J/A+A/647/A167 Using H-bump to identify RSGs in NGC6822 (Yang+, 2021)
Evolved massive stars at low-metallicity IV.
Using the 1.6um H-bump to identify red supergiant stars: Case study of NGC 6822.
Yang M., Bonanos A.Z., Jiang B.W., Lam M.I., Gao J., Gavras P.,
Maravelias G., Wang S., Chen X.D., Tramper F., Ren Y., Spetsieri Z.T.
<Astron. Astrophys. 647, A167 (2021)>
=2021A&A...647A.167Y 2021A&A...647A.167Y (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Galaxies, nearby ; Mass loss ;
Stars, late-type ; Stars, supergiant
Keywords: infrared: stars - galaxies: dwarf - stars: late-type -
stars: massive - stars: mass-loss - stars: variables: general
Abstract:
We present a case study in which we used a novel method to identify
red supergiant (RSG) candidates in NGC 6822 based on their 1.6um
H-bump. We collected 32 bands of photometric data for NGC 6822 ranging
from the optical to the mid-infrared (MIR), derived from Gaia, PS1,
LGGS, VHS, UKIRT, IRSF, HAWK-I, Spitzer, and WISE. Using the
theoretical spectra from MARCS, we demonstrate that there is a
prominent difference around 1.6um (H-bump) between targets with
high and low surface gravity (HSG and LSG). Taking advantage of this
feature, we identify efficient color-color diagrams of rzH (r-z versus
z-H) and rzK (r-z versus z-K) to separate HSG (mostly foreground
dwarfs) and LSG targets (mainly background red giant stars, asymptotic
giant branch stars, and RSGs) from crossmatching of optical and
near-infrared (NIR) data. Moreover, synthetic photometry from ATLAS9
gives similar results. We further separated RSG candidates from the
remaining LSG candidates as determined by the H-bump method by using
semi-empirical criteria on NIR color-magnitude diagrams, where both
the theoretic cuts and morphology of the RSG population are
considered. This separation produced 323 RSG candidates. The
simulation of foreground stars with Besancon models also indicates
that our selection criteria are largely free from the contamination of
Galactic giants. In addition to the H-bump method, we used the
traditional BVR method (B-V versus V-R) as a comparison and/or
supplement by applying a slightly aggressive cut to select as many RSG
candidates as possible (358 targets). Furthermore, the Gaia
astrometric solution was used to constrain the sample, where 181 and
193 targets were selected with the H-bump and BVR method,
respectively. The percentages of selected targets in the two methods
are similar at ∼60%, indicating a comparable accuracy of the two
methods. In total, there are 234 RSG candidates after combining
targets from the two methods, and 140 (∼60%) of them are in
common. The final RSG candidates are in the expected locations on the
mid-infrared color-magnitude diagram with [3.6]-[4.5]≲0 and
J-[8.0]∼1.0. The spatial distribution is also coincident with the
far-ultraviolet-selected star formation regions, suggesting that the
selection is reasonable and reliable. We indicate that our method can
also be used to identify other LSG targets, such as red giants and
asymptotic giant branch stars, and it can also be applied to most of
the nearby galaxies by using recent large-scale ground-based surveys.
Future ground- and space-based facilities may promote its application
beyond the Local Group.
Description:
Photometric catalogues of NGC 6822 from PS1, Gaia, LGGS, UKIRT, VHS,
IRSF, HAWK-I, Spitzer, and WISE. We also identified 234 RSG
candidates. The catalogues mainly provide positions and photometry.
Astrometry is also provided by Gaia for some targets.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
rsg.dat 648 234 Catalog of 234 identified RSG candidates (table 2)
gaia.dat 113 22826 Gaia photometric catalog (table A2)
ps1.dat 163 23977 PS1 photometric catalog (table A1)
lggs.dat 104 43584 LGGS photometric catalog (table A3)
ukirt.dat 65 25848 UKIRT photometric catalog (table A4)
vhs.dat 51 16903 VHS photometric catalog (table A5)
irsf.dat 65 5657 IRSF photometric catalog (table A6)
hawki.dat 51 4318 HAWK-I photometric catalog ((table A7)
spitzer.dat 113 28824 Spitzer photometric catalog (table A8)
wise.dat 107 7464 WISE photometric catalog (table A9)
--------------------------------------------------------------------------------
See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/352 : The VISTA Hemisphere Survey (VHS) catalog (McMahon+, 2013)
II/288 : IRSF Magellanic Clouds Point Source Catalog (Kato+ 2007)
II/295 : Spitzer IRAC survey of the galactic center (Ramirez+, 2008)
II/332 : c2d Spitzer final data release (DR4) (Evans+, 2003)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
II/328 : AllWISE Data Release (Cutri+ 2013)
Byte-by-byte Description of file: rsg.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (ICRS) at Ep=2015.5
13- 23 F11.6 deg DEdeg Declination (ICRS) at Ep=2015.5
25- 32 F8.3 mas PlxG ? Gaia parallax
34- 41 F8.3 mas e_PlxG ? Gaia parallax error
43- 50 F8.3 mas/yr pmRAG ? Gaia proper motion along RA, pmRA*cosDE
52- 59 F8.3 mas/yr e_pmRAG ? Gaia proper motion error along RA
61- 68 F8.3 mas/yr pmDEG ? Gaia proper motion along DE
70- 77 F8.3 mas/yr e_pmDEG ? Gaia proper motion error along DE
79- 86 F8.3 mag Gmag Gaia G-band mean magnitude
88- 95 F8.3 mag BPmag ? Gaia BP-band mean magnitude
97-104 F8.3 mag RPmag ? Gaia RP-band mean magnitude
106-113 F8.3 --- RUWE ? Gaia Renormalised unit weight error
115-120 F6.3 mag gmagPS1 ? PS1 g-band magnitude
122-127 F6.3 mag e_gmagPS1 ? PS1 g-band magnitude error
129-134 F6.3 mag s_gmagPS1 ? PS1 g-band standard deviation
136-141 F6.3 mag AmpgPS1 ? PS1 g-band amplitude
143-148 F6.3 mag rmagPS1 ? PS1 r-band magnitude
150-155 F6.3 mag e_rmagPS1 ? PS1 r-band magnitude error
157-162 F6.3 mag s_rmagPS1 ? PS1 r-band standard deviation
164-169 F6.3 mag AmprPS1 ? PS1 r-band amplitude
171-176 F6.3 mag imagPS1 ? PS1 i-band magnitude
178-183 F6.3 mag e_imagPS1 ? PS1 i-band magnitude error
185-190 F6.3 mag s_imagPS1 ? PS1 i-band standard deviation
192-197 F6.3 mag AmpiPS1 ? PS1 i-band amplitude
199-204 F6.3 mag zmagPS1 ? PS1 z-band magnitude
206-211 F6.3 mag e_zmagPS1 ? PS1 z-band magnitude error
213-218 F6.3 mag s_zmagPS1 ? PS1 z-band standard deviation
220-225 F6.3 mag AmpzPS1 ? PS1 z-band amplitude
227-232 F6.3 mag ymagPS1 ? PS1 y-band magnitude
234-239 F6.3 mag e_ymagPS1 ? PS1 y-band magnitude error
241-246 F6.3 mag s_ymagPS1 ? PS1 y-band standard deviation
248-253 F6.3 mag AmpyPS1 ? PS1 y-band amplitude
255-260 F6.3 mag VmagLGGS ? LGGS V-band magnitude
262-267 F6.3 mag e_VmagLGGS ? LGGS V-band magnitude error
269-274 F6.3 mag B-VLGGS ? LGGS B-V color
276-281 F6.3 mag e_B-VLGGS ? Error in LGGS B-V color
283-288 F6.3 mag U-BLGGS ? LGGS U-B color
290-295 F6.3 mag e_U-BLGGS ? Error in LGGS U-B color
297-302 F6.3 mag V-RLGGS ? LGGS V-R color
304-309 F6.3 mag e_V-RLGGS ? Error in LGGS V-R color
311-316 F6.3 mag R-ILGGS ? LGGS R-I color
318-323 F6.3 mag e_R-ILGGS ? Error in LGGS R-I color
325-334 A10 --- SpTypeILGGS ? LGGS MK Spectral Type
336-341 F6.3 mag JmagUKIRT ? UKIRT J-band magnitude
343-348 F6.3 mag e_JmagUKIRT ? UKIRT J-band magnitude error
350-355 F6.3 mag HmagUKIRT ? UKIRT H-band magnitude
357-362 F6.3 mag e_HmagUKIRT ? UKIRT H-band magnitude error
364-369 F6.3 mag KmagUKIRT ? UKIRT K-band magnitude
371-376 F6.3 mag e_KmagUKIRT ? UKIRT K-band magnitude error
378-383 F6.3 mag JmagVHS ? VHS J-band magnitude
385-390 F6.3 mag e_JmagVHS ? VHS J-band magnitude error
392-397 F6.3 mag KsmagVHS ? VHS Ks-band magnitude
399-404 F6.3 mag e_KsmagVHS ? VHS Ks-band magnitude error
406-411 F6.3 mag JmagIRSF ? IRSF J-band magnitude
413-418 F6.3 mag s_JmagIRSF ? IRSF J-band standard deviation
420-425 F6.3 mag HmagIRSF ? IRSF H-band magnitude
427-432 F6.3 mag s_HmagIRSF ? IRSF H-band standard deviation
434-439 F6.3 mag KsmagIRSF ? IRSF Ks-band magnitude
441-446 F6.3 mag s_KsmagIRSF ? IRSF Ks-band standard deviation
448-453 F6.3 mag JmagHAWKI ? HAWK-I J-band magnitude
455-460 F6.3 mag e_JmagHAWKI ? HAWK-I J-band magnitude error
462-467 F6.3 mag KsmagHAWKI ? HAWK-I Ks-band magnitude
469-474 F6.3 mag e_KsmagHAWKI ? HAWK-I Ks-band magnitude error
476-480 F5.2 mag IRAC1 ? Spitzer IRAC1-band magnitude
482-486 F5.2 mag e_IRAC1 ? Spitzer IRAC1-band magnitude error
488-492 F5.2 mag dIRAC1 ? Difference between the PSF and aperture
photometry magnitude in Spitzer IRAC1-band
494-498 F5.2 mag IRAC2 ? Spitzer IRAC2-band magnitude
500-504 F5.2 mag e_IRAC2 ? Spitzer IRAC2-band magnitude error
506-510 F5.2 mag dIRAC2 ? Difference between the PSF and aperture
photometry magnitude in Spitzer IRAC2-band
512 A1 --- l_IRAC3 3-sigma upper limit for Spitzer
IRAC3-band magnitude
514-518 F5.2 mag IRAC3 ? Spitzer IRAC3-band magnitude
520-524 F5.2 mag e_IRAC3 ? Spitzer IRAC3-band magnitude error
526-530 F5.2 mag dIRAC3 ? Difference between the PSF and aperture
photometry magnitude in Spitzer IRAC3-band
532 A1 --- l_IRAC4 ? 3-sigma upper limit for Spitzer
IRAC4-band magnitude
534-538 F5.2 mag IRAC4 ? Spitzer IRAC4-band magnitude
540-544 F5.2 mag e_IRAC4 ? Spitzer IRAC4-band magnitude error
546-550 F5.2 mag dIRAC4 ? Difference between the PSF and aperture
photometry magnitude in Spitzer IRAC4-band
552 A1 --- l_MIPS24 ? 3-sigma upper limit for
Spitzer MIPS24-band magnitude
554-558 F5.2 mag MIPS24 ? Spitzer MIPS24-band magnitude
560-564 F5.2 mag e_MIPS24 ? Spitzer MIPS24-band magnitude error
566-571 F6.3 mag WISE1 ? ALLWISE WISE1-band magnitude
573-578 F6.3 mag e_WISE1 ? ALLWISE WISE1-band magnitude error
580-585 F6.3 --- SNRWISE1 ? ALLWISE WISE1-band SNR
587-592 F6.3 mag WISE2 ? ALLWISE WISE2-band magnitude
594-599 F6.3 mag e_WISE2 ? ALLWISE WISE2-band magnitude error
601-606 F6.3 --- SNRWISE2 ? ALLWISE WISE2-band SNR
608-613 F6.3 mag WISE3 ? ALLWISE WISE3-band magnitude
615-620 F6.3 mag e_WISE3 ? ALLWISE WISE3-band magnitude error
622-627 F6.3 --- SNRWISE3 ? ALLWISE WISE3-band SNR
629-634 F6.3 mag WISE4 ? ALLWISE WISE4-band magnitude
636-641 F6.3 mag e_WISE4 ? ALLWISE WISE4-band magnitude error
643-648 F6.3 --- SNRWISE4 ? ALLWISE WISE4-band SNR
--------------------------------------------------------------------------------
Byte-by-byte Description of file: gaia.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (ICRS) at Ep=2015.5
13- 23 F11.6 deg DEdeg Declination (ICRS) at Ep=2015.5
25- 32 F8.3 mas PlxG ? Gaia parallax
34- 41 F8.3 mas e_PlxG ? Gaia parallax error
43- 50 F8.3 mas/yr pmRAG ? Gaia proper motion along RA, pmRA*cosDE
52- 59 F8.3 mas/yr e_pmRAG ? Gaia proper motion error along RA
61- 68 F8.3 mas/yr pmDEG ? Gaia proper motion along DE
70- 77 F8.3 mas/yr e_pmDEG ? Gaia proper motion error along DE
79- 86 F8.3 mag Gmag Gaia G-band mean magnitude
88- 95 F8.3 mag BPmag ? Gaia BP-band mean magnitude
97-104 F8.3 mag RPmag ? Gaia RP-band mean magnitude
106-113 F8.3 --- RUWE ? Gaia Renormalised unit weight error
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ps1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (J2000)
13- 23 F11.6 deg DEdeg Declination (J2000)
25- 30 F6.3 mag gmagPS1 PS1 g-band magnitude
32- 37 F6.3 mag e_gmagPS1 ? PS1 g-band magnitude error
39- 44 F6.3 mag s_gmagPS1 ? PS1 g-band standard deviation
46- 51 F6.3 mag AmpgPS1 ? PS1 g-band amplitude
53- 58 F6.3 mag rmagPS1 PS1 r-band magnitude
60- 65 F6.3 mag e_rmagPS1 ? PS1 r-band magnitude error
67- 72 F6.3 mag s_rmagPS1 ? PS1 r-band standard deviation
74- 79 F6.3 mag AmprPS1 ? PS1 r-band amplitude
81- 86 F6.3 mag imagPS1 PS1 i-band magnitude
88- 93 F6.3 mag e_imagPS1 ? PS1 i-band magnitude error
95-100 F6.3 mag s_imagPS1 ? PS1 i-band standard deviation
102-107 F6.3 mag AmpiPS1 ? PS1 i-band amplitude
109-114 F6.3 mag zmagPS1 PS1 z-band magnitude
116-121 F6.3 mag e_zmagPS1 ? PS1 z-band magnitude error
123-128 F6.3 mag s_zmagPS1 ? PS1 z-band standard deviation
130-135 F6.3 mag AmpzPS1 ? PS1 z-band amplitude
137-142 F6.3 mag ymagPS1 ? PS1 y-band magnitude
144-149 F6.3 mag e_ymagPS1 ? PS1 y-band magnitude error
151-156 F6.3 mag s_ymagPS1 ? PS1 y-band standard deviation
158-163 F6.3 mag AmpyPS1 ? PS1 y-band amplitude
--------------------------------------------------------------------------------
Byte-by-byte Description of file: lggs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (J2000)
13- 23 F11.6 deg DEdeg Declination (J2000)
25- 30 F6.3 mag VmagLGGS LGGS V-band magnitude
32- 37 F6.3 mag e_VmagLGGS LGGS V-band magnitude error
39- 44 F6.3 mag B-VLGGS LGGS B-V color
46- 51 F6.3 mag e_B-VLGGS Error in LGGS B-V color
53- 58 F6.3 mag U-BLGGS ? LGGS U-B color
60- 65 F6.3 mag e_U-BLGGS ? Error in LGGS U-B color
67- 72 F6.3 mag V-RLGGS LGGS V-R color
74- 79 F6.3 mag e_V-RLGGS Error in LGGS V-R color
81- 86 F6.3 mag R-ILGGS ? LGGS R-I color
88- 93 F6.3 mag e_R-ILGGS ? Error in LGGS R-I color
95-104 A10 --- SpTypeLGGS ? LGGS MK Spectral Type
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ukirt.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (J2000)
13- 23 F11.6 deg DEdeg Declination (J2000)
25- 30 F6.3 mag JmagUKIRT UKIRT J-band magnitude
32- 37 F6.3 mag e_JmagUKIRT UKIRT J-band magnitude error
39- 44 F6.3 mag HmagUKIRT UKIRT H-band magnitude
46- 51 F6.3 mag e_HmagUKIRT UKIRT H-band magnitude error
53- 58 F6.3 mag KmagUKIRT UKIRT K-band magnitude
60- 65 F6.3 mag e_KmagUKIRT UKIRT K-band magnitude error
--------------------------------------------------------------------------------
Byte-by-byte Description of file: vhs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (J2000)
13- 23 F11.6 deg DEdeg Declination (J2000)
25- 30 F6.3 mag JmagVHS VHS J-band magnitude
32- 37 F6.3 mag e_JmagVHS VHS J-band magnitude error
39- 44 F6.3 mag KsmagVHS VHS Ks-band magnitude
46- 51 F6.3 mag e_KsmagVHS VHS Ks-band magnitude error
--------------------------------------------------------------------------------
Byte-by-byte Description of file: irsf.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (J2000)
13- 23 F11.6 deg DEdeg Declination (J2000)
25- 30 F6.3 mag JmagIRSF IRSF J-band magnitude
32- 37 F6.3 mag s_JmagIRSF IRSF J-band standard deviation
39- 44 F6.3 mag HmagIRSF IRSF H-band magnitude
46- 51 F6.3 mag s_HmagIRSF IRSF H-band standard deviation
53- 58 F6.3 mag KsmagIRSF IRSF Ks-band magnitude
60- 65 F6.3 mag s_KsmagIRSF IRSF Ks-band standard deviation
--------------------------------------------------------------------------------
Byte-by-byte Description of file: hawki.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (J2000)
13- 23 F11.6 deg DEdeg Declination (J2000)
25- 30 F6.3 mag JmagHAWKI HAWK-I J-band magnitude
32- 37 F6.3 mag e_JmagHAWKI HAWK-I J-band magnitude error
39- 44 F6.3 mag KsmagHAWKI HAWK-I Ks-band magnitude
46- 51 F6.3 mag e_KsmagHAWKI HAWK-I Ks-band magnitude error
--------------------------------------------------------------------------------
Byte-by-byte Description of file: spitzer.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (J2000)
13- 23 F11.6 deg DEdeg Declination (J2000)
25- 29 F5.2 mag IRAC1 Spitzer IRAC1-band magnitude
31- 35 F5.2 mag e_IRAC1 Spitzer IRAC1-band magnitude error
37- 41 F5.2 mag dIRAC1 Difference between the PSF and aperture
photometry magnitude in Spitzer IRAC1-band
43- 47 F5.2 mag IRAC2 Spitzer IRAC2-band magnitude
49- 53 F5.2 mag e_IRAC2 Spitzer IRAC2-band magnitude error
55- 59 F5.2 mag dIRAC2 Difference between the PSF and aperture
photometry magnitude in Spitzer IRAC2-band
61 A1 --- l_IRAC3 3-sigma upper limit for Spitzer
IRAC3-band magnitude
63- 67 F5.2 mag IRAC3 ? Spitzer IRAC3-band magnitude
69- 73 F5.2 mag e_IRAC3 ? Spitzer IRAC3-band magnitude error
75- 79 F5.2 mag dIRAC3 ? Difference between the PSF and aperture
photometry magnitude in Spitzer IRAC3-band
81 A1 --- l_IRAC4 3-sigma upper limit for
Spitzer IRAC4-band magnitude
83- 87 F5.2 mag IRAC4 ? Spitzer IRAC4-band magnitude
89- 93 F5.2 mag e_IRAC4 ? Spitzer IRAC4-band magnitude error
95- 99 F5.2 mag dIRAC4 ? Difference between the PSF and aperture
photometry magnitude in Spitzer IRAC4-band
101 A1 --- l_MIPS24 ? 3-sigma upper limit for
Spitzer MIPS24-band magnitude
103-107 F5.2 mag MIPS24 ? Spitzer MIPS24-band magnitude
109-113 F5.2 mag e_MIPS24 ? Spitzer MIPS24-band magnitude error
--------------------------------------------------------------------------------
Byte-by-byte Description of file: wise.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 deg RAdeg Right ascension (J2000)
13- 23 F11.6 deg DEdeg Declination (J2000)
25- 30 F6.3 mag WISE1 ? ALLWISE WISE1-band magnitude
32- 37 F6.3 mag e_WISE1 ? ALLWISE WISE1-band magnitude error
39- 44 F6.3 --- SNRWISE1 ? ALLWISE WISE1-band SNR
46- 51 F6.3 mag WISE2 ? ALLWISE WISE2-band magnitude
53- 58 F6.3 mag e_WISE2 ? ALLWISE WISE2-band magnitude error
60- 65 F6.3 --- SNRWISE2 ? ALLWISE WISE2-band SNR
67- 72 F6.3 mag WISE3 ? ALLWISE WISE3-band magnitude
74- 79 F6.3 mag e_WISE3 ? ALLWISE WISE3-band magnitude error
81- 86 F6.3 --- SNRWISE3 ? ALLWISE WISE3-band SNR
88- 93 F6.3 mag WISE4 ? ALLWISE WISE4-band magnitude
95-100 F6.3 mag e_WISE4 ? ALLWISE WISE4-band magnitude error
102-107 F6.3 --- SNRWISE4 ? ALLWISE WISE4-band SNR
--------------------------------------------------------------------------------
Acknowledgements:
Ming Yang, myang(at)noa.gr
(End) Ming Yang [NOA, Greece], Patricia Vannier [CDS] 05-Mar-2021