- ID:
- ivo://CDS.VizieR/J/MNRAS/415/103
- Title:
- IPHAS T Tauri candidates in IC 1396
- Short Name:
- J/MNRAS/415/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Isaac Newton Telescope (INT) Photometric H-Alpha Survey (IPHAS) is a 1800deg^2^ survey of the Northern Galactic Plane, reaching down to r'~21. We demonstrate how the survey can be used to (1) reliably select classical T Tauri star candidates and (2) constrain the mass accretion rates with an estimated relative uncertainty of 0.6dex. IPHAS is a necessary addition to spectroscopic surveys because it allows large and uniform samples of accretion rates to be obtained with a precise handle on the selection effects. We apply the method on a region of 7deg^2^ towards the HII region IC 1396 in Cepheus OB2 and identify 158 pre-main-sequence candidates with masses between 0.2 and 2.0M_{sun}_ and accretion rates between 10-9.2 and 10-7.0M_{sun}_/yr.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/675/1375
- Title:
- IRAC/MIPS photometry in Cha I
- Short Name:
- J/ApJ/675/1375
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a census of circumstellar disks in the Chamaeleon I star-forming region. Using the Infrared Array Camera and the Multiband Imaging Photometer on board the Spitzer Space Telescope, we have obtained images of Chamaeleon I at 3.6, 4.5, 5.8, 8.0, and 24um. To search for new disk-bearing members of the cluster, we have performed spectroscopy on objects that have red colors in these data. Through this work, we have discovered four new members of Chamaeleon I with spectral types of M4, M6, M7.5, and L0.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A10
- Title:
- IRAS23033+5951 continuum & line data cubes at 1.3mm
- Short Name:
- J/A+A/629/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation process of high-mass stars (>8M_{sun}_) is poorly constrained, particularly, the effects of clump fragmentation creating multiple systems and the mechanism of mass accretion onto the cores. We study the fragmentation of dense gas clumps, and trace the circumstellar rotation and outflows by analyzing observations of the high-mass (~500M_{sun}_) star-forming region IRAS 23033+5951. Using the Northern Extended Millimeter Array (NOEMA) in three configurations and the IRAM 30-m single-dish telescope at 220GHz, we probe the gas and dust emission at an angular resolution of ~0.45", corresponding to 1900au. In the mm continuum emission, we identify a protostellar cluster with at least four mm-sources, where three of them show a significantly higher peak intensity well above a signal-to-noise ratio of 100. Hierarchical fragmentation from large to small spatial scales is discussed. Two fragments are embedded in rotating structures and drive molecular outflows, traced by ^13^CO (2-1) emission. The velocity profiles across two of the cores are similar to Keplerian but are missing the highest velocity components close to the center of rotation, which is a common phenomena from observations like these, and other rotation scenarios are not excluded entirely. Position-velocity diagrams suggest protostellar masses of ~6 and 19M_{sun}. Rotational temperatures from fitting CH_3_CN (12_K_-11_K_) spectra are used for estimating the gas temperature and by that the disk stability against gravitational fragmentation, utilizing Toomre's Q parameter. Assuming that the candidate disk is in Keplerian rotation about the central stellar object and considering different disk inclination angles, we identify only one candidate disk to be unstable against gravitational instability caused by axisymmetric perturbations. The dominant sources cover different evolutionary stages within the same maternal gas clump. The appearance of rotation and outflows of the cores are similar to those found in low-mass star-forming regions.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/28
- Title:
- IR counterparts to submm H-ATLAS galaxies
- Short Name:
- J/ApJ/756/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Spitzer-IRAC data to identify near-infrared counterparts to submillimeter galaxies detected with Herschel-SPIRE at 250{mu}m in the Herschel Astrophysical Terahertz Large Area Survey. Using a likelihood ratio analysis we identify 146 reliable IRAC counterparts to 123 SPIRE sources out of the 159 in the survey area. We find that, compared to the field population, the SPIRE counterparts occupy a distinct region of the 3.6 and 4.5{mu}m color-magnitude space, and we use this property to identify 23 further counterparts to 13 SPIRE sources. The IRAC identification rate of 86% is significantly higher than those that have been demonstrated with wide-field ground-based optical and near-IR imaging of Herschel fields. We estimate a false identification rate of 3.6%, corresponding to 4-5 sources. Among the 73 counterparts that are undetected in Sloan Digital Sky Survey, 57 have both 3.6 and 4.5{mu}m coverage. Of these, 43 have [3.6]-[4.5]>0, indicating that they are likely to be at z>~1.4. Thus, ~40% of identified SPIRE galaxies are likely to be high-redshift (z>~1.4) sources. We discuss the statistical properties of the IRAC-identified SPIRE galaxy sample including far-IR luminosities, dust temperatures, star formation rates, and stellar masses. The majority of our detected galaxies have 10^10^-10^11^L_{sun}_ total IR luminosities and are not intense starbursting galaxies as those found at z~2, but they have a factor of 2-3 above average specific star formation rates compared to near-IR selected galaxy samples.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A79
- Title:
- IRDC APEX/SABOCA observations
- Short Name:
- J/A+A/559/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared-dark clouds (IRDCs) harbor the early phases of cluster and high-mass star formation and are comprised of cold (~20K), dense (n>10^4^cm^-3^) gas. The spectral energy distribution (SED) of IRDCs is dominated by the far-infrared and millimeter wavelength regime, and our initial Herschel study examined IRDCs at the peak of the SED with high angular resolution. Here we present a follow-up study using the SABOCA instrument on APEX which delivers 7.8" angular resolution at 350{mu}m, matching the resolution we achieved with Herschel/PACS, and allowing us to characterize substructure on ~0.1pc scales. Our sample of 11 nearby IRDCs are a mix of filamentary and clumpy morphologies, and the filamentary clouds show significant hierarchical structure, while the clumpy IRDCs exhibit little hierarchical structure. All IRDCs, regardless of morphology, have about 14% of their total mass in small scale core-like structures which roughly follow a trend of constant volume density over all size scales. Out of the 89 protostellar cores we identified in this sample with Herschel, we recover 40 of the brightest and re-fit their SEDs and find their properties agree fairly well with our previous estimates (<T>~19K). We detect a new population of "cold cores" which have no 70{mu}m counterpart, but are 100 and 160{mu}m-bright, with colder temperatures (<T>~16K). This latter population, along with SABOCA-only detections, are predominantly low-mass objects, but their evolutionary diagnostics are consistent with the earliest starless or prestellar phase of cores in IRDCs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/1506
- Title:
- IRDC cores in SCUBA Legacy Catalogue
- Short Name:
- J/MNRAS/399/1506
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an investigation of candidate infrared dark cloud (IRDC) cores as identified by Simon et al. (2006, Cat. J/ApJ/639/227) located within the Submillimetre Common User Bolometer Array (SCUBA) Legacy Catalogue. After applying a uniform noise cut to the catalogue data, we identify 154 IRDC cores that were detected at 850um and 51 cores that were not. We derive column densities for each core from their 8um extinction and find that the IRDCs detected at 850um have higher column densities (a mean of 1.7x10^22^cm^-2^) compared to those cores not detected at 850um (a mean of 1.0x10^22^cm-2).
- ID:
- ivo://CDS.VizieR/J/ApJ/658/1264
- Title:
- IR-excess sources in GLIMPSE and MSX
- Short Name:
- J/ApJ/658/1264
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 230 Tycho-2 Spectral Catalog stars that exhibit 8um mid-IR extraphotospheric excesses in the MSX and Spitzer GLIMPSE surveys. Of these, 183 are either OB stars earlier than B8 in which the excess plausibly arises from a thermal bremsstrahlung component or evolved stars in which the excess may be explained by an atmospheric dust component. The remaining 47 stars have spectral classifications B8 or later and appear to be main-sequence or late pre-main-sequence objects harboring circumstellar disks. Six of the 47 stars exhibit multiple signatures characteristic of pre-main-sequence circumstellar disks, including emission lines, near-IR K-band excesses, and X-ray emission. Approximately one-third of the remaining 41 sources have emission lines suggesting relative youth. We modeled the excesses in 26 stars having two or more measurements in excess of the expected photospheres as single-component blackbodies.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/167
- Title:
- JCMT Gould Belt Survey: dense cores in Orion B
- Short Name:
- J/ApJ/817/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a first look at the SCUBA-2 observations of three sub-regions of the Orion B molecular cloud: LDN 1622, NGC 2023/2024, and NGC 2068/2071, from the JCMT Gould Belt Legacy Survey. We identify 29, 564, and 322 dense cores in L1622, NGC 2023/2024, and NGC 2068/2071 respectively, using the SCUBA-2 850{mu}m map, and present their basic properties, including their peak fluxes, total fluxes, and sizes, and an estimate of the corresponding 450{mu}m peak fluxes and total fluxes, using the FellWalker source extraction algorithm. Assuming a constant temperature of 20K, the starless dense cores have a mass function similar to that found in previous dense core analyses, with a Salpeter-like slope at the high-mass end. The majority of cores appear stable to gravitational collapse when considering only thermal pressure; indeed, most of the cores which have masses above the thermal Jeans mass are already associated with at least one protostar. At higher cloud column densities, above 1-2x10^23^/cm2, most of the mass is found within dense cores, while at lower cloud column densities, below 1x10^23^/cm2, this fraction drops to 10% or lower. Overall, the fraction of dense cores associated with a protostar is quite small (<8%), but becomes larger for the densest and most centrally concentrated cores. NGC 2023/2024 and NGC 2068/2071 appear to be on the path to forming a significant number of stars in the future, while L1622 has little additional mass in dense cores to form many new stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/1551
- Title:
- JCMT Gould Belt Survey: Serpens MWC 297
- Short Name:
- J/MNRAS/448/1551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present SCUBA-2 450 and 850{mu}m observations of the Serpens MWC 297 region, part of the James Clerk Maxwell Telescope (JCMT) Gould Belt Survey of nearby star-forming regions. Simulations suggest that radiative feedback influences the star formation process and we investigate observational evidence for this by constructing temperature maps. Maps are derived from the ratio of SCUBA-2 fluxes and a two-component model of the JCMT beam for a fixed dust opacity spectral index of {beta}=1.8. Within 40-arcsec of the B1.5Ve Herbig star MWC 297, the submillimetre fluxes are contaminated by free-free emission with a spectral index of 1.03+/-0.02, consistent with an ultracompact HII region and polar winds/jets. Contamination accounts for 73+/-5 per cent and 82+/-4 per cent of peak flux at 450{mu}m and 850 {mu}m, respectively. The residual thermal disc of the star is almost undetectable at these wavelengths. Young stellar objects (YSOs) are confirmed where SCUBA-2 850{mu}m clumps identified by the fellwalker algorithm coincide with Spitzer Gould Belt Survey detections. We identify 23 objects and use T_bol_ to classify nine YSOs with masses 0.09 to 5.1M_{sun}_. We find two Class 0, one Class 0/I, three Class I and three Class II sources. The mean temperature is 15+/-2K for the nine YSOs and 32+/-4K for the 14 starless clumps. We observe a starless clump with an abnormally high mean temperature of 46+/-2K and conclude that it is radiatively heated by the star MWC 297. Jeans stability provides evidence that radiative heating by the star MWC 297 may be suppressing clump collapse.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/4022
- Title:
- JCMT Gould Belt Survey: Southern Orion A
- Short Name:
- J/MNRAS/461/4022
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the JCMT Gould Belt Survey's first look results of the southern extent of the Orion A Molecular Cloud ({delta}<=-5:31:27.5). Employing a two-step structure identification process, we construct individual catalogues for large-scale regions of significant emission labelled as islands and smaller-scale subregions called fragments using the 850{mu}m continuum maps obtained using SCUBA-2. We calculate object masses, sizes, column densities, and concentrations. We discuss fragmentation in terms of a Jeans instability analysis and highlight interesting structures as candidates for follow-up studies. Furthermore, we associate the detected emission with young stellar objects (YSOs) identified by Spitzer and Herschel. We find that although the population of active star-forming regions contains a wide variety of sizes and morphologies, there is a strong positive correlation between the concentration of an emission region and its calculated Jeans instability. There are, however, a number of highly unstable subregions in dense areas of the map that show no evidence of star formation. We find that only ~72 per cent of the YSOs defined as Class 0+I and flat-spectrum protostars coincide with dense 850{mu}m emission structures (column densities >3.7x10^21^cm^-2^). The remaining 28 per cent of these objects, which are expected to be embedded in dust and gas, may be misclassified. Finally, we suggest that there is an evolution in the velocity dispersion of YSOs such that sources which are more evolved are associated with higher velocities.
