------------------------------------------------------------------------ From: "Don F. Figer" figer@stsci.edu Subject: submission Mime-Version: 1.0 X-Keywords: %this is 2-column %\documentstyle[12pt,aas2pp4, epsf]{article} %this is one column, double-space \documentstyle[12pt,aasms4, epsf]{article} %this is one column, single-spaced %\documentstyle[12pt,aaspp4, epsf]{article} \def\nheh{\hbox{n$_{\rm He}$/n$_{\rm H}$}} \def\nnihe{\hbox{n$_{\rm N}$/n$_{\rm He}$}} \def\Mdot{\hbox{$\dot {M}$}} \def\Rsun{\hbox{\it R$_\odot$}} \def\Rstar{\hbox{\it R$_*$}} \def\Lsun{\hbox{\it L$_\odot$}} \def\Lstar{\hbox{\it L$_*$}} \def\Msun{\hbox{\it M$_\odot$}} \def\Minit{\hbox{\it M$_{\rm initial}$}} \def\Msunyr{\hbox{\it M$_\odot\,$yr$^{-1}$}} \def\Myr{\hbox{\it Myr}} \def\Gyr{\hbox{\it Gyr}} \def\Teff{\hbox{\it T$_{\rm eff}$}} \def\Vinf{\hbox{$v_\infty$}} \def\kms{\hbox{km$\,$s$^{-1}$}} \def\AV{\hbox{\it A$_{\rm V}$}} \def\AJ{\hbox{\it A$_{\rm J}$}} \def\AH{\hbox{\it A$_{\rm H}$}} \def\AK{\hbox{\it A$_{\rm K}$}} \def\K{\hbox{\it K}} \def\AL{\hbox{\it A$_{\rm L}$}} \def\BCK{\hbox{BC$_{\rm K}$}} \def\BCV{\hbox{BC$_{\rm V}$}} \def\simgr{\mathrel{\hbox{\rlap{\hbox{\lower4pt\hbox{$\sim$}}}\hbox{$>$}}}} \def\HH{H{\sc ii}} % HII region \makeatletter \def\jnl@aj{AJ} \ifx\revtex@jnl\jnl@aj\let\tablebreak=\nl\fi \makeatother \received{October 12, 1999} \revised{REVISION DATE} \accepted{January 10, 2000} \journalid{VOL}{JOURNAL DATE} \articleid{START PAGE}{END PAGE} \paperid{MANUSCRIPT ID} \cpright{TYPE}{YEAR} \ccc{CODE} \lefthead{Figer et al.} \righthead{Sgr~A$^*$} \begin{document} \title{2 \micron\ Spectroscopy within 0\farcs3 of Sgr~A$^*$} \author{ Donald F. Figer\altaffilmark{2}, E. E. Becklin\altaffilmark{3}, Ian S. McLean\altaffilmark{3}, \\ Andrea M. Gilbert\altaffilmark{4}, James R. Graham\altaffilmark{4}, James E. Larkin\altaffilmark{3}, \\ N. A. Levenson\altaffilmark{5}, Harry I. Teplitz\altaffilmark{6,}\altaffilmark{7}, Mavourneen K. Wilcox\altaffilmark{3}, \\ Mark Morris\altaffilmark{3}} \authoremail{figer@stsci.edu} \altaffiltext{2}{Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; figer@stsci.edu } \altaffiltext{3}{Department of Physics and Astronomy, University of California, Los Angeles, Division of Astronomy, Los Angeles, CA, 90095-1562 } \altaffiltext{4}{Department of Astronomy, University of California, Berkeley, 601 Campbell Hall, Berkeley, CA, 94720-3411} \altaffiltext{5}{Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218} \altaffiltext{6}{Laboratory for Astronomy and Solar Physics, Code 681, Goddard Space Flight Center, Greenbelt MD 20771} \altaffiltext{7}{NOAO Research Associate} \begin{abstract} We present moderate (R~$\approx$~2,700) and high resolution (R~$\approx$~22,000) 2.0$-$2.4 \micron\ spectroscopy of the central 0.1 square arcseconds of the Galaxy obtained with NIRSPEC, the facility near-infrared spectrometer for the Keck II telescope. The composite spectra do not have any features attributable to the brightest stars in the central cluster, i.e.\ after background subtraction, W$_{\rm ^{12}CO(2-0)}$~$<$~2~\AA. This stringent limit leads us to conclude that the majority, if not all, of the stars are hotter than typical red giants. Coupled with previously reported photometry, we conclude that the sources are likely OB main sequence stars. In addition, the continuum slope in the composite spectrum is bluer than that of a red giant and is similar to that of the nearby hot star, IRS16NW. It is unlikely that they are late-type giants stripped of their outer envelopes because such sources would be much fainter than those observed. Given their inferred youth ($\tau_{\rm age}$~$<$~20~\Myr), we suggest the possibility that the stars have formed within 0.1 pc of the supermassive black hole. We find a newly-identified broad-line component (V$_{\rm FWHM}$ $\approx$ 1,000 \kms) to the 2.2178 \micron\ [\ion{Fe}{3}] line located within a few arcseconds of Sgr~A$^*$. A similar component is not seen in the Br-$\gamma$ emission. \end{abstract} \keywords{Galaxy: center --- stars: formation --- techniques: spectroscopic --- ISM: individual (Sgr~A$^*$) --- infrared: stars} \section{Introduction} Recent high-resolution near-infrared imaging reveals a tight cluster of at least a dozen stellar sources projected within 0\farcs5 of the putative massive black hole in the Galactic Center\markcite{gen97,ghe98} (Genzel et al.\ 1997; Ghez et al.\ 1998). Genzel et al.\ (1997) suggest that this cluster contains early-type stars with initial masses $\sim$15 to 20 \Msun. While their low-resolution spectra (R $\approx$ 35) and photometry can be fit by early-type stars, they can also be fit by much lower mass K giants of a few \Msun. The implications for star formation near a massive black hole are heavily dependent on whether the stars are of early or late type. In the former case, the stars are a few \Myr\ old and probably formed very near to the central black hole. In the latter case, they are on the order of a \Gyr\ old and represent a central concentration of the general old population seen throughout the Galactic Center\markcite{ale99} (Alexander 1999). If stars have formed near the central black hole, then it is important to know the physical properties of the gas there. The intensity of recombination line emission can be used to constrain the gas density and ionizing environment near the center, and the line width might be used to probe the central mass to smaller size scales than the stellar velocity dispersions. With these issues in mind, we obtained high resolution (R $\sim$ 22,400) and moderate resolution (R $\sim$ 2,700) long-slit spectra of the central few arcseconds of the Galaxy in the 2.0$-$2.4 \micron\ region ({\it K}-band). We present spectra of the combined light from the central stellar sources\markcite{gen97} (hereafter the ``S sources''; Genzel et al.\ 1997), nearby stars, and ionized gas. \section{Observations and Data Reduction} The observations were obtained with NIRSPEC, the facility near-infrared spectrometer, on the Keck II telescope\markcite{mcl98,mcl99} (McLean et al.\ 1998, 1999). A log of observations is given in Table 1. The plate scale was measured by comparing the locations of the spectra of IRS7, IRS16NW, IRS33E, and IRS33W to the positions in Eckart \& Genzel\markcite{eck97} (1997), giving 0\farcs14$\times$0\farcs20 per pixel in the spectral$\times$spatial directions of the high-resolution mode, and 0\farcs20$\times$0\farcs14 per pixel in the spectral$\times$spatial directions of the low-resolution mode (note that the axes are flipped with respect to the camera in the two modes). The slit viewing camera (SCAM) was used to obtain images simultaneously with the spectra. We measured a plate scale for the SCAM of 0\farcs18 per pixel by comparing the locations of IRS16NW, IRS16NE, IRS33E, and IRS33W to those given by Eckart \& Genzel\markcite{eck97} (1997). From SCAM images, we estimate seeing (FWHM) of 0$\farcs$5 on 28 April 1999 and 0$\farcs$3 on 3 June 1999. We chose to use the 3-pixel-wide slit (0\farcs43) in high-resolution mode and the 2-pixel-wide slit (0\farcs39) in low-resolution mode in order to match the seeing. Quintuplet Star \#3, which is featureless in this spectral region\markcite{fig98} (see Figure 1 in Figer et al.\ 1998), was observed as a telluric standard\markcite{mon94} (nomenclature from Moneti, Glass, \& Moorwood 1994). Arc lamps containing Ar, Ne, Kr, and Xe, were observed to set the wavelength scale. A field relatively devoid of stars (RA~17$^{\rm h}$~44$^{\rm m}$~49$\fs$8, DEC~$-$28$^{\arcdeg}$~54$^{\arcmin}$~6$\farcs$8~, J2000) was observed to provide a dark current plus bias plus background image. A quartz tungsten halogen lamp was observed to provide a ``flat'' image. All data reduction was accomplished using IRAF routines\footnote {IRAF is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.}. Bad pixel removal, flat-fielding, and coadding of object-sky frame pairs were performed to produce the final spectral images. The spectra were extracted and then divided by a similarly extracted spectrum of the telluric standard corrected for its apparent spectral energy distribution\markcite{fig98} (Figer et al.\ 1998). \section{Analysis and Results} We have compared the flux in the spectrum to that expected from the stars in the slit\markcite{wiz99} (Wizinowich et al.\ 1999), and the detected flux in the low-resolution spectrum confirms our pointing. The total background-subtracted flux from the combined low-resolution spectrum is \K\ = 12.8, in good agreement with the sum of the previously reported fluxes for the sources, reported as \K\ = 12.6\markcite{gen97} (Genzel et al.\ 1997). Figure 1 shows the low resolution spectra for the S sources, IRS7, and IRS16NW. The spectra demonstrate the very deep CO absorption in the spectrum of a cool star (IRS7) and the total lack of any similar feature in that of a hot star (IRS16NW). The spectra for the S sources were extracted from synthetic apertures centered 1\farcs38 south of IRS16NW and 0\farcs75 wide to give W$_{\rm ^{12}CO(2-0)}$~$\approx$~6$\pm$2~\AA. Figure 2 shows that the CO bandhead strength gradually increases in apertures to the south of Sgr~A$^*$, and to the north of IRS16NW. For instance, W$_{\rm ^{12}CO(2-0)}$~$\approx$~11$\pm$2~\AA\ for an aperture centered 0\farcs78 to the south of Sgr~A$^*$. A similar measurement for $\iota$ Cep (K0III), whose spectrum was taken from the Kleinmann \& Hall atlas\markcite{kle86} (1986), gives W$_{\rm ^{12}CO(2-0)}$~=~11.5 \AA; note that later red giants would have deeper CO absorption. It appears, then, that the off-source spectrum is similar to that of a K giant. The total on-source continuum flux level (with background) is about 1.8 times the off-source flux level. So, if the collective spectrum for the S sources is truly featureless, and the spectrum of the background mimics that of a K giant, then we would expect to measure an equivalent width of 6~\AA\ in the combined spectrum, in good agreement with our measurements. We find that no more than 30\% of the light in the composite spectrum can come from K giants or later types. Note that this limit is conservatively determined by using the upper error limit of W$_{\rm ^{12}CO(2-0)}$~=~8~\AA, for the combined light spectrum. The spectrum of the light from all sources in the central 0\farcs39 $\times$ 0\farcs85 (EW $\times$ NS) suggests at least some population of stars earlier than K0, and we find that the nearest blue supergiant, IRS16NW, does not contribute significantly to the light falling in the aperture. The peak of the S sources is 1\farcs43 south of IRS16NW, and the point spread function (measured from IRS7) suggests that the light from IRS16NW should contribute $<$ 1\% of the total flux in the synthetic aperture. We are also interested in detecting possible emission-line flux from the stellar sources, in order to constrain their nature, and from any gas associated with the black hole, in order to constrain the physical properties of material near the black hole. The high resolution data are particularly useful for this purpose (see Table 1 and Figure 3). We find three distinct components to the Br-$\gamma$ emission: 1) a faint ``zero-velocity'' component which is distributed throughout the low-resolution slit region, and is not easily identified in Figure 3, 2) a very bright, high-velocity, component associated with the ``mini-spiral,'' and 3) a near-zero-velocity component near the position of Sgr~A$^*$ and extending 1\farcs5 to the north and 7\arcsec\ to the south. The first component can also be seen in the H$_{2}$ (2.122 \micron) and \ion{He}{1} (2.058 \micron) lines, suggesting that \ion{H}{1} and \ion{He}{1} gas are distributed in projection over the whole region, and are being ionized by the ambient radiation field. The third component varies considerably along the north-south direction in peak location, 0 $\lesssim$ V$_{\rm LSR}$ $\lesssim$ +55 \kms, and line width, 25~\kms~$\lesssim$~V$_{\rm FWHM}$~$\lesssim$~110~\kms, gradually increasing from south to north. At the position of Sgr~A$^*$, the emission is centered at V$_{\rm LSR}$~=~+15~\kms, and V$_{\rm FWHM}$~=~80 \kms\ at the peak emission. Within 2\arcsec\ of Sgr~A$^*$, the line center has a linear gradient of $+$18~\kms~arcsec$^{-1}$ (south-to-north), and the line width has a peak value of +90~\kms\ at $-$0\farcs6 south of Sgr~A$^*$. The only distinguishing characteristic of the emission at the location of Sgr~A$^*$ with respect to surrounding regions is the local maximum in the line width which is 50\% greater than the value $\approx$~1\arcsec\ in either direction. The otherwise nondescript appearance of the line emission near Sgr~A$^*$ suggests that it has little to do with the black hole. Forbidden iron-line emission can also be seen throughout the spectroscopic field. There appears to be a broad [\ion{Fe}{3}] emission line near 2.2178 \micron\ with V$_{\rm FWHM}$ $\approx$ 1,000 \kms, peaking near the center of the spectroscopic field shown in Figure 2; a similar broad feature is not seen in the Br-$\gamma$ line. There is also a velocity component of the [\ion{Fe}{3}] emission lines at 2.1451 \micron, 2.2178 \micron, 2.2420 \micron, and 2.3479 \micron\ which is narrow and follows the pattern of the mini-cavity, the spatial distribution of which agrees well that described in Lutz, Krabbe, \& Genzel\markcite{lut93} (1993). \section{Discussion} The S sources span a range of brightness of 14.0~$\leq$~\K~$\leq$~16.0, implying a range of absolute magnitudes of $-$3.2~$\leq$~M$_{\rm K}$~$\leq$~$-$1.1, assuming d=8000 pc\markcite{rei93} (Reid 1993) and \AK\ $\approx$ 2.7. The absolute magnitudes match those of O9V to B1V stars having 25~\Msun~$>$~\Minit~$>$~10~\Msun, and 6~\Myr~$<$~$\tau_{\rm age}$~$<$~20~\Myr\markcite{mey94} (assuming the Geneva models, twice mass loss rate, twice solar metallicity, and $\tau_{\rm age}$~$\sim$1~\Myr\ old; Meynet et al.\ 1994). The absolute magnitudes can also be fit by red giants of type K0III to K3III with ages $\approx$~1~\Gyr. The early-type stars are most easily distinguished from the red giants by the presence of CO absorption in the \K-band spectra of the latter. For instance, the deepest CO bandhead in the \K-band (2.2935 \micron) for an early K giant has W$_{\rm ^{12}CO(2-0)}$~$\approx$~11~\AA. The data suggest that the majority of the S sources in our synthetic aperture are hot stars formed within 0.1 pc of the black hole. This is in agreement with Genzel et al.\markcite{gen97} (1997) and Eckart, Ott, \& Genzel\markcite{eck99} (1999). It is unlikely that the observed stars are actually red giants minus their outer envelopes, such as might be produced via stellar collisions\markcite{lac82bai99} (Lacy, Townes, \& Hollenbach 1982; Bailey \& Davies 1999). Even a particularly luminous red giant ({\it L}~$\approx$~10$^4$~\Lsun) with its envelope stripped to an extent consistent with the lack of strong Br-$\gamma$ absorption would have \K~$>$~16, far too faint to be a likely candidate for the S sources. It is also unlikely that they have formed outside of the center and have been transported inward via dynamical friction. Using Figure 1 and equation 1 in Morris\markcite{mor93} (1993), we find that it would take longer than the lifetime of an O- or B-star to transport them into the center if they were formed more than 0.1 pc from the center. The requirements for star formation so near the supermassive black hole are extreme. Consider a protostellar clump of sufficient density to form an O-star near the black hole. Such a clump would need to be very dense to be bound against tidal disruption: \begin{equation} \rho_{\rm clump}~\gtrsim~3.53~{{M} \over {R_{\rm GC}^3}}, \end{equation} where {\it R$_{\rm GC}$} is the distance between the clump and the Galactic Center, and {\it M} is the enclosed mass within the orbit of the clump. Let's assume that the clump is as far away from the center as possible while still allowing for dynamical friction to operate as described above, i.e., {\it R$_{\rm GC}$}~$\approx$~0.1~pc. With M~=~2.6(10$^6$)~\Msun, we find, n$_{\rm clump}$~$\gtrsim$~4(10$^{11}$)~cm$^{-3}$. Since gas near the GC is presently at least 5 orders of magnitude less dense than this, one must appeal to a much denser environment during the formation epoch, or to an event which was exceptionally strongly compressive, or to both. As discussed by Morris, Ghez \& Becklin\markcite{mor99} (1999), the formation of stars this close to the supermassive black hole would inevitably be accompanied by the violent release of accretion energy with a total luminosity near the Eddington limit of the black hole, since the black hole would then be immersed in a relatively dense medium. Indeed, this outpouring of energy may be required to compress the gas to densities sufficient to overcome the tidal forces. Given the challenge of forming stars in this tidally extreme environment, other possibilities might be considered. For example, have the masses of these stars been built up by stellar coalescence or by continuous accretion, making them much older than we infer? The calculations of Lee\markcite{lee96} (1996) suggest that this is unlikely, although Bonnell, Bate, \& Zinnecker\markcite{bon98} (1998) argue that all stars with \Minit~$>$~10~\Msun\ form by coalescence in very young dense clusters; it remains to be seen if the steady-state conditions in the central parsec can mimic those in the formation epoch of a young cluster. Or are these ``stars'' really more exotic objects such as compact stars with atmospheres acquired by passage through a dense medium or by collisions with red giant stars\markcite{mor93} (Morris 1993)? Perhaps they are stars powered by dark matter annihilation in their interiors\markcite{sal89} (Salati \& Silk 1989), in which case they would be much longer-lived than a star of comparable mass. In any of these cases, the explanation for the presence of these stars would be exceedingly interesting, and continued investigation well worthwhile. \section{Conclusions} We find that about half a dozen of the stars projected within a few thousand AU of Sgr~A$^*$ have little, if any, CO absorption in their {\it K}-band spectra, indicating that the stars are hot. Coupled with their brightnesses, we suggest that the stars are OBV types, and therefore $<$~20~\Myr\ old. Given the lifetimes of such stars, it is improbable that they formed beyond 0.1 pc of the Galactic Center, forcing us to consider the possibility that gas clumps having n~$\gtrsim$~10$^{11}$~cm$^{-3}$ can exist within a few thousand AU of a supermassive black hole. \acknowledgements It is a pleasure to acknowledge the hard work of past and present members of the NIRSPEC instrument team at UCLA: Maryanne Angliongto, Oddvar Bendiksen, George Brims, Leah Buchholz, John Canfield, Kim Chin, Jonah Hare, Fred Lacayanga, Samuel B. Larson, Tim Liu, Nick Magnone, Gunnar Skulason, Michael Spencer, Jason Weiss and Woon Wong. In addition, we thank the Keck Director Fred Chaffee, CARA instrument specialist Thomas A. Bida, and all the CARA staff involved in the commissioning and integration of NIRSPEC. We especially thank our Observing Assistants Joel Aycock, Gary Puniwai, Charles Sorenson, Ron Quick and Wayne Wack for their support. Finally, we thank Diane Gilmore of STScI for assisting in preparing the figures. \clearpage \begin{deluxetable}{rcrrrcr} \small \tablewidth{0pt} \tablecaption{Log of Observations} \tablehead{ \colhead{Resolution\tablenotemark{a}} & \colhead{Filter} & \colhead{Integ.} & \colhead{Frames} & \colhead{Slit Size} & \colhead{PA} & \colhead{Date} } \startdata 22,400 & 1.561~\micron~$-$~2.312~\micron & 300 s. & 3 & 0$\farcs43\times 24\arcsec$ & 0$\arcdeg$ \& 90$\arcdeg$ & 28 April 1999 \nl 2,700 & 1.996~\micron~$-$~2.382~\micron & 50 s. & 15 & 0\farcs$39\times 42$\arcsec & 0$\arcdeg$ & 3 June 1999 \nl \enddata \tablenotetext{a}{The resolution is $\lambda$/$\Delta\lambda_{\rm FWHM}$, where $\Delta\lambda_{\rm FWHM}$ is the half-power line width of unresolved arc lamp lines. The slit width was 2 pixels in low-resolution mode and 3 pixels in high-resolution mode.} \tablecomments{All images were obtained using the multiple correlated read mode with 16 reads at the beginning and end of each integration.} \end{deluxetable} \small \clearpage \begin{references} \reference{ale99} Alexander, T. 1999, \apj, in press \reference{bai99} Bailey, V. C., \& Davies, M. B. 1999, \mnras, in press \reference{bon98} Bonnell, I. A., Bate, M. R., \& Zinnecker, H. 1998, \mnras, 298, 93 \reference{eck97} Eckart, A., \& Genzel, R. 1997, \mnras, 284, 576 \reference{eck99} Eckart, A., Ott, T., \& Genzel, R. 1999, A\&A, submitted \reference{fig98} Figer, D. F., Najarro, F., Morris, M., McLean, I. S., Geballe, T. R., Ghez, A. M., \& Langer, N. 1998, \apj, 506, 384 %\reference{gen96} Genzel, R., Thatte, N., Krabbe, A., Kroker, H., \& Tacconi-Garman, L. E. 1996, \apj, 472, 153 \reference{gen97} Genzel, R., Eckart, A., Ott, T., \& Eisenhauer, F. 1997, \mnras, 291, 219 \reference{ghe98} Ghez, A. M., Klein, B. L., Morris, M., \& Becklin, E. E. 1998, \apj, 509, 678 %\reference{han96} Hanson, M. M., Conti, P. S., \& Rieke, M. J. 1996, \apj, 107, 281 \reference{kle86} Kleinmann, S. G., \& Hall, D. N. B. 1986, \apjs, 62, 501 \reference{lac82} Lacy, J. H., Townes, C. H., \& D. J. 1982, \apj, 262, 120 \reference{lee96} Lee, H. M. 1996, in Dynamical Evolution of Galactic Center Star Cluster and Importance of Stellar Collisions, eds.\ L. Blitz \& P. Teuben (Dordrecht: Kluwer), 215 \reference{lut93} Lutz, D., Krabbe, A., Genzel, R. 1993, \apj, 418, L244 \reference{mcl98} McLean et al.\ 1998, SPIE Vol. 3354, 566 \reference{mcl99} McLean et al.\ 1999, \pasp, in preparation \reference{mey94} Meynet, G., Maeder, A., Schaller, G., Schaerer, D., \& Charbonnel, C. 1994, \aap\ Supp., 103, 97 \reference{mon94} Moneti, A., Glass, I. S. \& Moorwood, A. F. M. 1994, \mnras, 268, 194 \reference{mor93} Morris, M. 1993, \apj, 408, 496 \reference{mor99} Morris, M., Ghez, A. M., \& Becklin, E. E. 1999, Adv. Spa. Res., 23, 959 \reference{rei93} Reid, M. J. 1993, \araa, 31, 345 \reference{sal89} Salati, P., \& Silk, J. 1989, \apj, 338, 24 %\reference{tam96} Tamura, M., Werner, M. W., Becklin, E. E., \& Phinney, E. S. 1996, \apj, 467, 645 \reference{wiz99} Wizinowich, P. et al.\ 1999, in preparation \end{references} \newpage \figurenum{1} \figcaption[gcspectra.ps] {Low-resolution {\it K}-band spectra of the combined light from the S sources (S/N$\sim$120), IRS7 ($>$200), and IRS16NW (200). Reddened blackbody fits have been overplotted. We assume \AK~=~3.5 for IRS7 and 2.7 for the S sources and IRS16NW. Normalization factors and constant offsets are given in the plot labels.} \figurenum{2} \figcaption[ndts03xxbf2d.ps] {Spectra extracted from the low resolution data for synthetic apertures separated by 0\farcs36 in the north-south direction and offset with respect to Sgr~A$^*$. The y-axis gives location of the aperture with respect to Sgr~A$^*$ --- north is up. Normalization factors and constant offsets are given in the plot labels.} \figurenum{3} \figcaption[highres.ps] {High resolution spectral image, displayed in inverted grayscale, near the Br-$\gamma$ line. The slit orientation was north-south. Objects discussed in the text are located at offsets of 0$\arcsec$ (Sgr A*), +1$\arcsec$ (IRS16NW), and +6$\arcsec$ (IRS7).} \newpage % NOTE TO EDITOR: THIS FIGURE SHOULD BE PLACED IN 1 COLUMN \begin{figure} \epsscale{1} \hspace{3.75in} \plotone{../plots/gcspectra.ps} \hspace*{4.5in} \vskip .2in Figure 1 \end{figure} % NOTE TO EDITOR: THIS FIGURE SHOULD BE PLACED IN 1 COLUMN \begin{figure} \hspace{0.8in} \epsscale{.80} \plotone{../plots/ndts03xxbf2d.ps} \hspace*{4.5in} \vskip .2in Figure 2 \end{figure} % NOTE TO EDITOR: THIS FIGURE SHOULD BE PLACED IN 1 COLUMN \begin{figure} \epsscale{.80} \plotone{../plots/highres.ps} \hspace*{2.2in} \vskip .2in Figure 3 \end{figure} \end{document} ---------------------------------------------------------------------------------------- Donald F. Figer figer@stsci.edu STScI 410-338-4377 3700 San Martin Drive Baltimore, MD 21218 http://nemesis.stsci.edu/~figer/ ---------------------------------------------------------------------------------------- ------------- End Forwarded Message -------------