Prof.
John O'Meara
(Saint Michael's College)
24/06/2013, 09:30
Invited Talk
Mr
Marcel Neeleman
(UCSD)
24/06/2013, 10:10
Contributed Talk
The study of the high redshift universe through quasar absorption lines allows us to measure in great detail the properties of the gas that is responsible for the absorption. Damped Lyα systems, DLAs, the largest of these absorbers, are intimately linked to the predecessors of modern-day galaxies, and their study provide insight into how galaxies form and evolve. In this talk, I will review...
Mr
Ali Rahmati
(Leiden Observatory)
24/06/2013, 10:40
Contributed Talk
In this talk, I will show that cosmological simulations of galaxy formation that match the cosmic star formation history are also capable of reproducing the observed HI distribution when they are combined with accurate radiative transfer calculations. I will discuss the impact of different ionizing processes (i.e., the UV background, recombination radiation, collisional ionization and local...
Dr
Michele Fumagalli
(Carnegie Observatories/Princeton University)
24/06/2013, 11:40
Invited Talk
Already from the first quasar surveys, it became evident that Lyman limit systems (LLSs) differ from the Lyα forest and are likely associated to galaxies. Recently, this idea has received renewed attention because of the proposed connection between LLSs and the so-called "cold streams" that are postulated to feed star forming galaxies at z>2. In this talk, I will present results from a new...
Dr
Khee-Gan Lee
(MPIA)
24/06/2013, 12:20
Contributed Talk
The BOSS Lyα forest survey is obtaining Lyα forest sightlines for over 160,000 QSOs at z>2. While the signal-to-noise and resolution is moderate, I will show that it is possible to obtain information on the IGM temperature-density relation by measuring the flux PDF from the BOSS Lyα forest data. I will discuss new methods for continuum-estimation, noise- and metal-modelling that allow us to...
Prof.
Philipp Richter
(University of Potsdam)
24/06/2013, 14:20
Invited Talk
Dr
Benjamin Oppenheimer
(Leiden University)
24/06/2013, 15:00
Invited Talk
Dr
Richard Bielby
(Durham University)
24/06/2013, 15:40
Contributed Talk
We present results from the VLT LBG Redshift Survey (VLRS), probing the HI distribution around z ~ 3 galaxies. The VLRS consists of ~ 2,000 galaxy redshifts at z > 2 in the foreground of bright QSOs with pre-existing high-resolution spectra. We have further added to the QSO sample within our survey fields by identifying and observing fainter QSOs with X-Shooter. We present the widest area...
Dr
Matthew Pieri
(ICG, Portsmouth)
24/06/2013, 16:40
Contributed Talk
We present results from stacking Lyα forest absorbers in the BOSS sample to achieve a variety of goals. Chief among them is the measurement of metals in the intergalactic medium (IGM) associated with the forest using various transitions, including several elements and species only seen using this technique. Metals in the IGM provide a valuable tracer of mechanical feedback - a crucial...
Ms
Monica Turner
(Leiden Observatory)
24/06/2013, 17:10
Contributed Talk
We study the distribution of metals spanning a large range of ionization energies (from SiIII to OVI) in the circumgalactic medium, through a sample ~700 star-forming z~2.4 galaxies selected from the Keck Baryonic Structure Survey. Using 15 hyper-luminous background quasars, we search for metals in absorption near galaxies, in order to make 2D metal maps by taking the median optical depth in...
Dr
David Syphers
(University of Colorado, Boulder)
25/06/2013, 09:30
Invited Talk
The reionization of He II at z~3 was the last major change in the ionization state of the IGM. In addition, the reionization of He II may also aid theoretical understanding of the later stages of hydrogen reionization. In recent years we have dramatically increased the number of He II Gunn-Peterson trough observations. Previously there were only two Gunn-Peterson observations at medium...
Dr
Wei Zheng
(Johns Hopkins University)
25/06/2013, 10:10
Contributed Talk
From the HST/COS spectra of selected quasars at z~>3.5, we find significant flux blueward of the HeII Lyα wavelength. The absorption profile suggests large "bubbles" of ionized helium embedded in the intergalactic medium. We find that the intensity of He+ ionizing field weakens considerably at z~3, and the reionization of the intergalactic helium started around z=3.5.
Dr
Gabor Worseck
(Max-Planck-Institut für Astronomie)
25/06/2013, 10:40
Invited Talk
The advent of GALEX and HST/COS have revolutionized studies of HeII reionization. In HST Cycle 17 we pioneered an effective strategy to statistically probe the HeII reionization epoch with HST/COS spectroscopy of the UV-brightest quasars. The clear picture emerging from the 13 sightlines probing z<3 is that HeII reionization likely ended at z~2.7. At z>2.7 the large scatter in the mean HeII...
Dr
Matthew McQuinn
(UC Berkeley)
25/06/2013, 11:50
Invited Talk
I will discuss the impact of intensity fluctuations on HI and HeII Lyα forest data. This will include a summary of recent work to measure and model eta fluctuations in the z~2.5 HeII Lyα forest and its implications for the sources of the UV background. In addition, I will summarize what numerical simulations plus radiative transfer predict for the abundance of z>3 HI Lyman-limit systems, and a...
Mr
Frederick Davies
(UCLA)
25/06/2013, 12:30
Contributed Talk
The standard cosmological radiative transfer method used to estimate the He II ionizing background assumes a uniform radiation field despite the discrete nature of the (rare) bright quasars that dominate the background. We estimate, for the first time, the effects of fluctuations on the evolving continuum opacity in two ways: by incorporating the complete distribution of ionizing background...
Dr
Luca Graziani
(Max Planck Institute for Astrophysics - MPA Garching)
25/06/2013, 14:30
Contributed Talk
The helium reionisation and the cosmic UV background (UVB) at z=3 have been investigated in recent years both theoretically and observationally. Spatial fluctuations of the eta parameter in the Lyα forest show that the He II opacity is “patchy” and a theoretical modelling of the UVB spectral shape is necessary to constrain these fluctuations. Metal ions in the IGM help constraining the UVB...
Dr
Sebastiano Cantalupo
(UCSC)
25/06/2013, 16:00
Invited Talk
I will present the result of a an ongoing, successful program that uses a new approach to directly detect and study cosmic gas in the early Universe: the key idea is to use an external ``source of illumination’’, a bright quasar, to light up with fluorescent Lyα emission dark, proto- galactic clouds and dense streams around galaxies in a large cosmological volume. In the first part of the...
Dr
Marc Rafelski
(IPAC (Caltech))
25/06/2013, 16:40
Contributed Talk
We present chemical abundance measurements for damped Lyα systems (DLAs) at z>4, which show a clear decrease in the metallicity of DLAs with increasing redshift. We find a possible break in the metallicity evolution of DLAs at z>4.7, and showcase our latest results using new Keck ESI and Magellan FIRE spectra. This break may represent a transition in the nature of DLAs, where high redshift...
Prof.
Jordi Miralda-Escudé
(ICREA, Barcelona)
26/06/2013, 09:30
Invited Talk
The Baryon Oscillations Spectroscopic Survey of SDSS-III has opened a new era for high-redshift large-scale structure surveys using spectra of intervening absorption. On large scales, the 3D redshift space linear power spectrum can be measured, as modified with two bias parameters for the Lyα forest, for density and peculiar velocity gradient. On small scales, the detailed physics of the...
Dr
Nicolás Busca
(Laboratoire AstroParticules Cosmologie - CNRS)
26/06/2013, 10:10
Invited Talk
Dr
Andreu Font-Ribera
(University of Zurich)
26/06/2013, 10:50
Invited Talk
The Baryon Oscillation Spectroscopic Survey (BOSS) uses the SDSS telescope to obtain spectra of 1.5 million galaxies to get a very accurate measurements of the BAO scale at redshift z ~0.5. Roughly a 20% of the fibers of the spectrograph, however, are pointing to high redshift quasars with the idea of detecting the BAO also in the clustering of gas responsible for the Lyα absorption present in...
Dr
Matteo Viel
(INAF)
26/06/2013, 12:00
Invited Talk
I will present new measurements of cold dark matter coldness by using a set of high resolution quasar spectra.
Dr
Tom Theuns
(Durham University)
26/06/2013, 12:40
Invited Talk
I will present some recent results on IGM simulations, including statistics of strong absorbers, and the effect of WDM.
Dr
Ryan Cooke
(UC Santa Cruz)
26/06/2013, 13:20
Contributed Talk
We are currently in an exciting era of precision cosmology. With the release of the cosmic microwave background data recorded by the Planck satellite, we are now in a position to accurately test the standard model of Big Bang Nucleosynthesis. In this talk, I will present a new, precise measure of the primordial abundance of deuterium - the most accurate measurement to date - derived from a...
Prof.
Hsiao-Wen Chen
(The University of Chicago)
27/06/2013, 09:30
Invited Talk
I will review observations of the circumgalactic medium at low and high redshifts based on absorption spectroscopy, and present new resolved velocity maps of the CGM at intermediate redshifts.
Prof.
John Stocke
(CASA, U. of Colorado)
27/06/2013, 10:10
Contributed Talk
The Science Team for the Cosmic Origins Spectrograph (COS) has conducted a modest-sized survey of QSOs near very low-z galaxies to characterize gaseous galaxy halos. We have found that high (~100%) covering factors in Lyα absorption extend at least out to the virial radius for L>0.1L* galaxies. Standard photo-ionization modeling of these absorbers finds cloud sizes of 1—30 kpc, masses of...
Dr
Charles Danforth
(University of Colorado)
27/06/2013, 10:45
Contributed Talk
The Cosmic Origins Spectrograph on HST has been in operation for nearly four years and has accumulated a library of ~400 AGN sight lines. Many of these are suitable for probing the low-redshift IGM for HI (Lyα forest) and metal-ion absorbers. The result is an unprecedented view of the local (z<1) IGM several times larger and more sensitive than previous surveys. I will present initial results...
Dr
Neil Crighton
(MPIA)
27/06/2013, 11:45
Contributed Talk
I will present observations of the distribution and covering fraction of metal-enriched gas around star-forming galaxies at redshift ~2.5. Using high resolution spectra of background quasars at impact parameters from ~70 to 300 kpc from foreground galaxies, we have measured precise column densities from both cool ~10^4 K and hotter ~10^5 K gas. We compare our results to those for star-forming...
Mr
Nicolas Tejos
(Durham University)
27/06/2013, 12:15
Contributed Talk
I will present observational results on the large-scale connection between the Intergalactic medium (IGM) and galaxies at z<1. I will focus on a statistical approach to this problem by measuring the gas-galaxy 2-point cross-correlation, and comparing it with both the galaxy-galaxy and the gas-gas auto-correlations, as a function of different absorber/galaxy properties. These results come from...
Dr
George Becker
(University of Cambridge)
27/06/2013, 14:15
Invited Talk
Reconciling our current constraints on hydrogen reionization with what we know about high-redshift galaxy populations points to interesting galaxy physics at early times. For example, in order to emit enough ionizing photons to complete reionization by z=6, it appears that faint sources must make a larger than expected contribution to the ionizing budget at z > 6, or else reionization galaxies...
Ms
Elisa Boera
(Swinburne University)
27/06/2013, 14:55
Contributed Talk
The HeII reionization is expected to leave a “footprint” on the thermal history of the IGM: a peak in the temperature evolution at the mean density. So far no clear evidence for this mark has been found and recently it has been suggested that new volumetric heating processes, from blazar emission, could dominate the photo-heating at z<3. These processes would obscure the peak due to the HeII...
Mr
Alberto Rorai
(Max Planck Institute for Astronomy - Heidelberg)
27/06/2013, 15:25
Contributed Talk
The small scale structure of the IGM, quantified by the Jeans filtering scale, has fundamental cosmological implications. On the one hand, it provides a thermal record of the heat injected by UV photons during cosmic reionization events, and its value thus constrains the thermal and reionization history of the Universe. On the other hand, it sets the minimum mass scale for gravitational...
Dr
Keri Dixon
(University of Sussex)
27/06/2013, 16:25
Contributed Talk
Recent HeII Lyα forest observations from 2.0 < z < 3.4 show large fluctuations in the optical depth at z > 2.7. These results point to a fluctuating HeII-ionizing background, possibly due to the end of helium reionization. We present a fast, semi-numeric procedure to approximate detailed cosmological simulations. Spanning a large parameter space, we find order-of-magnitude fluctuations in the...
Mr
Michele Compostella
(Argelander Institute for Astronomy, Bonn)
27/06/2013, 16:55
Contributed Talk
I will present results on the topology of HeII reionization obtained from AMR hydrodynamic simulations of the intergalactic medium post-processed with the radiative transfer code RADAMESH. Ionizing radiation is propagated from a realistic population of active galactic nuclei considering different scenarios for the time evolution of the ionizing sources. During the early phases of the...
Prof.
Todd Tripp
(University of Massachusetts)
28/06/2013, 09:30
Invited Talk
Theoretical studies have raised a number of important questions about the roles of gas inflows (accretion) and outflows (feedback) in galaxy evolution. Unfortunately, galactic gas flows are likely to have low densities and hence are difficult to observe with most techniques. However, QSO absorption lines provide sensitive observational probes of galactic flows, and the recent deployment of the...
Prof.
Varsha Kulkarni
(University of South Carolina)
28/06/2013, 10:10
Contributed Talk
Quasar absorption lines offer powerful probes to study the circumgalactic medium and the intergalactic medium. The gas-rich damped Lyα (DLA) and sub-DLA absorbers allow an especially detailed study of metals, gas, and dust in the circum-galactic medium. Most past studies of chemical composition of the absorbers focused on DLAs, rather than sub-DLAs. But recent studies by our team and others...
Dr
Sijing Shen
(University of California, Santa Cruz)
28/06/2013, 11:10
Invited Talk
I will present results on the kinematics, thermal and ionization state and spatial distribution of metal-enriched gas in the circumgalactic medium (CGM) of galaxies of different mass scales, using two suites of very high resolution cosmological hydrodynamic “zoom-in” simulations from Milky Way-like scales to (“Eris”) down to dwarf galaxies. The runs adopt a blastwave scheme for supernova...
Dr
Claudio Dalla Vecchia
(MPE)
28/06/2013, 11:50
Invited Talk
