- ID:
- ivo://CDS.VizieR/J/A+A/574/A126
- Title:
- HeViCS. XVIII. Star-forming dwarf galaxies
- Short Name:
- J/A+A/574/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To assess the effects of the cluster environment on the different components of the interstellar medium, we analyse the far-infrared (FIR) and submillimetre (submm) properties of a sample of star-forming dwarf galaxies detected by the Herschel Virgo Cluster Survey (HeViCS). We determine dust masses and dust temperatures by fitting a modified black body function to the spectral energy distributions (SEDs). Stellar and gas masses, star formation rates (SFRs), and metallicities are obtained from the analysis of a set of ancillary data. Dust is detected in 49 out of a total 140 optically identified dwarfs covered by the HeViCS field; considering only dwarfs brighter than m_B_=18mag, this gives a detection rate of 43%. After evaluating different emissivity indices, we find that the FIR-submm SEDs are best-fit by {beta}=1.5, with a median dust temperature T_d_=22.4K. Assuming {beta}=1.5, 67% of the 23 galaxies detected in all five Herschel bands show emission at 500{mu}m in excess of the modified black-body model. The fraction of galaxies with a submillimetre excess decreases for lower values of {beta}, while a similarly high fraction (54%) is found if a {beta}-free SED modelling is applied. The excess is inversely correlated with SFR and stellar masses. To study the variations in the global properties of our sample that come from environmental effects, we compare the Virgo dwarfs to other Herschel surveys, such as the Key Insights into Nearby Galaxies: Far-Infrared Survey with Herschel (KINGFISH), the Dwarf Galaxy Survey (DGS), and the HeViCS Bright Galaxy Catalogue (BGC). We explore the relations between stellar mass and HI fraction, specific star formation rate, dust fraction, gas-to-dust ratio over a wide range of stellar masses (from 10^7^ to 10^11^M_{sun}_) for both dwarfs and spirals. Highly HI-deficient Virgo dwarf galaxies are mostly characterised by quenched star formation activity and lower dust fractions giving hints for dust stripping in cluster dwarfs. However, to explain the large dust-to-gas mass ratios observed in these systems, we find that the fraction of dust removed has to be less than that of the HI component. The cluster environment seems to mostly affect the gas component and star formation activity of the dwarfs. Since the Virgo star-forming dwarfs are likely to be crossing the cluster for the first time, a longer timescale might be necessary to strip the more centrally concentrated dust distribution.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/597/A130
- Title:
- HI and 250um images of the Virgo cirrus
- Short Name:
- J/A+A/597/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the correlation between far-infrared/submm dust emission and atomic gas column density in order to derive the properties of the high Galactic latitude, low density, Milky Way cirrus in the foreground of the Virgo cluster of galaxies. Dust emission maps from 60 to 850um are obtained from SPIRE observations carried out within the Herschel Virgo Cluster Survey, complemented by IRAS-IRIS and Planck-HFI maps. Data from the Arecibo legacy Fast ALFA Survey is used to derive atomic gas column densities for two broad velocity components, low and intermediate velocity clouds. Dust emissivities are derived for each gas component and each far-infrared/submm band. For the low velocity clouds, we measure an average emissivity {epsilon]_{nu}^LVC=(0.79+/-0.08)*10^-20^MJy.cm^2^/sr at 250um. After fitting a modified blackbody to the available bands, we estimated a dust absorption cross-section {tau}_{nu}^LVC/N_HI_=(0.49+/-0.13)*10^-25cm^2^/H at 250um (with dust temperature T=20.4+/-1.5K and spectral index {beta}=1.53+/-0.17). The results are in excellent agreement with those obtained by Planck over a much larger coverage of the high Galactic latitude cirrus (50% of the sky vs 0.2% in our work). For dust associated with intermediate velocity gas, we confirm earlier Planck results and find a higher temperature and lower emissivity and cross-section. After subtracting the modelled components, we find regions at scales smaller than 20' where the residuals deviate significantly from the average, cosmic-infrared-background dominated, scatter. These large residuals are most likely due to local variations in the cirrus dust properties (and/or the dust/atomic-gas correlation) or to high-latitude molecular clouds with average N_H2_<~10^20^cm^-2^. We find no conclusive evidence for intracluster dust emission in Virgo.
- ID:
- ivo://CDS.VizieR/J/A+A/594/A58
- Title:
- Hi-GAL l=224deg region CO(1-0) data cubes
- Short Name:
- J/A+A/594/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars form in dense, dusty structures, which are embedded in larger clumps of molecular clouds often showing a clear filamentary structure on large scales (>1pc). The origin (e.g., turbulence or gravitational instabilities) and evolution of these filaments, as well as their relation to clump and core formation, are not yet fully understood. A large sample of both starless and protostellar clumps can now be found in the Herschel Hi-GAL (Herschel Infrared GALactic Plane Survey) key project, which also provides striking images of the filamentary structure of the parent molecular clouds. Recent results indicate that populations of clumps on and off filaments may differ. One of the best studied regions in the Hi-GAL survey can be observed toward the l=224{deg} field. Here, a filamentary region has been studied and it has been found that protostellar clumps are mostly located along the main filament, whereas starless clumps are detected off this filament and are instead found on secondary, less prominent filaments. We want to investigate this segregation effect and how it may affect the clumps properties. We mapped the ^12^CO(1-0) line and its main three isotopologues toward the two most prominent filaments observed toward the l=224{deg} field using the Mopra radio telescope, in order to set observational constraints on the dynamics of these structures and the associated starless and protostellar clumps. Compared to the starless clumps, the protostellar clumps are more luminous, more turbulent and lie in regions where the filamentary ambient gas shows larger linewidths. We see evidence of gas flowing along the main filament, but we do not find any signs of accretion flow from the filament onto the Hi-GAL clumps. We analyze the radial column density profile of the filaments and their gravitational stability. The more massive and highly fragmented main filament appears to be thermally supercritical and gravitationally bound, assuming that all of the non-thermal motion is contributing thermal-like support, suggesting a later stage of evolution compared to the secondary filament. The status and evolutionary phase of the Hi-GAL clumps would then appear to correlate with that of the host filament.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A88
- Title:
- High cadence polarization monitoring of OJ287
- Short Name:
- J/A+A/619/A88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multifrequency, dense radio monitoring program of the blazar OJ287 using the 100-m Effelsberg radio telescope. The program aims to test different binary supermassive black hole (SMBH) scenarios and studying the physical conditions in the central region of this bright blazar. Between December 2015 and January 2017 (MJD 57370-57785), the radio electric vector position angle (EVPA) showed a large clockwise (CW) rotation by about 340{deg} with a mean rate of -1.04{deg}/day. Based on concurrent polarized Very Long Baseline Array (VLBA) data, the rotation seems to originate within the jet core at 43GHz. Optical polarization data show a similar monotonic CW EVPA rotation of about -1.1{deg}/day, superposed by shorter and faster rotations of about 7.8{deg}/day, mainly in the CW sense. When combined, the single dish, VLBI and optical polarization data are consistent with a polarized emission component propagating on a helical trajectory within a bent jet. We constrained the helix arc length (0.26pc) and radius (about 0.04pc) and the projected jet bending arc length (about 1.9-7.6pc). The helical trajectory covers only a part of the jet width, possibly its spine. In addition, we found a stable polarized component with EVPA (-10{deg}) perpendicular to the large scale jet, suggesting dominance of the poloidal magnetic field component.
- ID:
- ivo://CDS.VizieR/J/ApJ/815/130
- Title:
- High-mass molecular clumps from MALT90
- Short Name:
- J/ApJ/815/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present dust column densities and dust temperatures for ~3000 young, high-mass molecular clumps from the Millimeter Astronomy Legacy Team 90GHz survey, derived from adjusting single-temperature dust emission models to the far-infrared intensity maps measured between 160 and 870{mu}m from the Herschel/Herschel Infrared Galactic Plane Survey (Hi-Gal) and APEX/APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) surveys. We discuss the methodology employed in analyzing the data, calculating physical parameters, and estimating their uncertainties. The population average dust temperature of the clumps are 16.8+/-0.2K for the clumps that do not exhibit mid-infrared signatures of star formation (quiescent clumps), 18.6+/-0.2K for the clumps that display mid-infrared signatures of ongoing star formation but have not yet developed an HII region (protostellar clumps), and 23.7+/-0.2 and 28.1+/-0.3K for clumps associated with HII and photo-dissociation regions, respectively. These four groups exhibit large overlaps in their temperature distributions, with dispersions ranging between 4 and 6K. The median of the peak column densities of the protostellar clump population is 0.20+/-0.02g/cm2, which is about 50% higher compared to the median of the peak column densities associated with clumps in the other evolutionary stages. We compare the dust temperatures and column densities measured toward the center of the clumps with the mean values of each clump. We find that in the quiescent clumps, the dust temperature increases toward the outer regions and that these clumps are associated with the shallowest column density profiles. In contrast, molecular clumps in the protostellar or HII region phase have dust temperature gradients more consistent with internal heating and are associated with steeper column density profiles compared with the quiescent clumps.
- ID:
- ivo://CDS.VizieR/J/A+A/498/147
- Title:
- High mass protostellar objects physical parameters
- Short Name:
- J/A+A/498/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a previous work (Paper I, Kumar & Grave, 2007A&A...472..155K) a sample of 380 HMPO targets was studied using the GLIMPSE point source catalog and images. A colour-magnitude analysis of the point sources resulted in the identification of infrared counterparts (IRC) of the (sub)mm cores of HMPO candidates which were considered bona fide targets. We aim to estimate and analyse the physical properties of the infrared counterparts of HMPOs by comparing their spectral energy distributions (SED) with those predicted by radiative transfer accretion models of YSOs.
- ID:
- ivo://CDS.VizieR/J/ApJS/231/11
- Title:
- High-mass starless clump candidates from ATLASGAL
- Short Name:
- J/ApJS/231/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a sample of 463 high-mass starless clump (HMSC) candidates within -60{deg}<l<60{deg} and -1{deg}<b<1{deg}. This sample has been singled out from 10861 ATLASGAL clumps. None of these sources are associated with any known star-forming activities collected in SIMBAD and young stellar objects identified using color-based criteria. We also make sure that the HMSC candidates have neither point sources at 24 and 70{mu}m nor strong extended emission at 24{mu}m. Most of the identified HMSCs are infrared dark, and some are even dark at 70{mu}m. Their distribution shows crowding in Galactic spiral arms and toward the Galactic center and some well-known star-forming complexes. Many HMSCs are associated with large-scale filaments. Some basic parameters were attained from column density and dust temperature maps constructed via fitting far-infrared and submillimeter continuum data to modified blackbodies. The HMSC candidates have sizes, masses, and densities similar to clumps associated with Class II methanol masers and H II regions, suggesting that they will evolve into star-forming clumps. More than 90% of the HMSC candidates have densities above some proposed thresholds for forming high-mass stars. With dust temperatures and luminosity-to-mass ratios significantly lower than that for star-forming sources, the HMSC candidates are externally heated and genuinely at very early stages of high-mass star formation. Twenty sources with equivalent radii r_eq_<0.15pc and mass surface densities {Sigma}>0.08g/cm^2^ could be possible high-mass starless cores. Further investigations toward these HMSCs would undoubtedly shed light on comprehensively understanding the birth of high-mass stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/675/49
- Title:
- High-redshift QSOs in the SWIRE survey
- Short Name:
- J/ApJ/675/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a simple optical/infrared (IR) photometric selection of high-redshift QSOs that identifies a Lyman break in the optical photometry and requires a red IR color to distinguish QSOs from common interlopers. The search yields 100 z~3 (U-dropout) QSO candidates with 19<r'<22 over 11.7deg^2^ in the ELAIS-N1 (EN1) and ELAIS-N2 (EN2) fields of the Spitzer Wide-area Infrared Extragalactic (SWIRE) Legacy Survey. The z~3 selection is reliable, with spectroscopic follow-up of 10 candidates confirming that they are all QSOs at 2.83<z<3.44. We find that our z~4 (g'-dropout) sample suffers from both unreliability and incompleteness but present seven previously unidentified QSOs at 3.50<z<3.89.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A37
- Title:
- High-z AGN obscured by host galaxy ISM
- Short Name:
- J/A+A/636/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Submillimeter Galaxies (SMGs) at high redshift are among the best targets to investigate the early evolutionary phases in the lifetime of massive systems, during which large gas reservoirs sustain vigorous star formation and efficiently feed the central, buried Super Massive Black Hole (SMBH). We present the analysis of new ALMA band 4 (1.8-2.4mm) continuum and high-J CO observation of six obscured QSOs (logN_H_>23) hosted by SMGs at z>2.5 in the 7 Ms Chandra Deep Field South (CDF-S). Sizes and masses of the galaxies are measured to estimate to which extent the host ISM may contribute to the nuclear absorption. We found that at high redshift the galaxy ISM can substantially contribute to the AGN obscuration up to the Compton-thick (10^24^cm^-2^) regime. In addition, we found that all the detected sources show a velocity gradient possibly ascribed to a rotating system, even though two of them could be even associated with a chaotic, possibly merging, structure.
- ID:
- ivo://CDS.VizieR/J/A+A/637/A40
- Title:
- HMSCs classification and physical parameters
- Short Name:
- J/A+A/637/A40
- Date:
- 07 Dec 2021 10:47:33
- Publisher:
- CDS
- Description:
- The role of ionization feedback on high-mass (>8M_{sun}_) star formation is still highly debated. Questions remain concerning the presence of nearby HII regions changes the properties of early high-mass star formation and whether H ii regions promote or inhibit the formation of high-mass stars. To characterize the role of HII regions on the formation of high-mass stars, we study the properties of a sample of candidates high-mass starless clumps (HMSCs), of which about 90% have masses larger than 100 Msun. These high-mass objects probably represent the earliest stages of high-mass star formation; we search if (and how) their properties are modified by the presence of an HII region. We took advantage of the recently published catalog of HMSC candidates. By cross matching the HMSCs and HII regions, we classified HMSCs into three categories: 1) The HMSCs associated with HII regions both in the position in the projected plane of the sky and in velocity; 2) HMSCs associated in the plane of the sky, but not in velocity; and 3) HMSCs far away from any HII regions in the projected sky plane. We carried out comparisons between associated and non-associated HMSCs based on statistical analyses of multiwavelength data from infrared to radio. We show that there are systematic differences of the properties of HMSCs in different environments. Statistical analyses suggest that HMSCs associated with HII regions are warmer, more luminous, more centrally-peaked and turbulent. We also clearly show, for the first time, that the ratio of bolometric luminosity to envelope mass of HMSCs (L/M) could not be a reliable evolutionary probe for early massive star formation due to the external heating effects of the HII regions. We show HMSCs associated with HII regions present statistically significant differences from HMSCs far away from HII regions, especially for dust temperature and L/M. More centrally peaked and turbulent properties of HMSCs associated with HII regions may promote the formation of high-mass stars by limiting fragmentation. High-resolution interferometric surveys toward HMSCs are crucial to reveal how HII regions impact the star formation process inside HMSCs.