224 citations · 3.9k across the 128 of their papers we have counts for
40 papers · 1 filter
Shattering and coagulation of dust grains in interstellar turbulence
Hiroyuki Hirashita, Huirong Yan
We investigate shattering and coagulation of dust grains in turbulent interstellar medium (ISM). The typical velocity of dust grain as a function of grain size has been calculated…
Origin and Nature of Dust in the Early Universe
T. Nozawa, T. Kozasa, H. Umeda +8
We present recent advances in theoretical studies of the formation and evolution of dust in primordial supernovae (SNe) that are considered to be the main sources of dust in the ea…
Far-Infrared Properties of Blue Compact Dwarf Galaxies Observed with AKARI/Far-Infrared Surveyor (FIS)
Hiroyuki Hirashita, Hidehiro Kaneda, Takashi Onaka +1
We report basic far-infrared (FIR) properties of eight blue compact dwarf galaxies (BCDs) observed by AKARI. We measure the fluxes at the four FIS bands (wavelengths of 65 um, 90 u…
Extinction curves flattened by reverse shocks in supernovae
Hiroyuki Hirashita, Takaya Nozawa, Tsutomu T. Takeuchi +1
We investigate the extinction curves of young galaxies in which dust is supplied from Type II supernovae (SNe II) and/or pair instability supernovae (PISNe). Since at high redshift…
Origin of Chromatic Features in Multiple Quasars -Variability, Dust, or Microlensing -
Atsunori Yonehara, Hiroyuki Hirashita, Philipp Richter
Aims:In some of the lensed quasars, color differences between multiple images are observed at optical/near-infrared wavelengths. There are three possible origins of the color diffe…
Far-infrared dust properties in the Galaxy and the Magellanic Clouds
Hiroyuki Hirashita, Yasunori Hibi, Hiroshi Shibai
A recent data analysis of the far-infrared (FIR) map of the Galaxy and the Magellanic Clouds has shown that there is a tight correlation between two FIR colours: the 60 um-100 um a…
Time evolution of the radio continuum of young starbursts: The importance of synchrotron emission
H. Hirashita, L. K. Hunt
We investigate the radio spectral energy distributions (SEDs) of young star-forming galaxies and how they evolve with time. The duration and luminosity of the nonthermal radio emis…
Common Correlations between 60, 100 and 140 um Intensities in the Galactic Plane and Magellanic Clouds
Yasunori Hibi, Hiroshi Shibai, Mitsunobu Kawada +2
We investigate the far-infrared SED of the Galaxy and the Magellanic Clouds by using the COBE (COsmic Background Explorer) / DIRBE (Diffuse InfraRed Background Experiment) ZSMA (Zo…
Search for high column density systems with gamma ray bursts
Hiroyuki Hirashita, Hiroshi Shibai, Tsutomu T. Takeuchi
We investigate the possibility to search for metal-poor high column density (> 10^{23} cm^{-2}) clouds at high redshift (z) by using gamma ray burst (GRB) afterglows. Such clouds c…
Fate of clumps in damped Ly systems
Ilian T. Iliev, Hiroyuki Hirashita, Andrea Ferrara
Recent observations have revealed that damped Ly clouds (DLAs) host star formation activity. In order to examine if such star formation activity can be triggered by ionization f…
A model for the infrared dust emission from forming galaxies
Tsutomu T. Takeuchi, Takako T. Ishii, Takaya Nozawa +2
In the early epoch of galaxy evolution, dust is only supplied by supernovae (SNe). With the aid of a new physical model of dust production by SNe developed by Nozawa et al. (2003)…
Extinction curves expected in young galaxies
Hiroyuki Hirashita, Takaya Nozawa, Takashi Kozasa +2
We investigate the extinction curves of young galaxies in which dust is supplied from Type II supernovae (SNe II) and/or pair instability supernovae (PISNe). We adopt Nozawa et al.…
The role of dust in "active" and "passive" low-metallicity star formation
H. Hirashita, L. K. Hunt
We investigate the role of dust in star formation activity of extremely metal-poor blue compact dwarf galaxies (BCDs). Observations suggest that star formation in BCDs occurs in tw…
Star formation rate in galaxies from UV, IR, and H-alpha estimators
Hiroyuki Hirashita, Veronique Buat, Akio K. Inoue
Infrared (IR) luminosity of galaxies originating from dust emission can be used as an indicator of the star formation rate (SFR). Inoue et al. (2000, IHK) have derived a formula fo…
Infrared Spectral Energy Distribution Model for Extremely Young Galaxies
Tsutomu T. Takeuchi, Hiroyuki Hirashita, Takako T. Ishii +2
The small grain sizes produced by Type II supernova (SN II) models in young, metal-poor galaxies make the appearance of their infrared (IR) spectral energy distribution (SED) quite…
Molecular Hydrogen in Damped Ly-alpha Systems: Spatial Distribution
H. Hirashita, A. Ferrara, K. Wada +1
To interpret H_2 quasar absorption line observations in Damped Ly-alpha clouds (DLAs), we model the H_2 spatial distribution within a DLA. Based on numerical simulations of disk st…
The UV (GALEX) and FIR (ASTRO-F) All Sky Surveys: the measure of the dust extinction in the local universe
V. Buat, T. T. Takeuchi, A. Boselli +9
Before the end of 2002 will be launched the GALEX satellite (a NASA/SMEX project) which will observe all the sky in Ultraviolet (UV) through filters at 1500 and 2300 A down to m(AB…
Dust-to-gas ratio and star formation history of blue compact dwarf galaxies
H. Hirashita, Y. Y. Tajiri, H. Kamaya
This paper investigates the origin of the observed large variety in dust-to-gas ratio among blue compact dwarf galaxies (BCDs). By applying our chemical evolution model, we find th…
Absorption Measurement of Hydrogen Molecules in the Early Universe
Hiroshi Shibai, Tsutomu T. Takeuchi, T. N. Rengarajan +1
We investigate the observability of hydrogen molecules in absorption. The absorption efficiency of the hydrogen molecules become comparable with or larger than that of the dust gra…
H2 Formation in Low Metallicity Galaxies
Hideyuki Kamaya, Hiroyuki Hirashita
A possible formation mechanism of hydrogen molecules on a galactic scale is examined. We are interested especially in the role of hydrogen molecules for formation and evolution of…
Mass-Metallicity Relation for the Local Group Dwarf Spheroidal Galaxies: A New Picture for the Chemical Enrichment of Galaxies in the Lowest Mass Range
Naoyuki Tamura, Hiroyuki Hirashita, Tsutomu T. Takeuchi
The virial mass ()-metallicity relation among the Local Group dwarf spheroidal galaxies (dSphs) is examined. Hirashita, Takeuchi, & Tamura showed that the dSphs can be…
Effect of Dust Extinction on Estimating Star Formation Rate of Galaxies: Lyman Continuum Extinction
Akio K. Inoue, Hiroyuki Hirashita, Hideyuki Kamaya
We re-examine the effect of Lyman continuum ( Å) extinction (LCE) by dust in H {\sc ii} regions in detail and discuss how it affects the estimation of the global star fo…
Impact of Future Submillimeter and Millimeter Large Facilities on the Studies of Galaxy Formation and Evolution
Tsutomu T. Takeuchi, Ryohei Kawabe, Kotaro Kohno +4
We investigate what we can learn about galaxy formation and evolution from the data which will be obtained by the forthcoming large submillimeter/millimeter facilities, mainly by t…
Chemical Evolution of the Galaxy Based on the Oscillatory Star Formation History
H. Hirashita, A. Burkert, T. T. Takeuchi
We model the star formation history (SFH) and the chemical evolution of the Galactic disk by combining an infall model and a limit-cycle model of the interstellar medium (ISM). Rec…