Sean Morrison
A5008161956- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Radio Astronomy Observations and Technology
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Spectroscopy and Laser Applications
- Space Exploration and Technology
- Natural Products and Biological Research
- Advanced Statistical Methods and Models
- Aquatic Ecosystems and Phytoplankton Dynamics
- Fish Ecology and Management Studies
- Freshwater macroinvertebrate diversity and ecology
- Spectroscopy and Chemometric Analyses
- Laser Design and Applications
- Atmospheric and Environmental Gas Dynamics
- Numerical Methods and Algorithms
University of Illinois Urbana-Champaign
2022-2024
Laboratoire d’Astrophysique de Marseille
2017-2024
Aix-Marseille Université
2019-2024
Centre National de la Recherche Scientifique
2019-2024
Max Planck Institute for Extraterrestrial Physics
2024
Château Gombert
2023
University of South Carolina
2015-2017
Scottish Environment Protection Agency
2016
University of Glasgow
2016
The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is first one for SDSS-V, fifth generation survey. SDSS-V comprises three primary scientific programs, or "Mappers": Milky Way Mapper (MWM), Black Hole (BHM), and Local Volume (LVM). This contains extensive targeting information two multi-object spectroscopy programs (MWM BHM), including input catalogs selection functions their numerous objectives. We describe production databases calibration- scientifically-focused...
WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for William Herschel Telescope, will see first light in late 2022. WEAVE comprises a 2-degree field-of-view prime-focus corrector system, nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and single large IFU. These systems feed dual-beam spectrograph covering wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges $R\sim20\,000$. After summarising...
Abstract Stars that formed with an initial mass of over 50 M ⊙ are very rare today, but they thought to be more common in the early Universe. The fates those early, metal-poor, massive stars highly uncertain. Most expected directly collapse black holes, while some may explode as a result rotationally powered engines or pair-creation instability. We present chemical abundances J0931+0038, nearby low-mass star identified follow-up SDSS-V Milky Way Mapper, which preserves signature unusual...
Abstract “Changing-look” active galactic nuclei (CL-AGNs) challenge our basic ideas about the physics of accretion flows and circumnuclear gas around supermassive black holes. Using first-year Sloan Digital Sky Survey V (SDSS-V) repeated spectroscopy nearly 29,000 previously known (AGNs), combined with dedicated follow-up spectroscopy, publicly available optical light curves, we have identified 116 CL-AGNs where (at least) one broad emission line has essentially (dis-)appeared, as well 88...
Aims. Compact white-dwarf binaries are selected from spectra obtained in the early SDSS-V plate program. A dedicated set of SDSS observations were carried out eFEDS field, providing spectroscopic classifications for a significant fraction optically bright end (r < 22.5) X-ray sample. The identification and subclassification rests on visual inspections spectra, spectral variability, color-magnitude color-color diagrams involving optical fluxes, variability literature work. Results. Upon...
Abstract Measuring the mass–radius relation of individual white dwarfs is an empirically challenging task that has been performed for only a few dozen stars. We measure dwarf using gravitational redshifts and radii 135 in wide binaries with main-sequence companions. obtain radial velocities these systems companion, subtract Doppler from dwarfs’ apparent motions, isolating their redshifts. use Gaia data to calculate surface temperatures dwarfs, thereby deriving empirical redshift–radius...
ABSTRACT SDSS-V is carrying out a dedicated survey for white dwarfs, single, and in binaries, we report the analysis of spectroscopy 118 cataclysmic variables (CVs) CV candidates obtained during final plug plate observations SDSS. We identify eight new CVs, spectroscopically confirm 53 refute 11 published candidates, 21 or improved orbital periods. The period distribution CVs does not clearly exhibit gap. In common with previous studies, shows that identified have larger proportion...
ABSTRACT The upcoming WEAVE-QSO survey will target a high density of quasars over large area, enabling the reconstruction 3D field through Lyman-α (Ly-α) tomography unprecedented volumes smoothed on intermediate cosmological scales (≈ 16 Mpc h−1). We produce mocks Ly-α forest using Mass Association Scheme, and reconstruct between sightlines Wiener filtering in configuration compatible with future observations. fidelity is assessed by measuring one- two-point statistics from distribution...
The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is first one for SDSS-V, fifth generation survey. SDSS-V comprises three primary scientific programs, or "Mappers": Milky Way Mapper (MWM), Black Hole (BHM), and Local Volume (LVM). This contains extensive targeting information two multi-object spectroscopy programs (MWM BHM), including input catalogs selection functions their numerous objectives. We describe production databases calibration- scientifically-focused...
In this series of papers, we employ several machine learning (ML) methods to classify the point-like sources from miniJPAS catalogue, and identify quasar candidates. Since no representative sample spectroscopically confirmed exists at present train these ML algorithms, rely on mock catalogues. first paper develop a pipeline compute synthetic photometry quasars, galaxies stars using spectra objects targeted as quasars in Sloan Digital Sky Survey. To match same depths signal-to-noise ratio...
Abstract We report the discovery of SDSS J022932.28+713002.7, a nascent extremely low-mass (ELM) white dwarf (WD) orbiting massive (>1 M ⊙ at 2 σ confidence) companion with period 36 hr. use combination spectroscopy, including data from ongoing fifth-generation Sloan Digital Sky Survey (SDSS-V), and photometry to measure stellar parameters primary pre-ELM WD. The lightcurve WD exhibits ellipsoidal variation, which we combine radial velocity PHOEBE binary simulations estimate mass...
ABSTRACT We study of the properties a new class circumgalactic medium absorbers identified in Ly α forest: ‘Strong, Blended Lyman-α’ (or SBLA) absorption systems. SBLAs at 2.4 &lt; z 3.1 SDSS-IV/eBOSS spectra by their strong extended complexes covering 138 $\, \, {\rm km}\, s}^{-1}$ with an integrated $\log (N_{\rm H\, {\small I}}/\mathrm{cm}^{-2}) =16.04$$\substack{+0.05 \\ -0.06}$ and Doppler parameter b = 18.1$\substack{+0.7 -0.4}$$\, s}^{-1}$. Clustering forest provides large-scale...
We present a high-cadence multi-epoch analysis of dramatic variability three broad emission lines (MgII, H$\beta$, and H$\alpha$) in the spectra luminous quasar ($\lambda L_{\lambda}$(5100\r{A}) = $4.7 \times 10^{44}$ erg s$^{-1}$) SDSS J141041.25+531849.0 at $z 0.359$ with 127 spectroscopic epochs over 9 years monitoring (2013-2022). observe anti-correlations between emission-line widths flux all lines, indicating that "breathe" response to stochastic continuum variations. also radial...
We present the first clustering measurement of Strong Blended Lyman $\alpha$ (SBLA) absorption systems by measuring their cross-correlation with forest. SBLAs are a new population absorbers detected within find bias $2.329\pm0.057$, consistent that Damped (DLAs). For DLAs, we recover $2.331\pm0.057$ larger than previously reported (P\'erez-R\`afols et al. 2018b). also redshift space distortion parameter $\beta=0.417\pm0.010$, recovered value for DLAs ($\beta=0.416\pm0.010$). This is SBLA and...
We report Keck/Echellette Spectrograph and Imager Very Large Telescope/Ultraviolet-Visual Echelle observations of three super-damped Lyα quasar absorbers with H i column densities log NH ≥ 21.7 at redshifts 2 ≲ z 2.5. All show similar metallicities (∼−1.3 to −1.5 dex), dust depletion Fe, Ni, Mn. Two the supersolar [S/Zn] [Si/Zn]. combine our results those for other damped a (DLAs) examine trends between i, metallicity, depletion. A larger fraction super-DLAs lie close or above line [X/H] =...
WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for William Herschel Telescope, will see first light in late 2022. WEAVE comprises a 2-degree field-of-view prime-focus corrector system, nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and single large IFU. These systems feed dual-beam spectrograph covering wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges $R\sim20\,000$. After summarising...
This paper is part of large effort within the J-PAS collaboration that aims to classify point-like sources in miniJPAS, which were observed 60 optical bands over ~1 deg 2 AEGIS field. We developed two algorithms based on artificial neural networks (ANN) objects into four categories: stars, galaxies, quasars at low redshift ( z < 2.1), and high ≥ 2.1). As inputs, we used miniJPAS fluxes for one classifiers (ANN 1 ) colours other ). The ANNs trained tested using mock data first place....
We present abundance measurements of elements O, C, Si and Fe for three gas-rich galaxies at z~5 using observations from the Very Large Telescope (VLT) Keck telescope in order to better constrain early chemical enrichment galaxies. These show strong Lyman-{\alpha} absorption spectra background quasars, with neutral hydrogen column densities log N${_H{}_I}$(cm$^{-2}$)=20.10$\pm$0.15, 20.10$\pm$0.15, 20.80$\pm$0.15. Using undepleted element we find metallicities [O/H] be range -2.51 -2.05 dex....
Astrophysical surveys rely heavily on the classification of sources as stars, galaxies or quasars from multi-band photometry. Surveys in narrow-band filters allow for greater discriminatory power, but variety different types and redshifts objects present a challenge to standard template-based methods. In this work, which is part larger effort that aims at building catalogue miniJPAS survey, we Machine Learning-based method employs Convolutional Neural Networks (CNNs) classify point-like...
We present the results of an investigation a highly variable CIV broad absorption-line feature in quasar SBS 1408+544 (z=2.337) that shows significant shift velocity over time. This source was observed as part Sloan Digital Sky Survey Reverberation Mapping Project and SDSS-V Black Hole Mapper Project, has been included two previous studies, both which identified variability high-velocity absorption line (BAL) on timescales just few days rest frame. Using ~130 spectra acquired eight years...
We present SQUEzE, a software package to classify quasar spectra and estimate their redshifts. SQUEzE is random forest classifier operating on the parameters of candidate emission peaks identified in spectra. test performance algorithm using visually inspected data from BOSS as truth table. Only 4\% sample ($\sim$6,800 quasars $\sim$11,520 contaminants) needed for converged training recommended choices confidence threshold ($0.2<p_{\rm min}<0.7$). For an operational mode which balances...
Element abundances in high-redshift quasar absorbers offer excellent probes of the chemical enrichment distant galaxies, and can constrain models for population III early II stars. Recent observations indicate that sub-damped Lyman-alpha (sub-DLA) are more metal-rich than DLA at redshifts 0$<$$z$$<$3. It has also been suggested metallicity drops suddenly $z$$>$4.7. However, only 3 DLAs $z$$>$4.5 none $z$$>$3.5 have "dust-free" measurements undepleted elements. We report first sub-DLA...
We present an analysis combining the simultaneous measurement of intergalactic absorption by hydrogen (H I), helium (He II) and oxygen (O VI) in UV optical quasar spectra. The combination H I He II Lyman-alpha forests through $\eta$ (the ratio column densities singly ionized to neutral hydrogen) is thought be sensitive large-scale inhomogeneities extragalactic background. test this assertion measuring associated five-times-ionized absorption, which also apply pixel depth technique O VI high...
We present the first clustering measurement of Strong Blended Lyman $α$ (SBLA) absorption systems by measuring their cross-correlation with forest. SBLAs are a new population absorbers detected within find bias $2.329\pm0.057$, consistent that Damped (DLAs). For DLAs, we recover $2.331\pm0.057$ larger than previously reported (Pérez-Ràfols et al. 2018b). also redshift space distortion parameter $β=0.417\pm0.010$, recovered value for DLAs ($β=0.416\pm0.010$). This is SBLA and DLA tracing...