Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMassive Star Formation Rates and Radial Distributions from Halpha Imaging of 84 Virgo Cluster and Isolated Spiral Galaxies
200
0
0.0
(
0
)
Added by
Rebecca A. Koopmann
Publication date
2002
fields
Physics
and research's language is
English
Authors
Rebecca A. Koopmann
Ask ChatGPT about the research
No Arabic abstract
The massive star formation properties of 55 Virgo Cluster and 29 isolated S0-Scd bright (M(B) < -18) spiral galaxies are compared via analyses of R and Halpha surface photometry and integrated fluxes as functions of Hubble type and central R light concentration (bulge-to-disk ratio). In the median, the total normalized massive star formation rates (NMSFRs) in Virgo Cluster spirals are reduced by factors up to 2.5 compared to isolated spiral galaxies of the same type or concentration, with a range from enhanced (up to 2.5 times) to strongly reduced (up to 10 times). Within the inner 30% of the optical disk, Virgo Cluster and isolated spirals have similar ranges in NMSFRs, with similar to enhanced median NMSFRs for Virgo galaxies. NMSFRs in the outer 70% of the optical disk are reduced in the median by factors up to 9 for Virgo Cluster spirals, with more severely reduced star formation at progressively larger disk radii. Thus the reduction in total star formation of Virgo Cluster spirals is caused primarily by spatial truncation of the star-forming disks. The correlation between HI deficiency and R light central concentration is much weaker than the correlation between HI deficiency and Hubble type. ICM-ISM stripping of the gas from spiral galaxies is likely responsible for the truncated star-forming disks of Virgo Cluster spirals. This effect may be responsible for a significant part of the morphology-density relationship.
rate research
Read More
We present the analysis of Halpha3, an Halpha imaging survey of 409 galaxies selected from the HI Arecibo ALFALFA Survey in the Local Supercluster, including the Virgo cluster. We explore the relations between the stellar mass, the HI mass and the current, massive SFR of nearby galaxies in the Virgo cluster and we compare them with those of isolated galaxies in the Local Supercluster, disentangling the role of the environment in shaping the star formation properties of galaxies at the present cosmological epoch. We investigate the relationships between atomic neutral gas and newly formed stars in different environments, across many morphological types, and over a wide range of stellar masses adopting an updated calibration of the HI deficiency parameter. Studying the mean properties of late-type galaxies in the Local Supercluster, we find that galaxies in increasing local galaxy density conditions (or decreasing projected angular separation from M87) show a significant decrease in the HI content and in the mean specific star formation rate, along with a progressive reddening of their stellar populations. The gradual quenching of the star formation occurs outside-in, consistently with the predictions of the ram pressure model. Once considered as a whole, the Virgo cluster is effective in removing neutral hydrogen from galaxies, and this perturbation is strong enough to appreciably reduce the SFR of its entire galaxy population. An estimate of the present infall rate of 300-400 galaxies per Gyr in the Virgo cluster is obtained from the number of existing HI-rich late-type systems, assuming 200-300 Myr as the time scale for HI ablation. If the infall process has been acting at constant rate this would imply that the Virgo cluster has formed approximately 2 Gyr ago, consistently with the idea that Virgo is in a young state of dynamical evolution.
Using a recently completed survey of faint (sub-mJy) radio sources, selected at 1.4 GHz, a dust-free estimate of the local star formation rate (SFR) is carried out. The sample is 50% complete to 0.2 mJy, with over 50% of the radio sources having optical counterparts brighter than R = 21.5. Spectroscopic observations of 249 optically identified radio sources have been made, using the 2-degree Field (2dF) facility at the Anglo-Australian Telescope (AAT). Redshifts and equivalent widths of several spectral features (e.g., Halpha and [OII]3727) sensitive to star formation have been measured and used to identify the star-forming and absorption-line systems. The spectroscopic sample is corrected for incompleteness and used to estimate the 1.4 GHz and Halpha luminosity functions (LFs) and luminosity density distributions. The 1.4 GHz LF of the star-forming population has a much steeper faint-end slope (1.85) than that for the ellipticals (1.35). This implies an increasing preponderance of star-forming galaxies among the optically identified (i.e., z < 1) radio sources at fainter flux densities. The Halpha LF of the faint radio population agrees with published Halpha LFs derived from local samples selected by Halpha emission. This suggests that the star-forming faint radio population is coincident with the Halpha selected galaxies. The 1.4 GHz and Halpha luminosity densities have been used to estimate the SFRs. The two estimates agree, both giving a SFR density of $0.032 M_odot yr^{-1} Mpc^{-3}$ in the range z < 1.
We present a systematic investigation of the star formation rate (hereafter SFR) in interacting disk galaxies. We determine the dependence of the overall SFR on different spatial alignments and impact parameters of more than 50 different configurations in combined N-body/hydrodynamic simulations. We also show mass profiles of the baryonic components. We find that galaxy-galaxy interactions can enrich the surrounding intergalatic medium with metals very efficiently up to distances of several 100 kpc. This enrichment can be explained in terms of indirect processes like thermal driven galactic winds or direct processes like kinetic spreading of baryonic matter. In the case of equal mass mergers the direct -kinetic- redistribution of gaseous matter (after 5 Gyr) is less efficient than the environmental enrichment of the same isolated galaxies by a galactic wind. In the case of non-equal mass mergers however, the direct -kinetic- process dominates the redistribution of gaseous matter. Compared to the isolated systems, the integrated star formation rates (ISFRs) ($int_{t = 0 Gyr}^{t = 5 Gyr}textnormal{SFR(t)}dt$) in the modelled interacting galaxies are in extreme cases a factor of 5 higher and on average a factor of 2 higher in interacting galaxies. Co-rotating and counter-rotating interactions do not show a common trend for the enhancement of the ISFRs depending on the interaction being edge-on or face-on. The latter case shows an increase of the ISFRs for the counter-rotating system of about 100%, whereas the edge-on counter-rotating case results in a lower increase ($sim$ 10%).
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
