Vasiliki Petropoulou

Instituto De Astrofisica De Andalucia, Granata, Andalusia, Spain

Are you Vasiliki Petropoulou?

Claim your profile

Publications (8)29.04 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent results are presented on the metal enrichment of low-mass star-forming (SF) galaxies in local Universe clusters. The environmental effects on the chemical evolution of these galaxies are discussed. We have used spectroscopic data from the SDSSIII-DR8 and we have derived the gas-phase O/H and N/O abundances. We have then examined the Mass-Metallicity Relation (MZR) of this sample of cluster galaxies, and we have found well defined sequences. A flattening of the slope of these sequences has been observed for galaxies located in the core of the two more massive clusters of the sample, suggesting that the effect of the cluster environment depends both on the galaxy mass and the host cluster mass. Based on these results we explore cluster-specific effects (e.g. ram-pressure stripping, pressure confinement etc), predicted by hydrodynamic models, capable of yielding the observed mass-dependent enhancement of the metallicity.
    11/2012;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Galaxy clusters are key places to study the contribution of {\it nature} (i.e. mass, morphology) and {\it nurture} (i.e.environment) in the formation and evolution of galaxies. Recently, a number of clusters at z$>$1, i.e. corresponding to the first epochs of the cluster formation, has been discovered and confirmed spectroscopically. We present new observations obtained with the {\sc LUCIFER} spectrograph at Large Binocular Telescope (LBT) of a sample of star-forming galaxies associated with a large scale structure around the radio galaxy 7C1756+6520 at z=1.42. Combining our spectroscopic data and the literature photometric data, we derived some of the properties of these galaxies: star formation rate, metallicity and stellar mass. With the aim of analyzing the effect of the cluster environment on galaxy evolution, we have located the galaxies in the plane of the so-called Fundamental Metallically Relation (FMR), which is known not to evolve with redshift up to z$=2.5$ for field galaxies, but it is still unexplored in rich environments at low and high redshift. We found that the properties of the galaxies in the cluster 7C 1756+6520 are compatible with the FMR which suggests that the effect of the environment on galaxy metallicity at this early epoch of cluster formation is marginal. As a side study, we also report the spectroscopic analysis of a bright AGN, belonging to the cluster, which shows a significant outflow of gas.
    Monthly Notices of the Royal Astronomical Society 06/2012; 426(2). · 5.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper we study the chemical history of low-mass star-forming (SF) galaxies in the local Universe clusters Coma, A1367, A779, and A634. The aim of this work is to search for the imprint of the environment on the chemical evolution of these galaxies. Galaxy chemical evolution is linked to the star formation history (SFH), as well as to the gas interchange with the environment, and low-mass galaxies are well known to be vulnerable systems to environmental processes affecting both these parameters. For our study we have used spectra from the SDSS-III DR8. We have examined the mass-metallicity relation of cluster galaxies finding well defined sequences. The slope of these sequences, for galaxies in low-mass clusters and galaxies at large cluster-centric distances, follows the predictions of recent hydrodynamic models. A flattening of this slope has been observed for galaxies located in the core of the two more massive clusters of the sample, principally in Coma, suggesting that the imprint of the cluster environment on the chemical evolution of SF galaxies should be sensitive to both the galaxy mass and the host cluster mass. The HI gas content of Coma and A1367 galaxies indicate that low-mass SF galaxies, located at the core of these clusters, have been severely affected by ram-pressure stripping. The observed mass-dependent enhancement of the metal content of low-mass galaxies in dense environments seems plausible, according to hydrodynamic simulations. This enhanced metal enrichment could be produced by the combination of effects such as wind reaccretion, due to pressure cofinement by the intra-cluster medium (ICM), and the truncation of gas infall, as a result of the ram-pressure stripping. Thus, the properties of the ICM should play an important role in the chemical evolution of low-mass galaxies in clusters.
    The Astrophysical Journal 02/2012; 749(2). · 6.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We carried out IFU optical spectroscopy on three pointings in and near the SQ shock. We used PMAS on the 3.5m Calar Alto telescope to obtain measures of emission lines that provide insight into physical properties of the gas. Severe blending of H\alpha\ and [NII]6548,6583A emission lines in many spaxels required the assumption of at least two kinematical components in order to extract fluxes for the individual lines. Main results from our study include: (a) detection of discrete emission features in the new intruder velocity range 5400-6000km/s showing properties consistent with HII regions, (b) detection of a low velocity component spanning the range 5800-6300km/s with properties resembling a solar metallicity shocked gas and (c) detection of a high velocity component at ~6600km/s with properties consistent with those of a low metallicity shocked gas. The two shocked components are interpreted as products of a collision between NGC7318b new intruder and a debris field in its path. This has given rise to a complex structure of ionized gas where several components with different kinematical and physical properties coexist although part of the original ISM associated with NGC7318b is still present and remains unaltered. Our observations suggest that the low velocity ionized component might have existed before the new intruder collision and could be associated with the NW-LV HI component of Williams et al. (2002). The high velocity ionized component might fill the gap between the HI complexes observed in SQ-A and NGC7319's tidal filament (NW-HV, Arc-N and Arc-S in Williams et al. 2002).
    Astronomy and Astrophysics 01/2012; · 5.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The star formation history, gas-content and the mass interchange with the environment (infall of metal-poor gas and/or outflow of enriched material) are the fundamental variables controlling the chemical evolution of a galaxy. Observational hints which constrain the galaxy evolution scenarios in dense environments have lately started to be investigated (Mouhcine et al. 2007, Ellison et al. 2009, Cooper et al. 2008). In this work we study the relation between metallicity and environment for a sample of star-forming galaxies in the Hercules cluster. Spatially resolved spectroscopy has been obtained for 28 galaxies selected from our deep Hα survey of the Hercules cluster. We apply spectral synthesis models to all our emission-line spectra using the evolutionary code STARLIGHT and we obtain fundamental parameters of the underlying stellar component, as the mean metallicity and age. By the emission-line spectra corrected from the stellar population continuum we derive gas chemical abundances using empirical strong-line calibrations. We calculate galaxies' physical properties as masses and total luminosities using SDSS broadband photometry. All the information obtained has provided us with new observable imprints of the cluster environment effect on the chemical evolution of galaxies and the mass-metallicity relation.
    10/2011; -1:396-396.
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work we study the effects of the Hercules cluster environment on the chemical history of star-forming (SF) galaxies. For this purpose we have derived the gas metallicities, the mean stellar metallicities and ages, the masses and the luminosities of our sample of galaxies. We have found that our Hercules SF galaxies are either chemically evolved spirals with nearly flat oxygen gradients, or less metal-rich dwarf galaxies which appear to be the “newcomers” in the cluster. Most Hercules SF galaxies follow well defined mass-metallicity and luminosity-metallicity sequences; nevertheless significant outliers to these relations have been identified, illustrating how environmental effects can provide a physical source of dispersion in these fundamental relations.
    07/2011: pages 65-67;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Spatially resolved spectroscopy has been obtained for a sample of 27 star-forming (SF) galaxies selected from our deep Halpha survey of the Hercules cluster. We have applied spectral synthesis models to all emission-line spectra of this sample using the population synthesis code STARLIGHT. We have obtained fundamental parameters of the stellar components, as the mean metallicity and age, and we have corrected the emission-line spectra for underlying stellar absorption. O/H and N/O gas chemical abundances were obtained using the latest empirical calibrations. The effects of cluster environment on the chemical evolution of galaxies and on their mass-metallicity (MZ) and luminosity-metallicity (LZ) relations were studied combining the derived gas metallicities, the mean stellar metallicities and ages, the masses and luminosities of galaxies and their existing HI data. We have found that our Hercules SF galaxies divide into three main subgroups: a) chemically evolved spirals with truncated ionized-gas disks and nearly flat oxygen gradients, witnessing the effect of ram-pressure stripping, b) chemically evolved dwarfs/irregulars populating the highest local densities, possible products of tidal interactions in preprocessing events, or c) less metallic dwarf galaxies which appear to be "newcomers" to the cluster, experiencing pressure-triggered star-formation. Most Hercules SF galaxies follow well defined MZ and LZ sequences (for both O/H and N/O); though the dwarf/irregular galaxies located at the densest regions appear to be outliers to these global relations, suggesting a physical reason for the dispersion in these fundamental relations. The Hercules cluster appears to be currently assembling via the merger of smaller substructures, providing an ideal laboratory where the local environment has been found to be a key parameter to understand the chemical history of galaxies.
    The Astrophysical Journal 04/2011; 734. · 6.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the first results of an H imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in H, from which 41 were classified as secure members of the cluster and 2 as likely members based on spectroscopic and photometric redshift considerations. The remaining seven galaxies were classified as background contaminants and thus excluded from our study on the H properties of the cluster. The morphologies of the 43 H selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalactic H II regions, spanning a range of magnitudes of -21 {
    The Astronomical Journal 09/2009; 138(3):873-888. · 4.97 Impact Factor