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The Spitzer Survey of Interstellar Clouds in the Gould Belt

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The Spitzer Survey of Interstellar Clouds in the Gould Belt The Astrophysical Journal Supplement Series, 194:43 (43pp), 2011 June doi:10.1088/0067-0049/194/2/43 C 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A. THE SPITZER SURVEY OF INTERSTELLAR CLOUDS IN THE GOULD BELT. III. A MULTI-WAVELENGTH VIEW OF CORONA AUSTRALIS Dawn E. Peterson1, Alessio Caratti o Garatti2, Tyler L. Bourke1, Jan Forbrich1, Robert A. Gutermuth3,4, Jes K. Jørgensen5, Lori E. Allen6, Brian M. Patten1, Michael M. Dunham7, Paul M. Harvey7, Bruno Mer´ın8, Nicholas L. Chapman9, Lucas A. Cieza10, Tracy L. Huard11, Claudia Knez11, Brian Prager11, and Neal J. Evans II7 1 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA; [email protected] 2 Dublin Institute for Advanced Studies, Dublin 2, Ireland 3 Five College Astronomy Department, Smith College, Northampton, MA 01063, USA 4 Department of Astronomy, University of Massachusetts, Amherst, MA 01002, USA 5 Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, DK-1350 Copenhagen K., Denmark 6 National Optical Astronomy Observatory, Tucson, AZ 85719, USA 7 Department of Astronomy, University of Texas at Austin, Austin, TX 78712-0259, USA 8 Herschel Science Centre, European Space Astronomy Centre (ESA), 28691 Villanueva de la Canada,˜ Madrid, Spain 9 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA 10 Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA 11 Department of Astronomy, University of Maryland, College Park, MD 20742, USA Received 2010 September 15; accepted 2011 April 8; published 2011 June 1 ABSTRACT We present Spitzer Space Telescope IRAC and MIPS observations of a 0.85 deg2 field including the Corona Australis (CrA) star-forming region. At a distance of 130 pc, CrA is one of the closest regions known to be actively forming stars, particularly within its embedded association, the Coronet. Using the Spitzer data, we identify 51 young stellar objects (YSOs) in CrA which include sources in the well-studied Coronet cluster as well as sources distributed throughout the molecular cloud. Twelve of the YSOs discussed are new candidates, one of which is located in the Coronet. Known YSOs retrieved from the literature are also added to the list, and a total of 116 candidate YSOs −1 in CrA are compiled. Based on these YSO candidates, the star formation rate is computed to be 12 M Myr , similar to that of the Lupus clouds. A clustering analysis was also performed, finding that the main cluster core, consisting of 68 members, is elongated (having an aspect ratio of 2.36), with a circular radius of 0.59 pc and mean −2 surface density of 150 pc . In addition, we analyze outflows and jets in CrA by means of new CO and H2 data. We present 1.3 mm interferometric continuum observations made with the Submillimeter Array (SMA) covering R CrA, IRS 5, IRS 7, and IRAS 18595-3712 (IRAS 32). We also present multi-epoch H2 maps and detect jets and outflows, study their proper motions, and identify exciting sources. The Spitzer and ISAAC/VLT observations of IRAS 32 show a bipolar precessing jet, which drives a CO(2–1) outflow detected in the SMA observations. There is also clear evidence for a parsec-scale precessing outflow, which is east–west oriented and originates in the SMA 2 region and likely driven by SMA 2 or IRS 7A. Key words: infrared: general – ISM: clouds – ISM: individual objects (Corona Australis) – ISM: jets and outflows – stars: formation – stars: pre-main sequence Online-only material: color figures 1. INTRODUCTION indicated no velocity gradient. Loren (1979) interpreted this to mean that the elongation is not due to contraction along the The Gould Belt Spitzer Legacy program is a GO-4 program rotational axis. However, Harju et al. (1993) argued that the designed to extend the earlier Spitzer Cores to Disks (c2d; Evans Loren (1979) data were not sufficient, and suggest from their et al. 2003, 2009) program, thereby completing a census of star- own C18O observations that the R CrA core is, in fact, a forming regions within 500 pc. The Gould Belt is a band of stars fragmented disk, explaining the observed elongation along the and molecular clouds located within ∼20◦ of the Galactic Plane major axis. It is somewhat surprising that CrA is not associated (Herschel 1847; Gould 1879). Although, at a declination of with the Gould Belt, considering its close distance of 130 pc12; approximately −40◦, Corona Australis (CrA) is not technically Mamajek & Feigelson (2001) argue that instead it formed as part within the Gould Belt, it is discussed in this paper as part of of expanding Sco-Cen superbubbles, specifically Loop I, citing the survey. We present an extensive study of the entire Corona evidence from the Harju et al. (1993) millimeter observations, Australis star-forming region, investigating the overall young and radio observations from Cappa de Nicolau & Poppel (1991). population, its spatial distribution along the molecular cloud, Studies from the literature have mainly focused on R CrA, and the young stellar object (YSO) outflows. the brightest star in the cluster, the Coronet region, and its Rossano (1978) used star counts to create an extinction population. The variability of the nebula surrounding the Herbig map, and identified five clouds in CrA, named clouds A–E, Ae star, R CrA, has been known since the early 1900s (Knox noting that CrA is highly elongated, oriented nearly east to Shaw 1916; Reynolds 1916). Many years later, the two variable west in the sky. Cloud A is in the west, and it is this cloud 12 which corresponds to the R CrA/Coronet region. Large-scale The distance to CrA is based on measurements to several stars, ranging from 85 to 190 pc. A comprehensive summary of the various measurements CO mapping by Loren (1979) also shows this elongation, but can be found in Neuhauser¨ & Forbrich (2008); throughout this paper, we use their high spatial resolution observations of the velocity field their suggested distance of 130 pc. 1 The Astrophysical Journal Supplement Series, 194:43 (43pp), 2011 June Peterson et al. stars R CrA and T CrA were identified by Herbig (1960) Table 1 to be young, and he then concluded that the associated stars Spitzer Observations of CrA should also be young. This prompted an interest in studying the Instrument AOR ID PID Observation Date R CrA region, and in 1973, the first major optical and infrared IRAC 0003650816 6 2004 Apr 20 study of the main stars near R CrA was conducted, finding a 0017672960 30784 2006 Sep 25 total of 11 stars in the young stellar group: TY CrA, S CrA, 0017673472 30784 2006 Sep 25 T CrA, R CrA, DG CrA, VV CrA, KS-15, HR 7169, HR 7170, 0027041280 30574 2008 May 10 Anon 1, and Anon 2 (Knacke et al. 1973). The following year, MIPS 0003664640 6 2004 Apr 11 IRS 1 was suggested by Strom et al. (1974)tobethedriving 0017673216 30784 2007 May 30 source for the Herbig-Haro (HH) object, HH 100. Subsequent 0017673728 30784 2007 May 29 infrared observations were made by many groups (Glass & 0027042816 30574 2008 Oct 23 Penston 1975;Vrbaetal.1976a; Taylor & Storey 1984; Wilking et al. 1986)aswellasHα observations (Marraco & Rydgren 1981) and emission-line observations (Graham 1993). These seem to be driven by YSOs inside it or in its outskirts. A few were followed by early X-ray (Walter 1986; Koyama et al. more HH objects are positioned close to HH100-IR (IRS 1), 1996; Neuhauser¨ & Preibisch 1997; Walter et al. 1997; Patten S CrA, VV CrA and IRAS 18595-3712 (IRAS 32), which seem 1998), radio (Brown 1987; Cappa de Nicolau & Poppel 1991), to drive outflows as well. On the other hand, there are very few millimeter (Harju et al. 1993), and far-infrared studies (Wilking and sparse studies on H2 jets and outflows in CrA (see, e.g., et al. 1992, who first mentioned IRAS 32). Wilking et al. 1990; Gredel 1994; Davis et al. 1999; Caratti Neuhauser¨ & Forbrich (2008) have recently reviewed the o Garatti et al. 2006). In these papers, the H2 counterparts of literature on the entire Corona Australis star-forming region, HH 99, 100, 101 and 104 were identified and studied, and a few although many of the studies cover only a subset of the region new jets in the Coronet were detected (Caratti o Garatti et al. which we include here as part of our Spitzer IRAC and MIPS 2006). Davis et al. (2010) cataloged five molecular hydrogen study. The most relevant recent studies include: deep infrared objects (MHOs, MHO 2000–2004), but so far, an extensive H2 observations (Wilking et al. 1997; Haas et al. 2008), millimeter map of the region has not been made. Thus, a complete census and submillimeter observations (Chini et al. 2003; Groppi et al. of outflows and their driving sources is lacking. 2004; Nutter et al. 2005) including Submillimeter Array (SMA) We present Spitzer observations of a 0.85 deg2 region in observations (Groppi et al. 2007), mid-infrared observations the Corona Australis molecular cloud, identifying the Spitzer- with the Infrared Space Observatory (ISO;Olofssonetal.1999), selected YSOs distributed throughout the cloud as well as the and a series of papers focusing on Chandra X-ray studies of outflows and their driving sources. This study includes infrared the region (Forbrich et al. 2006, 2007; Forbrich & Preibisch imaging of a much larger portion of the molecular cloud than 2007). Finally, some spectroscopic work has been done to many previous studies have included. In Section 2, we discuss determine association memberships (Patten 1998; Nisini et al.
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