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First search for gravitational waves from known pulsars with advanced LIGO

We present the result of searches for gravitational waves from 200 pulsars using data from the first observing run of the Advanced LIGO detectors. We find no significant evidence for a gravitational-wave signal from any of these pulsars, but we are able to set the most constraining upper limits yet on their gravitational-wave amplitudes and ellipticities. For eight of these pulsars, our upper limits give bounds that are improvements over the indirect spin-down limit values. For another 32, we are within a factor of 10 of the spin-down limit, and it is likely that some of these will be reachable in future runs of the advanced detector. Taken as a whole, these new results improve on previous limits by more than a factor of two.

Author: Powell, J.
Publication year: 2017
Publication type: Journal article
Source: The Astrophysical Journal
Status: Live|Last updated:7 December 2017 6:32 PM
Relevance: 0.215
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Polarimetry of the Eclipsing Pulsar PSR J1748–2446A

Observations with the Parkes radio telescope of the eclipsing millisecond binary pulsar PSR J1748-2446A, which is in the globular cluster Terzan 5, are presented. These include the first observations of this pulsar in the 3 GHz frequency band, along with simultaneous observations in the 700 MHz band, and new observations around 1400 MHz. We show that the pulsar signal is not eclipsed in the 3 GHz band and observe the known eclipses in the lower-frequency bands. We find that the observed pulse signal becomes depolarized during particular orbital phases and postulate that this depolarization occurs because of rotation-measure fluctuations resulting from turbulence in the stellar wind responsible for the eclipses.

Author: You, X. P., Manchester, R. N., Coles, W. A., Hobbs, G. B., Shannon, R.
Publication year: 2018
Publication type: Journal article
Source: The Astrophysical Journal
Status: Live|Last updated:13 November 2018 5:32 PM
Relevance: 0.215
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The influence of host galaxies in type Ia supernova cosmology

We use a sample of 1338 spectroscopically confirmed and photometrically classified Type Ia supernovae (SNe Ia) sourced from Carnegie Supernova Project, Center for Astrophysics Supernova Survey, Sloan Digital Sky Survey-II, and SuperNova Legacy Survey SN samples to examine the relationships between SNe Ia and the galaxies that host them. Our results provide confirmation with improved statistical significance that SNe Ia, after standardization, are on average more luminous in massive hosts (significance >5σ), and decline more rapidly in massive hosts (significance >9σ) and in hosts with low specific star formation rates (significance >8σ). We study the variation of these relationships with redshift and detect no evolution. We split SNe Ia into pairs of subsets that are based on the properties of the hosts and fit cosmological models to each subset. Including both systematic and statistical uncertainties, we do not find any significant shift in the best-fit cosmological parameters between the subsets. Among diff…

Author: Uddin, Syed A., Mould, Jeremy, Lidman, Chris, Ruhlmann-Kleider, Vanina...
Publication year: 2017
Publication type: Journal article
Source: Astrophysical Journal
Status: Live|Last updated:24 January 2019 3:28 PM
Relevance: 0.188
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Search for Multimessenger Sources of Gravitational Waves and High-energy Neutrinos with Advanced LIGO during its first observing run, ANTARES, and IceCube

Astrophysical sources of gravitational waves, such as binary neutron star and black hole mergers or core-collapse supernovae, can drive relativistic outflows, giving rise to non-thermal high-energy emission. High-energy neutrinos are signatures of such outflows. The detection of gravitational waves and high-energy neutrinos from common sources could help establish the connection between the dynamics of the progenitor and the properties of the outflow. We searched for associated emission of gravitational waves and high-energy neutrinos from astrophysical transients with minimal assumptions using data from Advanced LIGO from its first observing run O1, and data from the Antares and IceCube neutrino observatories from the same time period. We focused on candidate events whose astrophysical origins could not be determined from a single messenger. We found no significant coincident candidate, which we used to constrain the rate density of astrophysical sources dependent on their gravitational-wave and neutrino emi…

Author: Albert, A., Andre, M., Anghinolfi, M., Powell, J., Stevenson, S. P., L...
Publication year: 2019
Publication type: Journal article
Source: The Astrophysical Journal
Status: Live|Last updated:30 January 2019 3:33 PM
Relevance: 0.188
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LOFAR Observations of 4C+19.44: On the Discovery of Low-frequency Spectral Curvature in Relativistic Jet Knots

We present the first LOFAR observations of the radio jet in the quasar 4C+19.44 (a.k.a. PKS 1354+19) obtained with long baselines. The achieved resolution is very well matched to that of archival Jansky Very Large Array observations at higher radio frequencies as well as the archival X-ray images obtained with Chandra. We found that, for several knots along the jet, the radio flux densities measured at hundreds of MHz lie well below the values estimated by extrapolating the GHz spectra. This clearly indicates the presence of spectral curvature. Radio spectral curvature has already been observed in different source classes and/or extended radio structures, and it has been often interpreted as due to intrinsic processes, as a curved particle energy distribution, rather than absorption mechanisms (Razin-Tsytovich effect, free-free or synchrotron self absorption to name a few). Here, we discuss our results according to the scenario where particles undergo stochastic acceleration mechanisms also in quasar jet knot…

Author: Harris, D. E., Moldon, J., Oonk, J. R. R., Massaro, F., Paggi, A., Del...
Publication year: 2019
Publication type: Journal article
Source: The Astrophysical Journal
Status: Live|Last updated:15 March 2019 12:32 PM
Relevance: 0.188
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Galaxy and mass assembly (gama): Impact of the group environment on galaxy star formation

We explore how the group environment may affect the evolution of star-forming galaxies. We select 1197 Galaxy And Mass Assembly groups at 0.05 ≤ z ≤ 0.2 and analyze the projected phase space (PPS) diagram, i.e., the galaxy velocity as a function of projected group-centric radius, as a local environmental metric in the low-mass halo regime 1012 ≤ (M 200/M o) < 1014. We study the properties of star-forming group galaxies, exploring the correlation of star formation rate (SFR) with radial distance and stellar mass. We find that the fraction of star-forming group members is higher in the PPS regions dominated by recently accreted galaxies, whereas passive galaxies dominate the virialized regions. We observe a small decline in specific SFR of star-forming galaxies toward the group center by a factor ∼1.2 with respect to field galaxies. Similar to cluster studies, we conclude for low-mass halos that star-forming group galaxies represent an infalling population from the field to the halo and show suppressed star for…

Author: Barsanti, S., Owers, M. S., Brough, S., Davies, L. J.M., Driver, S. P....
Publication year: 2018
Publication type: Journal article
Source: Astrophysical Journal
Status: Live|Last updated:24 January 2019 3:37 PM
Relevance: 0.188
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Search for gravitational waves associated with gamma-ray bursts during the first advanced LIGO observing run and implications for the origin of GRB 150906B

We present the results of the search for gravitational waves (GWs) associated with γ-ray bursts detected during the first observing run of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO). We find no evidence of a GW signal for any of the 41 γ-ray bursts for which LIGO data are available with sufficient duration. For all γ-ray bursts, we place lower bounds on the distance to the source using the optimistic assumption that GWs with an energy of ${10}^{-2}{M}_{\odot }{c}^{2}$ were emitted within the $16$–$500$ Hz band, and we find a median 90% confidence limit of 71 Mpc at 150 Hz. For the subset of 19 short/hard γ-ray bursts, we place lower bounds on distance with a median 90% confidence limit of 90 Mpc for binary neutron star (BNS) coalescences, and 150 and 139 Mpc for neutron star–black hole coalescences with spins aligned to the orbital angular momentum and in a generic configuration, respectively. These are the highest distance limits ever achieved by GW searches. We also discuss in d…

Author: Powell, J.
Publication year: 2017
Publication type: Journal article
Source: The Astrophysical Journal
Status: Live|Last updated:7 December 2017 5:32 PM
Relevance: 0.161
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The dearth of z ∼ 10 galaxies in all HST legacy fields - the rapid evolution of the galaxy population in the first 500 myr

We present an analysis of all prime HST legacy fields spanning >800 arcmin2 in the search for z ∼ 10 galaxy candidates and the study of their UV luminosity function (LF). In particular, we present new z ∼ 10 candidates selected from the full Hubble Frontier Field (HFF) data set. Despite the addition of these new fields, we find a low abundance of z ∼ 10 candidates with only nine reliable sources identified in all prime HST data sets that include the HUDF09/12, the HUDF/XDF, all of the CANDELS fields, and now the HFF survey. Based on this comprehensive search, we find that the UV luminosity function decreases by one order of magnitude from z ∼ 8 to z ∼ 10 over a four-magnitude range. This also implies a decrease of the cosmic star formation rate density by an order of magnitude within 170 Myr from z ∼ 8 to z ∼ 10. We show that this accelerated evolution compared to lower redshift can entirely be explained by the fast build up of the dark matter halo mass function at z > 8. Consequently, the predicted UV LFs fr…

Author: Oesch, P. A., Bouwens, R. J., Illingworth, G. D., Labbe, I., Stefanon,...
Publication year: 2018
Publication type: Journal article
Source: Astrophysical Journal
Status: Live|Last updated:18 May 2018 4:32 PM
Relevance: 0.161
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The AGN ionization cones of NGC 5728. I. Excitation and nuclear structure

We explore the gas morphology and excitation mechanisms of the ionization cones of the Type II Seyfert galaxy NGC 5728. Near-IR and optical data from the SINFONI and MUSE integral field units on the Very Large Telescope are combined with Hubble Space Telescope optical images, Chandra X-ray data, and Very Large Array radio observations. The complex nuclear structure has a star-forming (SF) ring with a diameter of 2 kpc. A radio jet impacts on the interstellar medium at about 200 pc from the nucleus, with the supernova remnants in the SF ring also present. Emission-line ratios of [Fe ii] and H ii show heavy extinction toward the nucleus, moderate extinction in the SF ring, and reduced extinction in the ionization cones. The active galactic nucleus (AGN) is hidden by a dust bar with up to 19 mag of visual extinction; the dust temperature at the nuclear position is ∼870 K. An X-ray jet is aligned with the ionization cones and associated with high-excitation emission lines of [Si vi] in a coronal line region exten…

Author: Durre, Mark, Mould, Jeremy
Publication year: 2018
Publication type: Journal article
Source: The Astrophysical Journal
Status: Live|Last updated:24 January 2019 3:39 PM
Relevance: 0.161
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Unique tracks drive the scatter of the spatially resolved star formation main sequence

The scatter of the spatially resolved star formation main sequence (SFMS) is investigated in order to reveal signatures about the processes of galaxy formation and evolution. We have assembled a sample of 355 nearby galaxies with spatially resolved H and mid-infrared fluxes from the Survey for Ionized Neutral Gas in Galaxies and the Wide-field Infrared Survey Explorer, respectively. We examine the impact of various star formation rate (SFR) and stellar mass transformations on the SFMS. Ranging from 106 to 1011.5 M o and derived from color to mass-to-light ratio methods for mid-infrared bands, the stellar masses are internally consistent within their range of applicability and inherent systematic errors; a constant mass-to-light ratio also yields representative stellar masses. The various SFR estimates show intrinsic differences and produce noticeable vertical shifts in the SFMS, depending on the timescales and physics encompassed by the corresponding tracer. SFR estimates appear to break down on physical scal…

Author: Hall, Christine, Courteau, Stephane, Jarrett, Thomas, Cluver, Michelle...
Publication year: 2018
Publication type: Journal article
Source: The Astrophysical Journal
Status: Live|Last updated:24 October 2018 10:32 AM
Relevance: 0.161
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