Search

Start Over Capability Type Simple Cone Search
14601. Star formation in spectroscopic survey
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.
14602. Star formation in the blue compact dwarf Mrk 900
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.
14603. Star formation in the Vela Molecular Ridge
ID:
ivo://CDS.VizieR/J/A+A/617/A63
Title:
Star formation in the Vela Molecular Ridge
Short Name:
J/A+A/617/A63
Date:
21 Oct 2021
Publisher:
CDS
Description:
Most stars born in clusters and recent results suggest that star formation (SF) preferentially occurs in subclusters. Studying the morphology and SF history of young clusters is crucial to understanding early SF. We identify the embedded clusters of young stellar objects (YSOs) down to M stars, in the HII regions RCW33, RCW32 and RCW27 of the Vela Molecular Ridge. Our aim is to characterise their properties, such as morphology and extent of the clusters in the three HII regions, derive stellar ages and the connection of the SF history with the environment. Through public photometric surveys such as Gaia, VPHAS, 2MASS and Spitzer/GLIMPSE, we identify YSOs with IR, Halpha and UV excesses, as signature of circumstellar disks and accretion. In addition, we implement a method to distinguish M dwarfs and giants, by comparing the reddening derived in several optical/IR color-color diagrams assuming suitable theoretical models. Since this diagnostic is sensitive to stellar gravity, the procedure allows us to identify pre-main sequence stars. We find a large population of YSOs showing signatures of circumstellar disks with or without accretion. In addition, with the new technique of M-type star selection, we find a rich population of young M stars with a spatial distribution strongly correlated to the more massive population. We find evidence of three young clusters, with different morphology. In addition, we identify field stars falling in the same region, by securely classifying them as giants and foreground MS stars. We identify the embedded population of YSOs, down to about 0.1M_{sun}_, associated with the HII regions RCW33, RCW32 and RCW27 and the clusters Vela T2, Cr197 and Vela T1, respectively, showing very different morphologies. Our results suggest a decreasing SF rate in Vela T2 and triggered SF in Cr197 and Vela T1.
14604. Star formation in W5: Spitzer observations
ID:
ivo://CDS.VizieR/J/ApJ/688/1142
Title:
Star formation in W5: Spitzer observations
Short Name:
J/ApJ/688/1142
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present images and initial results from our extensive Spitzer Space Telescope imaging survey of the W5 HII region with the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS). We detect dense clusters of stars, centered on the O stars HD 18326, BD +60 586, HD 17505, and HD 17520. At 24um, substantial extended emission is visible, presumably from heated dust grains that survive in the strongly ionizing environment of the HII region. With photometry of more than 18000 point sources, we analyze the clustering properties of objects classified as young stars by their IR spectral energy distributions (a total of 2064 sources) across the region using a minimal-spanning-tree algorithm. We find ~40%-70% of infrared excess sources belong to clusters with >=10 members. We find that within the evacuated cavities of the HII regions that make up W5, the ratio of Class II to Class I sources is ~7 times higher than for objects coincident with molecular gas as traced by ^12^CO emission and near-IR extinction maps. We attribute this contrast to an age difference between the two locations and postulate that at least two distinct generations of star formation are visible across W5. Our preliminary analysis shows that triggering is a plausible mechanism to explain the multiple generations of star formation in W5 and merits further investigation.
14605. Star formation quenching stages of galaxies
ID:
ivo://CDS.VizieR/J/A+A/648/A64
Title:
Star formation quenching stages of galaxies
Short Name:
J/A+A/648/A64
Date:
21 Oct 2021
Publisher:
CDS
Description:
The mechanisms that bring galaxies to strongly reduce their star formation activity (star-formation quenching) remain poorly understood. To better study galaxy evolution, we propose a classification based on maps of ionised hydrogen distribution traced by the kiloparsec-resolved, equivalent width of H{alpha} maps, and the nuclear activity of the galaxies using information from the Baldwin-Philips-Terlevich diagnostic diagrams. Using these tools, we group a sample of 238 galaxies from the Calar Alto Legacy Integral Field spectroscopy Area survey in six quenching stages (QSs): (i) objects dominated by recent star formation; (ii) systems that present a quiescent-nuclear-ring structure in their centre; (iii) galaxies that are centrally quiescent; (iv) galaxies with no clear pattern in their ionisation gas distribution (mixed); (v) systems that posses only a few star-forming regions (nearly retired), or (vi) galaxies that are completely quiescent (fully retired). Regarding their nuclear activity, we further divide the galaxies into two groups: active systems that host a weak or strong active galactic nucleus (AGN) at their centre, and non-active objects. Galaxies grouped into quenching-stage classes occupy specific locations on the star-formation-rate versus stellar mass diagram. The 'blue cloud' is populated by the star-forming and the quiescent-nuclear-ring galaxies, the 'green valley' is populated by centrally quiescent and mixed systems, and the 'red sequence' by the nearly- and fully retired objects. Generally, galaxies that host a weak or strong AGN show properties comparable to those of their non-active counterparts at the same QSs, except for the AGN-hosting star-forming systems. The degree of star-formation quenching increases along the present emission-line pattern sequence from star-forming to fully retired. The proposed emission-line classes reinforce the 'inside-out' quenching scenario, which foresees that the suppression of star formation begins from the central regions of the galaxies.
14606. Star formation rate distribution in NGC 1232
ID:
ivo://CDS.VizieR/J/AJ/155/234
Title:
Star formation rate distribution in NGC 1232
Short Name:
J/AJ/155/234
Date:
22 Feb 2022
Publisher:
CDS
Description:
NGC 1232 is a face-on spiral galaxy and a great laboratory for the study of star formation due to its proximity. We obtained high spatial resolution H{alpha} images of this galaxy, with adaptive optics, using the SAM instrument at the SOAR telescope, and used these images to study its H II regions. These observations allowed us to produce the most complete H II region catalog for it to date, with a total of 976 sources. This doubles the number of H II regions previously found for this object. We used these data to construct the H II luminosity function, and obtained a power-law index lower than the typical values found for Sc galaxies. This shallower slope is related to the presence of a significant number of high-luminosity H II regions (log L>39 dex). We also constructed the size distribution function, verifying that, as for most galaxies, NGC 1232 follows an exponential law. We also used the H{alpha} luminosity to calculate the star formation rate. An extremely interesting fact about this galaxy is that X-ray diffuse observations suggest that NGC 1232 recently suffered a collision with a dwarf galaxy. We found an absence of star formation around the region where the X-ray emission is more intense, which we interpret as a star formation quenching due to the collision. Along with that, we found an excess of star-forming regions in the northeast part of the galaxy, where the X-ray emission is less intense.
14607. Star Formation Rate in nearby galaxies
ID:
ivo://CDS.VizieR/J/AJ/146/46
Title:
Star Formation Rate in nearby galaxies
Short Name:
J/AJ/146/46
Date:
21 Oct 2021
Publisher:
CDS
Description:
A distance-limited sample of 869 objects from the Updated Nearby Galaxy Catalog is used to characterize the star formation status of the Local Volume population. We present a compiled list of 1217 star formation rate (SFR) estimates for 802 galaxies within 11Mpc, derived from the H{alpha} imaging surveys and the GALEX far-ultraviolet survey. We briefly discuss some basic scaling relations between SFR and luminosity, morphology, HI mass, surface brightness, and the environment of the galaxies. About 3/4 of our sample consist of dwarf galaxies, for which we offer a more refined classification. We note that the specific SFR of nearly all luminous and dwarf galaxies does not exceed the maximum value: log(SFR/L_K_)=-9.4[yr^-1^]. Most spiral and blue dwarf galaxies have enough time to generate their stellar mass during the cosmological time, T_0_, with the observed SFRs. They dispose of a sufficient amount of gas to support their present SFRs over the next T_0_term. We note that only a small fraction of BCD, Im, and Ir galaxies (about 1/20) proceed in a mode of vigorous starburst activity. In general, the star formation history of spiral and blue dwarf galaxies is mainly driven by their internal processes. The present SFRs of E, S0, and dSph galaxies typically have 1/30-1/300 of their former activity.
14608. Star formation rate in Seyfert galaxies
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.
14609. Star Formation Rate of NFGS galaxies
ID:
ivo://CDS.VizieR/J/AJ/127/2002
Title:
Star Formation Rate of NFGS galaxies
Short Name:
J/AJ/127/2002
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the [O II] emission line as a star formation rate (SFR) indicator using integrated spectra of 97 galaxies from the Nearby Field Galaxies Survey (NFGS). The sample includes all Hubble types and contains SFRs ranging from 0.01 to 100M_{sun}_/yr.
14610. Star formation rate of 4<~z<~8 galaxies
ID:
ivo://CDS.VizieR/J/ApJ/814/95
Title:
Star formation rate of 4<~z<~8 galaxies
Short Name:
J/ApJ/814/95
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent observations have shown that the characteristic luminosity of the rest-frame ultraviolet (UV) luminosity function does not significantly evolve at 4<z<7 and is approximately M_UV_^*^~21. We investigate this apparent non-evolution by examining a sample of 173 bright, M_UV_<-21 galaxies at z=4-7, analyzing their stellar populations and host halo masses. Including deep Spitzer/IRAC imaging to constrain the rest-frame optical light, we find that M_UV_^*^ galaxies at z=4-7 have similar stellar masses of log(M/M_{sun}_)=9.6-9.9 and are thus relatively massive for these high redshifts. However, bright galaxies at z=4-7 are less massive and have younger inferred ages than similarly bright galaxies at z=2-3, even though the two populations have similar star formation rates and levels of dust attenuation for a fixed dust-attenuation curve. Matching the abundances of these bright z=4-7 galaxies to halo mass functions from the Bolshoi {Lambda}CDM simulation implies that the typical halo masses in ~M_UV_^*^ galaxies decrease from log(M_h_/M_{sun}_)=11.9 at z=4 to log(M_h_/M_{sun}_)=11.4 at z=7. Thus, although we are studying galaxies at a similar stellar mass across multiple redshifts, these galaxies live in lower mass halos at higher redshift. The stellar baryon fraction in ~M_UV_^*^ galaxies in units of the cosmic mean {Omega}_b_/{Omega}_m_ rises from 5.1% at z=4 to 11.7% at z=7; this evolution is significant at the ~3{sigma} level. This rise does not agree with simple expectations of how galaxies grow, and implies that some effect, perhaps a diminishing efficiency of feedback, is allowing a higher fraction of available baryons to be converted into stars at high redshifts.

Limit your search

more »

more »

more »

more »

more »

more »