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A search for clustering around Herbig Ae/Be stars - II. Atlas of the observed sources

We present large field infrared images of a sample of 45 Herbig Ae/Be stars. Stellar parameters, such as age and luminosity, have been derived for all of them in a consistent way. The images have been used to identify stellar groups or clusters associated with the Herbig Ae/Be star. The results presented in this paper form the database for a study of clustering around...

ALMA continuum observations of the protoplanetary disk AS 209 - Evidence of multiple gaps opened by a single planet

This paper presents new high angular resolution ALMA 1.3 mm dust continuum observations of the protoplanetary system AS 209 in the Ophiuchus star forming region. The dust continuum emission is characterized by a main central core and two prominent rings at r = 75 au and r = 130 au intervaled by two gaps at r = 62 au and r = 103 au. The two gaps have different widths and depths...

Dust and gas environment of the young embedded cluster IRAS 18511+0146

Context. Since massive and intermediate mass stars form in clusters, a comparative investigation of the environments of the young embedded cluster members can reveal significant information about the conditions under which stars form and evolve.Aims. IRAS 18511+0146 is a young embedded (proto)cluster located at 3.5 kpc surrounding what appears to be an intermediate mass protostar...

The Pillars of Creation revisited with MUSE: gas kinematics and high-mass stellar feedback traced by optical spectroscopy

Integral field unit (IFU) data of the iconic Pillars of Creation in M16 are presented. The ionization structure of the pillars was studied in great detail over almost the entire visible wavelength range, and maps of the relevant physical parameters, e.g. extinction, electron density, electron temperature, line-of-sight velocity of the ionized and neutral gas are shown. In...

Evidence for a correlation between mass accretion rates onto young stars and the mass of their protoplanetary disks

A&A Astronomy & Astrophysics Letter to the Editor C. F. Manara 3 G. Rosotti 1 L. Testi 0 6 7 A. Natta 5 7 J. M. Alcalá 4 J. P. Williams 9 M. Ansdell 9 A. Miotello 8 N. van der Marel 8 9 M. Tazzari

Evidence for a correlation between mass accretion rates onto young stars and the mass of their protoplanetary disks

A&A Astronomy & Astrophysics Letter to the Editor C. F. Manara 3 G. Rosotti 1 L. Testi 0 6 7 A. Natta 5 7 J. M. Alcalá 4 J. P. Williams 9 M. Ansdell 9 A. Miotello 8 N. van der Marel 8 9 M. Tazzari

The sulfur depletion problem: upper limits on the H2S2, HS·2, and S2 gas-phase abundances toward the low-mass warm core IRAS 16293-2422

Context. A fraction of the missing sulfur in dense clouds and circumstellar regions could be in the form of three species not yet detected in the interstellar medium: H2S2, HS.2, and S2 according to experimental simulations performed under astrophysically relevant conditions. These S-S bonded molecules can be formed by the energetic processing of H2S-bearing ice mantles on dust...

Accurate determination of accretion and photospheric parameters in young stellar objects: The case of two candidate old disks in the Orion Nebula Cluster

Context. Current planet formation models are largely based on the observational constraint that protoplanetary disks have a lifetime of ~3 Myr. Recent studies, however, report the existence of pre-main-sequence stars with signatures of accretion (strictly connected with the presence of circumstellar disks) and photometrically determined ages of 30 Myr or more. Aims. Here, we...

Accurate determination of accretion and photospheric parameters in young stellar objects: The case of two candidate old disks in the Orion Nebula Cluster

Context. Current planet formation models are largely based on the observational constraint that protoplanetary disks have a lifetime of ~3 Myr. Recent studies, however, report the existence of pre-main-sequence stars with signatures of accretion (strictly connected with the presence of circumstellar disks) and photometrically determined ages of 30 Myr or more. Aims. Here, we...

X-shooter spectroscopy of young stellar objects - I. Mass accretion rates of low-mass T Tauri stars in σ Orionis

We present high-quality, medium-resolution X-shooter/VLT spectra in the range 300−2500 nm for a sample of 12 very low mass stars in the σ Orionis cluster. The sample includes eight stars with evidence of disks from Spitzer and four without disks, with masses ranging from 0.08 to 0.3 M⊙. The aim of this first paper is to investigate the reliability of the many accretion tracers...

Explaining millimeter-sized particles in brown dwarf disks

, Nature, 377 , 129 Regály, Z. , Juhász , A. , Sándor , Z. , & Dullemond , C. P. 2012 , MNRAS, 419 , 1701 Riaz, B. , Honda , M. , Campins , H. , et al. 2012 , MNRAS, 420 , 2603 Ricci, L. , Testi , L. , Natta ... , A. , et al. 2010a, A &A, 512 , A15 Ricci , L. , Testi , L. , Natta , A. , & Brooks , K. J. 2010b , A &A, 521 , A66 Ricci , L. , Mann , R. K. , Testi , L. , et al. 2011 , A &A, 525 , A81 Ricci , L

The effect of local optically thick regions in the long-wave emission of young circumstellar disks

& Planets V, 783 Regaly , Zs. , Juhasz , A. , Sandor , Zs. , & Dullemond , C. P. 2012 , MNRAS, 419 , 1701 Ricci , L. , Testi , L. , Natta , A. , et al. 2010a, A &A, 512 , A15 Ricci , L. , Testi , L. , Natta ... , A. , & Brooks , K. 2010b , A &A, 521 , A66 Ricci , L. , Mann , R. K. , Testi , L. , et al. 2011a, A &A, 525 , A81 Ricci , L. , Testi , L. , Williams , J. P. , Mann , R. K. , & Birnstiel , T. 2011b

X-shooter spectroscopy of young stellar objects - II. Impact of chromospheric emission on accretion rate estimates

Context. The lack of knowledge of photospheric parameters and the level of chromospheric activity in young low-mass pre-main sequence stars introduces uncertainties when measuring mass accretion rates in accreting (Class II) young stellar objects. A detailed investigation of the effect of chromospheric emission on the estimates of mass accretion rate in young low-mass stars is...

Silicon isotopic abundance toward evolved stars and its application for presolar grains

Aims. Galactic chemical evolution (GCE) is important for understanding the composition of the present-day interstellar medium (ISM) and of our solar system. In this paper, we aim to track the GCE by using the 29Si/30Si ratios in evolved stars and tentatively relate this to presolar grain composition.Methods. We used the APEX telescope to detect thermal SiO isotopologue emission...

The molecular distribution of the IRDC G351.77–0.51

. , van Broekhuizen , F. , Fraser , H. J. , et al. 2005 , ApJ, 621 , L33 Olmi , L. , & Testi , L. 2002 , A &A, 392 , 1053 Ossenkopf , V. , & Henning , T. 1994 , A &A, 291 , 943 Peeters, E. , Martín

Search for starless clumps in the ATLASGAL survey

Context. Understanding massive star formation requires comprehensive knowledge about the initial conditions of this process. The cradles of massive stars are believed to be located in dense and massive molecular clumps.Aims. In this study, we present an unbiased sample of the earliest stages of massive star formation across 20 deg2 of the sky.Methods. Within the region 10° < l...

Variations in the Galactic star formation rate and density thresholds for star formation

The conversion of gas into stars is a fundamental process in astrophysics and cosmology. Stars are known to form from the gravitational collapse of dense clumps in interstellar molecular clouds, and it has been proposed that the resulting star formation rate is proportional to either the amount of mass above a threshold gas surface density, or the gas volume density. These star...

Resolving the molecular environment of super star clusters in Henize 2-10

Context. The rate of star formation both in the Galaxy and in external galaxies should be related to the physical properties of the molecular clouds from which stars form. This is expected for the starbursts found both in irregular galaxies and in some mergers. The dwarf galaxy Henize 2-10 is particularly interesting in this context as it shows a number of newly formed super star...

Accretion in Ophiuchus brown dwarfs: infrared hydrogen line ratios

Context.Mass accretion rate determinations are fundamental for an understanding of the evolution of pre-main sequence star circumstellar disks.Aims.Magnetospheric accretion models are used to derive values of the mass accretion rates in objects of very different properties, from brown dwarfs to intermediate-mass stars; we test the validity of these models in the brown dwarf...