J/ApJ/825/91    Refined classification for Orion A protostars    (Lewis+, 2016)

Protostars at low extinction in Orion A. Lewis J.A., Lada C.J. <Astrophys. J., 825, 91-91 (2016)> =2016ApJ...825...91L 2016ApJ...825...91L (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Molecular clouds ; Extinction Keywords: galaxies: star formation; stars: protostars Abstract: In the list of young stellar objects (YSOs) compiled by Megeath et al. (2012, J/AJ/144/192) for the Orion A molecular cloud, only 44 out of 1208 sources found projected onto low extinction (AK<0.8mag) gas are identified as protostars. These objects are puzzling because protostars are not typically expected to be associated with extended low extinction material. Here, we use high resolution extinction maps generated from Herschel data, optical/infrared and Spitzer Space Telescope photometry and spectroscopy of the low extinction protostellar candidate sources to determine if they are likely true protostellar sources or contaminants. Out of 44 candidate objects, we determine that 10 sources are likely protostars, with the rest being more evolved YSOs (18), galaxies (4), false detections of nebulosity and cloud edges (9), or real sources for which more data are required to ascertain their nature (3). We find none of the confirmed protostars to be associated with recognizable dense cores and we briefly discuss possible origins for these orphaned objects. Description: In this paper, we re-examine the classification of low extinction protostars from the Megeath et al. catalog (2012, J/AJ/144/192) using stringent criteria based on SED modeling and informed by spectroscopic and imaging data from the literature. We use the YSO catalog of Megeath et al. and the extinction maps from Lombardi et al. (2014, J/A+A/566/A45) to identify the protostellar candidates that are projected on low (i.e., AK<0.8mag) extinction regions of the Orion A cloud. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 85 44 Low Ak source classification -------------------------------------------------------------------------------- See also: V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012) II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012) J/ApJS/224/5 : Herschel Orion Protostar Survey (HOPS): SEDs (Furlan+, 2016) J/A+A/589/A80 : APOGEE strings (Hacar+, 2016) J/A+A/566/A45 : Orion optical-depth and column-density maps (Lombardi+, 2014) J/ApJ/786/29 : Catalog of distances to molecular clouds (Schlafly+, 2014) J/ApJS/207/5 : YSOs in LDN 1641 with Hectochelle spectra (Fang+, 2013) J/AJ/144/192 : Spitzer survey of Orion A & B. I. YSO catalog (Megeath+, 2012) J/ApJ/752/59 : Low-mass population in L1641 (Hsu+, 2012) J/ApJ/723/1019 : Galactic SFR and gas surface densities (Heiderman+, 2010) J/A+A/504/461 : YSOs in L1630N and L1641 (Fang+, 2009) J/A+A/498/167 : Embedded sources in L 1688 (van Kempen+, 2009) J/A+A/496/153 : Molecular hydrogen flows along Ori A cloud (Davis+, 2009) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- [MGM2012] [122/2748] Candidate protostar number in Megeath et al. (2012, J/AJ/144/192) 6- 9 F4.2 mag Ak [0.08/0.8] K band extinction 11- 14 F4.2 mag e_Ak [0.01/0.06] Uncertainty in Ak 16- 26 A11 --- Si Si feature 28- 37 A10 --- Class Classification from this paper (1) 39- 59 A21 --- Notes Notes 61- 64 A4 --- --- [HOP-] 65- 67 I3 --- HOPS [25/382]? Herschel Orion Protostar Survey ID 69- 77 A9 --- HClass Herschel Orion Protostar Survey classification (2) 79- 85 A7 --- Ref Reference(s) (3) -------------------------------------------------------------------------------- Note (1): Classification as follows: Protostar = 10 sources Stage II = 18 sources fuzz = 7 sources Galaxy = 4 sources Unknown = 3 sources cloud edge = 2 sources "cloud edge" sources are associated with more structure than "fuzz" which are essentially blank fields in the NIR. Note (2): Classification from HOPS data (Herschel Orion Protostar Survey; Furlan et al. 2016, preprint) as follows: Flat = 12 sources Galaxy = 5 sources Class I = 3 sources Uncertain = 1 source Note (3): Reference as follows: 1 = Davis et al. (2009, J/A+A/496/153); 2 = Fang et al. (2013, J/ApJS/207/5); 3 = Fang et al. (2009, J/A+A/504/461); 4 = Herschel Orion Protostar Survey, Furlan et al. (2016, preprint); 5 = Hsu et al. (2012, J/ApJ/752/59) -------------------------------------------------------------------------------- History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Aug-2016
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