VISION - Vienna survey in Orion. III. Young stellar objects in Orion A

Josefa E. Großschedl, João Alves, Paula S. Teixeira, Hervé Bouy, Jan Forbrich, Charles J. Lada, Stefan Meingast, Álvaro Hacar, Joana Ascenso, Christine Ackerl, Birgit Hasenberger, Rainer Köhler, Karolina Kubiak, Irati Larreina, Lorenz Linhardt, Marco Lombardi, Torsten Möller

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We extend and refine the existing young stellar object (YSO) catalogs for the Orion A molecular cloud, the closest massive star-forming region to Earth. This updated catalog is driven by the large spatial coverage (18.3 deg^2, ~950 pc^2), seeing limited resolution (~0.7''), and sensitivity (Ks<19 mag) of the ESO-VISTA near-infrared survey of the Orion A cloud (VISION). Combined with archival mid- to far-infrared data, the VISTA data allow for a refined and more robust source selection. We estimate that among previously known protostars and pre-main-sequence stars with disks, source contamination levels (false positives) are at least ∼7% and ∼2.5%, respectively, mostly due to background galaxies and nebulosities. We identify 274 new YSO candidates using VISTA/Spitzer based selections within previously analyzed regions, and VISTA/WISE based selections to add sources in the surroundings, beyond previously analyzed regions. The WISE selection method recovers about 59% of the known YSOs in Orion A's low-mass star-forming part L1641, which shows what can be achieved by the all-sky WISE survey in combination with deep near-infrared data in regions without the influence of massive stars. The new catalog contains 2978 YSOs, which were classified based on the de-reddened mid-infrared spectral index into 188 protostars, 184 flat-spectrum sources, and 2606 pre-main-sequence stars with circumstellar disks. We find a statistically significant difference in the spatial distribution of the three evolutionary classes with respect to regions of high dust column-density, confirming that flat-spectrum sources are at a younger evolutionary phase compared to Class IIs, and are not a sub-sample seen at particular viewing angles.
Original languageEnglish
JournalAstronomy & Astrophysics
Publication statusPublished - 30 Sept 2018


  • astro-ph.SR
  • astro-ph.GA


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