Issue |
A&A
Volume 454, Number 3, August II 2006
|
|
---|---|---|
Page(s) | 781 - 796 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20042474 | |
Published online | 17 July 2006 |
2MASS wide field extinction maps
I. The Pipe nebula
1
European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany e-mail: mlombard@eso.org
2
University of Milan, Department of Physics, via Celoria 16, 20133 Milan, Italy
3
Harvard-Smithsonian Center for Astrophysics, Mail Stop 42, 60 Garden Street, Cambridge, MA 02138, USA
Received:
2
December
2004
Accepted:
3
March
2006
Context.
Aims.
We present a , high resolution extinction map
of the Pipe nebula using 4.5 million stars from the Two Micron All
Sky Survey (2MASS) point source catalog.
Methods.
The use of Nicer (Lombardi & Alves 2001, A&A, 377, 1023), a robust and
optimal technique to map the dust column density, allows us to
detect a extinction at a 3-σ level
with a
resolution.
Results.
(i ) We find for the Pipe nebula a normal
reddening law, .
(ii ) We measure the cloud distance using Hipparchos and
Tycho parallaxes, and obtain
. This,
together with the total estimated mass,
,
makes the Pipe the closest massive cloud complex to
Earth. (iii ) We compare the Nicer extinction map
to the NANTEN
CO observations and derive with
unprecedented accuracy the relationship between the near-infrared
extinction and the 12CO column density and hence (indirectly)
the 12CO X-factor, that we estimate to be
in the
range
. (iv ) We identify
approximately 1500 OH/IR stars located within the Galactic bulge
in the direction of the Pipe field. This represents a
significant increase of the known numbers of such stars in the
Galaxy.
Conclusions.
Our analysis confirms the power and simplicity of the color excess
technique to study molecular clouds. The comparison with the NANTEN
CO data corroborates the insensitivity of CO observations to
low column densities (up to approximately
in AV),
and shows also an irreducible uncertainty in the dust-CO correlation
of about
of visual extinction.
Key words: ISM: clouds / ISM: dust, extinction / ISM: structure / ISM: individual objects: Pipe molecular complex / methods: data analysis
© ESO, 2006
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