J/ApJ/921/81 M20 young stellar population (Kalari, 2021) ================================================================================ The young stellar population, distance, and cloud-cloud collision induced star formation scenario of the Trifid Nebula. Kalari V.M. =2021ApJ...921...81K (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Photometry, H-alpha Keywords: star formation - star forming regions - H II regions - young stellar objects - pre-main sequence stars Abstract: The Trifid Nebula is a young, nearby star-forming region where star formation is proposed to have been triggered by cloud-cloud collision (CCC), based on observations of molecular clouds. It offers a unique opportunity to test whether the CCC hypothesis is supported by the spatial distribution and star formation chronology of young stars. We present the first study of the optically visible pre-main sequence (PMS) population of the region using riH{alpha} imaging and Gaia astrometry. Combined with an analysis of young stellar objects (YSOs) using infrared imaging, we capture the spatial distribution and star formation chronology of the young stellar population. From the analysis, 15 Flat/Class I YSOs, 46 Class II YSOs, and 41 accreting PMS stars are identified (diskless/non-accreting sources are not included in the analysis). The distance based on Gaia parallaxes is ~1250pc, significantly closer than previously reported. The Class II YSOs and PMS stars (~1.5Myr old) are spread toward the edge of the molecular clouds. They are slightly younger than the estimated crossing time of ~2.7Myr and closer to the estimated dynamical age ~0.85Myr. Younger Class I YSOs are more concentrated spatially. There exists a cavity devoid of young stars where the two clouds overlap. This evidence suggests that the current generation of stars formed after the collision of two clouds ~1Myr ago, and this result can be corroborated using future spectroscopic studies. Description: Class I YSOs identified based on mid-infrared photometry, and Class II YSOs identified based on H{alpha} excess are listed. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 174 61 Infrared photometry of young stellar objects in the Trifid nebula table2.dat 203 41 Optical photometry, Gaia astrometry, and estimated stellar properties of pre-main sequence stars in the Trifid nebula -------------------------------------------------------------------------------- See also: II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008) II/341 : VPHAS+ DR2 survey (Drew+, 2016) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 17 A17 --- GLIMPSE GLIMPSE identifier (GLLL.llll+BB.bbbb) 19- 34 A16 --- 2MASS 2MASS catalog identifier 36- 37 I2 h RAh Right Ascension (J2000) 39- 40 I2 min RAm Right Ascension (J2000) 42- 46 F5.2 s RAs Right Ascension (J2000) 48 A1 --- DE- Declination sign (J2000) 49- 50 I2 deg DEd Declination (J2000) 52- 53 I2 arcmin DEm Declination (J2000) 55- 58 F4.1 arcsec DEs Declination (J2000) 60- 65 F6.3 mag Jmag ?=- 2MASS J band magnitude 67- 71 F5.3 mag e_Jmag ?=- Uncertainty in Jmag 73- 78 F6.3 mag Hmag ?=- 2MASS H band magnitude 80- 84 F5.3 mag e_Hmag ?=- Uncertainty in Hmag 86- 91 F6.3 mag Kmag ?=- 2MASS Ks band magnitude 93- 97 F5.3 mag e_Kmag ?=- Uncertainty in Kmag 99-104 F6.3 mag 3.6mag Spitzer/IRAC 3.6 um band magnitude 106-110 F5.3 mag e_3.6mag Uncertainty in 3.6mag 112-117 F6.3 mag 4.5mag Spitzer/IRAC 4.5 um band magnitude 119-123 F5.3 mag e_4.5mag Uncertainty in 4.5mag 125-130 F6.3 mag 5.8mag Spitzer/IRAC 5.8 um band magnitude 132-136 F5.3 mag e_5.8mag Uncertainty in 5.8mag 138-143 F6.3 mag 8.0mag Spitzer/IRAC 8.0 um band magnitude 145-149 F5.3 mag e_8.0mag Uncertainty in 8.0mag 151-154 F4.2 mag 24mag ?=- Spitzer/MIPS 24 um band magnitude 156-159 F4.2 mag e_24mag ?=- Uncertainty in 24mag 161-165 F5.2 --- alpha IR SED slope 167-169 F3.1 --- e_alpha Uncertainty in alpha 171-174 A4 --- Class Classification -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 12 I12 --- VPHAS+ VPHAS+ DR3 identifier 14- 15 I2 h RAh Right Ascension (J2000) 17- 18 I2 min RAm Right Ascension (J2000) 20- 24 F5.2 s RAs Right Ascension (J2000) 26 A1 --- DE- Declination sign (J2000) 27- 28 I2 deg DEd Declination (J2000) 30- 31 I2 arcmin DEm Declination (J2000) 33- 36 F4.1 arcsec DEs Declination (J2000) 38- 43 F6.3 mag rmag Apparent r band magnitude (Vega) 45- 49 F5.3 mag e_rmag Uncertainty in rmag 51- 56 F6.3 mag imag Apparent i band magnitude (Vega) 58- 62 F5.3 mag e_imag Uncertainty in imag 64- 69 F6.3 mag Hamag Apparent H{alpha} band magnitude 71- 75 F5.3 mag e_Hamag Uncertainty in Hamag 77- 83 F7.2 0.1nm EWHa H{alpha} equivalent width 85- 88 F4.1 0.1nm e_EWHa Uncertainty in EWHa 90- 95 F6.3 mas/yr pmRA Gaia EDR3 proper motion along RA 97-101 F5.3 mas/yr e_pmRA Uncertainty in pmRA 103-108 F6.3 mas/yr pmDE Gaia EDR3 proper motion along Declination 110-114 F5.3 mas/yr e_pmDE Uncertainty in pmDE 116-122 F7.4 mas Plx Gaia EDR3 parallax 124-129 F6.4 mas e_Plx Uncertainty in plx 131-136 F6.3 mag Jmag ?=- 2MASS J band magnitude 138-142 F5.3 mag e_Jmag ?=- Uncertainty in Jmag 144-149 F6.3 mag Hmag 2MASS H band magnitude 151-155 F5.3 mag e_Hmag Uncertainty in Hmag 157-162 F6.3 mag Kmag ?=- 2MASS Ks band magnitude 164-168 F5.3 mag e_Kmag ?=- Uncertainty in Ksmag 170-173 F4.2 Msun Mass Mass 176-179 F4.2 Msun E_Mass Upper uncertainty in Mass (1) 182-185 F4.2 Msun e_Mass Lower uncertainty in Mass (1) 187-191 F5.2 Myr Age Age 193-196 F4.2 Myr E_Age Upper uncertainty in Age (1) 199-203 F5.2 Myr e_Age Lower uncertainty in Age (1) -------------------------------------------------------------------------------- Note (1): Mass and age errors denote the upper and lower deviations based on the propagated photometric uncertainties, and assuming a distance and reddening uncertainty of 200pc, and 0.2mag. -------------------------------------------------------------------------------- Acknowledgements: Venu Kalari, venu.kalari(at)noirlab.edu ================================================================================ (End) Patricia Vannier [CDS] 25-Nov-2021