- ID:
- ivo://CDS.VizieR/J/A+A/592/A122
- Title:
- Starburst galaxies in the COSMOS field
- Short Name:
- J/A+A/592/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At high redshift, starburst galaxies present irregular morphologies, with 10-20% of their star formation occurring in giant clumps. These clumpy galaxies are considered to be the progenitors of local disk galaxies. To understand the properties of starbursts at intermediate and low redshift, it is fundamental to track their evolution and possible link with the systems at higher z. We present an extensive, systematic, and multi-band search and analysis of the starburst galaxies at redshift (0<z<0.5) in the COSMOS field, as well as detailed characteristics of their star-forming clumps by using Hubble Space Telescope/Advance Camera for Surveys (HST/ACS) images. The starburst galaxies are identified using a tailor-made intermediate-band color excess selection, tracing the simultaneous presence of H{alpha} and [OIII] emission lines in the galaxies. Our methodology uses previous information from the zCOSMOS spectral database to calibrate the color excess as a function of the equivalent width of both spectral lines. This technique allows us to identify 220 starburst galaxies at redshift 0<z<0.5 using the SUBARU intermediate-band filters. Combining the high spatial resolution images from the HST/ACS with ground-based multi-wavelength photometry we identify and parametrize the star-forming clumps in every galaxy. Their principal properties, sizes, masses, and star formation rates are provided.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/609/A13
- Title:
- Star cluster Gaia 1 stars equivalent widths
- Short Name:
- J/A+A/609/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star clusters, particularly those objects in the disk-bulge-halo interface are as yet poorly charted, despite the fact that they carry important information about the formation and the structure of the Milky Way. Here, we present a detailed chemical abundance study of the recently discovered object Gaia 1. Photometry has previously suggested it as an intermediate-age, moderately metal-rich system, although the exact values for its age and metallicity remained ambiguous in the literature. We measured detailed chemical abundances of 14 elements in four red giant members, from high-resolution (R=25000) spectra that firmly establish Gaia 1 as an object associated with the thick disk. The resulting mean Fe abundance is -0.62+/-0.03(stat.)+/-0.10(sys.) dex, which is more metal-poor than indicated by previous spectroscopy from the literature, but it is fully in line with values from isochrone fitting. We find that Gaia 1 is moderately enhanced in the {alpha}-elements, which allowed us to consolidate its membership with the thick disk via chemical tagging. The cluster's Fe-peak and neutron-capture elements are similar to those found across the metal-rich disks, where the latter indicate some level of s-process activity. No significant spread in iron nor in other heavy elements was detected, whereas we find evidence of light-element variations in Na, Mg, and Al. Nonetheless, the traditional Na-O and Mg-Al (anti-)correlations, typically seen in old globular clusters, are not seen in our data. This confirms that Gaia 1 is rather a massive and luminous open cluster than a low-mass globular cluster. Finally, orbital computations of the target stars bolster our chemical findings of Gaia 1's present-day membership with the thick disk, even though it remains unclear which mechanisms put it in that place.
- ID:
- ivo://CDS.VizieR/J/ApJ/613/914
- Title:
- Star formation in HI-selected galaxies
- Short Name:
- J/ApJ/613/914
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 69 galaxies with radial velocities of less than 2500km/s was selected from the HI Parkes All-Sky Survey (HIPASS, Cat. <VIII/73>) and imaged in broadband B and R and narrowband H{alpha}, to deduce details about star formation in nearby disk galaxies while avoiding surface brightness selection effects.
- ID:
- ivo://CDS.VizieR/J/ApJS/174/337
- Title:
- Star formation in nuclear rings
- Short Name:
- J/ApJS/174/337
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a photometric H{alpha} survey of 22 nuclear rings, aiming to provide insight into their star formation properties, including age distribution, dynamical timescales, star formation rates, and galactic bar influence. We find a clear relationship between the position angles and ellipticities of the rings and those of their host galaxies, which indicates the rings are in the same plane as the disk and circular. We use population synthesis models to estimate ages of each H{alpha}-emitting (HII) region, which range from 1 to 10Myr throughout the rings. We find that approximately half of the rings contain azimuthal age gradients that encompass at least 25% of the ring, although there is no apparent relationship between the presence or absence of age gradients and the morphology of the rings or their host galaxies. NGC 1343, NGC 1530, and NGC 4321 show clear bipolar age gradients, where the youngest HII regions are located near the two contact points of the bar and ring. We speculate in these cases that the gradients are related to an increased mass inflow rate and/or an overall higher gas density in the ring, which would allow for massive star formation to occur on short timescales, after which the galactic rotation would transport the HII regions around the ring as they age. Two-thirds of the barred galaxies show correlation between the locations of the youngest HII region(s) in the ring and the location of the contact points, which is consistent with predictions from numerical modeling.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A8
- Title:
- Star-forming regions in NGC 2903 bar
- Short Name:
- J/A+A/521/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nearby barred spiral NGC 2903 has an active starburst at its centre and HII regions distributed along its bar. We analyse the star-formation properties in the bar region of NGC 2903 and study its links to the typical bar morphological features. We combine space and ground-based data from the far-ultraviolet to the sub-millimeter spectral ranges to create a panchromatic view of the NGC 2903 bar. We produce two catalogues: one for the current star-formation regions, as traced by the H{alpha} compact emission, and a second for the ultraviolet (UV) emitting knots, containing positions and luminosities. From them, we obtain ultraviolet colours, star-formation rates, dust attenuation, and H{alpha} EWs, and analyse their spatial distribution. We estimate stellar cluster ages using stellar population synthesis models (Starburst99).
- ID:
- ivo://CDS.VizieR/J/AJ/103/1987
- Title:
- Stars of very low metal abundance
- Short Name:
- J/AJ/103/1987
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic observations for 1044 stars located primarily in the southern Galactic hemisphere are reported; the stars were chosen from a list of candidate metal-deficient stars discovered in the HK objective-prism survey. Radial velocities and line indices based on the equivalent widths of Ca II, K, H-gamma and H-delta, and the CH G band are reported. Estimates of metallicity for 874 stars with derived abundances less than -0.5 are presented.
- ID:
- ivo://CDS.VizieR/J/AJ/147/136
- Title:
- Stars of very low metal abundance. VI. Abundances
- Short Name:
- J/AJ/147/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities, equivalent widths, model atmosphere parameters, and abundances or upper limits for 53 species of 48 elements derived from high resolution optical spectroscopy of 313 metal-poor stars. A majority of these stars were selected from the metal-poor candidates of the HK Survey of Beers, Preston, and Shectman. We derive detailed abundances for 61% of these stars for the first time. Spectra were obtained during a 10yr observing campaign using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Telescopes at Las Campanas Observatory, the Robert G. Tull Coude Spectrograph on the Harlan J. Smith Telescope at McDonald Observatory, and the High Resolution Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory. We perform a standard LTE abundance analysis using MARCS model atmospheres, and we apply line-by-line statistical corrections to minimize systematic abundance differences arising when different sets of lines are available for analysis. We identify several abundance correlations with effective temperature. A comparison with previous abundance analyses reveals significant differences in stellar parameters, which we investigate in detail. Our metallicities are, on average, lower by {approx}0.25dex for red giants and {approx}0.04dex for subgiants. Our sample contains 19 stars with [Fe/H]<=-3.5, 84 stars with [Fe/H]<=-3.0, and 210 stars with [Fe/H]<=-2.5. Detailed abundances are presented here or elsewhere for 91% of the 209 stars with [Fe/H]<=-2.5 as estimated from medium resolution spectroscopy by Beers, Preston, and Shectman. We will discuss the interpretation of these abundances in subsequent papers.
- ID:
- ivo://CDS.VizieR/III/120
- Title:
- Stars with CaII H and K emission
- Short Name:
- III/120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intensities and widths of emission cores of H and K lines from the literature are presented for over 1400 stars of spectral types F, G, K and M.
- ID:
- ivo://CDS.VizieR/J/A+AS/142/275
- Title:
- Stellar activity of late-type stars
- Short Name:
- J/A+AS/142/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a spectroscopic CaII H&K survey of 1058 late-type stars selected from a color-limited subsample of the Hipparcos (Cat. <I/239>) catalog. Out of these 1058 stars, 371 stars were found to show significant H&K emission, most of them previously unknown; 23% with strong emission, 36% with moderate emission, and 41% with weak emission. These spectra are used to determine absolute H&K emission-line fluxes, radial velocities, and equivalent widths of the luminosity-sensitive Sr II line at 4077{AA}. Red-wavelength spectroscopic and Stroemgren y photometric follow-up observations of the 371 stars with H&K emission are used to additionally determine the absolute H{alpha}-core flux, the lithium abundance from the Li I 6708{AA} equivalent width, the rotational velocity vsini, the radial velocity, and the light variations and its periodicity.
- ID:
- ivo://CDS.VizieR/J/ApJS/251/29
- Title:
- Stellar bow shock nebulae spectroscopic obs.
- Short Name:
- J/ApJS/251/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Arcuate mid-infrared nebulae known as stellar bow shock nebulae (SBNe) have been previously hypothesized to be supported by the strong stellar winds and/or luminosity of massive early-type stars. We present an optical spectroscopic survey of 84 stars identified from mid-infrared images as candidate SBN-supporting stars. Eighty-one of 84 sources, 96%, are O or early-B spectral types. K-band luminosities for a larger sample of 289 stars at the centers of bow shock nebulae are overwhelmingly consistent with OB stars. This affirms both that SBNe are supported by massive stars and that arcuate mid-infrared nebulae are reliable indicators of the presence of a massive star. The radial velocity dispersions of these systems and detections of double-lined systems indicate that at least 27 of the 74 systems with multiple observations (>36%) are candidate multiple-star systems. This rate is consistent with observed multiplicity rates of field OB stars detected with similar radial velocity surveys and lower than, but not inconsistent with, the multiplicity rates of OB stars in clusters and associations.
