HIGH SURFACE BRIGHTNESS GALAXIES
DEFINITION, STAR FORMATION, BASIC DATA
The small group of High Surface Brightness Galaxies (HSBGs) offers a large field of studying different properties of galaxies in general. HSBGs have been registered amongst Seyfert Galaxies, X-ray sources, high luminosity objects and many Infra Red sources.
Holmberg (1952), while making detailed surface photometry of ca. 100 bright galaxies, defined B≤13.6 [mag/sq.min] as a border splitting the high surface brightness objects from the normal one. Arakelian (1974) found that many physical characteristics of galaxies correlated with their surface brightness. Amongst them are spectral emission lines, radio emission, colours, etc.
Using Holmbergs criteria, Arakelian (1975) determined the surface brightness of all galaxies to the north of Delta ≤ -3 deg, that have photographic magnitudes in CGCG (Zwicky et al., 1960 - 1968) and diameters in MCG (Vorontsov-Vel'jaminov et al., 1962 -1968). The basic relation is
(1) B = mZw+ 2.5Lg(Pi/4*D*d) - 0.22cosec(bII) [m/sq.sec]
BAkn are transfomed to Holmberg's one using the simple relations based on the least square fit for ca. 100 common objects:
(2) BAkn = B + 0.22D/d + 0.73
Thus Arakelian (1975) differentiated 591 objects with HSB in the northern hemispere. Kojoian et al.1(981) determined accurate optical positions for these objects.
Using Arakelian's criteria, Petrov (1986) presented a list of 47 new galaxies with HSB (NHSBG) from the UGCG. Rem.: Nilson's diameters are systematically larger (i.e., lower SB). In this list there are 19 Zwicky (1971) compact galaxies (40%) and 2 SyGs - IZw 1 and IIZw 136.
As there were some speculations (e. g. Karachentsev et al, 1986) the HSBG simple is the most compact part of the normal galaxies. We tried to show they were quite a homogenous group, too. To prove that we reduced Arakelian's system of surface brightness to the standard isophote 25 mag/sq.sec. The reduction procedure included conversion of MCG-diameters to D25 (Paturel, 1977).
(3) D25 = D25 (al,del,T,bII)
The transformation of Zwicky magnitudes mZw to corrected Holmberg magnitudes mHolm is:
(4) mcorr = mHolm (mZw,D,al,del,T, bII,R)
i.e. (5) SB25 = mcorr + 2.5Lg(Pi/4*D25* D25) + 8,89 [m/sqr.sec]
and (6) SB25= (0.882+-0.077) BAkn + (2.322+-1.675)
COMPARISON OF THE BASIC PROPERTIES OF THE N ORMAL AND HIGH SURFACE BRIGHTNESS GALAXIES
What are "normal" galaxies? Up to now most astronomers have used the evaluations made by E. Holmberg or G. de Vaucouleurs many years ago based usually on small samples of galaxies. We construct a basic picture of normal galaxies using the homogenous sample of 1939 objects not belonging to any group of galaxies such as SyGs, MrkGs, AknGs, DDO galaxies, etc. up to 14.5 magnitude from the Center for Astrophysics, USA.
Student's "t- test" and Fisher's "f-test" have been used to check the statistical significances that the HSBGs are a homogenous group with different average parameters from the ones of the normal galaxies. The main differences are:
· The normal galaxies have lower luminosities and larger diameters than HSB ones;
· The HSBGs are a sample of the normal galaxies with on the average higher surface brightness, higher luminosities and smaller diameters;
· The HSBG are more distant on the average;
· IR luminosities are more common for the more compact objects;
· Amongst CfA normal galaxies there are new 93 objects with high
· We could expect increasing or constant SFR than decreasing one.
SURFACE BRIGHTNESS OF EMISSION-LINE GALAXIES
It is shown that the relative number of emission line galaxies significantly decreases with the decrease of the mean surface brightness. Similar phenomenon takes place when Zwicky compact galaxies are considered. These results are interpreted as due to the fact, that the duration of emission line phase is in correlation with the surface brightness of galaxies.
MEAN SURFACE BRIGHTNESS OF ISOLATED AND DOUBLE GALAXIES
The mean surface brightness of isolated galaxies and galaxies that are members of systems are compared in order to obtain information pertaining to the different conditions under which these galaxies were formed. The comparison of the spiral galaxies in the Catalog of Isolated Galaxies (Karachentseva, 1973) and the Catalog of Isolated Pairs (Karachentsev, 1972) reveals that the difference between the mean values of mean surface brightness of the corresponding galaxies equals 0.35. The mean surface brightness of the components of pairs are greater than those of isolated galaxies, indicating the dependence of the former on the separation of the components. The mean value of the mean surface brightness of the components of the pairs reaches that of the isolated galaxies at a distance r = 225 kpc, where the mutual influence of the components of pairs is greatly reduced.
OUR RESEARCH ON HIGH SURFACE BRIGHTNESS GALAXIES
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