INTRINSICALLY RED SOURCES OBSERVED BYSPITZERIN THE GALACTIC MIDPLANE

Abstract

We present a highly reliable flux-limited census of 18,949 point sources in the Galactic midplane that have intrinsically red mid-infrared colors. These sources were selected from the Spitzer Space Telescope Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIMPSE) I and II surveys of 274 deg 2 of the Galactic midplane, and consist mostly of high-and intermediate-mass young stellar objects (YSOs) and asymptotic giant branch (AGB) stars. The selection criteria were carefully chosen to minimize the effects of positiondependent sensitivity, saturation, and confusion. The distribution of sources on the sky and their location in the Infrared Array Camera and the Multiband Image Photometer for Spitzer 24 μm color-magnitude and colorcolor space are presented. Using this large sample, we find that YSOs and AGB stars can be mostly separated by simple color-magnitude selection criteria into approximately 50%-70% of YSOs and 30%-50% of AGB stars. Planetary nebulae and background galaxies together represent at most 2%-3% of all the red sources. 1004 red sources in the GLIMPSE II region, mostly AGB stars with high mass-loss rates, show significant (0.3 mag) variability at 4.5 and/or 8.0 μm. With over 11,000 likely YSOs and over 7000 likely AGB stars, this is to date the largest uniform census of AGB stars and high-and intermediate-mass YSOs in the Milky Way Galaxy.

Discovering protostars and their host clusters via WISE

“…Ultimately, the results will bolster the statistics linked to supporting new theories of star-formation (e.g., the 'fireworks hypothesis', Koenig et al 2012), and constraining parameters such as the star formation rate and local starburst history (e.g., Bonatto & Bica 2011 A JHK s color-color diagram ( Fig. 1) is compiled for the YSO candidates highlighted by Doppmann et al (2005), Robitaille et al (2008), Gutermuth et al (2010), Straižys & Kazlauskas (2010), Majaess et al (2012), andRosvick et al (2012, in prep) 3 . Fig.…”

“…Field contamination appears reduced since < 10% of the AGB stars identified by Robitaille et al (2008) were classified as YSO candidates via the present hybrid selection scheme. Robitaille et al (2008) did not assess YSOs with close neighbors (Fig. 2) in order to mitigate crowding/blending, and adopt α > −1.2 as a threshold to detect class II objects.…”

“…Only targets with S/N> 5 in all WISE passbands were examined, as longer-wavelength 22 µm data are valuable for culling non-YSO contaminants (see also Robitaille et al 2008). ∼ 20% of the YSO candidates identified toward the Serpens cloud may be reddened giants masquerading as class II/III sources (Evans et al 2009, and references therein).…”

“…1 The latest generation of infrared surveys are aptly tailored to detect YSOs and their host environments. Robitaille et al (2008), Evans et al (2009), andGutermuth et al (2010) used Spitzer data to classify > 13 × 10 3 YSOs. Borissova et al (2011) discovered 96 candidate clusters 2 in the VVV survey (Minniti et al 2010), while Mercer et al (2005) identified 92 star clusters via GLIMPSE data (see also Froebrich et al 2007;Kronberger et al 2006).…”

Highly Variable Young Massive Stars in Atlasgal Clumps

“…The photometric data compiled for the 13 objects are tabulated in Table 2. It includes the four Spitzer IRAC bands from the GLIMPSE survey (3.6μm, 4.5μm, 5.8μm, 8μm), two bands from the WISE survey (12μm, 22μm), Spitzer MIPS photometry at the 24μm band (Robitaille et al 2008), five bands from the Herschel-HiGal survey (70μm, 170μm, 250μm, 350μm, 500μm), and the ATLASGAL 850μm band. Whenever MIPS 24μm photometry is available, the WISE 22μm is ignored to ensure using the higher-quality data.…”