Studies of the stellar populations of galaxies using two-color diagrams

Abstract

Variations in the photometric parameters of stellar systems as a function of their evolution and the stellar populations comprising them are investigated. A set of seven evolutionary models with an exponential decrease in the star-formation rate and 672 models with a secondary burst of star formation are considered. The occurrence of a secondary burst of star formation can shift the position of a stellar system on two-color diagrams to the right or left of the normal color sequence for galaxies and the extinction line. This makes it possible to estimate the composition of the stellar population of a galaxy with a nonmonotonic star formation history from its position on two-color diagrams. Surface photometry in both the optical (UBVRI) and near-IR (JHK) is used to study the stellar populations and star-formation histories in the structural components (nucleus, bulge, disk, spiral arms, bar, ring) of 26 galaxies of various morphological types (from S0 to Sd). Components (nucleus, bulge, bar) with color characteristics corresponding to stellar systems with secondary bursts of star formation are indicated in 10 of the 26 galaxies. The parameters of these secondary bursts are estimated. Five of the 10 galaxies with complex star-formation histories display clear structural perturbations. Appreciable differences in the photometric characteristics of relatively red early-type galaxies (S0-Sb) and relatively blue later-type galaxies (Sb-Sd) have been found. Galaxies of both early and late types are encountered among the Sb-galaxies. Lenticular galaxies do not display different photometric characteristics from early-type spiral galaxies.Comment: Slightly edited version of the paper published in the Astronomy Reports, 2015, 59, 899. 18 pages (21 pp. in original paper), 11 figures, 3 table

Spatial regularity of the young stellar population in the ring of NGC 6217

“…The results of the U BVRI photometry for the galaxy were published in Gusev et al (2015). We also use the Hα image, obtained in the GHASP survey (Epinat et al 2008) and downloaded from the NED data base, in our study.…”

A spectral and photometric study of 102 star-forming regions in seven spiral galaxies

“…b Radius of a galaxy at the isophotal level 25 mag/arcsec 2 in the B band corrected for Galactic extinction and inclination effects. Gusev et al (2015), 7 -Artamonov, Bruevich & Gusev (1997).…”

Azimuthal propagation of star formation in nearby spiral galaxies: NGC 628, NGC 3726 and NGC 6946

“…That is, the substance in the disc of NGC 3726 rotates in a counter clockwise direction. The circle itself with radius R C3 = 9.8 ± 1.0 kpc is the corotation circle, where the rotational ve- Gusev et al 2015Gusev et al , 2016. locity of the matter in the disc coincides with the rotational velocity of the spiral pattern.…”

“…The upper panel shows the SC-HiiR pairs outside spiral arm 1 as filled squares, the SC-HiiR pairs in spiral arm A are shown as open circles. The bottom panel shows the face-on B-image of NGC 6946 from our earlier papers (seeGusev et al 2015Gusev et al , 2016.…”