J/A+A/606/A100 YSOs in California Molecular Cloud (Lada+, 2017)
HP2 survey. III. The California Molecular Cloud: A sleeping giant revisited.
Lada C.J., Lewis J.A., Lombardi M., Alves J.
<Astron. Astrophys. 606, A100 (2017)>
=2017A&A...606A.100L 2017A&A...606A.100L (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; YSOs ; Photometry, classification
Keywords: stars: formation - dust, extinction - ISM: clouds -
ISM: individual: California Molecular Cloud
Abstract:
We present new high resolution and dynamic range dust column density
and temperature maps of the California Molecular Cloud derived from a
combination of Planck and Herschel dust-emission maps, and 2MASS NIR
dust-extinction maps. We used these data to determine the ratio of the
2.2µm extinction coefficient to the 850µm opacity and found the
value to be close to that found in similar studies of the Orion B and
Perseus clouds but higher than that characterizing the Orion A cloud,
indicating that variations in the fundamental optical properties of
dust may exist between local clouds. We show that over a wide range of
extinction, the column density probability distribution function (pdf)
of the cloud can be well described by a simple power law (i.e.,
PDFN∝AK-n) with an index (n=4.0±0.1) that represents a
steeper decline with AK than found (n~=3) in similar studies of the
Orion and Perseus clouds. Using only the protostellar population of
the cloud and our extinction maps we investigate the Schmidt relation,
that is, the relation between the protostellar surface density,
Σ*, and extinction, AK, within the cloud. We show that
Σ* is directly proportional to the ratio of the protostellar
and cloud pdfs, i.e., PDF*(AK)/PDFN(AK). We use the cumulative
distribution of protostars to infer the functional forms for both
Σ* and PDF*. We find that Σ* is best described by
two power-law functions. At extinctions AK≤2.5mag,
Σ*∝AKβ with β=3.3 while at higher
extinctions β=2.5, both values steeper than those (~=2) found in
other local giant molecular clouds (GMCs). We find that PDF* is a
declining function of extinction also best described by two power-laws
whose behavior mirrors that of Σ*. Our observations suggest
that variations both in the slope of the Schmidt relation and in the
sizes of the protostellar populations between GMCs are largely driven
by variations in the slope, n, of PDFN(AK). This confirms earlier
studies suggesting that cloud structure plays a major role in setting
the global star formation rates in GMCs
Description:
The CMC was observed by the all-sky Planck observatory and by the
Herschel Space Observatory as part of the "Auriga-California" program
(Harvey et al. 2013, Cat J/ApJ/764/133). The Herschel data we used
consisted of observations obtained in parallel mode simultaneously
using the PACS and SPIRE instruments.
For the purposes of this study we use Herschel observations made in
the PACS 160um band, and the SPIRE 250um, 350um and 500um bands.
The file planckherschelfit.fits reports the results of a full SED fit
(with free parameters the optical depth and the temperature), at the
SPIRE 500um resolution (36-arcsec). The file planckherschelfit2-a.fits
uses the temperature from planckherschelfit.fits and the flux at SPIRE
250um to infer the optical depth with a resolution of 18 arcsec.
The results are combined in their respective multi-plane FITS file, with
the following structure:
PLANE1 = Opacity map at 353GHz
PLANE2 = Error on opacity map at 353GHz
PLANE3 = Color temperature [K]
PLANE4 = Error on color temperature [K]
PLANE5 = Modified black-body exponent (Planck)
PLANE6 = Error on modified black-body exponent
PLANE7 = Total chi-square
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 58 177 Young stellar objects in the
California Molecular Cloud
list.dat 194 2 List of fits datacubes
fits/* . 2 Individual fits datacubes
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See also:
J/A+A/587/A106 : Perseus dust optical depth & column density maps (Zari+, 2016)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq Sequential number
4 A1 --- n_Seq [*] Note on Seq
6- 7 I2 h RAh Right ascension (J2000)
9- 10 I2 min RAm Right ascension (J2000)
12- 16 F5.2 s RAs Right ascension (J2000)
18 A1 --- DE- Declination sign (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 29 F5.2 arcsec DEs Declination (J2000)
31- 35 F5.3 mag AK Infrared extinction
37- 41 F5.3 mag e_AK rms uncertainty on AK
43- 45 I3 --- IDB ? Broekhoven-Fiene et al. (2014, Cat.
J/ApJ/786/37) identification number,
([BMH2014] NNN in Simbad)
47- 49 A3 --- ClassB Broekhoven-Fiene et al. (2014,
Cat. J/ApJ/786/37) classification (1)
51- 52 I2 --- IDH ? Harvey et al. (2013, Cat. J/ApJ/764/133)
identification number
([HFG2013] NN in Simbad)
54- 56 A3 --- ClassH Harvey et al. (2013, Cat. J/ApJ/764/133)
classification (1)
58 A1 --- Class [PDS] Classification (2)
--------------------------------------------------------------------------------
Note (1): Classification as follows:
0 = the most dust-enshrouded objects (not detectable at λ<20um)
I = sources with α > 0.3
F = flat spectrum (-0.3 < α < 0.3)
II = sources with -1.6 ≤ α < -0.3
III = sources with α < -1.6
Note (2): Classification as follows:
P = protostar (Class 0/I), (dM/dt)/M*≥10-6 and Menv/M*≥0.05
D = disk (Class II), (dM/dt)/M*<10-6 and Mdisk/M*≥10-6
S = star (Class III) (dM/dt)/M*<10-6 and Mdisk/M*<10-6
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- --- [G]
2- 10 F9.5 deg GLON Galactic longitude
11- 19 F9.5 deg GLAT Galactic latitude
21- 24 I4 --- Nx Number of pixels along X-axis
26- 29 I4 --- Ny Number of pixels along Y-axis
31 I1 --- Nz Number of planes (1)
33- 38 I6 Kibyte size Size of FITS file
40- 66 A27 --- FileName Name of FITS file, in subdirectory fits
68-194 A127 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Note (1): The file planckherschelfit.fits reports the results of a full SED
fit (with free parameters the optical depth and the temperature), at the
SPIRE 500um resolution (36-arcsec). The file planckherschelfit2-a.fits
uses the temperature from planckherschelfit.fits and the flux at SPIRE
250um to infer the optical depth with a resolution of 18 arcsec.
The results are combined in their respective multi-plane FITS file, with
the following structure:
PLANE1 = Opacity map at 353GHz
PLANE2 = Error on opacity map at 353GHz
PLANE3 = Color temperature [K]
PLANE4 = Error on color temperature [K]
PLANE5 = Modified black-body exponent (Planck)
PLANE6 = Error on modified black-body exponent
PLANE7 = Total chi-square
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Lombardi et al., Paper I 2015A&A...576L...1L 2015A&A...576L...1L
Zari et al., Paper II 2016A&A...587A.106Z 2016A&A...587A.106Z, Cat. J/A+A/587/A106
(End) Patricia Vannier [CDS] 18-Jan-2018