Protostars, multiplicity, and disk evolution in the Corona Australis region: aHerschelGould Belt Study

Abstract

Context. The CrA region and the Coronet cluster form a nearby (138 pc), young (1−2 Myr) star-forming region that hosts a moderate population of Class I, II, and III objects. Aims. We study the structure of the cluster and the properties of the protostars and protoplanetary disks in the region. Methods. We present Herschel PACS photometry at 100 and 160 μm, obtained as part of the Herschel Gould Belt Survey. The Herschel maps reveal the cluster members within the cloud with high sensitivity and high dynamic range. Results. Many of the cluster members are detected, including some embedded, very low-mass objects, several protostars (some of them extended), and substantial emission from the surrounding molecular cloud. Herschel also reveals some striking structures, such as bright filaments around the IRS 5 protostar complex and a bubble-shaped rim associated with the Class I object IRS 2. The disks around the Class II objects display a wide range of mid-and far-IR excesses consistent with different disk structures. We have modeled the disks with the RADMC radiative transfer code to quantify their properties. Some of them are consistent with flared, massive, relatively primordial disks (S CrA, T CrA). Others display significant evidence for inside-out evolution, consistent with the presence of inner holes/gaps (G-85, G-87). Finally, we found disks with a dramatic small dust depletion (G-1, HBC 677) that, in some cases, could be related to truncation or to the presence of large gaps in a flared disk (CrA-159). The derived masses for the disks around the low-mass stars are found to be below the typical values in Taurus, in agreement with previous Spitzer observations. Conclusions. The Coronet cluster presents itself as an interesting compact region that contains both young protostars and very evolved disks. The Herschel data provide sufficient spatial resolution to detect small-scale details, such as filamentary structures or spiral arms associated with multiple star formation. The disks around the cluster members range from massive, flared primordial disks to disks with substantial small dust grain depletion or with evidence of inside-out evolution. This results in an interesting mixture of objects for a young and presumably coevally formed cluster. Given the high degree of multiplicity and interactions observed among the protostars in the region, the diversity of disks may be a consequence of the early star formation history, which should also be taken into account when studying the disk properties in similar sparsely populated clusters.

The low-mass stellar population in the young cluster Tr 37

“…213751210+572436151, 213809997+572352782). This is similar to other disks in the Coronet cluster (CrA-159 and HBC 677; Sicilia-Aguilar et al 2013). Further observations at longer wavelengths are needed to clarify the total dust content and other special structures that could affect their morphology, like truncation or gaps at larger radii.…”

“…Various physical processes can be invoked for disk removal, including grain growth, photoevaporation, and planet formation. In addition, other external parameters may also contribute to define the path followed by a dispersing disk, such as age, stellar mass, stellar and planetary companions, initial conditions, cluster environment, crowdedness in the star-forming region, and angular momentum of the collapsing core (Hartmann et al 2006;Bouwman et al 2006;Alexander & Armitage 2009;Fang et al 2013a;Sicilia-Aguilar et al 2013;Dullemond et al 2006). Further processes (ejection in multiple systems, photo-erosion of cores by massive nearby stars; Bate et al 2005Bate et al , 2012Whitworth & Zinnecker 2004) may also play a role in the formation of lowmass systems.…”

Probing the effects of external irradiation on low-mass protostars through unbiased line surveys

“…However, VV CrA is a fairly luminous protostar, with a higher flux at 5.8 µm than R CrA (Peterson et al 2011). Using 2MASS, Spitzer, IRAS, PACS, and SCUBA data of VV CrA (Sicilia-Aguilar et al 2013, and references therein), we estimate the bolometric luminosity of the source to 13 L , which is not sufficient to explain the measured H 2 CO temperature. However, by the use of the Robitaille database of SED models for YSOs (Robitaille et al 2006) and their online 3 fitting tool (Robitaille et al 2007), we find that the best matches to the SED are protostellar models with luminosities 40 L .…”

A network of filaments detected byHerschelin the Serpens core

“…A characteristic filamentary structure consists of a main filament with some subfilaments converging on it. This is the case in low-mass star-forming regions (e.g., the B213 filament in Taurus or the Corona Australis region; Palmeirim et al 2013;Sicilia-Aguilar et al 2013) and in high-mass starforming regions (e.g., the DR21 ridge and filaments in Cygnus; Hennemann et al 2012).…”