2,080 research outputs found
Towards a Comprehensive Fueling-Controlled Theory on the Growth of Massive Black Holes and Host Spheroids
We study the relation between nuclear massive black holes and their host
spheroid gravitational potential. Using AMR numerical simulations, we analyze
how gas is transported in the nuclear (central kpc) regions of galaxies. We
study the gas fueling onto the inner accretion disk (sub-pc scale) and the star
formation in a massive nuclear disk like those generally found in
proto-spheroids (ULIRGs, SCUBA Galaxies). These sub-pc resolution simulation of
gas fueling that is mainly depleted by star formation naturally satisfy the
`M_BH - $M_virial' relation, with a scatter considerably less than the observed
one. We found a generalized version of Kennicutt-Schmidt Law for starbursts is
satisfied, in which the total gas depletion rate (dot{M}_gas = dot{M}_BH +
dot{M}_SF) is the one that scales as M_gas/t_orbital. We also found that the
`M_BH - sigma' relation is a byproduct of the `M_BH - M_virial' relation in the
fueling controlled scenario.Comment: 12 pages, figures, submited to ApJ, email: [email protected]
Laser-Doppler gas-velocity instrument
Three-D instrument using a laser light source measures both turbulence and mean velocity of subsonic and supersonic gas flows. This instrument is based on the measurement of the Doppler frequency shift of light waves scattered by moving particles in the gas stream
Reionization Constraints on the Contribution of Primordial Compact Objects to Dark Matter
Many lines of evidence suggest that nonbaryonic dark matter constitutes
roughly 30% of the critical closure density, but the composition of this dark
matter is unknown. One class of candidates for the dark matter is compact
objects formed in the early universe, with typical masses M between 0.1 and 1
solar masses to correspond to the mass scale of objects found with microlensing
observing projects. Specific candidates of this type include black holes formed
at the epoch of the QCD phase transition, quark stars, and boson stars. Here we
show that accretion onto these objects produces substantial ionization in the
early universe, with an optical depth to Thomson scattering out to z=1100 of
approximately tau=2-4 [f_CO\epsilon_{-1}(M/Msun)]^{1/2} (H_0/65)^{-1}, where
\epsilon_{-1} is the accretion efficiency \epsilon\equiv L/{\dot M}c^2 divided
by 0.1 and f_CO is the fraction of matter in the compact objects. The current
upper limit to the scattering optical depth, based on the anisotropy of the
microwave background, is approximately 0.4. Therefore, if accretion onto these
objects is relatively efficient, they cannot be the main component of
nonbaryonic dark matter.Comment: 12 pages including one figure, uses aaspp4, submitted to Ap
Improvement of Pheromone Trapping in Low Density Populations of \u3ci\u3eChoristoneura Pinus Pinus\u3c/i\u3e (Lepidoptera: Tortricidae)
Pheromone baited bucket traps (e.g., Multipher) are popular as a monitoring tool for the jack pine budworm, Choristoneura pinus pinus Freeman (Lepidoptera: Tortricidae), in Canada. However, there is no evidence to support their use when budworm populations are low. We therefore evaluated the capture rate of bucket traps at two placement heights (2 vs 6 m) in two jack pine forests in 2011, having low (≤5 fifth instars per mfoliated branch length) budworm populations. Compared to wing traps (e.g., Pherocon 1C), the trap design used initially to evaluate efficacy of the C. pinus pheromone, bucket traps caught fewer C. pinus and capture rates of both trap designs did not differ significantly between the two heights tested. Loss of bucket traps at 2 m, due to black bears, suggested that higher placement of traps was warranted to maintain the integrity of the array. However, wing traps are recommended due to their ability to consistently catch more moths when C. pinus populations are low
Laser Doppler velocity instrument
Laser Doppler velocity instrument for measuring turbulence and mean velocity in subsonic and supersonic gas flow
Top-Down Fragmentation of a Warm Dark Matter Filament
We present the first high-resolution n-body simulations of the fragmentation
of dark matter filaments. Such fragmentation occurs in top-down scenarios of
structure formation, when the dark matter is warm instead of cold. In a
previous paper (Knebe et al. 2002, hereafter Paper I), we showed that WDM
differs from the standard Cold Dark Matter (CDM) mainly in the formation
history and large-scale distribution of low-mass haloes, which form later and
tend to be more clustered in WDM than in CDM universes, tracing more closely
the filamentary structures of the cosmic web. Therefore, we focus our
computational effort in this paper on one particular filament extracted from a
WDM cosmological simulation and compare in detail its evolution to that of the
same CDM filament. We find that the mass distribution of the halos forming via
fragmentation within the filament is broadly peaked around a Jeans mass of a
few 10^9 Msun, corresponding to a gravitational instability of smooth regions
with an overdensity contrast around 10 at these redshifts. Our results confirm
that WDM filaments fragment and form gravitationally bound haloes in a top-down
fashion, whereas CDM filaments are built bottom-up, thus demonstrating the
impact of the nature of the dark matter on dwarf galaxy properties.Comment: 7 pages, 7 figures, replaced with MNRAS accepted version (minor
revisions
A SuperMassive Black Hole Fundamental Plane for Ellipticals
We obtain the coefficients of a new fundamental plane for supermassive black
holes at the centers of elliptical galaxies, involving measured central black
hole mass and photometric parameters which define the light distribution. The
galaxies are tightly distributed around this mass fundamental plane, with
improvement in the rms residual over those obtained from the \mbh-\sigma and
\mbh-L relations. This implies a strong multidimensional link between the
central massive black hole formation and global photometric properties of
elliptical galaxies and provides an improved estimate of black hole mass from
galaxy data.Comment: Accepted for publication in ApJ Letter
Recent star formation in high-redshift early-type galaxies: insights from the rest-frame UV
We combine deep UBVRIzJK photometry from the MUSYC survey with redshifts from
the COMBO-17 survey to study the rest-frame ultraviolet (UV) properties of 674
high-redshift (0.5<z<1) early-type galaxies, drawn from the Extended Chandra
Deep Field South (E-CDFS). Galaxy morphologies are determined through visual
inspection of Hubble Space Telescope (HST) images taken from the GEMS survey.
We harness the sensitivity of the UV to young (<1 Gyrs old) stars to quantify
the recent star formation history of the early-type population. We find
compelling evidence that early-types of all luminosities form stars over the
lifetime of the Universe, although the bulk of their star formation is already
complete at high redshift. Luminous (-23<M(V)<-20.5) early-types form 10-15
percent of their mass after z=1, while their less luminous (M(V)>-20.5)
counterparts form 30-60 percent of their mass in the same redshift range.Comment: To appear in the proceedings of the IAU 245, eds. M. Bureau, E.
Athanassoula, and B. Barbu
- …