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J/AJ/154/29    Observation of 148 young stars toward NGC 1980   (Kounkel+, 2017)

Characterizing the stellar population of NGC 1980. Kounkel M., Hartmann L., Calvet N., Megeath T. <Astron. J., 154, 29-29 (2017)> =2017AJ....154...29K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Spectral types ; Equivalent widths Keywords: ISM: individual objects: NGC 1980 - stars: pre-main sequence Abstract: NGC1980 is a young cluster that is located about 0.5° south of the Orion Nebula Cluster (ONC). Recent studies by Bouy et al. and Pillitteri et al. have suggested that NGC1980 contains an older population of stars compared to a much younger ONC, and that it belongs to a foreground population that may be located in front of the Orion A molecular gas by as much as 40pc. In this work, we present low-resolution spectra toward 148 young stars found toward the NGC1980 region. We determine the spectral types of these stars, examine accretion signatures and measure the extinction toward them. We determine that based on these observations, the age of the population of NGC1980 is indistinguishable from L1641, estimated to be ∼3Myr, comparable with the study by Fang et al. Description: We conducted observations using the Inamori-Magellan Areal Camera and Spectrograph (IMACS) on the Magellan Baade telescope. Observations were done using the f/2 camera with the 300 line grism at a blaze angle of 17.5° and slit width of 0.6". In this configuration, the typical resolution is 4Å, and the spectral coverage is approximately 4000-9000Å. We observed four fields toward NGC1980 using the multi-slit mode on 2016 January 7. We targeted 280 sources identified by Bouy et al. 2014 (Cat. J/A+A/564/A29) with r<21mag, of which 212 sources had probabilities of membership (P) greater than 50%. The exposure time was 5*10 minutes per field for the first three fields, and the last field had the exposure time of 8*10 minutes. The weather conditions deteriorated rapidly over the course of the night, therefore, while the first field had the full sensitivity, the last field, even with the increased exposure time, yielded little in terms of the number of sources detected. Partially because of this, we have detected only 148 sources (see Table1). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 88 148 Sources observed toward NGC 1980 with Inamori-Magellan Areal Camera and Spectrograph (IMACS)
See also: II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/ApJ/834/142 : Gould's Belt Distances Survey (GOBELINS). II. (Kounkel+, 2017) J/ApJ/821/8 : Spectroscopic binaries of ONC and NGC2264 (Kounkel+, 2016) J/ApJ/818/59 : IN-SYNC. IV. YSOs in Orion A (Da Rio+, 2016) J/A+A/564/A29 : Optical and near-infrared photometry in Orion A (Bouy+, 2014) J/ApJ/768/99 : X-ray survey of YSOs in Orion A (Pillitteri+, 2013) J/ApJ/764/114 : BVRI photometry of stars in Orion A (Hsu+, 2013) J/ApJ/753/149 : YSOVAR: 6 Orion eclipsing binaries (Morales-Calderon+, 2012) J/AJ/144/192 : Spitzer survey of Orion A and B. I. (Megeath+, 2012) J/ApJ/722/1092 : Optical photometry of the ONC. II. (Da Rio+, 2010) J/ApJS/183/261 : Optical photometry of the ONC (Da Rio+, 2009) J/ApJ/676/1109 : Velocities of stars in the ONC (Furesz+, 2008) J/ApJ/661/1119 : Spectroscopy in the 25 Ori group (Briceno+, 2007) J/AJ/121/1676 : ONC low-mass stars photometry (Rebull+, 2001) J/AJ/119/3026 : Circumstellar disk candidates in Orion (Rebull+, 2000) J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 6 I6 --- B14 [329411/400107] Identifier from Bouy et al. 2014 (Cat. J/A+A/564/A29) 8- 9 I2 h RAh Hour of Right Ascension (J2000) 11- 12 I2 min RAm Minute of Right Ascension (J2000) 14- 18 F5.2 s RAs Second of Right Ascension (J2000) 20 A1 --- DE- Sign of the Declination (J2000) 21- 22 I2 deg DEd Degree of Declination (J2000) 24- 25 I2 arcmin DEm Arcminute of Declination (J2000) 27- 30 F4.1 arcsec DEs Arcsecond of Declination (J2000) 32- 35 A4 --- SpT Spectral type 37- 39 F3.1 --- e_SpT [0.5/5.2] Spectral subtype uncertainty 41 I1 --- f_EWHa [0/3]? Flag on EWHa (0, 1, 2, or 3) (1) 43- 48 F6.1 0.1nm EWHa [-124.2/4.9]? Hα equivalent width (2) 50- 53 F4.1 0.1nm e_EWHa [0/33.2]? Uncertainty in EWHa 55 I1 --- f_EWLi [0/4]? Flag on EWLi (0, 1, 2, or 4) (1) 57 A1 --- l_EWLi [<] Upper limit flag on EWLi 59- 61 F3.1 0.1nm EWLi [0.1/2.1]? Li I 6707Å equivalent width (2) 63- 67 F5.1 --- S/N [1.3/172.8] Spectral Signal-to-Noise/per pixel 69- 72 A4 --- TTS ? Accretion type (WTTS or CTTS) (3) 74- 82 A9 --- Ref ? References (4) 84- 86 F3.1 mag AV [0/3.9]? Visual extinction (AV) 88 I1 --- Field [1/4] Observation field (1, 2, 3, or 4) (5)
Note (1): Line detection flags are defined as follows: 0 = Detection; 1 = No detection with S/N>5; 2 = Line has either fallen onto the chip gap or off the edge of the field; 3 = Poor nebular line subtraction; 4 = Upper limit. Note (2): EWHa, EWLi reported only for sources with S/N>5. Note (3): The T Tauri stars are defined as follows: WTTS = Weak-lined T Tauri Star; CTTS = Classical T Tauri Star. Note (4): Reference codes are defined as follows: 1 = This work; 2 = Pillitteri et al. 2013 (Cat. J/ApJ/768/99); 3 = Hsu et al. 2012 (Cat. J/ApJ/752/59); 4 = Furesz et al. 2008 (Cat. J/ApJ/676/1109); 5 = Megeath et al. 2012 (Cat. J/AJ/144/192); 6 = Morales-Calderon et al. 2012 (Cat. J/ApJ/753/149); 7 = Fang et al. 2017AJ....153..188F. Note (5): We observed four fields toward NGC 1980 using the multi-slit mode on 2016 January 7.
History: From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 29-Sep-2017
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