scholarly journals A new concept of transonic galactic outflows and its application to the Sombrero galaxy

2016 ◽  
Vol 11 (S321) ◽  
pp. 125-125
Author(s):  
Asuka Igarashi ◽  
Masao Mori ◽  
Shin-ya Nitta
Keyword(s):  
Star Formation ◽  
Density Distribution ◽  
Cold Dark Matter ◽  
Star Formation History ◽  
Dark Matter Halo ◽  
Polytropic Model ◽  
Gas Density ◽  
Galactic Outflows ◽  
Distant Region ◽  
Subsonic Region

AbstractWe study fundamental properties of transonic galactic outflows in the gravitational potential of a cold dark matter halo (DMH) with a central super-massive black hole (SMBH) assuming a polytropic, steady and spherically symmetric state. We have classified the transonic solutions with respect to their topology in the phase space. As a result, we have found two types of transonic solutions characterized by a magnitude relationship between the gravity of DMH and that of SMBH. These two types of solutions have different loci of the transonic points; one transonic point is formed at a central region (< 0.01kpc) and another is at a distant region (> 100kpc). Also, mass fluxes and outflow velocities are different between the two solutions. These two transonic solutions may play different roles on the star formation history of galaxies and the metal contamination of intergalactic space. Furthermore, we have applied our model to the Sombrero galaxy. In this galaxy, the wide-spread hot gas is detected as an apparent trace of galactic outflows while the star-formation rate is disproportionately low, and the observed gas density distribution is quite similar to the hydrostatic state (Li et al. 2011). To solve this discrepancy, we propose a slowly accelerating outflow in which the transonic point forms in a distant region (~ 120 kpc) and the subsonic region spreads across the stellar distribution. In the subsonic region, the gas density distribution is similar to that of the hydrostatic state. Our model predicts the possibility of the slowly accelerating outflow in the Sombrero galaxy. Igarashi et al. 2014 used the isothermal model and well reproduced the observed gas density distribution, but the estimated mass flux (1.8M⊙/yr) is lager than the mass of the gas supplied by stars (0.3-0.4M⊙/yr). Then, we expect that the polytropic model may reproduce the observational mass of the supplied gas (Igarashi et al. 2015). Such slowly accelerating outflows should be distinguished from the conventional supersonic outflows frequently argued in star-forming galaxies.

scholarly journals Transonic galactic outflows in a dark matter halo with a central black hole

2015 ◽  
Vol 11 (A29B) ◽  
pp. 741-741
Author(s):  
Asuka Igarashi ◽  
Masao Mori ◽  
Shin-ya Nitta
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Density Distribution ◽  
Mass Flux ◽  
Dark Matter Halo ◽  
Polytropic Model ◽  
Gas Density ◽  
Topological Features ◽  
Galactic Outflows ◽  
Distant Region

AbstractWe study fundamental properties of transonic galactic outflows in the gravitational potential of a cold dark matter halo (DMH) with a central super-massive black hole (SMBH) assuming an isothermal, steady and spherically symmetric state. Transonic solutions of galactic outflows are classified according to their topological features. As result, we find two types of transonic solutions distinguished by a magnitude relationship between the gravity of DMH and that of SMBH. The loci of transonic points for two types are different; one transonic point is formed at a central region (< 0.01kpc) and another is at a very distant region (> 100kpc). Also, mass fluxes and outflow velocities are different for two solutions. Thus, these solutions may differently influence the evolution of galaxies and the release of metals into the intergalactic space.Furthermore, we apply our model to the Sombrero galaxy. In this galaxy, the wide-spread hot gas is detected as the trace of galactic outflows while the star-formation rate is low, and the observed gas density distribution is similar to the hydrostatic state (Li et al. 2011). To solve this discrepancy, we propose a solution that this galaxy has a slowly accelerating outflow; the transonic point forms in a very distant region (~ 120 kpc) and the wide subsonic region spreads across the stellar distribution. Thus, the gas density distribution in the observed region is similar to the hydrostatic state. Such slowly accelerating outflows are different from high-velocity outflows conventionally studied (Igarashi et al. 2014).However, this isothermal model requires an unrealistically large mass flux. Then, we apply the polytropic model to this galaxy incorporating mass flux supplied by stellar components. We find that it can reproduce the observed gas density and the temperature distributions with the realistic mass flux. Thus, our polytropic model successfully demonstrates the existence of the slowly accelerating outflow in the Sombrero galaxy (Igarashi et al. 2015).

scholarly journals Origin of the galaxy morphology

2003 ◽  
Vol 208 ◽  
pp. 431-432
Author(s):  
N. Nakasato
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
High Resolution ◽  
Cold Dark Matter ◽  
Star Formation History ◽  
The Galaxy ◽  
Particle Hydrodynamics ◽  
History Of ◽  
Analytic Models ◽  
Galaxy Morphology

In the current most plausible Cold Dark Matter (CDM) cosmology, larger halos increase their mass by the progressive mergers of smaller clumps. Due to these progressive merger events, galaxies have formed and evolved. Such merger events could trigger star bursts depending on mass of a merging object. In other words, star formation history reflects the strength of the interaction between a galaxy and merging objects. Also, a several merger events strongly affect the development of the morphology of galaxies as assumed in semi-analytic models. In the most advanced semi-analytic models, N-body simulations of dark matter particles are used to obtain the merging history of halos. By combining the description of radiative cooling, hydrodynamics and star formation with the obtained merging history, such models successfully have explained the various qualitative predictions. Here, we show the results of similar approach but using a fullly numerical model. In contrast to the semi-analytic models, we use our high resolution Smoothed Particle Hydrodynamics (SPH) models. With our SPH code, we try to tackle the problem of the galaxy morphology. We have done a several handful high-resolution SPH simulations and analyzed the merging history of such models. Accordingly, we can see the relation between the obtained morphology and the merging history or other physical properties of the model.

scholarly journals Star formation history from the cosmic infrared background anisotropies

2018 ◽  
Vol 614 ◽  
pp. A39 ◽  
Author(s):  
A. S. Maniyar ◽  
M. Béthermin ◽  
G. Lagache
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Formation History ◽  
Dark Matter Halo ◽  
Model Parameters ◽  
Formation History ◽  
Infrared Background ◽  
Cosmic Infrared Background

We present a linear clustering model of cosmic infrared background (CIB) anisotropies at large scales that is used to measure the cosmic star formation rate density up to redshift 6, the effective bias of the CIB, and the mass of dark matter halos hosting dusty star-forming galaxies. This is achieved using the Planck CIB auto- and cross-power spectra (between different frequencies) and CIB × CMB (cosmic microwave background) lensing cross-spectra measurements, as well as external constraints (e.g. on the CIB mean brightness). We recovered an obscured star formation history which agrees well with the values derived from infrared deep surveys and we confirm that the obscured star formation dominates the unobscured formation up to at least z = 4. The obscured and unobscured star formation rate densities are compatible at 1σ at z = 5. We also determined the evolution of the effective bias of the galaxies emitting the CIB and found a rapid increase from ~0.8 at z = 0 to ~8 at z = 4. At 2 < z < 4, this effective bias is similar to that of galaxies at the knee of the mass functions and submillimetre galaxies. This effective bias is the weighted average of the true bias with the corresponding emissivity of the galaxies. The halo mass corresponding to this bias is thus not exactly the mass contributing the most to the star formation density. Correcting for this, we obtained a value of log(Mh/M⊙) = 12.77−0.125+0.128 for the mass of the typical dark matter halo contributing to the CIB at z = 2. Finally, using a Fisher matrix analysis we also computed how the uncertainties on the cosmological parameters affect the recovered CIB model parameters, and find that the effect is negligible.

scholarly journals Star Formation History of Dwarf Galaxies in Cosmological Hydrodynamic Simulations

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
Kentaro Nagamine
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Star Formation History ◽  
Hydrodynamic Simulations ◽  
Cosmological Context ◽  
Cold Dark Matter Model ◽  
Formation History ◽  
History Of

We examine the past and current work on the star formation (SF) histories of dwarf galaxies in cosmological hydrodynamic simulations. The results obtained from different numerical methods are still somewhat mixed, but the differences are understandable if we consider the numerical and resolution effects. It remains a challenge to simulate the episodic nature of SF history in dwarf galaxies at late times within the cosmological context of a cold dark matter model. More work is needed to solve the mysteries of SF history of dwarf galaxies employing large-scale hydrodynamic simulations on the next generation of supercomputers.

scholarly journals Gamma-ray burst cosmology: Hubble diagram and star formation history

2017 ◽  
Vol 26 (02) ◽  
pp. 1730002 ◽  
Author(s):  
Jun-Jie Wei ◽  
Xue-Feng Wu
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Mass Formula ◽  
Gamma Ray ◽  
Massive Stars ◽  
High Redshift ◽  
Formation Rate ◽  
Star Formation History ◽  
Dark Matter Halo ◽  
Hubble Diagram

We briefly introduce the disadvantages for Type Ia supernovae (SNe Ia) as standard candles to measure the universe, and suggest Gamma-ray bursts (GRBs) can serve as a powerful tool for probing the properties of high redshift universe. We use GRBs as distance indicators in constructing the Hubble diagram at redshifts beyond the current reach of SNe Ia observations. Since the progenitors of long GRBs (LGRBs) are confirmed to be massive stars, they are deemed as an effective approach to study the cosmic star formation rate (SFR). A detailed representation of how to measure high-[Formula: see text] SFR using GRBs is presented. Moreover, first stars can form only in structures that are suitably dense, which can be parametrized by defining the minimum dark matter halo mass [Formula: see text]. [Formula: see text] must play a crucial role in star formation. The association of LGRBs with the collapses of massive stars also indicates that the GRB data can be applied to constrain the minimum halo mass [Formula: see text] and to investigate star formation in dark matter halos.

scholarly journals Stochastic star formation and early galactic nucleosynthesis

2012 ◽  
Vol 8 (S292) ◽  
pp. 336-336
Author(s):  
Lan Nguyen ◽  
Grant Mathews
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dark Matter Halo ◽  
Stellar Winds ◽  
Galactic Chemical Evolution ◽  
Chemical Enrichment ◽  
Ia Supernovae ◽  
Chemical Evolution Model

AbstractWe discuss calculations of the star formation, nucleosynthesis, and stochastic evolution of proto-galactic clouds in a galactic chemical evolution model which is motivated by cold dark matter simulations of hierarchical galaxy formation (Saleh et al. 2006; Lan et al. 2010). We utilize SN-induced and dark matter halo formation-induced star formation within a model that follows the evolution of chemical enrichment and energy input to the clouds via Type II, Ia supernovae and stellar winds.

Star Formation History and Stellar Metallicity Distribution in a Cold Dark Matter Universe

2001 ◽  
Vol 558 (2) ◽  
pp. 497-504 ◽  
Author(s):  
Kentaro Nagamine ◽  
Masataka Fukugita ◽  
Renyue Cen ◽  
Jeremiah P. Ostriker
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Cold Dark Matter ◽  
Star Formation History ◽  
Formation History ◽  
Metallicity Distribution
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