A Corona Australis cloud filament seen in NIR scattered light

M. Juvela; V.-M. Pelkonen; P. Padoan; K. Mattila

doi:doi:10.1051/0004-6361:20078470

Free access

Issue		A&A Volume 480, Number 2, March III 2008


Page(s)		445 - 458
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20078470

A&A 480, 445-458 (2008)
DOI: 10.1051/0004-6361:20078470

I. Comparison with extinction of background stars

M. Juvela¹, V.-M. Pelkonen¹, P. Padoan², and K. Mattila¹

¹ Helsinki University Observatory, 00014, University of Helsinki, Finland
² Department of Physics, University of California, San Diego, CASS/UCSD 0424, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA
e-mail: ppadoan@ucsd.edu

(Received 12 August 2007 / Accepted 7 January 2008)

Abstract
Context.Using state-of-art near-infrared (NIR) instrumentation the near-infrared light scattered from interstellar clouds can be mapped over large areas. Measurement of the surface brightness provides information on the line-of-sight dust column density. Scattered light therefore provides an important tool to study the mass distribution of quiescent, interstellar clouds at high, even sub-arcsecond resolution.
Aims.We test the assumption that light scattering is the dominant contributor to the surface brightness in all NIR bands. Furthermore, we want to show that scattered light can be used for an accurate estimation of dust column densities in clouds with extinction in the range $A_{\rm V}$ = 1-15 $^{\rm m}$ .
Methods.We have obtained NIR images of a quiescent filament in the molecular cloud. The observations provide maps of diffuse surface brightness in the J, H, and Ks photometric bands. Assuming that the main contributor is indeed scattered light, we convert surface brightness data into a map of dust column density. The same observations provide colour excesses for a large number of background stars. These data are used to derive an extinction map of the cloud. The two, largely independent tracers of the cloud structure are compared.
Results.In regions where the extinction is below $A_{\rm V}$ ~ 15 $^{\rm m}$ , both diffuse surface brightness and background stars lead to similar column density estimates. The existing differences can be explained as a result of normal observational errors and bias in the sampling of extinctions provided by the background stars. There is no indication that thermal dust-emission would have a significant contribution even in the Ks band. The results show that, below $A_{\rm V}$ ~ 15 $^{\rm mag}$ , scattered light provides a reliable way to map cloud structure. Compared with the use of background stars, it can provide data of a significantly higher spatial resolution.

Key words: ISM: structure -- ISM: clouds -- infrared: ISM -- ISM: dust, extinction -- scattering -- techniques: photometric

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.