- ID:
- ivo://CDS.VizieR/J/AJ/138/1037
- Title:
- Star formation in Centaurus A Group dwarfs
- Short Name:
- J/AJ/138/1037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present H{alpha} narrow-band imaging of 17 dwarf irregular (dI) galaxies in the nearby Centaurus A Group. Although all large galaxies of the group are or recently have been through a period of enhanced star formation, the dIs have normal star formation rates (SFRs) and do not contain a larger fraction of dwarf starbursts than other nearby groups such as the Sculptor Group or the Local Group. Most of the galaxies in the group now have fairly accurately known distances, which enables us to obtain relative distances between dIs and larger galaxies of the group. We find four transition dwarfs in the Group, dwarfs that show characteristics of both dE/dSphs and dIs, and which contain cold gas but no current star formation.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/285/404
- Title:
- Star formation in compact groups of galaxies
- Short Name:
- J/A+A/285/404
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/AJ/105/894
- Title:
- Star formation in DDO 210 and NGC 3109
- Short Name:
- J/AJ/105/894
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The method proposed in Paper I [Tosi et al., AJ, 102, 951 (1991)] to study the star formation histories in nearby irregulars is here applied to the galaxies DDO 210 and NGC 3109. To this purpose we have obtained deep CCD photometry of two regions in DDO 210 and three regions in NGC 3109, reaching V = 24 with the required accuracy of Sigma(V) <= 0.1 mag. Major information on the stellar populations, star formation rates, and initial mass functions of these regions in the last 1 Gyr are derived from the comparison of the observational color-magnitude diagrams and luminosity functions, with the corresponding synthetic diagrams and luminosity functions generated by a numerical simulation code based on stellar evolutionary tracks. In general, for both galaxies we find that in the last 1 Gyr the star formation activity has been rather continuous, possibly occurring in long episodes of moderate activity separated by short quiescent periods. According to our models the metallicity should be fairly low (in the range 0.05 <= Z/Zsun <= 0.5) and the initial mass function exponent in the vicinity of Salpeter's value, i.e., slightly flatter than in the solar neighborhood. The studied regions of NGC 3109 appear to contain different stellar populations (i.e., with slightly different metallicity and star formation histories), whereas those of DDO 210 seem to have fairly similar stellar contents, although for this galaxy the interpretation is more uncertain. As a by-product of our method we find that the distance modulus to DDO 210 should be (m-M)0 approx. 28, which places this galaxy beyond the edge of the Local Group.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/251
- Title:
- Star Formation in Early-type galaxies
- Short Name:
- J/A+AS/130/251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper is the first of a series (Longhetti et al., 1998A&AS..130..267L, 1998b (Paper III) in press) dedicated to the study of the star formation history in early-type galaxies which show fine structures and/or interaction signatures. It presents nuclear line-strength indices for a sample composed of 21 shell galaxies, from the Malin & Carter (1983ApJ...274..534M) southern survey, and 30 members of isolated interacting pairs, from the Reduzzi & Rampazzo (1995ApL....30....1R) catalogue, located in low density environments. The spectral range covers 3700{AA}<{lambda}<5700{AA} at 2.1{AA}FWHM resolution. We measure 16 red ({lambda}>4200{AA}) indices defined by the Lick Group. Measures have been transformed into the Lick-IDS ``standard'' system. The procedure has been tested on a set of 5 elliptical galaxies selected from the Gonzalez (1993, Ph.D. thesis) sample. We derive also three blue ({lambda}<4200) indices, namely {DELTA}(4000{AA}) defined by Hamilton (1985ApJ...297..371H), H+K(CaII) and Hdelta/FeI defined by Rose (1984AJ.....89.1238R, 1985AJ.....90.1927R). Blue indices are correlated to the age of the last starburst occurred in a galaxy (Leonardi & Rose, 1996AJ....111..182L). The indices determination, the estimate of the measurement errors and the correction for the galaxies velocity dispersions are discussed in detail. In the Appendix A we present the indices for a set of hot stars (T>10000K) which may be used for extending, toward high temperatures, Worthey (1992, Ph.D. Thesis) fitting functions.
- ID:
- ivo://CDS.VizieR/J/A+A/345/419
- Title:
- Star formation in early-type galaxies
- Short Name:
- J/A+A/345/419
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the star formation properties of a sample of 21 shell galaxies and 30 early-type galaxies members of interacting pairs, located in low density environments (Longhetti et al., 1998, Cat. <J/A+AS/130/251>, 1998A&AS..130..267L). The study is based on new models developed to interpret the information coming from `blue' H{delta}FeI, H+K(CaII) and D4000 line-strength indices proposed by Rose (1984AJ.....89.1238R; 1985AJ.....90.1927R) and Hamilton (1985ApJ...297..371H). We find that the last star forming event that occurred in the nuclear region of shell galaxies is statistically old (from 0.1 up to several Gyr) with respect to the corresponding one in the sub-sample of pair galaxies (<0.1Gyr or even ongoing star formation). If the stellar activity is somehow related to the formation of shells, as predicted by several dynamical models of galaxy interaction, shells have to be considered long lasting structures. Since pair members show evidence of very recent star formation, we suggest that either large reservoirs of gas have to be present to maintain active star formation, if these galaxies are on periodic orbits, or most of the pair members in the present sample are experiencing unbound encounters.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/841
- Title:
- Star formation in E/S0 galaxies
- Short Name:
- J/ApJ/708/841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent work has identified a population of low-redshift E/S0 galaxies that lie on the blue sequence in color versus stellar mass parameter space, where spiral galaxies typically reside. While high-mass blue-sequence E/S0s often resemble young merger or interaction remnants likely to fade to the red sequence, we focus on blue-sequence E/S0s with lower stellar masses (M_*_<a fewx10^10^M_{sun}_), which are characterized by fairly regular morphologies and low-density field environments where fresh gas infall is possible. This population may provide an evolutionary link between early-type galaxies and spirals through disk regrowth. Focusing on atomic gas reservoirs, we present new GBT HI data for 27 E/S0s on both sequences as well as a complete tabulation of archival HI data for other galaxies in the Nearby Field Galaxy Survey. Normalized to stellar mass, the atomic gas masses for 12 of the 14 blue-sequence E/S0s range from 0.1 to >1.0, demonstrating that morphological transformation is possible if the detected gas can be converted into stars. These gas-to-stellar mass ratios are comparable to those of spiral and irregular galaxies and have a similar dependence on stellar mass.
20487. Star formation in galaxies
- ID:
- ivo://CDS.VizieR/J/A+A/288/713
- Title:
- Star formation in galaxies
- Short Name:
- J/A+A/288/713
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Evolutionary models of disk galaxies are presented (table3), and are confronted with a sample of late type galaxies from the Tully (Nearby Galaxies, see Cat. <VII/145>) and the de Vaucouleurs (RC3, see Cat. <VII/155>) catalogues.
- 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/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.
- 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.