------------------------------------------------------------------------ From: moultaka@ph1.uni-koeln.de To: gcnews@aoc.nrao.edu Subject: paper submission %astro-ph/0507161 \documentclass[referee]{../aa} %\documentclass{../aa} \usepackage{graphics,natbib,amssymb} \usepackage{rotating} \citestyle{aa} %\newcommand{\bm}[1]{\mbox{\boldmath $#1$}} %\newcommand{\bM}[1]{\mbox{\textbf{\textsf{#1}}}} \newcommand{\solm}{M$_{\odot}$\ } \newcommand{\solar}{L$_{\odot}$\ } \newcommand{\solars}{L$_{\odot}$\ } %\newcommand{\etal}{et al.\ } \newcommand{\rf}{\par\noindent\hangindent 15pt {}} %================================================================= \begin{document} \authorrunning{Moultaka et al.} \titlerunning{Mapping the ISM and CSM of the GC IRS~3-IRS~13 region} \title{VLT L-band mapping of the Galactic Center IRS~3-IRS~13 region} \subtitle{Evidence for new Wolf-Rayet type stars} \author{J. Moultaka$^1$, A. Eckart$^1$, R. Sch\"{o}del$^1$, T. Viehmann$^1$, \& F. Najarro$^2$} \institute{ 1) I Physikalishes Institut, Z\"ulpicher Str. 77, 50937 K\"oln, Germany \\ 2) Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, CSIC, Serrano 121, E-28006, Madrid, Spain \\ \email{email: moultaka@ph1.uni-koeln.de} } %\institute{ \date{Received / Accepted } \abstract{This paper presents L-band ISAAC and NAOS/CONICA (VLT) spectroscopic observations of the IRS~3-IRS~13 Galactic Center region. The ISAAC data allowed us to build the first spectroscopic data cube of the region in the L-band domain. Using the L-band spectrum of the extinction along the line of sight towards the GC derived in a previous paper (Moultaka et al. 2004), it was also possible to correct the cube for the foreground extinction. Maps of the water ice and hydrocarbon absorption line strength were then derived. These maps are important diagnostics of the interstellar and circumstellar medium because water ices are observed in molecular clouds while %are most likely associated with regions of star formation and disks surrounding young stars; on the other hand, hydrocarbons are usually good tracers of the diffuse ISM. These maps support our previous results that the absorption features most probably occur in the local Galactic center medium and can be associated with the individual sources. Moreover, turbulence seems to affect the studied region of the minispiral, which appears like a mixture of a dense and diffuse medium. Comparison of the concentrations of ice and hydrocarbon absorptions around IRS~13E, IRS~6E, and IRS~2, with similar concentrations at the location of the extended continuum emission around IRS~3, suggests that these sources might present outflows interacting with the surrounding ISM. It was also possible to derive Br${\alpha}$ and Pf${\gamma}$ emission line maps. The results suggest that the physical conditions of the ISM are not uniform in the observed region of the minispiral especially at the edges of the minicavity. The emission line maps allowed us to find three sources with broad lines corresponding to an FWHM deconvolved line width of about 1100 km/s and moving towards us with a radial velocity of about -300km/s. These sources are most probably new Wolf-Rayet type stars located in projection to the north and west of IRS~3. Their derived radial velocities and proper motions show that only two of them might belong to the two rotating disks of young stars reported by Genzel et al. (2003) and Levin \& Beloborodov (2003). Previously, NAOS/CONICA (NACO) data allowed us to resolve the IRS13E3 region into two components E3N, and E3c (Eckart et al. 2004). The new spectroscopic NACO data show that E3c is a good candidate for a Wolf-Rayet type star. In addition, three sources ($\eta$, $\zeta$, and $\gamma$) out of the eight very red sources located in the IRS13N complex also presented in Eckart et al. (2004) have been resolved spectroscopically with NACO. The spectra presented in this paper show that the red colors of the sources are probably due to extended dust emission. \keywords{Galaxy: center - galaxies: nuclei - infrared: ISM extinction} } \maketitle %=================================================================== \section{Introduction}\label{sec:intro} The vicinity of the center of our Galaxy (at a distance of $\sim 8$kpc) makes it the ideal nuclear region to study in detail. Recently, it has been shown that the central star cluster of the Milky Way is hosting a super massive black hole (SMBH) of $\sim$3.6 10$^6$ M$_\odot$ (Sch\"odel et al. 2002, Ghez et al. 2003) coinciding with the radio source Sgr A$^\star$. It is thus the best example where the environment of a central SMBH can be analyzed thoroughly. The central parsec is powered by a cluster of young and massive stars, the most prominent group of which is the IRS~16 complex (Blum et al. 1988, Krabbe et al. 1995, Genzel et al. 1996, Eckart et al. 1999, Cl\'enet et al. 2001) where helium emission lines have been observed in their NIR spectra. More recently, Paumard et al. (2001, 2004) have identified about 20 stars with strong He emission lines imploying integral field NIR spectroscopy. They classified them into two groups using a combination of their emission line widths and their K-magnitudes as a criterion. The intriguing result is the spatial distribution of these two groups, since the narrow line stars (FWHM$\sim 225$km s$^{-1}$) are mostly found in the IRS~16 complex (diameter of about 0.15 pc), whereas the broad line stars (FWHM$\sim 1025$km s$^{-1}$) are distributed over the whole field (diameter of about 1 pc). About 20 additional early-type stars in the inner region have also been reported by Horrobin et al. (2004), Paumard et al. (2004). The presence and especially the formation of a large number of young massive stars in the vicinity of the SMBH is problematic given the tidal field of Sgr A$^\star$ and other constraints (see discussion in Genzel et al. 2003). Levin \& Beloborodov (2003) and Genzel et al. (2003) show that the early-type stars appear to be located in one or two coeval counterrotating (with respect to each other) disks at large inclination angles. The presence of such disks would then give new insights into the presence of young stars in the vicinity of the SMBH (Genzel et al. 2003, Levin \& Beloborodov, 2003). \\ %located in the central $10\arcsec$. %These disks would have been formed from the disruption of infalling molecular clouds surrounding Sgr A$^\star$. The presence of such young stars in the vicinity of the SMBH is then explained by the collapse of the disks fragments when these become unstable.\\ %Levin \& Beloborodov (2003) have shown that 10 of the 13 stars for which 3-D velocities had been measured by Genzel et al. (2000) were located in a thin disk with a maximum opening angle of 10$\deg$. This disk would have been formed by the disruption of an infalling molecular cloud surrounding Sgr A$^\star$. They explain the presence of such young stars at 0.1 pc from Sgr A$^\star$ as the result of the collapse of disk fragments when the disk becomes unstable. Old stars can also be trapped by the dense accretion disk and become more massive after accreting the disk material, consequently, they look like young stars.\\ %On the other hand, Genzel et al. (2003) show that the early-type stars are located in two counterrotating (with respect to each other) disks at large inclination angles located in the central $10\arcsec$. As their stellar content is similar, they have most probably been formed coevally. The authors provide a scenario for the formation of these early-type stars: the collision of two infalling clouds creates the two disks of debris orbiting the central black hole; as a consequence of a contraction and a loss of the angular momentum, the gas can be moved inwards and the disks become gravitationally unstable leading to the formation of stars.\\ In addition to these massive early-type supergiants, a population of late-type stars are identified as AGB stars (e.g. Krabbe et al. 1995, Horrobin et al. 2004). A number of embedded objects associated with dust emission are also observed in the Galactic Center stellar cluster. Examples of such objects are IRS~1, IRS~3, and also the IRS~5, 8, 10W, and IRS~21 sources. These are identified as bowshock sources (Tanner et al. 2002, 2004, Rigaut et al. 2003) and are probably early-type Wolf-Rayet (WR) stars (Tanner et al. 2004) heating the dust of their environment while moving through it. \\ Recently, the IRS~13E complex has been resolved into 6 components (Maillard et al. 2004) and the IRS~13N region, located $\sim 0.5\arcsec$ north to the center of this complex, into eight sources (Eckart et al. 2004). The latter have strongly reddened NIR colors. These authors interpret this in the framework of low luminosity bowshock sources or young stellar objects (YSO). \\ %In the latter case, an even younger population of stars as previously reported would be identified in the vicinity of the SMBH even more stressing the question of how star formation would occur in the region.\\ %provide three possibilities as for the nature of these sources. One of the most exciting interpretations is that they could be young stellar objects (YSO) and Herbig Ae/Be stars. In this case, an even younger population of stars as previously reported would be identified in the vicinity of the SMBH reviving the question of how star formation would occur in the region.\\ %The first possibility is that they could be bright young stars heating the gas and dust in which they are deeply embedded or behind which they are located; the second one is that they could be low luminosity analogues of the bowshock sources as IRS~21 and IRS~8. Finally, the most exciting possibility is that they could be young stellar objects (YSO) and Herbig Ae/Be stars. In the latter case, an even younger population of stars as previously reported would be identified in the vicinity of the SMBH reviving the question of how would star formation occur in the region.\\ As for the interstellar medium in the central 1-2 pc region of our Galaxy, referred to as the central minispiral or the SgrA West HII region (in the following we refer to it as the minispiral) and surrounded by a torus of molecular gas called the circumnuclear ring (CNR or CND), it is shown to be composed in part of ionized gas in a low density (diffuse) medium (Lebofsky 1979, Lacy et al. 91, Paumard et al. 2004) and in part of dense molecular clouds where dust can survive (Lutz et al. 1996, de Graauw et al. 1996, Gerakines et al. 1999). Both components are responsible for the high extinction seen towards the region, reaching $\sim 27$mag in the optical (Rieke et al. 1989, Chan et al. 1997, Scoville et al. 2003, Viehmann et al. 2005). On the other hand, the extinction across the central 10$\arcsec$ to 20$\arcsec$ is shown to be smoothly distributed (Scoville et al. 2003).\\ In addition, {\it intrinsic} extinction and reddening associated with individual stars are thought to occur as well in the central parsec (Blum et al. 1996, Cl\'enet et al. 2001, Moultaka et al. 2004). Moreover, ISO observations have shown deep absorption features in the MIR (Lutz et al. 1996) in the direction of the Galactic Center. These are due to H$_2$O and CO$_2$ ices or aliphatic and aromatic hydrocarbons and silicates.\\ Water ice absorption at $3.0\mu$m and aliphatic hydrocarbon absorptions around $3.4\mu$m and at $3.48\mu$m have also been observed in the spectra of the bright sources located in the central parsec of the Galaxy: Jones et al. 1983, Butchart et al. 1986, McFadzean et al. 1989, Sandford et al. 1991, Wada et al. 1991, Pendleton et al. 1994, Chiar et al. 2002, Mennella et al. 2003, Moultaka et al. 2004.\\ The hydrocarbon absorption features in the MIR are caused by their CH, CC, CH$_2$, or CH$_3$ stretching modes: Duley \& Williams 1984, Butchart et al. 1986, Sandford et al. 1991, Sellgren et al. 1995, Brooke et al. 1999, Chiar et al. 2000, Grishko \& Duley 2002. The features we are interested in are the 3.4$\mu$m (a double feature at $3.38\mu$m and $3.42\mu$m) and the $3.48\mu$m absorption, both coming from stretching vibrations of the CH$_2$ and CH$_3$ groups. They are observed in the diffuse ISM and thus constitute a characteristic signature of it.\\ The water ice feature is due to vibrations in the O-H bonds. It originates from mantles of water ice that are formed by condensation of the interstellar gas onto dust particles. \\ This feature is important as it is observed in molecular clouds and is often associated with regions of star formation (e.g. Ishii et al. 1998, Brooke et al. 1999). \\ %The observations of 16 stars in the constellation of Ophiuchus located in a region of star formation obscured by a dark molecular cloud has lead Beck \& Simon (?????2002) to conclude that water ices are more associated with the circumstellar material (e.g. disks) of young stars. \\ %Moreover, they are thought to be located in the outer regions of disks surrounding young stars and to be part of the material leading to the formation of comets and planetesimals. In this paper, we present L-band spectroscopic observations of the IRS~3-IRS~13 region obtained with the ISAAC and NACO instruments operating at the VLT telescopes. This allows us to obtain a detailed picture of the integrated dust distribution towards that region thanks to the first L-band data cube constructed for this goal. In the following section, we describe the observations and the data reduction. In Sect.~\ref{datacube}, we provide an analysis of the data cube constructed using the ISAAC observations and discuss the results. The adaptive optics data obtained with NACO are presented and discussed in Sect. \ref{naco}. Finally, a summary and conclusion are provided in the last section. % Near-infrared diffraction limited imaging over the past 10 years %(Eckart \& Genzel, 1996; Genzel et al., 1997; Ghez et al., 1998, 2000; %Eckart et al., 2002; Sch\"odel et al. 2002, 2003; Ghez et al., 2003) %has yielded convincing evidence for a 3-4$\times$10$^6$\solm black %hole at the center of the Milky Way. This finding is supported by the %discovery of a variable X-ray and NIR source at the position of SgrA* %(Baganoff et al., 2001; Genzel et al., 2003a). Most intriguingly, %near-infrared imaging and spectroscopic observations have provided %evidence for recent star formation in the central parsec of the Milky %Way, an environment previously thought hostile to star formation %because of the tidal field of the black hole, intense stellar winds, %and strong magnetic fields. %At a distance of 8~kpc (Eisenhauer et al. 2003), the Galactic Center is %surrounded by a circumnuclear ring of dense gas and dust showing %clumpy extinction (G\"usten et al. 1987). Inside this ring, there is a %central cavity of about 3~pc diameter that contains mainly ionized or %atomic gas. The visual extinction estimates towards prominent sources %within the central stellar cluster range between 20 and 50 magnitudes %with a median around 30 magnitudes (see Rieke, Rieke, \& Paul 1989, %Chan et al. 1997, Scoville et al. 2003). In addition Scoville et %al. (2003) showed that the extinction is smoothly distributed across %the central 10 to 20 arcseconds with no indication of concentrations %of extinction on scales of about 1$\arcsec$ to 2$\arcsec$. %The visual extinction by $\sim$30 magnitudes along the line of sight %toward the Galactic Center (GC) is mostly due to the diffuse %interstellar medium (ISM) (Lebofsky 1979) and in part to %dense molecular gas (Gerakines et al. 1999; de Graauw et al. 1996; %Lutz et al. 1996). The absorbing gas is cold (10~K) and the %abundances of important molecular species are similar to those in the solar %neighborhood (Moneti, Cernicharo, \& Pardo 2001a, Chiar et al. 2000). %In addition Blum et al. (1996) and Cl\'enet et al. (2001) concluded %that the colours of individual dusty sources within the central stellar %cluster contain a substantial contribution from intrinsic reddening. %The entire central parsec of our Galaxy is powered by %a cluster of young and massive stars (Blum et al. 1988, Krabbe et al. 1995, %Genzel et al. 1996, Eckart et al. 1999, Cl\'enet et al. 2001). %Within that cluster the 7 most luminous (L$>$10$^{5.75}$ \solar), %moderately hot (T$<$10$^{4.5}$~K) blue supergiants %contribute half of the ionizing luminosity of that region %(Najarro et al. 1997, Krabbe et al. 1995, Blum et al. 1995). %Such massive and hot stars were also found in dense clusters %within the Galactic bulge, i.e. the Arches cluster (Cotera et al. 1992, %see also Figer et al. 2002 and references therein) and the %Quintuplet cluster (e.g. Figer et al. 1997). %In addition to the massive blue supergiants, a population of dusty %sources associated with bright dust emission can be found in the %Galactic Center stellar cluster. After initial work by %Becklin \& Neugebauer (1968, 1969) the first individual mid-infrared %sources in the central stellar cluster (among them IRS 1, 3 and %others) were reported by Rieke \& Low (1973) and Becklin \& Neugebauer %(1975). Later, IRS 1 was resolved into multiple components by Storey %\& Allen (1983), Rieke et al. (1989), Simon et al. (1990), and Herbst %et al. (1993). Further high resolution imaging by Tollestrup et %al. (1989) resolved IRS~6 and IRS~12 into multiple components. %In this paper, we discuss MIR sources that are located well within the %central stellar cluster at projected distances from Sgr~A* of less %than 0.5~pc (Fig. \ref{slitpositions.eps}). Several sources like %IRS~1, 3, and 21 are dominated by dust emission and are strong at a %wavelength of 10$\mu$m, whereas the supergiant IRS 7 is brightest at %2.2$\mu$m. The nature of the dust-enshrouded sources is still %unknown. Among the best studied cases is IRS~21, which is %strongly polarized (17\% at 2$\mu$m ; Eckart et al. 1995, Ott et %al. 1999, Krabbe et al. 1995). Initially, Gezari et al. (1985) %suggested that IRS~21 is an externally heated, high-density dust %clump. Given the MIR excess and the featureless NIR spectra several %other classifications have been proposed, including an embedded %early-type star and a protostar (Blum et al. 1988, Krabbe et al. 1995, %Genzel et al. 1996, Cl\'enet et al. 2001). Tanner et al. (2002) %suggest that IRS~21 is an optically thick dust shell surrounding a %mass-losing source, such as a dusty recently formed WC9 Wolf-Rayet %star. Tanner et al. (2002, 2003) indicate that the extended dust %emission of most of the central sources is consistent with bow shocks %created by the motion of massive hot stars through the dust and gas of %the mini-spiral. %One way of investigating the nature of these bright NIR/MIR sources is %by imaging and spectroscopy in the 2 to 4$\mu$m wavelength range. %In addition to Hydrogen and Helium recombination lines, %this wavelength domain is dominated by strong absorption features %due to abundant molecules (NH$_3$, CH$_3$OH, H$_2$O, CO, CO$_2$ etc...), functional groups (like %NH$_2$, CH$_2$), and ices. %Here H$_2$O ice enriched with molecular material is of special importance. %Liquid, crystalline, amorphous water ice as well as %trapped water ice in SiO condensate (Wada et al. 1991) %give rise to a rich variety in shapes of a prominent feature %with its deepest absorption at 2.94-3.00 $\mu$m %(e.g. Wada et al. 1991). The variety in shapes of the water ice feature is dependent not only on temperature, but also on annealing history and on the ice composition etc... (Hagen et al. 1983, Tielens \& Hagen 1982, Tielens et al. 1983, Kitta \& Kratschmer 1983, Hudgins et al. 1993, Maldoni et al. 1998) %The emission of dust and the absorption features of ices are %important diagnostic tools for the investigation of %the interstellar medium and circumstellar %environments of individual sources. %Infrared sources towards the Galactic Center show a wealth of ice %absorption features (Butchart et al. 1986; Sandford et al. 1991) %indicative of a broad range of organic material mostly in the diffuse %interstellar medium. Aliphatic hydrocarbons are characterized by %their CH$_2$ (methylene) and CH$_3$ (methyl) stretching modes around %3.4$\mu$m (Sandford et al. 1991; Pendleton et al. 1994). Aromatic %hydrocarbons are detected via their CH and CC stretching modes at 3.28 %and 6.2$\mu$m. (Chiar et al. 2000, Pendleton et al. 1994). An %absorption feature at 3.25$\mu$m has been found towards dense %molecular clouds. It is attributed to aromatic hydrocarbon molecules %at low temperatures (Sellgren et al. 1995; Brooke et al. 1999). %Differences in the exact central wavelength and profile width of the %absorption near 3.3$\mu$m are mostly attributed to differences in %temperature and/or carrier of the absorbing molecules in these %regions. %In this paper we present 3 to 4$\mu$m imaging and spectroscopy %data combined with near-infrared 2.2$\mu$m spectroscopy of the %strongest mid-infrared sources in the central stellar cluster. In addition to the previously published L-band observations of IRS~1W, IRS~3 and IRS~7 we provide the first L-band spectra of 9 other MIR sources: IRS~9, IRS~13, IRS~13N, IRS~21, IRS~29 and IRS~16~C, CC, NE and SW. These %data on sources located in the central $0.5$~pc of the GC enable us to study %the properties of the local interstellar medium and of circumstellar %matter in this region. \section{Observations and data reduction}\label{sec:obs} L-band observations of the central $\sim$0.5 pc of the Galaxy were undertaken with the spectrograph ISAAC located at the ESO Very Large Telescope (VLT) unit telescope UT1 (Antu), at the Paranal observatory in Chile during July 2003. The complete set of observations with ISAAC required for our study could be obtained in a single night. The observations were performed with the long-wavelength (LWS3) and low resolution (LW) mode using the SL filter covering the wavelength range of 2.7$\mu$m - 4.2$\mu$m. The use of a 0.6$\arcsec$ slit width implied a spectral resolution $R=\lambda/\Delta \lambda=600$ in that wavelength domain. The optical seeing at this time ranged between 0.4$\arcsec$ and 1$\arcsec$. To compensate for the thermal background, separate chopped observations were carried out using chopper throws of $\sim$20$\arcsec$ along the slit of length 120$\arcsec$. \\ The slit was positioned at 9 different locations shown in Fig. \ref{slitpositionsII.eps}. Eight of them map the IRS~3-IRS~13 region. The goal of such a mapping was to build a data cube of the region. For calibration purposes, a single additional slit position passes through a late-type star, labeled ``CO-star'' (see Fig. \ref{slitpositionsII.eps}), since it has been used successfully for an L-band extinction correction as described in Moultaka et al. (2004).\\ %because it shows CO absorption bands in its K-band spectrum (see Moultaka et al. 2004). \\ The resulting array images were divided by flat-fields, corrected for cosmic rays, for sky lines, and for dispersion-related distortion. The wavelength calibration was performed using a Xenon-Argon lamp.\\ A chopped frame contains a positive trace image and a negative one. Two consecutive chopped frames present shifted image positions where the positive trace image of the first frame is at the same position as the negative one of the second frame. Such consecutive frames were then subtracted from each other to provide a single frame containing two negative trace images and a positive one with twice the intensity of the negative images. After extraction of the individual source spectra, they were corrected for wavelength dependent sensitivity, atmospheric transmission, and telluric lines using two standard stars HR 5249 (B2IV-V) and HR 7446 (B0.5III).\\ \begin{figure} \resizebox{8cm}{!}{\rotatebox{0}{\includegraphics{slitpositionsIIcut.eps}}} \caption[]{ISAAC L-band image of the central parsec of the Galaxy. The slit positions chosen for the ISAAC observations are shown in blue. The black line corresponds to the NACO slit position. The ``CO-star'' used to derive L-band spectrum of the extinction along the line of sight toward the GC lies in one of the ISAAC slit positions. } \label{slitpositionsII.eps} \end{figure} A second night was used to observe part of the region using one slit position (see Fig. \ref{slitpositionsII.eps}) with CONICA in spectroscopic mode behind the adaptive optics system NAOS mounted on the VLT unit telescope UT4 (Yepun). The slit was positioned such that the IRS~13E3 and 3 of the IRS~13N components lay inside the slit. During this night the optical seeing varied from 0.4$\arcsec$ to 0.9 $\arcsec$. The slit width used is of 86 mas implying a resolution of R=700 in the wavelength domain from $3.2\mu$m to $3.76\mu$m covered by the used L' filter. \\ For sky subtraction, the jitter technique was used consisting of taking different images with offsets between the positions. We subtracted the sky images from the object images. The resulting frames were flatfielded after a subtraction of the darks from the flatfields. They were corrected for cosmic rays, for sky lines, and for dispersion-related distortion. \\ As no calibration lamp was available for wavelength calibration, the prominent atmospheric line at $3.31\mu$m and the Pf${\gamma}$ emission line at $3.739\mu$m were used instead.\\ Finally, the images were corrected for telluric lines using the spectra of the standard G0 type star HD 4306.\\ All the data reduction was performed using routines from the IRAF and MIDAS software packages. \section{An L-band data cube of the IRS~3-IRS~13 region}\label{datacube} Eight of the ISAAC slit positions on the sky shown in Fig. \ref{slitpositionsII.eps} allowed us to build a 3D data cube of the IRS~3-IRS~13 region, i.e. position along the right ascension and declination, as well as wavelength. This was done using the DPUSER\footnote{http://www.mpe.mpg.de/$\sim$ott/dpuser/} software. To construct such a cube, each slit image is divided by the standard star shifted in wavelength and scaled in intensity for optimum sky line suppression. The shifting allows correction for small errors in the zeropoint of the dispersion and scaling for possible small variations in the airmass.\\ The relative flux calibration of the slits was done % in comparison to the others is made by determining the area (in pixels) covered by an object in all slits where the object is present; then, assuming that the mean value of the intensity multiplied by the area is equal to the total intensity of the object, the contribution of each slit to the flux of the object is normalised to unity and multiplied by the proportion of the real flux of the object relative to IRS~34. The values of the fluxes are obtained from using the L-band magnitudes published by Viehmann et al. (2005). The objects used for the relative flux density calibration of the slits are IRS~3, IRS~6E, IRS~12N, IRS~29, IRS~29N, and IRS~34.\\ Due to the pixel scale of the array and to the slit width used, %is 0.148" and the slit width is of 0.6$\arcsec$, the 3D-cube is constructed by laying close to each others 4 times each of the slit images corresponding to each of the 8 slit positions on the sky shown in Fig. \ref{slitpositionsII.eps}. The goal is to obtain a well-proportioned image while keeping the same observed resolution along the slit height. the step in declination and wavelength of the obtained cube is of 0.148$\arcsec$/pixel and of 0.6$\arcsec$/pixel in right ascension. For display purposes, the images were adjusted such that the image scale is the same in both directions. The positional calibration of the cube is done using the reference coordinates of IRS~3 taken from Viehmann et al. (2005). The final calibrated image was smoothed such that the final angular resolution is on the order of 0.8$\arcsec$. Integrated L-band maps are shown in Fig. \ref{cartesintegby4sm3p8IIOVI.eps}. %???The source showing up in the integrated image at the south-western side of IRS~29 is an artifact of the smoothing. \\ In this figure one can also distinguish the bright source IRS~3. Viehmann et al. (2005) notice an extended emission to the north-east and to the west of the compact center of this source. They interpret this feature as an extended dust shell of a hot mass-losing star, with bow-shock-like appearance produced by the interaction with the wind from the IRS~16 cluster or SgrA$^\star$. \\ %what about the east-side extension????.\\ \begin{figure} \resizebox{9cm}{!}{\rotatebox{-90}{\includegraphics{cartesintegby4_sm3p8IIOVIIV.eps}}} \caption[]{{\it (a)-} The integrated L-band map of the observed IRS~3-IRS~13 region (not corrected for the foreground extinction) obtained from the ISAAC data cube. {\it (b-)} A smoothed version of the integrated map with overlaid linear intensity contours. As shown, one can distinguish clearly the bright sources of the region, as well as the minispiral structure.{\it (c-)} A smoothed version of the integrated map corrected for the foreground extinction as explained in the text. Linear intensity contours are also overlaid for clarity, which helps to show the similarity between the two maps. They correspond to relative intensity levels, since absolute values are not necessary in the context of this paper. Two consecutive contours are separated by a factor of 1/48 of the peak intensity.} \label{cartesintegby4sm3p8IIOVI.eps} \end{figure} %{\bf They correspond to values in $10^4$ of 2.8, 14.1, 25.4, 36.7, 48, $\geq$ 59.3 and $\leq$ 556.9.} % with levels in $10^4$: 4, 21.8, 39.8, 57.6, 75.6 and $\geq$ 93.6, $\leq$ 882}. %140000,705402,1.2708e+06,1.83621e+06,2.40161e+06, $\geq$ 2.96701e+06 and $\leq$ 2.78447e+07. %200000,1.09551e+06,1.99103e+06,2.88654e+06,3.78206e+06 and $\geq$ 4.67757e+06, $\leq$ 4.40802e+07 The spectrum of the L-band absorption along the line of sight towards the Galactic Center can be derived by dividing the featureless spectrum of a late-type star located well outside the minispiral area with blackbody spectrum of effective temperature T$_{eff}$= 3600K as explained in Moultaka et al. (2004). We argued in that paper that the location of this star is at a projected distance of 12.6$\arcsec$ ($\sim0.5$pc) from the center, is at the edge of the brightest part of the SgrA West HII region, and that it does not show any excess emission in the L-band. For these reasons, it is assumed to be free of local reddening and its spectrum is then mostly, but not exclusively, affected by the line of sight extinction towards the Galactic Center. The spectrum of the L-band absorption is thus a good approximation of the real foreground extinction spectrum. As expected, the spectrum obtained from the present data is very similar to the one shown in Fig. 8 of the previous paper; therefore we use the same spectrum of the foreground L-band extinction. All the eight slit images are divided by this spectrum in order to construct the data cube shown in Fig.~\ref{cartesintegby4sm3p8IIOVI.eps}~c of the extinction corrected spectra. %The integrated L-band image of this data cube shown in Fig.~\ref{cartesintegby4sm3p8IIOVI.eps}c is very similar to the non corrected one of Fig.~\ref{cartesintegby4sm3p8IIOVI.eps}b, which supports the fact that the extinction. \subsection{Optical depth maps of the ice and hydrocarbon features}\label{optdepth} %???? Maybe introduce the different absorptions or maybe in the introduction?\\ As in Sandford et al. (1991), Chiar et al. (2002), and Moultaka et al. (2004), the spectral regions around $2.8\mu$m and $3.77\mu$m are assumed to be representative of the continuum emission at these wavelengths in the L-band.\\ \begin{figure} \resizebox{8cm}{!}{\rotatebox{0}{\includegraphics{IRS29cont.eps}}} \caption[]{L-band spectrum of IRS~29 where water ice and hydrocarbon absorptions are shown as approximated in the data cube. The approximated continua consist of straight lines from $\sim2.84\mu$m to $\sim3.77\mu$m for the H$_2$O absorption and from $\sim3.32\mu$m to $\sim3.77\mu$m in the case of the hydrocarbon feature.} \label{IRS7cont.eps} \end{figure} In order to derive the optical depth maps of the water ice and the hydrocarbon absorptions from each of the data cubes described above, it is necessary to define the continua over each of the absorption features. We approximated the continuum over the hydrocarbon absorption feature by the straight line connecting the spectrum at $\sim3.32\mu$m and $\sim3.77\mu$m; the one over the water ice absorption was approximated by a straight line connecting the spectrum at $\sim$2.84$\mu$m and $\sim3.77\mu$m (see Fig. \ref{IRS7cont.eps}). These continuum positions are good approximations as one can see by comparing such continua with the fitted ones in Moultaka et al. (2004). The water ice absorption is then approximated in the 2.8$\mu$m to 3.32$\mu$m spectral region by the area between the spectrum and the continuum over the ice feature. In the 3.32$\mu$m to 3.77$\mu$m wavelength domain, the water ice absorption is approximated by the area between the continuum over the hydrocarbon feature and the one over the water ice feature (Chiar et al. 2002) (see Fig. \ref{IRS7cont.eps}). %Using the previous continua, we have derived optical depth maps of the two integrated absorptions (i.e. along the wavelength range of each of the absorption) using the following definition of the optical depth: %\begin{equation} %tau=-ln(\frac{\int{F_{obs}}}{\int{F_{cont}}}) %\end{equation} %where $\int{F_{obs}}$ and $\int{F_{cont}}$ are the observed fluxes and the extimated continuum fluxes integrated over the absorption feature.\\ Maps of the optial depths at $3.0\mu$m, $3.4\mu$m and $3.48\mu$m are also derived using the values of the continua at these wavelengths. The maps are obtained using the definition of the optical depth at a given wavelength $\lambda$ by: \begin{equation} \tau_{\lambda}=$-ln$(\frac{F_{obs\,\lambda}}{F_{cont\,\lambda}}) \end{equation} where $F_{obs\,\lambda}$ and $F_{cont\,\lambda}$ are the observed and the estimated continuum fluxes at the given wavelength $\lambda$, respectively. The values of the fluxes at a given wavelength are determined by taking the mean value over 60 pixels ($\sim 85.8$nm) around $\sim2.84\mu$m, 10 pixels ($\sim 14.3$nm) around $\sim3.32\mu$m and $\sim3.77\mu$m, and over 40 pixels ($\sim 57.2$nm) around $3.0\mu$m, $3.4\mu$m, and $3.48\mu$m. When deriving the optical depth values over the IRS~3-IRS~13 region, some conditions were imposed to avoid artifacts of the division procedure and %When $F_{obs}$ or $F_{cont}$ are negative, the value of the optical depth $\tau$ is set to zero. On the other hand, to avoid artifacts in regions of low flux densities. Thus, the optical depth value is set to zero if the signal is less than 3$\sigma$ of the sky background noise in the data.\\ %when the mean intensity of the blue part of the spectrum is less than 3$\sigma$ of the noise (because the mean intensity of the red part is always higher than that of the blue part). Since the resulting observed and extinction corrected maps are very similar, we show only the extinction corrected ones in Fig.~\ref{carteby4p8IIOVIIVExtCorr.eps}. In this figure are shown the integrated L-band map of the IRS~3-IRS~13 region (Fig.~\ref{carteby4p8IIOVIIVExtCorr.eps}~a) and the optical depth integrated maps over the ice feature from $2.84\mu$m to $3.77\mu$m (Fig.~\ref{carteby4p8IIOVIIVExtCorr.eps}~b) and over the hydrocarbon feature from $3.32\mu$m to $3.77\mu$m (in Fig.~\ref{carteby4p8IIOVIIVExtCorr.eps}~c). The maps obtained after deriving the optical depth values at the wavelengths of $3.0\mu$m, $3.4\mu$m, and $3.48\mu$m are shown in (d), (e), (f) of the figure. The striking first result, as reported previously, is that the non-corrected maps and their extinction-corrected homologues are very similar. This shows that the absorption features probably take place in the local Galactic centre medium and that, when they are present at the location of a bright source, they can be associated with the source. This result supports our previous finding concerning the absorption features observed in the direction of the bright sources of the central half parsec (Moultaka et al. 2004).\\ Moreover, the maps of the integrated ice absorption feature (maps b) and of the absorption at 3.0$\mu$m (maps d) are very similar, and those of the integrated hydrocarbon feature (maps c), the 3.4$\mu$m (maps e) and the 3.48$\mu$m (maps f) are similar as well. This shows that the values of the optical depths obtained at the single wavelengths are very representative of the shape of the absorption features over the whole absorption band.\\ All the previous results also show that our continuum derivation is reliable. Comparison of the ice (b and d) and hydrocarbon (c, e and f) optical depth maps show for the first time that the two features are similarly distributed in the region and are prominent in the studied minispiral area. Indeed, the peaks and minima in both absorptions are located at the same positions on the different maps. A vague correlation between the optical depth values of the two absorption features observed towards the bright sources of the central half parsec was found in our previous paper Moultaka et al. (2004) (see Fig. 19 of that paper). This correlation shows up as well in the present data and in the studied region. In Fig.~\ref{diagramTauicehydmap.eps}, the optical depth values of the two absorption features are plotted at different pixels of the maps where the signal to noise ratio is higher than 10, implying small errors in the optical depth measurements. These pixels include the bright sources of the region and a large part (the central part) of the observed minispiral area. The correlation coefficient obtained without considering the uncertainties is 0.36, which is in agreement with the previous value of 0.43 where the error bars were taken into account (Moultaka et al. 2004). This correlation suggests that the ISM presents itself as a mixture (possibly clumpy as indicated by the maps) between a dense dusty and a diffuse ionised media. In addition, the turbulent nature of the ISM (Paumard et al. 2004) may also be of importance. \begin{figure} \resizebox{8cm}{!}{\rotatebox{0}{\includegraphics{diagramTauicehydmap.eps}}} \caption[]{Optical depth of the hydrocarbon versus the ice absorption features. This figure plots the intensities of all pixels of the water ice and hydrocarbon optical depth maps, at which the S/N ratio in the integrated L-band map, is higher than 10.} %for a number of about 300 pixels where the signal is high enough to assume little uncertainties on the optical depth measurements.}} \label{diagramTauicehydmap.eps} \end{figure} %However, the IRS 13 region shows a complete anticorrelation between the two features where the hydrocarbon absorption peaks and the water ice absorption presents a minimum. This suggests that the diffuse medium is more prominent in the region. The northern part of IRS13, where the presence of very red sources has been reported by Eckart et al. (2004), shows higher water ice and hydrocarbon absorptions than the centre of the IRS~13 complex. This is in agreement with these sources being more embedded than those at the centre of the IRS~13 complex. %, while the water ice absorption is almost equivalent.\\ %A high value of the optical depth of the ice feature shows up at the location of IRS~12.\\ On the other hand, in the optical depth maps one can notice a peak in the ice absorption feature at the north-eastern and the western sides of IRS~3. These peaks possess homologues in the hydrocarbon absorption feature maps. In addition, the position of IRS~3 shows a deficiency in the H$_2$O absorption, which suggests that the ISM has been swept up by the stellar wind at this position. The peaks can be interpreted as being the trace of the circumstellar medium at the edge of the extended dust shells of this star. This also suggests that the west-side bowshock-like extended emission which shows up in the integrated L-band map (Fig.~\ref{cartesintegby4sm3p8IIOVI.eps}) is real and can be created by the mass-losing star during its interaction with the surrounding medium.\\ A similar situation occurs north and south of IRS~13 and IRS~6E and north-west and south-east to IRS~2, where peaks in the ice and hydrocarbon absorptions show up; moreover, the absorption maps also present a deficiency at the location of IRS~13, IRS~6E, and IRS~2 as is the case for IRS~3. This is an intriguing result, which suggests that these sources could also be mass-losing stars interacting with their environment and presenting an outflow-like shape. Moreover, these results indicate a close spatial correlation between these sources, especially IRS~13, and the surrounding material of the minispiral. Finally, both IRS~34 and IRS~29 locations show high water ice and hydrocarbon absorption peaks that can be associated with these sources. %All the previous descriptions are also valid in the maps corrected for extinction along the line of site shown in Fig. \ref{carteby4p8IIOVIIVExtCorr.eps} and obtained as described in Sect. \ref{???}. This shows that our continuum derivation is reliable. %However, the IRS~13 region and its east side show a big gap in the H$_2$O absorption feature extinction corrected maps. This probably due to an artifact of the foreground extinction which is likely to be overestimated in that region. %On the other hand, we obtain similar maps when deriving the optical depth values at the exact wavelengths at $3.0\mu$m, $3.4\mu$m and $3.48\mu$m as shown in the maps (d), (e), (f) of Fig. \ref{carteby4p8IIOVIIV.eps} and Fig. \ref{carteby4p8IIOVIIVExtCorr.eps} where the spectra have been corrected for extinction along the line of sight; this shows that the values of the optical depths obtained at the single wavelengths are very representative of the whole abosrption features.\\ %The previous results imply that the absorption features probably take place in the local medium and that when they are present at the location of a bright source, they can be associated with the source. \\ %Moreover, the present maps show that the water ice and the hydrocarbon features are well correlated and prominent in the minispiral area. %they do not seem to be associated with star formation regions as they are also found in the vicinity of late-type stars as IRS~29. \subsection{Hydrogen emission line maps}\label{emlines} %????Intriduce the lines and figure?????\\ The maps of the Pf${\gamma}$ and Br${\alpha}$ emission lines are constructed by deriving the relative flux density integrated over each line: from $3.722\mu$m to $3.744\mu$m for Pf${\gamma}$ and from $4.028\mu$m to $4.061\mu$m for Br${\alpha}$. The continuum is taken as the average of the continuum on the red and the blue sides of the line taken over 16 pixels ($\sim 22.8$nm) for Pf${\gamma}$ and 24 pixels ($\sim 34.3$nm) for Br${\alpha}$ on each side. %Just as they are defined, the emission line maps also include the HeII recombination lines at 3.738$\mu$m and 4.049$\mu$m when these lines are present in the spectra. Such a case occurs and will be discussed in the following section.\\ Since we compute the relative fluxes (i.e. $\frac{F_{line}-F_{cont}}{F_{cont}}$), and in order to avoid artifacts in the maps (see Sect. \ref{optdepth} above), we impose similar conditions to the ones used for the optical depths of the water ice and hydrocarbon features. %figure emission The Pf${\gamma}$ and Br${\alpha}$ emission line maps are shown in Fig. \ref{carteby4p8IIOVIIVExtCorr.eps} (g) and (h) where the spectra have been corrected for the foreground extinction. These maps are similar to those not corrected for the line of sight extinction, as one could expect because the wavelength region of the emission lines in the spectra is not heavily affected by extinction. The maps of the two emission lines trace the minispiral well and are very similar in that area. They show high line strengths in the south-eastern part, which can be explained probably by the high density of this region being located just at the south-western edge of the minicavity and possibly associated with the late-type star IRS~12N (Genzel et al. 2000). % This result suggests that over the whole area, the physical conditions of the minispiral are quite uniform. This idea is, however, not fully supported by the map of Fig. \ref{carteby4p8IIOVIIV.eps} (i) (and of Fig. \ref{carteby4p8IIOVIIVExtCorr.eps} (i) for the extinction corrected version) In Fig.~\ref{carteby4p8IIOVIIVExtCorr.eps}~(i), we show the map of the Br${\alpha}$ to Pf${\gamma}$ ratio. This map does not show a constant ratio over the minispiral region; the line ratio varies from 0.12 to 1.75 and shows peaks in the south-western part associated with the south-western edge of the minicavity. Peaks of the ratio show up as well in the region located to the north-west of the minicavity with values of about 1.8 and at the location of the IRS~2 and IRS~13 complex regions with values of 1.6 and 1.4, respectively. The IR color-temperature map of the minispiral obtained by Cotera et al. (1999) shows peaks of the dust temperature at the locations of IRS~13 and IRS~2 corresponding to values of about 220K. As shown by Hummer \& Storey (1987) for temperatures $\geq$ 1000 K, the Br$\alpha$/Pf$\gamma$ ratio can be equal in media of high temperature and low density and vice versa. Our Br$\alpha$/Pf$\gamma$ ratio maps are in agreement with the finding of Cotera et al. (1999) if the density at the locations of IRS~13 and IRS~2 is lower than in the neighbouring regions. The peaks of the line ratio at the south- and north-western sides of the minicavity can then be explained by lower temperatures and higher densities justified by their location at the edges of the minicavity and possibly associated with IRS~12N and IRS~29. \\ %Moreover, IRS~3 and the source north to IRS~3 also visible in the integrated maps (Figs. \ref{carteby4p8IIOVIIV.eps} and \ref{carteby4p8IIOVIIVExtCorr.eps} a) but faint in the emission line maps show up in the line ratio maps. %. However the south-eastern part shows a peak in the ratio implying that this region has probably different conditions of temperature and density. This is in agreement with the complex composition of the minispiral found by different authors (?????) (2 new sources show up in the ratio figures and WR3 disappears, they have to be checked?????) .\\ \subsubsection{New WR-type stars in the Galactic center} Analysis of our emission line maps reveals three Wolf-Rayet stars, two of which have been detected for the first time. Indeed, in the northern part of the emission line maps, three sources of high emission show up, but are very faint in the integrated L-band map. They are located at the northern and the western sides of IRS~3 and correspond to three faint sources that can be distinguished in the continuum images of Fig. \ref{WRpositions.eps} (red circles labeled WR1, WR2, and WR3). Their emission lines are much broader than those of the minispiral area, which have typical FWHM of 200 km/s resulting, when unresolved, from multiple individual velocity gas components which characterize the gas and have line widths of about 50 km/s (Paumard et al. 2001, 2004). The L-band spectra are shown in Figs. \ref{WR1FRVN11ExtCorr.eps}, \ref{WR2sumFRIIN7ExtCorr.eps}, and \ref{WR3sumFRIN8.eps}. \begin{figure} \resizebox{6cm}{!}{\rotatebox{0}{\includegraphics{WRpositions.eps}}} \caption[]{L-band ISAAC image of the IRS~7-IRS~3 region with the positions of the three WR-type stars WR1, WR2, and WR3, where WR1 is the IRS~7W source identified by Ott (2004) and Paumard et al. (2001,2004).} \label{WRpositions.eps} \end{figure} %The spectra are corrected for the foreground extinction in the case of WR1 and WR2 and not corrected in the case of WR3 where the correction seems to be overestimated at this northern location. This shows once more that the extinction along the line of sight is not completely smooth all over the area.\\ In these figures, one can distinguish several broad emission lines. All of them are intriguingly blueshifted by about -300 $\pm$ 100 km/s. Because of the broad width of the lines (the FWHM corresponds to a velocity of about 1100 km/s) and the low spectral resolution, no better precision on the radial velocities can be provided. %appear in the spectra (see previous figures). %The FWHM of these lines correspond to a velocity of about 1100 km/s????. Moreover, the emission lines are also blueshifted implying that the sources are moving towards us with a radial velocity of about -300 km/s. Taking the blue shift into account, the new emission lines correspond to HeI, HeII, and H/HeI,HeII lines as labeled in their spectra. If we consider the strong line at 3.09$\mu$m as a Pf$\delta$ line, it would disagree with the position of the other lines and would imply a higher blueshift of these objects, which is unlikely. This line is also very prominent in the spectrum of WR1 located west of IRS~3, which is a HeI emission line star already identified by Najarro et al. (1997), Ott (2004), and Paumard et al. (2001,2004), and called IRS~7W. If the 3.09$\mu$m line were due to CIII or CIV lines, then very strong CIII and CIV lines would also be expected to show up in the K-band spectrum of this star, which is not the case (see Najarro et al. 1997 and Ott 2004). Consequently, at this wavelength, only a HeII (6-7) line would fit. \\ On the other hand, the strong similarity between the spectra of WR1 and WR147 shown in Morris et al. (2000) and classified as a WN8 star, points towards a slightly lower excitation of WR1, which could prevent the HeII line at 2.189$\mu$m (fairly weak in Morris et al. 2000) from appearing in emission, while a strong HeII emission line at 3.09$\mu$m can still be observed. Using a radiative transfer model, Najarro et al. (1997) indeed show that HeII emission lines can be expected in the spectrum of WR1. \\ Moreover, the K-band spectrum of WR1 shows a highly depleted hydrogen (Najarro et al. 1997). Consequently, we can conclude that the hydrogen lines {in the present L-band spectra} are also contaminated by HeI and HeII or are pure HeI neighbouring emission lines that cannot be separated at the present spectral resolution. Indeed, for higher transitions than the Bracket ones, the HeI atoms are very hydrogenic. Najarro et al. (1997) also find a radial velocity of -250 km/s in agreement with our value and with the value obtained by Ott (2004).\\ The extinction-corrected spectra (in the case of WR1 and WR2) are fitted by a blackbody spectrum with T$_{eff}\geq 30000$ K. Since these temperatures and the present wavelength domain correspond to the Rayleigh-Jeans regime, the temperature of the best-fitted blackbody spectrum will be taken as a lower limit. A residual absorption in the blue part of the WR2 extinction corrected spectrum shows up. This is probably due to an excess of the extinction towards this position. The spectrum of WR3 shown in Fig. \ref{WR3sumFRIN8.eps} is not corrected for the foreground extinction, because the corrected spectrum is very blue. This is most probably due to a lower extinction toward this northern location. Indeed, the NIR colors of this object listed in Table \ref{WRtab} and obtained from ISAAC (for the L- and M-bands) and NACO (for the H- and K-bands) images, as described in Viehmann et al. (2005), show that it is bluer than the others. In addition, the K-band magnitudes of the 3 stars are similar to those of the broad emission line stars observed by Paumard et al. (2001,2004).\\ Considering all these results, we conclude that these sources are most likely WR-type stars with strong stellar winds and probably high mass loss rate. As the L-band spectra of WR2 and WR3 are very similar to that of the early-type star WR1, this supports our conclusion. Furthermore, the similarity of the spectrum of WR1 with the one of the WN8 star WR147 of Morris et al. (2000) shows that this star seems to be consistent with a WN8/9 spectral type, although one can not rule out that it is on its way from a WN8/9 to a WC9/10 spectral type.\\ Using the K-band NACO images obtained from four epochs of NACO observations between May 2002 and July 2004 (Sch\"odel et al. in preparation), we derived the proper motions of the three WR stars (see Table \ref{WRtab2}). This table also lists the measured radial velocities, the angle between the normal to the disk, and the velocity vector of a given star, the maximal radial velocities which allow these stars to be bound to the SMBH assuming that they belong to one of the disks. Note that if the radial velocities of the stars are higher than the maximal radial velocities, this would not imply that they are not bound to the central stellar cluster. The velocities of the WR1 and WR2 stars fit well, within the uncertainties, the counterrotating disks of young stars determined by Genzel et al. (2003) and Levin \& Beloborodov (2003); where WR1 belongs to the clockwise rotating disk and WR2 to the counter-clockwise disk. However, WR3 seems not to belong to the counter-rotating disk even though it is moving counter clockwise, but it still may, given the uncertainties on its radial velocity. %As a matter of fact, it's velocity seems to be higher than the escape velocity at its position from the SMBH. %Even if we supposing that the inner clockwise disk is more extended than previously determined, WR3 could also belong to this disk ????. More accurate radial velocities measurements are necessary to confirm our results. \begin{table*}[htbp] \small \begin{center} \begin{tabular}{rccccccc} \hline Source & H & K & L & M & H-K & K-L & L-M \\ \hline WR1 & 14.25 $\pm$ 0.25 & 11.73 $\pm$ 0.25 & 10.08$\pm$ 0.15 & 9.37$\pm$ 0.15 & 2.52 $\pm$ 0.5& 1.65 $\pm$ 0.4& 0.72$\pm$ 0.3 \\ WR2 & 15.24$\pm$ 0.25 & 12.90$\pm$ 0.25 & 11.31$\pm$ 0.15 & 10.02$\pm$ 0.15 & 2.34 $\pm$ 0.5& 1.58$\pm$ 0.4 & 1.29$\pm$ 0.3 \\ WR3 & 13.43$\pm$ 0.25 & 11.64 $\pm$ 0.25 & 9.84$\pm$ 0.15 & 9.22$\pm$ 0.15 & 1.79 $\pm$ 0.5& 1.80$\pm$ 0.4 & 0.61$\pm$ 0.3 \\ \hline \end{tabular} \end{center} \caption{Magnitudes and colors of the three newly-found Wolf-Rayet stars. } \label{WRtab} \end{table*} \begin{table*}[htbp] \small \begin{center} \begin{tabular}{rccccc} \hline Source & $\mu_\alpha$ (km/s)& $\mu_\delta$ (km/s) & $v_r$ & $v_{r\,max}$ & $\theta$ (degrees)\\ \hline WR1 & -61$\pm$24 & -127$\pm$61 & 260$\pm$100 & 296$\pm$49& 85$\pm$11\\ WR2 & 135$\pm$32 & 41$\pm$47 & 310$\pm$100 & 322$\pm$35 & $ 115\pm$14\\ WR3 & -129$\pm$39 & -4$\pm$53 & 332$\pm$105 & 174$\pm$44 & 74$\pm$12\\ \hline \end{tabular} \end{center} \caption{Proper motions, radial velocities, orbital inclinations ($\theta$) to the normal to the disks of the newly-found Wolf-Rayet stars and maximal line-of-sight velocities allowed for the stars to still be bound to the SMBH under the assumption that they are part of one of the disks.} \label{WRtab2} \end{table*} \begin{figure} \resizebox{8cm}{!}{\rotatebox{0}{\includegraphics{WR1FRVN11ExtCorr.eps}}} \caption[]{L-band spectrum corrected for the line of sight extinction of the Wolf-Rayet type star WR1. The broad Helium emission lines are also shown. The shape of this spectrum agrees well with a blackbody temperature $\geq$ 30000K. } \label{WR1FRVN11ExtCorr.eps} \end{figure} \begin{figure} \resizebox{8cm}{!}{\rotatebox{0}{\includegraphics{WR2sumFRIIN7ExtCorr.eps}}} \caption[]{Extinction-corrected L-band spectrum of the Wolf-Rayet type star WR2 where Helium emission lines are distinguished. A blackbody spectrum with effective temperature of 30000K is also shown. The shape of the spectrum can be well-fitted with this continuum except in the blue part where the excess of absorption is probably due to an underestimation of the extinction towards this position. } \label{WR2sumFRIIN7ExtCorr.eps} \end{figure} \begin{figure} \resizebox{8cm}{!}{\rotatebox{0}{\includegraphics{WR3sumFRIN8.eps}}} \caption[]{Observed L-band spectrum (not corrected for the foreground extinction) of the Wolf-Rayet type star WR3 where helium emission lines are distinguished. It is well-fitted by the spectrum of a blackbody of temperature $\geq$30000K. The correction for the extinction along the line of sight, as derived in our previous paper Moultaka et al. (2004), seems to overestimate the real extinction towards the position of this object.} \label{WR3sumFRIN8.eps} \end{figure} % at $3.0\mu$m and the hydrocarbon double feature at $3.4\mu$m. \\ %The optical depth map of the ice and hydrocarbon features obtained with the higher continuum are more adapted to the study of IRS~13 and IRS~29 but the maps obtained with a lower continuum represent better the optical depth value of IRS~3 as one can see it in Figs. 2 and 3 of Moultaka et al. (2004). %The striking result that one can derive from these maps is the similarity between the ice feature map and the 3.4$\mu$m map. This is in agreement with the trend of correlation observed in Moultaka et al. (2004) between these two features for the twelve most luminous source of the central parsec of the Milky-Way. %The high optical depth value in the minispiral area on the west-side of IRS~13 is not due to ice absorption as can be seen in the extracted spectra of the region (see Fig. \ref{minispiralspec}), these values represent actually the difference of the slopes in the red part (from pixel 660 to 960 ???in lambda???) and the blue part (from pixel 60 to 360 in lambda????). Consequently, the value of the optical depth informs about the temperature of the dust in the minispiral (??? if we assme a black body, the temperature should be below 700K. Maybe make a table of the values of tau for different temperatures). In this case, if one traces the optical depth map using a lower continuum matching the value of the spectra at pixel 60 (???lambda), one can distinguish better the difference of temperature (see Fig. \ref{carteoptdepthby4sm3}). \section{Resolving the IRS13-IRS13N complex with the adaptive optics NACO system}\label{naco} In a previous paper (Eckart et al. 2004), H-, K$_s$-, and L-band diffraction-limited images of the Galactic Center have been obtained with the adaptive optics NAOS/CONICA camera. As shown in that paper, the IRS~13 complex has been resolved into 4 components (see Fig. 2 of that paper). In addition to the well known components E1 and E2 (Paumard et al. 2001, Maillard et al. 2004), the E3 component appears as a double structure in the K$_s$-band image. The components of this structure have been labeled E3N (for North) and E3c (for center). The E3c component is very red (K-L=4.24 and H-K=4.05) and is also the faintest among the four components in the H- and K-bands and the brightest in the L-band. In Maillard et al. (2004), the IRS~13E complex has been resolved into 6 components. The IRS~13~E4 component is the brightest in H and K after IRS~13E1 and E2. As the IRS~13~E3N of Eckart et al. (2004) has similar magnitudes, it corresponds most probably to the E4 component of Maillard et al. (2004). Moreover, the IRS~13~E3 component of Maillard et al. (2004) has been resolved into 2 components called E3A and E3B, and the position of these sources coincides with our E3c component. Using the results of the fit of SED fitting, the authors argue that both E3A and E3B are probably WR-type stars.\\ The present NACO spectrum of the E3 region (E3N + E3c) (Fig. \ref{fig3}) shows a prominent Pf$\gamma$/HeII emission line that is very faint in the IRS~13E2 component as shown in the figure. This supports the result that the E3 component is the broad He emission-line star identified in the IRS~13 region by Paumard et al. (2001) and previously by Krabbe et al. 1995 and Blum et al. (1996). As the E3c source is the faintest in the K-band with a K-magnitude fainter than 10.6 mag, we argue that this resolved component might be a WR-type star (see discussion in Paumard et al. 2001 and the introduction to the present paper), as was also suggested in the former paper by Eckart et al. (2004). This would be in agreement with the result of Maillard et al. (2004). \begin{figure*} %\scalebox{0.15}{ \resizebox{16cm}{!}{\rotatebox{0}{\includegraphics{moultakafig2.eps}}} \caption{{\it L'}-band NACO spectra of IRS~13~E2 ({\it left}) and IRS~13~E3Nc ({\it right}) where both E3N and E3c contribute to the emission. The ``sky'' and ``3.4$\mu$m'' labelled regions correspond to the partially corrected telluric methane absorption.} \label{fig3} \end{figure*} The previous NACO images have also revealed a new complex of IR red colour excess sources located at about 0.5'' north of the IRS~13 cluster. Eight sources have been resolved in the deconvolved images and labeled $\alpha$ through $\eta$ as shown in Figs. 1 and 2 of Eckart et al. (2004). \begin{figure} %\scalebox{0.6}{ \resizebox{8cm}{!}{\rotatebox{0}{\includegraphics{NACOspec.ps}}} % moultakafig3.eps}}} \caption{NACO {\it L'}-band AO spectra of the IRS~13N sources $\eta$, $\zeta$ and $\gamma$ obtained with NACO instrument. The ``sky'' and ``3.4$\mu$m'' labelled regions correspond to the partially corrected telluric methane absorption.} \label{fig2} \end{figure} In order to explain the unusual colors of these sources, the authors provide three different interpretations: 1- the sources could be bright young stars that are deeply embedded in the gas and dust of the minispiral or simply located behind a dense clump of gas and dust. 2- The second possibility is that they could be O-or B-type stars heating the gas and dust in their vicinity. In this case, they could be low luminosity analogues of the bowshock sources, and in both cases, extinctions well above A$_V\sim$ 30 $mag$ are needed. 3- The third interpretation is that they may be young stellar objects as they show similar luminosities ($\sim 10^3$L$_\odot$) in addition to their red colors ($K-L\sim 4$ to $5$ mag). Moreover, when corrected for the visual extinction value A$_V\sim$30 mag toward the Galactic Center, their colors are shifted to the region of YSO and Herbig Ae/Be stars in the Color-Color diagram (Ishii et al. 1998) (see Fig. 3 of Eckart et al. 2004). In addition, in Moultaka et al. (2004), the ISAAC spectrum of the IRS~13N region has been well-fitted with a reddened blackbody continuum of temperature T=1000K and the corrected spectrum for the foreground extinction is redder than the one of the IRS~13 cluster especially longward of 3.5$\mu$m. This shows that the L-band excess is due to the emission of warm (T$\sim$1000K) dust. \\ The NACO observations have resolved three of the very red new sources of the IRS13N region. These are the sources $\eta$, $\zeta$, and $\gamma$ along the same slit. The spectra show a redder continuum from $\eta$ to $\gamma$ as shown in Fig. \ref{fig2}, which agrees well with the colors of these sources (Eckart et al. 2004). This result indicates that these colors are affected by dust emission. Moreover, the lack of Pf$\gamma$ line emission in these spectra, which is prominent in the integrated lower spatial resolution ISAAC spectrum of the overall IRS~13N region as shown in Moultaka et al. (2004), also suggests that this line emission is very likely due to an extended nebular emission. Alternatively, it may originate in sources $\epsilon$ or $\delta$. % (see if we can obtain more information from the new ISAAC spectra ??????) \section{Conclusion and discussion} The L-band ISAAC observations allowed us to build the first spectroscopic L-band data cube of the IRS~3-IRS~13 region. Using the spectrum of the foreground extinction towards the Galactic Center derived in a previous paper Moultaka et al. (2004), we constructed the extinction-corrected data cube of the same region.\\ Maps of water ice absorption at $3.0\mu$m and of the hydrocarbon absorptions at $3.4\mu$m and $3.48\mu$m were then derived, as well as the Pf$\gamma$ and Br$\alpha$ emission line maps. The three absorption features - the water ice and the hydrocarbons - are good tracers of the ISM, molecular clouds, and the diffuse medium, respectively.\\ Analysis of the absorption feature maps showed that the features are present almost over the entire region and are surprisingly well-correlated. This suggests that the ISM in the studied area could be affected by turbulence or could be a mixture of a dense dusty and diffuse ionized medium. On the other hand, the observed maps and the extinction corrected ones are very similar, and the absorption features show varying strengths over the entire region, as much in the observed maps as in the extinction corrected maps. This consolidates our previous finding that these absorptions are most probably taking place locally at the position of the Galactic Center and can be associated with the bright sources, when they are found at their location.\\ The extended emission north-east and west to the probably hot, young, mass-losing star IRS~3 are well-traced in the ice and hydrocarbon maps. Since similar absorption distributions are also observed in the maps around the IRS~6E and the IRS~12N sources, a tempting question would be whether these sources are also mass-losing stars where outflows are interacting with their environment. The continuum images obtained from Adaptive Optics observations of the region (e.g. Genzel et al. 2003) show that IRS~6E and IRS~12N are embedded in highly extended emission and can hardly be distinguished from the minispiral. Moreover, the position of the IRS~13 complex shows similar concentrations of the absorptions north and south to IRS~13E where we have just located the position of a WR-type star. This also supports the idea that such concentrations may be created by the strong winds of neighboring massive stars. These results also stress the idea that a high spatial correlation occurs between these sources and the minispiral material.\\ %that when they are found at the location of a bright source they are associated with it.\\ The ISAAC emission line maps have revealed three WR-type stars located to the north and west of IRS~3. One of these has already been identified as a Wolf-Rayet type star from its K-band spectrum and the two remaing stars are reported in the present paper for the first time. The L-band spectra of the three sources show broad blueshifted helium emission lines. They correspond to FWHM line widths of about 1100 km/s and radial velocities of about -300 km/s. A better accuracy for these quantities should be obtained with spectroscopy in the NIR domain, where other WR-type stars have been identified.\\ Two of the new WR stars, WR1 and WR2, could belong to the two couter-rotating disks of young stars, as shown by their proper motions and radial velocities within the uncertainties. The northern star WR3 does not seem to be part of any of the two disks; but NIR spectroscopy should be undertaken to confirm these conclusions.\\ The NACO L-band observations allowed us to resolve three of the IRS~13N compact sources and the IRS~13E2 and E3Nc components of the IRS~13E complex. The absence of prominent emission lines in the IRS~13N sources, $\eta$, $\zeta$, and $\gamma$ shows that the red colors of these objects are probably due to dust. It also shows that the recombination line emission is mostly due either to extended nebular emission or to the remaining IRS~13N sources $\epsilon$ or $\delta$. On the other hand, the comparison of the NACO spectra of IRS~13E3 (IRS~13E3N and IRS~13E3c) and of IRS~13E2 suggests that the previously resolved E3c component can probably be identified with a dusty WR star. \\ This brings the number of new WR-type stars reported in this paper to three, which increases the number of massive hot WR stars in the central parsec by about 17\% over the total number obtained by Paumard et al. (2001,2003) and Tanner et al. (2004), including the five bowshock sources of the northern arm. It supports the conclusion of Tanner et al. (2004) that these sources are underestimated in the central parsec of the Milky-Way. %and NACO spectra of the IRS~3-IRS~13 region %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartesbandsby4p8IIOVI.eps}}} % \caption[]{cartesbandsby4p8IIOVI.eps} %\label{cartesbandsby4p8IIOVI.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartesbandsby4sm3p8IIOVI.eps}}} % \caption[]{Optical depth maps non corrected for extinction along the line of sight. {\it Middle:} Smoothed version of the optical depth map of the water ice absorption in the IRS~3-IRS~13 GC region. {\it Right:} Smoothed version of the optical depth map of the hydrocarbon feature. {\it Left:} Smoothed integrated map over the L-band wavelength domain for comparison. All over the three maps are also overlaid contours of the same images for clarity. (cartesbandsby4sm3p8IIOVI.eps???)} %\label{cartesbandsby4sm3p8IIOVI.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartesbandsby4p8IIOVIExtCorr.eps}}} % \caption[]{cartesbandsby4p8IIOVIExtCorr.eps} %\label{cartesbandsby4p8IIOVIExtCorr.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartesbandsby4sm3p8IIOVIExtCorr.eps}}} % \caption[]{Optical depth maps of the water ice ({\it middle}) and hydrocarbon ({\it right}) absorption features corrected for extinction along the line of sight. (cartesbandsby4sm3p8IIOVIExtCorr.eps???)} %\label{cartesbandsby4sm3p8IIOVIExtCorr.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartes3vs3p4by4p8IIOVI.eps}}} % \caption[]{cartes3vs3p4by4p8IIOVI.eps} %\label{cartes3vs3p4by4p8IIOVI.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartes3vs3p4by4sm3p8IIOVI.eps}}} % \caption[]{Same as in Fig. \ref{cartesbandsby4sm3p8IIOVI.eps} but the middle and right maps correspond respectively to the optical depths at $\sim3.0\mu$m and $\sim3.4\mu$m. (cartes3vs3p4by4sm3p8IIOVI.eps????)} %\label{cartes3vs3p4by4sm3p8IIOVI.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartes3vs3p4by4p8IIOVIExtCorr.eps}}} % \caption[]{cartes3vs3p4by4p8IIOVIExtCorr.eps} %\label{cartes3vs3p4by4p8IIOVIExtCorr.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartes3vs3p4by4sm3p8IIOVIExtCorr.eps}}} % \caption[]{Extinction corrected smoothed maps of the optical depths at $\sim3.0\mu$m ({\it middle}) and $\sim3.4\mu$m ({\it right}). (cartes3vs3p4by4sm3p8IIOVIExtCorr.eps????)} %\label{cartes3vs3p4by4sm3p8IIOVIExtCorr.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartes3vs3p8by4p8IIOVI.eps}}} % \caption[]{cartes3vs3p8by4p8IIOVI.eps} %\label{cartes3vs3p8by4p8IIOVI.eps}%\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartes3vs3p8by4sm3p8IIOVI.eps}}} % \caption[]{Same figure as Fig. \ref{cartes3vs3p4by4sm3p8IIOVI.eps} (non corrected for extinction) but the right figure maps the optical depth of hydrocarbon at $3.48\mu$m. (cartes3vs3p8by4sm3p8IIOVI.eps???)} %\label{cartes3vs3p8by4sm3p8IIOVI.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartes3vs3p8by4sm3p8IIOVIExtCorr.eps}}} % \caption[]{cartes3vs3p8by4sm3p8IIOVIExtCorr.eps} %\label{cartes3vs3p8by4sm3p8IIOVIExtCorr.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartesemissionnormby4p8IIOVI.eps}}} %{\includegraphics{cartesemissionnormby4p8IIO.eps}}} %COstar.eps}}} % \caption[]{cartesemissionnormby4p8IIOVI.eps} %\label{cartesemissionnormby4p8IIOVI.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartesemissionnormby4sm3p8IIOVI.eps}}} %{\includegraphics{cartesemissionnormby4sm3p8IIO.eps}}} %Taulineofsight4.eps}}} % \caption[]{Emission lines maps non corrected for extinction along the line of sight. {\it Middle:} Smoothed version of the Pf$_{\gamma}$ emission line map in the IRS~3-IRS~13 GC region. {\it Right:} Smoothed version of the Br$_{\alpha}$ emission line map. {\it Left:} Smoothed integrated map over the L-band wavelength domain for comparison. All over the three maps are also overlaid contours of the same images for clarity. (cartesemissionnormby4sm3p8IIOVI.eps???)} %\label{cartesemissionnormby4sm3p8IIOVI.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartesemissionnormby4p8IIOVIExtCorr.eps}}} %{\includegraphics{cartesemissionnormby4p8IIO.eps}}} %COstar.eps}}} % \caption[]{cartesemissionnormby4p8IIOVIExtCorr.eps} %\label{cartesemissionnormby4p8IIOVIExtCorr.eps} %\end{figure*} %\begin{figure*} % \resizebox{12cm}{!}{\rotatebox{-90}{\includegraphics{cartesemissionnormby4sm3p8IIOVIExtCorr.eps}}} %{\includegraphics{cartesemissionnormby4sm3p8IIO.eps}}} %Taulineofsight4.eps}}} % \caption[]{Same as in Fig. \ref{cartesemissionnormby4sm3p8IIOVI.eps} but here the maps are corrected for foreground extinction. (cartesemissionnormby4sm3p8IIOVIExtCorr.eps????)} %\label{cartesemissionnormby4sm3p8IIOVIExtCorr.eps} %\end{figure*} %\newpage %\begin{figure} % \resizebox{4cm}{!}{\rotatebox{0}{\includegraphics{raieRdivBextsm3p8IIOVI.eps}}} % \caption[]{Smoothed map of the $\frac{Br_{\alpha}}{Pf_{\gamma}}$ ratio with contours of the same image overlaid. (raieRdivBextsm3p8IIOVI.eps???)} %\label{raieRdivBextsm3p8IIOVI.eps} %\end{figure} %\begin{figure} % \resizebox{7.1cm}{!}{\rotatebox{90}{\includegraphics{carteby4p8IIOVIIV.eps}}} % \caption[]{\small{Maps of the IRS~3-IRS~13 GC region not corrected for % extinction along the line of sight. {\it (a)-} Smoothed integrated % map over the L-band wavelength domain. {\it (b)-} Smoothed version % of the optical depth map of the integrated water ice absorption over % the 2.84$\mu$m to 3.77$\mu$m spectral domain as explained in the % text. {\it (c)-} Smoothed version of the optical depth map of the % integrated hydrocarbon absorption feature from 3.32$\mu$m to % 3.77$\mu$m. {\it (d)-} Smoothed map of the optical depth % distribution at 3.0$\mu$m. {\it (e)-} Smoothed map of the optical % depth distribution at 3.4$\mu$m. {\it (f)-} Smoothed map of the % optical depth distribution at 3.48$\mu$m. {\it (g)-} Smoothed version % of the Pf$\gamma$ emission line map. {\it (h)-} Smoothed version % of the Br$\alpha$ emission line map. {\it (i)-} Smoothed version % of the Br$\alpha$/Pf$\gamma$ ratio. All over the maps are also overlaid contours of the same images for clarity.}} %\label{carteby4p8IIOVIIV.eps} %\end{figure} \begin{figure*} \begin{center} %%\newpage \resizebox{6.7cm}{!}{\rotatebox{90}{\includegraphics{carteby4p8IIOVIIVExtCorr.eps}}} \caption[]{\small{Maps of the IRS~3-IRS~13 GC region corrected for extinction along the line of sight. Over all the maps contours of the same images are also overlaid for clarity. {\it (a)-} Smoothed integrated map over the L-band wavelength domain. The contours correspond to relative intensity levels. {\it (b)-} Smoothed version of the optical depth map of the integrated water ice absorption over the 2.84$\mu$m to 3.77$\mu$m spectral domain as explained in the text. Contour values: 0.07, 0.13, 0.21, 0.27, 0.34, 0.41, 0.48, 0.55, 0.62, 0.69, 0.75, 0.82, 0.89, 0.96. {\it (c)-} Smoothed version of the optical depth map of the integrated hydrocarbon absorption feature from 3.32$\mu$m to 3.77$\mu$m. Contour values: 0.020, 0.028, 0.036, 0.044, 0.052, 0.060, 0.068, 0.075, 0.083, 0.091, 0.099, 0.107, 0.115 {\it (d)-} Smoothed map of the optical depth distribution at 3.0$\mu$m. Contour values: 0.17, 0.34, 0.51, 0.68, 0.85, 1.02, 1.19, 1.36, 1.53, 1.70, 1.87, 2.04, 2.21, 2.38 {\it (e)-} Smoothed map of the optical depth distribution at 3.4$\mu$m. Contour values: 0.04, 0.05, 0.07, 0.08, 0.09, 0.11, 0.12, 0.13, 0.15, 0.16, 0.18, 0.19, 0.20 {\it (f)-} Smoothed map of the optical depth distribution at 3.48$\mu$m.Contour values: 0.010, 0.02, 0.026, 0.031, 0.037, 0.043, 0.048, 0.054, 0.060, 0.066, 0.072, 0.077, 0.083 {\it (g)-} Smoothed version of the Pf$\gamma$ emission line map. Contour values: 0.02, 0.04, 0.06, 0.08, 0.11, 0.13, 0.15, 0.17, 0.19, 0.21, 0.24, 0.26, 0.28, 0.30, 0.32 {\it (h)-} Smoothed version of the Br$\alpha$ emission line map. Contour values: 0.044, 0.11, 0.19, 0.25, 0.33, 0.40, 0.47, 0.54, 0.61, 0.68, 0.76, 0.83, 0.90, 0.97, 1.04, 1.11, 1.18 {\it (i)-} Smoothed version of the Br$\alpha$/Pf$\gamma$ ratio. Contour values: 0.12, 0.45, 0.77, 1.10, 1.42, 1.75, 2.07, 2.40, 2.72, 3.05, 3.38, 3.70, 4.03.}} \label{carteby4p8IIOVIIVExtCorr.eps} \end{center} \end{figure*} %\bigskip % \caption[]{\small{{\bf Maps of the IRS~3-IRS~13 GC region corrected for % extinction along the line of sight. {\it (a)-} Smoothed integrated % map over the L-band wavelength domain. The contours correspond to values of the optical depth of 200000,1.09551e+06,1.99103e+06,2.88654e+06,3.78206e+06 %and $\geq$ 4.67757e+06, $\leq$ 4.40802e+07. {\it (b)-} Smoothed version % of the optical depth map of the integrated water ice absorption over % the 2.84$\mu$m to 3.77$\mu$m spectral domain as explained in the % text. Contour values: 0.343336, 0.686673,1.03001,1.37335,1.71668,2.06002,2.40335,,2.74669,3.09003,3.43336,3.7767,4.12004,4.46337,4.80671 %{\it (c)-} Smoothed version of the optical depth map of the % integrated hydrocarbon absorption feature from 3.32$\mu$m to % 3.77$\mu$m. Contour values: 0.1,0.139651,0.179302,0.218953,0.258604,0.298255,0.337907,0.377558,0.417209,0.45686,0.496511,0.536162,0.575813 {\it (d)-} Smoothed map of the optical depth % distribution at 3.0$\mu$m. Contour values: 0.849636,1.69927,2.54891,3.39854,4.24818,5.09781,5.94745,6.79709,7.64672,8.49636,9.34599,10.1956,11.0453,11.8949 {\it (e)-} Smoothed map of the optical % depth distribution at 3.4$\mu$m. Contour values: 0.2,0.268373,0.336747,0.40512,0.473493,0.541867,0.61024,0.678613,0.746987,0.81536,0.883733,0.952107,1.02048 {\it (f)-} Smoothed map of the % optical depth distribution at 3.48$\mu$m.Contour values: 0.07,0.0987975,0.127595,0.156392,0.18519,0.213987,0.242785,0.271582,0.30038,0.329177,0.357975,0.386772,0.41557 {\it (g)-} Smoothed version % of the Pf$\gamma$ emission line map. Contour values: 0.1,0.207994,0.315989,0.423983,0.531977,0.639971,0.747966,0.85596,0.963954,1.07195,1.17994,1.28794,1.39593,1.50393,1.61192 {\it (h)-} Smoothed version % of the Br$\alpha$ emission line map. Contour values: 0.22,0.576051,0.932101,1.28815,1.6442,2.00025,2.3563,2.71235,3.0684,3.42446,3.78051,4.13656,4.49261,4.84866,5.20471,5.56076,5.91681 {\it (i)-} Smoothed version % of the Br$\alpha$/Pf$\gamma$ ratio. Contour values: 0.6,2.22832,3.85663,5.48495,7.11327,8.74158,10.3699,11.9982,13.6265,15.2548,16.8832,18.5115,20.1398. All over the maps are also overlaid contours of the same images for clarity.}}} \begin{acknowledgement} This work was supported in part by the Deutsche Forschungsgemeinschaft (DFG) via grant SFB 494. F.N. acknowledges PNAYA2003-02785-E and AYA2004-08271-C02-02 grants and the Ramon y Cajal program. %We are grateful to all members of the ISAAC/VLT and the MPE 3D team. \end{acknowledgement} %=================================================================== \appendix %============================================================ \bibliographystyle{apj} %\rf{Allen, D.A. \& Wickramasinghe, D.T. 1981, Nature 294, 239} % %\rf{Baganoff, F. K., Bautz, M. W., Brandt, W. N., Chartas, G., % Feigelson, E. D., Garmire, G. P., Maeda, Y., Morris, M., % Ricker, G. R., Townsley, L. K., Walter, F. 2001, Nature, Volume 413, % Issue 6851, pp. 45-48 } % %\rf{Baganoff et al., % Proceedings of the Galactic Center Workshop, Nov. 3-8, 2002, Hawaii, % A. Cotera, T. Geballe, S. Markoff, H. 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