Results of surface photometry of 50 galaxies in the Local Volume based on archived images obtained with the Hubble Space Telescope are presented. Integrated magnitudes in the V and I bands are ...introduced for the chosen galaxies, along with brightness and color profiles. The obtained photometric parameters are compared with the measurements of other authors.
Stellar photometry in nine fields around the giant elliptical galaxy M87 in the Virgo cluster is obtained from archival images of the Hubble Space Telescope. The resulting Hertzsprung-Russell ...diagrams show populated red-giant and AGB branches. The position of the tip the red-giant branch (the TRGB discontinuity) is found to vary with galactocentric distance. This variation can be interpreted as the effect of metal-rich red giants on the procedure of the measurement of the TRGB discontinuity or as a consequence of the existence of a weak gas-and-dust cloud around M87 extending out to 10’ along the galactocentric radius and causing
I
-band absorption of up to
0
.
m
2
near the center of the galaxy. The TRGB stars located far fromtheM87 center yield an average distancemodulus of (
m
-
M
) = 30.91 ± 0.08, which corresponds to the distance of
D
= 15.4± 0.6Mpc. It is shown that stars in the field located between M86 and M87 galaxies at angular separations of 37’ and 40’ are not intergalactic stars, but belong to the M87 galaxy, i.e., that the stellar halo of this galaxy can be clearly seen at a galactocentric distance of 190 kpc. The distances are measured to four dwarf galaxies P4anon, NGC4486A, VCCA039, and dSph-D07, whose images can be seen in the fields studied. The first three galaxies are M87 satellites, whereas dSph-D07 is located at a greater distance and is a member of the M86 group.
We present surface photometry and metallicity measurements for 104 nearby dwarf galaxies imaged with the Advanced Camera for Surveys and Wide Field and Planetary Camera 2 aboard the Hubble Space ...Telescope. In addition, we carried out photometry for 26 galaxies of the sample and for Sextans B on images of the Sloan Digital Sky Survey. Our sample comprises dwarf spheroidal, irregular and transition type galaxies located within ∼10 Mpc in the field and in nearby groups: M81, Centaurus A, Sculptor and Canes Venatici I cloud. It is found that the early-type galaxies have on average higher metallicity at a given luminosity in comparison to the late-type objects. Dwarf galaxies with MB≥−12 to −13 mag deviate towards larger scalelengths from the scalelength–luminosity relation common for spiral galaxies, h∝L0.5B. The following correlations between fundamental parameters of the galaxies are consistent with expectations if there is pronounced gas loss through galactic winds: (1) between the luminosity of early-type dwarf galaxies and the mean metallicity of constituent red giant branch stars, Z∼L0.4, (2) between mean surface brightness within the 25 mag arcsec−2 isophote and the corresponding absolute magnitude in the V and I bands, SB 25∼ 0.3M25 and (3) between the central surface brightness (or effective surface brightness) and integrated absolute magnitude of galaxies in the V and I bands, SB0∼ 0.5ML, SB e∼ 0.5 Me. The knowledge of basic photometric parameters for a large sample of dwarf galaxies is essential for a better understanding of their evolution.
—Based on archived images from the Hubble Space Telescope, stellar photometry of the dwarf galaxy Coma P, located near the Virgo galaxy cluster, was performed. The selection of weakly luminous ...regions of the galaxy showed that Coma P consists of two interacting dwarf galaxies, one of which has a weak star formation, and the second galaxy has a very low surface brightness, there is no star formation in it, and it can be called a “dark” galaxy. The distance to this pair of galaxies, measured by the TRGB method (
D
= 12
.
7 ± 0
.
9 Mpc), showed that Coma P is located on the periphery of the Virgo galaxy cluster.
A search for a correlation between the luminosities of the brightest stars and luminosities of their host galaxies was carried out on archival Hubble Space Telescope (HST)
or
(
V
) and
(
I
) images ...of 150 nearby galaxies. The sample contains only galaxies with ongoing star formation and with known distances we derived with the TRGB-method. We correlated the average absolute luminosities of the three brightest blue and the three brightest red stars with the luminosity of a host. We find a linear relation for both the blue and the red stars in irregular and low-mass spiral galaxies. Their scatters are sufficiently small (
) to make these relations useful for distance determination for low-mass galaxies. We found that all 31 dwarf galaxies
in our sample lack bright massive stars
, probably due to the physical conditions that prevent their birth. For galaxies with higher an average luminosity in the range
, there is an asymmetry in the distribution of the number of galaxies relative to the linear dependence, indicating an increase in the fraction of galaxies with bright stars.
Absctract
—The present study continues the investigation of the super-fast variability of line profiles in the spectra of stars of early spectral types. We studied the line-profile variability in the ...spectrum of the binary (O9.7Ib+B0III) star
Ori A using the MSS spectrograph of the 6-m BTA telescope based on observations carried out on February 19, 2019. Short-period regular variations of the hydrogen Balmer lines and He I lines with periods from 89 to 295 minutes were found. The presence of short-period variations in the period interval of 10–20 minutes is also possible. An analysis of the stellar brightness variations from observations by the TESS satellite showed the presence of seven regular components, one of which is probably the second harmonic of the rotation period of the main component of the Aa star
Ori A. The magnetic field of the star was determined for the whole series of observations. The longitudinal component of the root-mean-square magnetic field measured by the regression method over the whole observation period is
G.
The results of observations at high temporal resolution (∆T~4 min) of the B0.5V star ε Per A on the 2-m telescope of the Terskol Observatory are reported. Regular components of variations in line ...profiles with periods 1.5-18 hours are recorded. Evidence of irregular variations in line profiles on time scales of minutes is detected. The nature of these variations is discussed.
We analyze new observational data obtained at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences with the SCORPIO focal reducer for the peculiar galaxy UGC ...1198. Based on these data, we have concluded that UGC 1198 is a dwarf elliptical galaxy (
dE
) with evidence of interaction. A kinematic study of UGC 1198 has shown that at least two systems are observed in this object. One of them is associated with the stellar system of UGC 1198 itself with weak rotation around the minor axis of the galaxy. The second system is associated with the gaseous disk/ring rotating at an angle of 72° to the equatorial plane of the galaxy. The gaseous polar disk/ring could be formed during the merger of a dwarf elliptical galaxy with a galaxy of approximately the same or lower mass containing a gas. The mean age of the stellar population at
r
≥ 5″ is 2 × 10
9
yr. The interaction as a result of which the galaxy under study was formed can be assumed to have occurred less than one billion years ago.
The displacement of phosphorus from ferrophosphorus (24.89% P, 67.82% Fe) by FeSi
2
is studied by thermodynamic simulation. The melting of electrothermic ferrophosphorus with FS65 ferrosilicium with ...the extraction of gaseous phosphorus and the formation of a complex ferroalloy containing 42.8–44.3% Si, 50–52.4% Fe, 1.8–2.0% Mn, and 1.4–1.6% P is experimentally investigated.
We analyze new optical spectroscopic observations obtained at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences with the SCORPIO focal reducer (in the ...modes of a Fabry–Perot interferometer (FPI) and long-slit spectroscopy) and the Multi-Pupil Fiber Spectrograph for the galaxy IC 883. We have confirmed that the main body of the galaxy rotates around its minor axis. The positions of the dynamical axes of the stellar and gaseous components have been found to differ by ~10°. The velocities in the SE tail do not correspond to the circular rotation around the galaxy’s minor axis. This structure is probably a fragment of an unwound curved spiral arm. Regions with high velocity dispersions and peculiarities in the velocity fields have been found along the minor axis. Our study of the age and metallicity of the galaxy’s stellar population has shown that the mean values of these parameters in the stellar disk, except for the central region (
r
≤ 5ʺ), are ≈1 Gyr and ≈−0.4 dex, respectively. Both young (2−5 × 10
8
yr) and old (5−10 × 109 yr) stellar populations are present in the circumnuclear region. Our analysis of the spectroscopic data for the bright feature 8ʺ south of the nucleus coincident in position with a compact X-ray source has shown that this is apparently a dwarf galaxy or a remnant of a companion galaxy. Our FPI observations in the Hα emission line and direct images have revealed a region of ionized gas that together with the already known structures along the minor axis forms a clumpy tidal structure of ionized gas pulled from the companion galaxy. The results of our study confirm the previously proposed hypothesis that the observed peculiar structures were formed by the merger of two galaxies. However, it can be said that IC 883 does not belong to the class of polar-ring galaxies.
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