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220 result(s) for "Ziegler, Bodo"
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Kinematic Evolution of Field and Cluster Spiral Galaxies
We investigate the evolution of the Tully–Fisher relation out to z = 1 with 137 emission-line galaxies in the field that display a regular rotation curve. They follow a linear trend with lookback time being on average brighter by 1.1 Bmag and 60% smaller at z = 1. For a subsample of 48 objects with very regular gas kinematics and stellar structure we derive a TF scatter of 1.15mag, which is two times larger than local samples exhibit. This is probably due to modest variations in their star formation history and chemical enrichment. In another study of 96 members of Abell 901/902 at z = 0.17 and 86 field galaxies with similar redshifts we find a difference in the TFR of 0.42mag in the B-band but no significant difference in stellar mass. Comparing specifically red spirals with blue ones in the cluster, the former are fainter on average by 0.35 Bmag and have 15% lower stellar masses. This is probably due to star formation quenching caused by ram-pressure in the cluster environment. Evidence for this scenario comes from strong distortions of the gas disk of red spirals that have at the same time a very regular stellar disk structure.
Oxygen abundances of zCOSMOS galaxies at z ∼ 1.4 based on five lines and implications for the fundamental metallicity relation
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 VLT-SINFONI near-infrared (NIR) spectroscopy of eight zCOSMOS galaxies at 1.3 < z < 1.4 to measure the strengths of four emission lines: Hβ, [OIII]λ5007, Hα, and [NII]λ6584, additional to [OII]λ3727 measured from VIMOS. We derive reliable O/H metallicities based on five lines, and also SFRs from extinction corrected Hα 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]/Hα-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 Evolution of Disk Galaxy Scaling Relations Since Redshift z = 1
Based on VLT/FORS spectroscopy and HST/ACS imaging, we have constructed a sample of 125 field spiral galaxies that cover redshifts up to z = 1. By deriving the galaxies' luminosities, disk sizes, maximum rotation velocities, stellar masses, total masses, gas-phase metallicities etc., we are able to study the evolution of fundamental scaling relations like the Tully–Fisher relation as a function of cosmic time. While the evolution of most of the galaxies' fundamental parameters is in compliance with a hierarchical structure growth, the results from stellar population modelling favour a down-sizing scenario in the sense that the average stellar ages in high-mass spirals are older than in low-mass spirals.
Galaxy Population in the Infall Regions of Intermediate Redshift Clusters
We investigate the galaxy populations in 6 clusters of different x-ray luminosities at intermediate redshifts (z ≈ 0.25) concentrating on their star formation activity. Our ~500 Calar Alto MOSCA spectra come from targets covering large fields out to 2–4 cluster virial radii. To probe this so-called infall region is important since here newly arriving galaxies from the surrounding field encounter the special environment of clusters for the first time. We selected 3 fields containing 2 clusters each from the X-ray Dark Cluster Survey (Gilbank et al. 2004). Results for one field were already published by Gerken et al. 2004. We find evidence that the process(es) that suppresses or truncates the star formation activity in cluster galaxies, sets in already at rather large distances from the cluster cores corresponding to low projected local galaxy densities. This changes the fraction of star forming galaxies rather quickly.
A detailed view of the Fundamental Plane of early–type galaxies in clusters at z$\\sim$0.2
We present a spectroscopic sample of 48 early-type galaxies in the rich cluster Abell 2218 and 50 galaxies in Abell 2390. Since both samples are very similar, we combine them and investigate a total number of 98 early-type galaxies at $z \\sim 0.2$. A subsample of 34 galaxies with HST structural properties is used to construct the Fundamental Plane. Elliptical and S0 galaxies show a zeropoint offset of $\\overline{m}_{r}\\sim0.43$ mag with respect to the local Coma FP. Both sub-samples, ellipticals and lenticulars, exhibit a similar, mild evolution and small scatter. The moderate amount of luminosity evolution is consistent with stellar population models of passive evolution, if $z_{f}\\ge2$ is assumed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html
Evolutionary status of early–type galaxies in distant poor clusters
We introduce our project that investigates the kinematic properties of early–type galaxies in 6 distant poor clusters at $z\\approx0.25$. This study represents a continuation of our efforts to understand galaxy evolution in low-density environments. Higher–resolution MOSCA spectra have been obtained at the Calar Alto 3.5-m telescope with which we can measure absorption line strengths and velocity dispersions. In conjunction with our HST/F702W images of all the clusters, we are able to construct the Fundamental Plane of ellipticals and S0 galaxies in poor clusters at a look-back time of $\\approx3$ Gyr. For galaxies outside the HST field, we concentrate our analysis on the Mg–$\\sigma$ and Faber–Jackson relations. With the line strength diagrams age/metallicity distributions can be derived in densities between the field and rich cluster environments. Comparing with our rich clusters at the same cosmic epochs, the dependence of galaxy formation models on the local environment can be tested more quantitatively.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html
The Hector Survey: integral field spectroscopy of 100,000 galaxies
In March 2013, the Sydney–AAO Multi-object Integral field spectrograph (SAMI) began a major survey of 3400 galaxies at the AAT, the largest of its kind to date. At the time of writing, over a third of the targets have been observed and the scientific impact has been immediate. The Manga galaxy survey has now started at the SDSS telescope and will target an even larger sample of nearby galaxies. In Australia, the community is now gearing up to deliver a major new facility called Hector that will allow integral field spectroscopy of 100 galaxies observed simultaneously. By the close of the decade, it will be possible to obtain integral field spectroscopy of 100,000 galaxies over 3000 square degrees of sky down to r=17 (median). Many of these objects will have HI imaging from the new ASKAP radio surveys. We discuss the motivation for such a survey and the use of new cosmological simulations that are properly matched to the integral field observations. The Hector survey will open up a new and unique parameter space for galaxy evolution studies.
The Wsrt Halogas Survey
We present an overview of the HALOGAS (Hydrogen Accretion in LOcal GAlaxieS) Survey, which is the deepest systematic investigation of cold gas accretion in nearby spiral galaxies to date. Using the deep H i data that form the core of the survey, we are able to detect neutral hydrogen down to a typical column density limit of about 1019 cm−2 and thereby characterize the low surface brightness extra-planar and anomalous-velocity neutral gas in nearby galaxies with excellent spatial and velocity resolution. Through comparison with sophisticated kinematic modeling, our 3D HALOGAS data also allow us to investigate the disk structure and dynamics in unprecedented detail for a sample of this size. Key scientific results from HALOGAS include new insight into the connection between the star formation properties of galaxies and their extended gaseous media, while the developing HALOGAS catalogue of cold gas clouds and streams provides important insight into the accretion history of nearby spirals. We conclude by motivating some of the unresolved questions to be addressed using forthcoming 3D surveys with the modern generation of radio telescopes.