D. M. Alexander
A5082749953- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Radio Astronomy Observations and Technology
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- Posttraumatic Stress Disorder Research
- Pulsars and Gravitational Waves Research
- Geomagnetism and Paleomagnetism Studies
- Particle Detector Development and Performance
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Disaster Response and Management
- Grief, Bereavement, and Mental Health
- Dark Matter and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Migration, Health and Trauma
Durham University
2016-2025
Indiana Cancer Consortium
2024-2025
Tech-X Corporation (United States)
2001-2024
Penn State Milton S. Hershey Medical Center
2024
United States Army Reserve
2024
United States Army Combat Capabilities Development Command
2024
DEVCOM Army Research Laboratory
2018-2024
Rice University
2006-2023
Muskegon Community College
2022-2023
East Cheshire NHS Trust
2023
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates band from 3 to 79 keV, extending sensitivity of far beyond ∼10 keV cutoff achieved by all previous satellites. inherently low background associated with concentrating light enables probe hard sky a more than 100-fold improvement over collimated or coded mask instruments that have operated this bandpass. Using its unprecedented...
The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution, over approximate redshift (z) range 8--1.5. It will image >250,000 distant galaxies using three separate cameras on Hubble Space Telescope, from mid-ultraviolet near-infrared, and find measure Type Ia supernovae at z>1.5 test their accuracy as standardizable candles for cosmology. Five premier multi-wavelength sky regions are selected, each with...
This special issue of the Astrophysical Journal Letters is dedicated to presenting initial results from Great Observatories Origins Deep Survey (GOODS) that are primarily, but not exclusively, based on multiband imaging data obtained with Hubble Space Telescope and Advanced Camera for Surveys (ACS). The survey covers roughly 320 arcmin2 in ACS F435W, F606W, F814W, F850LP bands, divided into two well-studied fields. Existing deep observations Chandra X-Ray Observatory ground-based facilities...
Aims.We study the relationship between local environment of galaxies and their star formation rate (SFR) in Great Observatories Origins Deep Survey, GOODS, at .
Examining a sample of massive galaxies at 1.4<z<2.5 with K_{Vega}<22 from the Great Observatories Origins Deep Survey, we compare photometry Spitzer mid- and far-IR, to submillimeter, radio rest-frame ultraviolet wavelengths, test agreement between different tracers star formation rates (SFRs) explore implications for galaxy assembly. For z~2 moderate luminosities(L_{8um}<10^{11}L_sun), find that SFR can be estimated consistently multiwavelength data based on local luminosity correlations....
This paper describes the Hubble Space Telescope imaging data products and reduction procedures for Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). survey is designed to document evolution of galaxies black holes at $z\sim1.5-8$, study Type Ia SNe beyond $z>1.5$. Five premier multi-wavelength sky regions are selected, each with extensive multiwavelength observations. The primary CANDELS consist obtained in Wide Field Camera 3 / infrared channel (WFC3/IR) UVIS channel,...
We present the deepest 100 to 500 μm far-infrared observations obtained with Herschel Space Observatory as part of GOODS-Herschel key program, and examine infrared (IR) 3–500 spectral energy distributions (SEDs) galaxies at 0 < z 2.5, supplemented by a local reference sample from IRAS, ISO, Spitzer, AKARI data. determine projected star formation densities their radio mid-IR continuum sizes.
We report here, for the first time, on spatial oscillations of coronal loops, which were detected in extreme-ultraviolet wavelengths (171 Å) with Transition Region and Coronal Explorer, temperature range Te ≈ 1.0-1.5 MK. The observed loop occurred during a flare that began at 1998 July 14, 12:55 UT are most prominent 20 minutes. oscillating loops connect penumbra leading sunspot to site trailing portion. identified five an average length L = 130,000 ± 30,000 km. transverse amplitude is A...
We present catalogs for the ~2 Ms Chandra Deep Field-North, currently deepest X-ray observation of Universe in 0.5-8.0 keV band. Five hundred and three (503) sources are detected over an ~448 sq.arcmin area up to seven bands; 20 these lie Hubble Field-North. Source positions determined using matched-filter centroiding techniques; median positional uncertainty is ~0.3 arcsecs. The colors indicate a broad variety source types, although absorbed AGNs (including some possible Compton-thick...
[abridged] We present point-source catalogs for the 4Ms Chandra Deep Field-South (CDF-S), which is deepest survey to date and covers an area of 464.5 arcmin^2. provide a main source catalog, contains 740 X-ray point sources that are detected with wavdetect at false-positive probability threshold 1E-5 also satisfy binomial-probability source-selection criterion P<0.004; this approach designed maximize number reliable detected. A total 300 main-catalog new compared previous 2Ms CDF-S sources....
Background The association between mental health and occupational factors among ambulance personnel has not been thoroughly investigated in the UK. Aims To identify prevalence of psychopathology its relationship to personality exposure critical incidents. Method Data were gathered from by means an anonymous questionnaire standardised measures. Results Approximately a third sample reported high levels general psychopathology, burnout posttraumatic symptoms. Burnout was associated with less...
We present partial-correlation analyses that examine the strengths of relationships between l2500 Å, l2 keV, αOX, and redshift for optically selected active galactic nuclei (AGNs). extend work Strateva coworkers, which analyzed AGNs from Sloan Digital Sky Survey (SDSS), by including 52 moderate-luminosity, COMBO-17 survey with corresponding deep (≈250 ks to 1 Ms) X-ray observations Extended Chandra Deep Field-South. The extends ∼3 mag deeper than SDSS probes moderate-luminosity numerically...
This White Paper, submitted to the recent ESA call for science themes define its future large missions, advocates need a transformational leap in our understanding of two key questions astrophysics: 1) How does ordinary matter assemble into scale structures that we see today? 2) do black holes grow and shape Universe? Hot gas clusters, groups intergalactic medium dominates baryonic content local Universe. To understand astrophysical processes responsible formation assembly these structures,...
We present X-ray source catalogs for the $\approx7$ Ms exposure of Chandra Deep Field-South (CDF-S), which covers a total area 484.2 arcmin$^2$. Utilizing WAVDETECT initial detection and ACIS Extract photometric extraction significance assessment, we create main catalog containing 1008 sources that are detected in up to three bands: 0.5-7.0 keV, 0.5-2.0 2-7 keV. A supplementary is also provided including 47 lower-significance have bright ($K_s\le23$) near-infrared counterparts. identify...
We present integral field unit (IFU) observations covering the [O III]4959,5007 and H-Beta emission lines of sixteen z<0.2 type 2 active galactic nuclei (AGN). Our targets are selected from a well-constrained parent sample 24,000 AGN so that we can place our into context overall population. radio-quiet with star formation rates (<~[10-100] Msol/yr) consistent normal star-forming galaxies. decouple kinematics galaxy dynamics mergers outflows. find high-velocity ionised gas (velocity widths...
The COSMOS-Legacy survey is a 4.6 Ms Chandra program that has imaged 2.2 deg$^2$ of the COSMOS field with an effective exposure $\simeq$160 ks over central 1.5 and $\simeq$80 in remaining area. combination 56 new observations, obtained as X-ray Visionary Project, previous C-COSMOS survey. We describe reduction analysis observations properties 2273 point sources detected above spurious probability 2$\times 10^{-5}$. also present updated data. whole includes 4016 (3814, 2920 2440 full, soft...
We present the maps, source catalogue and number counts of largest, most complete unbiased extragalactic submillimetre survey ever undertaken: 850-micron SCUBA HAlf Degree Extragalactic Survey (SHADES). Using Submillimetre Common-User Bolometer Array (SCUBA) on James Clerk Maxwell Telescope (JCMT), SHADES mapped two separate regions sky: Subaru/XMM-Newton Deep Field (SXDF) Lockman Hole East (LH). These maps cover 720 square arcmin with an RMS noise level about 2 mJy have uncovered >100...
Deep SCUBA surveys have uncovered a large population of massive submm galaxies (SMGs) at z>~1. Although it is generally believed that these host intense star-formation activity, there growing evidence substantial fraction also harbor an AGN. We present here possibly the strongest for this viewpoint to date: combination ultra-deep X-ray observations (the 2 Ms CDF-N) and deep Keck spectroscopic data. find majority (~75%) spectroscopically identified SMGs AGN activity; other ~25% properties...
Using HST/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), we examine role that major galaxy mergers play in triggering active galactic nuclei (AGN) activity at z~2. Our sample consists 72 moderate-luminosity (Lx ~ 1E42-1E44 erg/s) AGN 1.5<z<2.5 are selected using 4 Msec Chandra observations Field South, deepest X-ray to date. Employing visual classifications, have analyzed rest-frame optical morphologies host galaxies and compared...
Active galactic nuclei (AGN) are powered by the accretion of material onto a supermassive black hole (SMBH) and among most luminous objects in Universe. However, huge radiative power AGN cannot be seen directly, as is hidden behind gas dust that absorb many characteristic observational signatures. This obscuration presents an important challenge for uncovering complete population understanding cosmic evolution SMBHs. In this review, we describe broad range multiwavelength techniques...
We investigate the effect of active galactic nucleus (AGN) variability on observed connection between star formation and black hole accretion in extragalactic surveys. Recent studies have reported relatively weak correlations AGN luminosities properties hosts, which has been interpreted to imply that there is no direct activity formation. However, AGNs may be expected vary significantly a wide range timescales (from hours Myr) are far shorter than typical timescale for (≳100 Myr). This can...
We present a sensitive 870 micron survey of the Extended Chandra Deep Field South (ECDFS) using LABOCA on APEX telescope. The ECDFS Submillimetre Survey (LESS) covers full 30' x field size and has uniform noise level 1.2 mJy/beam. LESS is thus largest contiguous deep submillimetre undertaken to date. properties our map show clear evidence that we are beginning be affected by confusion noise. catalog 126 SMGs detected with significance above 3.7 sigma. exhibits deficit bright relative...
We present deep mid-infrared spectroscopy with the Spitzer Space Telescope of 13 submillimeter galaxies (SMGs) in Great Observatories Origins Deep Survey North (GOODS-N) field. find strong polycyclic aromatic hydrocarbon (PAH) emission all our targets which allows us to measure mid-IR spectroscopic redshifts and place constraints on contribution from star formation active galactic nuclei (AGN) activity emission. In high signal-to-noise ratio composite spectrum SMGs, we that hot dust...