- ID:
- ivo://CDS.VizieR/J/other/AstBu/68.243
- Title:
- Star formation in isolated galaxies
- Short Name:
- J/other/AstBu/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the FUV fluxes measured with the GALEX to study the star formation properties of galaxies collected in the Local Orphan Galaxies catalog (LOG, 2011AstBu..66....1K). Among 517 LOG galaxies having radial velocities V_LG_<3500km/s and Galactic latitudes |b|>15{deg}, 428 objects have been detected in FUV. We briefly discuss some scaling relations between the specific star formation rate (SSFR) and stellar mass, HI-mass, morphology, and surface brightness of galaxies situated in extremely low density regions of the Local Supercluster. Our sample is populated with predominantly late-type, gas-rich objects with the median morphological type of Sdm. Only 5% of LOG galaxies are classified as early types: E, S0, S0/a, however, they systematically differ from normal E and S0 galaxies by lower luminosity and presence of gas and dust. We find that almost all galaxies in our sample have their SSFR below 0.4Gyr^-1^. This limit is also true even for a sample of 260 active star-burst Markarian galaxies situated in the same volume. The existence of such a quasi-Eddington limit for galaxies seems to be a key factor which characterizes the transformation of gas into stars at the current epoch.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/588/A29
- Title:
- Star formation in massive clumps in Milky Way
- Short Name:
- J/A+A/588/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Newborn stars form within the localized, high density regions of molecular clouds. The sequence and rate at which stars form in dense clumps and the dependence on local and global environments are key factors in developing descriptions of stellar production in galaxies. We seek to observationally constrain the rate and latency of star formation in dense massive clumps that are distributed throughout the Galaxy and to compare these results to proposed prescriptions for stellar production. A sample of 24 micron based Class I protostars are linked to dust clumps that are embedded within molecular clouds selected from the APEX Telescope Large Area Survey of the Galaxy. We determine the fraction of star-forming clumps that imposes a constraint on the latency of star formation in units of a clump's lifetime. Protostellar masses are estimated from models of circumstellar environments of young stellar objects from which star formation rates are derived. Physical properties of the clumps are calculated from 870 micron dust continuum emission and NH_3_ line emission. Linear correlations are identified between the star formation rate surface density, Sigma_SFR and the quantities Sigma_H2/tau_ff and Sigma_H2/tau_cross, suggesting that star formation is regulated at the local scales of molecular clouds. The measured fraction of star forming clumps is 23%. Accounting for star formation within clumps that are excluded from our sample due to 24 micron saturation, this fraction can be as high as 31%, which is similar to previous results. Dense, massive clumps form primarily low mass (<1-2M_{sun}_) stars with emergent 24 micron fluxes below our sensitivity limit or are incapable of forming any stars for the initial 70% of their lifetimes. The low fraction of star forming clumps in the Galactic center relative to those located in the disk of the Milky Way is verified.
- ID:
- ivo://CDS.VizieR/J/MNRAS/482/560
- Title:
- Star formation in nearby galaxies
- Short Name:
- J/MNRAS/482/560
- Date:
- 18 Jan 2022 13:35:08
- Publisher:
- CDS
- Description:
- We present multiwavelength global star formation rate (SFR) estimates for 326 galaxies from the Star Formation Reference Survey in order to determine the mutual scatter and range of validity of different indicators. The widely used empirical SFR recipes based on 1.4GHz continuum, 8.0um polycyclic aromatic hydrocarbons (PAHs), and a combination of far-infrared (FIR) plus ultraviolet (UV) emission are mutually consistent with scatter of <~0.3dex. The scatter is even smaller, <~0.24dex, in the intermediate luminosity range 9.3<log(L_60um_/L_{sun}_)<10.7. The data prefer a non-linear relation between 1.4GHz luminosity and other SFR measures. PAH luminosity underestimates SFR for galaxies with strong UV emission. A bolometric extinction correction to far-UV luminosity yields SFR within 0.2dex of the total SFR estimate, but extinction corrections based on UV spectral slope or nuclear Balmer decrement give SFRs that may differ from the total SFR by up to 2dex. However, for the minority of galaxies with UV luminosity >5x10^9^L_{sun}_ or with implied far-UV extinction <1mag, the UV spectral slope gives extinction corrections with 0.22dex uncertainty.
- 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/ApJ/683/822
- Title:
- Star formation in Ophiuchus and Perseus II.
- Short Name:
- J/ApJ/683/822
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a census of the population of deeply embedded young stellar objects (YSOs) in the Ophiuchus molecular cloud complex based on a combination of Spitzer Space Telescope mid-infrared data from the "Cores to Disks" (c2d) legacy team and JCMT/SCUBA submillimeter maps from the COMPLETE team. We have applied a method developed for identifying embedded protostars in Perseus to these data sets and in this way construct a relatively unbiased sample of 27 candidate embedded protostars with envelopes more massive than our sensitivity limit (about 0.1M_{sun}_).
- ID:
- ivo://CDS.VizieR/J/A+A/468/1009
- Title:
- Star formation in Perseus. II.
- Short Name:
- J/A+A/468/1009
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hatchell et al. (2005, Cat. <J/A+A/440/151>, Paper I) published a submillimetre continuum map of the Perseus molecular cloud, detecting the starless and protostellar cores within it. The aim is to determine the evolutionary stage of each submm core in Perseus, and investigate the lifetimes of these phases.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/97
- Title:
- Star Formation in Radio Survey (SFRS): 33GHz obs.
- Short Name:
- J/ApJ/761/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 33GHz photometry of 103 galaxy nuclei and extranuclear star-forming complexes taken with the Green Bank Telescope (GBT) as part of the Star Formation in Radio Survey (SFRS). Among the sources without evidence for an active galactic nucleus, and also having lower frequency radio data, we find a median thermal fraction at 33GHz of {approx}76% with a dispersion of {approx}24%. For all sources resolved on scales <~0.5kpc, the thermal fraction is even larger, being >~90%. This suggests that the rest-frame 33GHz emission provides a sensitive measure of the ionizing photon rate from young star-forming regions, thus making it a robust star formation rate (SFR) indicator. Taking the 33 GHz SFRs as a reference, we investigate other empirical calibrations relying on different combinations of warm 24{mu}m dust, total infrared (IR; 8-1000{mu}m), H{alpha} line, and far-UV continuum emission. The recipes derived here generally agree with others found in the literature, albeit with a large dispersion that most likely stems from a combination of effects. Comparing the 33GHz to total IR flux ratios as a function of the radio spectral index, measured between 1.7 and 33GHz, we find that the ratio increases as the radio spectral index flattens which does not appear to be a distance effect. Consequently, the ratio of non-thermal to total IR emission appears relatively constant, suggesting only moderate variations in the cosmic-ray electron injection spectrum and ratio of synchrotron to total cooling processes among star-forming complexes. Assuming that this trend solely arises from an increase in the thermal fraction sets a maximum on the scatter of the non-thermal spectral indices among the star-forming regions of {sigma}_{alpha}_NT<~0.13.
- ID:
- ivo://CDS.VizieR/J/ApJ/559/606
- Title:
- Star formation in spectroscopic survey
- Short Name:
- J/ApJ/559/606
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 15R-North galaxy redshift survey is a uniform spectroscopic survey (S/N~10) covering the range 3650-7400{AA} for 3149 galaxies with median redshift 0.05. The sample is 90% complete to R=15.4. The median slit covering fraction is 24% of the galaxy, apparently sufficient to minimize the effects of aperture bias on the EW(H{alpha}). Forty-nine percent of the galaxies in the survey have one or more emission lines detected at >=2{sigma}. In agreement with previous surveys, the fraction of absorption-line galaxies increases steeply with galaxy luminosity. We use H{beta}, [O III], H{alpha}, and [N II] to discriminate between star-forming galaxies and AGNs. At least 20% of the galaxies are star-forming, at least 17% have AGN-like emission, and 12% have unclassifiable emission. The data for the entire survey will appear in Geller et al. 2002, in preparation.
- ID:
- ivo://CDS.VizieR/J/ApJ/619/L95
- Title:
- Star formation in Stephan's Quintet
- Short Name:
- J/ApJ/619/L95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first Galaxy Evolution Explorer (GALEX) UV images of the well-known interacting group of galaxies, Stephan's Quintet (SQ). We detect widespread UV emission throughout the group. However, there is no consistent coincidence between UV structure and emission in the optical, H{alpha}, or HI. Excluding the foreground galaxy NGC 7320 (Sd), most of the UV emission is found in regions associated with the two spiral members of the group, NGC 7319 and NGC 7318b, and the intragroup medium starburst SQ-A. The extinction-corrected UV data are analyzed to investigate the overall star formation activity in SQ.
- ID:
- ivo://CDS.VizieR/J/A+A/634/A95
- Title:
- Star formation in the blue compact dwarf Mrk 900
- Short Name:
- J/A+A/634/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-luminosity, active star-forming blue compact galaxies (BCGs) are excellent laboratories for investigating the process of star formation on galactic scales and probing the interplay between massive stars and the surrounding interstellar (or intergalactic) medium. We investigated the morphology, structure, and stellar content of the Blue Compact Galaxy Mrk 900, combining optical integral field observations obtained with VIMOS at the VLT and deep broad-band photometry taken at the 2.5 m NOT telescope. From the integral field data, we built continuum, emission, and diagnostic line ratio maps and produced velocity and velocity dispersion maps. We also generated the integrated spectrum of the major HII regions and the nuclear area to determine reliable physical parameters and oxygen abundances. The broad-band data, tracing the galaxy up to radius 4 kpc, allowed us to investigate the properties of the low surface brightness underlying stellar host. We disentangle two different stellar components in Mrk 900: a young population, which resolves into individual stellar clusters with ages ~5.5-6.6Myr and extends about 1 kpc along the galaxy minor axis, is placed on top of a rather red and regular shaped underlying stellar host, several Gyr old. We find evidence of a substantial amount of dust and an inhomogeneous extinction pattern, with a dust lane crossing the central starburst. Mrk 900 displays overall rotation, although distorted in the central, starburst regions; the dispersion velocity map is highly inhomogeneous, with values increasing up to 60km/s at the periphery of the SF regions, where we also find hints of the presence of shocks. Our observational results point to an interaction or merger with a low-mass object or infalling gas as plausible trigger mechanisms for the present starburst event.