Volume 565, May 2014
|Number of page(s)||10|
|Section||Interstellar and circumstellar matter|
|Published online||23 April 2014|
2MASS wide-field extinction maps
V. Corona Australis⋆
1 University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, 1180 Vienna, Austria
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: 28 June 2013
Accepted: 6 January 2014
We present a near-infrared extinction map of a large region (~870 deg2) covering the isolated Corona Australis complex of molecular clouds. We reach a 1-σ error of 0.02 mag in the K-band extinction with a resolution of 3 arcmin over the entire map. We find that the Corona Australis cloud is about three times as large as revealed by previous CO and dust emission surveys. The cloud consists of a 45 pc long complex of filamentary structure from the well known star forming Western-end (the head, N ≥ 1023 cm-2) to the diffuse Eastern-end (the tail, N ≤ 1021 cm-2). Remarkably, about two thirds of the complex both in size and mass lie beneath AV ~ 1 mag. We find that the probability density function (PDF) of the cloud cannot be described by a single log-normal function. Similar to prior studies, we found a significant excess at high column densities, but a log-normal + power-law tail fit does not work well at low column densities. We show that at low column densities near the peak of the observed PDF, both the amplitude and shape of the PDF are dominated by noise in the extinction measurements making it impractical to derive the intrinsic cloud PDF below AK < 0.15 mag. Above AK ~ 0.15 mag, essentially the molecular component of the cloud, the PDF appears to be best described by a power-law with index −3, but could also described as the tail of a broad and relatively low amplitude, log-normal PDF that peaks at very low column densities.
Key words: ISM: structure / ISM: clouds / dust, extinction / ISM: general
FITS files of the extinction maps are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/565/A18
© ESO, 2014
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