- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/601/A95
- Title:
- Star-forming dwarfs at intermediate-z in VUDS
- Short Name:
- J/A+A/601/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present emission line measurements and the main physical properties of a sample of 164 star-forming dwarf galaxies (SFDGs) in the VIMOS Ultra Deep Survey (VUDS, Le Fevre et al., 2015A&A...576A..79L). VUDS is one of the largest programs on the ESO-VLT with 640 hours of observing time, and covers a total of one square degree in three separate fields: COSMOS, ECDFS, and VVDS-02h. The spectroscopic observations were carried out at the VLT with the VIMOS Multi-Object Spectrograph (MOS) with two grisms (LRBLUE and LRRED) covering a wavelength range of 365<lambda<935nm at uniform spectral resolution of R=180 and R=210, respectively. The integration time (on-source) is ~14-hours per target for each grism, which allows to detect the continuum at 850nm for i_AB_=25, and emission lines with an observed flux limit F=1.5*10^-18^erg/s/cm2 at S/N~5. Redshift measurements in VUDS were performed using the EZ code (Garilli et al., 2010PASP..122..827G), both in automatic and manual modes (by two persons independently) for each spectrum. The overall redshift accuracy is dz/(1+z)=0.0005-0.0007. The spectra had already been fully calibrated in wavelength and flux by the VUDS team, which also did the sky subtraction. Emission lines fluxes and equivalent widths are measured manually on a one-by- one basis using the task 'splot' of IRAF by direct integration of the line profile after linear subtraction of the continuum. These fluxes are given in units of 10^-18^erg/s/cm^2^. The uncertainties in the line measurements were computed from the dispersion of values provided by multiple measurements adopting different possible band-passes (free of lines and strong residuals from sky subtraction) for the local continuum determination, which is fitted using a second order polynomial. No extinction correction has been applied to these fluxes. The EW measurements of H{gamma}, H{beta} and H{alpha} lines have been already corrected for absorption by +0.1nm for all galaxies, following Ly et al. (2014ApJ...780..122L). For each galaxy the reddening constant, c(H{beta}), is presented. These values and their uncertainties have been derived from the H{alpha}/H{beta} or H{gamma}/H{beta} ratios, whenever possible. We adopted the reddening constant from the best-fit SED, using the relations of Calzetti et al. (2000ApJ...533..682C), for (a) galaxies where the computation of c(H{beta}) from emission lines is not possible because the lines are not present, or (b) the line ratios give a negative extinction correction (i.e., H{alpha}/H{beta}<2.82 or H{gamma}/H{beta}<0.47, assuming Case B recombination with Te=2*10^4^K, ne=100cm^-3^).
- ID:
- ivo://CDS.VizieR/J/ApJ/773/86
- Title:
- Star-forming galaxies in ACO 2029
- Short Name:
- J/ApJ/773/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dense environments are known to quench star formation in galaxies, but it is still unknown what mechanism(s) are directly responsible. In this paper, we study the star formation of galaxies in A2029 and compare it to that of Coma, combining indicators at 24{mu}m, H{alpha}, and UV down to rates of 0.03M_{sun}_/yr. We show that A2029's star-forming galaxies follow the same mass-SFR relation as the field. The Coma cluster, on the other hand, has a population of galaxies with star formation rates (SFRs) significantly lower than the field mass-SFR relation, indicative of galaxies in the process of being quenched. Over half of these galaxies also host active galactic nuclei. Ram-pressure stripping and starvation/strangulation are the most likely mechanisms for suppressing the star formation in these galaxies, but we are unable to disentangle which is dominating. The differences we see between the two clusters' populations of star-forming galaxies may be related to their accretion histories, with A2029 having accreted its star-forming galaxies more recently than Coma. Additionally, many early-type galaxies in A2029 are detected at 24{mu}m and/or in the far-UV, but this emission is not directly related to star formation. Similar galaxies have probably been classified as star forming in previous studies of dense clusters, possibly obscuring some of the effects of the cluster environment on true star-forming galaxies.
- 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.
- 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.