J/ApJ/914/115 Spitzer MIR and NIR study of Sh2-208 (Yasui, 2021)
Spitzer mid-infrared study of Sh 2-208: evolution of protoplanetary disks in
low-metallicity environments.
Yasui C.
<Astrophys. J., 914, 115 (2021)>
=2021ApJ...914..115Y 2021ApJ...914..115Y
ADC_Keywords: Clusters, open; Photometry, infrared; YSOs
Keywords: Protoplanetary disks ; Galaxy abundances ; Infrared sources ;
Open star clusters ; Metallicity ; Star formation ;
Pre-main sequence ; Protostars ; H II regions
Abstract:
This study presents sensitive mid-infrared (MIR) photometry obtained
with the Spitzer/IRAC for a young cluster in Sh 2-208 (S208) located
in one of the lowest-metallicity HII regions in the Galaxy,
[O/H]=-0.8dex. Previous studies suggested that the cluster is ∼0.5Myr
old and has a distance of D=4kpc, which is consistent with the
astrometric distance from Gaia EDR3. In a ∼3.5'x4' field, 96 sources
were detected in at least one MIR band at ≥10σ, covering
intermediate-mass stars with a ∼1.0M☉ mass detection limit. A
total of 41 probable cluster members were identified based on the
spatial distributions of spectral energy distribution slopes derived
from the near-infrared (NIR) KS and IRAC bands and extinctions of the
sources. The cumulative distribution of the spectral energy
distribution slopes for the S208 cluster was not significantly
different from those of other clusters in solar-metallicity
environments with approximately the same age for intermediate-mass
stars, if one also considers nondetected MIR sources identified as
S208 cluster members from NIR observations. This suggests that the
degree of dust growth/settling does not significantly change with
metallicities as different as ∼1dex. The fraction of stars with MIR
disk emissions for the cluster members with ≥1M☉ was 64%-93%,
which is comparable to the results in solar-metallicity environments.
Although this may suggest that dominant disk dispersal mechanisms for
intermediate-mass stars have either no or very weak dependence on
metallicity, it can be argued alternatively that this may suggest that
the disk dispersal process does not work effectively at this young
stage.
Description:
We obtained four-band Spitzer/IRAC images of S208 from archival data
obtained on 2007 October 16 (UT), for which the program ID is 30734. A
five-position Gaussian dithering pattern was used, and the resulting
images in each wavelength band covered a 5'x5' area. The total
integration time was 471s in each of the four bands.
We also used the results of NIR JHK-band photometry from images with
spatial resolutions ≲1" in the literature (Yasui+ 2016AJ....151..115Y 2016AJ....151..115Y).
The investigators obtained deep imaging with the 8.2m Subaru telescope
equipped with MOIRCS. See Section 3.2.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
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04 19 32.91 +52 58 41.5 S208 = SH 2-208
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 120 96 Spitzer/IRAC point-source catalog of S208
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See also:
VII/20 : Catalogue of HII Regions (Sharpless 1959)
VII/50 : CO Radial Velocities Toward Galactic H II Regions (Blitz+ 1982)
VI/102 : Geneva stellar evolution tracks and isochrones (Lejeune+, 2001)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJ/573/366 : Infrared photometry of Trapezium cluster (Muench+, 2002)
J/A+A/404/223 : 2MASS IR star clusters in the Galaxy (Bica+, 2003)
J/AJ/129/856 : Herbig Ae/Be stars in nearby OB assoc. (Hernandez+, 2005)
J/A+A/438/663 : JHKL photometry of 30 Dor (Maercker+, 2005)
J/AJ/131/1574 : Infrared photometry of IC348 members (Lada+, 2006)
J/AJ/132/2268 : SAGE calibration stars (Meixner+, 2006)
J/ApJS/162/346 : Abundance gradients in the Galaxy (Rudolph+, 2006)
J/ApJ/671/1784 : Ori OB1 IRAC/MIPS observations (Hernandez+, 2007)
J/ApJ/674/336 : Spitzer observations of NGC 1333 (Gutermuth+, 2008)
J/ApJ/686/1195 : IR photometry in the γ Vel cluster (Hernandez+, 2008)
J/AJ/136/18 : LMC SAGE. New candidate YSOs (Whitney+, 2008)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/AJ/138/1243 : The star formation history of the LMC (Harris+, 2009)
J/A+A/503/107 : Spitzer/IRAC view of Sh2-284 (Puga+, 2009)
J/A+A/509/A104 : UBVRIJHK photometry of Dolidze 25 (Delgado+, 2010)
J/ApJ/721/357 : YSOs in the LMC star-forming region N206 (Romita+, 2010)
J/AJ/144/192 : Spitzer survey of Orion A and B. I. YSOs (Megeath+, 2012)
J/MNRAS/421/78 : LMC PMS stars mass accretion rates (Spezzi+, 2012)
J/MNRAS/442/2543 : Dust disks around star in young clusters (Yasui+, 2014)
J/AJ/153/240 : ALMA survey of protopl. disks in sigma Ori (Ansdell+, 2017)
J/ApJ/869/L41 : DSHARP I. Sample, ALMA obs. log & overview (Andrews+, 2018)
J/A+A/618/A93 : Gaia DR2 open clusters in the MW (Cantat-Gaudin+, 2018)
J/ApJ/875/51 : Mass accretion rates of PMS stars. VI. LH95 (Biazzo+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/96] Running sequence number
4- 12 F9.6 deg RAdeg Right ascension in decimal degrees (J2000)
14- 22 F9.6 deg DEdeg Declination in decimal degrees (J2000)
24- 28 F5.2 mag Jmag [11.9/20.43]? J-band magnitude
30- 33 F4.2 mag e_Jmag [0.01/0.17]? Uncertainty on the Jmag
35- 39 F5.2 mag Hmag [12.56/17.98]? H-band magnitude
41- 44 F4.2 mag e_Hmag [0.01/0.07]? Uncertainty on the Hmag
46- 50 F5.2 mag Ksmag [11.86/16.43]? Ks-band magnitude
52- 55 F4.2 mag e_Ksmag [0.01/0.06]? Uncertainty on the Ksmag
57- 61 F5.2 mag 3.6mag [10.94/15.8]? Spitzer/IRAC 3.6um band magnitude
63- 66 F4.2 mag e_3.6mag [0.03/0.1]? Uncertainty on the 3.6mag
68- 72 F5.2 mag 4.5mag [10.14/15.16]? Spitzer/IRAC 4.5um band magnitude
74- 77 F4.2 mag e_4.5mag [0.03/0.1]? Uncertainty on the 4.5mag
79- 83 F5.2 mag 5.8mag [8.4/10.89]? Spitzer/IRAC 5.8um band magnitude
85- 88 F4.2 mag e_5.8mag [0.03/0.09]? Uncertainty on the 5.8mag
90- 93 F4.2 mag 8.0mag [8.59/9.66]? Spitzer/IRAC 8um band magnitude
95- 98 F4.2 mag e_8.0mag [0.03/0.05]? Uncertainty on the 8.0mag
100- 103 F4.1 mag Av [0/15.7]? Visual extinction (1)
105- 109 F5.2 --- alpha [-2.97/5.4] Spectral index α (2)
111- 115 F5.2 --- alpha0 [-2.97/3.69]? Spectral index α0 (2)
117- 120 A4 --- Note Note (3)
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Note (1): AV values are only provided for sources with valid JHKs photometry.
Note (2): SED slopes [d.log(λFλ)/d.log(λ)] derived from
the NIR KS and IRAC bands. The SED slopes derived from the observed
data for each source (α) are shown in Column (12), and the SED
slopes derived from the data corrected for extinction using the AV
derived for each object (α0) are shown in Column (13).
Note (3): Note as follows:
CL = probable cluster members
(CL) = sources inside the cluster region, which are not identified as
cluster members
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 12-Dec-2022