arXiv subjects

Cai-Na Hao

Publications and source records attributed to Cai-Na Hao.

23 records · Page 2Linked to original sources

arXiv2013

Revisiting the Dichotomy of Early-type Galaxies

We study the relationship among isophotal shapes, central light profiles and kinematic properties of early-type galaxies (ETGs) based on a compiled sample of 184 ETGs. These sample galaxies are included in the Data Release 8 of Sloan Digital Sky Survey (SDSS DR8) and have central light profiles and kinematic properties available from the literature, which were measured based on Hubble Space Telescope ({\it HST}) and \atlas\ integral-field spectrograph (IFS) observations, respectively. We find that there is only a weak correlation between the isophotal shape ($a_{4}/a$) and the central light profile (within $1\,\rm kpc$) of ETGs. About two-fifths of "core" galaxies have disky isophotes, while one-third of "power-law" galaxies are boxy deviated. Our statistical results also show that there are weak correlations between galaxy luminosity and dynamical mass with $a_{4}/a$, but such correlations are tighter with central light profile. Moreover, no clear link has been found between the isophotal shape and the S\' ersic index. Comparisons show that there are similar correlations between $a_{4}/a$ and ellipticity and between $a_{4}/a$ and specific angular momentum $λ_{R_e/2}$ for "power-law" ETGs, but there are no such correlations for "core" ETGs. Therefore, we speculate that the bimodal classifications for ETGs are not as simple as previously thought, though we also find that the most deviated disky ETGs are "power-law", more elongated and fast rotators.

astro-ph.CO↗

arXiv2012

Characterizing Ultraviolet and Infrared Observational Properties for Galaxies. I. Influences of Dust Attenuation and Stellar Population Age

The correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color, i.e. the IRX-UV relation, was regarded as a prevalent recipe for correcting extragalactic dust attenuation. Considerable dispersion in this relation discovered for normal galaxies, however, complicates its usability. In order to investigate the cause of the dispersion, in this paper, we select five nearby spiral galaxies, and perform spatially resolved studies on each of the galaxies, with a combination of ultraviolet and infrared imaging data. We measure all positions within each galaxy and divide the extracted regions into young and evolved stellar populations. By means of this approach, we attempt to discover separate effects of dust attenuation and stellar population age on the IRX-UV relation for individual galaxies. In this work, in addition to dust attenuation, stellar population age is interpreted to be another parameter in the IRX-UV function, and the diversity of star formation histories is suggested to disperse the age effects. At the same time, strong evidence shows the necessity of more parameters in the interpretation of observational data, such as variations in attenuation/extinction law. Fractional contributions of different components to the integrated luminosities of the galaxies suggest that the integrated measurements of galaxies which comprise different populations would weaken the effect of the age parameter on IRX-UV diagrams. The dependance of the IRX-UV relation on luminosity and radial distance in galaxies presents weak trends, which offers an implication of selective effects. The two-dimensional maps of the UV color and the infrared-to-ultraviolet ratio are displayed and show a disparity in the spatial distributions between the two parameters in galaxies, which offers a spatial interpretation of the scatter in the IRX-UV relation.

astro-ph.CO↗

arXiv2011

Dust-Corrected Star Formation Rates of Galaxies. II. Combinations of Ultraviolet and Infrared Tracers

We present new calibrations of far-ultraviolet (FUV) attenuation as derived from the total infrared to FUV luminosity ratio (IRX) and the FUV-NUV color. We find that the IRX-corrected FUV luminosities are tightly and linearly correlated with the attenuation-corrected Hα luminosities (as measured from the Balmer decrement), with a rms scatter of $\pm 0.09$ dex. The ratios of these attenuation-corrected FUV to Hα luminosities are consistent with evolutionary synthesis model predictions, assuming a constant star formation rate over 100 Myr, solar metallicity and either a Salpeter or a Kroupa IMF with lower and upper mass limits of 0.1 and 100\msun. The IRX-corrected FUV to Balmer-corrected Hα luminosity ratios do not show any trend with other galactic properties over the ranges covered by our sample objects. In contrast, FUV attenuation derived from the FUV-NUV color (UV spectral slope) show much larger random and systematic uncertainties. When compared to either Balmer-corrected Hα luminosities or IRX-corrected FUV luminosities the color-corrected FUV luminosities show $\sim 2.5$ times larger rms scatter, and systematic nonlinear deviations as functions of luminosity and other parameters. Linear combinations of 25um and 1.4GHz radio continuum luminosities with the observed FUV luminosities are also well correlated with the Balmer-corrected Hα luminosities. These results provide useful prescriptions for deriving attenuation-corrected star formation rates of galaxies based on linear combinations of UV and IR or radio luminosities, which are presented in convenient tabular form. Comparisons of our calibrations with attenuation corrections in the literature and with dust attenuation laws are also made.

astro-ph.CO↗

arXiv2009

Dust-Corrected Star Formation Rates of Galaxies. I. Combinations of H-alpha and Infrared Tracers

We combine H-alpha emission-line and infrared continuum measurements of two samples of nearby galaxies to derive dust attenuation-corrected star formation rates (SFRs). We use a simple energy balance based method that has been applied previously to HII regions in the Spitzer Infrared Nearby Galaxies Survey (SINGS), and extend the methodology to integrated measurements of galaxies. We find that our composite H-alpha+IR based SFRs are in excellent agreement with attenuation-corrected SFRs derived from integrated spectrophotometry, over the full range of SFRs (0.01 -- 80 solar mass per year) and attenuations (0 -- 2.5 mag) studied. We find that the combination of H-alpha and total infrared luminosities provides the most robust SFR measurements, but combinations of H-alpha measurements with monochromatic luminosities at 24 micron and 8 micron perform nearly as well. The calibrations differ significantly from those obtained for HII regions (Calzetti et al. 2007), with the difference attributable to a more evolved population of stars heating the dust. Our results are consistent with a significant component of diffuse dust (the `IR cirrus' component) that is heated by a non-star-forming population. The same methodology can be applied to [OII]$λ$3727 emission-line measurements, and the radio continuum fluxes of galaxies can be applied in place of IR fluxes when the latter are not available. We assess the precision and systematic reliability of all of these composite methods.

astro-ph.CO↗

arXiv2005

A Catalog of Luminous Infrared Galaxies in the IRAS Survey and the Second Data Release of the SDSS

We select the Luminous Infrared Galaxies by cross-correlating the Faint Source Catalogue (FSC) and Point Source Catalogue (PSC) of the IRAS Survey with the Second Data Release of the SDSS for studying their infrared and optical properties. The total number of our sample is 1267 for FSC and 427 for PSC by using 2$σ$ significance level cross-section. The "likelihood ratio" method is used to estimate the sample's reliability and for a more reliable subsample (908 for FSC and 356 for PSC) selection. Then a Catalog with both the infrared, optical and radio informations is presented and will be used in further works. Some statistical results show that the Luminous Infrared Galaxies are quite different from the Ultra-Luminous Infrared Galaxies. The AGN fractions of galaxies with different infrared luminosities and the radio to infrared correlations are consist with previous studies.

astro-ph↗