- ID:
- ivo://CDS.VizieR/J/ApJ/724/835
- Title:
- The Spitzer c2d survey of WTTSs. III.
- Short Name:
- J/ApJ/724/835
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 3.6 to 70um Spitzer photometry of 154 weak-line T Tauri stars (WTTSs) in the Chamaeleon, Lupus, Ophiuchus, and Taurus star formation regions, all of which are within 200pc of the Sun. For a comparative study, we also include 33 classical T Tauri stars which are located in the same star-forming regions. Spitzer sensitivities allow us to robustly detect the photosphere in the IRAC bands (3.6 to 8um) and the 24um MIPS band. In the 70um MIPS band, we are able to detect dust emission brighter than roughly 40 times the photosphere. These observations represent the most sensitive WTTSs survey in the mid- to far-infrared to date and reveal the frequency of outer disks (r=3-50AU) around WTTSs. The 70um photometry for half the c2d WTTSs sample (the on-cloud objects), which were not included in the earlier papers in this series, those of Padgett et al. (2006ApJ...645.1283P) and Cieza et al. (2007, Cat. J/ApJ/667/308) are presented here for the first time.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/838/150
- Title:
- The Taurus-Auriga ecosystem. I.
- Short Name:
- J/ApJ/838/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The census of Taurus-Auriga has been assembled over seven decades and inherited the biases and incompleteness of the input studies. The unusual shape of its inferred initial mass function (IMF) and the existence of isolated disk-bearing stars suggest that additional (likely disk-free) members remain to be discovered. We therefore have begun a global reassessment of the census of Taurus-Auriga that exploits new data and better definitions of youth and kinematic membership. As a first step, we reconsider the membership of all disk-free candidate members from the literature with spectral type >=F0, 3h50min<{alpha}5h40min, and 14{deg}<{delta}<34{deg}. We combine data from the literature with Keck/HIRES and UH88/SNIFS spectra to test the membership of these candidates using the positions in the Hertzsprung-Russel diagram, proper motions, radial velocities, H{alpha}, lithium, and surface gravity. We find 218 confirmed or likely Taurus members, 160 confirmed or likely interlopers, and only 18 that lack sufficient evidence to draw firm conclusions. A significant fraction of these stars (81/218=37%) are not included in the most recent canonical member lists. There are few additional members to the immediate vicinity of the molecular clouds, preserving the IMFs that have been deemed anomalous in past work. Many of the likely Taurus members are instead distributed broadly across the search area. When combined with the known disk hosts, our updated census reveals two regimes: a high-density population with a high disk fraction (indicative of youth) that broadly traces the molecular clouds, and a low-density population with low disk fraction (hence likely older) that most likely represents previous generations of star formation.
- ID:
- ivo://CDS.VizieR/J/ApJS/224/22
- Title:
- The YSO population of LDN 1340 in infrared
- Short Name:
- J/ApJS/224/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of an infrared study of the molecular cloud Lynds 1340, forming three groups of low- and intermediate-mass stars. Our goals are to identify and characterize the young stellar population of the cloud, study the relationships between the properties of the cloud and the emergent stellar groups, and integrate L1340 into the picture of the star-forming activity of our Galactic environment. We selected candidate young stellar objects (YSOs) from the Spitzer and WISE databases using various published color criteria and classified them based on the slope of the spectral energy distribution (SED). We identified 170 Class II, 27 flat SED, and 45 Class 0/I sources. High angular resolution near-infrared observations of the RNO 7 cluster, embedded in L1340, revealed eight new young stars of near-infrared excess. The surface density distribution of YSOs shows three groups, associated with the three major molecular clumps of L1340, each consisting of <~100 members, including both pre-main-sequence stars and embedded protostars. New Herbig-Haro objects were identified in the Spitzer images. Our results demonstrate that L1340 is a prolific star-forming region of our Galactic environment in which several specific properties of the intermediate-mass mode of star formation can be studied in detail.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A112
- Title:
- THOR. The HI, OH, Recombination Line Survey
- Short Name:
- J/A+A/580/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To study the atomic, molecular and ionized emission of Giant Molecular Clouds (GMCs), we have initiated a Large Program with the VLA: 'THOR - The HI, OH, Recombination Line survey of the Milky Way'. We map the 21cm HI line, 4 OH lines, 19 H{alpha} recombination lines and the continuum from 1 to 2GHz of a significant fraction of the Milky Way (l=15-67{deg}, |b|<1{deg}) at ~20" resolution. In this paper, we focus on the HI emission from the W43 star-formation complex. Classically, the HI 21cm line is treated as optically thin with column densities calculated under this assumption. This might give reasonable results for regions of low-mass star-formation, however, it is not sufficient to describe GMCs. We analyzed strong continuum sources to measure the optical depth, and thus correct the HI 21cm emission for optical depth effects and weak diffuse continuum emission. Hence, we are able to measure the HI mass of W43 more accurately and our analysis reveals a lower limit of M=6.6x10^6^M_{sun}_, which is a factor of 2.4 larger than the mass estimated with the assumption of optically thin emission. The HI column densities are as high as N(HI)~150M_{sun}_/pc^2^~1.9x10^22cm^-2^, which is an order of magnitude higher than for low mass star formation regions. This result challenges theoretical models that predict a threshold for the HI column density of ~10M_{sun}_/pc^2^, at which the formation of molecular hydrogen should set in. By assuming an elliptical layered structure for W43, we estimate the particle density profiles. While at the cloud edge atomic and molecular hydrogen are well mixed, the center of the cloud is strongly dominated by molecular hydrogen. We do not identify a sharp transition between hydrogen in atomic and molecular form. Our results are an important characterization of the atomic to molecular hydrogen transition in an extreme environment and challenges current theoretical models.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A44
- Title:
- TMC-1N mapping in JHK bands
- Short Name:
- J/A+A/558/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mapping of the near-infrared (NIR) scattered light is a recent method for the study of interstellar clouds, complementing other, more commonly used methods, like dust emission and extinction. Our goal is to study the usability of this method on larger scale, and compare the properties of a filamentary structure using infrared scattering and other methods. We also study the radiation field and differences in grain emissivity between diffuse and dense areas. We have used scattered NIR J, H, and K band surface brightness observations with WFCAM instrument to map a filament TMC-1N in Taurus Molecular Cloud, covering an area of 1{deg}x1{deg} corresponding to ~(2.44pc). We have converted the data into an optical depth map and compared the results with NIR extinction and Herschel observations of sub-mm dust emission. We have also modelled the filament with 3D radiative transfer calculations of scattered light.
- ID:
- ivo://CDS.VizieR/J/MNRAS/396/964
- Title:
- T Tauri in and around bright-rimmed clouds
- Short Name:
- J/MNRAS/396/964
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to quantitatively testify the 'small-scale sequential star formation' hypothesis in and around bright-rimmed clouds (BRCs). As a continuation of the recent attempt by Ogura et al. (2007PASJ...59..199O), we have carried out BVIc photometry of four more BRC aggregates along with deeper re-observations of two previously observed BRCs. Again, quantitative age gradients are found in almost all the BRCs studied in the present work. Archival Spitzer/Infrared Array Camera data also support this result.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A99
- Title:
- UBVRI images of Barnard 207
- Short Name:
- J/A+A/605/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Barnard 207 (B207, LDN 1489, LBN 777), also known as the Vulture Head nebula, is a cometary globule in the Taurus-Auriga-Perseus Molecular Cloud region. B207 is known to host a Class I protostar, IRAS 04016+2610, located at a projected distance of ~8400au from the dense core centre. Using imaging and photometry over a wide wavelength range, from UV to sub-mm, we study the physical properties of B207 and the dust grains contained within. The core density, temperature, and mass are typical of other globules found in the Milky Way interstellar medium (ISM). The increase in the dust albedo with increasing optical wavelengths, along with the detection of coreshine in the near infrared, indicates the presence of larger dust grains in B207. The measured optical, near-, mid- and far-infrared intensities are in agreement with the CMM+AMM and CMM+AMMI dust grain type of the THEMIS model, suggesting mantle formation on the dust grains throughout the globule. We investigate the possibility of turbulence being responsible for diffusing dust grains from the central core to external outer layers of B207. However, in situ formation of large dust grains cannot be excluded.
- ID:
- ivo://CDS.VizieR/J/MNRAS/331/474
- Title:
- ubvy{beta} photometry in the Lupus dark cloud
- Short Name:
- J/MNRAS/331/474
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stroemgren uvby{beta} photometry observations obtained for 205 stars in the general direction of a void in the IRAS 100-{mu}m emission from the Lupus dark cloud complex are presented and analysed. The colour excess versus distance diagram confirms the existence of a region depleted from interstellar material, which is also seen in the ROSAT soft X-ray background emission map. The distance to the surrounding material is estimated as being within the interval from 60 to 100pc. This result is in disagreement with previous distance estimates to the supposed supernova that has been suggested as responsible for clearing the region from dust. As an alternative, the data presented support the suggestion that the void may have been produced by the detachment of material from the interface between LoopI and the Local Bubble as a consequence of hydromagnetic instabilities. Moreover, the distribution of colour excess as a function of distance supports a value of ~150pc as the most probable distance to the dark cloud known as Lupus1.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A11
- Title:
- 70um-1.2mm and N_2_H+ maps of IRDC18454 (W43)
- Short Name:
- J/A+A/538/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The earliest stages of high-mass star formation are still poorly characterized. Densities, temperatures and kinematics are crucial parameters for simulations of high-mass star formation. It is also unknown whether the initial conditions vary with environment. We want to investigate the youngest massive gas clumps in the environment of extremely active star formation. We selected the IRDC18454 complex, directly associated with the W43 Galactic mini-starburst, and observed it in the continuum emission between 70um and 1.2mm with Herschel, APEX and the 30m telescope, and in spectral line emission of N_2_H+ and ^13^CO with the Nobeyama 45m, the IRAM 30m and the Plateau de Bure Interferometer.
- ID:
- ivo://CDS.VizieR/J/MNRAS/379/663
- Title:
- 850um observations of W3 giant molecular cloud
- Short Name:
- J/MNRAS/379/663
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed a ~0.9 square degree area of the W3 giant molecular cloud (GMC) and star-forming region in the 850-um continuum, using the Submillimetre Common-User Bolometer Array on the James Clerk Maxwell Telescope. A complete sample of 316 dense clumps were detected with a mass range from around 13 to 2500M_{sun}_.
