Welcome to the Homepage of 
Dr. Christian Maier
Extragalactic Astrophysics Group

University of Vienna
Department of Astronomy

Türkenschanzstrasse 17,
1180 Wien,
Office: 010.5
Tel. +43 1 4277-53827
Fax: +43 1 4277-9518
Email: christian.maier(at)univie.ac.at

I am currently a Univ. assistant in the Extragalactic Astrophysics Group of Prof. Bodo Ziegler.
I am a member of the COSMOS team, a core member of the zCOSMOS team, and a member of the VLT-CLASH team.

Teaching, Recent Talks, Observing Programs and Publications

June 2014 Publication: C. Maier, S.J. Lilly, B. Ziegler et al. The mass-metallicity and fundamental metallicity relations at z>2 using VLT and Subaru near-infrared spectroscopy of zCOSMOS galaxies, 2014, arXiv:1406.6069, accepted for publication in ApJ

June 2014 Observations 3 nights FMOS at Subaru telescope awarded, visitor-mode in January 2015 : Z(M,SFR) at z>2 and the existence of the fundamental metallicity relation

Mai 2014 Talk: COSMOS-CLASH: The existence and universality of the fundamental metallicity relation at z<2.5 and environmental effects, at the Multiwavelength-surveys: Galaxy Formation and Evolution from the early universe to today, Dubrovnik, Croatia

March 2014 - June 2014 Astronomical Laboratory Exercises Astronomisches Anfaengerpraktikum (SS 2014)

Feb 2014 Observations PI of Subaru program S14A-003 (FMOS observations 11/12 February): The mass-metallicity and fundamental metallicity relation at z>2

Oct 2013 - Jan 2014 Lecture Giant black holes and their host galaxies (WS 2013)

Sep 2013 Talk: A VLT-SUBARU synergy to establish the mass-metallicity relation of main sequence galaxies at z<2.5, at the Galaxy Evolution over Five Decades, Cambridge, UK

Sep 2013 Publication: Lisa Kewley, Christian Maier et al. The Cosmic BPT Diagram: Confronting Theory with Observations, 2013, ApJ, 774, 10

May 2013 Talk: A VLT-SUBARU synergy to establish the mass-metallicity relation of main sequence galaxies at z>2, at the COSMOS Team Meeting Kyoto 2013

March 2013 - June 2013 Lecture Galaxy Evolution (SS 2013)

March 2013 - June 2013 Astronomical Laboratory Exercises Astronomisches Anfaengerpraktikum (SS 2013)

Dec 2012 Observations 15 hours VLT-SINFONI awarded, rank A, service mode observations, for P91 (starting in April 2013) : The evolution of the mass-metallicity and fundamental metallicity relation from reliable SFRs, masses and metallicities of zCOSMOS galaxies at z ~ 1.4

Oct 2012 - Jan 2013 Lecture Giant black holes and their host galaxies (WS 2012)

Sep 2012 Publication Perez-Montero, E., Contini, T., Lamareille, F., Maier, C. et al., The cosmic evolution of oxygen and nitrogen abundances in star-forming galaxies over the last 10 Gyrs, 2013, A&A, 549, 25

June 2012 Invited Talk The evolution of the mass-metallicity relation at 0 < z < 2.5 revealed by near-infrared spectroscopy at Metals in Tuscany 2012

March 2012 - June 2012 Lecture Galaxy Evolution (SS 2012)

April 2012 Talk at Metals in 3D: New insights from Integral Field Spectroscopy, Granada, 2012

March 2012 - June 2012 Astronomical Laboratory Exercises Astronomisches Anfaengerpraktikum (SS 2012)

Oct 2011 - Jan 2012 Seminar for master and doctoral students Galaxy Evolution

Talk at the COSMOS meeting, Honolulu, Hawaii, USA

Talk at the COSMOS meeting, Matsuyama, Ehime, Japan

Curriculum Vitae

1994: Abitur, mark : 1.2 _ very good, Konstanz, Germany
1994 - 1999: study of physics at the University Heidelberg
1998 - 1999: Diploma thesis: (Abstract), at Landessternwarte Heidelberg, Germany
July 1999: Diploma in Physics, University Heidelberg (mark : very good)
1999 - 2002: Ph.D thesis: Emission Line Galaxies from CADIS: High Redshift Lyman-Alpha Galaxies and Metal Poor Galaxies at Medium Redshift 2002PhDT.........2M, in Max-Planck-Institut für Astronomie Heidelberg, Germany
4th December 2002: PhD in Astronomy (mark : magna cum laude), University Heidelberg, Germany, Laudatio
1998 - 1999 Landessternwarte Heidelberg
1999 - 2003 Max-Planck-Institut für Astronomie, Heidelberg
2003 - 2011 Institute of Astronomy, ETH Zürich
2007 - 2011 ETH Ober-Assistent, zCOSMOS data manager
since Oct 2011 University of Vienna, Institute for Astrophysics

Research Interests

As the zCOSMOS data manager I have been responsible for the data handling of the 600 hours of zCOSMOS raw VIMOS data from ESO and preparing them for processing. My main research interests include

Recently Awarded Scientific Programs with Large Telescopes

PI of program 084.B-0232 SINFONI at the VLT,
Chemical evolution: metallicities of vigorously star-forming galaxies at z ~ 2.3,
37 hours in service mode

PI of program 084.B-0312 ISAAC at the VLT,
Establishing the evolutionary status of candidates low-metallicity luminous galaxies at z ~ 0.7,
23.5 hours in service mode

PI of program S09B-013 MOIRCS at the SUBARU telescope,
Chemical evolution: metallicities of vigorously star-forming galaxies at z ~ 2.3,
2.5 nights in visitor mode

PI of program 085.B-0317 ISAAC at the VLT,
Establishing the role of ENVIRONMENT on METALLICITIES of galaxies at 0.5 < z< 0.7,
23.5 hours in service mode

Metallicities at the Peak of the Cosmic Star Formation Rate:
Implications for the Evolution of Galaxies

Gas metallicities are a particularly important diagnostic of galaxy evolution. The rather unexplored 1 < z < 2 redshift regime is one of particular importance to trace the evolution of the metal content in galaxies: there, the star formation and metal production rates for the universe as a whole, as measured by the the integrated luminosity density in the ultraviolet and far-infrared, appear to peak, i.e., are a factor of about 6 higher relative to the local value. Furthermore, this is the redshift regime where the galaxy population clearly undergoes a transition in properties: it is beyond z~1 that luminous ultraviolet star-forming galaxies with ``unobscured'' star-formation rates above ~10 Msol/yr appear in optically-selected galaxy samples. Such galaxies are not detected below z~0.8-1.0. Studies of the metal content of the star forming galaxies at these key epochs are however sparse.

Figure 1. We have used VLT-ISAAC near-infrared spectroscopy for a sample of five [OII]-selected, M_B,AB<~-21.5, z~1.4 galaxies, to measure their Hbeta, [OIII]5007, Halpha emission line fluxes, and upper limits for [NII]6584 fluxes. These have allowed us to determine accurate [O/H] abundances for the z~1.4 galaxies, which we have compared with those of galaxies at lower redshifts and with chemical evolution models. Not surpringsingly, we see a relationship between redshift and inferred chemical age. For example, despite the large scatter, the bright, M_B,AB<-19.5, z~1.4 galaxies (black filled squares) appear to be ``younger'' than 0.7 < z < 0.9 galaxies (red filled squares), in the sense that they lie towards the beginning of the luminosity-metallicity track. The 0.7 < z < 0.9 galaxies appear in turn to be on average ``younger'' than most 0.5 < z < 0.7 galaxies (green filled squares), which themselves overlap on the diagram with the metallicity-luminosity relation traced by nearby galaxies.

The tracks of the chemical evolution models in Fig. 1 suggest that the bright star forming z~1.4 galaxies are likely to evolve into the population of less luminous but nonetheless rather massive, metal-rich galaxies that appear in the 0.5 < z < 0.9 galaxy population. The broad range of galaxy morphologies suggests that the metal-enriched reservoirs of star forming gas that we are probing at intermediate redshifts are being mostly consumed to build up both the disk and the bulge components of spiral galaxies.

Our analysis of the metallicity-luminosity relation at 0 < z < 1.5 suggests that the period of rapid chemical evolution takes place progressively in lower mass systems as the universe ages. The Figure shows the signatures of this "downsizing" effect: (a) at z < 0.7 (green symbols) nearly all galaxies with M_B,AB<-20 are fairly close to the low-z [O/H]-M_B relation (with one obvious exception); (b) at 0.7 < z < 0.9, this is true only for M_B,AB<-21.3; and (c) at z~1.4 even the most luminous galaxies are evolved off of the low redshift [O/H]-M_B,AB relation. As the Universe ages, particular signatures of "youth" (e.g., high [OIII]/[OII] or low [O/H]) are seen in progressively less luminous, less massive systems!

Which galaxies contribute to the star formation rate density over the past 8 billion years?

One of the key unanswered questions in the study of galaxy evolution is what physical processes inside galaxies drive the changes in the star formation rates in individual galaxies that, taken together, produce the large decline in the global star-formation rate density to redshifts since z ~ 2 (Lilly et al. 1996, Hippelein, Maier et al. 2003). Studies using the local SDSS sample have argued that the surface mass density may be more important than stellar mass in regulating star formation. Using the SDSS sample Brinchmann et al. (2004) found that the low specific star formation rate (SSFR, star formation rate / unit stellar mass) peak is more prominent at high surface density than at high stellar mass, and therefore concluded that the surface density of stars is more important than stellar mass in regulating star formation.

Figure 2. The shape of the specific SFR (SSFR) versus stellar mass surface density relation for relatively massive zCOSMOS z~0.7 galaxies is very similar to that of local SDSS galaxies (left panel). There is a roughly uniform increase in the average SSFR by a factor of 5-6 that is broadely independent of surface mass density, and which occurs for both late-type (middle panel), and early-type (right panel) galaxies. This emphasizes that galaxies of all types are contributing, proportionally, to the global increase in star formation rate density in the Universe back to these redshifts. Disk galaxies have a SSFR that is almost independent of surface mass density, and the same is probably also true of high Sersic index galaxies once obvious disk systems are excluded (red squares in the right panel).

Using the HST/ACS images of the COSMOS field, plus star formation rate information from emission lines measured in large numbers of zCOSMOS spectra we can study the changes that have occured in the SSFR - surface mass density relation between redshifts approaching z~1 and the present epoch, as sampled by the SDSS studies. The requirement is that we can select comparable samples at the different redshifts, and therefore we derive star formation rates, stellar masses, and structural parameters in a consistent way for both zCOSMOS and SDSS samples, and apply them to samples that are complete down to the same stellar mass at both redshifts.

Figure 3. The SSFR - surface mass density step-function (Fig.1) is clearly due to the change-over of different structural types from disk-dominated low Sersic galaxies (n<1.5) to bulge-dominated high Sersic galaxies (n>2.5), as the surface mass density increases. The cross-over point shifts to higher surface mass density in zCOSMOS compared to SDSS, because of a modest differential evolution in the size-mass relations of disk and spheroid galaxies.

Selected Papers

Conferences 2004 - 2008