7,973 research outputs found
Observing complete gravitational wave signals from dynamical capture binaries
We assess the detectability of the gravitational wave signals from highly
eccentric compact binaries. We use a simple model for the inspiral, merger, and
ringdown of these systems. The model is based on mapping the binary to an
effective single black hole system described by a Kerr metric, thereby
including certain relativistic effects such as zoom-whirl-type behavior. The
resultant geodesics source quadrupolar radiation and, in turn, are evolved
under its dissipative effects. At the light ring, we attach a merger model that
was previously developed for quasicircular mergers but also performs well for
eccentric mergers with little modification. We apply this model to determine
the detectability of these sources for initial, Enhanced, and Advanced LIGO
across the parameter space of nonspinning close capture compact binaries. We
conclude that, should these systems exist in nature, the vast majority will be
missed by conventional burst searches or by quasicircular waveform templates in
the advanced detector era. Other methods, such as eccentric templates or, more
practically, a stacked excess power search, must be developed to avoid losing
these sources. These systems would also have been missed frequently in the
initial LIGO data analysis. Thus, previous null coincidence results with
detected gamma-ray bursts cannot exclude the possibility of coincident
gravitational wave signals from eccentric binaries.Comment: 18 pages, 18 figures; revised to match accepted version, PRD in pres
Less than 10 percent of star formation in z=0.6 massive galaxies is triggered by major interactions
Both observations and simulations show that major tidal interactions or
mergers between gas-rich galaxies can lead to intense bursts of starformation.
Yet, the average enhancement in star formation rate (SFR) in major mergers and
the contribution of such events to the cosmic SFR are not well estimated. Here
we use photometric redshifts, stellar masses and UV SFRs from COMBO-17, 24
micron SFRs from Spitzer and morphologies from two deep HST cosmological survey
fields (ECDFS/GEMS and A901/STAGES) to study the enhancement in SFR as a
function of projected galaxy separation. We apply two-point projected
correlation function techniques, which we augment with morphologically-selected
very close pairs (separation <2 arcsec) and merger remnants from the HST
imaging. Our analysis confirms that the most intensely star-forming systems are
indeed interacting or merging. Yet, for massive (M* > 10^10 Msun) star-forming
galaxies at 0.4<z<0.8, we find that the SFRs of galaxies undergoing a major
interaction (mass ratios <1:4 and separations < 40 kpc) are only 1.80 +/- 0.30
times higher than the SFRs of non-interacting galaxies when averaged over all
interactions and all stages of the interaction, in good agreement with other
observational works.
We demonstrate that these results imply that <10% of star formation at 0.4 <
z < 0.8 is triggered directly by major mergers and interactions; these events
are not important factors in the build-up of stellar mass since z=1.Comment: Submitted to ApJ. 41 pages, 11 figure
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