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
with HSB in northern hemispere. Kojoian
determined accurate optical positions for these objects.
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)<>
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
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.
Created by G.T. Petrov