J/ApJ/717/1067 Triggered star formation in SFO 38 (Choudhury+, 2010) ================================================================================ Triggered star formation and young stellar population in bright-rimmed cloud SFO 38. Choudhury R., Mookerjea B., Bhatt H.C. =2010ApJ...717.1067C ================================================================================ ADC_Keywords: Photometry, infrared ; Photometry, UBVRI ; YSOs ; H II regions Stars, pre-main sequence ; Spectral types Keywords: H II regions - ISM: clouds - stars: pre-main sequence - ISM: individual objects (SFO 38, IC 1396) - stars: low-mass Abstract: We have investigated the young stellar population in and around SFO 38, one of the massive globules located in the northern part of the Galactic HII region IC 1396, using the Spitzer IRAC and MIPS observations (3.6-24um), and followed up with ground-based optical photometric and spectroscopic observations. Based on the IRAC and MIPS colors and H{alpha} emission, we identify ~45 young stellar objects (Classes 0/I/II) and 13 probable pre-main-sequence candidates. We derive the spectral types (mostly K- and M-type stars), effective temperatures, and individual extinction of the relatively bright and optically visible Class II objects. Using the width of the H{alpha} emission line measured at 10% peak intensity, we derive the mass accretion rates of individual objects to be between 10^-10^ and 10^-8^M_{sun}_/yr. Description: We have extracted IRAC (3.6, 4.5, 5.8, and 8um) and MIPS (24 and 70um) observations from the Spitzer Space Observatory archive (Program ID 30050: Star Formation in Bright Rimmed Clouds by Fazio et al. 2006sptz.prop30050F). SFO 38 was observed on 2009 July 17, August 23, and September 15 using Bessell's broadband filters VR, BVI, and BI, respectively, and on 2008 November 4 using the narrowband H{alpha} (900s) with the Himalayan Faint Object Spectrograph Camera (HFOSC) mounted on the 2m Himalayan Chandra Telescope (HCT) of the Indian Astronomical Observatory, Hanle. Medium resolution (~7{AA}) spectra were obtained for relatively bright and optically visible YSOs during July-November of both 2008 and 2009 in the wavelength range (5200-9200{AA}) with the HFOSC mounted on the HCT. Typical exposure time of each spectrum was 3600s. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 159 110 *Results of near- and mid-IR photometry of the mid-infrared sources in SFO 38 table3.dat 60 44 BVRI photometry of MIR sources in SFO 38 table4.dat 85 29 Spectral classification of YSOs -------------------------------------------------------------------------------- Note on table1.dat: Out of the 110 sources identified with Spitzer in SFO 38, 80 were found to have NIR counterparts (in 2MASS, Cat. II/246). However 10 out of the 80 sources with NIR counterparts were found to coincide with the H_2_ knots identified by Beltran et al. (2009, Cat. J/A+A/504/97). -------------------------------------------------------------------------------- See also: II/311 : WISE All-Sky Data Release (Cutri+ 2012) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/MNRAS/415/103 : IPHAS T Tauri candidates in IC 1396 (Barentsen+, 2011) J/A+A/504/97 : JHKs photometry of IC 1396N (Beltran+, 2009) J/MNRAS/396/964 : T Tauri in and around bright-rimmed clouds (Chauhan+, 2009) J/AJ/135/2323 : H{alpha} stars and HH objects near BRCs (Ikeda+, 2008) J/ApJ/654/316 : X-ray sources in IC 1396N (Getman+, 2007) J/AJ/123/2597 : H{alpha} stars and HH objects near BRCs (Ogura+, 2002) J/A+A/309/581 : CO observations of clouds in IC 1396 region (Weikard +,1996) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 A7 --- Name SFO 38 source name (<[CMB2010] MIR-NNN> in Simbad) 8 A1 --- r_Name [ab] JHKs photometry reference if not 2MASS (1) 10- 11 I2 h RAh Hour of right ascension (J2000) 13- 14 I2 min RAm Minute of right ascension (J2000) 16- 20 F5.2 s RAs Second of right ascension (J2000) 22 A1 --- DE- Sign of declination (J2000) 23- 24 I2 deg DEd Degree of declination (J2000) 26- 27 I2 arcmin DEm Arcminute of declination (J2000) 29- 33 F5.2 arcsec DEs Arcsecond of declination (J2000) 35- 39 F5.2 mag Jmag ? 2MASS J-band magnitude 41- 44 F4.2 mag e_Jmag ? Jmag uncertainty 46 A1 --- l_Hmag Limit flag on Hmag 47- 51 F5.2 mag Hmag ? 2MASS H-band magnitude 53- 56 F4.2 mag e_Hmag ? Hmag uncertainty 58- 62 F5.2 mag Ksmag ? 2MASS Ks-band magnitude 64- 67 F4.2 mag e_Ksmag ? Ksmag uncertainty 69- 73 F5.2 mJy F3.6 ? Spitzer/IRAC 3.6um flux density 75- 78 F4.2 mJy e_F3.6 ? F3.6 uncertainty 80- 85 F6.2 mJy F4.5 ? Spitzer/IRAC 4.5um flux density 87- 90 F4.2 mJy e_F4.5 ? F4.5 uncertainty 92- 97 F6.2 mJy F5.8 ? Spitzer/IRAC 5.8um flux density 99-102 F4.2 mJy e_F5.8 ? F5.8 uncertainty 104-109 F6.2 mJy F8.0 ? Spitzer/IRAC 8.0um flux density 111-114 F4.2 mJy e_F8.0 ? F8.0 uncertainty 116-122 F7.2 mJy F24 ? Spitzer/MIPS 24um flux density 124-127 F4.2 mJy e_F24 ? F24 uncertainty 129-134 A6 --- Class Preliminary classification (Trans., III/S, I, II, I/II, 0/I, Galaxy, H_2_) (2) 136-158 A23 --- Comm Comments 159 A1 --- f_Comm [c] c: variable in J/H/Ks -------------------------------------------------------------------------------- Note (1): JHKs photometry reference as follows: a = Nisini et al. 2001A&A...376..553N b = Beltran et al. 2009, Cat. J/A+A/504/97 Note (2): Preliminary classification based on selected color-color plots and other criteria described in Section 3.2. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- Name SFO 38 source name (MIR-NNN mainly) 10- 14 F5.2 mag Bmag ? HCT/HFOSC B-band magnitude 16- 20 F5.3 mag e_Bmag ? Bmag uncertainty 22- 26 F5.2 mag Vmag HCT/HFOSC V-band magnitude 28- 32 F5.3 mag e_Vmag Vmag uncertainty 34- 38 F5.2 mag Rmag HCT/HFOSC R-band magnitude 40- 44 F5.3 mag e_Rmag Rmag uncertainty 46- 50 F5.2 mag Imag HCT/HFOSC I-band magnitude 52- 56 F5.3 mag e_Imag Imag uncertainty 58- 60 A3 --- Var [BVI ] Variability (1) -------------------------------------------------------------------------------- Note (1): We consider a source to be variable if the magnitude difference is >=0.1mag at the two observing epochs (2009 Aug 23 and Sept 15). -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- Name SFO 38 source name (MIR-NNN mainly) 10- 17 A8 --- AName Alternate name (BRC38= <[OSP2002] BRC 38 NN> or GFG= <[GFG2007] NN> in Simbad) 19- 26 A8 "DD/MM/YY" Date Observation date 28- 35 F8.3 0.1nm W H{alpha} equivalent width ({AA}) 37- 38 A2 --- SpT MK spectral type 40 I1 --- e_SpT ? Subtype uncertainty 42- 45 I4 K Teff ? Effective temperature 47- 50 A4 --- Type YSO type (CTTS/WTTS: Classical or Weak TTau) 52- 57 F6.2 km/s Ha ? H{alpha} emission line at 10% of the peak intensity (H{alpha}[10%]) (1) 59- 64 F6.2 [Msun/yr] logdM/dt ? Rate of accretion from H{alpha} emission (1) 66- 70 F5.2 --- alpha ? IRAC slope 72- 75 F4.2 mag E(V-I) ? V-I color index 77- 80 F4.2 mag Av ? Extinction (2) 82- 85 F4.2 mag Erat ? E(V-I)/E(B-V) color index ratio -------------------------------------------------------------------------------- Note (1): Natta et al. (2004A&A...424..603N) showed that H{alpha}[10%]>=200km/s can be used to distinguish the accretors and nonaccretors as well as to derive an approximate estimate of the accretion rate dM/dt_ac_ quantitatively by the following relation: logdM/dt_ac_=-12.89(+/-0.3)+9.7(+/-0.7)x10^-3^H{alpha}[10%] where H{alpha}[10%] is in km/s and dM/dt_ac_ is in M_{sun}_/yr. Note (2): Using the V-I color of a particular spectral type and our optical BVRI observations, we calculated the A_V_ assuming the normal interstellar extinction law as given by Bessell & Brett (1988PASP..100.1134B). The average extinction toward the globule is estimated to be A_V_=2.5mag. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Emmanuelle Perret [CDS] 05-Jun-2012