J/AJ/153/188 Spectroscopy of the foreground population in Orion A (Fang+, 2017)
NGC 1980 is not a foreground population of Orion: spectroscopic survey of young
stars with low extinction in Orion A.
Fang M., Kim J.S., Pascucci I., Apai D., Zhang L., Sicilia-Aguilar A.,
Alonso-Martinez M., Eiroa C., Wang H.
<Astron. J., 153, 188 (2017)>
=2017AJ....153..188F 2017AJ....153..188F (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; YSOs ; Accretion ; Spectroscopy ;
Spectral types ; Equivalent widths ; Extinction ; Stars, masses ;
Stars, ages
Keywords: accretion, accretion disks - protoplanetary disks -
stars: pre-main sequence
Abstract:
We perform a spectroscopic survey of the foreground population in
Orion A with MMT/Hectospec. We use these data, along with archival
spectroscopic data and photometric data, to derive spectral types,
extinction values, and masses for 691 stars. Using the Spitzer Space
Telescope data, we characterize the disk properties of these sources.
We identify 37 new transition disk (TD) objects, 1 globally depleted
disk candidate, and 7 probable young debris disks. We discover an
object with a mass of less than 0.018-0.030 M☉, which harbors a
flaring disk. Using the Hα emission line, we characterize the
accretion activity of the sources with disks, and confirm that the
fraction of accreting TDs is lower than that of optically thick disks
(46%±7% versus 73%±9%, respectively). Using kinematic data from
the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of the
Young Nebulous Clusters program (IN-SYNC), we confirm that the
foreground population shows similar kinematics to their local
molecular clouds and other young stars in the same regions. Using the
isochronal ages, we find that the foreground population has a median
age of around 1-2 Myr, which is similar to that of other young stars
in Orion A. Therefore, our results argue against the presence of a
large and old foreground cluster in front of Orion A.
Description:
We performed a low-resolution spectroscopic survey of the stellar
population in NGC 1980 with the Hectospec multi-object spectrograph,
capable of taking a maximum of 300 spectra simultaneously. We used the
270 groove/mm grating and obtained spectra in the 3700-9000Å
range with a spectral resolution of ∼5Å. The data were taken in
2016 February.
In Table 4, we list the young stars with X-Shooter spectra. These
sources are mainly from the η Cha cluster, the TW Hydra Association,
the Lupus star-forming region, the σ Ori cluster, and the Cha I
star-forming region. We extract the spectra of these sources from the
X-Shooter phase III data archive.
Objects:
-----------------------------------------------------------
RA (ICRS) DE Designation(s)
-----------------------------------------------------------
05 35 24 -05 54.9 NGC 1980 = NAME Lower Sword
05 35.3 -05 23 Orion = NAME Orion Complex
05 35 17.3 -05 23 28 Orion A = M 42
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 118 85 The parameters for young stars with X-Shooter
spectra
table6.dat 101 691 Stellar properties for the YSOs
refs.dat 64 43 References
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See also:
J/A+AS/123/329 : New weak-line T Tauri stars in Lupus (Krautter+ 1997)
J/ApJ/602/816 : Chamaeleon I star-forming region census (Luhman, 2004)
J/AJ/130/1733 : Optical spectroscopy of ρ Oph stars (Wilking+, 2005)
J/A+A/460/695 : Search for Associations Containing Young stars (Torres+, 2006)
J/AJ/132/866 : New M dwarfs in solar neighborhood (Riaz+, 2006)
J/AJ/133/2524 : Spectra of young nearby stars (White+, 2007)
J/ApJ/667/308 : Weak-line T Tauri in Spitzer c2d Survey. II. (Cieza+, 2007)
J/A+A/480/735 : Young local stellar associations (Fernandez+, 2008)
J/A+A/488/167 : Low-mass stars in σ Ori and λ Ori (Sacco+, 2008)
J/A+A/500/1045 : Cool stars and brown dwarfs in Lupus clouds (Comeron+, 2009)
J/A+A/504/461 : YSOs in L1630N and L1641 (Fang+, 2009)
J/ApJ/691/672 : Spectrocopy of YSOs in Serpens molecular cloud
(Oliveira+, 2009)
J/ApJ/712/925 : Transition circumstellar disks in Ophiuchus (Cieza+, 2010)
J/ApJ/724/835 : The Spitzer c2d survey of WTTSs. III. (Wahhaj+, 2010)
J/A+A/548/A56 : X-shooter spectra of 12 young stellar objects
(Rigliaco+, 2012)
J/AJ/144/192 : Spitzer survey of Orion A and B. I. YSO catalog
(Megeath+, 2012)
J/ApJ/745/119 : Close companions to young stars. I. ChaI & Tau
(Nguyen+, 2012)
J/ApJ/749/79 : Transition disks. II. Southern MoC (Romero+, 2012)
J/A+A/551/A107 : X-shooter spectra of 24 young stellar objects (Manara+, 2013)
J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013)
J/A+A/561/A2 : 36 accreting YSOs emission lines (Alcala+, 2014)
J/A+A/602/A33 : X-Shooter spectroscopy of YSOs in Lupus (Frasca+, 2017)
J/A+A/605/A86 : Pre-main sequence stars VLT/X-Shooter spectra (Manara+, 2017)
J/AJ/154/29 : Observation of 148 young stars toward NGC 1980
(Kounkel+, 2017)
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/85] Running number identifier
4- 25 A22 --- Name Star Name
27- 28 I2 h RAh Hour of Right Ascension (J2000)
30- 31 I2 min RAm Minute of Right Ascension (J2000)
33- 38 F6.3 s RAs Second of Right Ascension (J2000)
40 A1 --- DE- Sign of the Declination (J2000)
41- 42 I2 deg DEd Degree of Declination (J2000)
44- 45 I2 arcmin DEm Arcminute of Declination (J2000)
47- 51 F5.2 arcsec DEs Arcsecond of Declination (J2000)
53- 66 A14 --- SpT-Lit Literature spectral type(s)
68- 78 A11 --- r_SpT-Lit Reference(s) for SpT-Lit
80- 84 A5 --- SpT Adopted spectral type
86- 94 A9 --- r_SpT Reference for SpT
96-101 F6.1 0.1nm EW(Ha) [-222.5/1.3] Hα equivalent width (Å)
103 A1 --- l_Lacc/L* [<] Limit flag on Lacc/L*
104-109 F6.4 --- Lacc/L* [0.003/0.096]? Accretion to stellar luminosity
ratio
111 A1 --- Acc [Y/N] Accreting? (Y=Yes, N=No)
113-115 F3.1 mag Av [0/6.2] Line of sight extinction
117-118 I2 --- Ref [14/43]? Reference for accretion luminosity
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/691] Running number identifier
5- 6 I2 h RAh Hour of Right Ascension (J2000)
8- 9 I2 min RAm Minute of Right Ascension (J2000)
11- 15 F5.2 s RAs Second of Right Ascension (J2000)
17 A1 --- DE- Sign of the Declination (J2000)
18- 19 I2 deg DEd Degree of Declination (J2000)
21- 22 I2 arcmin DEm Arcminute of Declination (J2000)
24- 27 F4.1 arcsec DEs Arcsecond of Declination (J2000)
29- 32 A4 --- SpT MK spectral type (1)
34- 38 F5.3 Lsun Lum [0.019/1.039] Luminosity
40- 42 F3.1 mag Av [0/2.8] Visual extinction
44- 48 F5.3 Msun Mass [0.018/0.67] Stellar mass
50 A1 --- l_Age [<] Limit flag on Age
51- 54 F4.1 Myr Age [0.5/22.9] Stellar age
55 A1 --- f_Age [?] Uncertainty flag on Age
57- 60 F4.2 0.1nm EW-Li1 [0.07/1.2]? First Li 6708Å equivalent width
(Å)
62- 65 F4.2 0.1nm EW-Li2 [0.12/0.62]? Second Li 6708Å equivalent
width (Å)
67- 72 F6.1 0.1nm EW-Ha [-249.8/0]? Hα equivalent width (Å)
74- 78 F5.2 --- alpha1 [-3.12/0.32]? SED slope in spectral range
3.6-8µm
80- 84 F5.2 --- alpha2 [-2.46/0.13]? SED slope in spectral range
3.6-24µm
86 A1 --- TTS [CW] T Tauri type (2)
88- 89 A2 --- Disk Disk population (3)
91-101 A11 --- Crit Sample selection criterion (4)
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Note (1): Spectral types of the sources are obtained using the relations between
spectral types and the strengths of spectral features constructed in
Appendix A, and kept to the 1/10th subtype accuracy.
Note (2): T-Tauri type based on Hα equivalent width according to the
spectral type based criteria from Fang et al. (2009, J/A+A/504/461):
W = Weak-lined T-Tauri;
C = Classical T-Tauri.
Note (3): Disk population as follows:
? = Disk presence uncertain;
DB = Debris disk;
N = There is no disk;
TD = Transition disk;
Y = Yes, there is a disk.
Note (4): Criterion as follows:
IRE = Infrared Excess;
Li = Lithium absorption;
Na = Gravity sensitive sodium lines;
X = X-ray emission.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref [1/43] Reference number
4- 22 A19 --- BibCode BibCode
24- 44 A21 --- Aut Author's name
46- 64 A19 --- Com Comments
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 04-May-2018