New members of the Lupus I cloud based on Gaia astrometry Physical and accretion properties from X-Shooter spectra
F. Z. Majidi, J. M. Alcala', A. Frasca, S. Desidera, C. F. Manara, G. Beccari, V. D'Orazi, A. Bayo, K. Biazzo, R. Claudi, E. Covino, G. Mantovan, M. Montalto, D… 展开作者
F. Z. Majidi, J. M. Alcala', A. Frasca, S. Desidera, C. F. Manara, G. Beccari, V. D'Orazi, A. Bayo, K. Biazzo, R. Claudi, E. Covino, G. Mantovan, M. Montalto, D. Nardiello, G. Piotto, E. Rigliaco
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20 pages, 15 Tables, 13 Figures, accepted for publication in A&A
We characterize twelve young stellar objects (YSOs) located in the Lupus I region, spatially overlapping with the Upper Centaurus Lupus (UCL) sub-stellar association. The aim of this study is to understand whether the Lupus I cloud has more members than what has been claimed so far in the literature and gain a deeper insight into the global properties of the region. We selected our targets using Gaia DR2 catalog, based on their consistent kinematic properties with the Lupus I bona fide members. In our sample of twelve YSOs observed by X-Shooter, we identified ten Lupus I members. We could not determine the membership status of two of our targets, namely Gaia DR2 6014269268967059840 and 2MASS J15361110-3444473 due to technical issues. We found out that four of our targets are accretors, among them 2MASS J15551027-3455045, with a mass of ~0.03 M_Sun, is one of the least massive accretors in the Lupus complex to date. Several of our targets (including accretors) are formed in-situ and off-cloud with respect to the main filaments of Lupus I, hence, our study may hint that there are diffused populations of M-dwarfs around Lupus I main filaments. In this context, we would like to emphasize that our kinematic analysis with Gaia catalogs played a key role in identifying the new members of the Lupus I cloud.
We present the results of a study of the stellar and accretion properties of the (almost) complete sample of class II and transitional YSOs in the Lupus I, II, III and IV clouds, based on spectroscopic data acquired with the VLT/X-Shooter spectrograph. Our study combines the dataset from our previous work with new observations of 55 additional objects. We have investigated 92 YSO candidates in total, 11 of which have been definitely identified with giant stars unrelated to Lupus. The stellar and accretion properties of the 81 bona fide YSOs, which represent more than 90% of the whole class~II …
We present the analysis of 34 new VLT/X-Shooter spectra of young stellar objects in the Chamaeleon I star forming region, together with four more spectra of stars in Taurus and two in Chamaeleon II. The broad wavelength coverage and accurate flux calibration of our spectra allow us to estimate stellar and accretion parameters for our targets by fitting the photospheric and accretion continuum emission from the Balmer continuum down to 700 nm. The dependence of accretion with stellar properties for this sample is consistent with previous results from the literature. The accretion rates for tran…
A homogeneous determination of basic stellar parameters of young stellar object (YSO) candidates is needed to confirm their evolutionary stage, membership to star forming regions (SFRs), and to get reliable values of the quantities related to chromospheric activity and accretion. We used the code ROTFIT and synthetic BT-Settl spectra for the determination of the atmospheric parameters (Teff and logg), the veiling, the radial (RV) and projected rotational velocity (vsini), from X-Shooter spectra of 102 YSO candidates in the Lupus SFR. We have shown that 13 candidates can be rejected as Lupus me…
With the purpose of performing a homogeneous determination of elemental abundances for members of the Lupus T association, we analyzed three chemical elements: lithium, iron, and barium. The aims were: to derive the Li abundance for ~90% of known class II stars in the Lupus I, II, III, IV clouds; to perform chemical tagging of a region where few Fe abundance measurements have been obtained in the past, and no determination of the Ba content has been done up to now. We also investigated possible Ba enhancement, as this element has become increasingly interesting in the last years following the …
We present X-Shooter/VLT observations of a sample of 36 accreting low-mass stellar and sub-stellar objects (YSOs) in the Lupus star forming region, spanning a range in mass from ~0.03 to ~1.2Msun, but mostly with 0.1Msun < Mstar < 0.5Msun. Our aim is twofold: firstly, analyse the relationship between excess-continuum and line emission accretion diagnostics, and, secondly, to investigate the accretion properties in terms of the physical properties of the central object. The accretion luminosity (Lacc), and from it the accretion rate (Macc), is derived by modelling the excess emission, from the …
Planet formation is one explanation for the partial clearing of dust observed in the disks of some T Tauri stars. Indeed studies using state-of-the-art high angular resolution techniques have very recently begun to observe planetary companions in these so-called transitional disks. The goal of this work is to use spectra of the transitional disk object LkCa 15 obtained with X-Shooter on the Very Large Telescope to investigate the possibility of using spectro-astrometry to detect planetary companions to T Tauri stars. It is argued that an accreting planet should contribute to the total emission…
I have used high-precision photometry and astrometry from the second data release of the Gaia mission to perform a survey for young stars associated with the Lupus clouds, which have distances of ~160 pc and reside within the Sco-Cen OB association. The Gaia data have made it possible to distinguish Lupus members from most of the stars in other groups in Sco-Cen that overlap with the Lupus clouds, which have contaminated previous surveys. The new catalog of candidate Lupus members should be complete for spectral types earlier than M7 at A_K<0.2 within fields encompassing clouds 1--4. I have us…
Previous star formation studies have, out of necessity, often defined a population of young stars confined to the proximity of a molecular cloud. Gaia allows us to examine a wider, three-dimensional structure of nearby star forming regions, leading to a new understanding of their history. We present a wide-area survey covering 494 square degrees of the Lupus complex, a prototypical low-mass star forming region. Our survey includes all known molecular clouds in this region as well as parts of the Upper Scorpius (US) and Upper Centaurus Lupus (UCL) groups of the Sco-Cen complex. We combine Gaia …
We have analysed the [OI]6300 A line in a sample of 131 young stars with discs in the Lupus, Chamaeleon and signa Orionis star forming regions, observed with the X-shooter spectrograph at VLT. The stars have mass accretion rates spanning from 10^{-12} to 10^{-7} Mo/yr. The line profile was deconvolved into a low velocity component (LVC, < 40 km/s) and a high velocity component (HVC, > 40 km/s ), originating from slow winds and high velocity jets, respectively. The LVC is by far the most frequent component, with a detection rate of 77%, while only 30% of sources have a HVC. The [OI]6300 luminos…
Extensive surveys of star-forming regions with Spitzer have revealed populations of disk-bearing young stellar objects. These have provided crucial constraints, such as the timescale of dispersal of protoplanetary disks, obtained by carefully combining infrared data with spectroscopic or X-ray data. While observations in various regions agree with the general trend of decreasing disk fraction with age, the Lupus V and VI regions appeared to have been at odds, having an extremely low disk fraction. Here we show, using the recent Gaia data release 2 (DR2), that these extremely low disk fractions…
The He I 1 micron line is a high excitation line which allows us to probe the innermost regions of protostellar disks, and to trace both accreting and outflowing material. We use X-Shooter observations of a sample of 107 young stars in the Lupus (1-3 Myr) and Upper Scorpius (5-10 Myr) star-forming regions to search for correlations between the line properties, as well as the disk inclination and accretion luminosity. We identified eight distinct profile types in the sample. We fitted Gaussian curves to the line features to measure the maximum velocities traced in absorption, the full-width hal…
The mass accretion rate is a crucial parameter for the study of the evolution of accretion discs around young low-mass stellar and substellar objects (YSOs). We revisit the case of MYLup, an object where VLT/X-Shooter data suggested a negligible mass accretion rate, and show it to be accreting on a level similar to other ClassII YSOs in Lupus based on HST observations. In our HST-COS and -STIS spectra, we find many emission lines, as well as substantial FUV continuum excess emission, which can be ascribed to active accretion. The total luminosity of the CIV 1549A doublet is 4.1$\times10^{-4}$ …
We present the first pilot study of jets from young stars conducted with X-shooter, on ESO/VLT. As it offers simultaneous, high quality spectra in the range 300-2500 nm X-shooter is uniquely important for spectral diagnostics in jet studies. We chose to probe the accretion/ejection mechanisms at low stellar masses examining two targets with well resolved continuous jets lying on the plane of the sky, ESO-HA 574 in Chamaleon I, and Par-Lup3-4 in Lupus III. The mass of the latter is close to the sub-stellar boundary (Mstar=0.13 Msun). A large number of emission lines probing regions of different…
Determining the mechanisms that drive the evolution of protoplanetary disks is a necessary step to understand how planets form. Here we measured the mass accretion rate for young stellar objects at age >5 Myr, a critical test for the current models of disk evolution. We present the analysis of the spectra of 36 targets in the ~5-10 Myr old Upper Scorpius region for which disk masses were measured with ALMA. We find that the mass accretion rates in this sample of old but still survived disks are similarly high as those of the younger (<3 Myr old) star-forming regions of Lupus and Cha I, when co…
We analyzed X-Shooter/VLT spectra of 24 ClassIII sources from three nearby star-forming regions (sigmaOrionis, LupusIII, and TWHya). We determined the effective temperature, surface gravity, rotational velocity, and radial velocity by comparing the observed spectra with synthetic BT-Settl model spectra. We investigated in detail the emission lines emerging from the stellar chromospheres and combined these data with archival X-ray data to allow for a comparison between chromospheric and coronal emissions. Both X-ray and Halpha luminosity as measured in terms of the bolometric luminosity are ind…
Disks around T Tauri stars are known to lose mass, as best shown by the profiles of forbidden emission lines of low ionization species. At least two separate kinematic components have been identified, one characterised by velocity shifts of tens to hundreds km/s (HVC) and one with much lower velocity of few km/s (LVC). The HVC are convincingly associated to the emission of jets, but the origin of the LVC is still unknown. In this paper we analyze the forbidden line spectrum of a sample of 44 mostly low mass young stars in Lupus and $σ$-Ori observed with the X-Shooter ESO spectrometer. We detec…
X-shooter survey Across Regions and Ages to probe Disk Evolution (ARADE): Accretion properties in Orion A and their relation with disk masses
European Southern Observatory（欧洲南方天文台）；Trinity College Dublin, the University of Dublin（都柏林三一学院，都柏林大学）；Space Research Institute, Austrian Academy of Sciences（奥地利科学院空间研究所）；Istituto Nazionale di Astrofisica (INAF)—Osservatorio Astronomico di Palermo（意大利国家天体物理研究所（INAF）—巴勒莫天文台）；Maynooth University Department of Physics, National University of Ireland Maynooth（梅努斯大学物理系，爱尔兰国立大学梅努斯分校）；University College Dublin（都柏林大学学院）；Ludwig-Maximilians-Universität München（慕尼黑大学）；Max-Planck-Institut für Extraterrestrische Physik（马克斯·普朗克地外物理学研究所）
We present 27 new L subdwarfs and classify five of them as esdL and 22 as sdL. Our L subdwarf candidates were selected with the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Spectroscopic follow-up was carried out primarily with the OSIRIS spectrograph on the Gran Telescopio Canarias. Some of these new objects were followed up with the X-shooter instrument on the Very Large Telescope. We studied the photometric properties of the population of known L subdwarfs using colour-spectral type diagrams and colour-colour diagrams, by comparison with L dwarfs and main-sequence stars, and…
X-Shooter survey of disk accretion in Upper Scorpius II. A lack of correlation between accretion rates and disk properties
University College Dublin (UCD)（都柏林大学学院）；European Southern Observatory（欧洲南方天文台）；School of Cosmic Physics, Dublin Institute for Advanced Studies（都柏林高等研究院宇宙物理学院）；Department of Physics, Maynooth University（梅努斯大学物理系）；Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）；Institue of Astronomy, University of Cambridge（剑桥大学天文研究所）；INAF-Osservatorio Astronomico di Capodimonte（意大利国家天体物理研究所卡波迪蒙特天文台）；School of Physics, Trinity College Dublin, the University of Dublin（都柏林三一学院物理学院，都柏林大学）；Joint ALMA Observatory（ALMA联合天文台）；Dipartimento di Fisica, Università degli Studi di Milano（米兰大学物理系）
A relation between the mass accretion rate onto the central young star and the mass of the surrounding protoplanetary disk has long been theoretically predicted and observationally sought. For the first time, we have accurately and homogeneously determined the photospheric parameters, mass accretion rate, and disk mass for an essentially complete sample of young stars with disks in the Lupus clouds. Our work combines the results of surveys conducted with VLT/X-Shooter and ALMA. With this dataset we are able to test a basic prediction of viscous accretion theory, the existence of a linear relat…
