- ID:
- ivo://CDS.VizieR/J/ApJ/789/147
- Title:
- Star formation histories of LG dwarf galaxies
- Short Name:
- J/ApJ/789/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present uniformly measured star formation histories (SFHs) of 40 Local Group (LG) dwarf galaxies based on color-magnitude diagram (CMD) analysis from archival Hubble Space Telescope imaging. We demonstrate that accurate SFHs can be recovered from CMDs that do not reach the oldest main sequence turn-off (MSTO), but emphasize that the oldest MSTO is critical for precisely constraining the earliest epochs of star formation. We find that: (1) the average lifetime SFHs of dwarf spheroidals (dSphs) can be approximated by an exponentially declining SFH with {tau} ~ 5 Gyr; (2) lower luminosity dSphs are less likely to have extended SFHs than more luminous dSphs; (3) the average SFHs of dwarf irregulars (dIrrs), transition dwarfs, and dwarf ellipticals can be approximated by the combination of an exponentially declining SFH ({tau} ~ 3-4 Gyr) for lookback ages >10-12 Gyr ago and a constant SFH thereafter; (4) the observed fraction of stellar mass formed prior to z = 2 ranges considerably (80% for galaxies with M < 10^5^ M_{sun}_ to 30% for galaxies with M > 10^7^ M_{sun}_) and is largely explained by environment; (5) the distinction between "ultra-faint" and "classical" dSphs is arbitrary; (6) LG dIrrs formed a significantly higher fraction of stellar mass prior to z = 2 than the Sloan Digital Sky Survey galaxies from Leitner and the SFHs from the abundance matching models of Behroozi et al. This may indicate higher than expected star formation efficiencies at early times in low mass galaxies. Finally, we provide all the SFHs in tabulated electronic format for use by the community.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/127/1531
- Title:
- Star formation history of SMC
- Short Name:
- J/AJ/127/1531
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spatially resolved star formation and chemical enrichment history of the Small Magellanic Cloud (SMC) across the entire central 4{deg}x4.5{deg} area of the main body, based on UBVI photometry from our Magellanic Clouds Photometric Survey.
- 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/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/661/L143
- Title:
- Star formation rate in Seyfert galaxies
- Short Name:
- J/ApJ/661/L143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Feedback from black hole activity is widely believed to play a key role in regulating star formation and black hole growth. A long-standing issue is the relation between star formation and the fueling of the supermassive black holes in active galactic nuclei (AGNs). We compile a sample of 57 Seyfert galaxies to tackle this issue. We estimate the surface densities of gas and star formation rates in circumnuclear regions (CNRs). Comparing them with the well-known Kennicutt-Schmidt (K-S) law, we find that the star formation rates (SFRs) in the CNRs of most Seyfert galaxies are suppressed in this sample. Feedback is suggested to explain the suppressed SFRs.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A31
- Title:
- Statistical test on binary stars non-coevality
- Short Name:
- J/A+A/587/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a statistical test on the expected difference in age estimates of two coeval stars in detached double-lined eclipsing binary systems that are only caused by observational uncertainties. We focus on stars in the mass range [0.8; 1.6] Msun, with an initial metallicity [Fe/H] from -0.55 to 0.55dex, and on stars in the main-sequence phase. The ages were obtained by means of the SCEPtER technique, a maximum-likelihood procedure relying on a pre-computed grid of stellar models. The observational constraints used in the recovery procedure are stellar mass, radius, effective temperature, and metallicity [Fe/H]. To check the effect of the uncertainties affecting observations on the (non-)coevality assessment, the chosen observational constraints were subjected to a Gaussian perturbation before applying the SCEPtER code. We defined the statistic W computed as the ratio of the absolute difference of estimated ages for the two stars over the age of the older one. We determined the critical values of this statistics above which coevality can be rejected in dependence on the mass of the two stars, on the initial metallicity [Fe/H], and on the evolutionary stage of the primary star. The median expected difference in the reconstructed age between the coeval stars of a binary system - caused alone by the observational uncertainties - shows a strong dependence on the evolutionary stage. This ranges from about 20% for an evolved primary star to about 75% for a near ZAMS primary. The median difference also shows an increase with the mass of the primary star from 20% for 0.8M_{sun}_ stars to about 50% for 1.6M_{sun}_ stars. The reliability of these results was checked by repeating the process with a grid of stellar models computed by a different evolutionary code; the median difference in the critical values was only 0.01. We show that the W test is much more sensible to age differences in the binary system components than the alternative approach of comparing the confidence interval of the age of the two stars. We also found that the distribution of W is, for almost all the examined cases, well approximated by beta distributions. The proposed method improves upon the techniques that are commonly adopted for judging the coevality of an observed system. It also provides a result founded on reliable statistics that simultaneously accounts for all the observational uncertainties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/310/210
- Title:
- Stellar composition of CMa R1
- Short Name:
- J/MNRAS/310/210
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This directory contains movies in mpeg format which show models for the time evolution of the Hertzsprung-Russell diagram of a very young open cluster between 0 and 30Myr. Four different star formation scenario's are considered, (a) instantaneous star formation, (b) constant rate of star formation with time, (c) increasing rate of star formation, and (d) decreasing rate of star formation. For the latter three scenario's, models for a duration of the star formation episode {delta}t of 0.1, 1.0 and 10Myr are computed.
- ID:
- ivo://CDS.VizieR/J/ApJ/764/21
- Title:
- Stellar evolutionary models with 13-120Msun
- Short Name:
- J/ApJ/764/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first set of a new generation of models of massive stars with a solar composition extending between 13 and 120M_{sun}_, computed with and without the effects of rotation. We included two instabilities induced by rotation: the meridional circulation and the shear instability. We implemented two alternative schemes to treat the transport of the angular momentum: the advection-diffusion formalism and the simpler purely diffusive one. The full evolution from the pre-main sequence up to the pre-supernova stage is followed in detail with a very extended nuclear network. The explosive yields are provided for a variety of possible mass cuts and are available at the Web site http://www.iasf-roma.inaf.it/orfeo/public_html. We find that both the He and the CO core masses are larger than those of their non-rotating counterparts. Also the C abundance left by the He burning is lower than in the non-rotating case, especially for stars with an initial mass of 13-25M_{sun}_, and this affects the final mass-radius relation, basically the final binding energy, at the pre-supernova stage. The elemental yields produced by a generation of stars rotating initially at 300km/s do not change substantially with respect to those produced by a generation of non-rotating massive stars, the main differences being a slight overproduction of the weak s-component and a larger production of F. Since rotation also affects the mass-loss rate, either directly or indirectly, we find substantial differences in the lifetimes as O-type and Wolf-Rayet subtypes between the rotating and non-rotating models. The maximum mass exploding as Type IIP supernova ranges between 15 and 20M _{sun}_ in both sets of models (this value depends basically on the larger mass-loss rates in the red supergiant phase due to the inclusion of the dust-driven wind). This limiting value is in remarkably good agreement with current estimates.
- ID:
- ivo://CDS.VizieR/J/A+A/299/755
- Title:
- Stellar evolution. II. Post-AGB
- Short Name:
- J/A+A/299/755
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a set of evolutionary tracks for central stars of planetary nebulae in the range from 0.53 to 0.94M_{sun}_. These models are based on extensive stellar evolution calculations for initial masses between 1 and 7M_{sun}_ which have been carried out all the way from the main sequence through the AGB towards the stage of white dwarfs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/298/525
- Title:
- Stellar evolution models for Z = 0.0001 to 0.03
- Short Name:
- J/MNRAS/298/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have calculated a grid of empirically well tested evolutionary tracks with masses M between 0.5 and 50M_{sun}_, spaced by approximately 0.1 in log M, and with metallicities Z=0.0001, 0.0003, 0.001, 0.004, 0.01, 0.02 and 0.03. We use a robust and fast evolution code with a self-adaptive non-Lagrangian mesh, which employs the mixing-length theory but treats convective mixing as a diffusion process, solving simultaneously for the structure and the chemical composition. The hydrogen and helium abundances are chosen as functions of the metallicity: X=0.76-3.0Z and Y=0.24+2.0Z. Two sets of models were computed, one without and one with a certain amount of enhanced mixing or 'overshooting'.
