MASSIVE YOUNG STELLAR OBJECTS IN THE GALACTIC CENTER. I. SPECTROSCOPIC IDENTIFICATION FROMSPITZERINFRARED SPECTROGRAPH OBSERVATIONS

2011/04/25 by Deokkeun An, Solange V. Ramírez, Solange Ramírez +15 · 2 citations
Chemistry · Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxy #Infrared #Milky Way #Physics #Population #Spectral line #Spectrograph #Spectroscopy and Laser Applications #Spitzer Space Telescope #Star formation #Stellar, planetary, and galactic studies #Telescope #Young stellar object #astro-ph.GA #astro-ph.SR

paper · pdf · doi:10.1088/0004-637x/736/2/133

Accepted for publication in ApJ

arxiv created 2011/04/25 · openalex publication_date 2011/07/19 · arxiv updated 2015/05/28 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

We present results from our spectroscopic study, using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope , designed to identify massive young stellar objects (YSOs) in the Galactic center (GC). Our sample of 107 YSO candidates was selected based on Infrared Array Camera (IRAC) colors from the high spatial resolution, high sensitivity Spitzer /IRAC images in the Central Molecular Zone, which spans the central ∼300 pc region of the Milky Way. We obtained IRS spectra over 5–35 μm using both high- and low-resolution IRS modules. We spectroscopically identify massive YSOs by the presence of a 15.4 μm shoulder on the absorption profile of 15 μm CO 2 ice, suggestive of CO 2 ice mixed with CH 3 OH ice on grains. This 15.4 μm shoulder is clearly observed in 16 sources and possibly observed in an additional 19 sources. We show that nine massive YSOs also reveal molecular gas-phase absorption from CO 2 , C 2 H 2 , and/or HCN, which traces warm and dense gas in YSOs. Our results provide the first spectroscopic census of the massive YSO population in the GC. We fit YSO models to the observed spectral energy distributions and find YSO masses of 8–23 M ☉ , which generally agree with the masses derived from observed radio continuum emission. We find that about 50% of photometrically identified YSOs are confirmed with our spectroscopic study. This implies a preliminary star formation rate of ∼0.07 M ☉ yr −1 at the GC.

Citations

• Interpreting Spectral Energy Distributions from Young Stellar Objects. II. Fitting Observed SEDs Using a Large Grid of Precomputed Models
• A CATALOG OF 24 μm SOURCES TOWARD THE GALACTIC CENTER
• Sp i t zer Mid-Infrared Spectroscopy of Ices toward Extincted Background Stars
• New Catalogs of Compact Radio Sources in the Galactic Plane
• Point Sources from aSpitzerIRAC Survey of the Galactic Center
• Gas-phase CO₂ toward massive protostars
• Hubble Space Telescope/NICMOS Observations of Massive Stellar Clusters near the Galactic Center
• The Spitzer Space Telescope Mission
• The United Kingdom Infrared Telescope Infrared Deep Sky Survey First Data Release
• Two‐dimensional Radiative Transfer in Protostellar Envelopes. II. An Evolutionary Sequence
• The Two Micron All Sky Survey (2MASS)
• Young massive stars in the ISOGAL survey

Cited by

• INFRARED H₃⁺ AND CO STUDIES OF THE GALACTIC CORE: GCIRS 3 AND GCIRS 1W
• Near-infrared spectroscopic observations of massive young stellar object candidates in the central molecular zone