An Unusual Group of Low Surface Brightness Galaxies in the Region 1046 + 65

Abstract

A complex of I I objects with a surface brightness of about 26 mag/m" is detected in the direction of the M~I group of galaxies. The argumentes are presented in favour of the fact that they are a t the distance of the M81 group; their linear diameters (2 to 3 kpc) and absolute magnitudes ( M B = -I ~m to -I z m ) are in agreement with the parameters of the known dwarf galaxies of the Local group. An assumption about the tidal stability of the complex of dwarfs relative to M81 gives an estimation of its summary mass 2 I -IO* M a and of its mass-to-luminosity ratio %/L 2 1.2 in the solar units.Eine Gruppe von 11 Galaxien mit einer Flachenhelligkeit von etwa 26 m a g / n " wurde in Richtung der M8I-Gruppe entdeckt. Unter der Annahme gleicher Entfernung wie die M8I-Gruppe stimmen ihre linearen Durchmesser (2 -3 kpc) und ihre absoluten Helligkeiten ( M B = -I ~m bis -I z m mit den Parametern der Zwerggalaxien der Lokalen Gruppe iiberein. Annahmen tiber die Stabilitat der Zwerggruppe gegeniiber M8 I erlauben eine Abschatzung ihrer Gesamtmasse zu % 2 I -108Mg und ihres Masse-Leuchtkraftverhaltnisses %/L 2 1.2 (in Sonneneinheiten).

Structure and stellar content of dwarf galaxies

“…In Appendix A we discuss the possible nature of an unusual clustering of low-surface brightness objects in the south-east corner of the M 81 group. While the case for extra-galactic objects (Börngen et al 1984) remains viable, we argue in favour of a galactic nature (cirrus clouds) for at least some of the cases.…”

“…This list was prepared by Binggeli (Van Driel et al 1998) based on Börngen et al (1982Börngen et al ( , 1984 and Karachentseva et al (1985). A map showing the distribution of these objects on the sky can be found in Van Driel et al (1998).…”

“…A further great advantage of the GC-method is that one can easily control the sky subtraction by noting that the GC should be asymptotically flat at large radii if the background is correctly removed (Binggeli et al Notes: Column 4: BKK refers to Börngen et al (1984). Columns 5 and 6: 1950 epoch coordinates taken from the NED.…”

“…(see Appendix A). Columns 8 and 9: Diameter at µ = 25 mag/ and total apparent blue magnitude from the present photometry, from Schmidt & Boller (1992) ( 1 ), Börngen et al (1984) ( 2 ) and from other sources compiled by one of us (B. B.)…”

“…During their extensive Schmidt survey of the M 81 group, Börngen et al (1984) discovered an unusual cluster of 11 low-surface brightness objects in the SE corner of the region. Some of these objects, notably UGCA 220 and DDO 87 had been known before.…”