Pasadena Postdoc Retreat Abstracts

Lei Bai	Is the Group Environment a Special Place for Galaxy Evolution? The star forming fraction of galaxies has been shown to anti-correlate with the density of the environment they reside in. However, the specific mechanisms that cause this trend are not clearly known. Many studies suggest the group environment might be the special place where this environmental transformation occurs, causing galaxies to be pre-processed before they fall into clusters. To confirm this speculation, we have carried out a multi-wavelength study of a well-selected group sample at z=0.06. I will briefly talk about the results based the first 9 groups in our sample.
Alyson Brooks	Simulating Realistic Disk Galaxies I will show movies of the latest results from a set of cosmological N-body simulations that form individual spiral galaxies. I will briefly demonstrate how both increased resolution and a physically motivated prescription for supernovae feedback are necessary to overcome long-standing problems with past CDM disk galaxy simulations. Finally, I will highlight my recent work utilizing these simulations, demonstrating that cold gas accretion into galaxies allows for the growth of stellar disks at much higher redshift than predicted by the standard model.
Kuenley Chiu	Quasars beyond the epoch of reionization: are we there yet? are we there yet? are we there yet? Abstract TBA
Michelle Cluver	Strange Company : The Galaxy and the Group I will discuss the unusual properties of the luminous infrared galaxy, HIZOA J0836-43, and the compact group, Stephan's Quintet. These very different systems, some would call them freaks, display an "unexpected" combination of emission characteristics. What does this tell us about their composition and/or physical state? My aim is to convince you that these astrophysical freaks are interesting because they challenge our understanding of the underlying physics and have application to diverse astrophysical systems.
Dan Coe	Cosmological Constraints from Gravitational Lens Time Delays Tighter constraints on Hubble's constant (H0) will yield tighter constraints on both the dark energy equation of state parameter (w) and the flatness of our universe (k), independently of the results of future dark energy surveys. At long last, strong lensing time delays have begun to realize their potential as cosmological rulers capable of constraining H0. Recent analyses of lens ensembles yield H0 values in agreement with and to roughly the same level of precision (10%) as the HST Key Project. These results were obtained with only 16 lenses, but future surveys are expected to yield hundreds or even thousands of lenses with well-measured time delays. Thus we can expect this method to soon yield very competitive constraints on H0. Alternatively, if strong priors are placed on H0, other cosmological parameters may be well constrained. We present new simulations which quantify the levels of precision expected both from proposed surveys and from a proposed decidated space-based observatory.
Kelle Cruz	Brown Dwarfs Abstract TBA
Sally Dodson-Robinson	The Formation of the ultra-dense planet HD 149026b Abstract TBA
Louise Edwards	ABELL 1763 - Multiwavelength observations of star formation in the cluster core and filament Abell 1763 is a nearby rich galaxy cluster (z~0.2). Using Spitzer MIPS data we have recently discovered galaxies in a filament that connects this cluster to the neighbouring Abell 1770. This filament shows an excess of star forming galaxies relative to the cluster core. We present Optical, NIR, MIR (and, depending on how our upcoming VLA run pans out), Radio observations which further quantify our original discovery.
Julian van Eyken	The Exoplanet Tracker Project The Exoplanet Tracker project is based on dispersed fixed-delay interferometry, a new instrument concept for high-precision radial velocity surveys for extrasolar planets. A combination of an interferometer in series with a medium resolution spectrograph, it has the potential for performing multi-object surveying down to faint magnitude limits, where previous radial velocity techniques have been limited to observing only one target at at time. This technique provides the basis for the MARVELS exoplanet survey, which will be one of the pillars of SDSS III. I will briefly outline the concept, and talk about some interesting results from the preliminary surveys.
Janice Hester	Dark Matter Halo Mergers in the Millennium Simulation - Dependence on Environment I will briefly present the results of a study of the specific major merger rate as a function of group membership, local environment, and redshift in a very large, 500h−1 mpc, cosmological N-body simulation, the Millennium Simulation. The results from the simulation suggest a physical picture of how tidal stripping, dynamical friction, and inelastic unbound collisions between subhalos interact to drive the major merger rate. The goal of this work is to provide environmental diagnostics of major merger populations in order to test simulations against observations and provide further constraints on major merger driven galaxy evolution scenarios. I will present observational predictions that are based on our results.
Inese Ivans	Galaxy construction and evolution -- the perspective from stellar chemical compositions Abstract TBA
Eric Jullo	Gravitational lensing and the matter power spectrum The 2deg HST/COSMOS weak lensing project led by JPL-Caltech can be considered as a preparation to future space missions like JDEM/Euclid. Weak lensing techniques used so far are intrinsically limited to the analysis of large scale structures. In this talk, I present a new method that combines strong and weak lensing to extend the analysis of the matter power spectrum to small scale structures. The method also allows to introduce prior knowledge in a Bayesian way, such as stellar mass and X ray hot gas distribution, in order to separate the baryonic and non-baryonic components of the power spectrum.
Michael Kesden	Competitive Black Hole Growth in Bulgeless Disk Galaxies Recent observations and theoretical developments suggest that tight relations exist between the mass of a supermassive black hole and the properties of the spheroidal component of its host galaxy. These correlations call into question whether a bulgeless disk galaxy lacking a genuine spheroidal component can host a supermassive black hole, as do HST observations placing an upper limit of 1500 solar masses on the black hole at the center of the nearby pure disk galaxy M33. Here we use a simple semianalytic model to explore the competitive grown of a supermassive black hole, galactic disk, and nuclear star cluster in the host galaxy's dark matter halo. We place constraints on galactic star formation and accretion histories consistent with the absence of a supermassive black hole.
Nick Konidaris	Tiny Star Formation Rates in z~0.8 Massive Red Early Type Galaxies Massive (more luminous than L*), red sequence, early type galaxies are typically thought to have little ongoing star formation. Yet classic signatures of star formation are present including the [O II] 3727 emission line. Using arguments from line ratios and emission line kinematics, I'll argue that the ionizing source of the emission is likely not star formation or even AGN activity. My talk will then switch gears and focus on the new multi object near-infrared spectrograph, MOSFIRE, for the Keck telescope. MOSFIRE will be tremendously useful for nailing down the ionization source of emission lines in early type galaxies. I'll present the spectrograph, its capabilities, and show pictures of MOSFIRE in the lab.
Shri Kulkarni	SDSS: A Laboratory for Future Survey Machines The Sloan Digital Sky Survey (SDSS) is widely considered as a most successful story. Future and futuristic surveys appeal to the success of SDSS in justifying their project. In view of this I have undertaken a modestly objective study of the impact of SDSS as a purely photometric survey (p), as a survey with massive spectroscopy (z) and as a survey which inspired follow up (f). I will present my analysis of the impact of SDSS in these three categories (p,z,f) and thereby anchor the claims of the future surveys.
Ivo Labbé	Near-IR medium band imaging of massive distant galaxies Deep near-infrared imaging surveys have enable us to select and study distant galaxies in the rest-frame optical, transforming our knowledge of the early Universe. As the vast majority of K- or IRAC-selected galaxies are too faint for spectroscopy, the interpretation of these surveys relies almost exclusively on photometric redshifts determined from the broadband photometry. The best-achieved accuracy of these redshifts (typically dz/(1+z)~0.05) is insufficient for measuring accurate rest-frame colors, stellar population parameters, or the local galaxy density. I will present the first results of a new large survey with NEWFIRM on the Kitt Peak 4-m telescope employing medium band surveys in the near-infrared. The medium-width filters unambiguously pinpoint the location of the redshifted Balmer break in galaxies at z=1.5-3.5, enabling accurate redshift measurements and much improved determinations of their stellar populations and masses.
Karín Menéndez- Delmestre	The Luminous, the Massive and the Dusty: a Near- to Mid-Infrared Spectroscopic Study of Submillimeter Galaxies Ultra-luminous infrared galaxies (ULIRGs; L > 1012 Lsun) are quite rare in the local universe, but appear to dominate the commoving energy density at z>2. Many are optically-faint, dust-obscured galaxies that have been identified only relatively recently by the detection of their thermal dust emission redshifted into the submillimeter wavelengths. For the past few years I have worked on the near- to mid-IR spectral properties of these submillimeter galaxies (SMGs). I will give a brief overview of my work, including the first integral field AO view of SMGs and a summary of the mid-IR properties of SMGs as seen by the Spitzer Infrared Spectrograph.
Iva Momcheva	Environments of Strong Gravitational Lenses Abstract TBA
Christian Ott	Core-Collapse Supernova Theory Abstract TBA
Masami Ouchi	Galaxy Formation and Reionization Probed with Lya Emitters Abstract TBA
Fang Peng	Electron-ion equilibration process in the intracluster medium Galaxy clusters grow hierarchically via mergers and accretions, which shock-heated ion particles in the intracluster medium efficiently to very high temperature. Electrons gain energy via Coulomb collision with ions. In the outer regions of galaxy clusters, the electron-ion equilibration timescale is longer than the age of the cluster, which causes colder electrons than ions. I will discuss how this process affects the Sunyaev-Zel'dovich effect signals.
Annika Peter	Astrophysical systematics for dark matter detection in the solar system Next-generation direct detection experiments and neutrino telescopes are expected to have several orders of magnitude better sensitivity to particle dark matter in the solar system than current experiments. The greatest uncertainty in the event rate for these experiments, other than the dark matter microphysics which we wish to glean from their measurements, is the local distribution of dark matter. I will describe the outstanding issues regarding the local dark matter distribution, and how the uncertainty in the dark matter distribution translates to the event rates.
Robert Quimby	Optical Transients in Nearby and Not-So-Nearby Galaxies Abstract TBA
Jesper Rasmussen	Now you see them, now you don't: Searching for hot accretion flows around spiral galaxies In classical models of galaxy formation and evolution, massive disk galaxies like the Milky Way acquire some of their material for continued star formation from external accretion of gas, which converts into a million-degree plasma when shock heated during infall in the galaxy's gravitational potential. Direct evidence for this hot material around nearby spirals has remained elusive, however. I will describe recent observational attempts at detecting these X-ray emitting accretion flows around massive spirals, and discuss some implications for our understanding of disk galaxy evolution.
Brian Siana	Clear Evidence for Evolution of the Escape Fraction of Lyman Continuum Photons It's thought that UV light from young starbursts is responsible for reionizing the universe at z>6. However, it's unclear how the ionizing photons escape the large HI column densities in these galaxies. Over the last decade, many studies have looked for escaping ionizing photons from starburst galaxies at z=0,1,3 and several groups have recently reported the first detections at z=3. I'll report on our HST program that gives the deepest escape fraction limits at any redshift. The large number of non-detections demonstrates for the first time that the average escape fraction is increasing with redshift, in agreement with recent numerical simulations.
Ali Vanderveld	Supernova lensing by voids Large-scale voids and the sheets of matter between them can impact the Hubble diagram that we measure from Type Ia supernovae, primarily through gravitational lensing. Thus it is important to know if such effects are large enough so as to significantly impact the cosmological inferences that we draw from these data. I will review recent theoretical work to quantify these effects using simple analytical models.
Yanling Wu	Mid-IR properties of Seyferts: Spitzer/IRS spectroscopy of the IRAS 12µm Seyfert Sample The study of Seyfert galaxies is of particular interest as they trace the build up of SMBH at the centers of galaxies and they are responsible for the most of the cosmic X-ray background at redshift z ∼0.8. Given the high obscuration of their nuclei by dust extinction, a large fraction of their emitted radiation is absorbed and reemitted in the infrared. It has been recently demonstrated that mid-infrared spectroscopy, in particular with ISO and Spitzer, is a powerful tool to probe the physics of the radiation ﬁeld of deeply enshrouded galactic nuclei. Here we present our analysis on the properties of Seyfert galaxies based mostly on our uniformly extracted low-resolution Spitzer/IRS 5.5-35micron spectra for 103 Seyfert galaxies, nearly 90% of the local 12µm IRAS Seyfert sample. We ﬁnd that we are able to disentangle the AGN/starburst contribution of the mid-IR emission, and estimate the circumnuclear star formation rate using typical mid-IR tracers. We also ﬁnd that the mid-IR properties of Type 1 and Type 2 Seyferts are indistinguishable at a given luminosiry range, placing constrains both on the infrared optical depth to their nuclei galaxies as well as to the applicability of the uniﬁed AGN model.