EDP Sciences
Free access
Volume 438, Number 1, July IV 2005
Page(s) 169 - 185
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20042267

A&A 438, 169-185 (2005)
DOI: 10.1051/0004-6361:20042267

Optimal column density measurements from multiband near-infrared observations

M. Lombardi1, 2

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

(Received 27 October 2004 / Accepted 22 March 2005)

We consider from a general point of view the problem of determining the extinction in dense molecular clouds. We use a rigorous statistical approach to characterize the properties of the most widely used optical and infrared techniques, namely the star count and the color excess methods. We propose a new maximum-likelihood method that takes advantage of both star counts and star colors to provide an optimal estimate of the extinction. Detailed numerical simulations show that our method performs optimally under a wide range of conditions and, in particular, is significantly superior to the standard techniques for clouds with high column-densities and affected by contamination by foreground stars.

Key words: dust, extinction -- methods: statistical -- ISM: clouds -- infrared: ISM -- stars: formation

© ESO 2005

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.