J/ApJ/914/28 G305 star-forming region. II. Irregular var. stars (Medina+, 2021)
The G305 star-forming region.
II. Irregular variable stars.
Medina N., Borissova J., Kurtev R., Alonso-Garcia J., Roman-Zuniga C.G.,
Bayo A., Kounkel M., Roman-Lopes A., Lucas P.W., Covey K.R., Forster F.,
Minniti D., Adame L., Hernandez J.
<Astrophys. J., 914, 28 (2021)>
=2021ApJ...914...28M 2021ApJ...914...28M
ADC_Keywords: Star Forming Region; Stars, variable; YSOs; Photometry, infrared;
Spectra, infrared
Keywords: Pre-main sequence stars ; Infrared astronomy ;
Irregular variable stars ; Open star clusters
Abstract:
We present a catalog of 167 newly discovered, irregular variables
spanning a ∼7deg2 area that encompasses the G305 star-forming
complex, one of the most luminous giant HII regions in the Galaxy. We
aim to unveil and characterize the young stellar object (YSO)
population of the region by analyzing the Ks-band variability and JHKs
infrared colors from the VISTA Variables in the Via Lactea survey.
Additionally, SDSS-IV APOGEE-2 infrared spectra of selected objects
are analyzed. The sample shows relatively high amplitudes
(0.661mag<ΔKS<3.521mag). Most of them resemble sources with
outbursts with amplitude >1mag and duration longer than a few days,
typically at least a year, known as eruptive variables. About 60% are
likely to be Class II/flat/I objects. This is also confirmed by the
spectral index α when available. From the analysis of APOGEE-2
near-infrared spectra of sources in the region, another 122 stars are
classified as YSOs and display some infrared variability. The measured
effective temperature Teff peak is around 4000 K, and they are
slightly supersolar in metal abundance. The modal radial velocity is
approximately -41km/s. Combining available catalogs of YSOs in the
region with our data, we investigate the spatial distributions of 700
YSOs. They are clearly concentrated within the central cavity formed
by the massive clusters Danks 1 and 2. The calculated surface density
for the entire catalog is 0.025 YSOs pc-2, while the central cavity
contains 10 times more objects per area (0.238 YSOs pc-2).
Description:
This is the second paper of our series on the G305 star-forming
region. In Borissova+ (2019AJ....158...46B 2019AJ....158...46B), we used moderately high
resolution spectroscopy obtained with the Apache Point Observatory
Galaxy Evolution Experiment-2 (APOGEE-2) spectrograph to study the
massive stellar content in the area.
In this paper, we report a new study of the YSO population in the
region. A variability search in the NIR KS bandpass is performed.
Sources are identified as variable stars by their variability indices
via analysis of the time-series data of the entire VVV survey period
between 2010 and 2015. Spectroscopic follow-up of a sample is
performed with the APOGEE-2 spectrograph. Finally, we collated
catalogs of YSOs and candidate YSOs from the literature in order to
investigate their spatial distribution.
The VVV is an ESO NIR public survey (Saito+ 2012, II/337) that uses
the 4m VISTA telescope at Cerro Paranal Observatory, Chile. It was
designed for mapping 562deg2 in the Galactic bulge and the southern
disk in five NIR broadband filters, Z, Y, J, H, and KS, with a time
coverage spanning over 5yr, between 2010 and mid-2015. The
observations were performed with the VIRCAM NIR camera. See Section 2.
APOGEE-2 is a second-generation multiobject NIR spectrograph, mounted
on the 2.5m du Pont Telescope at Las Campanas Observatory, Chile. The
observed spectral range is 1.51-1.70um, with resolution R=22500.
The APOGEE-2 observations of G305 were carried out on 2017 April 14
(under external CNTAC program No. CN2016B90), with 1hr exposure time.
In total, 127 stars were observed with APOGEE-2.
See Section 7.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
13 13 00 -62 42 00 G305 = NAME G305 Complex
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 341 196 Parameters of the VVV variables considered
in this work
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See also:
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
II/337 : VISTA Variables in the Via Lactea Survey DR1 (Saito+, 2012)
II/328 : AllWISE Data Release (Cutri+ 2013)
II/348 : VISTA Variable in the Via Lactea Survey DR2 (Minniti+, 2017)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
II/364 : VIRAC. The VVV Infrared Astrometric Catalogue (Smith+, 2019)
IX/57 : The Chandra Source Catalog (CSC), Release 2.0 (Evans+, 2019)
II/360 : Gaia DR2 x AllWISE catalogue (Marton+, 2019)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
J/AJ/121/3160 : JHK photometry near the Trapezium region (Carpenter+, 2001)
J/A+A/432/737 : General Cat. of 6.7GHz Methanol Masers (Pestalozzi+, 2005)
J/A+A/492/277 : Analysis of Collinder 69 stars with VOSA (Bayo+, 2008)
J/AJ/136/2391 : GLIMPSE Extended Green Objects catalog (Cyganowski+, 2008)
J/AJ/136/2413 : Galactic midplane Spitzer red sources (Robitaille+, 2008)
J/A+A/532/A131 : New Galactic star clusters in VVV survey (Borissova+, 2011)
J/ApJS/196/9 : 95GHz methanol maser survey toward GLIMPSE EGOs (Chen+, 2011)
J/AJ/143/70 : Differential reddening in MW globulars (Alonso-Garcia+, 2012)
J/AJ/147/82 : Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014)
J/AJ/149/64 : MIPSGAL 24µm point source catalog (Gutermuth+, 2015)
J/AJ/150/132 : JHK photometry of 1203 variables in ONC (Rice+, 2015)
J/AJ/150/145 : YSOVAR infrared photometry in GGD12-15 (Wolk+, 2015)
J/AJ/151/144 : ASPCAP weights for APOGEE chemical elements (Garcia+, 2016)
J/A+A/591/A149 : Hi-GAL. inner Milky Way: +68≥l≥70 (Molinari+, 2016)
J/MNRAS/465/3011 : VVV high amplitude NIR var. stars (Contreras Pena+, 2017)
J/MNRAS/464/1247 : VVV high PM stars. I. Ks≤13.5 stars (Kurtev+, 2017)
J/ApJ/864/11 : The VVV Variables (V4) catalog (Medina+, 2018)
J/A+A/619/A41 : Photometric variability of massive YSOs (Teixeira+, 2018)
J/A+A/623/A110 : Gaia DR2. Variable stars in CMD (Gaia Collaboration+, 2019)
J/A+A/647/A169 : VVV survey near-infrared colour catalogue (Herpich+, 2021)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- OID Object Identifier (TileID: d045, d046, d083 or
d084 and vNN within tile with numbers
from v1 to v66)
10- 19 F10.6 deg RAdeg [194/200.51] Right Ascension (J2000)
21- 30 F10.6 deg DEdeg [-64/-61.6] Declination (J2000)
32- 42 F11.7 deg GLON [303.4/306.4] Galactic longitude
44- 53 F10.7 deg GLAT [-1.16/1.11] Galactic latitude
55- 60 F6.3 mag Ksmag [11.29/16.5] Mean Ks-band magnitude of variable
62- 66 F5.3 mag e_Ksmag [0.01/0.07] Standard deviation of
Ksmag observations
68- 69 I2 --- n_Ksmag [22/69] Number of Ks observations
71- 75 F5.3 --- DelKs [0.66/3.53] Total amplitude variability
parameter (1)
77- 81 F5.3 --- eta [0.049/1.06] η index variability
parameter (1)
83- 86 A4 --- TileID VVV Tile identifier (d045, d046, d083 or d084)
88- 93 F6.3 mag Ksmag0 [11.78/17.37]? Ksmag on MJD=55264
95- 99 F5.3 mag e_Ksmag0 [0.016/0.1]? Uncertainty in Ksmag on MJD=55264
101-106 F6.3 mag Jmag [12.81/19.7]? Mean J-band magnitude
108-112 F5.3 mag e_Jmag [0.013/0.22]? Uncertainty in Jmag
114-119 F6.3 mag Hmag [12.61/18.86]? Mean H-band magnitude
121-125 F5.3 mag e_Hmag [0.01/0.94]? Uncertainty in Hmag
127-133 F7.4 mag J-H [-0.05/3.73]? Mean J-H color index
135-141 F7.4 mag H-Ks [-0.15/4]? Mean H-Ks color index
143 A1 --- Class Optical Class "F, T, or P" (2)
147-155 A9 --- VClass Variable Class (3)
157-192 A36 --- Comm Comments (4)
194-211 A18 --- Ref Reference (5)
213-218 F6.3 mag [3.6] [7.7/14.94]? GLIMPSE IRAC 3.6um band magnitude
220-224 F5.3 mag e_[3.6] [0.028/0.4]? Uncertainty in [3.6]
226-231 F6.3 mag [4.5] [6.89/14.5]? GLIMPSE IRAC 4.5um band magnitude
233-237 F5.3 mag e_[4.5] [0.029/0.3]? Uncertainty in [4.5]
239-244 F6.3 mag [5.8] [4/13.22]? GLIMPSE IRAC 5.8um band magnitude
246-250 F5.3 mag e_[5.8] [0.019/0.4]? Uncertainty in [5.8]
252-257 F6.3 mag [8.0] [4.2/12.74]? GLIMPSE IRAC 8.0um band magnitude
259-263 F5.3 mag e_[8.0] [0.016/0.4]? Uncertainty in [8.0]
265-268 F4.2 mag [24] [0.5/9.31]? MIPSGAL 24um band magnitude
270-273 F4.2 mag e_[24] [0.02/0.4]? Uncertainty in [24]
275-280 F6.3 mag W1mag [8.36/15.1]? ALLWISE W1-band (3.4um) magnitude
282-286 F5.3 mag e_W1mag [0.02/0.31]? Uncertainty in W1mag
288-293 F6.3 mag W2mag [5.036/13.75]? ALLWISE W2-band (4.6um) magnitude
295-299 F5.3 mag e_W2mag [0.017/0.2]? Uncertainty in W2mag
301-306 F6.3 mag W3mag [2.34/12.5]? ALLWISE W3-band (12um) magnitude
308-312 F5.3 mag e_W3mag [0.012/0.5]? Uncertainty in W3mag
314-319 F6.3 mag W4mag [-0.68/9.05]? ALLWISE W4-band (22um) magnitude
321-325 F5.3 mag e_W4mag [0.004/0.43]? Uncertainty in W4mag
327-331 F5.2 --- alpha [-3.56/3.31]? IR spectral index, α (6)
333-341 A9 --- AClass Classification from α slope (7)
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Note (1): ΔKs and η variability parameters as defined in
Medina+ (2018, J/ApJ/864/11)
Note (2): Class as follows:
F = We define the region between the reddening vectors of MS stars and giant
stars as the F-region. These objects are considered to have at most a
small NIR excess, likely corresponding to Class III or Class II YSOs.
Some of these could be foreground or background sources.
T = The T-region is defined to be between the projected reddening vector
from the end of the T Tauri locus (Meyer+ 1997AJ....114..288M 1997AJ....114..288M) and the
MS dwarf reddening vector. Sources located here are considered to have
a substantial NIR excess and are likely to be Class II objects, also
known as T Tauri stars. Some Herbig Ae/Be sources with small NIR
excess are also considered to lie in the T-region.
P = The region to the right of the reddening vector extending from the end of
the T Tauri locus is called the P-region. The projected sources in
this region are more likely Class I objects, sources with thermal
emission from the circumstellar envelope, and protostar-like and/or
Herbig Ae/Be objects.
See Section 5.
Note (3): Classes of aperiodic VVVKSlight curves of YSOs as defined in
Medina+ (2018, J/ApJ/864/11); see Section 4.
Classes as follows:
Eruptive = Shows sources with outbursts with amplitude >1mag and duration
longer than a few days and typically at least a year;
47 occurrences
Unclass = Sources without a clear trend; 45 occurrences
STV = Short Timescale Variable: Sources where the time series is
dominated by fast variability on timescales from days to weeks.
They also can show brief bursts in brightness on timescales
of weeks; 37 occurrences
Dipper = Shows one or more fading events on a timescale of months or
years, followed by a return to normal brightness; 25 occurrences
LAE = Low Amplitude Eruptive: Sources that present outbursts with
amplitude lower than 1mag and duration typically longer
than a year; 24 occurrences
Fader = The light curve is best described by a monotonic decrease in
brightness on a timescale t>1yr, sometimes following a
constant brightness initially; 18 occurrences
Note (4): Comments, including information about: close neighbors, groups of
stars, inside a molecular cloud, FIRE spectrum, etc.
Note (5): References for other catalogs (see Section 3) as follows:
Robitaille = Robitaille et al. 2008, J/AJ/136/2413
Faimali = Faimali, A. D. 2013PhDT.......185F 2013PhDT.......185F
Borissova2016 = Borissova et al. 2016AJ....152...74B 2016AJ....152...74B
HAWORTH2013 = The source d083_v29 is identified as an outflow candidate
in Chen+ (2011, J/ApJS/196/9) and
Cyganowski+ (2008, J/AJ/136/2391).
NovaCen2005 = the source d084_v41 is a well-known nova called
NOVA Cen 2005 or V1047 Cen (Samus 2005IAUC.8596....2S 2005IAUC.8596....2S)
Pestalozzi2005 = Pestalozzi et al. 2005, J/A+A/432/737
Note (6): Infrared spectral index, α, from equations given in
Kuhn+ (2021, J/ApJS/254/33) and based on the longest wavelength data
available.
Note (7): Subdivision into YSO classes is made using the limits at
α=-1.6, -0.3, and 0.3 (Greene+ 1994ApJ...434..614G 1994ApJ...434..614G).
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History:
From electronic version of the journal
References:
Borissova et al. Paper I. 2019AJ....158...46B 2019AJ....158...46B
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Dec-2022