Determining the Hubble Constant with Black Hole Mergers in Active Galactic Nuclei

Gravitational waves from neutron star mergers have long been considered a promising way to measure the Hubble constant, $H_0$, which describes the local expansion rate of the Universe. While black hole mergers are more abundantly observed, their expected lack of electromagnetic emission and poor gravitational-wave localization makes them less suited for measuring $H_0$. Black hole mergers within the disks of Active Galactic Nuclei (AGN) could be an exception. Accretion from the AGN disk may produce an electromagnetic signal, pointing observers to the host galaxy. Alternatively, the low number density of AGNs could help identify the host galaxy of $1-5\%$ of mergers. Here we show that black hole mergers in AGN disks may be the most sensitive way to determine $H_0$ with gravitational waves. If 1% of LIGO/Virgo's observations occur in AGN disks with identified host galaxies, we could measure $H_0$ with 1% uncertainty within five years, likely beyond the sensitivity of neutrons star mergers.Comment: 4 pages, 2 figure

Synthesis, spectroscopy and structural elucidation of two new CoII and NiII complexes of pyrazole derived heterocyclic Schiff base ligand as potential anticancer and photocatalytic agents

Dr. Arunima Biswas has received research grant from West Bengal DBT, vide grant no. (676/(Sanc.)/BT/(Estt.)/RD27/2016).Two new complexes I and II of general composition, [ML3]X2.nH2O (where, M = CoII and NiII for I and II, respectively, L = MPAFA, X = Br and n = 2) were synthesized from a pyrazolyl Schiff base ligand, MPAFA (L). I and II were characterised through several physico-chemical and spectroscopic techniques, viz., C, H, N analyses, estimation of metal contents, conductance and magnetic susceptibility measurements, IR, electronic and fluorescence spectral studies. Both the reported coordination complexes were cationic in nature and behaved as 1:2 electrolytes. According to IR spectra, each of the MPAFA molecule coordinated to the metal centres via the azomethine nitrogen and the pyrazolyl tertiary nitrogen atoms. Single crystal X-ray diffraction studies of I and II had established a N6 donor set with a distorted octahedral structure for both the cases. Both the complexes exhibited some non-covalent interactions, like π…π stacking, H-bonding contacts etc. L, I and II had also been found to possess fluorescence property. Anticancer activities of L, I and II had been investigated and it was found that both the complexes I and II were stronger cytotoxic agents against the breast cancer cell line MCF7 than the primary ligand system; while all of them (L, I and II) were less toxic against a non-cancerous cell line HEK293. All the compounds had shown potential photocatalytic activity in degrading methylene-blue (MB).Peer reviewe

The quijote simulations

The Quijote simulations are a set of 44,100 full N-body simulations spanning more than 7000 cosmological models in the hyperplane. At a single redshift, the simulations contain more than 8.5 trillion particles over a combined volume of 44,100 each simulation follows the evolution of 2563, 5123, or 10243 particles in a box of 1 h -1 Gpc length. Billions of dark matter halos and cosmic voids have been identified in the simulations, whose runs required more than 35 million core hours. The Quijote simulations have been designed for two main purposes: (1) to quantify the information content on cosmological observables and (2) to provide enough data to train machine-learning algorithms. In this paper, we describe the simulations and show a few of their applications. We also release the petabyte of data generated, comprising hundreds of thousands of simulation snapshots at multiple redshifts; halo and void catalogs; and millions of summary statistics, such as power spectra, bispectra, correlation functions, marked power spectra, and estimated probability density functions

Search for post-merger gravitational waves from the remnant of the binary neutron star merger GW170817

In Advanced LIGO, detection and astrophysical source parameter estimation of the binary black hole merger GW150914 requires a calibrated estimate of the gravitational-wave strain sensed by the detectors. Producing an estimate from each detector's differential arm length control loop readout signals requires applying time domain filters, which are designed from a frequency domain model of the detector's gravitational-wave response. The gravitational-wave response model is determined by the detector's opto-mechanical response and the properties of its feedback control system. The measurements used to validate the model and characterize its uncertainty are derived primarily from a dedicated photon radiation pressure actuator, with cross-checks provided by optical and radio frequency references. We describe how the gravitational-wave readout signal is calibrated into equivalent gravitational-wave-induced strain and how the statistical uncertainties and systematic errors are assessed. Detector data collected over 38 calendar days, from September 12 to October 20, 2015, contain the event GW150914 and approximately 16 of coincident data used to estimate the event false alarm probability. The calibration uncertainty is less than 10% in magnitude and 10 degrees in phase across the relevant frequency band 20 Hz to 1 kHz

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

In Advanced LIGO, detection and astrophysical source parameter estimation of the binary black hole merger GW150914 requires a calibrated estimate of the gravitational-wave strain sensed by the detectors. Producing an estimate from each detector's differential arm length control loop readout signals requires applying time domain filters, which are designed from a frequency domain model of the detector's gravitational-wave response. The gravitational-wave response model is determined by the detector's opto-mechanical response and the properties of its feedback control system. The measurements used to validate the model and characterize its uncertainty are derived primarily from a dedicated photon radiation pressure actuator, with cross-checks provided by optical and radio frequency references. We describe how the gravitational-wave readout signal is calibrated into equivalent gravitational-wave-induced strain and how the statistical uncertainties and systematic errors are assessed. Detector data collected over 38 calendar days, from September 12 to October 20, 2015, contain the event GW150914 and approximately 16 of coincident data used to estimate the event false alarm probability. The calibration uncertainty is less than 10% in magnitude and 10 degrees in phase across the relevant frequency band 20 Hz to 1 kHz