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Register a new userLuminosity and Stellar Mass Functions of Local Star-Forming Galaxies
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Pablo G. Perez-Gonzalez
Publication date
2003
fields
Physics
and research's language is
English
Authors
P.G. Perez-Gonzalez
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We present the optical and near-infrared luminosity and mass functions of the local star-forming galaxies in the Universidad Complutense de Madrid Survey. A bivariate method which explicitly deals with the Halpha selection of the survey is used when estimating these functions. Total stellar masses have been calculated on a galaxy-by-galaxy basis taking into account differences in star formation histories. The main difference between the luminosity distributions of the UCM sample and the luminosity functions of the local galaxy population is a lower normalization (phi^*), indicating a lower global volume density of UCM galaxies. The typical near-infrared luminosity (L^*) of local star-forming galaxies is fainter than that of normal galaxies. This is a direct consequence of the lower stellar masses of our objects. However, at optical wavelengths (B and r) the luminosity enhancement arising from the young stars leads to M^* values that are similar to those of normal galaxies. The fraction of the total optical and near infrared luminosity density in the local Universe associated with star-forming galaxies is 10-20%. Fitting the total stellar mass function using a Schechter parametrization we obtain alpha=-1.15+/-0.15, log({M}^*)=10.82+/-0.17 Msun and log(phi^*)=-3.04+/-0.20 Mpc^{-3}. This gives an integrated total stellar mass density of 10^{7.83+/-0.07} Msun Mpc^{-3} in local star-forming galaxies (H_0=70 km s^{-1} Mpc^{-1}, Omega_M=0.3, Lambda=0.7). The volume-averaged burst strength of the UCM galaxies is b=0.04+/-0.01, defined as the ratio of the mass density of stars formed in recent bursts (age<10 Myr) to the total stellar mass density in UCM galaxies. Finally, we derive that, in the local Universe, (13+/-3)% of the total baryon mass density in the form of stars is associated with star-forming galaxies.
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The main goal of this thesis work is studying the main properties of the stellar populations embedded in a statistically complete sample of local active star-forming galaxies: the Universidad Complutense de Madrid (UCM) Survey of emission-line galaxies. This sample contains 191 local star-forming galaxies at an average redshift of 0.026. The survey was carried out using an objective-prism technique centered at the wavelength of the Halpha nebular emission-line (a common tracer of recent star formation). (continues)
We constrain the mass distribution in nearby, star-forming galaxies with the Star Formation Reference Survey (SFRS), a galaxy sample constructed to be representative of all known combinations of star formation rate (SFR), dust temperature, and specific star formation rate (sSFR) that exist in the Local Universe. An innovative two-dimensional bulge/disk decomposition of the 2MASS/$K_{s}$-band images of the SFRS galaxies yields global luminosity and stellar mass functions, along with separate mass functions for their bulges and disks. These accurate mass functions cover the full range from dwarf galaxies to large spirals, and are representative of star-forming galaxies selected based on their infra-red luminosity, unbiased by AGN content and environment. We measure an integrated luminosity density $j$ = 1.72 $pm$ 0.93 $times$ 10$^{9}$ L$_{odot}$ $h^{-1}$ Mpc$^{-3}$ and a total stellar mass density $rho_{M}$ = 4.61 $pm$ 2.40 $times$ 10$^{8}$ M$_{odot}$ $h^{-1}$ Mpc$^{-3}$. While the stellar mass of the emph{average} star-forming galaxy is equally distributed between its sub-components, disks globally dominate the mass density budget by a ratio 4:1 with respect to bulges. In particular, our functions suggest that recent star formation happened primarily in massive systems, where they have yielded a disk stellar mass density larger than that of bulges by more than 1 dex. Our results constitute a reference benchmark for models addressing the assembly of stellar mass on the bulges and disks of local ($z = 0$) star-forming galaxies.
We present the integrated properties of the stellar populations in the Universidad Complutense de Madrid Survey galaxies. Applying the techniques described in the first paper of this series, we derive ages, burst masses and metallicities of the newly-formed stars in our sample galaxies. The population of young stars is responsible for the Halpha emission used to detect the objects in the UCM Survey. We also infer total stellar masses and star formation rates in a consistent way taking into account the evolutionary history of each galaxy. We find that an average UCM galaxy has a total stellar mass of ~1E10 Msun, of which about 5% has been formed in an instantaneous burst occurred about 5 Myr ago, and sub-solar metallicity. Less than 10% of the sample shows massive starbursts involving more than half of the total mass of the galaxy. Several correlations are found among the derived properties. The burst strength is correlated with the extinction and with the integrated optical colours for galaxies with low obscuration. The current star formation rate is correlated with the gas content. A stellar mass-metallicity relation is also found. Our analysis indicates that the UCM Survey galaxies span a broad range in properties between those of galaxies completely dominated by current/recent star formation and those of normal quiescent spirals. We also find evidence indicating that star-formation in the local universe is dominated by galaxies considerably less massive than L*.
We present a panchromatic study of luminosity functions (LFs) and stellar mass functions (SMFs) of galaxies in the core of the Shapley supercluster at z=0.048, in order to investigate how the dense environment affects the galaxy properties, such as star formation (SF) or stellar masses. We find that while faint-end slopes of optical and NIR LFs steepen with decreasing density, no environment effect is found in the slope of the SMFs. This suggests that mechanisms transforming galaxies in different environments are mainly related to the quench of SF rather than to mass-loss. The Near-UV (NUV) and Far-UV (FUV) LFs obtained have steeper faint-end slopes than the local field population, while the 24$mu$m and 70$mu$m galaxy LFs for the Shapley supercluster have shapes fully consistent with those obtained for the local field galaxy population. This apparent lack of environmental dependence for the infrared (IR) LFs suggests that the bulk of the star-forming galaxies that make up the observed cluster IR LF have been recently accreted from the field and have yet to have their SF activity significantly affected by the cluster environment.
The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) is a radio continuum survey at 76-227 MHz of the entire southern sky (Declination $<+30deg$) with an angular resolution of $approx 2$ arcmin. In this paper, we combine GLEAM data with optical spectroscopy from the 6dF Galaxy Survey to construct a sample of 1,590 local (median $z approx 0.064$) radio sources with $S_{200,mathrm{MHz}} > 55$ mJy across an area of $approx 16,700~mathrm{deg}^{2}$. From the optical spectra, we identify the dominant physical process responsible for the radio emission from each galaxy: 73 per cent are fuelled by an active galactic nucleus (AGN) and 27 per cent by star formation. We present the local radio luminosity function for AGN and star-forming galaxies at 200 MHz and characterise the typical radio spectra of these two populations between 76 MHz and $sim 1$ GHz. For the AGN, the median spectral index between 200 MHz and $sim 1$ GHz, $alpha_{mathrm{high}}$, is $-0.600 pm 0.010$ (where $S propto u^{alpha}$) and the median spectral index within the GLEAM band, $alpha_{mathrm{low}}$, is $-0.704 pm 0.011$. For the star-forming galaxies, the median value of $alpha_{mathrm{high}}$ is $-0.650 pm 0.010$ and the median value of $alpha_{mathrm{low}}$ is $-0.596 pm 0.015$. Among the AGN population, flat-spectrum sources are more common at lower radio luminosity, suggesting the existence of a significant population of weak radio AGN that remain core-dominated even at low frequencies. However, around 4 per cent of local radio AGN have ultra-steep radio spectra at low frequencies ($alpha_{mathrm{low}} < -1.2$). These ultra-steep-spectrum sources span a wide range in radio luminosity, and further work is needed to clarify their nature.
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