Search Publications
Changing physical conditions in star-forming galaxies between redshifts 0 < z < 4: [O III]/H β evolution
Bowler, R. A. A.; Cullen, F.; McLure, R. J. +3 more
We investigate the redshift evolution of the [O III]/H β nebular emission line ratio for a sample of galaxies spanning the redshift range 0 < z < 4. We compare the observed evolution to a set of theoretical models which account for the independent evolution of chemical abundance, ionization parameter and interstellar medium (ISM) pressure in…
Evidence for large-scale subsurface convection in the Sun
Woodard, M. F.
A helioseismic statistical waveform analysis of subsurface flow was performed on two 720-day time series of SOHO/Michelson Doppler Imager medium-l spherical-harmonic coefficients. The time series coincide with epochs of high and low solar activity. Time-dependent coupling-strength coefficients b^t_s(n,l) of modes of the same radial order n and deg…
The nature of the torus in the heavily obscured AGN Markarian 3: an X-ray study
Harrison, F.; Stern, D.; Bauer, F. E. +22 more
In this paper, we report the results of an X-ray monitoring campaign on the heavily obscured Seyfert galaxy, Markarian 3, carried out between the fall of 2014 and the spring of 2015 with NuSTAR, Suzaku and XMM-Newton. The hard X-ray spectrum of Markarian 3 is variable on all the time-scales probed by our campaign, down to a few days. The observed …
The NuSTAR view of the non-thermal emission from PSR J0437-4715
Harrison, F. A.; Boggs, S.; Stern, D. +11 more
We present a hard X-ray Nuclear Spectroscopic Telescope Array (NuSTAR) observation of PSR J0437-4715, the nearest millisecond pulsar. The known pulsations at the apparent pulse period {∼ }5.76{ ms} are observed with a significance of 3.7σ, at energies up to 20 keV above which the NuSTAR background dominates. We measure a photon index Γ = 1.50 ± 0.…
The bulge-disc decomposition of AGN host galaxies
Dunlop, J. S.; Kocevski, D. D.; Rosario, D. J. +3 more
We present the results from a study of the morphologies of moderate luminosity X-ray-selected active galactic nuclei (AGN) host galaxies in comparison to a carefully mass-matched control sample at 0.5 < z < 3 in the CANDELS GOODS-S field. We apply a multiwavelength morphological decomposition analysis to these two samples and report on the d…
The view of AGN-host alignment via reflection spectroscopy
Fabian, Andrew C.; Reynolds, Christopher S.; Middleton, Matthew J. +2 more
The fuelling of active galactic nuclei (AGN) - via material propagated through the galactic disc or via minor mergers - is expected to leave an imprint on the alignment of the sub-pc disc relative to the host galaxy's stellar disc. Determining the inclination of the inner disc usually relies on the launching angle of the jet; here instead we use t…
Peak of spectral energy distribution plays an important role in intra-day variability of blazars?
Gupta, Alok C.; Kalita, Nibedita; Gaur, Haritma +1 more
Blazars can be divided into two sub-classes namely high energy and low energy peaked blazars. In spectral energy distribution, the first synchrotron hump of the former class peaks in UV/X-rays and in IR/optical bands for the latter class. The peak of the spectral energy distribution seems to be responsible for variability properties of these class…
A pair of O VI and broad Ly α absorbers probing warm gas in a galaxy group environment at z ∼ 0.4
Savage, Blair D.; Wakker, Bart P.; Muzahid, Sowgat +4 more
We report the detection of two O VI absorbers at z = 0.416 14 and 0.419 50 (|Δv| = 710 km s-1), towards SBS 0957+599. Both absorbers are multiphase systems tracing substantial reservoirs of warm baryons. The low- and intermediate-ionization metals in the z = 0.416 14 absorber are consistent with an origin in photoionized gas. O VI has a…
Origin and evolution of two-component debris discs and an application to the q1 Eridani system
Kirchschlager, Florian; Booth, Mark; Krivov, Alexander V. +3 more
Many debris discs reveal a two-component structure, with an outer Kuiper-belt analogue and a warm inner component whose origin is still a matter of debate. One possibility is that warm emission stems from an `asteroid belt' closer in to the star. We consider a scenario in which a set of giant planets is formed in an initially extended planetesimal…
X-ray, UV and optical analysis of supergiants: ɛ Ori
Hillier, D. John; Leutenegger, Maurice A.; Cohen, David H. +2 more
We present a multi-wavelength (X-ray to optical) analysis, based on non-local thermodynamic equilibrium photospheric+wind models, of the B0 Ia-supergiant: ɛ Ori. The aim is to test the consistency of physical parameters, such as the mass-loss rate and CNO abundances, derived from different spectral bands. The derived mass-loss rate is {dot {M}} / …