Proceedings of the International Astronomical Union, 2014
ABSTRACT We investigate the environmental dependence of the mass-metallicty (MZ) relation and it&... more ABSTRACT We investigate the environmental dependence of the mass-metallicty (MZ) relation and it's connection to galaxy stellar structures and morphologies. In our studies, we analyze galaxies in massive clusters at z~0.4 from the CLASH (HST) and CLASH-VLT surveys and measure their gas metallicities, star-formation rates, stellar structures and morphologies. We establish the MZ relation for 90 cluster and 40 field galaxies finding a shift of ~-0.3 dex in comparison to the local trends seen in SDSS for the majority of galaxies with logM<10.5. We do not find significant differences of the distribution of 4 distinct morphological types that we introduce by our classification scheme (smooth, disc-like, peculiar, compact). Some variations between cluster and field galaxies in the MZ relation are visible at the high mass end. However, obvious trends for cluster specific interactions (enhancements or quenching of SFRs) are missing. In particular, galaxies with peculiar stellar structures that hold signs for galaxy interactions, are distributed in a similar way as disc-like galaxies - in SFRs, masses and O/H abundances. We further show that our sample falls around an extrapolation of the star-forming main sequence (the SFR-M* relation) at this redshift, indicating that emission-line selected samples do not have preferentially high star-formation rates (SFRs). However, we find that half of the high mass cluster members (M*>10^10Msun) lie below the main sequence which corresponds to the higher mass objects that reach solar abundances in the MZ diagram.
ABSTRACT In the local universe, there is good evidence that, at a given stellar mass M, the gas-p... more ABSTRACT In the local universe, there is good evidence that, at a given stellar mass M, the gas-phase metallicity Z is anti-correlated with the star formation rate (SFR) of the galaxies. It has also been claimed that the resulting Z(M, SFR) relation is invariant with redshift—the so-called "fundamental metallicity relation" (FMR). Given a number of difficulties in determining metallicities, especially at higher redshifts, the form of the Z(M, SFR) relation and whether it is really independent of redshift is still very controversial. To explore this issue at z > 2, we used VLT-SINFONI and Subaru-MOIRCS near-infrared spectroscopy of 20 zCOSMOS-deep galaxies at 2.1 < z < 2.5 to measure the strengths of up to five emission lines: [O II] λ3727, Hβ, [O III] λ5007, Hα, and [N II] λ6584. This near-infrared spectroscopy enables us to derive O/H metallicities, and also SFRs from extinction corrected Hα measurements. We find that the mass-metallicity relation (MZR) of these star-forming galaxies at z 2.3 is lower than the local Sloan Digital Sky Survey (SDSS) MZR by a factor of three to five, a larger change than found by Erb et al. using [N II]/Hα-based metallicities from stacked spectra. We discuss how the different selections of the samples and metallicity calibrations used may be responsible for this discrepancy. The galaxies show direct evidence that the SFR is still a second parameter in the MZR at these redshifts. However, determining whether the Z(M, SFR) relation is invariant with epoch depends on the choice of extrapolation used from local samples, because z > 2 galaxies of a given mass have much higher SFRs than the local SDSS galaxies. We find that the zCOSMOS galaxies are consistent with a non-evolving FMR if we use the physically motivated formulation of the Z(M, SFR) relation from Lilly et al., but not if we use the empirical formulation of Mannucci et al.
In order to try to understand the internal evolution of galaxies and relate this to the global ev... more In order to try to understand the internal evolution of galaxies and relate this to the global evolution of the galaxy population, we present a comparative study of the dependence of star formation rates on the average surface mass densities (Σ M) of galaxies at 0.5< z< 0.9 and 0.04< z< 0.08, using the zCOSMOS and Sloan Digital Sky Survey (SDSS) surveys, respectively.
Proceedings of the International Astronomical Union, 2014
ABSTRACT A relation between the stellar mass M and the gas-phase metallicity Z of galaxies, the M... more ABSTRACT A relation between the stellar mass M and the gas-phase metallicity Z of galaxies, the MZR, is observed up to higher redshifts. It is a matter of debate, however, if the SFR is a second parameter in the MZR. To explore this issue at z &gt; 1, we used VLT-SINFONI near-infrared (NIR) spectroscopy of eight zCOSMOS galaxies at 1.3 &lt; z &lt; 1.4 to measure the strengths of four emission lines: Hbeta, [OIII]lambda5007, Halpha, and [NII]lambda6584, additional to [OII]lambda3727 measured from VIMOS. We derive reliable O/H metallicities based on five lines, and also SFRs from extinction corrected Halpha measurements. We find that the MZR of these star-forming galaxies at z~1.4 is lower than the local SDSS MZR by a factor of three to five, a larger change than reported in the literature using [NII]/Halpha-based metallicities from individual and stacked spectra. Correcting N2-based O/Hs using recent results by Newman et al. (2014), also the larger FMOS sample at z~1.4 of Zahid et al. (2014) shows a similar evolution of the MZR like the zCOSMOS objects. These observations seem also in agreement with a non-evolving FMR using the physically motivated formulation of the FMR from Lilly et al. (2013).
The Calar Alto Deep Imaging Survey (CADIS) [5] combines a deep emission line survey employing an ... more The Calar Alto Deep Imaging Survey (CADIS) [5] combines a deep emission line survey employing an imaging Fabry-Perot-Interferometer ( F lim= 3 x 10-20 Wm-2) with a moderately deep multi-band survey ( 400 &amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;=lambda &amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;=2300nm, Rlim~= 24). One of its major goals is the search for Ly-alpha galaxies in three redshift windows around z ~= 4.8, 5.7 and 6.6. Six
Proceedings of the International Astronomical Union, 2014
ABSTRACT We investigate the environmental dependence of the mass-metallicty (MZ) relation and it&... more ABSTRACT We investigate the environmental dependence of the mass-metallicty (MZ) relation and it&amp;amp;amp;amp;#39;s connection to galaxy stellar structures and morphologies. In our studies, we analyze galaxies in massive clusters at z~0.4 from the CLASH (HST) and CLASH-VLT surveys and measure their gas metallicities, star-formation rates, stellar structures and morphologies. We establish the MZ relation for 90 cluster and 40 field galaxies finding a shift of ~-0.3 dex in comparison to the local trends seen in SDSS for the majority of galaxies with logM&amp;amp;amp;amp;lt;10.5. We do not find significant differences of the distribution of 4 distinct morphological types that we introduce by our classification scheme (smooth, disc-like, peculiar, compact). Some variations between cluster and field galaxies in the MZ relation are visible at the high mass end. However, obvious trends for cluster specific interactions (enhancements or quenching of SFRs) are missing. In particular, galaxies with peculiar stellar structures that hold signs for galaxy interactions, are distributed in a similar way as disc-like galaxies - in SFRs, masses and O/H abundances. We further show that our sample falls around an extrapolation of the star-forming main sequence (the SFR-M* relation) at this redshift, indicating that emission-line selected samples do not have preferentially high star-formation rates (SFRs). However, we find that half of the high mass cluster members (M*&amp;amp;amp;amp;gt;10^10Msun) lie below the main sequence which corresponds to the higher mass objects that reach solar abundances in the MZ diagram.
ABSTRACT In the local universe, there is good evidence that, at a given stellar mass M, the gas-p... more ABSTRACT In the local universe, there is good evidence that, at a given stellar mass M, the gas-phase metallicity Z is anti-correlated with the star formation rate (SFR) of the galaxies. It has also been claimed that the resulting Z(M, SFR) relation is invariant with redshift—the so-called &quot;fundamental metallicity relation&quot; (FMR). Given a number of difficulties in determining metallicities, especially at higher redshifts, the form of the Z(M, SFR) relation and whether it is really independent of redshift is still very controversial. To explore this issue at z &gt; 2, we used VLT-SINFONI and Subaru-MOIRCS near-infrared spectroscopy of 20 zCOSMOS-deep galaxies at 2.1 &lt; z &lt; 2.5 to measure the strengths of up to five emission lines: [O II] λ3727, Hβ, [O III] λ5007, Hα, and [N II] λ6584. This near-infrared spectroscopy enables us to derive O/H metallicities, and also SFRs from extinction corrected Hα measurements. We find that the mass-metallicity relation (MZR) of these star-forming galaxies at z 2.3 is lower than the local Sloan Digital Sky Survey (SDSS) MZR by a factor of three to five, a larger change than found by Erb et al. using [N II]/Hα-based metallicities from stacked spectra. We discuss how the different selections of the samples and metallicity calibrations used may be responsible for this discrepancy. The galaxies show direct evidence that the SFR is still a second parameter in the MZR at these redshifts. However, determining whether the Z(M, SFR) relation is invariant with epoch depends on the choice of extrapolation used from local samples, because z &gt; 2 galaxies of a given mass have much higher SFRs than the local SDSS galaxies. We find that the zCOSMOS galaxies are consistent with a non-evolving FMR if we use the physically motivated formulation of the Z(M, SFR) relation from Lilly et al., but not if we use the empirical formulation of Mannucci et al.
In order to try to understand the internal evolution of galaxies and relate this to the global ev... more In order to try to understand the internal evolution of galaxies and relate this to the global evolution of the galaxy population, we present a comparative study of the dependence of star formation rates on the average surface mass densities (Σ M) of galaxies at 0.5< z< 0.9 and 0.04< z< 0.08, using the zCOSMOS and Sloan Digital Sky Survey (SDSS) surveys, respectively.
Proceedings of the International Astronomical Union, 2014
ABSTRACT A relation between the stellar mass M and the gas-phase metallicity Z of galaxies, the M... more ABSTRACT A relation between the stellar mass M and the gas-phase metallicity Z of galaxies, the MZR, is observed up to higher redshifts. It is a matter of debate, however, if the SFR is a second parameter in the MZR. To explore this issue at z &gt; 1, we used VLT-SINFONI near-infrared (NIR) spectroscopy of eight zCOSMOS galaxies at 1.3 &lt; z &lt; 1.4 to measure the strengths of four emission lines: Hbeta, [OIII]lambda5007, Halpha, and [NII]lambda6584, additional to [OII]lambda3727 measured from VIMOS. We derive reliable O/H metallicities based on five lines, and also SFRs from extinction corrected Halpha measurements. We find that the MZR of these star-forming galaxies at z~1.4 is lower than the local SDSS MZR by a factor of three to five, a larger change than reported in the literature using [NII]/Halpha-based metallicities from individual and stacked spectra. Correcting N2-based O/Hs using recent results by Newman et al. (2014), also the larger FMOS sample at z~1.4 of Zahid et al. (2014) shows a similar evolution of the MZR like the zCOSMOS objects. These observations seem also in agreement with a non-evolving FMR using the physically motivated formulation of the FMR from Lilly et al. (2013).
The Calar Alto Deep Imaging Survey (CADIS) [5] combines a deep emission line survey employing an ... more The Calar Alto Deep Imaging Survey (CADIS) [5] combines a deep emission line survey employing an imaging Fabry-Perot-Interferometer ( F lim= 3 x 10-20 Wm-2) with a moderately deep multi-band survey ( 400 &amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;=lambda &amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;=2300nm, Rlim~= 24). One of its major goals is the search for Ly-alpha galaxies in three redshift windows around z ~= 4.8, 5.7 and 6.6. Six
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