INAF Post-Doctoral Fellowship 2010Violeta Gonzalez-Perez

INAF Post-doctoral Fellowship 2010Violeta Gonzalez-Perez

INAF

POST-DOCTORAL FELLOWSHIPS 2010

To: POST-DOCTORAL FELLOWSHIPS 2010

INAF – National Institute for Astrophysics

Viale Parco Mellini, 84

00136 Rome – Italy

First name...... Violeta......

Surname...... Gonzalez-Perez......

Family name......

Date of Birth...... 30th October 1979......

Town of Birth...... Zaragoza......

Country...... Spain......

Nationality...... Spaniard......

Address for correspondence...... ICC, Durham University,

South Road, Durham DH1 3LE, UK

Home Address...... Flat 10, St Andrew's Court, Durham DH1 3AH, UK

Telephone...... + 44 191 334 3765...... Fax...... -......

e-mail...... ......

I apply for a post-doc fellowship to carry out a research programme at:

----Trieste Astronomical Observatory------

(host research structure)

___Gabriella de Lucia______

(scientific contact person at the host research structure)

PhD or equivalent degree with a thesis on :

...... Astrophysics: “Properties and evolution of galaxies” Supervisor: F. J. Castander

Awarded on ...... 28th September 2009...... (date)

At...... Universitat de Barcelona...... (Institution, University, etc.)

Title of the Research Programme submitted to INAF:

...... How big is the Milky Way? Predicting the size and structure of our galaxy and others.

Thematic Area

...... Galaxies and Cosmology......

(to be chosen among) :

1. Galaxies and Cosmology
2. Stars, Stellar Population and Interstellar medium
3. Sun and Solar System
4. Relativistic and Particle Astrophysics
5. Advanced Technology and Instruments

Enclosures:

a)Curriculum Vitae

b)List of Pubblications

c)A summary of previous and current research

d)A copy of the research proposal

e)Endorsement letter

f)Names and e-mail contacts for the referees

Signature...... Date......

a) Curriculum Vitae: Violeta GONZALEZ-PEREZ

Born: October 30th, 1979 in Zaragoza, Spain – Spaniard

Academic Positions:

Education:

Teaching experience:

Durham University, UK

Universitat Autònoma de Barcelona, Spain

Computing experience:

• Advanced use of Fortran77, Fortran90 and IDL.
• Working knowledge of Shell scripting, IRAF, Sql, Awk, Python, Perl, SExtractor, Hyperz and HTML.
• Semi-analytical galaxy formation code GALFORM; populating Millenium N-body simulation with galaxies.

Observing experience:

• WFIRC infrared camera at the 2.5m du Pont telescope (Las Campanas, Chile), 5 nights, one visit in 2004. Observations and reduction of images done for the MUSYC survey.

Other relevant experience:

• Referee for the Monthly Notices of the Royal Astronomical Society since 2009.
• Organisation of Seminars:Joves talk, 2006/07, seminars for graduate students, ICE(CSIC/IEEC), Barcelona, Spain.
• ESA Student Parabolic Flight Campaign: Member of the APSIDE-1 team selected with an experiment on fluid physics, 2002.

Scholarships Awarded:

Seminars and talks:

Public Outreach:

Participation in research projects:

Schools and meetings attended:

b) List of Publications

Refereed publications:

1. V. Gonzalez-Perez, F. J. Castander, G. Kauffmann, Colour gradients within SDSS DR7 galaxies: Hints of recent evolution, 2010, MNRAS tmp1730G (arXiv:1008.2354).

1. V. Gonzalez-Perez, C. M. Baugh, C. Almeida, C. G. Lacey, Massive, red galaxies in a hierarchical universe-I: Counts of Extremely Red Objects and basic properties, 2009, MNRAS, 398, 497.

1. Edward N Taylor, Marijn Franx, Pieter G van Dokkum, Ryan F Quadri, Eric Gawiser, Eric F Bell, L Felipe Barrientos, Guillermo A Blanc, Francisco J Castander, Maaike Damen, Violeta Gonzalez-Perez, Patrick B Hall, David Herrera, Hendrik Hildebrandt, Mariska Kriek, Ivo Labbé, Paulina Lira, José Maza, Gregory Rudnick, Ezequiel Treister, C Megan Urry, Jon P Willis, Stijn Wuyts, A Public, K--Selected, Optical--to--Near-Infrared Catalog of the Extended Chandra Deep Field South (ECDFS) from the Multiwavelength Survey by Yale--Chile (MUSYC), 2009, ApJS, 183, 295.

1. R. López-Ruiz, F. Luis, V. González, A. Millán, J. L. García-Palacios, Nonlinear response of single-molecule nanomagnets: equilibrium and dynamical, 2005, Phys. Rev. B 72, 224433.

1. F. Luis, V. Gonzalez, A. Millan, J. L. Garcia-Palacios, Large quantum nonlinear dynamic susceptibility of single-molecule magnets, 2004, Phys. Rev. Lett., 92, 10, 107201

Conference proceedings:

1. V. Gonzalez-Perez, C. M. Baugh, C. Almeida, C. G. Lacey, Extremely Red Objects in a hierarchical universe, 2010, Highlights of Spanish Astrophysics V, Springer-Verlag Berlin Heidelberg, p. 297.

1. V. Gonzalez-Perez, F. J. Castander, G. Kauffmann, Can we find early-type galaxies with a bluer core today?, 2007, Cosmic Frontiers ASP Conference Series, Vol. 379.

1. V. Gonzalez-Perez, F. J. Castander, G. Kauffmann, 2007, Early-type galaxies colour gradient and their relation with global galactic properties, 2006, Highlights of Spanish Astrophysics IV, Springer-Verlag Berlin Heidelberg, CD.

c) A summary of previous and current research

My research career has covered an unusually broad range of subjects, with masters degrees in condensed matter physics and astrophysics, followed by a PhD in astrophysics and now an STFC funded postdoctoral position in Durham. I have published refereed papers in both areas of physics. I have also built up experience of teaching undergraduate students and have undertaken public outreach work. The research I carried out during my PhD, at the Institute of Space Sciences – ICE(CSIC/IEEC), and as a postdoc at Durham University spans both the theoretical and observational approaches to improving our understanding of galaxy formation. At the beginning of my PhD I performed one of the observational campaigns for the Multiwavelength Survey by Yale-Chile (MUSYC) collaboration, performing my own data reduction. Later I started a statistical study of galaxy properties using the publicly available Sloan Digital Sky Survey (SDSS) catalogue. Afterwards, I initiated a new collaboration with researchers from Durham University that has allowed me to use large computer simulations to understand the nature of galaxies in place when the Universe was half its current age. In the same spirit, I have recently started a theoretical project exploring the selection and properties of Lyman Break Galaxies, which currently set the record for the earliest population of galaxies studied in the Universe, thanks to the Hubble Space Telescope. Below, I summarize the two major projects that I have led in my astrophysics research:

i. Massive, red galaxies at z 1: a challenge to hierarchical models

Gonzalez-Perez et al (2009; 14 citations) and two related rst author papers in preparation

In the current structure formation paradigm, galaxies form inside dark matter haloes which are assembled through mergers. This hierarchical growth means that the most massive haloes tend to form the most recently. This scenario has been challenged recently by several deep photometric surveys which have suggested that galaxies with very red colours are in place at early epochs in the history of the Universe. These objects are unexpected because their red colours mean that they either have very old stars with no recent star formation or that they are undergoing a vigorous phase of star formation which is heavily obscured. These observations are at odds with naive expectations based on the hierarchical sequence of structure formation in the dark matter. To test the cold dark matter model against observations, it is necessary to model the interconnected processes which control the fate of the baryons, which is only possible through computer simulation. Even so, early attempts to explain the abundance of these extremely red galaxies failed spectacularly, missing the observed counts by an order of magnitude.

In collaboration with C. M. Baugh, C. G. Lacey and C. Almeida (Durham), I led a comparison of the prediction of two semi-analytical models (Baugh et al. 2005, Bower et al. 2006) with observations of red galaxies at z>1, selected using different observational colour criteria (EROs, DRGs, BzKs). Semi-analytical models of galaxy formation use simple, physically motivated recipes and rules to follow the fate of baryons in a universe in which structures grow hierarchically through gravitational instability. Semi-analytical models are a powerful technique to simulate the formation and evolution of galaxies, since they allow for a wide exploration of the physical processes that interplay in the galactic evolution. In Gonzalez-Perez et al. (2009), I provided the first example of a hierarchical model which could explain the abundance of extremely red galaxies (EROs). The key to understanding these objects proved to be the inclusion of AGN feedback, which suppresses the cooling of gas in massive haloes. I currently have two further papers on this topic which are at an advanced stage of preparation. The first addresses the clustering of EROs, which provides a crucial test of theoretical models since it constrains the host halo masses. EROs are observed to be highly clustered. Thus, accurate measurements of EROs clustering can only be achieved by sampling large areas, currently this is being achieved by dierent near-infrared surveys. The second paper investigates the present-day descendants of these galaxies, mainly massive early-type galaxies, and relates populations of red objects selected using different criteria (e.g. DRGs, BzKs selection). The question of the present day descendants of high redshift galaxies can only be properly addressed using semi-analytical models as the one I have been using.

This project enabled me to build invaluable experience of running and analysing semianalytical galaxy formation models in combination with N-body simulations, with datasets running into hundreds of Gigabytes, and of measuring and studying a range of galaxies properties: number counts, mass distribution, clustering, etc. Besides developing the computational skills needed to deal with large datasets, through this work I have gained a good understanding of the potential and the limitations of semi-analytical models as a tool for understanding the mechanisms that drive galaxy formation. Currently such expertise is restricted to a small number of researchers globally.

ii. Internal properties of galaxies: beyond the resolution of hierarchical models

Gonzalez-Perez et al. (2010; 1 citation).

The internal structure of a galaxy is shaped by the evolutionary path that it has followed. Therefore, the study of internal properties can elucidate the physical processes that have determined the recent history of galaxies. Simulations within the context of hierarchical models have shown how the properties of the progenitors of a galaxy shape its internal structure. Consequently, the recent evolution of galaxies, as uncovered by studying their internal properties can be helpful to test different formation scenarios.

In collaboration with F. J. Castander (Barcelona) and G. Kauffmann (Munich), I have led a study on the internal colour variations in galaxies, using four luminosity-threshold samples drawn from the Sloan Digital Sky Survey (SDSS, York et al. 2000). This variation is related to most of the features that shape the galactic interior, such as the occurrence of localised starbursts, and gradients in the metallicity and age of stellar populations. In Gonzalez-Perez et al. (2010), I found that it is more likely to observe steep colour gradients among late-type galaxies. This result holds for a range of classifications based on both morphological and spectral characteristics. In fact, my results relate, on average, steep colour gradients to a higher presence of young stars within a galaxy. I also found that nuclear activity is a marginal driverfor creating steep colour gradients in massive galaxies. I estimated the colour gradients within close pairs of galaxies, separated 5 arcsec in projected radius and 100km/s in redshift, finding that they present steeper gradients than the average population, skewed towards bluer cores. All this demonstrates that the colour gradient is a useful means to select galaxies with a high probability of having sufered a (minor) burst of star formation in their recent past.

The study of colour gradients requires a reliable measurement of the radial flux profile. Thus, I carried out a careful selection using both SDSS pipeline flags and error estimates on photometric quantities. For this process, I learnt SQL and PYTHON. To improve the analysis further, I improved an existing F77 code, that corrects galaxy colours for the evolution and band shifting of their spectra. In this work, the error analysis was performed using Monte Carlo simulations, when a simple error propagation was inadequate.

d) Research proposal

How galaxies form and evolve is a fundamental question in astrophysics that has led to the development of enhanced computational models and promoted the development of cutting edge instrumentation. Since the 1990s the number and grasp of extragalactic surveys has grown considerably, allowing both observations of the large scale structure of the Universe and studies of how galaxies appeared at different epochs, reaching far back in time to when the Universe was one tenth of its present age. The challenge now is to develop theoretical models to the stage where they can provide advanced and robust predictions to test against the new observational data. My research proposal aims to develop a theoretical framework to allow the most comprehensive understanding of the physical processes that shape galaxies, putting them into a cosmological context. In order to fulfil this goal, I will use a combination of hydrodynamical simulations and semi-analytical modelling, providing a good illustration of the way in which our understanding of galaxy formation can be advanced. The hydrodynamical simulations will improve our knowledge of the fate of gas and stars in dynamically unstable disks and following mergers. Hydrodynamical simulations of galaxy formation within a cosmological volume are currently unable to provide robust, converged results, and they neither match the observed galaxy luminosity function. Semi-analytical modelling is currently the only way to generate predictions for large populations of galaxies in the cold dark matter cosmology. My proposed research has two phases covering the following aspects:

Phase 1 – Merger remnants and instabilities

Observations of interacting galaxies suggest that mergers could be the fundamental drivers in shaping the morphologies, sizes and masses of galaxies. The present treatment of the impact of galaxy collisions in semi-analytical models is crude and in urgent need of a complete overhaul. This proposal aims to achieve this by performing a carefully designed and comprehensive suite of hydrodynamical simulations of galaxy mergers. In order to cover a representative sample of cases I propose to carry out two sets of simulations:

1. Isolated disks: The aim of simulating isolated disks is to study disk instabilities, the formation of bars, and the effect they have on the subsequent size, structure and star formation rate of the galaxies. These simulations will cover realistic ranges of the initial mass and gravitational potential well.

1. Interacting galaxies: I will consider three scenarios: 1) Disk-disk interactions, 2) Disk-Spheroid interactions, 3) Multiple disks interactions. For each set I will vary two parameters: the relative mass and gas content of the interacting galaxies. The selection of the actual parameters will be done based on a careful analysis of the most common interactions happening in both semi-analytical simulations and observations.

In order to check the validity of the results obtained, the grid of simulations will be compared with previous numerical studies, where these overlap with my calculations, and deep observations, such as those from EDisCS. Trieste participates in this survey designed to study cluster structure and cluster galaxy evolution over a large fraction of cosmic time. This survey is focused on 20 fields containing galaxy clusters at redshifts between 0.4 and 1. Such a set of observations is a perfect match to compare interactions simulations with.