J/MNRAS/495/3614 IR and sub-mm variability in protostars (Contreras+, 2020)
The relationship between mid-infrared and sub-millimetre variability of deeply
embedded protostars.
Contreras Pena C., Johnstone D., Baek G., Herczeg G.J., Mairs S.,
Scholz A., Lee J.-E.
<Mon. Not. R. Astron. Soc., 495, 3614-3635 (2020)>
=2020MNRAS.495.3614C 2020MNRAS.495.3614C (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Stars, pre-main sequence ; Stars, variable ;
Positional data ; Infrared ; Millimetric/submm sources
Keywords: stars: formation - stars: pre-main-sequence - stars: protostars -
stars: variables: T Tauri, Herbig Ae/Be - infrared: stars -
submillimetre: stars
Abstract:
We study the relationship between the mid-infrared (mid-IR) and
sub-millimetre (sub-mm) variability of deeply embedded protostars
using the multi-epoch data from the Wide-field Infrared Survey
Explorer (WISE/NEOWISE) and the ongoing James Clerk Maxwell Telescope
(JCMT) Transient Survey. Our search for signs of stochastic (random)
and/or secular (roughly monotonic in time) variability in a sample of
59 young stellar objects (YSOs) revealed that 35 are variable in at
least one of the two surveys. This variability is dominated by secular
changes. Of those objects with secular variability, 14 objects (22 per
cent of the sample) show correlated secular variability over mid-IR
and sub-mm wavelengths. Variable accretion is the likely mechanism
responsible for this type of variability. Fluxes of YSOs that vary in
both wavelengths follow a relation of
log10F4.6(t)=ηlog10F850(t) between the mid-IR and sub-mm,
with η=5.53±0.29. This relationship arises from the fact that
sub-mm fluxes respond to the dust temperature in the larger envelope
whereas the mid-IR emissivity is more directly proportional to the
accretion luminosity. The exact scaling relation, however, depends on
the structure of the envelope, the importance of viscous heating in
the disc, and dust opacity laws.
Description:
The JCMT Transient Survey uses the SCUBA-2 instrument (Holland et al.
2013MNRAS.430.2513H 2013MNRAS.430.2513H) on JCMT to monitor sub-mm continuum emission from
eight nearby star-forming regions. The eight regions, Ophiuchus Core,
NGC 1333, IC 348, Serpens Main, Serpens South, OMC 2/3, NGC 2024, and
NGC 2068 were selected for the high density of deeply embedded
protostars (Herczeg et al. 2017ApJ...849...43H 2017ApJ...849...43H). Each region is
observed in a PONG mode that produces an image with smooth sensitivity
across a field with 30arcmin diameter, with an integration time set to
reach ∼12mJy at 850µm. The 850µm fluxes are measured from the
peak brightness of the object, and are then calibrated using bright
sources that are measured to be non-varying at 850µm.
Also, in this work we used the W1 and W2 observations from the WISE
All-Sky single exposure data base (Cutri et al. 2012yCat.2311....0C 2012yCat.2311....0C,
Cat. II/311), which contains observations taken between 2010 January
and August . In addition, we used the NEOWISE single exposure data
base (2019 data release) that contains W1 and W2 observations from
2013 December until 2018 December (Cutri et al. 2015nwis.rept....1C).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 207 59 The 59 sources where JCMT and WISE fluxes likely
arise from the same source
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See also:
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Region JCMT Transient Survey region
16- 18 I3 --- ID Source number
20- 21 I2 h RAh Right ascension (J2000)
23- 24 I2 min RAm Right ascension (J2000)
26- 29 F4.1 s RAs Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 41 F4.1 arcsec DEs Declination (J2000)
43- 65 A23 --- JCMT JCMT source designation
(JCMTPP_JHHMMSS.s+DDMMSS)
67- 90 A24 --- Name Other name
92- 95 A4 --- YSOclass YSO class (1)
97- 157 A61 --- r_YSOclass Reference for YSOclass
159- 163 F5.2 mag W2mag Average WISE W2 (4.6um) band magnitude
165- 167 F3.1 mag E_W2mag Upper error on W2mag (90th percentile)
169- 171 F3.1 mag e_W2mag Lower error on W2mag (10th percentile)
173- 177 F5.2 --- SD/SDfidW Ratio of the standard deviation of the
observed W2 flux to a fiducial model of
the expected uncertainty (2)
179- 184 F6.2 --- S/dSW Ratio of the slope of the linear fit to
the W2 flux to the uncertainty in the
slope measurement (2)
186- 187 I2 --- NW2 Number of WISE points used in the analysis
of variability
189- 192 F4.2 Jy/beam Flux JCMT/SCUBA-2 850um flux
194- 197 F4.2 --- SD/SDfidJ Ratio of the standard deviation of the
observed JCMT light curves to a fiducial
model of the expected uncertainty (2)
199- 204 F6.2 --- S/dSJ Ratio of the slope of the linear fit to
the JCMT flux to the uncertainty in the
slope measurement (2)
206- 207 I2 --- NJCMT Number of epochs used in the analysis of
variability
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Note (1): In cases where we do not find any information in the literature to
classify the YSOs, the classification arises from SED inspection and
is marked with a '?' sign
Note (2): See Section 4 for more details
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 21-Jun-2023