The static and dynamic properties of many-body quantum systems are often well described by collective excitations, known as quasiparticles. Engineered quantum systems offer the opportunity to study such emergent phenomena in a precisely controlled an
d otherwise inaccessible way. We present a spectroscopic technique to study artificial quantum matter and use it for characterizing quasiparticles in a many-body system of trapped atomic ions. Our approach is to excite combinations of the systems fundamental quasiparticle eigenmodes, given by delocalised spin waves. By observing the dynamical response to superpositions of such eigenmodes, we extract the system dispersion relation, magnetic order, and even detect signatures of quasiparticle interactions. Our technique is not limited to trapped ions, and it is suitable for verifying quantum simulators by tuning them into regimes where the collective excitations have a simple form.
(Abridged) The knowledge of the number and of the physical nature of low-metallicity massive galaxies is crucial for the determination and interpretation of the mass-metallicity relation (MZR). Using VLT-ISAAC near-infrared (NIR) spectroscopy of 39 z
COSMOS z~0.7 galaxies, we have measured Halpha and [NII] emission line fluxes for galaxies with [OII], Hbeta and [OIII] available from VIMOS optical spectroscopy. The NIR spectroscopy enables us to break the degeneracy of the R23 method to derive unambiguously O/H gas metallicities, and also SFRs from extinction corrected Halpha. Using, as a benchmark, the position in the D4000 vs. [OIII]/Hbeta diagram of galaxies with reliable O/Hs from NIR spectroscopy, we were able to break the lower/upper branch R23 degeneracy of additional 900 zCOSMOS z~0.7 galaxies. Additionally, the Halpha-based SFR measurements were used to find the best SFR calibration based on [OII] for the zCOSMOS z~0.7 galaxies without Halpha measurements. We find a fraction of 19% of lower mass 9.5<logM/Msun<10.3 zCOSMOS galaxies which shows a larger evolution of the MZR relation, compared to higher mass galaxies, being more metal poor at a given mass by a factor of 2-3 compared to SDSS. This indicates that the low-mass MZR slope is getting steeper at z~0.7 compared to local galaxies. The existence of these metal-poor galaxies at z~0.7 can be interpreted as the chemical version of galaxy downsizing. Moreover, the sample of zCOSMOS galaxies shows direct evidence that SFR influences the MZR at these redshifts. The comparison of the measured metallicities for the zCOSMOS sample with the values expected for a non-evolving fundamental metallicity relation (FMR) shows broadly agreement, and reveals that also galaxies with lower metallicities and typically higher (specific) SFRs, as found in our zCOSMOS sample at z~0.7, are in agreement with the predictions of a non-evolving Z(M,SFR).
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 > 1, we used VL
T-SINFONI near-infrared (NIR) spectroscopy of eight zCOSMOS galaxies at 1.3 < z < 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).
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 invaria
nt 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: [OII], Hbeta, [OIII], Halpha, and [NII]. This near-infrared spectroscopy enables us to derive O/H metallicities, and also SFRs from extinction corrected Halpha measurements. We find that the mass-metallicity relation (MZR) of these star-forming galaxies at z~2.3 is lower than the local SDSS MZR by a factor of three to five, a larger change than found by Erb et al. (2006) using [NII]/Halpha-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 mass-metallicity relation 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. (2003), but not if we use the empirical formulation of Mannucci et al. (2010).
We present in these proceedings some preliminary results we have obtained studying the evolution of the specific star formation rate as a function of surface mass density and Sersic indices at z<0.7. These results are based on the consistent comparis
on of the properties of ~ 650 massive zCOSMOS galaxies in a mass-complete sample at 0.5<z<0.7 with a mass-complete sample of ~ 21500 SDSS local galaxies.
One of the key unanswered questions in the study of galaxy evolution is what physical processes inside galaxies drive the changes in the SFRs in individual galaxies that, taken together, produce the large decline in the global star-formation rate den
sity (SFRD) to redshifts since z~2. Many studies of the SFR at intermediate redshifts have been made as a function of the integrated stellar mass of galaxies but these did not use information on the internal structural properties of the galaxies. In this paper we present a comparative study of the dependence of SFRs on the average surface mass densities (SigmaM) of galaxies of different morphological types up to z~1 using the zCOSMOS and SDSS surveys. The main findings about the evolution of these relatively massive galaxies are: 1) There is evidence that, for both SDSS ans zCOSMOS galaxies, the mean specific SFR within a given population (either disk-dominated or bulge-dominated) is independent of SigmaM; 2) The observed SSFR - SigmaM step-function relation is due, at all investigated redshifts, to the changing mix of disk-dominated and bulge-dominated galaxies as surface density increases and the strong difference in the average SSFR between disks and bulges. We also find a modest differential evolution in the size-mass relations of disk and spheroid galaxies; 3) The shape of the median SSFR - SigmaM relation is similar, but with median SSFR values that are about 5-6 times higher in zCOSMOS galaxies than for SDSS, across the whole range of SigmaM, and in both spheroid and disk galaxies. This increase matches that of the global SFRD of the Universe as a whole, emphasizing that galaxies of all types are contributing, proportionally, to the global increase in SFRD in the Universe back to these redshifts (abridged).
We present a study of the host galaxies of AGN selected from the zCOSMOS survey to establish if accretion onto supermassive black holes and star formation are explicitly linked up to z~1. We identify 152 galaxies that harbor AGN, based on XMM observa
tions of 7543 galaxies (i<22.5). Star formation rates (SFRs), including those weighted by stellar mass, are determined using the [OII]3727 emission-line, corrected for an AGN contribution. We find that the majority of AGN hosts have significant levels of star formation with a distribution spanning ~1-100 Msun yr^-1. The close association between AGN activity and star formation is further substantiated by an increase in the AGN fraction with the youthfulness of their stars as indicated by the rest-frame color (U-V) and spectral index Dn(4000); we demonstrate that mass-selection alleviates an artifical peak falling in the transition region when using luminosity-limited samples. We also find that the SFRs of AGN hosts evolve with cosmic time in a manner that closely mirrors the overall galaxy population and explains the low SFRs in AGNs (z<0.3) from the SDSS. We conclude that the conditions most conducive for AGN activity are a massive host galaxy and a large reservoir of gas. Furthermore, a direct correlation between mass accretion rate onto SMBHs and SFR is shown to be weak although the average ratio is constant with redshift, effectively shifting the evidence for a co-evolution scenario in a statistical manner to smaller physical scales. Our findings illustrate an intermittent scenario with an AGN lifetime substantially shorter than that of star formation and underlying complexities regarding fueling over vastly different physical scales yet to be determined [Abridged].
