- ID:
- ivo://CDS.VizieR/J/A+A/593/A37
- Title:
- Spectral cube toward NGC 6334 I and I(N)
- Short Name:
- J/A+A/593/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HF molecule has been proposed as a sensitive tracer of diffuse interstellar gas, while at higher densities its abundance could be influenced heavily by freeze-out onto dust grains. We investigate the spatial distribution of a collection of absorbing gas clouds, some associated with the dense, massive star-forming core NGC 6334 I, and others with diffuse foreground clouds elsewhere along the line of sight. For the former category, we aim to study the dynamical properties of the clouds in order to assess their potential to feed the accreting protostellar cores. We use far-infrared spectral imaging from the Herschel SPIRE iFTS to construct a map of HF absorption at 243um in a 6'x3.5' region surrounding NGC 6334 I and I(N).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/588/A108
- Title:
- Spectra of CO and [CI] in protoplanetary disks
- Short Name:
- J/A+A/588/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The gas-solid budget of carbon in protoplanetary disks is related to the composition of the cores and atmospheres of the planets forming in them. The principal gas-phase carbon carriers CO, C^0^, and C^+6 can now be observed regularly in disks. The gas-phase carbon abundance in disks has thus far not been well characterized observationally. We obtain new constraints on the [C]/[H] ratio in a large sample of disks, and compile an overview of the strength of [CI] and warm CO emission. We carried out a survey of the CO 6-5 line and the [CI] 1-0 and 2-1 lines towards 37 disks with the APEX telescope, and supplemented it with [CII] data from the literature. The data are interpreted using a grid of models produced with the DALI disk code. We also investigate how well the gas-phase carbon abundance can be determined in light of parameter uncertainties.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/1964
- Title:
- Spectra of three nearby star-forming regions
- Short Name:
- J/ApJ/703/1964
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze samples of Spitzer Infrared Spectrograph spectra of T Tauri stars in the Ophiuchus, Taurus, and Chamaeleon I star-forming regions, whose median ages lie in the <1-2Myr range. The median mid-infrared spectra of objects in these three regions are similar in shape, suggesting, on average, similar disk structures. When normalized to the same stellar luminosity, the medians follow each other closely, implying comparable mid-infrared excess emission from the circumstellar disks. We use the spectral index between 13 and 31um and the equivalent width of the 10um silicate emission feature to identify objects whose disk configuration departs from that of a continuous, optically thick accretion disk. Based on their medians and fraction of evolved disks, T Tauri stars in Taurus and Chamaeleon I are very alike.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A16
- Title:
- Spectra of W49 massives young stars
- Short Name:
- J/A+A/589/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive stars form on different scales ranging from large, dispersed OB associations to compact, dense starburst clusters. The complex structure of regions of massive star formation, and the involved short timescales provide a challenge for our understanding of their birth and early evolution. As one of the most massive and luminous star- forming region in our Galaxy, W49 is the ideal place to study the formation of the most massive stars. By classifying the massive young stars deeply embedded into the molecular cloud of W49, we aim to investigate and trace the star formation history of this region. We analyse near-infrared K-band spectroscopic observations of W49 from LBT/LUCI combined with JHK images obtained with NTT/SOFI and LBT/LUCI. Based on JHK -band photometry and K-band spectroscopy the massive stars are placed in a Hertzsprung Russell diagram. By comparison with evolutionary models, their age and hence the star formation history of W49 can be investigated.
- ID:
- ivo://CDS.VizieR/J/AJ/133/2524
- Title:
- Spectra of young nearby stars
- Short Name:
- J/AJ/133/2524
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-dispersion (R~16000) optical (3900-8700{AA}) spectra of 390 stars obtained with the Palomar 60inch telescope. The majority of stars observed are part of the Spitzer Legacy Science Program "The Formation and Evolution of Planetary Systems." Through detailed analysis we determine stellar properties for this sample, including radial and rotational velocities, LiI{lambda}6708 and H{alpha} equivalent widths, the chromospheric activity index R'_HK_, and temperature- and gravity-sensitive line ratios. Several spectroscopic binaries are also identified. From our tabulations, we illustrate basic age- and rotation-related correlations among measured indices. One novel result is that CaII chromospheric emission appears to saturate at vsini values above ~30km/s, similar to the well-established saturation of X-rays that originate in the spatially separate coronal region.
- ID:
- ivo://CDS.VizieR/J/ApJ/691/672
- Title:
- Spectrocopy of YSOs in Serpens molecular cloud
- Short Name:
- J/ApJ/691/672
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of an optical spectroscopic survey designed to confirm the youth and determine the spectral types among a sample of young stellar object (YSO) candidates in the Serpens molecular cloud. We observed 150 infrared (IR) excess objects previously discovered by the Spitzer Legacy Program "From Molecular Cores to Planet-Forming Disks" (c2d), bright enough for subsequent Spitzer/InfraRed Spectrograph (IRS) spectroscopy. We obtained 78 optical spectra of sufficient signal-to-noise for analysis. Extinctions, effective temperatures, and luminosities are estimated for this sample, and used to construct Hertzsprung-Russell (H-R) diagrams for the population. We identified 20 background giants contaminating the sample, based on their relatively high extinction, position in the H-R diagram, the lack of H{alpha} emission and relatively low IR excess. Such strong background contamination (25%) is consistent with the location of Serpens being close to the Galactic plane (5{deg} Galactic latitude). The remaining 58 stars (75%) were all confirmed to be young, mostly K- and M-type stars that are presumed to belong to the cloud. Our analysis shows that the majority of the IR excess objects detected in Serpens are actively accreting, young T-Tauri stars.
- ID:
- ivo://CDS.VizieR/J/AJ/149/103
- Title:
- Spectroscopy of candidate YSOs in Serpens
- Short Name:
- J/AJ/149/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have completed an optical spectroscopic survey of a sample of candidate young stars in the Serpens Main star-forming region selected from deep B, V, and R band images. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys have been biased toward particular stages of pre-main sequence evolution. We have obtained over 700 moderate resolution optical spectra that, when combined with published data, have led to the identification of 63 association members based on the presence of H{alpha} in emission, lithium absorption, X-ray emission, a mid-infrared excess, and/or reflection nebulosity. Twelve YSOs are identified based on the presence of lithium absorption alone. An additional 16 objects are classified as possible association members and their pre-main sequence nature is in need of confirmation. Spectral types along with V and R band photometry were used to derive effective temperatures and bolometric luminosities for association members to compare with theoretical tracks and isochrones for pre-main sequence stars. An average age of 2Myr is derived for this population. When compared to simulations, there is no obvious evidence for an age spread when considering the major sources of uncertainties in the derived luminosities. However when compared to the young cluster in Ophiuchus, the association members in Serpens appear to have a larger spread in luminosities and hence ages which could be intrinsic to the region or the result of a foreground population of YSOs associated with the Aquila Rift. Modeling of the spectral energy distributions from optical through mid-infrared wavelengths has revealed three new transition disk objects, making a total of six in the cluster. Echelle spectra for a subset of these sources enabled estimates of vsini for seven association members. Analysis of gravity-sensitive lines in the echelle and moderate resolution spectra of the association members indicate surface gravities consistent with dwarf or sub-giant stars.
- ID:
- ivo://CDS.VizieR/J/AJ/153/188
- Title:
- Spectroscopy of the foreground population in Orion A
- Short Name:
- J/AJ/153/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a spectroscopic survey of the foreground population in Orion A with MMT/Hectospec. We use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk properties of these sources. We identify 37 new transition disk (TD) objects, 1 globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass of less than 0.018-0.030 M_{sun}_, which harbors a flaring disk. Using the H{alpha} emission line, we characterize the accretion activity of the sources with disks, and confirm that the fraction of accreting TDs is lower than that of optically thick disks (46%+/-7% versus 73%+/-9%, respectively). Using kinematic data from the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of the Young Nebulous Clusters program (IN-SYNC), we confirm that the foreground population shows similar kinematics to their local molecular clouds and other young stars in the same regions. Using the isochronal ages, we find that the foreground population has a median age of around 1-2 Myr, which is similar to that of other young stars in Orion A. Therefore, our results argue against the presence of a large and old foreground cluster in front of Orion A.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A85
- Title:
- SPHERE images of HD 32297
- Short Name:
- J/A+A/630/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectro-photometry of debris disks in total intensity and polarimetry can provide new insight into the properties of the dust grains therein (size distribution and optical properties). We aim to constrain the morphology of the highly inclined debris disk HD32297. We also intend to obtain spectroscopic and polarimetric measurements to retrieve information on the particle size distribution within the disk for certain grain compositions. We observed HD32297 with SPHERE in Y, J, and H bands in total intensity and in J band in polarimetry. The observations are compared to synthetic models of debris disks and we developed methods to extract the photometry in total intensity overcoming the data-reduction artifacts, namely the self-subtraction. The spectro-photometric measurements averaged along the disk mid-plane are then compared to model spectra of various grain compositions. These new images reveal the very inner part of the system as close as 0.15". The disk image is mostly dominated by the forward scattering making one side (half-ellipse) of the disk more visible, but observations in total intensity are deep enough to also detect the back side for the very first time. The images as well as the surface brightness profiles of the disk rule out the presence of a gap as previously proposed. We do not detect any significant asymmetry between the northeast and southwest sides of the disk. The spectral reflectance features a "gray to blue" color which is interpreted as the presence of grains far below the blowout size. The presence of sub-micron grains in the disk is suspected to be the result of gas drag and/or "avalanche mechanisms". The blue color of the disk could be further investigated with additional total intensity and polarimetric observations in K and H bands respectively to confirm the spectral slope and the fraction of polarization.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A19
- Title:
- Spiral structure in the gas disc of CQ Tau
- Short Name:
- J/A+A/648/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used spatially resolved ALMA observations of the three CO isotopologues ^12^CO, ^13^CO and C^18^O (J=2-1) from CQ Tau to analyse the brightness temperature and kinematics of the gas disc. We detect significant spiral structures in both the brightness temperature and the rotation velocity of ^12^CO after subtraction of an azimuthally symmetric model, which may be tracing planet-disc interactions with an embedded planet or low-mass companion. The brightness temperature spirals are morphologically connected to spirals observed in NIR scattered light in the same disc, indicating a common origin. Together with the observed large dust and gas cavity, these spiral structures support the hypothesis of a massive embedded companion in the CQ Tau disc.
