A MATURE DUSTY STAR-FORMING GALAXY HOSTING GRB 080607 AT z = 3.036

Preface. Part I: Radio quiet/loud dichotomy. Unification. The hosts galaxies of radio-loud and radio-quiet quasars J. Dunlop. The Nucleus-Host Galaxy Connection in Radio-Loud AGN M. O'Dowd, et al. The host galaxies of luminous radio-quiet quasars W.J. Percival, et al. The radio loudness dichotomy: environment or black-hole mass? R. McLure, J. Dunlop. QSO environments at intermediate redshifts M. Wold, et al. Host galaxies and cluster environment of BL Lac objects at z > 0.5 J. Heidt, et al. Associated absorption and radio source growth J.C. Baker. Host galaxies of RGB BL Lacertae objects K. Nilsson, et al. On the Parent Population of Radio Galaxies and the FR I-II Dichotomy R. Scarpa, C.M. Urry. The real difference between radio-loud and radio-quiet AGNs A. Sillanpaa. Broadband optical colours of intermediate redshift QSO host galaxies E. Orndahl, J. Ronnback. Three peculiar objects from a new sample of radio galaxies L. Lara, et al. Part II: QSO redshift evolution and their cluster environments. QSO hosts and companions at higher redshift J.B. Hutchings. The luminosity function of QSO host galaxies L. Wisotzki, et al. QSO host galaxy star formation history from multicolour data K. Jahnke, et al. Near-infrared imaging of steep spectrum radio quasars J.K. Kotilainen, R. Falomo. Adaptive-optics imaging of low and intermediate redshift quasars I. Marquez, et al. Subaru Observations of the Host Galaxies and the Environments of the Radio Galaxy 3C324 at z = 1.1 T. Yamada. Extremely red radio galaxies C.J. Willott, et al. The environments of radio-loud quasars J.M. Barr, et al. Extended X-ray emission around radio-loud quasars M.Hardcastle. WFPC2 Imaging of Quasar Environments R.A. Finn, et al. Deceleration and asymmetry in QSO radio map S. Rys. Spatially resolved spectroscopy of emission-line gas in QSO Host galaxies A.I. Sheinis. Host Galaxies and the Spectral Variability of Quasars F. Vagnetti, D. Trevese. Part III: Tidal Interactions/Mergers. ULIRGS. The AGN-Starburst Connection in Ultraluminous Infrared Galaxies M. Rowan-Robinson. The QSO -- Ultraluminous Infrared Galaxies Connection S. Veilleux, et al. Recent star formation in very luminous infrared galaxies A. Bressan, et al. A Molecular Gas Survey of z < 0.2 Infrared Excess, Optical QSOs A.S. Evans, et al. Molecular gas in nearby powerful radio galaxies S. Leon, et al. HI Imaging of low-z QSO Galaxies J. Lim, et al. Dust in Quasars and Radiogalaxies as seen by ISO S.A.H. Muller, et al. Imaging of a Complete Sample of IR-Excess PG QSOs J.A. Surace, D.B. Sanders. Interaction patterns in a complete sample of compact groups V. Zitelli, et al. Part IV: Galaxies hosting lower level AGN activity. AGN Host galaxies: H ST at z ~ 0.1 and Gemini at z ~ 2 D. Schade, et al. Host galaxies and nuclear structure of AGN with H2O megamasers as seen with H ST H. Falcke, et al. Statistics of Seyfert galaxies in clusters B. Kelm, P. Focardi. More Bars in Seyfert than in non-Seyfert galaxies J.H. Knapen, et al. Stellar Populations in the Host galaxy of AGNs M. Joly, et al. The Stellar Population of powerful Seyfert 2 galaxies: Implications for QSOs R.M.G. Delgado. Anisotropy in the mid-IR emission of Seyfert galaxies A.M.P. Garcia, J.M.R. Espinosa. FIR and

In this thesis I study the gas distribution and dynamics, as well as the stellar populations, in the circumnuclear star forming rings in the nearby barred galaxies NGC5248 and NGC6951. Circumnuclear star forming rings are regions of high gas and star formation density in the centers of disk galaxies. These star formation rings can have a strong influence on the secular evolution of their host galaxies, by halting gas inflow towards the nucleus. The gas masses that build up in these rings are high and this consequently leads to intense star formation. This makes circumnuclear star forming rings also an important tool to build up the stellar (pseudo-)bulge. These two galaxies were selected because they have very similar global properties (mass, size, metallicity), but very different circumnuclear regions, both of which containing circumnuclear star forming rings. Detailed investigation of both, and a comparison between them, thus provides new detailed insight on the interplay between circumnuclear star forming rings and the circumnuclear region as a whole. Three questions are addressed in this work. First of all, I investigate the true effectiveness of the circumnuclear rings as a gas barrier in both galaxies. I study star formation progression in these rings and its relation to the gas flow onto the ring. The age and life span of the circumnuclear rings is derived from the analysis of their stellar populations. In both galaxies I find that while the circumnuclear rings are effective barriers, they are not absolute ones. The interplay between the large scale stellar bar, circumnuclear ring and other dynamical components in the circumnuclear region allows some gas to flow towards the very center past the ring. I find that the location of the youngest stars in the ring is close to the inflow position of the gas onto the ring in both galaxies, consistent with star formation proceeding in a ’pearls-on-a-string’ mechanism with the youngest ’pearls’ close to the gas inflow location. Finally, I derive ages of the rings around 1.5 Gyr, which implies that circumnuclear star forming rings have a significant amount of time to shape the circumnuclear regions of their host galaxies.

We present near-infrared spectroscopy of the host galaxy of the dark gamma-ray burst (GRB) 080325 using Subaru/Multi-Object Infrared Camera and Spectrograph. The obtained spectrum provides a clear detection of Hα emission and marginal [Nii]λ6584. The host is a massive (M_* ~ 10^(11) M_⊙), dusty (A_V ~ 1.2) star-forming galaxy at z = 1.78. The extinction-corrected star formation rate (SFR) calculated from the Hα luminosity (35.6–47.0 M_⊙ yr^(−1)) is typical among GRB host galaxies (and star-forming galaxies generally) at z>1; however, the specific SFR is lower than for normal star-forming galaxies at redshift ~1.6, in contrast to the high specific SFR measured for many of other GRB hosts. The metallicity of the host is estimated to be 12 + log(O/H)_(KK04) = 8.88. We emphasize that this is one of the most massive host galaxies at z>1 for which metallicity is measured with emission-line diagnostics. The metallicity is fairly high among GRB hosts, however, this is still lower than the metallicity of normal star-forming galaxies of the same mass at z ~ 1.6. The metallicity offset from normal star-forming galaxies is close to a typical value of other GRB hosts and indicates that GRB host galaxies are uniformly biased toward low metallicity over a wide range of redshifts and stellar masses. The low-metallicity nature of the GRB 080325 host likely cannot be attributed to the fundamental metallicity relation of star-forming galaxies because it is a metal-poor outlier from the relation and has a low specific star formation rate. Thus, we conclude that metallicity is important to the mechanism that produced this GRB.

A remarkable fraction of supernovae (SNe) have no obvious host galaxy. Two possible explanations are that (i) the host galaxy is simply not detected within the sensitivity of the available data or that (ii) the progenitor is a hypervelocity star that has escaped its parent galaxy. We use the Type IIb SN 2009Z as a prototype of case (i), an example of how a very faint (here Low Surface Brightness; LSB) galaxy can be discovered via the observation of a seemingly host-less SN. By identifying and studying LSB galaxies that host SNe related to the death of massive stars, we can place constraints on the stellar population and environment of LSB galaxies, which at present are poorly understood. From an HI spectrum, a redshift of z = 0.02513+-0.00001 and an HI mass of (2.96+-0.12) 10^9 M_sun are computed. This redshift is consistent with that obtained from optical emission lines of SN 2009Z. Furthermore, a gas mass fraction of f_g = 0.87+-0.04 is obtained, one of the highest fractions ever measured. The host galaxy shows signs of recently enhanced star formation activity with a far-UV derived extinction-corrected Star Formation Rate (SFR) of 0.44+-0.34 M_sun/yr. Based on the B-band luminosity we estimate an extinction-corrected metallicity following the calibration by Pilyugin (2001) of 12 + log(O/H) = 8.24+-0.70. The presence of a Type IIb SN in an LSB galaxy suggests, contrary to popular belief, that massive stars can be formed in this type of galaxies. Furthermore, our results imply that LSB galaxies undergo phases of small, local burst activity intermittent with longer phases of inactivity.

We present new observational results that conclude that the nearby radio galaxy B2 0722+30 is one of the very few known disc galaxies in the low-redshift Universe that host a classical double-lobed radio source. In this paper we use HI observations, deep optical imaging, stellar population synthesis modelling and emission-line diagnostics to study the host galaxy, classify the Active Galactic Nucleus and investigate environmental properties under which a radio-loud AGN can occur in this system. Typical for spiral galaxies, B2 0722+30 has a regularly rotating gaseous disc throughout which star formation occurs. Dust heating by the ongoing star formation is likely responsible for the high infrared luminosity of the system. The optical emission-line properties of the central region identify a Low Ionization Nuclear Emission-line Region (LINER)-type nucleus with a relatively low [OIII] luminosity, in particular when compared with the total power of the Fanaroff & Riley type-I radio source that is present in this system. This classifies B2 0722+30 as a classical radio galaxy rather than a typical Seyfert galaxy. The environment of B2 0722+30 is extremely HI-rich, with several nearby interacting galaxies. We argue that a gas-rich interaction involving B2 0722+30 is a likely cause for the triggering of the radio-AGN and/or the fact that the radio source managed to escape the optical boundaries of the host galaxy.

We use optical integral field spectroscopy (IFS) of nearby supernova (SN) host galaxies (0.005 <z< 0.03) provided by the Calar Alto Legacy Integral Field Area (CALIFA) Survey with the goal of finding correlations in the environmental parameters at the location of different SN types. In this first study of a series we focus on the properties related with star formation (SF). We recover the sequence in association of different SN types to the star-forming regions by using several indicators of the ongoing and recent SF related to both the ionized gas and the stellar populations. While the total ongoing SF is on average the same for the three SN types, SNe Ibc/IIb tend to occur closer to star-forming regions and in higher SF density locations than SNe II and SNe Ia; the latter shows the weakest correlation. SNe Ia host galaxies have masses that are on average ~0.3−0.8 dex higher than those of the core collapse (CC) SNe hosts because the SNe Ia hosts contain alarger fraction of old stellar populations. Using the recent SN Ia delay-time distribution and the SFHs of the galaxies, we show that the SN Ia hosts in our sample are expected to produce twice as many SNe Ia as the CC SN hosts. Since both types occur in hosts with a similar SF rate and hence similar CC SN rate, this can explain the mass difference between the SN Ia and CC SN hosts, and reinforces the finding that at least part of the SNe Ia originate from very old progenitors. By comparing the mean SFH of the eight least massive galaxies with that of the massive SF SN Ia hosts, we find that the low-mass galaxies formed their stars during a longer time (0.65%, 24.46%, and 74.89% in the intervals 0–0.42 Gyr, 0.42–2.4 Gyr, and >2.4 Gyr, respectively) than the massive SN Ia hosts (0.04%, 2.01%, and 97.95% in these intervals). We estimate that the low-mass galaxies produce ten times fewer SNe Ia and three times fewer CC SNe than the high-mass group. Therefore the ratio between the number of CC SNe and SNe Ia is expected to increase with decreasing galaxy mass. CC SNe tend to explode at positions with younger stellar populations than the galaxy average, but the galaxy properties at SNe Ia locations are one average the same as the global galaxy properties.

We estimate the fraction of core-collapse supernovae (CCSNe) that remain undetected by optical SN searches due to obscuration by large amounts of dust in their host galaxies. This effect is especially important in luminous and ultraluminous infrared galaxies, which are locally rare but dominate the star formation at redshifts of z~1-2. We perform a detailed investigation of the SN activity in the nearby luminous infrared galaxy Arp 299 and estimate that up to 83% of the SNe in Arp 299 and in similar galaxies in the local Universe are missed by observations at optical wavelengths. For rest-frame optical surveys we find the fraction of SNe missed due to high dust extinction to increase from the average local value of ~19% to ~38% at z~1.2 and then stay roughly constant up to z~2. It is therefore crucial to take into account the effects of obscuration by dust when determining SN rates at high redshift and when predicting the number of CCSNe detectable by future high-z surveys such as LSST, JWST, and Euclid. For a sample of nearby CCSNe (distances 6-15 Mpc) detected during the last 12 yr, we find a lower limit for the local CCSN rate of 1.5 +0.4/-0.3 x 10^-4 yr^-1 Mpc^-3, consistent with that expected from the star formation rate. Even closer, at distances less than ~6 Mpc, we find a significant increase in the CCSN rate, indicating a local overdensity of star formation caused by a small number of galaxies that have each hosted multiple SNe.

We investigate the relationship between host galaxies’ stellar content and active galactic nuclei (AGNs) for optically selected QSOs with z &lt; 0.5. There is a total of 82 QSOs that we select from the Sloan Digital Sky Survey. These 82 QSOs have both Wide-field Infrared Survey Explorer data and measurable stellar content. With the help of the stellar population synthesis code STARLIGHT, we determine the luminosity fractions of AGNs, stellar population ages, and star formation histories (SFHs) of host galaxies. We find that there is a correlation between the SFH and AGN properties, which suggests a possible delay from star formation to AGN. This probably indicates that the AGN activity correlates with the star formation activity, which consistent with a coevolution scheme for black hole and host galaxies.

To investigate feedback between relativistic jets emanating from Active Galactic Nuclei (AGN) and the stellar population of the host galaxy, we analyze the long-term evolution of the galaxy-scale simulations by Gaibler et al. (2012) of jets in massive, gas-rich galaxies at z ~ 2 - 3 and of stars formed in the host galaxies. We find strong, jet-induced differences in the resulting stellar populations of galaxies that host relativistic jets and galaxies that do not, including correlations in stellar locations, velocities, and ages. Jets are found to generate distributions of increased radial and vertical velocities that persist long enough to effectively extend the stellar structure of the host. The jets cause the formation of bow shocks that move out through the disk, generating rings of star formation within the disk. The bow shock often accelerates pockets of gas in which stars form, yielding populations of stars with significant radial and vertical velocities, some of which have large enough velocities to escape the galaxy. These stellar population signatures can serve to identify past jet activity as well as jet-induced star formation.

Fast radio bursts (FRBs) are a powerful and mysterious new class of transients that are luminous enough to be detected at cosmological distances. By associating FRBs to host galaxies, we can measure intrinsic and environmental properties that test FRB origin models, in addition to using them as precise probes of distant cosmic gas. The Deep Synoptic Array (DSA-110) is a radio interferometer built to maximize the rate at which it can simultaneously detect and localize FRBs. Here, we present the first sample of FRBs and host galaxies discovered by the DSA-110. This sample of 11 FRBs is the largest, most uniform sample of localized FRBs to date, as it is selected based on association with host galaxies identified in optical imaging by Pan-STARRS1. These FRBs have not been observed to repeat, and their radio properties (dispersion, temporal scattering, energy) are similar to that of the known nonrepeating FRB population. Most host galaxies have ongoing star formation, as has been identified before for FRB hosts. Two hosts of the new sample are massive, quiescent galaxies. The distribution of star formation history across this host-galaxy sample shows that the delay time distribution is wide, with a power-law model that spans from ∼100 Myr to ≳2 Gyr. This requires the existence of one or more progenitor formation channels associated with old stellar populations, such as the binary evolution of compact objects.

‘Cometary’ Blue Compact Dwarf Galaxies (iI,C BCDs) are characterized by off-center starbursts close to the end of an elongated dwarf irregular (dI)-like host galaxy. This may either represent randomly enhanced star-forming activity of a dI, or may be caused by a set of special properties of such systems or their environment. For a first investigation of this issue, we analyse the nearby iI,C BCDs Markarian 59 and Markarian 71. Using deep ground-based spectrophotometric data and HST images, we derive physical properties, structure and ages of the starburst regions and the underlying stellar host galaxies. The metallicities show small scatter in the vicinity of the star-forming regions and along the major axis of Mrk 59 which suggests effective mixing of heavy elements on kpc scales. The surface brightness profiles of the underlying host galaxies in either iI,C BCD show an exponential decay with a central surface brightness and scale length that are intermediate between typical iE/nE BCDs and dls. Spectral population synthesis models in combination with colour magnitude diagrams and colour profiles yield most likely formation ages of ~2 Gyr for the host galaxies in both iI,C BCDs, with upper limits of ~4 Gyr for Mrk 59 and ~3 Gyr for Mrk 71, i.e. significantly lower than the typical age of several Gyr derived for the host galaxies of iE/nE BCDs. These findings raise the question whether iI,C systems form a distinct class within BCDs with respect to the age and structure of their hosts, or whether they represent an evolutionary stage connecting young i0 BCDs and ‘classical’ iE/nE BCDs. Properties of analogous objects studied in the local universe and at medium redshifts provide some support for this evolutionary hypothesis.

“Changing-look” active galactic nuclei (CL-AGNs) are a newly discovered class of AGNs that show the appearance (or disappearance) of broad emission lines within short timescales (months to years), and are often associated with dramatic changes in their continuum emissions. They provide us with an unprecedented chance to directly investigate the host galaxy properties with minimal contamination from the luminous central engine during the turn-off state, which is difficult for normal luminous AGNs. In this work, for the first time, we systematically characterize the stellar populations and star formation histories of host galaxies for 26 turn-off CL-AGNs using the stellar population synthesis code STARLIGHT. We find that the stellar populations of CL-AGNs are similar to those of normal AGNs, except that the intermediate stellar populations contribute more fractions. We estimate their stellar velocity dispersions (σ ⋆) and black hole masses (M BH,vir), and find that CL-AGNs also follow the overall M BH–σ ⋆ relationship. We also confirm the previous claims that CL-AGNs tend to be biased toward lower Eddington ratios, and that their extreme variabilities are more likely due to the intrinsic changes of the accretion rates. In addition, CL-AGNs with recent star formations tend to have higher Eddington ratios. Compared with previous studies, our analysis suggests that there may be a correlation between CL-AGN host galaxy properties and their CL phenomena.

We present the first comprehensive search for submillimeter and radio emission from the host galaxies of 20 well-localized gamma-ray bursts (GRBs). With the exception of a single source, all observations were undertaken months to years after the GRB explosions to ensure negligible contamination from the afterglows. We detect the host galaxy of GRB 000418 in both the submillimeter and radio, and the host galaxy of GRB 000210 in only the submillimeter. These observations, in conjunction with the previous detections of the host galaxies of GRB 980703 and GRB 010222, indicate that about 20% of GRB host galaxies are ultraluminous (L > 1012 L☉) and have star formation rates of about 500 M☉ yr-1. As an ensemble, the nondetected hosts have a star formation rate of about 100 M☉ yr-1 (5 σ) based on their radio emission. This, in conjunction with an average luminosity for the entire sample that is approximately 20% fainter than the local starburst galaxy Arp 220, indicates that GRB hosts probe a more representative population of star-forming galaxies than those uncovered in blank submillimeter and radio surveys. The detected and ensemble star formation rates exceed the values determined from various optical estimators by an order of magnitude, indicating significant dust obscuration. In the same vein, the ratio of bolometric dust luminosity to UV luminosity for the hosts detected in the submillimeter and radio bands ranges from about ~30 to 500 and follows the known trend of increasing obscuration with increasing bolometric luminosity. We also show that the GRB host sample as a whole, and the submillimeter- and radio-detected hosts individually, have significantly bluer R-K colors as compared with galaxies selected in the submillimeter and radio in the same redshift range. This possibly indicates that the stellar populations in the GRB hosts are on average younger, supporting the massive stellar progenitor scenario for GRBs, but it is also possible that GRB hosts are on average less dusty. For the nondetected GRB hosts, the difference in R-K color may also be a manifestation of their more representative bolometric luminosities relative to the highly luminous submillimeter- and radio-selected galaxies. Beyond the specific results presented in this paper, the submillimeter and radio observations serve as an observational proof-of-concept in anticipation of the upcoming launch of the Swift GRB mission and SIRTF. These new facilities will possibly bring GRB host galaxies into the forefront of star formation studies.

The host of the short gamma-ray burst (GRB) 050709 is a morphologically disturbed low-luminous galaxy. At a redshift of z = 0.16, it belongs to one of the cosmologically nearest short-GRB hosts identified to date. Consequently, it represents a promising target for sensitive, spatially resolved observational studies. We have used the Multi Unit Spectroscopic Explorer (MUSE) mounted at the Very Large Telescope to characterize the GRB host galaxy. In addition, we performed deep radio-continuum observations of the host with the Australia Telescope Compact Array (ATCA) and with ALMA at 1.3 mm. Moreover, we made use of archival Spitzer Space Telescope 24 μm and Hubble Space Telescope/F814W imaging data of this galaxy. The spatially resolved MUSE data reveal that the entire host is a source of strong line emission, in particular from Hα and [O III] λ 5007, superimposed on a rather weak stellar continuum. Using the Balmer decrement, we map the internal host-galaxy reddening and derive an extinction-corrected star formation rate based on the flux in the Hα line of 0.15 ± 0.02 M⊙ yr−1. The galaxy is detected neither by ALMA nor by Spitzer, excluding a substantial amount of optically obscured star formation activity. Using the O3N2 metallicity indicator, we measure an average 12 + log (O/H) = 8.40 ± 0.05 (corresponding to ∼0.5 solar). Diagnostic emission line diagrams show that a substantial fraction of all MUSE spaxels that cover the GRB 050709 host galaxy lie close to the star-formation demarcation line. Some spaxels even suggest line emission by shocked gas. The ATCA observations reveal faint diffuse radio emission at the eastern part of the host in excess to that expected from pure star formation, possibly further evidence for nonthermal processes. The kinematics of the Hα-emitting gas suggests a rotationally supported host-galaxy system, apparently in contrast to its irregular photometric morphology. A comparison with the field-galaxy population reveals, however, that the kinematics of the gas in the 050709 host fits into the ensemble of merging galaxies well. Finally, we use the ATCA radio data to set deep constraints on any late-time flux from the GRB afterglow or a potentially associated kilonova radio flare ∼10 years after the burst.

(ABRIDGED) We show that Type Ia supernovae (SNe Ia) are formed within both very young and old stellar populations, with observed rates that depend on the stellar mass and mean star-formation rates (SFRs) of their host galaxies. Models where the SN Ia rate depends solely on host galaxy stellar mass are ruled out with 99% confidence. Our analysis is based on 100 spectroscopically-confirmed SNe Ia, plus 24 photometrically-classified events, all from the Supernova Legacy Survey (SNLS) and distributed over 0.2<z<0.75. Using multi-band photometry, we estimate stellar masses and SFRs for the SN Ia host galaxies by fitting their broad-band spectral energy distributions with the galaxy spectral synthesis code, PEGASE.2. We show that the SN Ia rate per unit mass is proportional to the specific SFR of the parent galaxies -- more vigorously star-forming galaxies host more SNe Ia per unit stellar mass, broadly equivalent to the trend of increasing SN Ia rate in later-type galaxies seen in the local universe. Following earlier suggestions for a simple two-component model approximating the SN Ia rate, we find bivariate linear dependencies of the SN Ia rate on both the stellar masses and the mean SFRs of the host systems. We also demonstrate a dependence of distant SN Ia light-curve shapes on star-formation in the host galaxy, similar to trends observed locally. Passive galaxies, with no star-formation, preferentially host faster-declining/dimmer SNe Ia, while slower-declining/brighter events are only found in systems with ongoing star-formation. We model the light-curve width distribution in star-forming galaxies as the sum of a young component, and an old component taken from the distribution in non-star-forming galaxies.