4 research outputs found
Spectral Energy Distributions of Dusty Galaxies
We present a SED model of dusty galaxies, in which the equation of radiative
transfer is solved by assuming spherical symmetry. The temperature fluctuation
of very small dust particles is calculated consistently with the radiative
transfer. The adopted dust model consists of graphite and silicate grains and
PAHs, whose relative fractions are determined for each MW, LMC and SMC type
extinction curve. This model allows us to derive the intrinsic SEDs of stellar
populations embedded in dusty ISM, which are very important indicators for the
age of stellar populations. Therefore, the evolutionary phase of starburst
galaxies which have frequently very dusty ISM can be investigated with this SED
model. We show that the SEDs of Arp220 and M82 can both be explained by the
same single stellar population, despite the significant differences in the SEDs
and the infrared luminosities. The apparent difference between their SEDs is
mainly caused by the difference in the optical depth. In contrast, the SED of
prototypical star-forming ERO, HR10, indicates that this galaxy is relatively
old comparing to Arp220 and M82. It is found that, in the case of optically
thin limit like elliptical galaxies, the optical depth cannot be inferred only
from the SED, due to a degeneracy between the optical depth, galactic size, and
the spatial distribution of dust; the latter two are important for estimating
the average temperature of dust grains in elliptical galaxies. When the
observed size of elliptical galaxies is adopted for the model geometry, SEDs
can be used to constrain the spatial distribution of dust in elliptical
galaxies.Comment: 36 pages, 21 figures, submitted to PAS
Deriving physical parameters of unresolved star clusters. VII. Adaptive aperture photometry of the M31 PHAT star clusters
This work is the seventh study in a series dedicated to investigating
degeneracies of simultaneous age, mass, extinction, and metallicity
determinations of partially resolved or unresolved star clusters with Hubble
Space Telescope broadband aperture photometry. In the sixth work (hereafter,
Paper I), it was demonstrated that the adaptive aperture photometry, performed
to avoid the majority of the projected foreground and background stars falling
within the apertures, gives more consistent colour indices for star clusters.
In this study, we aim to supplement the homogeneous multi-colour aperture
photometry results published in Paper~I and provide a complete M31 Panchromatic
Hubble Andromeda Treasury (PHAT) survey star cluster photometry catalogue for
further analysis. Following Paper I, we used a two-aperture approach for
photometry. The first aperture is the standard one used to measure total
cluster fluxes. The second (smaller) aperture is introduced to avoid the bright
foreground and background stars projecting onto the clusters. We selected the
radii of smaller apertures to be larger than the half-light radii of the
clusters. We present the second part of the star cluster aperture photometry
catalogues for a sample of 1477 star clusters from the M31 PHAT survey not
covered in Paper I. Compared to the M31 PHAT star cluster aperture photometry
catalogue published by Johnson et al., adjustments were made to the cluster
centre coordinates, aperture sizes, and sky background levels.Comment: 8 pages, 8 figures, accepted in A&