arXiv subjects

A. Nigoche-Netro

Publications and source records attributed to A. Nigoche-Netro.

25 records · Page 2Linked to original sources

arXiv2012

Gemini GMOS--IFU spectroscopy of the compact HII galaxies Tol 0104-388 and Tol 2146-391: The dependence on the properties of the interstellar medium

Using GMOS--IFU spectroscopic observations of the compact HII/BCD galaxies Tol 0104-388 and Tol 2146-391, we study the spatial distribution of emission lines, equivalent width EW(Hb), extinction c(Hb), ionization ratios ([OIII]5007/Hb, [SII]6717,6731/Ha and [NII]6584/Ha), kinematics, and the chemical pattern (O/H, N/H and N/O) of the warm interstellar medium in these galaxies. We also investigate a possible dependence of these properties on the I(HeII4686)/I(Hb) ratio and find no significant correlation between these variables. In fact, the oxygen abundances appear to be uniform in the regions where the HeII4686 emission line was measured. It can be interpreted in the sense that these correlations are related to global properties of the galaxies and not with small patches of the interstellar medium. Although a possible weak N/H gradient is observed in Tol 2146-391, the available data suggest that the metals from previous star-formation events are well mixed and homogeneously distributed through the optical extent of these galaxies. The spatial constancy of the N/O ratio might be attributed to efficient transport and mixing of metals by starburst-driven super-shells, powered by a plethora of unresolved star cluster in the inner part of the galaxies. This scenario agrees with the idea that most of the observed HeII4686 emission line, in our sample of galaxies, is produced by radiative shocks.

astro-ph.CO↗

arXiv2011

Diffracto-Astrometry measurements: accuracy of the measuring algorithm

We present a theoretical analysis of the measuring algorithm we use when applying the Diffracto-Astrometry technique to Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) saturated stellar images. Theoretical Point Spread Functions (PSFs) were generated using the Tiny Tim software for the four CCDs in the WFPC2 and for some of the available filters. These images were then measured with our Diffracto-Astrometry measuring algorithm using only their diffraction pattern, and positions for the simulated PSFs on each generated CCD-frame were obtained. The measuring algorithm recovers the original positions reasonably well ($\pm 0.1\ \rm{to} \ \pm 0.4$ pixels). However, slight deviations from the original values are observed. These also vary with position over the entire surface of the CCD. We adjust the difference between the real and the measured position with a quadratic function of the coordinates. The transformation coefficients also present a slight correlation with the filter effective wavelength. Application of these transformation coefficients allows us to determine the position of a stellar image with a precision of a few hundredths of a pixel.

astro-ph.IM↗

arXiv2011

Star Cluster Complexes and the Host Galaxy in Three HII Galaxies: Mrk 36, UM 408, and UM 461

We present a stellar population study of three HII galaxies (Mrk 36, UM 408, and UM 461) based on the analysis of new ground-based high resolution near-infrared J, H and Kp broad-band and Br narrow-band images obtained with Gemini/NIRI. We identify and determine relative ages and masses of the elementary star clusters and/or star cluster complexes of the starburst regions in each of these galaxies by comparing the colors with evolutionary synthesis models that include the contribution of stellar continuum, nebular continuum and emission lines. We found that the current star cluster formation efficiency in our sample of low luminosity HII galaxies is ~10%. Therefore, most of the recent star formation is not in massive clusters. Our findings seem to indicate that the star formation mode in our sample of galaxies is clumpy, and that these complexes are formed by a few massive star clusters with masses > 10^4 Mo. The age distribution of these star cluster complexes shows that the current burst started recently and likely simultaneously over short time scales in their host galaxies, triggered by some internal mechanism. Finally, the fraction of the total cluster mass with respect to the low surface brightness (or host galaxy) mass, considering our complete range in ages, is less than 1%.

astro-ph.CO↗

arXiv2011

The intrinsic dispersion of the Faber-Jackson relation for early-type galaxies as function of the mass and redshift

Aims. Recently it has been reported that the intrinsic dispersion at constant magnitude of the structural relations from early-type galaxies is a useful tool to study the universality of these structural relations, that is to say, to study whether the structural relations depend on luminosity, wavelength, redshift and/or environment. In this work we study the intrinsic dispersion of the Faber-Jackson relation as function of the luminosity, mass and redshift. Methods. We use a sample of approximately 90 000 early-type galaxies from the Sloan Digital Sky Survey (SDSS-DR7) spanning a magnitude range of 7 $mag$ in both $g$ and $r$ filters. We calculate the intrinsic dispersion of the Faber-Jackson relation at approximately constant magnitude and compare this at different luminosities, masses and redshifts. Results. The main results are the following: i) The intrinsic dispersion of the Faber-Jackson relation depends on the luminosity, mass and redshift. ii) The distribution for brighter and more massive galaxies has smaller intrinsic dispersion than that for fainter and less massive galaxies. iii) The distribution of bright and massive galaxies at higher redshift has smaller intrinsic dispersion than those similar galaxies at low redshift. Conclusions. Comparisons of the results found in this work with recent studies from the literature make us conclude that the intrinsic dispersion of the Faber-Jackson relation could depend on the history of galaxies, in other words, the intrinsic dispersion could depend on the number and nature of transformation events that have affected the galaxies along their life times, such as collapse, accretion, interaction and merging.

astro-ph.CO↗

arXiv2010

The Faber-Jackson relation for early-type galaxies: Dependence on the magnitude range

We take a sample of early-type galaxies from the Sloan Digital Sky Survey (SDSS-DR7, $\sim$ 90 000 galaxies) spanning a range of approximately 7 $mag$ in both $g$ and $r$ filters and analyse the behaviour of the Faber-Jackson relation parameters as functions of the magnitude range. We calculate the parameters in two ways: i) We consider the faintest (brightest) galaxies in each sample and we progressively increase the width of the magnitude interval by inclusion of the brighter (fainter) galaxies (increasing-magnitude-intervals), and ii) we consider narrow-magnitude intervals of the same width ($ΔM = 1.0$ $mag$) over the whole magnitude range available (narrow-magnitude-intervals). Our main results are that: i) in both increasing and narrow-magnitude-intervals the Faber-Jackson relation parameters change systematically, ii) non-parametric tests show that the fluctuations in the values of the slope of the Faber-Jackson relation are not products of chance variations. We conclude that the values of the Faber-Jackson relation parameters depend on the width of the magnitude range and the luminosity of galaxies within the magnitude range. This dependence is caused, to a great extent by the selection effects and because the geometrical shape of the distribution of galaxies on the $M - \log (σ_{0})$ plane depends on luminosity. We therefore emphasize that if the luminosity of galaxies or the width of the magnitude range or both are not taken into consideration when comparing the structural relations of galaxy samples for different wavelengths, environments, redshifts and luminosities, any differences found may be misinterpreted.

astro-ph.CO↗

arXiv2008

The Fundamental Plane for early-type galaxies. Dependence on the magnitude range

Studying 3 samples of early-type galaxies, which include approximately 8800 galaxies and cover a relatively ample magnitude range ($<ΔM>$ $\sim 5$ $mag$), we find that the coefficients as well as the intrinsic dispersion of the Fundamental Plane depend on the width of the magnitude range within which the galaxies are distributed. We analyse this dependence and the results show that it could be due to the fact that the distribution of galaxies in the space defined by the variables $\log (r_{e}), <μ>_{e}, \log(σ)$ depends on the luminosity.

astro-ph↗

arXiv2008

The Kormendy Relation for early-type galaxies. Dependence on the magnitude range

Previous studies indicate that faint and bright early-type galaxies (ETGs) present different coefficients and dispersion for their Kormendy relation (KR). A recently published paper states that the intrinsic dispersion of the KR depends on the magnitude range within which the galaxies are contained, therefore, we investigate here whether the magnitude range has also an influence over the values of the coefficients of the KR; $α$ (zero point) and $β$ (slope). We perform numerical simulations and analysis of these coefficients for 4 samples of galaxies, which contain an approximate total of 9400 ETGs in a relatively ample magnitude range ($<ΔM>$ $\sim 6 mag$). The analysis of the results makes us conclude that the values of the KR coefficients depend on the width of the magnitude range and the brightness of galaxies within the magnitude range. This dependence is due to the fact that the distribution of galaxies in the $\log (r_{e}) - <μ>_{e}$ plane depends on luminosity and that this distribution is not symmetrical, that is, the geometric shape of the distribution of galaxies in the $\log (r_{e}) - <μ>_{e}$ plane plays an important role in the determination of the values of the coefficients of the KR.

astro-ph↗