DOCSLIB.ORG

Low Mass T Tauri and Young Brown Dwarf Candidates in the Chamaeleon II Dark Cloud Found by DENIS

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Low Mass T Tauri and Young Brown Dwarf Candidates in the Chamaeleon II Dark Cloud Found by DENIS A&A 379, 208–214 (2001) Astronomy DOI: 10.1051/0004-6361:20011259 & c ESO 2001 Astrophysics Low mass T Tauri and young brown dwarf candidates in the Chamaeleon II dark cloud found by DENIS M. H. Vuong1,?,L.Cambr´esy2, and N. Epchtein1 1 Observatoire de la Cˆote d’Azur, D´epartement Fresnel, 06304 Nice Cedex, France e-mail: [email protected] 2 California Institute of Technology, IPAC/JPL, Pasadena, CA 91109, USA e-mail: [email protected] Received 11 May 2001 / Accepted 5 September 2001 Abstract. We define a sample designed to select low-mass T Tauri stars and young brown dwarfs using DENIS data in the Chamaeleon II molecular cloud. We use a star count method to construct an extinction map of the Chamaeleon II cloud. We select our low-mass T Tauri star and young brown dwarf candidates by their strong infrared color excess in the I − J/J − Ks color-color dereddened diagram. We retain only objects with colors I − J ≥ 2, and spatially distributed in groups around the cloud cores. This provides a sample of 70 stars of which 4 are previously known T Tauri stars. We have carefully checked the reliability of all these objects by visual inspection of the DENIS images. Thanks to the association of the optical I band to the infra-red J and Ks bands in DENIS, we can apply this selection method to all star formation regions observed in the southern hemisphere. We also identify six DENIS sources with X-ray sources detected by ROSAT. Assuming that they are reliable low-mass candidates and using the evolutionary models for low-mass stars, we estimate the age of these sources between 1 Myr and <10 Myr. Key words. ISM: clouds – ISM: dust, extinction – ISM: individual objects: Chamaeleon 1. Introduction pre-main sequence stars may be due to an enhanced dy- namo activity with a coupled process of surface convection The Chamaeleon complex is one of the nearest star- and differential rotation of a star or between a star and formation regions to the Sun (between 160 and 180 pc, the inner disks (e.g. in ρ Oph, Montmerle et al. 2000). Whittet et al. 1997). It consists of three main dark clouds, Millimeter observations such as the detection of CO and designated Chamaeleon (Cha) I, II and III (Schwartz CS lines that reveal gas emission and outflows often al- ≈ 1977). Its relative proximity, high Galactic latitude (b low one to characterise young stellar objects (Olmi et al. − ◦ ∼ 6 17 ) and young age ( 10 yrs) make it an ideal location 1994). to search for low-mass T Tauri stars (TTS) and young Weak line TTS are known as pre-main sequence ob- brown dwarfs. The low-mass population can provide con- jects without a disk and are usually found to be associ- straints on the shape of the initial mass function (by in- ated with X-ray sources. In contrast, classical TTS with vestigating the slope), which is still poorly determined at a circumstellar disk show strong Hα emission and excess low masses (Tinney 1993; M´era et al. 1996). IR emission. Brown dwarfs are low-mass stars (<0.08 M ) Young stellar objects are characterised by their which never reach the reaction of hydrogen fusion. They Hα emission line (Hartigan 1993) and an infrared excess are mainly powered by gravitational energy. Therefore that reveals the presence of circumstellar material in the they are relatively faint objects and can only be de- near infrared (Larson et al. 1998; Oasa et al. 1999; G´omez tected at nearby distances (∼<30 pc). However, young & Kenyon 2001), the mid-infrared (ISO, Persi et al. 2000) brown dwarfs are much more luminous (∼100 times more and the far-infrared (IRAS, Prusti et al. 1992). X-ray than field brown dwarfs). Such young brown dwarfs can observations (ASCA, ROSAT) allow the identification of be found in star-forming regions out to a few 100 pc young stellar objects (Yamauchi et al. 1998; Alcal´aetal. (Neuh¨auser & Comer´on 1999). 2000). The origin of the X-ray emission from the low-mass The Cha II has not been mined as thoroughly as Send offprint requests to:M.H.Vuong, the Cha I cloud. In the Chamaeleon clouds, the pre- e-mail: [email protected] main-sequence stars, mainly TTS, were first discovered by ? Present address: Service d’Astrophysique, CEA Saclay, Schwartz (1977). No brown dwarfs have yet been found in 91191 Gif-sur-Yvette, France the Cha II. Recently, Comer´on et al. (2000) found eleven Article published by EDP Sciences and available at http://www.aanda.org or http://dx.doi.org/10.1051/0004-6361:20011259 M. H. Vuong et al.: Low mass T Tauri and young brown dwarf candidates 209 young brown dwarfs in the Cha I cloud from pointed IR at a radius of 200 before starting to pick up unrelated stars observations. With the advent of large near-IR surveys beyond 1000. Adopting a 200 radius1 assures that all double (DENIS, 2MASS), it is now possible to easily identify entries are removed, which is especially important for the such samples across large regions of the sky. Cambr´esy star count method (see next section). We therefore aver- et al. (1998) have used DENIS data to find young stellar age the positions and fluxes of the stars located <200 from objects in the Cha I cloud. each other. We detect ∼70 000 distinct sources in I and In this paper, we introduce a low-mass star sample in J bands which are used to construct the extinction map the Cha II dark cloud, extracted from the DENIS survey. (Sect. 3.1) and ∼20 000 sources in all 3 bands IJKs. Section 2 describes the observations and the data reduc- tion. In Sect. 3, we construct an extinction map of the Cha II cloud, and present the color-color I − J/J − Ks di- 3. Selection agram used to search for new low-mass members. Finally, Sect. 4 discusses the position of our sources on the color- 3.1. Extinction map of the Cha II cloud magnitude diagram using the evolutionary tracks for low- We construct an extinction map of the Cha II using mass stars as modeled by Baraffe et al. (1998). the star count method developed by Cambr´esy (1999). This method is based on the comparison of local stel- 2. DENIS observations and data reduction lar densities in the absorbed region and a nearby ref- erence area assumed to be free of obscuration. DENIS The observations presented in this paper have been provides stars detected in 2 infrared bands and 1 opti- obtained from the DEep Near Infrared Survey of the cal band. We first need to determine which band is the Southern Sky (DENIS, Epchtein et al. 1997) between 1996 best one to apply this method. The Ks band allows us March and 1998 May at La Silla using the ESO 1 m tele- to probe the dense cores of the cloud but the density con- scope. They cover an area of 2.42◦ × 3.50◦ centered at ◦ 0 00 trast is too small to build an extinction map. We therefore 13h 00m 00s in right ascension (J2000) and −76 45 00 in use the I and J bands to construct the extinction map. declination (J2000) in three bands I(0.8 µm), J(1.25 µm) By requiring that the stars be detected in both bands, and Ks(2.15 µm). Limiting magnitudes at 3σ are 18, 16 we can eliminate spurious sources. But the simultaneous and 13.5 in I, J and Ks bands. It consists of 24 strips use of I and J bands introduces a bias which begins each containing 180 images of 120 × 120 taken at constant at AV =[(I − J)limit − (I − J)average]/[<AI/AV > − right ascension along an arc of 30◦ in declination. There <AJ /AV >]. Figure 2 shows that the average color of the is a 20 overlap between each two adjacent images. For the stars (I − J)average = 1. Using the values of <AI /AV > adjacent strips, the overlap is also 20 for the images in and <AJ /AV > from Cardelli et al. (1989), we find that the north. The overlap becomes more important when we the bias begins at AV =(2− 1)/(0.479 − 0.282) = 5. The move to the south by a simple projection effect (this is par- bias can reach 2 mag in the densest cores. As a result, ticularly important for the Chamaeleon complex because fewer stars will be selected with a red color criterion. of its proximity to the South Pole). We use the ∼70 000 sources detected in I and J bands The data reduction took place at the Paris Data to construct the extinction map. We apply a wavelet trans- Analysis Center (PDAC). The source extraction used PSF form algorithm to filter out the noise due to the Poisson fitting. The astrometric calibration was obtained by cross- fluctuations in the star counts (Cambr´esy 1999). We take correlation with the USNO-PMM catalog (Monet et al. into account the decrease of stellar density with latitude 1998). The absolute astrometry is then fixed by the ac- to calibrate the extinction as a function of galactic lati- curacy of this catalog (∼0.500 at 3σ, Deutsch 1999). The tude. The slope of AV (b) is equal to 0 as suggested by the internal accuracy of DENIS observations derived from the morphological similarity with the 13CO map of Mizuno ∼ 00 overlapping regions of adjacent images is 0.35 (3σ).
Load more

Recommended publications
  • Spectroscopic Analysis of Accretion/Ejection Signatures in the Herbig Ae/Be Stars HD 261941 and V590 Mon T Moura, S
    Spectroscopic analysis of accretion/ejection signatures in the Herbig Ae/Be stars HD 261941 and V590 Mon T Moura, S. Alencar, A. Sousa, E. Alecian, Y. Lebreton To cite this version: T Moura, S. Alencar, A. Sousa, E. Alecian, Y. Lebreton. Spectroscopic analysis of accretion/ejection signatures in the Herbig Ae/Be stars HD 261941 and V590 Mon. Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2020, 494 (3), pp.3512-3535. 10.1093/mnras/staa695. hal-02523038 HAL Id: hal-02523038 https://hal.archives-ouvertes.fr/hal-02523038 Submitted on 16 May 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. MNRAS 000,1–24 (2019) Preprint 27 February 2020 Compiled using MNRAS LATEX style file v3.0 Spectroscopic analysis of accretion/ejection signatures in the Herbig Ae/Be stars HD 261941 and V590 Mon T. Moura1?, S. H. P. Alencar1, A. P. Sousa1;2, E. Alecian2, Y. Lebreton3;4 1Universidade Federal de Minas Gerais, Departamento de Física, Av. Antônio Carlos 6627, 31270-901, Brazil 2Univ. Grenoble Alpes, IPAG, F-38000 Grenoble, France 3LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ.
    [Show full text]
  • XIII Publications, Presentations
    XIII Publications, Presentations 1. Refereed Publications E., Kawamura, A., Nguyen Luong, Q., Sanhueza, P., Kurono, Y.: 2015, The 2014 ALMA Long Baseline Campaign: First Results from Aasi, J., et al. including Fujimoto, M.-K., Hayama, K., Kawamura, High Angular Resolution Observations toward the HL Tau Region, S., Mori, T., Nishida, E., Nishizawa, A.: 2015, Characterization of ApJ, 808, L3. the LIGO detectors during their sixth science run, Classical Quantum ALMA Partnership, et al. including Asaki, Y., Hirota, A., Nakanishi, Gravity, 32, 115012. K., Espada, D., Kameno, S., Sawada, T., Takahashi, S., Ao, Y., Abbott, B. P., et al. including Flaminio, R., LIGO Scientific Hatsukade, B., Matsuda, Y., Iono, D., Kurono, Y.: 2015, The 2014 Collaboration, Virgo Collaboration: 2016, Astrophysical Implications ALMA Long Baseline Campaign: Observations of the Strongly of the Binary Black Hole Merger GW150914, ApJ, 818, L22. Lensed Submillimeter Galaxy HATLAS J090311.6+003906 at z = Abbott, B. P., et al. including Flaminio, R., LIGO Scientific 3.042, ApJ, 808, L4. Collaboration, Virgo Collaboration: 2016, Observation of ALMA Partnership, et al. including Asaki, Y., Hirota, A., Nakanishi, Gravitational Waves from a Binary Black Hole Merger, Phys. Rev. K., Espada, D., Kameno, S., Sawada, T., Takahashi, S., Kurono, Lett., 116, 061102. Y., Tatematsu, K.: 2015, The 2014 ALMA Long Baseline Campaign: Abbott, B. P., et al. including Flaminio, R., LIGO Scientific Observations of Asteroid 3 Juno at 60 Kilometer Resolution, ApJ, Collaboration, Virgo Collaboration: 2016, GW150914: Implications 808, L2. for the Stochastic Gravitational-Wave Background from Binary Black Alonso-Herrero, A., et al. including Imanishi, M.: 2016, A mid-infrared Holes, Phys.
    [Show full text]
  • New Herbig±Haro Objects and Giant Outflows in Orion
    Mon. Not. R. Astron. Soc. 310, 331±354 (1999) New Herbig±Haro objects and giant outflows in Orion S. L. Mader,1 W. J. Zealey,1 Q. A. Parker2 and M. R. W. Masheder3,4 1Department of Engineering Physics, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia 2Anglo-Australian Observatory, Coonabarabran, NSW 2357, Australia 3Department of Physics, University of Bristol, Bristol BS8 1TL 4Netherlands Foundation for Research in Astronomy, PO Box 2, 7990 AA Dwingeloo, the Netherlands Accepted 1999 June 29. Received 1999 May 11; in original form 1998 June 25 ABSTRACT We present the results of a photographic and CCD imaging survey for Herbig±Haro (HH) objects in the L1630 and L1641 giant molecular clouds in Orion. The new HH flows were initially identified from a deep Ha film from the recently commissioned AAO/UKST Ha Survey of the southern sky. Our scanned Ha and broad-band R images highlight both the improved resolution of the Ha survey and the excellent contrast of the Ha flux with respect to the broad-band R. Comparative IVN survey images allow us to distinguish between emission and reflection nebulosity. Our CCD Ha,[Sii], continuum and I-band images confirm the presence of a parsec-scale HH flow associated with the Ori I-2 cometary globule, and several parsec-scale strings of HH emission centred on the L1641-N infrared cluster. Several smaller outflows display one-sided jets. Our results indicate that, for declinations south of 268 in L1641, parsec-scale flows appear to be the major force in the large-scale movement of optical dust and molecular gas.
    [Show full text]
  • Radio Constraints on Activity in Young Brown Dwarfs
    in prep. Radio Constraints on Activity in Young Brown Dwarfs Rachel A. Osten1 Department of Astronomy, University of Maryland, College Park, MD 20742-2421, U.S.A. Electronic Mail: [email protected] Ray Jayawardhana Department of Astronomy & Astrophysics, University of Toronto, Toronto, ON M5S 3H8, CANADA Electronic Mail: [email protected] ABSTRACT We report on searches for radio emission from three of the nearest known young brown dwarfs using the Very Large Array. We have obtained sensitive upper limits on 3.6cm emission from 2MASSW J1207334-393254, TWA 5B and SSSPM J1102-3431, all of which are likely members of the ∼8-Myr-old TW Hy- drae association. We derive constraints on the magnetic field strength and the number density of accelerated electrons, under the assumption that young brown dwarf atmospheres are able to produce gyrosynchrotron emission, as seems to be indicated in older brown dwarfs. For the young brown dwarf TWA 5B, the ratio of its detected X-ray luminosity to the upper limit on radio luminosity places arXiv:astro-ph/0604521v2 27 Apr 2006 it within the expected range for young stars and older, active stars. Thus, its behavior is anomalous compared to older brown dwarfs, in which radio luminos- ity is substantially enhanced over the expected relationship. Our observations deepen the conundrum of magnetic activity in brown dwarfs, and suggest that a factor other than age is more important for determining radio emission in cool substellar objects. Subject headings: stars: activity – stars: coronae – stars: low mass, brown dwarfs – stars: pre-main-sequence – radio continuum 1Hubble Fellow –2– 1.
    [Show full text]
  • Where Are the Hot Ion Lines in Classical T Tauri Stars Formed?
    Accretion, winds and jets: High-energy emission from young stellar objects Dissertation zur Erlangung des Doktorgrades des Departments Physik der Universit¨at Hamburg vorgelegt von Hans Moritz G¨unther aus Hamburg Hamburg 2009 ii Gutachter der Dissertation: Prof. Dr. J. H. M. M. Schmitt Prof. Dr. E. Feigelson Gutachter der Disputation: Prof. Dr. P. H. Hauschildt Prof. Dr. G. Wiedemann Datum der Disputation: 13.03.2009 Vorsitzender des Pr¨ufungsausschusses: Dr. R. Baade Vorsitzender des Promotionsausschusses: Prof. Dr. R. Klanner Dekan der MIN Fakult¨at: Prof. Dr. A. Fr¨uhwald (bis 28.02.2009) Prof. Dr. H. Graener (ab 01.03.2009) iii Zusammenfassung Sterne entstehen durch Gravitationsinstabilit¨aten in molekularen Wolken. Wegen der Erhaltung des Drehimpulses geschieht der Kollaps nicht sph¨arisch, sondern das Material f¨allt zun¨achst auf eine Akkretionsscheibe zusammen. In dieser Doktorarbeit wird hochenergetische Strahlung von Sternen untersucht, die noch aktiv Material von ihrer Scheibe akkretieren, aber nicht mehr von einer Staub- und Gash¨ulle verdeckt sind. In dieser Phase nennt man Sterne der Spektraltypen A und B Herbig Ae/Be (HAeBe) Sterne, alle sp¨ateren Sterne heißen klassische T Tauri Sterne (CTTS); eigentlich werden beide Typen ¨uber spektroskopische Merkmale definiert, aber diese fallen mit den hier genannten Entwicklungsstadien zusammen. In dieser Arbeit werden CTTS und HAeBes mit hochaufl¨osender Spektroskopie im R¨ontgen- und UV-Bereich untersucht und Simulationen f¨ur diese Stadien gezeigt. F¨ur zwei Sterne werden R¨ontgenspektren reduziert und vorgestellt: Der CTTS V4046 Sgr wurde mit Chandra f¨ur 100 ks beobachtet. Die Lichtkurve dieser Beobachtung zeigt einen Flare und die Triplets der He Isosequenz (Si xiii, Ne ix und O vii) deuten auf hohe Dichten im emittierenden Plasma hin.
    [Show full text]
  • Stellar Evolution
    AccessScience from McGraw-Hill Education Page 1 of 19 www.accessscience.com Stellar evolution Contributed by: James B. Kaler Publication year: 2014 The large-scale, systematic, and irreversible changes over time of the structure and composition of a star. Types of stars Dozens of different types of stars populate the Milky Way Galaxy. The most common are main-sequence dwarfs like the Sun that fuse hydrogen into helium within their cores (the core of the Sun occupies about half its mass). Dwarfs run the full gamut of stellar masses, from perhaps as much as 200 solar masses (200 M,⊙) down to the minimum of 0.075 solar mass (beneath which the full proton-proton chain does not operate). They occupy the spectral sequence from class O (maximum effective temperature nearly 50,000 K or 90,000◦F, maximum luminosity 5 × 10,6 solar), through classes B, A, F, G, K, and M, to the new class L (2400 K or 3860◦F and under, typical luminosity below 10,−4 solar). Within the main sequence, they break into two broad groups, those under 1.3 solar masses (class F5), whose luminosities derive from the proton-proton chain, and higher-mass stars that are supported principally by the carbon cycle. Below the end of the main sequence (masses less than 0.075 M,⊙) lie the brown dwarfs that occupy half of class L and all of class T (the latter under 1400 K or 2060◦F). These shine both from gravitational energy and from fusion of their natural deuterium. Their low-mass limit is unknown.
    [Show full text]
  • The UV Perspective of Low-Mass Star Formation
    galaxies Review The UV Perspective of Low-Mass Star Formation P. Christian Schneider 1,* , H. Moritz Günther 2 and Kevin France 3 1 Hamburger Sternwarte, University of Hamburg, 21029 Hamburg, Germany 2 Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research; Cambridge, MA 02109, USA; [email protected] 3 Department of Astrophysical and Planetary Sciences Laboratory for Atmospheric and Space Physics, University of Colorado, Denver, CO 80203, USA; [email protected] * Correspondence: [email protected] Received: 16 January 2020; Accepted: 29 February 2020; Published: 21 March 2020 Abstract: The formation of low-mass (M? . 2 M ) stars in molecular clouds involves accretion disks and jets, which are of broad astrophysical interest. Accreting stars represent the closest examples of these phenomena. Star and planet formation are also intimately connected, setting the starting point for planetary systems like our own. The ultraviolet (UV) spectral range is particularly suited for studying star formation, because virtually all relevant processes radiate at temperatures associated with UV emission processes or have strong observational signatures in the UV range. In this review, we describe how UV observations provide unique diagnostics for the accretion process, the physical properties of the protoplanetary disk, and jets and outflows. Keywords: star formation; ultraviolet; low-mass stars 1. Introduction Stars form in molecular clouds. When these clouds fragment, localized cloud regions collapse into groups of protostars. Stars with final masses between 0.08 M and 2 M , broadly the progenitors of Sun-like stars, start as cores deeply embedded in a dusty envelope, where they can be seen only in the sub-mm and far-IR spectral windows (so-called class 0 sources).
    [Show full text]
  • GEORGE HERBIG and Early Stellar Evolution
    GEORGE HERBIG and Early Stellar Evolution Bo Reipurth Institute for Astronomy Special Publications No. 1 George Herbig in 1960 —————————————————————– GEORGE HERBIG and Early Stellar Evolution —————————————————————– Bo Reipurth Institute for Astronomy University of Hawaii at Manoa 640 North Aohoku Place Hilo, HI 96720 USA . Dedicated to Hannelore Herbig c 2016 by Bo Reipurth Version 1.0 – April 19, 2016 Cover Image: The HH 24 complex in the Lynds 1630 cloud in Orion was discov- ered by Herbig and Kuhi in 1963. This near-infrared HST image shows several collimated Herbig-Haro jets emanating from an embedded multiple system of T Tauri stars. Courtesy Space Telescope Science Institute. This book can be referenced as follows: Reipurth, B. 2016, http://ifa.hawaii.edu/SP1 i FOREWORD I first learned about George Herbig’s work when I was a teenager. I grew up in Denmark in the 1950s, a time when Europe was healing the wounds after the ravages of the Second World War. Already at the age of 7 I had fallen in love with astronomy, but information was very hard to come by in those days, so I scraped together what I could, mainly relying on the local library. At some point I was introduced to the magazine Sky and Telescope, and soon invested my pocket money in a subscription. Every month I would sit at our dining room table with a dictionary and work my way through the latest issue. In one issue I read about Herbig-Haro objects, and I was completely mesmerized that these objects could be signposts of the formation of stars, and I dreamt about some day being able to contribute to this field of study.
    [Show full text]
  • Stellar Properties of Embedded Protostars
    Stellar Properties of Embedded Protostars R. J. White University of Alabama in Huntsville T. P. Greene National Aeronautics and Space Administration at Ames Research Center G. W. Doppmann Gemini Observatory K. R. Covey University of Washington L. A. Hillenbrand California Institute of Technology Protostars are precursors to the nearly fully assembled T-Tauri and Herbig Ae/Be type stars undergoing quasi-static contraction towards the zero-age main sequence; they are in the process of acquiring the majority of their stellar mass. Although numerous young stars with spatially extended envelope-like structures appear to fit this description, their high extinction has inhibited observers from directly measuring their stellar and accretion properties and confirming that they are in fact in the main phase of mass accretion (i.e., true protostars). Recently, however, high dispersion spectrographs on large aperture telescopes have allowed observers to begin studying the stellar and accretion properties of a subset of these stars, commonly referred to as Class I stars. In this Chapter, we summarize the newly determined properties of Class I stars and compare them with observations of Class II stars, which are the more optically revealed T Tauri stars, to better understand the relative evolutionary state of the two classes. Class I stars have distributions of spectral types and stellar luminosities that are similar to those of Class II stars, suggesting similar masses and ages. The stellar luminosity and resulting age estimates, however, are especially uncertain given the difficulty in accounting for the large extinctions, scattered light emission and continuum excesses typical of Class I stars.
    [Show full text]
  • The T Tauri Star RY Tauri As a Case Study of the Inner Regions of Circumstellar Dust Disks
    A&A 478, 779–793 (2008) Astronomy DOI: 10.1051/0004-6361:20077049 & c ESO 2008 Astrophysics The T Tauri star RY Tauri as a case study of the inner regions of circumstellar dust disks A. A. Schegerer1,S.Wolf1, Th. Ratzka2, and Ch. Leinert1 1 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: [email protected] 2 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany Received 3 January 2007 / Accepted 13 November 2007 ABSTRACT Aims. We study the inner region (∼1.0 AU up to a few 10 AUs) of the circumstellar disk around the “classical” T Tauri star RY Tau. Our aim is to find a physical description satisfying the available interferometric data, obtained with the mid-infrared interferometric instrument at the Very Large Telescope Interferometer, as well as the spectral energy distribution in the visible to millimeter wave- length range. We also compare the findings with the results of similar studies, including those of intermediate-mass Herbig Ae/Be stars. Methods. Our analysis is done within the framework of a passively heated circumstellar disk, which is optionally supplemented by the effects of accretion and an added envelope. To achieve a more consistent and realistic model, we used our continuum transfer code MC3D. In addition, we studied the shape of the 10 µm silicate emission feature in terms of the underlying dust population, both for single-dish and for interferometric measurements. Results. We show that a modestly flaring disk model with accretion can explain both the observed spectral energy distribution and the mid-infrared visibilities obtained with the mid-infrared infrared instrument.
    [Show full text]
  • Lecture 26 Pre-Main Sequence Evolution
    Lecture 26 Low-Mass Young Stellar Objects 1. Nearby Star Formation 2. General Properties of Young Stars 3. T Tauri Stars 4. Herbig Ae/Be Stars References Adams, Lizano & Shu ARAA 25 231987 Lada OSPS 1999 Stahler & Palla Chs. 17 & 18 Local Star Forming Regions Much of our knowledge of star formation comes from a few nearby regions Taurus-Auriga & Perseus – 150 pc low mass (sun-like) stars Orion – 450 pc high & low mass stars [Grey – Milky Way Black – Molecular clouds] Representative for the Galaxy as a whole? Stahler & Palla Fig 1.1 PERSEUS with famous objects AURIGA NGC 1579 B5 IC 348 NGC 1333 TMC-1 T Tau L1551 TAURUS Taurus, Auriga & Perseus • A cloud complex rich in cores & YSOs • NGC1333/IC 348 • Pleiades •TMC-1,2 • T Tauri & other TTSs • L 1551 Ophiuchus Wilking et al. 1987 AJ 94 106 CO Andre PP IV Orion L1630 L1630 star clusters L1630 in Orion NIR star clusters on CS(2-1) map E Lada, ApJ 393 25 1992 4 M(L1630) ~ 8x10 Msun 5 massive cores (~ 200 Msun) associated with NIR star clusters 2. General Properties Young stars are associated with molecular clouds. Observations are affected by extinction, which decreases with increasing wavelength. Loosely speaking, we can distinguish two types: Embedded stars - seen only at NIR or longer wavelengths, usually presumed to be very young Revealed stars - seen at optical wavelengths or shorter, usually presumed to be older What makes young stars particularly interesting is Circumstellar gas and dust – both flowing in as well as out, e.g., jets, winds, & disks.
    [Show full text]
  • The Gaseous Disks of Young Stellar Objects
    INVITED TALK NASA LAW, February 14-16, 2006, UNLV, Las Vegas The Gaseous Disks of Young Stellar Objects A. E. Glassgold Astronomy Department, University of California, Berkeley, CA 94720 [email protected] ABSTRACT Disks represent a crucial stage in the formation of stars and planets. They are novel astrophysical systems with attributes intermediate between the interstellar medium and stars. Their physical properties are inhomogeneous and are affected by hard stellar radiation and by dynamical evolution. Observing disk structure is difficult because of the small sizes, ranging from as little as 0.05 AU at the inner edge to 100-1000 AU at large radial distances. Nonetheless, substantial progress has been made by observing the radiation emitted by the dust from near infrared to mm wavelengths, i.e., the spectral energy distribution of an unresolved disk. Many fewer results are available for the gas, which is the main mass component of disks over much of their lifetime. The inner disk gas of young stellar objects (henceforth YSOs) have been studied using the near infrared rovibrational transitions of CO and a few other molecules, while the outer regions have been explored with the mm and sub-mm lines of CO and other species. Further progress can be expected in understanding the physical properties of disks from observations with sub-mm arrays like SMA, CARMA and ALMA, with mid infrared measurements using Spitzer, and near infrared spectroscopy with large ground-based telescopes. Intense efforts are also being made to model the observations using complex thermal-chemical models. After a brief review of the existing observations and modeling results, some of the weaknesses of the models will be discussed, including the absence of good laboratory and theoretical calculations for essential microscopic processes.
    [Show full text]