Identification of Young Stellar Objects in the Second Galactic Quadrant

Identification of Young Stellar Objects in the Second Galactic Quadrant
Leśniewska, A.1 , Karska, A.2,1 , Siódmiak, N.3 , Szczerba, R.3 , Sewilo, M.4,5 , Whitney, B.6
1
Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, ul. Sloneczna 36, 60-286 Poznań,
Poland
2
Centre for Astronomy, Nicolaus Copernicus University, Faculty of Physics, Astronomy and Informatics, ul. Grudziadzka 5, 87-100 Toruń, Poland
3
N. Copernicus Astronomical Center, PAS, ul. Rabiańska 8, 87-100 Toruń, Poland
4
NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20771, USA
5
Astronomical Observatory of the Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland
6
Space Science Institute, 4750 Walnut St., Suite 205, Boulder, CO 80301, USA
Young Stellar Objects (YSOs) in the Outer Galaxy allow us to probe the star formation process in the environment of low metallicity, reduced cosmic ray flux, and low molecular cloud densities compared to the inner Galactic
disk. We use the data from the Spitzer Space Telescope SMOG survey (PI S. Carey; 3.6–24 µm) to identify YSOs
in the Second Galactic Quadrant. The SMOG survey, covering regions with l ∼ (102◦ , 109◦ ) and b ∼ (-0.2◦ , 3.2◦ ),
probes three spiral arms: the Local, Perseus, and the Outer arm.
We combine the Spitzer/SMOG catalogue with point source catalogues from the 2MASS, UKIDSS, AllWISE, MSX,
and AKARI surveys and construct color-color diagrams (CCDs) to separate YSOs from evolved stars and extragalactic
sources. Our YSO identification method is based on the procedures developed for nearby star forming regions (e.g.,
Gutermuth et al. 2008) and for the Large and Small Magellanic Clouds (e.g., Whitney et al. 2008; Sewilo et al. 2013).
We will compare our results to the results of the study on YSOs in the third Galactic quadrant (Sewilo et al., in prep.)
and to the inner Galaxy studies to investigate the impact of the environment on star formation.
Figure 1: An example CCD used for the YSO identification: [3.6]-[5.8] vs. [4.5]-[8.0]. The locations of spectroscopically
confirmed YSOs in the LMC (squares; Woods et al. 2011) and SMC (triangles; Ruffle et al. 2015) are overlaid; they
are used to identify regions in the CCDs occupied by bona-fide YSOs. Extragalactic sources (shown in orange) are
separated using the criteria from Gutermuth et al. (2008; dashed lines).
References
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