Radial Velocities of Newly Discovered Globular Clusters in NGC 5128

We present radial velocity measurements for 74 globular clusters (GCs) in the nearby giant elliptical NGC 5128, of which 31 are newly discovered clusters. All the GC candidates were taken from the list of possible new clusters given in the Harris, Harris, & Geisler (2004) photometric survey. In addition to the newly confirmed clusters, we identified 24 definite foreground stars and 31 probable background galaxies. From a combined list of 299 known GCs in NGC 5128 with measured radial velocities and metallicity-sensitive (C - T_1) photometric indices, we construct a new metallicity distribution function (MDF) for the cluster system. The MDF shows an approximately bimodal form, with centroids at [Fe/H] = -1.46 and -0.53, and with nearly equal numbers of metal-poor and metal-rich clusters in the two modes. However, there are many intermediate-color clusters in the distribution, and the fainter clusters tend to have a higher proportion of red clusters. These features of the MDF may indicate a widespread age range within the cluster system as well as an intrinsically broad metallicity spread.Comment: 10 pages, 7 figures, 4 tables - accepted in Astronomical Journa

UCD Candidates in the Hydra Cluster

NGC 3311, the giant cD galaxy in the Hydra cluster (A1060), has one of the largest globular cluster systems known. We describe new Gemini GMOS (g',i') photometry of the NGC 3311 field which reveals that the red, metal-rich side of its globular cluster population extends smoothly upward into the mass range associated with the new class of Ultra-Compact Dwarfs (UCDs). We identify 29 UCD candidates with estimated masses > 6x10^6 solar masses and discuss their characteristics. This UCD-like sequence is the most well defined one yet seen, and reinforces current ideas that the high-mass end of the globular cluster sequence merges continuously into the UCD sequence, which connects in turn to the E galaxy structural sequence.Comment: 5 pages, 3 figures. Accepted for publication in ApJ Letter

Urine-reinfusion natriuresis: Evidence for potent natriuretic factors in rat urine

Urine-reinfusion natriuresis: Evidence for potent natriuretic factors in rat urine. In awake rats the entire urine output was continuously reinfused i.v. Urine-reinfusion (UR) consistently led to the appearance, within one to two hours, of massive, sustained natriuresis and diuresis, suggesting the existence of potent natriuretic factors in the urine. At the time of maximal natriuresis, mean sodium excretion rate and urine flow rate were 25 and 15 times their respective values in control rats. This “urine-reinfusion natriuresis” could be demonstrated despite treatment with desoxycorticosterone acetate, blockage of prostaglandin synthesis by indomethacin or meclofenamate, reduction of plasma urea by pretreatment with a protein-free diet, or heating the urine to 100°C. The natriuresis was not prevented by the absence of vasopressin (in Brattleboro rats) and was augmented by vasopressin infusion. In the Brattleboro rats, a marked increase in (CH2O + CNa)/GFR with only a slight rise in CH2O/GFR during UR suggests inhibition of both proximal and distal tubular reabsorption. Renal blood flow and plasma flow increased markedly during UR with a lesser rise in GFR, consistent with post-glomerular vasodilatation. Thus, the phenomenon of urine-reinfusion natriuresis suggests the presence in rat urine of potent, heat-stable natriuretic factors, whose action is largely independent of changes in mineralocorticoids, prostaglandins, urea, or vasopressin. Renal vasodilatation, with decreased sodium reabsorption at both proximal and distal nephron sites, appears to play an important role in the natriuresis.Natriurèse au cours de la réinjection d'urine: Preuve de l'existence de facteurs natriurétique et diurétique puissants dans Purine de rat. La totalité du débit urinaire a été réinjectée en continu chez des rats éveillés. La réinfusion d'urine (UR) détermine l'apparition, dans un délai d'une à deux heures, d'une natriurèse et d'une diurèse massive ce qui suggère la présence, dans l'urine, de facteurs natriurétiques puissants. Au moment de la natriurèse maximale les débits de sodium et d'urine sont égaux à 25 et 15 fois leurs valeurs respectives chez les animaux contrôles. Cette natriurèse par réinfusion d'urine peut être obtenue malgré le traitment par l'acétate de désoxycorticostérone, le blocage de la synthèse des prostaglandines par l'indométhacine, la diminution de l'urée plasmatique au moyen d'un prétraitement consistant en une alimentation sans protéines ou le chauffage de l'urine à 100° C. La natriurèse n'est pas empêchée par l'absence de vasopressine (rat Brattleboro), elle est augmentée par l'administration de vasopressine. Chez le rat Brattleboro une augmentation importante de (CH2O + CNa)/GFR avec une augmentation non significative de CH2O/GFR au cours de l'UR suggère l'inhibition de la réabsorption tubulaire proximale et distale. Les débits sanguin et plasmatique rénaux augmentent de façon importante au cours de l'UR cependant que le débit de filtration glomérulaire augmente moins, ce qui est compatible avec une vasodilatation post glomérulaire. Ainsi le phénomène de la natriurèse consécutive à la réinfusion d'urine suggère la présence, dans l'urine, d'un facteur natriurétique puissant, thermostable donc l'action est pour une grande part indépendante des modifications des minéralocorticoïdes, des prostaglandines, de l'urée et de la vasopressine. La vasodilatation rénale, qui diminue la réabsorption de sodium à la fois dans les régions proximale et distale du néphron, semble jouer un rôle important dans la natriurèse

Selection of gonadotrophin surge attenuating factor phage antibodies by bioassay

Peer reviewedPublisher PD

HST Photometry for the Halo Stars in the Leo Elliptical NGC 3377

We have used the ACS camera on HST to obtain (V,I) photometry for 57,000 red-giant stars in the halo of the Leo elliptical NGC 3377. We use this sample of stars to derive the metallicity distribution function (MDF) for its halo field stars, and comment on its chemical evolution history compared with both larger and smaller E galaxies. Our ACS/WFC field spans a radial range extending from 4 to 18 kpc projected distance from the center of NGC 3377 and thus covers a significant portion of this galaxy's halo. We find that the MDF is broad, reaching a peak at [m/H] ~ -0.6$, but containing virtually no stars more metal-poor than log [m/H] = -1.5$. It may, in addition, have relatively few stars more metal-rich than [m/H] = -0.3$, although interpretation of the high-metallicity end of the MDF is limited by photometric completeness that affects the detection of the reddest, most metal-rich stars. NGC 3377 appears to have an enrichment history intermediate between those of normal dwarf ellipticals and the much larger giants. As yet, we find no clear evidence that the halo of NGC 3377 contains a significant population of ``young'' (< 3 Gy) stars.Comment: 40 pages, 17 figure