Helium Sedimentation and the Ultraviolet Upturn in Brightest Cluster Galaxies (2009)
Recent observations with the Galaxy Evolution Explorer (GALEX) show strong unexpected ultraviolet (UV) excess in the spectrum of brightest cluster galaxies (BCGs). It is believed that the excess UV...
Helium Sedimentation and the UV Upturn in Brightest Cluster Galaxies (2009)
Recent observations with Galaxy Evolution Explorer (GALEX) show strong unexpected UV excess in the spectrum of brightest cluster galaxies (BCGs). It is believed that the excess UV signal is produced...
Effects of Baryon Dissipation on the Dark Matter Virial Scaling Relation (2009)
Lau, Erwin T., Nagai, Daisuke, Kravtsov, Andrey V.
We investigate effects of baryon dissipation on the dark matter virial scaling relation between total mass and velocity dispersion and the velocity bias of galaxies in groups and clusters using...
Non-Equilibrium Electrons and the Sunyaev-Zel'dovich Effect of Galaxy Clusters (2009)
Rudd, Douglas H., Nagai, Daisuke
We present high-resolution cosmological hydrodynamic simulations of three galaxy clusters employing a two-temperature model for the intracluster medium. We show that electron temperatures in cluster...
Mroczkowski, Tony, Bonamente, Max, Carlstrom, John E., Culverhouse, Thomas L., Greer, Christopher, Hawkins, David, ...
We investigate the utility of a new, self-similar pressure profile for fitting Sunyaev–Zel’dovich (SZ) effect observations of galaxy clusters. Current SZ imaging instruments–such as the...
Lau, Erwin T., Kravtsov, Andrey V., Nagai, Daisuke
We present analysis of bulk and random gas motions in the intracluster medium using high-resolution Eulerian cosmological simulations of sixteen simulated clusters, including both very relaxed and...
Effect of helium sedimentation on X-ray measurements of galaxy clusters (2009)
The uniformity of the helium-to-hydrogen (He-to-H) abundance ratio in the X-ray emitting intracluster medium (ICM) is one of the commonly adopted assumptions in X-ray analyses of galaxy clusters and...
雲仙火山1991年6月3日の火砕流による人的被害 (2009)
杉本, 伸一, 長井, 大輔, Sugimoto, Shinichi, Nagai, Daisuke, スギモト, シンイチ, ナガイ, ダイスケ
The 1990-1995 eruption of Unzen volcano, Japan, was characterized by lava dome growth and pyroclastic flows triggered by dome collapse. One of the largest pyroclastic flows occurred at 4:08 p.m. on...
The impact of baryonic cooling on giant arc abundances (2008)
Rozo, Eduardo, Nagai, Daisuke, Keeton, Charles, Kravtsov, Andrey
Using ray tracing for simple analytic profiles, we demonstrate that the lensing cross section for producing giant arcs has distinct contributions due to arcs formed through image distortion only, and...
Effect of Helium Sedimentation on X-ray Measurements of Galaxy Clusters (2008)
The uniformity of the helium-to-hydrogen abundance ratio in X-ray emitting intracluster medium (ICM) is one of the commonly adopted assumptions in X-ray analyses of galaxy clusters and cosmological...
Gamma-ray probe of cosmic ray pressure in galaxy clusters and cosmological implications (2008)
Ando, Shin'ichiro, Nagai, Daisuke
Cosmic rays produced in cluster accretion and merger shocks provide pressure to the intracluster medium (ICM) and affect the mass estimates of galaxy clusters. Although direct evidence for cosmic ray...
The Cluster-Merger Shock in 1E 0657-56 (2008)
Koda, Jun, Milosavljevic, Milos, Shapiro, Paul R., Nagai, Daisuke, Nakar, Ehud
The merging galaxy cluster 1E 0657-56, known as the "bullet cluster," is one of the hottest clusters known. The X-ray emitting plasma exhibits bow-shock-like temperature and density jumps. The...
Nakar, Ehud, Milosavljević, Miloš, Nagai, Daisuke
X-ray observations of galaxy cluster merger shocks can be used to constrain nonthermal processes in the intracluster medium (ICM). The presence of nonthermal pressure components in the ICM, as well...
Bonamente, Massimiliano, Marshall, Joy, LaRoque, Samuel J., Carlstrom, John E., Nagai, Daisuke, Marrone, Daniel P.
We present Sunyaev-Zel'dovich Effect (SZE) scaling relations for 38 massive galaxy clusters at redshifts 0.14 ≤ z≤ 0.89, observed with both the Chandra X-ray Observatory and the centimeter-wave...
Effects of galaxy formation on thermodynamics of the intracluster medium (2007)
Nagai, Daisuke, Kravtsov, Andrey V., Vikhlinin, Alexey
We present detailed comparisons of the intracluster medium (ICM) in cosmological Eulerian cluster simulations with deep Chandra observations of nearby relaxed clusters. To assess the impact of galaxy...
Bonamente, Massimiliano, Joy, Marshall, LaRoque, Samuel, Carlstrom, John, Nagai, Daisuke, Marrone, Dan
We present Sunyaev-Zel'dovich Effect (SZE) scaling relations for 38 massive galaxy clusters at redshifts 0.14
Nakar, Ehud, Milosavljevic, Milos, Nagai, Daisuke
X-ray observations of galaxy cluster merger shocks can be used to constrain nonthermal processes in the intracluster medium (ICM). The presence of nonthermal pressure components in the ICM, as well...
The Cluster-Merger Shock in 1E 0657–56: Faster than a Speeding Bullet? (2007)
Milosavljević, Miloš, Koda, Jun, Nagai, Daisuke, Nakar, Ehud, Shapiro, Paul R.
Shock waves driven in the intergalactic medium during the merging of galaxy clusters have been observed in X-ray imaging and spectroscopy. Fluid motions inferred from the shock strength and...
Gamma-ray probe of cosmic-ray pressure in galaxy clusters and cosmological implications (2007)
Ando, Shin'ichiro, Nagai, Daisuke
Cosmic rays produced in cluster accretion and merger shocks provide pressure to the intracluster medium (ICM) and affect the mass estimates of galaxy clusters. Although direct evidence for cosmic-ray...
Effects of Galaxy Formation on Thermodynamics of the Intracluster Medium (2007)
Nagai, Daisuke, Kravtsov, Andrey V., Vikhlinin, Alexey
We present detailed comparisons of the intracluster medium (ICM) in cosmological Eulerian cluster simulations with deep Chandra observations of nearby relaxed clusters. To assess the impact of galaxy...
The Cluster-Merger Shock in 1E 0657-56: Faster than the Speeding Bullet? (2007)
Milosavljevic, Milos, Koda, Jun, Nagai, Daisuke, Nakar, Ehud, Shapiro, Paul R.
Shock waves driven in the intergalactic medium during the merging of galaxy clusters have been observed in X-ray imaging and spectroscopy. Fluid motions inferred from the shock strength and...
Missing Thermal Energy of the Intracluster Medium (2006)
Afshordi, Niayesh, Lin, Yen-Ting, Nagai, Daisuke, Sanderson, Alastair J. R.
The Sunyaev-Zel'dovich (SZ) effect is a direct probe of thermal energy content of the Universe, induced in the cosmic microwave background (CMB) sky through scattering of CMB photons off hot...
Modeling Chandra X-ray observations of Galaxy Clusters using Cosmological Simulations (2006)
Nagai, Daisuke, Kravtsov, Andrey V., Vikhlinin, Alexey
X-ray observations of galaxy clusters potentially provide powerful cosmological probes if systematics due to our incomplete knowledge of the intracluster medium (ICM) physics are understood and...
The Impact of Baryonic Cooling on Giant Arc Abundances (2006)
Rozo, Eduardo, Nagai, Daisuke, Keeton, Charles, Kravtsov, Andrey
Using ray tracing for simple analytic profiles, we demonstrate that the lensing cross section for producing giant arcs has distinct contributions due to arcs formed through image distortion only, and...
Testing X-ray Measurements of Galaxy Clusters with Cosmological Simulations (2006)
Nagai, Daisuke, Vikhlinin, Alexey, Kravtsov, Andrey V.
X-ray observations of galaxy clusters potentially provide powerful cosmological probes if systematics due to our incomplete knowledge of the intracluster medium (ICM) physics are understood and...
"The Perfect Slope": A new robust low-scatter X-ray mass indicator for clusters of galaxies (2006)
Vikhlinin, Alexey, Kravtsov, Andrey V., Nagai, Daisuke
This presentation is a Moriond version of our recent paper (Kravtsov, Vikhlinin & Nagai astro-ph/0603205) where we discussed X-ray proxies for the total cluster mass, including the spectral...
Galaxy orbits and the intracluster gas temperature in clusters (2006)
Benatov, Latchezar, Rines, Ken, Natarajan, Priyamvada, Kravtsov, Andrey, Nagai, Daisuke
In this paper we examine how well galaxies and intra-cluster gas trace the gravitational potential of clusters. Utilizing mass profiles derived from gravitational lensing and X-ray observations,...
A New Robust Low-Scatter X-ray Mass Indicator for Clusters of Galaxies (2006)
Kravtsov, Andrey V., Vikhlinin, Alexey, Nagai, Daisuke
We present comparison of X-ray proxies for the total cluster mass, including the spectral temperature (Tx), gas mass measured within r500 (Mg), and the new proxy, Yx, which is a simple product of Tx...
The Impact of Galaxy Formation on the Sunyaev-Zeldovich Effect of Galaxy Clusters (2005)
We study the effects of galaxy formation on the Sunyaev-Zel'dovich effect (SZE) observable-mass relations using high-resolution cosmological simulations. The simulations of eleven individual clusters...
The Effect of Baryons on Halo Shapes (2005)
Kazantzidis, Stelios, Zentner, Andrew R., Nagai, Daisuke
Observational evidence indicates a mismatch between the shapes of collisionless dark matter (DM) halos and those of observed systems. Using hydrodynamical cosmological simulations we investigate the...
Effects of cooling and star formation on the baryon fractions in clusters (2005)
Kravtsov, Andrey V., Nagai, Daisuke, Vikhlinin, Alexey A.
We study the effects of dissipation on the baryon fractions in clusters using high-resolution cosmological simulations of nine clusters that resolve formation of cluster galaxies. The simulations of...
Supersonic Motions of Galaxies in Clusters (2004)
Faltenbacher, Andreas, Kravtsov, Andrey V., Nagai, Daisuke, Gottloeber, Stefan
We study motions of galaxies in galaxy clusters formed in the concordance LCDM cosmology. We use high-resolution cosmological simulations that follow dynamics of dark matter and gas and include...
The Radial Distribution of Galaxies in LCDM clusters (2004)
Nagai, Daisuke, Kravtsov, Andrey V.
We study the radial distribution of subhalos and galaxies using high-resolution cosmological simulations of galaxy clusters formed in the concordance LCDM cosmology. In agreement with previous...
Gnedin, Oleg Y., Kravtsov, Andrey V., Klypin, Anatoly A., Nagai, Daisuke
The cooling of gas in the centers of dark matter halos is expected to lead to a more concentrated dark matter distribution. The response of dark matter to the condensation of baryons is usually...
The Effect of Gas Cooling on the Shapes of Dark Matter Halos (2004)
Kazantzidis, Stelios, Kravtsov, Andrey V., Zentner, Andrew R., Allgood, Brandon, Nagai, Daisuke, Moore, Ben
We analyze the effect of dissipation on the shapes of dark matter (DM) halos using high-resolution cosmological gasdynamics simulations of clusters and galaxies in the LCDM cosmology. We find that...
Simulating the Formation of Galaxy Clusters (2004)
Nagai, Daisuke, Kravtsov, Andrey V.
We study the effects of radiative cooling, star formation and stellar feedback on the properties and evolution of galaxy clusters using high-resolution Adaptive Mesh Refinement N-body+gasdynamics...
Effect of Internal Flows on Sunyaev-Zeldovich Measurements of Cluster Peculiar Velocities (2002)
Nagai, Daisuke, Kravtsov, Andrey V., Kosowsky, Arthur
Galaxy clusters are potentially powerful probes of the large-scale velocity field in the Universe because their peculiar velocity can be estimated directly via the kinematic Sunyaev-Zeldovich effect...
Cold Fronts in CDM clusters (2002)
Nagai, Daisuke, Kravtsov, Andrey V.
Recently, high-resolution Chandra observations revealed the existence of very sharp features in the X-ray surface brightness and temperature maps of several clusters (Vikhlinin et. al., 2001). These...
Sunyaev-Zel'dovich Effect Imaging of Massive Clusters of Galaxies at Redshift z > 0.8 (2000)
Joy, Marshall, LaRoque, Samuel, Grego, Laura, Carlstrom, John E., Dawson, Kyle, Ebeling, Harald, ...
We present Sunyaev-Zel'dovich Effect (SZE) imaging observations of three distant (z > 0.8) and highly X-ray luminous clusters of galaxies, Cl1226+33, Cl0152-13 and MS1054-03. Two of the clusters,...
Antibacterial Properties of Some Cyclic Organobismuth(III) Compounds
Kotani, Toshiaki, Nagai, Daisuke, Asahi, Kensuke, Suzuki, Hitomi, Yamao, Fumiaki, Kataoka, Nobumasa, ...
Bismuth compounds are known for their low levels of toxicity in mammals, and various types of bismuth salts have been used to treat medical disorders. As part of our program to probe this aspect of...
Antibacterial Properties of Some Cyclic Organobismuth(III) Compounds
Kotani, Toshiaki, Nagai, Daisuke, Asahi, Kensuke, Suzuki, Hitomi, Yamao, Fumiaki, Kataoka, Nobumasa, ...
Bismuth compounds are known for their low levels of toxicity in mammals, and various types of bismuth salts have been used to treat medical disorders. As part of our program to probe this aspect of...