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- ID:
- ivo://CDS.VizieR/J/ApJ/894/57
- Title:
- Star formation activities in MaNGA low-mass galaxies
- Short Name:
- J/ApJ/894/57
- Date:
- 03 Dec 2021 00:39:35
- Publisher:
- CDS
- Description:
- We explore the environmental influences on the star formation (SF) in low-mass galaxies with stellar mass 8<=log(M_*_/M_{sun}_)<=10 at a redshift of 0.01<z<0.07. We identify the neighboring galaxies for our sample using the spectroscopically observed galaxies in the Sloan Digital Sky Survey (SDSS). Our 287 selected pair candidates have a neighboring galaxy with a stellar mass ratio of M_Neighbor_/M_Candidate_<=4 at a projected separation within d_proj_<=1500kpc and a line-of-sight kinematic separation of {Delta}v_LOS_<=300km/s. Our control galaxies are isolated from other galaxies within a projected radius of 1500kpc. All selected galaxies in our sample are spectroscopically observed by the fourth generation of SDSS/Mapping Nearby Galaxies at Apache Point Observatory (SDSS-IV/MaNGA) integral field spectroscopy survey. We radially bin our selected galaxies into three regions with a radial distance of 0<=R/R_e_<=0.5 (inner), 0.5<=R/R_e_<=1.0 (middle), and 1.0<=R/R_e_<=1.5 (outer), in which R_e_ is the effective radius at where the galaxy emit half of its light. We conclude that the SF activities in low-mass galaxies are affected by their environmental conditions when {Delta}v_LOS_<=100km/s at d_proj_<=400kpc. We use stellar-mass-weighted SF rate surface density ({Sigma}SFR/M_*_) to describe the SF strength in each radially binned region. For the pair candidates with 0.25<=M_Neighbor_/M_Candidate_<=4 at d_proj_<=100kpc and {Delta}v_LOS_<=100km/s, we observe an SF enhancement of f_{Delta}SF_=1.75+/-0.96 (f_{Delta}SF_=[({Sigma}SFR/M_*_)_Pair_-({Sigma}SFR/M_*_)_Control,mean_] /({Sigma}SFR/M_*_)_Control,mean_) in their inner regions, which decreases with increasing galactic radii.
- ID:
- ivo://CDS.VizieR/J/ApJ/733/87
- Title:
- Star formation efficiency in galaxies
- Short Name:
- J/ApJ/733/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose an "extended Schmidt law" with explicit dependence of the star formation efficiency (SFE=SFR/M_gas_) on the stellar mass surface density ({Sigma}_star_). This relation has a power-law index of 0.48+/-0.04 and a 1{sigma} observed scatter on the SFE of 0.4 dex, which holds over five orders of magnitude in the stellar density for individual global galaxies, including various types and especially the low-surface-brightness (LSB) galaxies that deviate significantly from the Kennicutt-Schmidt (KS) law. When applying it to regions of a sample of 12 spiral galaxies at sub-kiloparsec resolution, the extended Schmidt law not only holds for LSB regions but also shows significantly smaller scatters both within and across galaxies compared with the KS law. We argue that this new relation points to the role of existing stars in regulating the SFE, thus better encoding the star formation physics. Comparison with physical models of star formation recipes shows that the extended Schmidt law can be reproduced by some models including gas free fall in a stellar-gravitational potential and pressure-supported star formation. By implementing this new law into the analytic model of gas accretion in {Lambda}CDM, we show that it can reproduce the observed main sequence of star-forming galaxies (a relation between the SFR and stellar mass) from z=0 up to z=2.
- ID:
- ivo://CDS.VizieR/J/AJ/136/2782
- Title:
- Star formation efficiency in nearby galaxies
- Short Name:
- J/AJ/136/2782
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the star formation efficiency (SFE), the star formation rate (SFR) per unit of gas, in 23 nearby galaxies and compare it with expectations from proposed star formation laws and thresholds. We use HI maps from The HI Nearby Galaxy Survey (THINGS) and derive H_2_ maps of CO measured by HERA CO-Line Extragalactic Survey and Berkeley-Illinois-Maryland Association Survey of Nearby Galaxies. We estimate the SFR by combining Galaxy Evolution Explorer (GALEX) far-ultraviolet maps and the Spitzer Infrared Nearby Galaxies Survey (SINGS) 24um maps, infer stellar surface density profiles from SINGS 3.6um data, and use kinematics from THINGS.
- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/150/43
- Title:
- Star formation in active and normal galaxies
- Short Name:
- J/AJ/150/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated the properties of the host galaxies of active galactic nuclei (AGNs). We used radio emission around the nuclei of the host galaxies to represent AGN activity and used infrared (IR) emission to represent the star-forming activity and stellar population of the host galaxies. We determined that active galaxies have higher stellar masses (SMs) within the central kiloparsec radius than normal galaxies do independent of the Hubble types of the host galaxies; but both active and normal galaxies exhibit similar specific star formation rates (SSFRs), ranging between 10^-10.5^ and 10^-9.5^/yr. We find that the central SM surface density might be used as an indicator to identify AGNs. We also discovered that certain AGNs exhibit substantial inner stellar structures in the IR images; most of the AGNs with inner structures are Seyferts, whereas only a few LINERs exhibit inner structures. We note that the AGNs with inner structures show a positive correlation between the radio activity of the AGNs and the SFRs of the host galaxies, but the sources without inner structures show a negative correlation between the radio power and the SFRs. These results might be explained with a scenario of starburst-AGN evolution. In this scenario, AGN activities are triggered following a nuclear starburst; during the evolution, AGN activities are accompanied by SF activity in the inner regions of the host galaxies; at the final stage of the evolution, the AGNs might transform into LINERs, exhibiting weak SF activity in the central regions of the host galaxies.
- 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.
- 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.
