Jorge Melnick

Learn More
We present a study of the stellar populations in the central ∼ 200 pc of a large and homogeneous sample comprising 79 nearby galaxies, most of which are type 2 Seyferts. The star-formation history of these nuclei is reconstructed by means of state-of-the art population synthesis modeling of their spectra in the 3500–5200 Å interval. A QSO-like featureless(More)
Our recent determination of a Salpeter slope for the IMF in the field of 30 Doradus (Selman and Melnick 2005) appears to be in conflict with simple probabilistic counting arguments advanced in the past to support observational claims of a steeper IMF in the LMC field. In this paper we re-examine these arguments and show by explicit construction that,(More)
UBV profile fitting photometry is presented for 1469 stars within 90′′ of the center of the ionizing cluster of 30 Doradus (NGC 2070). A value of 0.82 ± 0.03 is found for the extinction parameter S = E(U-B)/E(B-V), constant over almost the whole area covered by this research, with some evidence for local variations. Two reddening components can be(More)
A new method is presented and used to determine the IMF of the starburst cluster NGC2070. A new correction, the magnitude-limit correction is introduced, and shown to be crucial when attempting to derive the IMF in the presence of variable reddening when the photometry is not several magnitudes deeper than the fainter stars analyzed. Failure to apply this(More)
  • M Plionis, R Terlevich, +4 authors I Georgantopoulos
  • 2009
We propose to use alternative cosmic tracers to measure the dark energy equation of state and the matter content of the Universe [w(z) & Ωm]. Our proposed method consists of two components: (a) tracing the Hubble relation using HII-like starburst galaxies, as an alternative to supernovae type Ia, which can be detected up to very large redshifts, z ∼ 4, and(More)
This is the third paper of a series devoted to the study of the global properties of Joguet’s sample of 79 nearby galaxies observable from the southern hemisphere, of which 65 are Seyfert 2 galaxies. We use the population synthesis models of Paper II to derive ‘pure’ emission-line spectra for the Seyfert 2’s in the sample, and thus explore the statistical(More)
We re-investigated the use of the Hubble diagram to measure the cosmological constant (Λ) and the mass density of the Universe (ΩM ). We find an important focusing effect in Λ for redshifts about 3. This effect implies that the apparent magnitude of a standard candle at redshifts z=2-3 has almost no dependence on Λ for ΩM > 0.2. This means that ΩM can be(More)