ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 2010-2014  (8)
  • 1
    facet.materialart.
    Unknown
    Muon spin relaxation and electron/neutron diffraction studies of BaTi_{2}(As_{1−x}Sb_{x})_{2}O: Absence of static magnetism and superlattice reflections (2013)
    American Physical Society (APS)
    Details
    Publication Date: 2013-12-07
    Description: Author(s): Y. Nozaki, K. Nakano, T. Yajima, H. Kageyama, B. Frandsen, L. Liu, S. Cheung, T. Goko, Y. J. Uemura, T. S. J. Munsie, T. Medina, G. M. Luke, J. Munevar, D. Nishio-Hamane, and C. M. Brown We present the results of muon spin relaxation/rotation, transmission electron microscopy, and neutron diffraction measurements performed on several specimens of BaTi 2 (As 1− x Sb x ) 2 O, which is known to have either charge density or spin density wave ordering at T DW for all x , and superconductivity belo... [Phys. Rev. B 88, 214506] Published Fri Dec 06, 2013
    Keywords: Superfluidity and superconductivity
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Angular momentum loss of primordial gas in Ly{alpha} radiation field (2014)
    Oxford University Press
    Details
    Publication Date: 2014-05-04
    Description: We present results on the radiation drag exerted by an isotropic and homogeneous background of Lyα photons on neutral gas clouds orbiting within H ii regions around Population III stars of different masses. The Doppler shift causes a frequency difference between photons moving in the direction of the cloud and opposite to it resulting in a net momentum loss of the cloud in the direction of motion. We find that half of the angular momentum of gas with v 20 km s –1 near ( r 3 kpc) a Population III star of 120 M at z  = 20 is lost within ~10 6 yr. The radiation drag is a strong function of cloud velocity that peaks at v ~ 20 km s –1 reflecting the frequency dependence of the photon cross-section. Clouds moving with velocities larger than ~100 km s –1 lose their angular momentum on time-scales of ~10 8 yr. At lower redshifts radiation drag becomes inefficient as the Lyα photon density in H ii regions decreases by a factor (1 +  z ) 3 and angular momentum is lost on time-scales 10 8 yr even for low-velocity clouds. Our results suggest that a sweet spot exists for the loss of angular momentum by radiation drag for gas clouds at z 〉 10 and with v ~ 20 km s –1 . Comparison to dynamical friction forces acting on typical gas clouds suggest that radiation drag is the dominant effect impacting the orbit. We propose that this effect can suppress the formation of extended gas discs in the first galaxies and help gas accretion near galactic centres and central black holes.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Dust properties of Lyman-break galaxies in cosmological simulations (2014)
    Oxford University Press
    Details
    Publication Date: 2014-03-21
    Description: Recent observations have indicated the existence of dust in high-redshift galaxies, however, the dust properties in them are still unknown. Here we present theoretical constraints on dust properties in Lyman-break galaxies (LBGs) at z  = 3 by post-processing a cosmological smoothed particle hydrodynamics simulation with radiative transfer calculations. We calculate the dust extinction in 2800 dark matter haloes using the metallicity information of individual gas particles in our simulation. We use only bright galaxies with rest-frame ultraviolet (UV) magnitude M 1700  〈 –20 mag, and study the dust size, dust-to-metal mass ratio, and dust composition. From the comparison of calculated colour excess between B and V band [i.e. E ( B  –  V )] and the observations, we constrain the typical dust size, and show that the best-fitting dust grain size is ~ 0.05 μm, which is consistent with the results of theoretical dust models for Type II supernova. Our simulation with the dust extinction effect can naturally reproduce the observed rest-frame UV luminosity function of LBGs at z  = 3 without assuming an ad hoc constant extinction value. In addition, in order to reproduce the observed mean E ( B  –  V ), we find that the dust-to-metal mass ratio needs to be similar to that of the local galaxies, and that the graphite dust is dominant or at least occupy half of dust mass.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Escape of Ly{alpha} and continuum photons from star-forming galaxies (2014)
    Oxford University Press
    Details
    Publication Date: 2014-04-02
    Description: A large number of high-redshift galaxies have been discovered via their narrow-band Lyα line or broad-band continuum colours in recent years. The nature of the escaping process of photons from these early galaxies is crucial to understand galaxy evolution and the cosmic reionization. Here, we investigate the escape of Lyα, non-ionizing UV-continuum ( = 1300-1600 Å in rest frame), and ionizing photons ( 〈 912 Å) from galaxies by combining a cosmological hydrodynamic simulation with three-dimensional multiwavelength radiative transfer calculations. The galaxies are simulated in a box of 5 3 h –3 Mpc 3 with high resolutions using the Aquila initial condition which reproduces a Milky Way-like galaxy at redshift z = 0. We find that the escape fraction ( f esc ) of these different photons shows a complex dependence on redshift and galaxy properties: $f_{\rm esc}^{\rm \rm {Ly{\alpha }}}$ and $f_{\rm esc}^{\rm UV}$ appear to evolve with redshift, and they show similar, weak correlations with galaxy properties such as mass, star formation, metallicity, and dust content, while $f_{\rm esc}^{\rm Ion}$ remains roughly constant at ~0.2 from z ~ 0 to 10, and it does not show clear dependence on galaxy properties. $f_{\rm esc}^{\rm \rm {Ly{\alpha }}}$ correlates more strongly with $f_{\rm esc}^{\rm UV}$ than with $f_{\rm esc}^{\rm Ion}$ . In addition, we find a relation between the emergent Lyα luminosity and the ionizing photon emissivity of Lyman Alpha Emitters (LAEs). By combining this relation with the observed luminosity functions of LAEs at different redshift, we estimate the contribution from LAEs to the reionization of intergalactic medium (IGM). Our result suggests that ionizing photons from LAEs alone are not sufficient to ionize IGM at z 6, but they can maintain the ionization of IGM at z ~ 0–5.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Distinctive 21-cm structures of the first stars, galaxies and quasars (2014)
    Oxford University Press
    Details
    Publication Date: 2014-11-01
    Description: Observations of the redshifted 21-cm line with forthcoming radio telescopes promise to transform our understanding of the cosmic reionization. To unravel the underlying physical process, we investigate the 21-cm structures of three different ionizing sources – Population (Pop) III stars, the first galaxies and the first quasars – by using radiative transfer simulations that include both ionization of neutral hydrogen and resonant scattering of Lyα photons. We find that Pop III stars and quasars produce a smooth transition from an ionized and hot state to a neutral and cold state, because of their hard spectral energy distribution with abundant ionizing photons, in contrast to the sharp transition in galaxies. Furthermore, Lyα scattering plays a dominant role in producing the 21-cm signal because it determines the relation between hydrogen spin temperature and gas kinetic temperature. This effect, also called Wouthuysen–Field coupling, depends strongly on the ionizing source. It is strongest around galaxies, where the spin temperature is highly coupled to that of the gas, resulting in extended absorption troughs in the 21-cm brightness temperature. However, in the case of Pop III stars, the 21-cm signal shows both emission and absorption regions around a small H ii bubble. For quasars, a large emission region in the 21-cm signal is produced, and the absorption region decreases as the size of the H ii bubble becomes large due to the limited travelling time of photons. We predict that future surveys from large radio arrays, such as the Murchison Widefield Array, the Low Frequency Array and the Square Kilometre Array, might be able to detect the 21-cm signals of primordial galaxies and quasars, but possibly not those of Pop III stars, because of their small angular diameters.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    Effects of photon trapping on the Ly{alpha} properties of star-forming galaxies (2013)
    Oxford University Press
    Details
    Publication Date: 2013-12-27
    Description: Recent observations show that a large number of Lyα emitters at high redshift z   3 have unusually high Lyα equivalent widths (EW 400 Å). However, the origin of these high EWs is an open question. Here, we investigate the impacts of photon trapping on the Lyα EW and other properties by tracking the Lyα radiative transfer in spherical galactic clouds. We find that the delayed escape of the Lyα photons can change the Lyα properties significantly. During the transition phase from optically thick to optically thin where the Lyα photons can escape simultaneously, the EW can be boosted to ~ 1000 Å, the Lyα luminosity can be increased by a factor of a few, and the line profile can be significantly broadened. The boost factor appears to depend on the galaxy properties such as mass and star formation rate and time-scale; therefore, future investigation combing 3D Lyα radiative transfer calculations with cosmological simulations of galaxy formation and evolution is needed to fully understand the Lyα properties of early star-forming galaxies.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    Effect of radiative transfer on damped Ly  and Lyman limit systems in cosmological SPH simulations (2012)
    Oxford University Press
    Details
    Publication Date: 2012-12-21
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    Distinctive 21-cm structures of the first stars, galaxies and quasars (2014)
    Oxford University Press
    Details
    Publication Date: 2014-10-30
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...