------------------------------------------------------------------------ eikenberry_s.tex AIP Conf. Proc., 2008, in press Message-ID: MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="-478107720-2045241309-1206380382=:827" X-Virus-Scanned: by UF Astronomy Mail Virus Scanner ks/14/4/2005 X-MailScanner-Information: Please contact the postmaster@aoc.nrao.edu for more information X-MailScanner: Found to be clean X-MailScanner-SpamCheck: not spam, SpamAssassin (not cached, score=1, required 5, autolearn=disabled, FB_WORD1_END_DOLLAR 1.00) X-MailScanner-SpamScore: s X-MailScanner-From: reba@astro.ufl.edu X-Spam-Status: No This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---478107720-2045241309-1206380382=:827 Content-Type: TEXT/PLAIN; charset=en_US Content-Transfer-Encoding: QUOTED-PRINTABLE %astro-ph/0803.3084=20 \documentclass[12pt,twoside]{article} \usepackage{xrb2007} \pagestyle{myheadings} \begin{document} % select your session by uncommenting the appropriate line %\session{Jets} %\session{Jet and Black Hole Binaries} %\session{Faint Galactic XRB Populations} %\session{Faint XRBs and Galactic LMXBs} %\session{Obscured XRBs and INTEGRAL Sources} %\session{ULXs} %\session{Extragalactic Populations} \session{Future Missions and Surveys} %\session{Population Synthesis} \shortauthor{Eikenberry} \shorttitle{F2GCS} \title{The FLAMINGOS-2 Galactic Center Survey} \author{Stephen S. Eikenberry} \affil{Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, 32611} \begin{abstract} Upon commissioning on Gemini South, FLAMINGOS-2 will be one of the most powerful wide-field near-infrared imagers and multi-object spectrographs ev= er built for use on 8-meter-class telescopes. In order to take best advantage= of the strengths of FLAMINGOS-2 early in its life cycle, the instrument team h= as proposed to use 21 nights of Gemini guaranteed time in 3 surveys -- the FLAMINGOS-2 Early Science Surveys (F2ESS). The F2ESS will encompass 3 corresponding science themes -- the Galactic Center, galaxy evolution, and star formation. In this paper, I review the design performance and status = of FLAMINGOS-2, and describe the planned FLAMINGOS-2 Galactic Center Survey. \end{abstract} \section{Introduction} Multi-object spectroscopy (MOS) is revolutionizing optical astronomy, in fields as far ranging as abundance studies of globular clusters to the large-scale structure of the Universe. Unlike the previously-common single-object spectrographs, MOS instruments have the capability to observe tens to hundreds of objects at a single time. This has enabled large increases in sample sizes for many studies - often as much as 2 or more ord= ers of magnitude. Near-infrared spectroscopy has lagged significantly behind optical spectroscopy, with the first instruments featuring large-format (1024x1024-pixel or larger) detector arrays appearing on telescopes in just the past few years. In particular, near-infrared MOS have only begun to appear very recently. The first fully-cryogenic IR MOS, FLAMINGOS, was developed at the University of Florida, has seen successful use at the Gemini South 8-m and MMT 6.5-m telescopes, and is currently in service as a facility instrument of the Kitt Peak 4-meter telescope (Elston et al. 2002)= =2E=20 FLAMINGOS-2 (Eikenberry et al. 2006) is a fully cryogenic near-infrared (0.9-2.5 $\mu m$) wide-field imager and multi-object spectrograph which is being built by the University of Florida Department of Astronomy for the Gemini South 8-m telescope on Cerro Pachon, Chile. FLAMINGOS-2 shares much= of the instrument heritage of FLAMINGOS (Elston et al. 2002), as both a wide-field imager and MOS. FLAMINGOS-2 differs from FLAMINGOS primarily in having optics and opto-mechanical systems optimized for the Gemini telescop= es, providing 0.18-arcsec pixels and a 6.2-arcmin field of view - covering approximately 6 times the solid angle of FLAMINGOS on the same telescopes. When commissioned on Gemini 2008, FLAMINGOS-2 will be one of the most powerful wide-field near-infrared imagers and multi-object spectrographs ev= er built for use on 8-meter-class telescopes. Upon completion of the FLAMINGOS-2 (F2) commissioning work, the F2 instrume= nt team at the University of Florida (UF) will have access to a number of nigh= ts of guaranteed observing time with F2 on Gemini. This team consists primari= ly of the Principal Investigator, Stephen Eikenberry, and Instrument Team Scientists, S. Nicholas Raines, Reba Bandyopadhyay, and Anthony Gonzalez. = In order to take best advantage of the strengths of F2 early in its life cycle= , the instrument team has proposed that the majority of this guaranteed time = be used in 3 surveys - the FLAMINGOS-2 Early Science Surveys (F2ESS). The F2ES= S surveys will encompass 3 corresponding scientific themes - the Galactic Center, extragalactic astronomy, and star formation. Each of these surveys will be carried out by the F2 instrument team in collaboration with groups = of scientists drawn from the Gemini community and elsewhere, with the goal of maximizing the early scientific return from F2. In this paper, I will briefly review the designed performance characteristi= cs of FLAMINGOS-2 as well as the current instrument status. I will then move = on to a discussion of the FLAMINGOS-2 Galactic Center Survey (F2GCS). \section{FLAMINGOS-2 Overview \& Status} \label{sec:F2instrument} \subsection{Instrument Overview} FLAMINGOS-2 is an imaging spectrometer for use at the f/16 telescope follow= ing the collimator to produce a reimaged focal surface on the detector array wi= th 2048x2048 18$\mu m$ pixels. A combination of filters and grisms are placed near the pupil for broad- and narrow-band imaging and moderate-resolution spectroscopy. A pupil mask reduces excess thermal emission from the telesco= pe. The imaging mode field will form an inscribed circle on the detector. FLAMINGOS-2 may also be fed with a slower (f/30) beam provided by the Gemin= i Multi-Conjugate Adaptive Optics (MCAO) system. In spectroscopic mode, a selection of 9 MOS plates and 3 long slits mask off-target locations in the focal plane, passing target light through the collimator to a selectable gr= ism inserted into the beam after the pupil. The grism disperses the incident light, which is reimaged as a spectrum on the detector array by the camera optics. We present the basic optical performance requirements for FLAMINGO= S-2 below. \ \=20 \begin{tabular}{ll} % \toprule {\bf Parameter} & {\bf Value} \\ % \midrule Wavelength Range & $0.9 - 2.5 \mu$m \\ Imaging field of view & 6.2-arcmin circular \\ Pixel scale & $0.180 \pm 0.002$ arcsec \\ Detector & HAWAII-2 ($2048 \times 2048$) pix \\ MOS field of view & $6 \times 2$-arcmin \\ MOS multiplex gain & up to $\sim 100$ targets \\ Low-res spectroscopy & $R \sim 1300$ JH or HK bands \\ High-res spectroscopy & $R \sim 3300$ J, H, or K band \\ MCAO field of view & $3 \times 1$-arcmin \\ MCAO pixel scale & 90-mas/pixel \\ % \bottomrule \end{tabular} \=20 \=20 \subsection{FLAMINGOS-2 Status} FLAMINGOS-2 is currently undergoing final full-system testing at the University of Florida. The FLAMINGOS-2 instrument team at the University o= f Florida includes Steve Eikenberry (PI), Reba Bandyopadhyay, Greg Bennett, Richard Corley, Skip Frommeyer, Anthony Gonzalez, Kevin Hanna, Rick Herlevi= ch, David Hon, Jeff Julian, Roger Julian, Toni Marin, Charlie Murphey, Nick Raines, William Rambold, David Rashkind, Craig Warner, and the late Richard Elston. The FLAMINGOS-2 On-Instrument Wavefront Sensor was developed at th= e Herzberg Institute of Astrophysics in Canada by a team including Brian Leck= ie, Rusty Gardhouse, Jennifer Dunn, Murray Fletcher, Bob Wooff, and Tim Hardy. As of this writing, FLAMINGOS-2 has been fully integrated in the laboratory= at the University of Florida, and has successfully demonstrated high-performan= ce operation in all of its major modes. It will be shipped to Gemini South in 2008 for on-telescope commissioning. In addition to the instrument hardwar= e and control software, the UF team has developed a data pipeline tool for FLAMINGOS-2 called the Florida Analysis Tool Born Of Yearning for high quality scientific data (FATBOY). FATBOY combines Python scripting and code with PyRAF calls to provide imaging, long-slit spectroscopy, and MOS spectroscopy data reduction capabilities in a rapid, automated manner. It has been extensively tested with FLAMINGOS data, and is currently in scientific use at UF. \section{The F2 Galactic Center Survey} The FLAMINGOS-2 Galactic Center Survey (F2GCS) portion of the three F2ESS surveys is focused on the unusual properties of stars, gas, and black holes= at the center of the Milky Way. The key goals of the F2GCS are to study and identify the unuusal population of Chandra-identified X-ray sources at the Galactic Center, and to use the star formation history of this region to pr= obe the physics of the ``bulge/black-hole connection'' in galaxies. This surve= y is being led by team co-leads Steve Eikenberry (UF) and Bob Blum (NOAO). Other team members include F. Baganoff (MIT), F. Bauer (Columbia), R. Bandyopadhyay (UF), D. Crampton (HIA), C. Dewitt (UF), A. Gonzalez (UF), M. Muno (Caltech), K. Olsen (NOAO), N. Raines (UF), and K. Sellgren (Ohio State). \subsection{X-ray Sources in the F2GCS} The Galactic Center is a wonderful and mysterious place in our local Univer= se. It contains a supermassive black hole in Sgr A*, loads of massive stars and clusters and, importantly, more than $2000$ identifiable X-ray point source= s in its central region (Muno et al. 2006). These X-ray sources are unusual = in their properties, being both faint (typical luminosities $L_x < 10^{34} \ {= \rm ergs \ s^{-1}}$) and spectrally hard. These properties and their number density at the Galactic Center are not compatible with other known source populations in the Galaxy. Historically, much of the information on X-ray binary source populations in the Galaxy has come from studies of optically- and infrared-identified counterparts. From them, one can determine the donor star type and thus a rough mass estimate. Furthermore, optical/IR studies can frequently reveal variations in brightness and/or wavelength to determine the binary period a= nd mass function of the system -- two critical parameters for assessing the nature of the underlying sources. However, this is a non-trivial task in t= he Galactic Center region. First of all, the high reddening ($A_V \sim 20-40$ mag) makes optical observations highly impractical, so that only infrared techniques are efficient for these studies. Secondly, the fields are highl= y crowded. Virtually every Chandra X-ray source has an IR counterpart candid= ate within $\sim 1$-arcsec at $K<16$ mag -- but our statistical analyses indica= te that $\sim 85 \%$ of these candidates are spurious chance superpositions. Thus, we need to sort the ``wheat'' from the ``chaff''. FLAMINGOS-2 presents the perfect tool for carrying this out. IR spectrosco= py of potential targets can separate out many false positives, in that X-ray binaries often carry spectral signatures of accretion -- particularly emiss= ion lines such as Br$\gamma$, HeI, and HeII (e.g. Mikles et al. 2006). Observi= ng all 2000 IR candidates should yield $\sim 300$ newly-identified X-ray binar= ies in the Galactic Center region -- increasing the number of such optical/IR identifications in this region by 2 orders of magnitude and effectively doubling the entire Galactic sample of optical/IR X-ray binary counterparts= =2E With previous instruments, such observations would take about 1 hour per target on an 8-meter-class telescope -- or roughly 250 nights of Gemini tim= e (!!). However, the massive multiplex gain of FLAMINGOS-2 will allow us to accomplish this task in $\sim 5-7$ nights of observation -- an eminently feasible task.=20 \subsection{Star Formation History and the F2GCS} While the F2GCS will find many X-ray source counterparts in a relatively sh= ort amount of time, the fundamental efficiency of searching will only be $\sim = 15 \%$, as set by the expected ``false coincidence'' rate (see above). Howeve= r, we will not simply ``waste'' the resulting $\sim 1700$ IR spectra. Rather, these HK $R \sim 1300$ spectra will be combined with another $\sim 3000$ st= ars selected from our pre-imaging survey to provide nearly $5000$ spectra of st= ars in this field -- primarily Red Giant Branch (RGB) stars. This will produce= a master catalog of many such stars in this field, and the spectra will cover both the $H/K$ ``steam'' bands and the CO absorption bands. Combining measurements of these features will allow us to measure the luminosity clas= s and extinction for each individual star. Combining these with photometry (already obtained from the CTIO 4-meter telescope and ISPI instrument -- se= e Dewitt et al., these proceedings) will provide $M_{bol}$ and $T_{eff}$ for each star. This in turn places them on a Hertzsprung-Russell diagram. Blum et al. (2003) used a similar approach based on 75 stars to constrain the star formation history of the Galactic Center region. The F2GCS will increase the sample size for this work by nearly 2 orders of magnitude (!). Just as importantly, the F2GCS will reach much ($\Delta K \ \sim 5$ mag) fainter than the previous work, and thus be dominated by stars for which systematic errors due to atmospheric spectral variations are minimized. In this way, we can constrain the star formation history of the Galactic Center over the past 4 billion years. Since these stars are effectively ``fossil tracers'' of the motion of star-forming gas through the region over this long time, we should be able to link this flow to the mass evolution history of the super-massive black hole in Sgr A*. \begin{thebibliography} \bibitem{} Blum, R. D., Ram=C3=ADrez, Solange V., Sellgren, K., Olsen, K. 2= 003, ApJ, 597, 323 \bibitem{} Eikenberry, Stephen, Elston, Richard, Raines, S. Nicholas, Julia= n, Jeff, Hanna, Kevin, Hon, David, Julian, Roger, Bandyopadhyay, R., Bennet= t, J. Greg, Bessoff, Aaron, Branch, Matt, Corley, Richard, Eriksen, John-D= avid, Frommeyer, Skip, Gonzalez, Anthony, Herlevich, Michael, Marin-Franch= , Antonio, Marti, Jose, Murphey, Charlie, Rashkin, David, Warner, Craig, = Leckie, Brian, Gardhouse, W. Rusty, Fletcher, Murray, Dunn, Jennifer, Wooff= , Robert, Hardy, Tim 2006, Proc. of SPIE, 6269, 39 \bibitem{} Elston, R. 2002, Proc. of SPIE, 4841, 1611 \bibitem{} Mikles, Valerie J., Eikenberry, Stephen S., Muno, Michael P., Ba= ndyopadhyay, Reba M., Patel, Shannon 2006, ApJ, 651, 408 \bibitem{} Muno, M. P., Bauer, F. E., Bandyopadhyay, R. M., Wang, Q. D. 200= 6, ApJS, 165, 173 \end{thebibliography} \end{document} k ---478107720-2045241309-1206380382=:827--