Could AGN Outbursts Transform Cool Core Clusters? (2009)
The origin of the bimodality in cluster core entropy is still unknown. At the same time, recent work has shown that thermal conduction in clusters is likely a time-variable phenomenon. We consider if...
Cosmology from the Highly-Redshifted 21 cm Line (2009)
Furlanetto, Steven, Lidz, Adam, Loeb, Abraham, McQuinn, Matthew, Pritchard, Jonathan, Shapiro, Paul, ...
One of the next decade's most exciting prospects is to explore the cosmic "dark ages," during which the first stars in the Universe formed, with the 21 cm line of neutral hydrogen. At z>6, this light...
Astrophysics from the Highly-Redshifted 21 cm Line (2009)
Furlanetto, Steven, Lidz, Adam, Loeb, Abraham, McQuinn, Matthew, Pritchard, Jonathan, Aguirre, James, ...
The cosmic dark ages and the epoch of reionization, during which the first generations of stars and galaxies formed, are among the most compelling frontiers of extragalactic astrophysics and...
Cooray, Asantha, Amblard, Alexandre, Beichman, Charles, Benford, Dominic, Bernstein, Rebecca, Bock, James, ...
(Brief Summary) What is the total radiative content of the Universe since the epoch of recombination? The extragalactic background light (EBL) spectrum captures the redshifted energy released from...
The 21cm Signature of Early Relic \HII Regions (2009)
Tokutani, Midori, Yoshida, Naoki, Oh, S. Peng, Sugiyama, Naoshi
We calculate the spin temperature and 21 cm brightness of early \HII regions around the first stars. We use outputs from cosmological radiation-hydrodynamics simulations of the formation and...
The evolution of the Lyman-alpha forest effective optical depth following HeII reionisation (2009)
Bolton, James S., Oh, S. Peng, Furlanetto, Steven R.
Three independent observational studies have now detected a narrow (\Delta z ~ 0.5) dip centred at z=3.2 in the otherwise smooth redshift evolution of the Lya forest effective optical depth. This...
The Equation of State of the Intergalactic Medium After Hydrogen Reionization (2009)
Furlanetto, Steven, Oh, S. Peng
We use an analytic model to study how inhomogeneous hydrogen reionization affects the temperature distribution of the intergalactic medium (IGM). During this process, the residual energy of each...
CMBPol Mission Concept Study: Reionization Science with the Cosmic Microwave Background (2008)
Zaldarriaga, Matias, Colombo, Loris, Komatsu, Eiichiro, Lidz, Adam, Mortonson, Michael, Oh, S. Peng, ...
We summarize existing constraints on the epoch of reionization and discuss the observational probes that are sensitive to the process. We focus on the role large scale polarization can play....
Accretion onto Seed Black Holes in the First Galaxies (2008)
Milosavljevic, Milos, Bromm, Volker, Couch, Sean M., Oh, S. Peng
The validity of the hypothesis that the massive black holes in high redshift quasars grew from stellar-sized "seeds" is contingent on a seed's ability to double its mass every few ten million years....
The Impact of HI in Galaxies on 21-cm Intensity Fluctuations During the Reionisation Epoch (2008)
Wyithe, Stuart, Warszawski, Lila, Geil, Paul M., Oh, S. Peng
We investigate the impact of neutral hydrogen (HI) in galaxies on the statistics of 21-cm fluctuations using analytic and semi-numerical modelling. Following the reionisation of hydrogen the HI...
Photo-heating and the fate of hard photons during the reionisation of HeII by quasars (2008)
Bolton, James S., Oh, S. Peng, Furlanetto, Steven R.
We use a combination of analytic and numerical arguments to consider the impact of quasar photo-heating during HeII reionisation on the thermal evolution of the intergalactic medium (IGM). We...
A Global Stability Analysis of Clusters of Galaxies with Conduction and AGN Feedback Heating (2008)
Guo, Fulai, Oh, S. Peng, Ruszkowski, M.
We investigate a series of steady-state models of galaxy clusters, in which the hot intracluster gas is efficiently heated by active galactic nucleus (AGN) feedback and thermal conduction, and in...
Fossil Ionized Bubbles Around Dead Quasars During Reionization (2008)
Furlanetto, Steven, Haiman, Zoltan, Oh, S. Peng
One of the most dramatic signatures of the reionization era may be the enormous ionized bubbles around luminous quasars (with radii reaching ~40 comoving Mpc), which may survive as "fossil'' ionized...
The History and Morphology of Helium Reionization (2007)
Furlanetto, Steven, Oh, S. Peng
A variety of observations now indicate that intergalactic helium was fully ionized by z~3. The most recent measurements of the high-redshift quasar luminosity function imply that these sources had...
Inhomogeneous Helium Reionization and the Equation of State of the Intergalactic Medium (2007)
Furlanetto, Steven, Oh, S. Peng
The temperature of the intergalactic medium (IGM) is set by the competition between photoheating and adiabatic cooling, which are usually assumed to define a tight equation of state in which the...
Feedback Heating by Cosmic Rays in Clusters of Galaxies (2007)
Recent observations show that the cooling flows in the central regions of galaxy clusters are highly suppressed. Observed AGN-induced cavities/bubbles are a leading candidate for suppressing cooling,...
Model atmospheres for Irradiated Giant Stars: Implications for the Galactic Center (2007)
Jiminez, Raul, Silva, Juliana, Oh, S. Peng, Jorgensen, Uffe, Merritt, David
Also archived in: arXiv:astro-ph/0601527 v2 Jan 27 2006
Effects of dark matter decay and annihilation on the high-redshift 21 cm background (2006)
Furlanetto, Steven R., Oh, S. Peng, Pierpaoli, Elena
The radiation background produced by the 21 cm spin-flip transition of neutral hydrogen at high redshifts can be a pristine probe of fundamental physics and cosmology. At z~30–300, the...
Early Cosmological HII/HeIII Regions and Their Impact on Second-Generation Star Formation (2006)
Yoshida, Naoki, Oh, S. Peng, Kitayama, Tetsu, Hernquist, Lars
(Abridged) We present the results of three-dimensional radiation-hydrodynamics simulations of the formation and evolution of early HII/HeIII regions around the first stars. Cooling (by H2 and HD) and...
The Effects of Dark Matter Decay and Annihilation on the High-Redshift 21 cm Background (2006)
Furlanetto, Steven, Oh, S. Peng, Pierpaoli, Elena
The radiation background produced by the 21 cm spin-flip transition of neutral hydrogen at high redshifts can be a pristine probe of fundamental physics and cosmology. At z~30-300, the intergalactic...
Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe (2006)
Furlanetto, Steven, Oh, S. Peng, Briggs, Frank
Observations of the high-redshift Universe with the 21 cm hyperfine line of neutral hydrogen promise to open an entirely new window onto the early phases of cosmic structure formation. Here we review...
Feedback from Clustered Sources During Reionization (2006)
Kramer, Roban Hultman, Haiman, Zoltan, Oh, S. Peng
The reionization history of the intergalactic medium (IGM) at high redshift (z > 6) was likely strongly shaped by several global feedback processes. Because the earliest ionizing sources formed at...
Redshifted 21 Centimeter Emission from Minihalos Before Reionization (2006)
Furlanetto, Steven, Oh, S. Peng
Before reionization, the intergalactic medium (IGM) may have been sufficiently cold for low-mass "minihalos" to condense out of the gas and subsequently affect reionization. Previous work has shown...
Model Atmospheres for Irradiated Giant Stars: Implications for the Galactic Center (2006)
Jimenez, Raul, Da Silva, Juliana P., Oh, S. Peng, Jorgensen, Uffe G., Merritt, David
Irradiation of a stellar atmosphere by an external source (e.g. an AGN) changes its structure and therefore its spectrum. Using a state-of-the-art stellar atmosphere code, we calculate the infrared...
Have We Detected Patchy Reionization in Quasar Spectra? (2005)
Lidz, Adam, Oh, S. Peng, Furlanetto, Steven R.
The Lyman-alpha forest at z >~ 5.5 shows strong scatter in the mean transmission even when smoothed over very large spatial scales, >~ 50 Mpc/h. This has been interpreted as a signature of strongly...
Lyman Alpha Radiative Transfer in a Multi-Phase Medium (2005)
Hydrogen Ly-alpha is our primary emission-line window into high redshift galaxies. Surprisingly, despite an extensive literature, Ly-alpha radiative transfer in the most realistic case of a dusty,...
Taxing the Rich: Recombinations and Bubble Growth During Reionization (2005)
Furlanetto, Steven R., Oh, S. Peng
Reionization is inhomogeneous for two reasons: the clumpiness of the intergalactic medium (IGM) and clustering of the discrete ionizing sources. While numerical simulations can in principle take both...
Oh, S. Peng, Furlanetto, Steven R.
Detectable flux is visible in the Ly-alpha and Ly-beta troughs of the highest redshift ($z=6.42$) quasar found to date, SDSS J1148+5251. This has previously been interpreted as continuum...
Excess Ionization and Soft X-ray Emission from Cooling Flow Clusters (2004)
X-ray spectroscopy of cooling-flow clusters reveal an unexpected deficit of soft X-ray emission lines from gas at ~1/3 of the ambient plasma temperature, across a wide range of X-ray luminosities and...
Quasar Feedback: the Missing Link in Structure Formation (2004)
Scannapieco, Evan, Oh, S. Peng
We consider the impact of quasar outflows on structure formation. Such outflows are potentially more important than galactic winds, which appear insufficient to produce the level of preheating...
Early reionization by miniquasars (2003)
Madau, Piero, Rees, Martin J., Volonteri, Marta, Haardt, Francesco, Oh, S. Peng
Motivated by the recent detection by WMAP of a large optical depth to Thomson scattering -- implying a very early reionization epoch -- we assess a scenario where the universe was reionized by...
Fossil HII Regions: Self-Limiting Star Formation at High Redshift (2003)
Recent results by the WMAP satellite suggest that the intergalactic medium was significantly reionized at redshifts as high as z~17. At this early epoch, the first ionizing sources likely appeared in...
Sunyaev-Zeldovich Fluctuations from the First Stars? (2003)
Oh, S. Peng, Cooray, Asantha, Kamionkowski, Marc
WMAP's detection of high electron-scattering optical depth suggests substantial star formation at high redshift z~17 +/- 5. On the other hand, the recovered sigma_8 ~ 0.84 +/-0.04 disfavors a cluster...
Foregrounds for 21cm Observations of Neutral Gas at High Redshift (2003)
Oh, S. Peng, Mack, Katherine J.
We investigate a number of potential foregrounds for an ambitious goal of future radio telescopes such as the Square Kilometer Array (SKA) and Low Frequency Array (LOFAR): spatial tomography of...
Entropy Injection as a Global Feedback Mechanism (2002)
Both preheating of the intergalactic medium and radiative cooling of low entropy gas have been proposed to explain the deviation from self-similarity in the cluster L_x-T_x relation and the observed...
The abundance of dark galaxies (2002)
Verde, Licia, Oh, S. Peng, Jimenez, Raul
We show that gas in a large fraction of low mass dark matter halos may form Toomre stable disks, if angular momentum is conserved when the gas contracts. Such halos would be stable to star formation...
Probing the Dark Ages with Metal Absorption Lines (2002)
Recent observations of high redshift quasars at z~6 have finally revealed complete Gunn-Peterson absorption. However, this at best constrains the volume-weighted and mass-weighted hydrogen neutral...
Dark halo properties from rotation curves (2002)
Jimenez, Raul, Verde, Licia, Oh, S. Peng
We study a large set of high spatial resolution optical rotation curves of galaxies with the goal of determining the model parameters for a disk embedded within a CDM halo that we model either with a...
Did Very Massive Stars Pre-enrich and Reionize the Universe? (2001)
Oh, S. Peng, Nollett, Kenneth M., Madau, Piero, Wasserburg, G. J.
Recent studies of heavy r-process elements in low [Fe/H] halo stars have suggested that an initial population of metal-free very massive stars (VMSs) may be required to provide early Fe enrichment...
The first generation of protogalaxies likely formed out of primordial gas via H2-cooling in cosmological minihalos with virial temperatures of a few 1000K. However, their abundance is likely to have...
HeII Recombination Lines From the First Luminous Objects (2000)
Oh, S. Peng, Haiman, Zoltan, Rees, Martin J.
The hardness of the ionizing continuum from the first sources of UV radiation plays a crucial role in the reionization of the intergalactic medium (IGM). While usual stellar populations have soft...
Reionization by Hard Photons: I. X-rays from the First Star Clusters (2000)
Observations of the Ly-alpha forest at z~3 reveal an average metallicity Z~0.01 Z_solar. The high-redshift supernovae that polluted the IGM also accelerated relativistic electrons. Since the energy...
Probing High Redshift Radiation Fields with Gamma-Ray Absorption (2000)
The next generation of gamma-ray telescopes may be able to observe gamma-ray blazars at high redshift, possibly out to the epoch of reionization. The spectrum of such sources should exhibit an...