J/AJ/157/112 Infrared photometry of YSOs in the W4 cloud complex (Panwar+, 2019)
Understanding formation of young, distributed low-mass stars and clusters
in the W4 cloud complex.
Panwar N., Samal M.R., Pandey A.K., Singh H.P., Sharma S.
<Astron. J., 157, 112 (2019)>
=2019AJ....157..112P 2019AJ....157..112P (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; YSOs ; Photometry, infrared
Keywords: H II regions - open cluster: star formation - stars: formation -
stars: low-mass - stars: pre-main sequence
Abstract:
It is well known that most of the stars form in rich clusters. However,
recent Spitzer observations have shown that a significant number of stars
also form in the distributed mode; their origin is not well understood.
In this work, we aim to investigate clustered and distributed modes of
star formation in the W4 complex. To do so, we identified and characterized
the young stellar population associated with the region using homogeneous
infrared data sets obtained from the Two Micron All Sky Survey, GLIMPSE,
MIPS, and Wide-field Infrared Survey Explorer surveys. We make stellar
surface density and minimum spanning tree maps to identify young clusters,
and use Spitzer images to identify irradiated structures, such as
elephant-trunk-like structures (ETLSs) and pillars in the region. The
surface density distribution of the young stellar objects (YSOs) reveals
three new clusterings and ∼50% distributed protostars in the H II region.
The clusters are of low-mass nature but significantly younger than the
central cluster IC 1805. We identified ∼38 ETLSs in the region, a majority
of which consist of one or a few stars at their tips. We find that these
stars are low-mass (<2 M☉) YSOs, located at the outskirts (>17 pc)
of the cluster IC 1805 and are part of the scattered distributed population.
We argued that the star formation in the ETLSs of W4 is going on possibly
due to the triggering effect of the expanding W4 bubble. Although
high-resolution photometric and spectroscopic data would be required to
confirm the scenario, nonetheless, we discuss the implications of this
scenario for our understanding of distributed low-mass star formation
in cloud complexes as opposed to other mechanisms such as turbulent
fragmentation and dynamical ejection.
Description:
The W4 bubble was observed in 24 µm using the Multi-band Imaging
Photometer for Spitzer (MIPS) in two epochs. However, a part of the bubble
is missing in these observations. We downloaded the MIPS post basic
calibrated data images from the Spitzer archive, which were created at
the image scale of 2.45" per pixel. We also used the archival infrared
array camera (IRAC) data from GLIMPSE-360 (P.I. - B.A. Whitney). The
GLIMPSE-360 observations were taken during the Spitzer warm mission and
hence were available only at 3.6 and 4.5 µm. The Wide-field Infrared
Survey Explorer (WISE) has explored the sky at four wavebands (3.4, 4.6,
12, and 22 µm). We have used the WISE catalog from Cutri et al. (2014,
Cat. II/328). We selected only sources that have contamination and
confusion flags "000" in 3.4, 4.6, and 12 µm wavebands. NIR JHK data
for the stars in the H II region have been obtained from the Two Micron
All Sky Survey (2MASS) Point Source Catalog (Cutri et al. 2003,
Cat. II/246).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 130 524 YSOs from MIPS, IRAC/2MASS and WISE data
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/328 : AllWISE Data Release (Cutri+ 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/524] Index identifier
5- 12 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000)
14- 21 F8.5 deg DEdeg Declination in decimal degrees (J2000)
23- 27 F5.2 mag Jmag [8.13/17.2]?=99.99 2MASS J band magnitude (1)
29- 33 F5.2 mag e_Jmag [0.02/0.22]?=99.99 Uncertainty in Jmag (1)
35- 39 F5.2 mag Hmag [7.84/16.21]?=99.99 2MASS H band magnitude (1)
41- 45 F5.2 mag e_Hmag [0.02/0.2]?=99.99 Uncertainty in Hmag (1)
47- 51 F5.2 mag Ksmag [7.46/15.56]?=99.99 2MASS Ks band magnitude (1)
53- 57 F5.2 mag e_Ksmag [0.01/0.22]?=99.99 Uncertainty in Ksmag (1)
59- 63 F5.2 mag 3.6mag [6.73/16.54]?=99.99 Spizter/IRAC 3.6 micron band
magnitude (1)
65- 69 F5.2 mag e_3.6mag [0.02/0.15]?=99.99 Uncertainty in 3.6mag (1)
71- 75 F5.2 mag 4.5mag [5.92/15.84]?=99.99 Spizter/IRAC 4.5 micron band
magnitude (1)
77- 81 F5.2 mag e_4.5mag [0.02/0.14]?=99.99 Uncertainty in 4.5mag (1)
83- 87 F5.2 mag 24mag [0.72/9.53]?=99.99 Spizter/MIPS 24 micron band
magnitude (1)
89- 94 F6.3 mag e_24mag [0.01/0.14]?=99.99 Uncertainty in 24mag (1)
96-100 F5.2 mag 3.4mag [6.72/16.81]?=99.99 WISE 3.4 micron band
magnitude (1)
102-106 F5.2 mag e_3.4mag [0.02/0.19]?=99.99 Uncertainty in 3.4mag (1)
108-112 F5.2 mag 4.6mag [6.36/15.79]?=99.99 WISE 4.6 micron band
magnitude (1)
114-118 F5.2 mag e_4.6mag [0.02/0.18]?=99.99 Uncertainty in 4.6mag (1)
120-124 F5.2 mag 12mag [3.08/11.38]?=99.99 WISE 12 micron band magnitude
(1)
126-130 F5.2 mag e_12mag [0.01/0.2]?=99.99 Uncertainty in 12mag (1)
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Note (1): 99.99 indicates a missing value.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 07-Jun-2019