69 research outputs found
Using member galaxy luminosities as halo mass proxies of galaxy groups
Reliable halo mass estimation for a given galaxy system plays an important
role both in cosmology and galaxy formation studies. Here we set out to find
the way that can improve the halo mass estimation for those galaxy systems with
limited brightest member galaxies been observed. Using four mock galaxy samples
constructed from semi-analytical formation models, the subhalo abundance
matching method and the conditional luminosity functions, respectively, we find
that the luminosity gap between the brightest and the subsequent brightest
member galaxies in a halo (group) can be used to significantly reduce the
scatter in the halo mass estimation based on the luminosity of the brightest
galaxy alone. Tests show that these corrections can significantly reduce the
scatter in the halo mass estimations by to in massive
halos depending on which member galaxies are considered. Comparing to the
traditional ranking method, we find that this method works better for groups
with less than five members, or in observations with very bright magnitude cut.Comment: ApJ accepte
The Chocolate Chip Cookie Model: dust-to-metal ratio of HII regions
Using a sample of face-on star-forming galaxies selected from the Sloan
Digital Sky Survey, we statistically derive the typical optical depth
of individual HII regions based on the ``Chocolate Chip
Cookie" model of Lu2022. By binning galaxies into stellar mass and gas-phase
metallicity bins and interpreting as the dust to gas ratio
(DGR) of HII regions, we further investigate the correlations among DGR and
stellar mass, gas-phase metallicity respectively. We find that DGR increases
monotonically with the stellar mass of galaxies. At a given stellar mass, DGR
shows a linear correlation with the gas-phase metallicity, which implies a
constant dust to metal ratio (DTM) of galaxies at a given stellar mass. These
results adequately indicate that the DTM of galaxies is simply a function of
their stellar masses. In terms of gas-phase metallicity, because of the
mass-metalliciy relation, DTM increases with increasing metallicity with a
power-law index 1.45 in the low metallicity region, while remains constant at
the high metallicity end.Comment: 9 pages, 4 figure
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