Hα emission objects in Circinus. Issue 3 (1st March 2013)

• Record Type: Journal Article
• Authors: Noroozi, S.; Haas, M.; Chen, Z.; Chini, R.
• Is Part Of: Astronomische Nachrichten. Volume 334:Issue 3(2013)
• Page Start: 282
• Page End: 287
• Publication Date: 2013-03-01
• Subjects: Astronomy -- Periodicals; 520.5
• DOI: 10.1002/asna.201211843
• Languages: English
• ISSNs: 0004-6337

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>We present a new survey for Hα emission objects in the Circinus cloud complex and introduce an efficient photometric method for detecting Hα emission via observations in a narrow‐band filter. The observed flux is compared to a blackbody fit of the continuum. Our search strategy reveals 20 stars with strong Hα emission (EW &gt; 10 Å), eight of them being new detections. All Hα stars display infrared excess corroborating their youth. On the other hand, the region contains a number of infrared excess objects that do not show Hα emission. Our results support the picture that accretion – as witnessed by Hα emission – is a highly variable phenomenon. Therefore, Hα surveys can only trace the temporarily active objects. In contrast, infrared excess is a more robust tracer that reveals most of the population of young stellar objects in a star forming region. Our analysis of the general stellar content of the region yields a reliable distance of 450 pc for the Circinus cloud. Moreover, we find a ratio of total‐to‐selective extinction of <italic>R</italic>^{<italic>V</italic>} = 2.8 suggesting that smaller‐than‐normal dust grains may be present. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)</p> </abstract>