Search Publications
Black Hole-Galaxy Scaling Relationships for Active Galactic Nuclei with Reverberation Masses
Bentz, Misty C.; Manne-Nicholas, Emily
We have utilized high-resolution optical Hubble Space Telescope images and deep, ground-based near-infrared images to examine the host galaxies of 37 active galactic nuclei (AGNs) with reverberation-based black hole masses. Using two-dimensional image decompositions, we have separated the host galaxy from the bright central AGN, allowing a re-exam…
A comparison of the local spiral structure from Gaia DR2 and VLBI maser parallaxes
Menten, K. M.; Xu, Y.; Zhang, B. +8 more
Context. The Gaia mission has released the second data set (Gaia DR2), which contains parallaxes and proper motions for a large number of massive, young stars.
Aims: We investigate the spiral structure in the solar neighborhood revealed by Gaia DR2 and compare it with that depicted by VLBI maser parallaxes.
Methods: We examined three sam…
Starburst to Quiescent from HST/ALMA: Stars and Dust Unveil Minor Mergers in Submillimeter Galaxies at z ∼ 4.5
Magnelli, B.; Smolčić, V.; van Kampen, E. +32 more
Dust-enshrouded, starbursting, submillimeter galaxies (SMGs) at z ≥ 3 have been proposed as progenitors of z ≥ 2 compact quiescent galaxies (cQGs). To test this connection, we present a detailed spatially resolved study of the stars, dust, and stellar mass in a sample of six submillimeter-bright starburst galaxies at z ∼ 4.5. The stellar UV emissi…
Extreme Kinematics of the 2017 September 10 Solar Eruption and the Spectral Characteristics of the Associated Energetic Particles
Gopalswamy, N.; Yashiro, S.; Mäkelä, P. +3 more
We report on the 2017 September 10 ground-level enhancement (GLE) event associated with a coronal mass ejection whose initial acceleration (∼9.1 km s-2) and initial speed (∼4300 km s-1) were among the highest observed in the Solar and Heliospheric Observatory era. The GLE event was of low intensity (∼4.4% above background) an…
Supervised machine learning for analysing spectra of exoplanetary atmospheres
Heng, Kevin; Fisher, Chloe; Márquez-Neila, Pablo +1 more
The use of machine learning is becoming ubiquitous in astronomy1-3, but remains rare in the study of the atmospheres of exoplanets. Given the spectrum of an exoplanetary atmosphere, a multi-parameter space is swept through in real time to find the best-fit model4-6. Known as atmospheric retrieval, this technique originates in…
Three-dimensional Circulation Driving Chemical Disequilibrium in WASP-43b
Mendonça, João M.; Heng, Kevin; Tsai, Shang-min +2 more
Spectral features in the observed spectra of exoplanets depend on the composition of their atmospheres. A good knowledge of the main atmospheric processes that drive the chemical distribution is therefore essential to interpret exoplanetary spectra. An atmosphere reaches chemical equilibrium if the rates of the forward and backward chemical reacti…
An automatic taxonomy of galaxy morphology using unsupervised machine learning
Geach, James E.; Hocking, Alex; Sun, Yi +1 more
We present an unsupervised machine learning technique that automatically segments and labels galaxies in astronomical imaging surveys using only pixel data. Distinct from previous unsupervised machine learning approaches used in astronomy we use no pre-selection or pre-filtering of target galaxy type to identify galaxies that are similar. We demon…
A Potential Cyclotron Resonant Scattering Feature in the Ultraluminous X-Ray Source Pulsar NGC 300 ULX1 Seen by NuSTAR and XMM-Newton
Harrison, F. A.; Fabian, A. C.; Pinto, C. +14 more
Based on phase-resolved broadband spectroscopy using XMM-Newton and NuSTAR, we report on a potential cyclotron resonant scattering feature (CRSF) at E ∼ 13 keV in the pulsed spectrum of the recently discovered ultraluminous X-ray source (ULX) pulsar NGC 300 ULX1. If this interpretation is correct, the implied magnetic field of the central neutron …
Compton-thick AGNs in the NuSTAR Era
Vignali, C.; Comastri, A.; Ajello, M. +3 more
We present the 2-100 keV spectral analysis of 30 candidate Compton-thick-(CT-)active galactic nuclei (AGNs) selected in the Swift-Burst Alert Telescope (BAT) 100 month survey. The average redshift of these objects is < z> ∼ 0.03, and they all lie within ∼500 Mpc. We used the MyTorus model to perform X-ray spectral fittings both without and w…
Puzzling Lyman-alpha line profiles in green pea galaxies
Schaerer, D.; Scarlata, C.; Oey, M. S. +4 more
Context. The Lyman-alpha (Lyα) line of hydrogen is of prime importance for detecting galaxies at high redshift. For a correct data interpretation, numerical radiative transfer models are necessary due to Lyα resonant scattering off neutral hydrogen atoms.
Aims: Recent observations have discovered an escape of ionizing Lyman-continuum radiatio…