- ID:
- ivo://CDS.VizieR/J/A+A/606/A35
- Title:
- Barnard 1b-N and 1b-S 350GHz images
- Short Name:
- J/A+A/606/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation epoch of protostellar disks is debated because of the competing roles of rotation, turbulence, and magnetic fields in the early stages of low-mass star formation. Magnetohydrodynamics simulations of collapsing cores predict that rotationally supported disks may form in strongly magnetized cores through ambipolar diffusion or misalignment between the rotation axis and the magnetic field orientation. Detailed studies of individual sources are needed to cross check the theoretical predictions. We present 0.06-0.1arcsec resolution images at 350GHz toward B1b-N and B1b-S, which are young class 0 protostars, possibly first hydrostatic cores. The images have been obtained with ALMA, and we compare these data with magnetohydrodynamics simulations of a collapsing turbulent and magnetized core. The submillimeter continuum emission is spatially resolved by ALMA. Compact structures with optically thick 350GHz emission are detected toward both B1b-N and B1b-S, with 0.2 and 0.35arcsec radii (46 and 80au at the Perseus distance of 230pc), within a more extended envelope. The flux ratio between the compact structure and the envelope is lower in B1b-N than in B1b-S, in agreement with its earlier evolutionary status. The size and orientation of the compact structure are consistent with 0.2arcsec resolution 32GHz observations obtained with the Very Large Array as a part of the VANDAM survey, suggesting that grains have grown through coagulation. The morphology, temperature, and densities of the compact structures are consistent with those of disks formed in numerical simulations of collapsing cores. Moreover, the properties of B1b-N are consistent with those of a very young protostar, possibly a first hydrostatic core. These observations provide support for the early formation of disks around low-mass protostars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/577/L2
- Title:
- Barnard 1b-N and 1b-S nascent bipolar outflows
- Short Name:
- J/A+A/577/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the theory of star formation, the first hydrostatic core (FHSC) phase is a critical step in which a condensed object emerges from a prestellar core. This step lasts about one thousand years, a very short time compared with the lifetime of prestellar cores, and therefore is hard to detect unambiguously. We present IRAM Plateau de Bure observations of the Barnard 1b dense molecular core, combining detections of H2CO and CH3OH spectral lines and dust continuum at 2.3" resolution (~500AU). The two compact cores B1b-N and B1b-S are detected in the dust continuum at 2mm, with fluxes that agree with their spectral energy distribution. Molecular outflows associated with both cores are detected. They are inclined relative to the direction of the magnetic field, in agreement with predictions of collapse in turbulent and magnetized gas with a ratio of mass to magnetic flux somewhat higher than the critical value, {mu}~2-7. The outflow associated with B1b-S presents sharp spatial structures, with ejection velocities of up to ~7km/s from the mean velocity. Its dynamical age is estimated to be ~2000yr. The B1b-N outflow is smaller and slower, with a short dynamical age of ~1000yr. The B1b-N outflow mass, mass-loss rate, and mechanical luminosity agree well with theoretical predictions of FHSC. These observations confirm the early evolutionary stage of B1b-N and the slightly more evolved stage of B1b-S.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A79
- Title:
- Barnard 30 dark cloud IR and submm data
- Short Name:
- J/A+A/612/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The early evolutionary stage of brown dwarfs (BDs) is not very well characterized, especially during the embedded phase. Our goal is to gain insight into the dominant formation mechanism of very low-mass objects and BDs. We have conducted deep observations at 870um obtained with the LABOCA bolometer at the APEX telescope in order to identify young submillimeter (submm) sources in the Barnard 30 dark cloud. We have complemented these data with multi-wavelength observations from the optical to the far-IR and compiled complete spectral energy distributions in order to identify the counterparts, characterize the sources and to assess their membership to the association and stellar or substellar status based on the available photometric information. We have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified into three distinct groups. First, 15 of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BD candidates. Moreover, a substantial number of them could be multiple systems. A second group of 13 sources comprises candidate members with significant infrared excesses located away from the central submm emission. All of them include BD candidates, some displaying IR excess, but their association with submm emission is unclear. In addition, we have found six starless cores and, based on the total dust mass estimate, three might be pre-substellar (or pre-BDs) cores. Finally, the complete characterization of our APEX/LABOCA sources, focusing on those detected at 24 and/or 70um, indicates that in our sample of 34 submm sources there are, at least: two WTTs, four CTTs, five young stellar objects, eight proto-BD candidates (with another three dubious cases), and one very low luminosity objects.
- ID:
- ivo://CDS.VizieR/VII/220A
- Title:
- Barnard's Catalogue of 349 Dark Objects in the Sky
- Short Name:
- VII/220A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue was created based on the original published catalogue by Barnard E.E., 1927, Carnegie Institution of Washington, "A photographic Atlas of selected regions of the Milky Way". The catalogue contains positions of 349 Barnard Objects. The objects with numbers from 1 to 175 are classified in the first Barnard catalogue (1919ApJ....49....1B); three of the objects in that list have been omitted here (Nos 52, 131a, and 172) because these objects had been listed twice. The objects from Barnard's second list are numbered from 201 to 370 -- there are therefore no objects having the numbers from 176 to 200. Their positions were determined by Miss Calvert. The epoch for all positions in the original published catalogue was 1875.0. Positions for both 1875.0 and 2000.0, the diameters and the notes are included in this machine-readable catalogue.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/4731
- Title:
- Barred galaxies structural decomposition
- Short Name:
- J/MNRAS/473/4731
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of two-component (disc+bar) and three-component (disc+bar+bulge) multiwavelength 2D photometric decompositions of barred galaxies in five Sloan Digital Sky Survey (SDSS) bands (ugriz). This sample of ~3500 nearby (z<0.06) galaxies with strong bars selected from the Galaxy Zoo citizen science project is the largest sample of barred galaxies to be studied using photometric decompositions that include a bar component. With detailed structural analysis, we obtain physical quantities such as the bar- and bulge-to-total luminosity ratios, effective radii, Sersic indices and colours of the individual components. We observe a clear difference in the colours of the components, the discs being bluer than the bars and bulges. An overwhelming fraction of bulge components have Sersic indices consistent with being pseudo-bulges. By comparing the barred galaxies with a mass-matched and volume-limited sample of unbarred galaxies, we examine the connection between the presence of a large-scale galactic bar and the properties of discs and bulges. We find that the discs of unbarred galaxies are significantly bluer compared to the discs of barred galaxies, while there is no significant difference in the colours of the bulges. We find possible evidence of secular evolution via bars that leads to the build-up of pseudo-bulges and to the quenching of star formation in the discs. We identify a subsample of unbarred galaxies with an inner lens/oval and find that their properties are similar to barred galaxies, consistent with an evolutionary scenario in which bars dissolve into lenses. This scenario deserves further investigation through both theoretical and observational work.
- ID:
- ivo://CDS.VizieR/J/MNRAS/439/1749
- Title:
- Barred S0 galaxies in the Coma cluster
- Short Name:
- J/MNRAS/439/1749
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study uses r-band images from the Eighth Data Release of the Sloan Digital Sky Survey (SDSS DR8) to study bars in lenticular (S0) galaxies in one of the nearest rich cluster environments, the Coma cluster. We develop techniques for bar detection and assess their success when applied to SDSS image data. To detect and characterize bars, we perform 2D bulge+disc+bar light decompositions of galaxy images with galfit. Using a sample of artificial galaxy images, we determine the faintest magnitude at which bars can be successfully measured at the depth and resolution of SDSS. We perform detailed decompositions of 83 S0 galaxies in Coma, 64 from a central sample, and 19 from a cluster outskirt sample. For the central sample, the S0 bar fraction is 72^+5^_-6_%. This value is significantly higher than that obtained using an ellipse-fitting method for bar detection, 48^+6^_-6_%. At a fixed luminosity, barred S0s are redder in g-r colour than unbarred S0s by 0.02mag. The frequency and strength of bars increase towards fainter luminosities. Neither central metallicity nor stellar age distributions differ significantly between barred and unbarred S0s. There is an increase in the bar fraction towards the cluster core, but this is at a low significance level. Bars have at most a weak correlation with cluster-centric radius.
- ID:
- ivo://CDS.VizieR/J/A+A/584/A88
- Title:
- Barred & unbarred galaxies N, O abundance ratio
- Short Name:
- J/A+A/584/A88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Bar-induced gas inflows towards galaxy centres are recognised as a key agent for the secular evolution of galaxies. One immediate consequence of this inflow is the accumulation of gas in the centre of galaxies where it can form stars and alter the chemical and physical properties. Our aim is to study whether the properties of the ionised gas in the central parts of barred galaxies are altered by the presence of a bar and whether the change in central properties is related to bar and/or parent galaxy properties. We use a sample of nearby face-on disc galaxies with available SDSS spectra, morphological decomposition, and information on the stellar population of their bulges, to measure the internal Balmer extinction from the H{alpha} to H{beta} line ratio, star formation rate, and relevant line ratios to diagnose chemical abundances and gas density.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A34
- Title:
- Baryon Acoustic Oscillations in LRGs
- Short Name:
- J/A+A/542/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Baryon Acoustic Oscillations (BAO) have been previously detected using correlation functions and power spectra of the galaxy distribution. In this work, we present a new method for the detection of the real-space structures associated with this feature. These baryon acoustic structures are spherical shells with a relatively small density contrast, surrounding high density central regions. We design a specific wavelet adapted to the search for shells, and exploit the physics of the process by making use of two different mass tracers, introducing a specific statistic to detect the BAO features. We apply our method to the detection of BAO in a galaxy sample drawn from the Sloan Digital Sky Survey (SDSS). We use the 'Main' catalogue to trace the shells, and the Luminous Red Galaxies (LRG) as tracers of the high density central regions.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A66
- Title:
- Baryons from groups and clusters of galaxies
- Short Name:
- J/A+A/555/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on XMM-Newton, Chandra, and SDSS data, we investigate the baryon distribution in groups and clusters and its use as a cosmological constraint. For this, we considered a sample of 123 systems with temperatures kT_500_=1.0-9.0keV, total masses in the mass range M_500_=(~10^13^-4x10^15^)h_70_^-1^M_{sun}_, and redshifts 0.02<z<1.3. The gas masses and total masses are derived from X-ray data under the assumption of hydrostatic equilibrium and spherical symmetry. The stellar masses are based on SDSS-DR8 optical photometric data. For the 37 systems out of 123 that had both optical and X-ray data available, we investigated the gas, stellar, and total baryon mass fractions inside r2500 and r500 and the differential gas mass fraction within the spherical annulus between r2500 and r500, as a function of total mass. For the other objects, we investigated the gas mass fraction only.
- ID:
- ivo://CDS.VizieR/J/ApJ/791/128
- Title:
- Basic galaxy data for spiral-rich group members
- Short Name:
- J/ApJ/791/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, the COS Science Team has conducted a high signal-to-noise survey of 14 bright QSOs. In a previous paper (Savage et al., 2014ApJS..212....8S), these far-UV spectra were used to discover 14 "warm" (T >= 10^5^ K) absorbers using a combination of broad Ly{alpha} and broad O VI absorptions. A reanalysis of a few of this new class of absorbers using slightly relaxed fitting criteria finds as many as 20 warm absorbers could be present in this sample. A shallow, wide spectroscopic galaxy redshift survey has been conducted around these sight lines to investigate the warm absorber environment, which is found to be spiral-rich groups or cluster outskirts with radial velocity dispersions {sigma}=250-750 km/s. While 2{sigma} evidence is presented favoring the hypothesis that these absorptions are associated with the galaxy groups and not with the individual, nearest galaxies, this evidence has considerable systematic uncertainties and is based on a small sample size so it is not entirely conclusive. If the associations are with galaxy groups, the observed frequency of warm absorbers (idN/dz = 3.5-5 per unit redshift) requires them to be very extended as an ensemble on the sky (~1 Mpc in radius at high covering factor). Most likely these warm absorbers are interface gas clouds whose presence implies the existence of a hotter (T ~ 10^6.5^ K), diffuse, and probably very massive (>10^11^ M_{sun}_) intra-group medium which has yet to be detected directly.
