2MASS wide field extinction maps: V. Corona Australis

Author(s)
João Alves, Marco Lombardi, Charles Lada
Abstract

We present a near-infrared extinction map of a large region (∼870 deg

2) 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 ≥ 10

23 cm

-2) to the di use Eastern-end (the tail, N ≤ 10

21 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.

Organisation(s)
Department of Astrophysics
External organisation(s)
Universitá degli Studi di Milano, Harvard-Smithsonian Center for Astrophysics
Publication date
05-2014
Austrian Fields of Science 2012
103004 Astrophysics
Keywords
ASJC Scopus subject areas
Astronomy and Astrophysics, Space and Planetary Science
Portal url
https://ucrisportal.univie.ac.at/en/publications/2mass-wide-field-extinction-maps-v-corona-australis(e55616f0-4a96-423b-9462-dca54bd0bbf1).html