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تسجيل مستخدم جديدUsing temporal distributions of transient events to characterize cosmological source populations
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The brightest events in a time series of cosmological transients obey an observation time dependence which is often overlooked. This dependence can be exploited to probe the global properties of electromagnetic and gravitational wave transients (Howell et al. 2007a, Coward & Burman 2005). We describe a new relation based on a peak flux--observation time distribution and show that it is invariant to the luminosity distribution of the sources (Howell et al. 2007b). Applying this relation, in combination with a new data analysis filter, to emph{Swift} gamma-ray burst data, we demonstrate that it can constrain their rate density.
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The Omicron software is a tool developed to perform a multi-resolution time-frequency analysis of data from gravitational-wave detectors: the LIGO, Virgo, and KAGRA detectors. Omicron generates spectrograms from whitened data streams, offering a visu
al representation of transient detector noises and gravitational-wave events. In addition, these events can be parameterized with an optimized resolution. They can be written to disk to conduct offline noise characterization and gravitational-wave event validation studies. Omicron is optimized to process, in parallel, thousands of data streams recorded by gravitational-wave detectors. The Omicron software plays an important role in vetting gravitational-wave detection candidates and characterization of transient noise.
We investigate the properties of galaxies as they shut off star formation over the 4 billion years surrounding peak cosmic star formation. To do this we categorize $sim7000$ galaxies from $1<z<4$ into $90$ groups based on the shape of their spectral
energy distributions (SEDs) and build composite SEDs with $Rsim 50$ resolution. These composite SEDs show a variety of spectral shapes and also show trends in parameters such as color, mass, star formation rate, and emission line equivalent width. Using emission line equivalent widths and strength of the 4000AA break, $D(4000)$, we categorize the composite SEDs into five classes: extreme emission line, star-forming, transitioning, post-starburst, and quiescent galaxies. The transitioning population of galaxies show modest H$alpha$ emission ($EW_{rm REST}sim40$AA) compared to more typical star-forming composite SEDs at $log_{10}(M/M_odot)sim10.5$ ($EW_{rm REST}sim80$AA). Together with their smaller sizes (3 kpc vs. 4 kpc) and higher Sersic indices (2.7 vs. 1.5), this indicates that morphological changes initiate before the cessation of star formation. The transitional group shows a strong increase of over one dex in number density from $zsim3$ to $zsim1$, similar to the growth in the quiescent population, while post-starburst galaxies become rarer at $zlesssim1.5$. We calculate average quenching timescales of 1.6 Gyr at $zsim1.5$ and 0.9 Gyr at $zsim2.5$ and conclude that a fast quenching mechanism producing post-starbursts dominated the quenching of galaxies at early times, while a slower process has become more common since $zsim2$.
We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors
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The detection of gravitational waves from neutron star merger events has opened up a new field of multi-messenger astronomy linking gravitational waves events to short-gamma ray bursts and kilonova afterglows. A further - yet to be discovered - elect
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