High Spatial Resolution Observations of Two Young Protostars in the R Corona Australis Region

Groppi, Christopher; Hunter, T. R.; Blundell, R.; Sandell, G.

doi:10.1086/521875

Cited by 37 publications

(132 citation statements)

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“…The membership count is probably close to complete for spectral types between B9 and M6, considering that the cluster has been observed in the optical, X ray, IR, and submillimeter (e.g. López-Martí et al 2005Groppi et al 2004Groppi et al , 2007Peterson et al 2011;Sicilia-Aguilar et al 2008, 2011a. Taking into account only the number of stars and not their mass, we arrive to a stellar density of about 3000 stars/pc 3 .…”

Section: What Drives Disk Evolution and Dispersal In Tr 37? Clues Fromentioning

confidence: 67%

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

Sicilia‐Aguilar

Kim

Соболев

et al. 2013

A&A

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Aims. We present a study of accretion and protoplanetary disks around M-type stars in the 4 Myr-old cluster Tr 37. With a well-studied solar-type population, Tr 37 is a benchmark for disk evolution. Methods. We used low-resolution spectroscopy to identify and classify 141 members (78 new ones) and 64 probable members, mostly M-type stars. Hα emission provides information about accretion. Optical, 2MASS, Spitzer, and WISE data are used to trace the spectral energy distributions (SEDs) and search for disks. We construct radiative transfer models to explore the structures of fulldisks, pre-transition, transition, and dust-depleted disks. Results. Including the new members and the known solar-type stars, we confirm that a substantial fraction (∼2/5) of disks show signs of evolution, either as radial dust evolution (transition/pre-transition disks) or as a more global evolution (with low small-dust masses, dust settling, and weak/absent accretion signatures). Accretion is strongly dependent on the SED type. About half of the transition objects are consistent with no accretion, and dust-depleted disks have weak (or undetectable) accretion signatures, especially among M-type stars. Conclusions. The analysis of accretion and disk structure suggests a parallel evolution of dust and gas. We find several distinct classes of evolved disks, based on SED type and accretion status, pointing to different disk dispersal mechanisms and probably different evolutionary paths. Dust depletion and opening of inner holes appear to be independent processes: most transition disks are not dust-depleted, and most dust-depleted disks do not require inner holes. The differences in disk structure between M-type and solar-type stars in Tr 37 (4 Myr old) are not as remarkable as in the young, sparse, Coronet cluster (1−2 Myr old), suggesting that other factors, like the environment/interactions in each cluster, are likely to play an important role in the disk evolution and dispersal. Finally, we also find some evidence of clumpy star formation or mini-clusters within Tr 37.

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Section: What Drives Disk Evolution and Dispersal In Tr 37? Clues Fromentioning

confidence: 67%

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

Sicilia‐Aguilar

Kim

Соболев

et al. 2013

A&A

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“…Therefore, we fixed the parameters H 0 and R 0 to the typical values of H 0 = 0.1 AU and R 0 = 10 AU. As total disk mass, we assume M disk = 0.012 M (Groppi et al 2007) with a standard gas-to-dust ratio of 100:1. Besides the luminosity L which is incident on the disk rim, the most sensitive parameter in the IN05 model is .…”

Section: Curved Rim Modelmentioning

confidence: 99%

Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R Coronae Austrinae

Kraus¹,

Hofmann²,

Malbet

et al. 2009

A&A

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Context. Unveiling the structure of the disks around intermediate-mass pre-main-sequence stars (Herbig Ae/Be stars) is essential for our understanding of the star and planet formation process. In particular, models predict that in the innermost AU around the star, the dust disk forms a "puffed-up" inner rim, which should result in a strongly asymmetric brightness distribution for disks seen under intermediate inclination.Aims. Our aim is to constrain the sub-AU geometry of the inner disk around the Herbig Ae star R CrA and search for the predicted asymmetries. Methods. Using the VLTI/AMBER long-baseline interferometer, we obtained 24 near-infrared (H-and K-band) spectrointerferometric observations on R CrA. Observing with three telescopes in a linear array configuration, each data set samples three equally spaced points in the visibility function, providing direct information about the radial intensity profile. In addition, the observations cover a wide position angle range (∼97 • ), also probing the position angle dependence of the source brightness distribution. Results. In the derived visibility function, we detect the signatures of an extended (Gaussian FWHM ∼ 25 mas) and a compact component (Gaussian FWHM ∼ 5.8 mas), with the compact component contributing about two-thirds of the total flux (both in H-and K-band). The brightness distribution is highly asymmetric, as indicated by the strong closure phases (up to ∼40 • ) and the detected position angle dependence of the visibilities and closure phases. To interpret these asymmetries, we employ various geometric as well as physical models, including a binary model, a skewed ring model, and a puffed-up inner rim model with a vertical or curved rim shape. For the binary and vertical rim model, no acceptable fits could be obtained. On the other hand, the skewed ring model and the curved puffed-up inner rim model allow us to simultaneously reproduce the measured visibilities and closure phases. From these models we derive the location of the dust sublimation radius (∼0.4 AU), the disk inclination angle (∼35 • ), and a north-south disk orientation (PA ∼ 180−190 • ). Our curved puffed-up rim model can reproduce reasonably well the interferometric observables and the SED and suggests a luminosity of ∼29 L and the presence of relatively large ( > ∼ 1.2 μm) Silicate dust grains. Our study also reveals discrepancies between the measured interferometric observables and the puffed-up inner rim models, providing important constraints for future refinements of these theoretical models. Perpendicular to the disk, two bow shock-like structures appear in the associated reflection nebula NGC 6729, suggesting that the detected sub-AU size disk is the driving engine of a large-scale outflow. Conclusions. Detecting, for the first time, strong non-localized asymmetries in the inner regions of a Herbig Ae disk, our study supports the existence of a puffed-up inner rim in YSO disks.

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“…The locations of the sources are shown on Spitzer 4.5 μm (Peterson et al 2011) image data, with Herschel 70 μm (Lindberg et al, in prep. ) and SMA 1.3 mm (Chen & Arce 2010) continuum A&A 548, A24 (2012) Peterson et al (2011), (2) Groppi et al (2007), (3) Choi et al (2008), (4) Miettinen et al (2008), (5) Forbrich et al (2006), (6) Nutter et al (2005), (7) Chen & Arce (2010). (b) The coordinates come from SMA and Spitzer continuum reported in Peterson et al (2011).…”

Section: Introductionmentioning

confidence: 99%

“…Nutter et al (2005) studied the region in submillimetre, and detected three peaks within the region around IRS7: SMM 1B coinciding with IRS7B, SMM 1C coinciding with Brown 9, and SMM 1A south of IRS7B. Studies of millimetre continuum emission showed three compact sources, IRS7B (SMM 1B), SMM 1C, and SMM 2 (Groppi et al 2007;Chen & Arce 2010;Peterson et al 2011). Groppi et al (2007) used Spitzer IRAC data, SCUBA 450 μm and 850 μm, and SMA 1.1 mm data to study the SEDs of IRS7B (SMA1) and SMM 1C (SMA2; not detected in the Spitzer data).…”

Section: Introductionmentioning

confidence: 99%

“…Studies of millimetre continuum emission showed three compact sources, IRS7B (SMM 1B), SMM 1C, and SMM 2 (Groppi et al 2007;Chen & Arce 2010;Peterson et al 2011). Groppi et al (2007) used Spitzer IRAC data, SCUBA 450 μm and 850 μm, and SMA 1.1 mm data to study the SEDs of IRS7B (SMA1) and SMM 1C (SMA2; not detected in the Spitzer data). They suggested that IRS7B is a transitional Class 0/I object, whereas SMM 1C likely is a Class 0 source.…”

Section: Introductionmentioning

confidence: 99%

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Strong irradiation of protostellar cores in Corona Australis

Lindberg

Jørgensen

2012

A&A

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Context. The importance of the physical environment in the evolution of newly formed low-mass stars remains an open question. In particular, radiation from nearby more massive stars may affect both the physical and chemical structure of these kinds of young stars. Aims. We constrain the physical characteristics of a group of embedded low-mass protostars in Corona Australis in the vicinity of the young luminous Herbig Be star R CrA. Methods. Millimetre wavelength maps of molecular line and continuum emission towards the low-mass star forming region IRS7 near R CrA from the Submillimeter Array (SMA) and Atacama Pathfinder Experiment (APEX) are presented. The maps show the distribution of 18 lines from 7 species (H 2 CO, CH 3 OH, HC 3 N, c-C 3 H 2 , HCN, CN and SiO) on scales from 3 to 60 (400-8000 AU). Using a set of H 2 CO lines, we estimate the temperatures and column densities in the region using both LTE and non-LTE methods. The results are compared with 1-D radiative transfer modelling of the protostellar cores. These models constrain which properties of the central source, protostellar envelope, and surrounding radiation field can give rise to the observed line and continuum emission. Results. Most of the H 2 CO emission from the regions emerges from two elongated (∼6000 AU long) narrow (<1500 AU) ridges dominating the emission picked up in both interferometric and single-dish measurements. The temperatures inferred from the H 2 CO lines are no less than ∼30 K and more likely 50-60 K, and the line emission peaks are offset by ∼2500 AU from the location of the embedded protostars. These temperatures can not be explained by the heating from the young stellar objects (YSOs) themselves. Irradiation by the nearby Herbig Be star R CrA could, however, explain these high temperatures. The elevated temperatures can in turn impact the physical and chemical characteristics of protostars, in particular, lead to enhanced abundances of typical tracers of photon dominated regions (PDRs) such as seen in single-dish line surveys of embedded protostars in the region.

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High Spatial Resolution Observations of Two Young Protostars in the R Corona Australis Region

Cited by 37 publications

References 36 publications

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

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

Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R Coronae Austrinae

Strong irradiation of protostellar cores in Corona Australis

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