HIGH SURFACE BRIGHTNESS GALAXIES: Deffinition, Star formation, basic data

  The small group of High Surface Brightness Galaxies offers a large field of studying different properties of the galaxies at all. They was registered amongst the Seyfert Galaxies, X-ray sources, High Luminosity Objects and many Infra Red sources.

Holmberg,1952, making detailed surface photometry of ca. 100 bright galaxies define B<=13.6 [mag./sqr.min] as a border split the objects with high surface brightness from the normal one. Arakelian,1974 found, that many physical characteristics of the galaxies correlated with their surface brightness. Amongst them are spectrum emission lines, radio emission, colors etc.

#Using Holmberg’s criteria Arakelian,1975 determined the surface brightness of all galaxies north of Delta <= -3 deg having 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 = m_Zw + 2.5Lg(Pi/4*D*d) - 0.22cosec(bII) [m/sqr.sec]

Statistically B_akn are transfomed to Holmberg's one using the simple relations based on the least square fit for ca. 100 common objects:

(2) B_Akn = B + 0.22D/d + 0.73

Thus Arakelian,1975 devided 591 objects with HSB in northern hemispere. Kojoian et al.,1981 determined accurate optical positions for these objects.
#Using Arakelian's criteria Petrov,1986 presents a list of 47 new galaxies with High Surface Brightness (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 SyG - IZw 1 and IIZw 136.

As there was some proposals (e.g. Karachentsev et al,1986) the HSBG simple are the most compact part of the normal galaxies we try to show they are quite a homogenous group. To prove that we reduce the Arakelian's system of surface brightness to the standard isophote 25 mag./sqr.sec. The reduction procedure includes conversion of the MCG_diameters to D_25 (Paturel, 1977)

(3) D_25 = D_25(al,del,T,bII)

Zwicky magnitudes m_Zw to corrected Holmberg's m_holm one

(4) m_corr = m_holm(m_Zw,D,al,del,T,bII,R)

i.e. (5) SB_25 = m_corr + 2.5Lg(Pi/4*D_25*D_25) + 8,89 [m/sqr.sec]

and (6) SB_25 = (0.882+-0.077)B_Akn + (2.322+-1.675)

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   #Comparison of basic properties of the Normal and High Surface Brightness Galaxies. What are "normal" galaxies - till now most of the astronomers use the evaluations made by E. Holmberg or G. de Vaucouleurs many years ago based usually on small sample of galaxies. We construct a basic picture of normal galaxies using the homogenous sample of 1939 objects not belonged to any group of galaxies such as SyG, MrkG, AknG, 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 the High Surface Brightness Galaxies are 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 HSBG ones.

· The HSBG are a sample of the normal galaxies with in average higher Surface Brightness, higher luminosities and smaller diameters

· The HSBG are further in average.

· IR luminosities are more common for the more compact objects.

· Amongst CfA normal galaxies there is 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.

Created by G.T. Petrov