5,496 research outputs found
Dark Matter annihilation energy output and its effects on the high-z IGM
We study the case of DM self annihilation, in order to assess its importance
as an energy injection mechanism, to the IGM in general, and to the medium
within particular DM haloes. We consider thermal relic WIMP particles with
masses of 10GeV and 1TeV and we analyse in detail the clustering properties of
DM in a CDM cosmology, on all hierarchy levels, from haloes and their
mass function, to subhaloes and the DM density profiles within them,
considering adiabatic contraction by the presence of a SMBH. We then compute
the corresponding energy output, concluding that DM annihilation does not
constitute an important feedback mechanism. We also calculate the effects that
DM annihilation has on the IGM temperature and ionization fraction, and we find
that assuming maximal energy absorption, at z ~ 10, for the case of a 1TeV
WIMP, the ionization fraction could be raised to and the
temperature to 10K, and in the case of a 10GeV WIMP, the IGM temperature could
be raised to 200K and the ionization fraction to . We
conclude that DM annihilations cannot be regarded as an alternative
reionization scenario. Regarding the detectability of the WIMP through the
modifications to the 21 cm differential brightness temperature signal
(Tb), we conclude that a thermal relic WIMP with mass of 1TeV is not
likely to be detected from the global signal alone, except perhaps at the 1-3mK
level in the frequency range 30MHz < < 35MHz corresponding to 40 < z <
46. However, a 10GeV mass WIMP may be detectable at the 1-3mK level in the
frequency range 55MHz < < 119MHz corresponding to 11 < z < 25, and at the
1-10mK level in the frequency range 30MHz < < 40MHz corresponding to 35 <
z < 46.Comment: 23 pages, 12 figures, accepted for publication in MNRA
Frequency domain analysis of the mean and osculating trajectories of LAGEOS-1
Several crucial developments in orbital mechanics are obtained through the method of averaging, which is equivalent to integrating only the dominant harmonics of the Fourier series of the dynamics. Frequency analysis of the trajectory expressed in orbital elements facilitates an in-depth understanding of Earth satellite dynamics, and facilitates the interpretation of numerical results from special perturbations within the theoretical framework of celestial mechanics. In this work, we examine recent Two-Line Element series for LAGEOS-1 in the frequency domain, highlighting the presence of short-periodic terms that are likely introduced in the generation of TLEs from observations. We also propose employing well-established methods from signal processing, such as spectrograms, to examine the evolution of dissipative systems such as satellites in LEO
Discovery of 6.035GHz Hydroxyl Maser Flares in IRAS18566+0408
We report the discovery of 6.035GHz hydroxyl (OH) maser flares toward the
massive star forming region IRAS18566+0408 (G37.55+0.20), which is the only
region known to show periodic formaldehyde (4.8 GHz H2CO) and methanol (6.7 GHz
CH3OH) maser flares. The observations were conducted between October 2008 and
January 2010 with the 305m Arecibo Telescope in Puerto Rico. We detected two
flare events, one in March 2009, and one in September to November 2009. The OH
maser flares are not simultaneous with the H2CO flares, but may be correlated
with CH3OH flares from a component at corresponding velocities. A possible
correlated variability of OH and CH3OH masers in IRAS18566+0408 is consistent
with a common excitation mechanism (IR pumping) as predicted by theory.Comment: Accepted for publication in the Astrophysical Journa
High Resolution Observations of the Massive Protostar in IRAS18566+0408
We report 3 mm continuum, CH3CN(5-4) and 13CS(2-1) line observations with
CARMA, in conjunction with 6 and 1.3 cm continuum VLA data, and 12 and 25
micron broadband data from the Subaru Telescope toward the massive proto-star
IRAS18566+0408. The VLA data resolve the ionized jet into 4 components aligned
in the E-W direction. Radio components A, C, and D have flat cm SEDs indicative
of optically thin emission from ionized gas, and component B has a spectral
index alpha = 1.0, and a decreasing size with frequency proportional to
frequency to the -0.5 power. Emission from the CARMA 3 mm continuum, and from
the 13CS(2-1), and CH3CN(5-4) spectral lines is compact (i.e. < 6700 AU), and
peaks near the position of VLA cm source, component B. Analysis of these lines
indicates hot, and dense molecular gas, typical for HMCs. Our Subaru telescope
observations detect a single compact source, coincident with radio component B,
demonstrating that most of the energy in IRAS18566+0408 originates from a
region of size < 2400 AU. We also present UKIRT near-infrared archival data for
IRAS18566+0408 which show extended K-band emission along the jet direction. We
detect an E-W velocity shift of about 10 km/sec over the HMC in the CH3CN lines
possibly tracing the interface of the ionized jet with the surrounding core
gas. Our data demonstrate the presence of an ionized jet at the base of the
molecular outflow, and support the hypothesis that massive protostars with
O-type luminosity form with a mechanism similar to lower mass stars
Long-term Variability of HCO Masers in Star-forming Regions
We present results of a multi-epoch monitoring program on variability of
6cm formaldehyde (HCO) masers in the massive star forming region
NGC7538IRS1 from 2008 to 2015 conducted with the GBT, WSRT, and
VLA. We found that the similar variability behaviors of the two formaldehyde
maser velocity components in NGC7538IRS1 (which was pointed out by
Araya and collaborators in 2007) have continued. The possibility that the
variability is caused by changes in the maser amplification path in regions
with similar morphology and kinematics is discussed. We also observed
12.2GHz methanol and 22.2GHz water masers toward
NGC7538IRS1. The brightest maser components of CHOH and HO
species show a decrease in flux density as a function of time. The brightest
HCO maser component also shows a decrease in flux density and has a similar
LSR velocity to the brightest HO and 12.2GHz CHOH masers. The line
parameters of radio recombination lines and the 20.17 and 20.97GHz CHOH
transitions in NGC7538IRS1 are also reported. In addition, we
observed five other 6cm formaldehyde maser regions. We found no evidence of
significant variability of the 6cm masers in these regions with respect to
previous observations, the only possible exception being the maser in
G29.960.02. All six sources were also observed in the HCO
isotopologue transition of the 6cm HCO line; HCO absorption
was detected in five of the sources. Estimated column density ratios
[HCO]/[HCO] are reported.Comment: 29 pages, 9 figure
Hadamard matrices of orders 60 and 64 with automorphisms of orders 29 and 31
A classification of Hadamard matrices of order with an automorphism of
order is given for and . The ternary self-dual codes spanned by
the newly found Hadamard matrices of order with an automorphism of order
are computed, as well as the binary doubly even self-dual codes of length
with generator matrices defined by related Hadamard designs. Several new
ternary near-extremal self-dual codes, as well as binary near-extremal doubly
even self-dual codes with previously unknown weight enumerators are found.Comment: 21 page
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