- ID:
- ivo://CDS.VizieR/J/A+A/645/A113
- Title:
- Southern outer Galaxy star forming regions
- Short Name:
- J/A+A/645/A113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star formation in the outer Galaxy is thought to be different from that in the inner Galaxy, as it is subject to different environmental parameters such as metallicity, interstellar radiation field, or mass surface density, which all change with galactocentric radius. Extending our star formation knowledge, from the inner to the outer Galaxy, helps us to understand the influences of the change of the environment on star formation throughout the Milky Way. We aim to obtain a more detailed view on the structure of the outer Galaxy, determining physical properties for a large number of star forming clumps and understanding star formation outside the solar circle. As one of the largest expanding Galactic super-shellsis present in the observed region, a unique opportunity is taken here to investigate the influence of such an expanding structure on star formation as well. We used pointed ^12^CO(2-1) observations conducted with the APEX telescope to determine the velocity components towards 830 dust clumps identified from 250um Herschel/Hi-GAL SPIRE emission maps in the outer Galaxy between 225<l<260. We determined kinematic distances from the velocity components, in order to analyze the structure of the outer Galaxy and to estimate physical properties such as dust temperatures, bolometric luminosities, clump masses, and H2 column densities for 611 clumps. Forthis, we determined the dust spectral energy density distributions from archival mid-infrared to sub- millimeter (submm) emission maps. We find the identified CO clouds to be strongly correlated with the highest column density parts of the Hiemission distribution, spanning a web of bridges, spurs, and blobs of star forming regions between the larger complexes, unveiling the complex three-dimensional structure of the outer Galaxy in unprecedented detail. Using the physical properties of the clumps, we find an upper limit of 6% (40 sources) capable of forming high-mass stars. This is supported by the fact that only two methanol Class II masers,or 34 known or candidate HII regions, are found in the whole survey area, indicating an even lower fraction that are able to form high-mass stars in the outer Galaxy. We fail to find any correlation of the physical parameters of the identified (potential) star forming regions with the expanding supershell, indicating that although the shell organizes the interstellar material into clumps, the properties of the latter are unaffected. Using the APEX telescope in combination with publicly available Hi-GAL, MSX, and Wise continuum emission maps, we were able to investigate the structure and properties of a region of the Milky Way in unprecedented detail.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/155/234
- Title:
- Star formation rate distribution in NGC 1232
- Short Name:
- J/AJ/155/234
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- NGC 1232 is a face-on spiral galaxy and a great laboratory for the study of star formation due to its proximity. We obtained high spatial resolution H{alpha} images of this galaxy, with adaptive optics, using the SAM instrument at the SOAR telescope, and used these images to study its H II regions. These observations allowed us to produce the most complete H II region catalog for it to date, with a total of 976 sources. This doubles the number of H II regions previously found for this object. We used these data to construct the H II luminosity function, and obtained a power-law index lower than the typical values found for Sc galaxies. This shallower slope is related to the presence of a significant number of high-luminosity H II regions (log L>39 dex). We also constructed the size distribution function, verifying that, as for most galaxies, NGC 1232 follows an exponential law. We also used the H{alpha} luminosity to calculate the star formation rate. An extremely interesting fact about this galaxy is that X-ray diffuse observations suggest that NGC 1232 recently suffered a collision with a dwarf galaxy. We found an absence of star formation around the region where the X-ray emission is more intense, which we interpret as a star formation quenching due to the collision. Along with that, we found an excess of star-forming regions in the northeast part of the galaxy, where the X-ray emission is less intense.
- ID:
- ivo://CDS.VizieR/J/ApJ/888/92
- Title:
- Star-forming clumps in local luminous IR galaxies
- Short Name:
- J/ApJ/888/92
- Date:
- 25 Oct 2021 10:18:57
- Publisher:
- CDS
- Description:
- We present HST narrowband near-infrared imaging of Pa{alpha} and Pa{beta} emission of 48 local luminous infrared galaxies (LIRGs) from the Great Observatories All-Sky LIRG Survey. These data allow us to measure the properties of 810 spatially resolved star-forming regions (59 nuclei and 751 extranuclear clumps) and directly compare their properties to those found in both local and high-redshift star-forming galaxies. We find that in LIRGs the star-forming clumps have radii ranging from ~90 to 900pc and star formation rates (SFRs) of ~1x10^-3^ to 10M_{sun}_/yr, with median values for extranuclear clumps of 170pc and 0.03M_{sun}_/yr. The detected star-forming clumps are young, with a median stellar age of 8.7Myr, and have a median stellar mass of 5x10^5^M_{sun}_. The SFRs span the range of those found in normal local star-forming galaxies to those found in high-redshift star-forming galaxies at z=1-3. The luminosity function of the LIRG clumps has a flatter slope than found in lower-luminosity, star-forming galaxies, indicating a relative excess of luminous star-forming clumps. In order to predict the possible range of star-forming histories and gas fractions, we compare the star-forming clumps to those measured in the MassiveFIRE high-resolution cosmological simulation. The star-forming clumps in MassiveFIRE cover the same range of SFRs and sizes found in the local LIRGs and have total gas fractions that extend from 10% to 90%. If local LIRGs are similar to these simulated galaxies, we expect that future observations with ALMA will find a large range of gas fractions, and corresponding star formation efficiencies, among the star-forming clumps in LIRGs.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/20
- Title:
- Stellar groups in Taurus field from Gaia DR2 & LAMOST
- Short Name:
- J/ApJS/254/20
- Date:
- 17 Jan 2022 14:18:37
- Publisher:
- CDS
- Description:
- In this work, we present a systematic search for stellar groups in the Taurus field by applying the DBSCAN algorithm to the data from Gaia DR2. We find 22 groups, consisting of 8 young groups (Groups 1-8) at ages of 2-4Myr and distances of ~130-170pc, and 14 old groups (Groups 9-22) at ages of 8-49Myr and distances of ~110-210pc. We characterize the disk properties of group members and find 19 new disk-bearing stars, 8 of which are in the young groups with 11 others belonging to the comparatively old groups at the ages of 8-11Myr. We characterize the accretion properties of the group members with H{alpha} emission lines in their Large Sky Area Multi-Object Fibre Spectroscopic Telescope spectra, and discover one source in Group 10 at an age of 10Myr which still shows accretion activity. We investigate the kinematic relations among the old groups, find that Group 9 is kinematically related to the known Taurus members, and exclude any kinematic relations between Groups 10-22 and the known Taurus members.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/35
- Title:
- Stellar population synthesis of clumps
- Short Name:
- J/ApJS/234/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 1027 star-forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star-forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in 8{mu}m observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution of our clumps with the Code Investigating GALaxy Emission using a double exponentially declined star formation history. We derive the star formation rates (SFRs), stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an active galactic nucleus for these clumps. The resolved star formation main sequence holds on 2.5kpc scales, although it does not hold on 1kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that the SFR is enhanced through the disk and in the tidal features relative to normal spirals.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/89
- Title:
- Structure of 1263 galaxies in Stripe 82 region
- Short Name:
- J/ApJ/899/89
- Date:
- 07 Mar 2022 13:26:50
- Publisher:
- CDS
- Description:
- Establishing a correlation (or lack thereof) between the bimodal color distribution of galaxies and their structural parameters is crucial to understand the origin of bimodality. To achieve that, we have performed a 2D mass-based structural decomposition (bulge+disk) of all disk galaxies (total=1263) in the Herschel imaging area of the Stripe 82 region using Ks-band images from the VICS82 survey. The scaling relations thus derived are found to reflect the internal kinematics and are employed in combination to select an indubitable set of classical- and pseudo-bulge-hosting disk galaxies. The rest of the galaxies (<20%) are marked as disks with "ambiguous" bulges. Pseudo- and classical bulge-disk galaxies exhibit clear bimodality in terms of all stellar parameters (M*, specific star formation rate, r-Ks). All pseudo- bulge-disk galaxies are blue and star forming, and all classical bulge-disk galaxies are red and quiescent with less than 5% digressions. Ambiguous bulge- disk galaxies are intermediate to pseudo- and classical bulge-disk galaxies in the distribution of all structural and stellar parameters. {Delta}<{mu}_eb_>-based on the placement of bulges on the Kormendy relation-is found to be the most efficient single structural indicator of both bulge type and stellar activity. The placement of ambiguous bulge-disk galaxies on scaling relations and the fundamental plane, in addition to their peculiar stellar properties, suggests that they are dominantly part of the green valley.
- ID:
- ivo://CDS.VizieR/J/AJ/162/28
- Title:
- Studying of protoplanetary disks in SFRs with ALMA
- Short Name:
- J/AJ/162/28
- Date:
- 14 Mar 2022 06:54:01
- Publisher:
- CDS
- Description:
- Gaps in protoplanetary disks have long been hailed as signposts of planet formation. However, a direct link between exoplanets and disks remains hard to identify. We present a large sample study of ALMA disk surveys of nearby star-forming regions to disentangle this connection. All disks are classified as either structured (transition, ring, extended) or nonstructured (compact) disks. Although low-resolution observations may not identify large-scale substructure, we assume that an extended disk must contain substructure from a dust evolution argument. A comparison across ages reveals that structured disks retain high dust masses up to at least 10Myr, whereas the dust mass of compact, nonstructured disks decreases over time. This can be understood if the dust mass evolves primarily by radial drift, unless drift is prevented by pressure bumps. We identify a stellar mass dependence of the fraction of structured disks. We propose a scenario linking this dependence with that of giant exoplanet occurrence rates. We show that there are enough exoplanets to account for the observed disk structures if transitional disks are created by exoplanets more massive than Jupiter and ring disks by exoplanets more massive than Neptune, under the assumption that most of those planets eventually migrate inwards. On the other hand, the known anticorrelation between transiting super-Earths and stellar mass implies those planets must form in the disks without observed structure, consistent with formation through pebble accretion in drift-dominated disks. These findings support an evolutionary scenario where the early formation of giant planets determines the disk's dust evolution and its observational appearance.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A107
- Title:
- (Sub)millimeter RRL in high-mass star-forming clumps
- Short Name:
- J/A+A/616/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous radio recombination line (RRL) observations of dust clumps identified in the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) have led to the detection of a large number of RRLs in the 3mm range. Here, we aim to study their excitation with shorter wavelength (sub)millimeter radio recombination line (submm-RRL) observations. We made observations of submm-RRLs with low principal quantum numbers (n<=30) using the APEX 12m telescope, toward 104 HII regions associated with massive dust clumps from ATLASGAL. The observations covered the H25{alpha}, H28{alpha}, and H35{beta} transitions. Toward a small subsample the H26{alpha}, H27{alpha}, H29{alpha}, and H30{alpha} lines were observed to avoid contamination by molecular lines at adjacent frequencies. We have detected submm-RRLs (signal-to-noise >=3{sigma}) from compact HII regions embedded within 93 clumps. The submm-RRLs are approximately a factor of two brighter than the mm-RRLs and consistent with optically thin emission in local thermodynamic equilibrium (LTE). The average ratio (0.31) of the measured H35{beta}/H28{alpha} fluxes is close to the LTE value of 0.28. No indication of RRL maser emission has been found. The Lyman photon flux, bolometric, and submm-RRL luminosities toward the submm-RRL detected sources present significant correlations. The trends of dust temperature and the ratio of bolometric luminosity to clump mass, L_bol_/M_clump_, indicate that the HII regions are related to L_bol_/M_clump_, indicate that the HII regions are related to the most massive and luminous clumps. By estimating the production rate of ionizing photons, Q, from the submm-RRL flux, we find that the Q(H28{alpha}) measurements provide estimates of the Lyman continuum photon flux consistent with those determined from 5GHz radio continuum emission. Six RRL sources show line profiles that are a combination of a narrow and a broad Gaussian feature. The broad features are likely associated with high-velocity ionized flows. We have detected submm-RRLs toward 93 ATLASGAL clumps. Six RRL sources have high-velocity RRL components likely driven by high-velocity ionized flows. Their observed properties are consistent with thermal emission that correlates well with the Lyman continuum flux of the HII regions. The sample of HII regions with mm/submm-RRL detections probes, in our Galaxy, luminous clumps (L_bol_>10^4^L_{sun}_) with high L_bol_/M_clump_. We also provide suitable candidates for further studies of the morphology and kinematics of embedded, compact HII regions with the Atacama Large Millimeter/submillimeter Array (ALMA).
- ID:
- ivo://CDS.VizieR/J/ApJ/899/145
- Title:
- Sulfur isotopes in SFR with 12m ARO and 30m IRAM
- Short Name:
- J/ApJ/899/145
- Date:
- 14 Mar 2022 07:08:41
- Publisher:
- CDS
- Description:
- We present observations of 12C32S, 12C34S, 13C32S, and 12C33S J=2-1 lines toward a large sample of massive star-forming regions by using the Arizona Radio Observatory 12m telescope and the IRAM 30m. Taking new measurements of the carbon 12C/13C ratio, the 32S/34S isotope ratio was determined from the integrated 13C32S/12C34S line intensity ratios for our sample. Our analysis shows a 32S/34S gradient from the inner Galaxy out to a galactocentric distance of 12kpc. An unweighted least-squares fit to our data yields 32S/34S=(1.56{+/-}0.17)DGC+(6.75{+/-}1.22) with a correlation coefficient of 0.77. Errors represent 1{sigma} standard deviations. Testing this result by (a) excluding the Galactic center region, (b) excluding all sources with C34S opacities >0.25, (c) combining our data and old data from previous study, and (d) using different sets of carbon isotope ratios leads to the conclusion that the observed 32S/34S gradient is not an artifact but persists irrespective of the choice of sample and carbon isotope data. A gradient with rising 32S/34S values as a function of galactocentric radius implies that the solar system ratio should be larger than that of the local interstellar medium. With the new carbon isotope ratios, we indeed obtain a local 32S/34S isotope ratio about 10% below the solar system one, as expected in the case of decreasing 32S/34S ratios with time and increased amounts of stellar processing. However, taking older carbon isotope ratios based on a lesser amount of data, such a decrease is not seen. No systematic variation of 34S/33S ratios along galactocentric distance was found. The average value is 5.9{+/-}1.5, the error denoting the standard deviation of an individual measurement.
- ID:
- ivo://CDS.VizieR/J/AJ/160/242
- Title:
- The H{alpha} dots survey. II. 119 new dots
- Short Name:
- J/AJ/160/242
- Date:
- 09 Mar 2022 22:00:00
- Publisher:
- CDS
- Description:
- We present the second catalog of serendipitously discovered compact extragalactic emission-line sources-H{alpha} Dots. These objects have been discovered in searches of moderately deep narrow-band images acquired for the ALFALFA H{alpha} project. In addition to cataloging 119 new H{alpha} Dots, we also present follow-up spectral data for the full sample. These spectra allow us to confirm the nature of these objects as true extragalactic emission-line objects, to classify them in terms of activity type (star-forming or AGN), and to identify the emission line via which they were discovered. We tabulate photometric and spectroscopic data for the all objects, and we present an overview of the properties of the full H{alpha} Dot sample. The H{alpha} Dots represent a broad range of star-forming and active galaxies detected via several different emission lines over a wide range of redshifts. The sample includes H{alpha}-detected blue compact dwarf galaxies at low redshift, [OIII]-detected Seyfert 2 and Green Pea-like galaxies at intermediate redshifts, and QSOs detected via one of several UV emission lines, including Ly{alpha}. Despite the heterogeneous appearance of the resulting catalog of objects, we show that our selection method leads to well-defined samples of specific classes of emission-line objects with properties that allow for statistical studies of each class.
