Testing of the dwarf galaxy content and the evolutionary status of nearby groups of galaxies

We carried out visual and parametric searches for dwarf galaxies in five loose groups of galaxies. Follow-up spectroscopy with the HET has shown a 50% success rate of morphological selection. The evolutionary status of the studied groups differs: while the NGC 6962 group has a partially relaxed core, surrounded by an infall region, the NGC 5005/5033 group and the IC 65 group, which consist only of late-type galaxies, are probably still assembling.Comment: 3 pages, 5 figures, to be published in Astronomische Nachrichten (proceedings of Symposium 6 of the JENAM 2008, Vienna

Near-infrared luminosity function and colours of dwarf galaxies in the Coma Cluster

We present K-band observations of the low-luminosity galaxies in the Coma cluster, which are responsible for the steep upturn in the optical luminosity function at M_R ~ -16, discovered recently. The main results of this study are (i) The optical$-$near-infrared colours of these galaxies imply that they are dwarf spheroidals. The median M-K colour for galaxies with -19.3 < M_K < -16.3 is 3.6 mag. (ii) The K-band luminosity function in the Coma cluster at the faint-end is not wee constrained, because of the uncertainties due to the field-to-field variance of the background. However, within the estimate large errors, it is consistent with the R-band luminosity function, shifted by $\sim3$ magnitudes. (iii) Many of the cluster dwarfs lie in a region of the B-K vs. B-R colour-colour diagram where background galaxies are rare Local dwarf spheroidal galaxies lie in this region too. This suggests that a better measurement of the K-band cluster luminosity function can be made if the field-to-field variance of the background can be measured as a function of colour. (iv) If we assume that none of the galaxies in the region of the B-K vs. B-R plane given in (iii) in our cluster fields are background, and that all the cluster galaxies with $15.5 < K < 18.5$ lie in this region of the plane, then we measure alpha = -1.41 +/- 0.35 for -19.3 < M_K < -16.3, where alpha is the logarithmic slope of the luminosity function.Comment: 6 pages, 8 figs, 2 tabs, MNRAS in press; email: [email protected], [email protected]

Modulation of human lymphocyte function by C3a and C3a(70-77).

Human C3a and the synthetic octapeptide C3a (70-77), which retains the activities of an anaphylatoxin, inhibit in a concentration-dependent manner the generation of leukocyte inhibitory factor (LIF) activity by human mononuclear leukocytes and T lymphocytes cultured with the mitogens phytohemagglutinin (PHA) or concanavalin A (Con A) or the antigen streptokinase-streptodornase (SK-SD). The generation of LIF activity was inhibited by 50% by 10(-8) M C3a or C3a(70-77) with PHA or Con A as the stimulus, whereas a more than 10-fold higher concentration of C3a(70-77) than C3a was required to achieve the same level of suppression with SK-SD as the stimulus. Similar concentrations of C3a(70-77) inhibited to the same extent the migration of T lymphocytes stimulated by alpha-thioglycerol of Con A. Neither C3a nor C3a(70-77) altered significantly the uptake of [3H]thymidine by human mononuclear cells exposed to PHA, Con A, or SK-SD. The capacity of C3a(70-77)-Sepharose,m but not Sepharose alone, to adsorb or inactivate mononuclear leukocytes required for the generation of LIF activity established a direct interaction. Analysis of the lymphocytes in the effluent from C3a(70-77)-Sepharose columns, using monoclonal antibodies to surface antigens, showed a selective depletion of the helper/inducer population of lymphocytes. C3a might represent an important mediator of the functionally selective regulation of human T lymphocyte activities by the complement system

Dwarf galaxies in the Dynamically Evolved NGC 1407 Group

The NGC 1407 Group stands out among nearby structures by its properties that suggest it is massive and evolved. It shares properties with entities that have been called fossil groups: the 1.4 magnitude differential between the dominant elliptical galaxy and the second brightest galaxy comes close to satisfying the definition that has been used to define the fossil class. There are few intermediate luminosity galaxies, but a large number of dwarfs in the group. We estimate there are 250 group members to the depth of our survey. The slope of the faint end of the luminosity function (reaching M_R = -12) is alpha = -1.35. Velocities for 35 galaxies demonstrate that this group with one dominant galaxy has a mass of 7 X 10^13 M_sun and M/L_R = 340. Two galaxies in close proximity to NGC 1407 have very large blueshifts. The most notable is the second brightest galaxy, NGC 1400, with a velocity of -1072 km/s with respect to the group mean. We report the detection of X-ray emission from this galaxy and from the group.Comment: final version to appear in MNRAS, URL for data include