STAR FORMATION IN THE CENTRAL REGIONS OF ACTIVE AND NORMAL GALAXIES

2015 ◽  
Vol 150 (2) ◽  
pp. 43 ◽  
Author(s):  
Mengchun Tsai ◽  
Chorng-Yuan Hwang
Keyword(s):  
Star Formation ◽  
Normal Galaxies ◽  
Central Regions

scholarly journals Centers of Star Formation in the Nuclei of Galaxies

1980 ◽  
Vol 5 ◽  
pp. 223-225
Author(s):  
V. I. Pronik
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Stellar Population ◽  
Central Star ◽  
Density Maximum ◽  
Origin And Evolution ◽  
Normal Galaxies ◽  
Central Regions ◽  
Nuclear Regions ◽  
Stellar Density

Nuclei of galaxies are the phenomena intimately connected with the structure of galaxies, their origin and evolution. Spectral and photometrical characteristics and therefore the stellar population of the most nuclei of normal galaxies are like that of central regions or bulges (Walker, 1962, 1964; Vorontsov-Velyaminov, 1965, 1968). Processes of star formation in the nuclei must be considered together with the problem of formation of the central regions (bulges) or even of all galaxies as a whole.The term “galactic nucleus” is usually applied to the central region (or center of symmetry) having the maximum stellar density (maximum surface brightness) and dimensions less than 100 pc (dimension of a globular cluster). The observational evidence of star formation at the present epoch is related to the nuclear regions within radii of 100-1000 pc or more. Information about the physical condition of the gas and about star formation just in the center of galaxies (≤ 1 pc) can be obtained only by theory. The red colour of the central star cluster of normal galaxies is evidence that star formation in this region is practically finished.

scholarly journals Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Monique C. Aller ◽  
Varsha P. Kulkarni ◽  
Donald G. York ◽  
Daniel E. Welty ◽  
Giovanni Vladilo ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Absorption Feature ◽  
Dust Grains ◽  
Interstellar Gas ◽  
Chemical Enrichment ◽  
Normal Galaxies ◽  
History Of ◽  
Dust Grain ◽  
Grain Properties

AbstractGas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of the strengths of the 10 and 18 μm silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between silicate dust abundance, reddening, and gas metallicity, which will yield valuable insights into the history of star formation and chemical enrichment in galaxies.

scholarly journals SDSS J114818.18-013823.7: Forming Compact Dwarf Galaxy through the Dwarf-Dwarf Merger

2021 ◽  
Vol 7 (2) ◽  
pp. 49-57
Author(s):  
D. N. Chhatkuli ◽  
S. Paudel ◽  
A. K. Gautam ◽  
B. Aryal
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Absolute Magnitude ◽  
Spectroscopic Properties ◽  
Normal Galaxies ◽  
Star Formation Activity ◽  
The Galaxy

We studied the spectroscopic properties of the low redshift (z = 0.0130) interacting dwarf galaxy SDSS J114818.18-013823.7. It is a compact galaxy of half-light radius 521 parsec. It’s r-band absolute magnitude is -16.71 mag. Using a publicly available optical spectrum from the Sloan Sky Survey data archive, we calculated star-formation rate, emission line metallicity, and dust extinction of the galaxy. Star formation rate (SFR) due to Hα is found to be 0.118 Mʘ year-1 after extinction correction. The emission-line metallicity, 12+log(O/H), is 8.13 dex. Placing these values in the scaling relation of normal galaxies, we find that SDSS J114818.18-013823.7 is a significant outlier from both size-magnitude relation and SFR-B-band absolute relation. Although SDSS J114818.18-013823.7 possess enhance rate of star-formation, the current star-formation activity can persist several Giga years in the future at the current place and it remains compact.

scholarly journals Gas-rich LSB Galaxies – Progenitors of Blue Compact Dwarfs?

1999 ◽  
Vol 171 ◽  
pp. 253-260 ◽  
Author(s):  
John J. Salzer ◽  
Stuart A. Norton
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Mass Density ◽  
Central Mass ◽  
Galaxy Distribution ◽  
Low Surface Brightness ◽  
Central Regions ◽  
Lsb Galaxies

AbstractWe analyze deep CCD images of nearby Blue Compact Dwarf (BCD) galaxies in an attempt to understand the nature of the progenitors which are hosting the current burst of star formation. In particular, we ask whether BCDs are hosted by normal or low-surface-brightness dI galaxies. We conclude that BCDs are in fact hosted by gas-rich galaxies which populate the extreme high-central-mass-density end of the dwarf galaxy distribution. Such galaxies are predisposed to having numerous strong bursts of star formation in their central regions. In this picture, BCDs can only occur in the minority of dwarf galaxies, rather than being a common phase experienced by all gas-rich dwarfs.

scholarly journals High supernova rate and enhanced star-formation triggered in M81-M82 encounter

2006 ◽  
Vol 2 (S237) ◽  
pp. 391-391
Author(s):  
B. Arbutina ◽  
D. Urošević ◽  
B. Vukotić
Keyword(s):  
Star Formation ◽  
Supernova Remnant ◽  
Close Encounter ◽  
Nearby Galaxy ◽  
Radio Observations ◽  
General Belief ◽  
Normal Galaxies

It is a general belief that the starburst activity of a nearby galaxy M82 was triggered in a close encounter with its massive companion M81, a few tens of million years ago. Despite the lack of supernovae observed, multiwavelength radio observations of M82 discovered a considerable number of compact supernova remnant candidates. We use these remnants to estimate the supernova rate (SNR) and the enhanced star-formation (SFR) rate in M82, and compare them with rates in normal galaxies.

scholarly journals Galaxy populations in the most distant SPT-SZ clusters

2019 ◽  
Vol 622 ◽  
pp. A117 ◽  
Author(s):  
V. Strazzullo ◽  
M. Pannella ◽  
J. J. Mohr ◽  
A. Saro ◽  
M. L. N. Ashby ◽  
...  
Keyword(s):  
Star Formation ◽  
Mass Range ◽  
Space Telescopes ◽  
Cluster Galaxy ◽  
Central Regions ◽  
Galaxy Populations ◽  
Galaxy Population ◽  
Stellar Masses ◽  
The Impact ◽  
Massive Clusters

We present the first results from a galaxy population study in the highest redshift galaxy clusters identified in the 2500 deg2 South Pole Telescope Sunyaev Zel’dovich effect (SPT-SZ) survey, which is sensitive to M500 ≳ 3 × 1014 M⊙ clusters from z ∼ 0.2 out to the highest redshifts where such massive structures exist. The cluster selection is to first order independent of galaxy properties, making the SPT-SZ sample particularly well suited for cluster galaxy population studies. We carried out a four-band imaging campaign with the Hubble and Spitzer Space Telescopes of the five z ≳ 1.4, S/NSZE >  5 clusters, that are among the rarest most massive clusters known at this redshift. All five clusters show clear overdensities of red galaxies whose colors agree with the initial cluster redshift estimates, although one (SPT-CLJ0607–4448) shows a galaxy concentration much less prominent than the others. The highest redshift cluster in this sample, SPT-CLJ0459–4947 at z ∼ 1.72, is the most distant M500 >  1014 M⊙ cluster discovered thus far through its intracluster medium, and is one of only three known clusters in this mass range at z ≳ 1.7, regardless of selection. Based on UVJ-like photometric classification of quiescent and star-forming galaxies, we find that the quiescent fraction in the cluster central regions (r/r500 <  0.7) is higher than in the field at the same redshift, with corresponding environmental quenching efficiencies typically in the range ∼0.5 − 0.8 for stellar masses log(M/M⊙) > 10.85. We have explored the impact of emission from star formation on the selection of this sample, concluding that all five clusters studied here would still have been detected with S/NSZE> 5, even if they had the same quiescent fraction as measured in the field. Our results thus point towards an efficient suppression of star formation in the central regions of the most massive clusters, occurring already earlier than z ∼ 1.5.

scholarly journals Activity in the Nuclei of Normal Sbc Galaxies - A Multiwavelength Study

1989 ◽  
Vol 134 ◽  
pp. 520-521
Author(s):  
R. D. Davies ◽  
A. Pedlar ◽  
D.J. Axon ◽  
B. Vila ◽  
E. Hummel ◽  
...  
Keyword(s):  
Star Formation ◽  
Strongly Correlated ◽  
Nuclear Activity ◽  
Normal Galaxies ◽  
Type Activity ◽  
Hubble Flow ◽  
Selection Of

This study of the activity in the nuclei of normal galaxies began as an investigation into the spread in the observed properties of normal galaxies used as standard candles in measurements of departures from the Hubble flow (Hart & Davies 1982). Extensive studies of the integrated properties of normal galaxies show the influence on these properties of quiescent star formation and embedded starburst-type activity (Staveley-Smith & Davies, 1987,1988). Normal galaxies have a significant level of nuclear activity, although it is not strongly correlated with their integrated properties. This investigation of nuclear activity is based on a sample of the 100 brightest nearby Sbc galaxies, a sample unbiassed in its selection of activity.

scholarly journals Low dust emissivities and radial variations in the envelopes of Class 0 protostars: possible signature of early grain growth

2019 ◽  
Vol 632 ◽  
pp. A5 ◽  
Author(s):  
M. Galametz ◽  
A. J. Maury ◽  
V. Valdivia ◽  
L. Testi ◽  
A. Belloche ◽  
...  
Keyword(s):  
Grain Size ◽  
Star Formation ◽  
Grain Growth ◽  
Central Region ◽  
Radial Gradient ◽  
Central Regions ◽  
Dust Composition ◽  
Dust Grain ◽  
Early Phases ◽  
Inner Envelope

Context. Analyzing the properties of dust and its evolution in the early phases of star formation is crucial to put constraints on the collapse and accretion processes as well as on the pristine properties of planet-forming seeds. Aims. In this paper, we aim to investigate the variations of the dust grain size in the envelopes of the youngest protostars. Methods. We analyzed Plateau de Bure interferometric observations at 1.3 and 3.2 mm for 12 Class 0 protostars obtained as part of the CALYPSO survey. We performed our analysis in the visibility domain and derived dust emissivity index (β1−3mm) profiles as a function of the envelope radius at 200–2000 au scales. Results. Most of the protostellar envelopes show low dust emissivity indices decreasing toward the central regions. The decreasing trend remains after correction of the (potentially optically thick) central region emission, with surprisingly low β1−3mm < 1 values across most of the envelope radii of NGC 1333-IRAS 4A, NGC 1333-IRAS 4B, SVS13B, and Serpens-SMM4. Conclusions. We discuss the various processes that could explain such low and varying dust emissivity indices at envelope radii 200–2000 au. Our observations of extremely low dust emissivity indices could trace the presence of large (millimeter-size) grains in Class 0 envelopes, in which case our results would point to a radial increase of the dust grain size toward the inner envelope regions. While it is expected that large grains in young protostellar envelopes could be built via grain growth and coagulation, we stress that the typical timescales required to build millimeter grains in current coagulation models are at odds with the youth of our Class 0 protostars. Additional variations in the dust composition could also partly contribute to the low β1−3mm we observe. We find that the steepness of the β1−3mm radial gradient depends strongly on the envelope mass, which might favor a scenario in which large grains are built in high-density protostellar disks and transported to the intermediate envelope radii, for example with the help of outflows and winds.

scholarly journals 12.1. The central regions of the Galaxy and galaxies: a brief summary

1998 ◽  
Vol 184 ◽  
pp. 495-499 ◽  
Author(s):  
F. Combes
Keyword(s):  
Galactic Center ◽  
Normal Galaxies ◽  
The Galaxy ◽  
Central Regions

This symposium has revealed considerable new progress on nuclei of galaxies over the last three years. In this talk, I will try to point out the advances since the last meeting on exactly the same subject held three years ago at Ringberg Castle in Germany (see “The Nuclei of Normal Galaxies: Lessons from the Galactic Center”, ed. R. Genzel & A. Harris, Kluwer).

Sign in / Sign up

Export Citation Format

Share Document