J/ApJ/961/176 Multiwavelength study of the Sh2-87 HII region (Biswas+, 2024)
Star formation in the HII region Sh2-87: evidence of global hierarchical
collapse.
Biswas S., Mondal S., Hoque A., Panja A., Baug T., Das R.
<Astrophys. J., 961, 176 (2024)>
=2024ApJ...961..176B 2024ApJ...961..176B
ADC_Keywords: Photometry, ugriz; Photometry, infrared; Stars, distances; YSOs;
H II regions; Photometry, H-alpha
Keywords: Star formation ; Star forming regions ; H II regions ;
Pre-main sequence stars ; Young stellar objects ; Interstellar medium
Abstract:
We present a detailed study of the Sh2-87 HII region using a
multiwavelength data set in optical to radio bands. A Herschel column
density map revealed that the host cloud is filamentary in nature, and
together they formed a central dense hub. The extinction map generated
using near-infrared photometric data also signifies the nonuniform
distribution of the cloud and reveals its filamentary nature. We
estimated a sizable variable extinction over the region up to
AV=34.4mag, with an average value of AV=3.4mag. Using the various
infrared color-color criteria, we identified 13 Class I and
202 Class II young stellar objects (YSOs) and 22 Hα-emitting
sources toward this region. Further analysis showed that the cluster
is mainly composed of low-mass YSOs with a typical age of ∼3Myr having
masses in the range of 0.1-6.0M☉. The identified evolved YSOs
(i.e., Class II YSOs) are primarily distributed along the filaments
and in the outer parts of the cloud, while the recent star formation,
inferred by the presence of Class I YSOs, ionized gas, and
star-forming clumps, is observed in the hub region. The overall star
formation scenario in the Sh2-87 region resembles the global
hierarchical collapse model of star formation, where younger massive
star formation activity is expected at the central hub along with the
distribution of evolved low-mass YSOs in the filaments and the outer
parts of the cloud.
Description:
We utilized the optical/NIR data from the Panoramic Survey Telescope
and Rapid Response System 1 (Pan-STARRS1, or PS1; see II/349). The PS1
system carried out the observations with the five filters gP1, rP1,
iP1, zP1, and yP1 distributed over wavelengths ranging from 400 to
1000nm and centered on 481, 617, 752, 866, and 962nm, respectively.
The INT/WFC Photometric Hα Survey (IPHAS) encompasses a 1800deg2
area of sky in the northern Galactic plane, and it uses the narrowband
Ha filter (656.8nm) and broadband Sloan r (625.4nm) and i (774.3nm)
filters for observations. We acquired the photometric data for r, i,
and Ha bands from the IPHAS data release 2 (DR2) catalog
(Barentsen+ 2014, II/321).
The photogeometric distances of the point sources were obtained from
Bailer-Jones+ (2021, I/352) estimated using the astrometric data from
the Gaia Early Data Release 3 (Gaia EDR3, I/350; superseded by I/355).
The NIR J-, H-, and K-band photometric data were obtained from the
sixth data release of the UKIRT Infrared Deep Sky Survey (UKIDSS
DR6PLUS) of the Galactic Plane Survey (GPS). Magnitudes for a few
saturated sources in the UKIDSS catalog were obtained from the Two
Micron All Sky Survey (2MASS).
We obtained the MIR photometric magnitudes of the point objects from
the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire
(GLIMPSE; se Cat. II/293), which have imaged the region with the
Infrared Array Camera (IRAC) in the four MIR bands centered at 3.6,
4.5, 5.8, and 8.0um, and the corresponding angular resolution of the
images is about 2".
In addition, we have taken the MIR photometric magnitudes of the point
sources from the first three bands ([3.4], [4.6], [12]) of the ALLWISE
catalog.
See Section 2.5
The CO molecular line data were obtained from the James Clerk Maxwell
Telescope (JCMT) archive. In this work, we used 12CO(3-2) data
(Program ID: M14AU09).
For the dust continuum emission in our target region, we also utilized
850um continuum data observed from the Submillimetre Common User
Bolometer Array 2 (SCUBA-2) installed on JCMT.
We also utilized the publicly available Herschel H2 column density
map generated from the 160, 250, 350, and 500um wavelength bands.
The map has a spatial resolution of ∼12".
Section 2.6.
We obtained the radio continuum map at 1.4GHz for our target region
from the NRAO VLA Sky Survey (NVSS; VIII/65) archive.
We also used the radio continuum data at 5GHz from the Coordinated
Radio and Infrared Survey for High-Mass Star Formation (CORNISH).
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
19 46 20.69 +24 35 15.3 Sh2-87 = IRAS 19442+2427
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 201 215 Photometric catalog of YSOs toward Sh2-87
table2.dat 158 22 Photometric catalog of Hα emitters
toward Sh2-87
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See also:
VII/20 : Catalogue of HII Regions (Sharpless 1959)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VII/233 : 2MASS All-Sky Extended Source Catalog (XSC) (IPAC/UMass, 2003-2006)
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/328 : AllWISE Data Release (Cutri+ 2013)
VI/139 : Herschel Observation Log (Herschel Science Centre, 2013)
II/321 : IPHAS DR2 Source Catalogue (Barentsen+, 2014)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
I/352 : Distances to 1.47 billion stars in Gaia EDR3 (Bailer-Jones+, 2021)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/ApJS/91/659 : Ultracompact HII regions radio images (Kurtz+ 1994)
J/ApJ/675/491 : Lynds 988e JHKs and IRAC photometry (Allen+, 2008)
J/ApJ/682/445 : Spitzer observations of S254-S258 (Chavarria+, 2008)
J/ApJ/674/336 : Spitzer observations of NGC 1333 (Gutermuth+, 2008)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJ/720/679 : Optical spectroscopy in Cygnus X region (Beerer+, 2010)
J/ApJ/712/797 : YSOs in Vul OB1 association (Billot+, 2010)
J/MNRAS/415/103 : IPHAS T Tauri candidates in IC 1396 (Barentsen+, 2011)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/MNRAS/432/3445 : YSOs on HII complex Sh2-252 (Jose+, 2013)
J/ApJS/205/1 : CORNISH project. II. Source catalog (Purcell+, 2013)
J/A+A/561/A83 : SDC13 infrared dark clouds spectra (Peretto+, 2014)
J/MNRAS/454/4335 : Multiwavelength photometry of Sh 2-138 YSOs (Baug+, 2015)
J/ApJ/836/98 : YSOs search in Stock 8 with opt. to IR photom. (Jose+, 2017)
J/MNRAS/468/2684 : IC1805 YSOs (Panwar+, 2017)
J/A+A/642/A87 : Hub-filament candidates (Kumar+, 2020)
J/AJ/159/153 : Optical & IR phot. in the HII region Sh2-242 (Panja+, 2020)
J/ApJ/939/46 : Stellar contents in the Sh2-112 cloud complex (Panja+, 2022)
http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/jcmt/ : JCMT archive homepage
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- Class Class identifier (II: 202 occurrences;
I: 13 occurrences)
4- 6 I3 --- Seq [1/202] Serial number
8- 17 F10.6 deg RAdeg [296.4/296.8] Right Ascension (J2000)
19- 28 F10.7 deg DEdeg [24.4/24.8] Declination (J2000)
30- 36 F7.3 mag 3.6mag [8.6/14.5]?=999 Spitzer/IRAC 3.6um band
apparent magnitude
38- 44 F7.3 mag e_3.6mag [0.003/0.3]?=999 Uncertainty in 3.6mag
46- 52 F7.3 mag 4.5mag [8.2/14.13]?=999 Spitzer/IRAC 4.5um band
apparent magnitude
54- 60 F7.3 mag e_4.5mag [0.03/0.4]?=999 Uncertainty in 4.5mag
62- 68 F7.3 mag 5.8mag [7.7/13.01]?=999 Spitzer/IRAC 5.8um band
apparent magnitude
70- 76 F7.3 mag e_5.8mag [0.02/0.4]?=999 Uncertainty in 5.8mag
78- 84 F7.3 mag 8.0mag [0/12.6]?=999 Spitzer/IRAC 8.0um band apparent
magnitude
86- 92 F7.3 mag e_8.0mag [0/0.4]?=999 Uncertainty in 8.0mag
94- 100 F7.3 mag Jmag [11.6/19.9]?=999 UKIDSS J band apparent
magnitude
102- 108 F7.3 mag e_Jmag [0/0.3]?=999 Uncertainty in Jmag
110- 116 F7.3 mag Hmag [11.2/18.4]?=999 UKIDSS H band apparent
magnitude
118- 124 F7.3 mag e_Hmag [0/0.2]?=999 Uncertainty in Hmag
126- 132 F7.3 mag Kmag [9.98/17.6]?=999 UKIDSS K band apparent
magnitude
134- 140 F7.3 mag e_Kmag [0/0.2]?=999 Uncertainty in Kmag
142- 149 F8.4 mag gmag [14.6/26.5]?=999 PANSTARRS g band apparent
magnitude
151- 158 F8.4 mag e_gmag [0/0.5]?=999 Uncertainty in gmag
160- 167 F8.4 mag ymag [12.89/19.74]?=999 PANSTARRS y band apparent
magnitude
169- 176 F8.4 mag e_ymag [0.002/0.3]?=999 Uncertainty in ymag
178- 184 F7.3 kpc Dist [1.1/6.3]?=999 Estimated Gaia EDR3
photogeometric distance
186- 193 F8.4 kpc e_Dist [0.045/2.8]?=999 Lower uncertainty in Dist
195- 201 F7.3 kpc E_Dist [0.048/3]?=999 Upper uncertainty in Dist
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/22] Serial number
4- 12 F9.5 deg RAdeg [296.41136/296.7] Right Ascension (J2000)
14- 21 F8.5 deg DEdeg [24.47/24.7] Declination (J2000)
23- 27 F5.2 mag rmag [14.05/19.9] IPHAS r band apparent magnitude
29- 32 F4.2 mag e_rmag [0/0.07] Uncertainty in rmag
34- 38 F5.2 mag imag [13.38/18.52] IPHAS i band apparent magnitude
40- 43 F4.2 mag e_imag [0/0.04] Uncertainty in imag
45- 49 F5.2 mag Hamag [13.39/18.57] IPHAS Hα band apparent
magnitude
51- 54 F4.2 mag e_Hamag [0/0.04] Uncertainty in Hamag
56- 62 F7.3 mag Jmag [11.69/16.72]?=999 UKIDSS J band apparent
magnitude
64- 70 F7.3 mag e_Jmag [0/0.02]?=999 Uncertainty in Jmag
72- 78 F7.3 mag Hmag [11.29/15.91]?=999 UKIDSS H band apparent
magnitude
80- 86 F7.3 mag e_Hmag [0/0.02]?=999 Uncertainty in Hmag
88- 93 F6.3 mag Kmag [9.98/15.51] UKIDSS K band apparent magnitude
95- 99 F5.3 mag e_Kmag [0/0.03] Uncertainty in Kmag
101- 108 F8.4 mag gmag [14.89/23.82]?=999 PANSTARRS g band apparent
magnitude
110- 117 F8.4 mag e_gmag [0/0.2]?=999 Uncertainty in gmag
119- 124 F6.3 mag ymag [13.22/18.06] PANSTARRS y band apparent
magnitude
126- 131 F6.4 mag e_ymag [0.004/0.15] Uncertainty in ymag
133- 139 F7.3 kpc Dist [1/4.2]?=999 Estimated Gaia EDR3 photogeometric
distance
141- 147 F7.3 kpc e_Dist [0.06/1.4]?=999 Lower uncertainty in Dist
149- 155 F7.3 kpc E_Dist [0.08/2.2]?=999 Upper uncertainty in Dist
157- 158 A2 --- Class Class identifier
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Apr-2026