An upper mass limit for the progenitor of the TypeII-P supernova SN1999gi

Masses and progenitor evolutionary states of TypeII supernovae remain almost unconstrained by direct observations. Only one robust observation of a progenitor (SN1987A) and one plausible observation (SN1993J) are available. Neither matched theoretical predictions and in this Letter we report limits on a third progenitor (SN1999gi). The Hubble Space Telescope has imaged the site of the TypeII-P supernova SN1999gi with the WFPC2 in two filters (F606W and F300W) prior to explosion. The distance to the host galaxy (NGC3184) of 7.9Mpc means that the most luminous, massive stars are resolved as single objects in the archive images. The supernova occurred in a resolved, young OB association 2.3kpc from the centre of NGC3184 with an association age of about 4Myrs. Follow-up images of SN1999gi with WFPC2 taken 14 months after discovery determine the precise position of the SN on the pre-explosion frames. An upper limit of the absolute magnitude of the progenitor is estimated (M_v >= -5.1). By comparison with stellar evolutionary tracks this can be interpreted as a stellar mass, and we determine an upper mass limit of 9(+3/-2)M_solar. We discuss the possibility of determining the masses or mass limits for numerous nearby core-collapse supernovae using the HST archive enhanced by our current SNAP programme.Comment: To appear in ApJ Letters, 16 pages, 3 figure

Evidence for tidal interaction and merger as the origin of galaxy morphology evolution in compact groups

We present the results of a morphological study based on NIR images of 25 galaxies, with different levels of nuclear activity, in 8 Compact Groups of Galaxies (CGs). We perform independently two different analysis: a isophotal study and a study of morphological asymmetries. The results yielded by the two analysis are highly consistent. For the first time, it is possible to show that deviations from pure ellipses are produced by inhomogeneous stellar mass distributions related to galaxy interactions and mergers. We find evidence of mass asymmetries in 74% of the galaxies in our sample. In 59% of these cases, the asymmetries come in pairs, and are consistent with tidal effects produced by the proximity of companion galaxies. The symmetric galaxies are generally small in size or mass, inactive, and have an early-type morphology. In 20% of the galaxies we find evidence for cannibalism. In 36% of the early-type galaxies the color gradient is positive (blue nucleus) or flat. Summing up these results, as much as 52% of the galaxies in our sample could show evidence of an on going or past mergers. Our observations suggest that galaxies in CGs merge more frequently under ``dry'' conditions. The high frequency of interacting and merging galaxies observed in our study is consistent with the bias of our sample towards CGs of type B, which represents the most active phase in the evolution of the groups. In these groups we also find a strong correlation between asymmetries and nuclear activity in early-type galaxies. This correlation allows us to identify tidal interactions and mergers as the cause of galaxy morphology transformation in CGs.[abridge]Comment: 64 pages, 35 figures. Accepted for publication in Ap

Astroclimatic Characterization of Vallecitos: A candidate site for the Cherenkov Telescope Array at San Pedro Martir

We conducted an 18 month long study of the weather conditions of the Vallecitos, a proposed site in Mexico to harbor the northern array of the Cherenkov Telescope Array (CTA). It is located in Sierra de San Pedro Martir (SPM) a few kilometers away from Observatorio Astron\'omico Nacional. The study is based on data collected by the ATMOSCOPE, a multi-sensor instrument measuring the weather and sky conditions, which was commissioned and built by the CTA Consortium. Additionally, we compare the weather conditions of the optical observatory at SPM to the Vallecitos regarding temperature, humidity, and wind distributions. It appears that the excellent conditions at the optical observatory benefit from the presence of microclimate established in the Vallecitos.Comment: 16 pages, 16 figures, Publication of the Astronomical Society of the Pacific, accepte

Effect of beta-adrenergic stimulation on whole-body and abdominal subcutaneous adipose tissue lipolysis in lean and obese men

AIMS/HYPOTHESIS: Obesity is characterised by increased triacylglycerol storage in adipose tissue. There is in vitro evidence for a blunted beta-adrenergically mediated lipolytic response in abdominal subcutaneous adipose tissue (SAT) of obese individuals and evidence for this at the whole-body level in vivo. We hypothesised that the beta-adrenergically mediated effect on lipolysis in abdominal SAT is also impaired in vivo in obese humans. METHODS: We investigated whole-body and abdominal SAT glycerol metabolism in vivo during 3 h and 6 h [2H5]glycerol infusions. Arterio-venous concentration differences were measured in 13 lean and ten obese men after an overnight fast and during intravenous infusion of the non-selective beta-adrenergic agonist isoprenaline [20 ng (kg fat free mass)(-1) min(-1)]. RESULTS: Lean and obese participants showed comparable fasting glycerol uptake by SAT (9.7+/-3.4 vs 9.3+/-2.5% of total release, p=0.92). Furthermore, obese participants showed an increased whole-body beta-adrenergically mediated lipolytic response versus lean participants. However, their fasting lipolysis was blunted [glycerol rate of appearance: 7.3+/-0.6 vs 13.1+/-0.9 micromol (kg fat mass)(-1) min(-1), p<0.01], as was the beta-adrenergically mediated lipolytic response per unit SAT [Delta total glycerol release: 140+/-71 vs 394+/-112 nmol (100 g tissue)(-1) min(-1), p<0.05] compared with lean participants. Net triacylglycerol flux tended to increase in obese compared with lean participants during beta-adrenergic stimulation [Delta net triacylglycerol flux: 75+/-32 vs 16+/-11 nmol (100 g tissue)(-1) min(-1), p=0.06]. CONCLUSIONS/INTERPRETATION: We demonstrated in vivo that beta-adrenergically mediated lipolytic response is impaired systematically and in abdominal SAT of obese versus lean men. This may be important in the development or maintenance of increased triacylglycerol stores and obesity

What makes a galaxy radio-loud?

We compare the Spectral Energy Distribution (SED) of radio-loud and radio-quiet AGNs in three different samples observed with SDSS: radio-loud AGNs (RLAGNs), Low Luminosity AGNs (LLAGNs) and AGNs in isolated galaxies (IG-AGNs). All these galaxies have similar optical spectral characteristics. The median SED of the RLAGNs is consistent with the characteristic SED of quasars, while that of the LLAGNs and IG-AGNs are consistent with the SED of LINERs, with a lower luminosity in the IG-AGNs than in the LLAGNs. We infer the masses of the black holes (BHs) from the bulge masses. These increase from the IG-AGNs to the LLAGNs and are highest for the RLAGNs. All these AGNs show accretion rates near or slightly below 10% of the Eddington limit, the differences in luminosity being solely due to different BH masses. Our results suggests there are two types of AGNs, radio quiet and radio loud, differing only by the mass of their bulges or BHs.Comment: 3 pages, 3 figures; to appear in Proceedings of IAU Symposium No. 284, The Spectral Energy Distribution of Galaxies (SED2011), Preston, UK, 5-9 sep. 201