MASTERARBEIT / MASTERS THESIS Titel der Masterarbeit / Title of the Masters Thesis "The slow quenching of CLASH RXJ2248-4431 cluster galaxies as traced by their gas phase metallicities " verfasst von / submitted by Ciocan Bianca-Iulia, BSc angestrebter akademischer Grad / in partial fulfilment of the requirements for the degree Master of Science (MSc) Wien, 2018 / Vienna 2018 Studienkennzahl lt. Studienblatt / A 066 861 degree programme code as it appears on the student record sheet: Studienrichtung lt. Studienblatt / Masterstudium Astronomie UG2002 degree programme as it appears on the student record sheet: Betreut von / Supervisor: Univ.-Prof. Dipl.-Phys. Dr. Bodo Ziegler Mitbetreut von / Co-supervisor: Dipl.-Phys. Dr. Christian Maier Acknowledgements I would like to express my deep gratitude to my research supervisor Univ.-Prof. Dipl.-Phys. Dr. Bodo Ziegler and co-supervisor Dipl.-Phys. Dr. Christian Maier for their encouragement, patient guidance and useful critiques of this research work. I would especially like to thank Dr. Christian Maier for the time that he invested in this master thesis and for the valuable pieces of advice and explanations. Thank you for your teaching me how to use the different softwares needed to quantify the data, and for your expertise on the topic of chemical abundances in galaxies! My grateful thanks are also extended the whole extragalactic astrophysics group for sharing their expertise as well as for their technical support, providing me with valuable information regarding different pipelines and codes used for this master thesis. Special thanks to Jos Manuel Perez Martinez for helping me with the code LePhare, used to compute the stellar masses of the investigated galaxies. A special thanks go to Dr. Miguel Verdugo for writing the python code, which I have used to test the cluster membership of galaxies, and for double-checking the results with me. I would also like to thank Boris Deshev for his pieces of advice regarding FADO, as well as for the python codes he provided me with, in order to extract the output of FADO. I want to express my gratitude towards Dr. Polychronis Papaderos, who patiently checked the output of FADO for the investigated cluster galaxies with me, as well as for all the valuable information he provided regarding the pss code. Thank you for the opportunity to be part of this research group and to work in the field of observational extragalactic astrophysics! iii Contents Abstract viii Abstract Germanx 1 Introduction 1 2 Physical principles3 2.1 Galaxy spectroscopy..................................3 2.2 Evolution of stellar populations and metallicity...................5 2.3 The Fundamental Metallicity Relation and the Bathtub model..........7 2.4 Impact of environment on galaxy evolution..................... 10 3 The data 14 3.1 CLASH-VLT survey.................................. 14 3.2 VIMOS......................................... 15 3.3 CLASH RXJ2248-4431 cluster............................. 16 3.3.1 CLASH-VLT VIMOS spectra......................... 16 3.4 WFI........................................... 17 3.4.1 Archival imaging data with WFI....................... 17 4 Methods 19 4.1 Measurement of the emission line fluxes....................... 19 4.1.1 VIPGI...................................... 19 4.1.2 splot in IRAF.................................. 21 4.1.3 FADO...................................... 23 4.2 Mass estimation.................................... 30 4.2.1 LePhare of Arnouts and Ilbert et al. 2011................. 31 4.3 Sample selection.................................... 39 4.3.1 Selection of cluster galaxies for metallicity study.............. 39 4.3.2 Comparison sample of field galaxies..................... 40 5 Results 43 5.1 Colour-Magnitude and Colour-Mass diagrams.................... 43 iv 5.2 Star forming galaxies and Type II AGNs....................... 49 5.2.1 BPT diagram for RXJ2248 cluster members................. 50 5.2.2 WHAN diagram for RXJ2248 cluster members............... 52 5.2.3 SF galaxies and Type II AGNs in the field population........... 55 5.3 Stellar Mass - Star Formation Rate relation..................... 60 5.3.1 Derivation of SFRs............................... 60 5.3.2 sSFR-Mass relation for RXJ2248 cluster members............. 65 5.3.3 sSFR-Mass relation for the comparison field sample............ 67 5.4 Mass-Metallicity relation................................ 70 5.4.1 Derivation of oxygen abundances...................... 71 5.4.2 MZR for RXJ2248 cluster members..................... 73 5.4.3 MZR for field sample.............................. 79 5.5 Comparison cluster to field galaxies.......................... 80 5.6 Cluster membership.................................. 83 5.7 Phase-space....................................... 87 5.8 Tentative evidence for strangulation......................... 89 5.8.1 (O/H) comparison between field galaxies and cluster members at different cluster centric radii............................... 89 5.8.2 The fundamental metallicity relation Z(M,SFR) for the RXJ2248 galaxies 95 5.8.3 The fundamental metallicity relation Z(M,SFR) for the comparison sample of field galaxies................................ 101 5.8.4 FMR Z(M,SFR) comparison between field galaxies and cluster members at different cluster centric radii........................ 104 5.8.5 Discussion: environmental effects...................... 107 6 Summary and conclusion 112 A LePhare of Arnouts and Ilbert et al. 2011 116 A.1 Computation of stellar masses............................. 116 A.2 Synthetic Subaru BRz observed magnitudes.................... 116 B FADO measurements 121 C MZR 123 C.1 MZR for RXJ2248 cluster members.......................... 123 C.2 MZR for field galaxies................................. 124 D Phase Space 130 E (O/H) comparison between field galaxies and cluster members at different cluster centric radii 134 v F The fundamental metallicity relation 139 F.1 The fundamental metallicity relation Z(M,SFR) for the RXJ2248 galaxies.... 139 F.2 The fundamental metallicity relation Z(M,SFR) for the field galaxies....... 142 G Tables 145 Bibliography 151 vi Abstract Aims: Gas-phase metallicities offer a deep insight into the chemical evolution of galaxies as they reflect the recycling of gas through star formation, galactic inflows and outflows. The environment in which a galaxy resides also plays an important role in modelling its evolution. Galaxies in dense environments such as clusters will have slightly different properties as compared to their field counterparts, because of gravitative interactions between the cluster members and hydrodynamical interactions between the hot intra-cluster medium and the interstellar medium of galaxies. In order to explore the environmental effects on gas regulation within galaxies, I have chosen to conduct a spectroscopic analysis of emission line, intermediate redshift cluster galaxies in comparison to a sample of field galaxies. Methods: The data set on which this research is based, consists of CLASH-VLT VIMOS spectra and WFI photometry for ∼ 700 intermediate and late type galaxies at 0:1 < z < 0:9, out of which ∼ 178 are members of the CLASH cluster Abell S1063 (RXJ2248-4431) with zmed = 0:348. The fluxes of [OII] λ3727, Hβ λ4861, [OIII] λ5007, Hα λ6564 and [NII] λ6584 emission lines were measured allowing the derivation of (O/H) gas metallicities, star formation rates based on extinction-corrected Hα and [OII] fluxes and active galactic nuclei (AGN) contamination. The stellar masses of the galaxies were computed from the available photometric data using the code LePhare of Arnouts and Ilbert et al. (2011). In order to explore the accretion history of the RXJ2248 cluster members, a phase-space analysis was conducted. The chemical evolutionary paths of the cluster members were also investigated based on the Fundamental-Metallicity- Relation expectation of Lilly et. al (2013), in order to search for signs of star formation quenching as the galaxies travel towards the cluster centre. Results: Our targets can be classified as blue-cloud galaxies according to the colour-magnitude diagram. Cluster and field galaxies follow the SF-sequence in the diagnostic diagrams, which allow disentangling between the ionising sources in a galaxy, with only a low number of galaxies classified as AGNs. Both field and cluster galaxies follow the "Main-Sequence" of star forming galaxies, with no substantial difference observed between the two populations. In the Mass - Metallicity (MZ) plane, both high mass field and cluster galaxies (9:5 < log(M=M ) < 11) vii show comparable (O/H)s to the local SDSS mass-metallicity relation, with an offset of low mass galaxies (8:4 < log(M=M ) < 9:5) towards higher metallicities than the local MZR. We use the location of galaxies in projected phase-space to distinguish between accreted cluster galaxies, which possibly form the virialised population, and infalling galaxies, which have just been recently accreted into the cluster. Our sample of cluster galaxies is located, in projection, close to the cluster core, at radial distances lower than 2·R200. When investigating the chemical histories of the galaxies, we find the following: while both the metallicities of accreted and infalling galaxies are comparable at all masses, accreted cluster galaxies show more enhanced metallicities, by a factor of 0:07 dex, with a ∼ 1:9σ significance, than the population of field galaxies at the low mass end. The same can be said for the population of infalling cluster galaxies. The high mass galaxies are all in