ﻻ يوجد ملخص باللغة العربية
Multi-band photometric images from ultraviolet and optical to infrared are collected to derive spatially resolved properties of a nearby Scd type galaxy M 101. With evolutionary stellar population synthesis models, two-dimensional distributions and radial profiles of age, metallicity, dust attenuation, and star formation timescale in the form of the Sandage star formation history are obtained. When fitting with the models, we use the IRX-$A_mathrm{FUV}$ relation, found to depend on a second parameter of birth rate b (ratio of present and past-averaged star formation rate), to constrain the dust attenuation. There are obvious parameter gradients in the disk of M101, which supports the theory of an inside-out disk growth scenario. Two distinct disc regions with different gradients of age and color are discovered, similar to another late-type galaxy NGC 628. The metallicity gradient of the stellar content is flatter than that of H {sc ii} regions. The stellar disk is optically thicker inside than outside and the global dust attenuation of this galaxy is lower, compared with galaxies of similar and earlier morphological type. We highlight that a variational star formation timescale describes the real star formation history of a galaxy. The timescale increases steadily from the center to the outskirt. We also confirm that the bulge in this galaxy is a disk-like pseudobulge, whose evolution is likely to be induced by some secular processes of the small bar with relatively young age, rich metal, and much dust.
We present absorption-line index gradients for a sample of S0 galaxies in the Fornax Cluster. The sample has been selected to span a wide range in galaxy mass, and the deep VLT-FORS2 spectroscopy allows us to explore the stellar populations all the w
We present the stellar population and velocity dispersion gradients for a sample of 24 brightest cluster galaxies (BCGs) in the nearby Universe for which we have obtained high quality long-slit spectra at the Gemini telescopes. With the aim of studyi
This is the third paper of a series where we study the stellar population gradients (SP; ages, metallicities, $alpha$-element abundance ratios and stellar initial mass functions) of early type galaxies (ETGs) at $zle 0.08$ from the MaNGA-DR15 survey.
The great advances in the network of cosmological tests show that the relativistic Big Bang theory is a good description of our expanding universe. But the properties of nearby galaxies that can be observed in greatest detail suggest a still better t
We have extracted PSF-fitted stellar photometry from near-ultraviolet, optical and near-infrared images, obtained with the Hubble Space Telescope, of the nearby (D ~ 5.5 Mpc) SBm galaxy NGC 1311. The ultraviolet and optical data reveal a population o