Andrea V. Ahumada

Optical Light Curve of the Type Ia Supernova 1998bu in M96 and the Supernova Calibration of the Hubble Constant

We present the UBV(RI)KC light curves of the Type Ia supernova SN 1998bu, which appeared in the nearby galaxy M96 (NGC 3368). M96 is a spiral galaxy in the Leo I group that has a Cepheid-based distance. Our photometry allows us to calculate the absolute magnitude and reddening of this supernova. These data, when combined with measurements of the four other well-observed supernovae with Cepheid-based distances, allow us to calculate the Hubble constant with respect to the Hubble flow defined by the distant Calan/Tololo Type Ia sample. We find a Hubble constant of 63.9 ± 2.2(internal) ± 3.5(external) km s-1 Mpc-1, consistent with most previous estimates based on Type Ia supernovae. We note that the two well-observed Type Ia supernovae in Fornax, if placed at the Cepheid distance to the possible Fornax spiral NGC 1365, are apparently too faint with respect to the Calan/Tololo sample calibrated with the five Type Ia supernovae with Cepheid distances to the host galaxies.

Background galaxies as reddening probes throughout the Magellanic Clouds

We study the spectral properties in the range 3600 A-6800 A of the nuclear region of galaxies behind the Magellanic Clouds. The radial velocities clarified the nature of the objects as background galaxies or extended objects belonging to the Clouds. For most galaxies behind the main bodies of the LMC and SMC, radial velocities were measured for the first time. In the present sample typical LMC background galaxies are nearby (

On the calibration of the COBE/IRAS dust emission reddening maps

4000 < V({\rm km s^{-1}}) < 6000

The relatively young, metal-poor and distant open cluster NGC 2324

), while SMCs are considerably more distant (

Dating star clusters in the Small Magellanic Cloud by means of integrated spectra

10 000 < V({\rm km s^{-1}}) < 20 000

Reddening and age for 13 southern Galactic open clusters determined from integrated spectra

). We determine the reddening in each line of sight by matching a reddening-free galaxy template with comparable stellar population. For the LMC main body we derive a combined Milky Way and internal reddening value

Spectral evolution of star clusters in the Large Magellanic Cloud. I. Blue concentrated clusters in the age range 40-300 Myr

E(B-V)_{\rm MW+i} = 0.12 \pm 0.10

Ruprecht 3: An old star cluster remnant?

, while for the SMC

Integrated spectral properties of 22 small angular diameter galactic open clusters

E(B-V)_{\rm MW+i} = 0.05 \pm 0.05

A sample of relatively unstudied star clusters in the Large Magellanic Cloud: fundamental parameters determined from Washington photometry

. By subtracting Milky Way reddening values for galaxies projected onto the surroundings of each Cloud, we estimate average internal reddening values