- ID:
- ivo://CDS.VizieR/J/A+A/562/A15
- Title:
- Star-forming galaxies in AKARI Deep Field-South
- Short Name:
- J/A+A/562/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The main aim of this work is the characterization of physical properties of galaxies detected in the far infrared (FIR) in the AKARI Deep Field-South (ADF-S) survey. Starting from a catalog of the brightest 1000 ADF-S sources in the WIDE-S (90um) AKARI band, we constructed a subsample of galaxies with spectral coverage from the ultraviolet to the far-infrared. Then, we analyzed the multiwavelength properties of this 90um-selected sample of galaxies. For galaxies without known spectroscopic redshifts we computed photometric redshifts using codes Le PHARE and CIGALE, tested these photometric redshifts using spectroscopic redshifts, and compared the performances of both codes. To test the reliability of parameters obtained by fitting Spectral Energy Distributions, a mock catalogue has been generated. We built a large multiwavelength catalog of more than 500 ADF-S galaxies. We successfully fitted Spectral Energy Distributions of 186 galaxies with {chi}^2^<4, and analyzed the output parameters of the fits. We conclude that our sample consists mostly of nearby actively star-forming galaxies, and all our galaxies have a relatively high metallicity. We estimated photometric redshifts for 113 galaxies from the whole ADF-S sample. Comparing the performance of Le PHARE and CIGALE, we found that CIGALE gives more reliable redshift estimates for our galaxies, which implies that including the IR photometry allows for substantial improvement of photometric redshift estimation.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/435/2861
- Title:
- Star-forming galaxies in near-IR
- Short Name:
- J/MNRAS/435/2861
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The near-infrared spectral region is becoming a very useful wavelength range to detect and quantify the stellar population of galaxies. Models are developing to predict the contribution of the thermally pulsating stars on the asymptotic giant branch stars that should dominate the near-infrared region (NIR) spectra of populations 0.3 to 2Gyr old. When present in a given stellar population, these stars leave unique signatures that can be used to detect them unambiguously. However, these models have to be tested in a homogeneous data base of star-forming galaxies, to check if the results are consistent with what is found from different wavelength ranges. In this work, we performed stellar population synthesis on the nuclear and extended regions of 23 star-forming galaxies to understand how the star formation tracers in the NIR can be used in practice. The stellar population synthesis shows that for the galaxies with strong emission in the NIR, there is an important fraction of young/intermediate population contributing to the spectra, which is probably the ionization source in these galaxies. Galaxies that had no emission lines measured in the NIR were found to have older average ages and less contribution of young populations. Although the stellar population synthesis method proved to be very effective to find the young ionizing population in these galaxies, no clear correlation between these results and the NIR spectral indexes were found. Thus, we believe that, in practice, the use of these indexes is still very limited due to observational limitations.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A114
- Title:
- Star-forming galaxies over 0.35<z<2.25
- Short Name:
- J/A+A/625/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To better constrain the physical mechanisms driving star formation, we present the first systematic study of the radio continuum size evolution of star-forming galaxies (SFGs) over the redshift range 0.35<z<2.25. We use the VLA COSMOS 3GHz map (noise rms=2.3Jy/beam, {theta}_beam_=0.75arcsec) to construct a mass-complete sample of 3184 radio-selected SFGs that reside on and above the main-sequence (MS) of SFGs. We constrain the overall extent of star formation activity in galaxies by applying a 2D-Gaussian model to their radio continuum emission. Extensive Monte Carlo simulations are used to validate the robustness of our measurements and characterize the selection function. We find no clear dependence between the radio size and stellar mass, M*, of SFGs with 10.5<log(M*/M_{sun}_)<11.5. Our analysis suggests that MS galaxies are preferentially extended, while SFGs above the MS are always compact. The median effective radius of SFGs on (above) the MS of Reff=1.5+/-0.2(1.0+/-0.2)kpc remains nearly constant with cosmic time; a parametrization of the form Reff{prop.to}(1+z)^alpha^ yields a shallow slope of only alpha=-0.26+/-0.08(0.12+/-0.14) for SFGs on (above) the MS. The size of the stellar component of galaxies is larger than that inferred from radio continuum emission by a factor ~2(1.3) at z=0.5(2), indicating star formation is enhanced at small radii. The galactic-averaged star formation rate surface density ({SIGMA}_SFR_) scales with the distance to the MS, except for a fraction of MS galaxies (~10%) that harbor starburst-like {SIGMA}_SFR_. These "hidden" starbursts might have experienced a compaction phase due to disk instability and/or merger-driven burst of star formation, which may or may not significantly offset a galaxy from the MS. We thus propose to use {SIGMA}_SFR_ and distance to the MS in conjunction to better identify the galaxy population undergoing a starbursting phase.
- ID:
- ivo://CDS.VizieR/J/ApJ/692/556
- Title:
- Star forming galaxy templates
- Short Name:
- J/ApJ/692/556
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We show that measures of star formation rates (SFRs) for infrared galaxies using either single-band 24um or extinction-corrected Pa{alpha} luminosities are consistent in the total infrared luminosity =L(IR)~10^10^L_{{sun}}_ range. As a part of this work, we constructed spectral energy distribution templates for eleven luminous and ultraluminous purely star forming infrared galaxies and over the spectral range 0.4um to 30cm. We use these templates and the SINGS data to construct average templates from 5um to 30cm for infrared galaxies with L(IR)=5x10^9^ to 10^13^L_{{sun}}_.
- ID:
- ivo://CDS.VizieR/J/AJ/125/1696
- Title:
- Star-forming knots in NGC 3395/3396
- Short Name:
- J/AJ/125/1696
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained ultraviolet and visible wavelength images for the central regions of the interacting galaxies NGC 3395 and NGC 3396, using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The images show many isolated sources of ultraviolet emission produced by young star-forming regions (knots). The FWHM of most of the knots in both galaxies is <=20pc. Far-UV flux distributions for the complete sample of knots can be fitted with a power law with exponent {alpha}=-1.20+/-0.35 for NGC 3395 and a power law with exponent {alpha}=-0.69+/-0.21 for NGC 3396. Comparison with models from Leitherer et al. indicates that the ages of most of the knots are <=80Myr. Reddening of the knots ranges from E(B-V)=0.0 to E(B-V)=0.3mag, indicating variable amounts of dust in these regions. Almost all the knots have masses less than 10^6^M_{sun}_. Many of the knots are probably bound and at least six knots are good proto-globular cluster candidates. There are no significant differences in the fluxes, sizes, and ages of the knots in the two galaxies. The average mass of the knots in NGC 3395 is an order of magnitude less than the average mass of the knots in NGC 3396. There is no obvious correlation between the age of a knot and its position the galaxy.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1360
- Title:
- Star-forming knots in NGC 4194 center
- Short Name:
- J/AJ/127/1360
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report high-resolution ultraviolet and visible-wavelength imaging of the blue compact galaxy NGC 4194 (the Medusa) using the Hubble Space Telescope. A complete sample of 38 UV-bright knots is identified.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A15
- Title:
- Star-forming low-mass gal. stellar host
- Short Name:
- J/A+A/632/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The morphological evolution of star-forming galaxies provides important clues to understand their physical properties, as well as the triggering and quenching mechanisms of star formation. We analyze the morphology of galaxies hosting star-forming events at low redshift (z<0.36). We aim at connecting morphology and star-formation properties of low-mass galaxies (median stellar mass ~10^8.5^M_{sun}_) beyond the local Universe. We use a sample of medium-band selected star-forming galaxies from the GOODS-North field. H images for the sample are created combining both spectral energy distribution fits and HST data. Using them, we mask the star forming regions to obtain an unbiased two-dimensional model of the light distribution of the host galaxies. For this purpose we use PHI, a new Bayesian photometric decomposition code. We applied it independently to 7 HST bands, from the ultraviolet to the near-infrared, assuming a Sersic surface brightness model. Star-forming galaxy hosts show low Sersic index (with median n~0.9), as well as small sizes (median Re~1.6kpc), and negligible change of the parameters with wavelength (except for the axis ratio, which grows with wavelength in 46% of the sample). Using a clustering algorithm, we find two different classes of star-forming galaxies: A more compact, redder, and high-n (class A) and a more extended, bluer and lower-n one (class B). This separation holds across all seven bands analyzed. In addition, we find evidence that the first class is more spheroidal-like (according to the distribution of observed axis ratios). We compute the color gradients of the host galaxies finding that 48% of the objects where the analysis could be performed show negative gradients, and only in 5% they are positive. The host component of low-mass star-forming galaxies at z<0.36 separates into two different classes, similar to what has been found for their higher mass counterparts. The results are consistent with an evolution from class B to class A. Several mechanisms from the literature, like minor and major mergers, and violent disk instability, can explain the physical process behind the likely transition between the classes.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A87
- Title:
- Star forming regions in HST galaxies sample
- Short Name:
- J/A+A/553/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The presence of small- and large-scale star formation structures in a sample of six spiral Hubble Space Telescope (HST) galaxies is investigated to identify small structures of young stars known as OB associations and to tell whether they are formed inside larger scale star forming stellar structures in a hierarchical form. This process was based on a friend-of-friend (FOF) algorithm applied to the bright, early type stars above a certain color cutoff limit in order to ensure that we include main sequence stars. A size criterion was introduced in order to apply the same algorithm to different types of stellar structures. Depending on their size, the structures were divided into the four categories of associations, aggregates, complexes, and supercomplexes. Star forming structures of the four types mentioned above are found in all six galaxies of our sample. The majority of the associations and aggregates (the smaller structures) found are lying inside larger structures like complexes and supercomplexes, indicating a hierarchical star formation mechanism.
- ID:
- ivo://CDS.VizieR/J/AZh/88/342
- Title:
- Star-forming regions in NGC 5585 and IC 1525
- Short Name:
- J/AZh/88/342
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use UBVRI CCD photometry to study star-forming regions (SFRs) in the galaxies NGC 5585 and IC 1525. The observations were acquired with the 1.5-m telescope of the Mt. Maidanak Observatory of the Astronomical Institute of the Uzbek Academy of Sciences (Uzbekistan), with seeing of 0.8"-1.8". We identified 47 SFRs in NGC 5585 and 16 SFRs in IC 1525.
- 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).
