2010A&A...518L..98P -
Astronomy and Astrophysics, volume 518, L98-98 (2010/7-2)
Mapping the column density and dust temperature structure of IRDCs with Herschel.
PERETTO N., FULLER G.A., PLUME R., ANDERSON L.D., BALLY J., BATTERSBY C., BELTRAN M.T., BERNARD J.-P., CALZOLETTI L., DI GIORGIO A.M., FAUSTINI F., KIRK J.M., LENFESTEY C., MARSHALL D., MARTIN P., MOLINARI S., MONTIER L., MOTTE F., RISTORCELLI I., RODON J.A., SMITH H.A., TRAFICANTE A., VENEZIANI M., WARD-THOMPSON D. and WILCOCK L.
Abstract (from CDS):
Infrared dark clouds (IRDCs) are cold and dense reservoirs of gas potentially available to form stars. Many of these clouds are likely to be pristine structures representing the initial conditions for star formation. The study presented here aims to construct and analyze accurate column density and dust temperature maps of IRDCs by using the first Herschel data from the HI-GAL galactic plane survey. These fundamental quantities, are essential for understanding processes such as fragmentation in the early stages of the formation of stars in molecular clouds. We have developed a simple pixel-by-pixel SED fitting method, which accounts for the background emission. By fitting a grey-body function at each position, we recover the spatial variations in both the dust column density and temperature within the IRDCs. This method is applied to a sample of 22 IRDCs exhibiting a range of angular sizes and peak column densities. Our analysis shows that the dust temperature decreases significantly within IRDCs, from background temperatures of 20-30K to minimum temperatures of 8-15K within the clouds, showing that dense molecular clouds are not isothermal. Temperature gradients have most likely an important impact on the fragmentation of IRDCs. Local temperature minima are strongly correlated with column density peaks, which in a few cases reach NH2=1x1023cm–2, identifying these clouds as candidate massive prestellar cores. Applying this technique to the full HI-GAL data set will provide important constraints on the fragmentation and thermal properties of IRDCs, and help identify hundreds of massive prestellar core candidates.
(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
() Anterior to 2007, before we can link the objet type to a reference, or given by the CDS team in some particular cases
Other object types:
Rad
(ASB,3C,...),
Cl*
([KPS2012]),
SFR
(2013MNRAS),
MoC
(SRBY),
SNR
(SNR),
PoC
([MSM95])
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
quality : flag of quality
E ≥ 10"
D : 1-10" (and some old data)
C : 0.1-1"
B : 0.01-0.1" + 2MASS, Tyc
A : VLBI, Hipparcos
bibcode : bibcode of the coordinates reference
FK4
coord.
(ep=B1950 eq=1950) :
18 44 56.4 -01 59 52
[
]
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
quality : flag of quality
E ≥ 10"
D : 1-10" (and some old data)
C : 0.1-1"
B : 0.01-0.1" + 2MASS, Tyc
A : VLBI, Hipparcos
bibcode : bibcode of the coordinates reference
Gal
coord.
(ep=J2000) :
030.7593 -00.0186
[
]
Syntax of proper motions is : "pm-ra pm-dec [error ellipse] quality bibcode"
pm-ra : mu-ra*cos(dec) (expressed in the ICRS system in mas/yr)
pm-dec : mu-dec (expressed in the ICRS system in mas/yr)
[error ellipse] : error major axis and minor axis (in mas), orientation angle (in deg)
quality : flag of quality (A=best quality -> E=worst quality, {� } =unknown quality)
Syntax of radial velocity (or/and redshift) is : "value [error] (wavelength) quality bibcode"
value : radial velocity or/and redshift (Heliocentric frame) according to your Output Options
(redshift may be not displayed if the data value is <0 and the database inside value is a radial velocity)
[error] : error of the corresponding value displayed before
(wavelength) : wavelength range of the measurement : Rad, mm, IR, Opt, UV, Xray, Gam or '∼'(unknown)
quality : flag of quality ( A=best quality -> E=worst quality, ∼=unknown quality)
References (531 between 1850 and 2024) (Total 531)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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