Physics Commons^™

Mapping Gravitational-Wave Backgrounds Of Arbitrary Polarisation Using Pulsar Timing Arrays, Jonathan Gair, Joseph D. Romano, Stephen R. Taylor

Physics and Astronomy Faculty Publications and Presentations

We extend our previous work on mapping gravitational-wave backgrounds using techniques borrowed from the analysis of cosmic microwave background data to backgrounds which have non-general-relativity (non-GR) polarisations. Our analysis and results are presented in the context of pulsar timing array observations, but the overarching methods are general, and can be easily applied to LIGO or eLISA observations using appropriately modified response functions. Analytic expressions for the pulsar timing response to gravitational waves with non-GR polarisation are given for each mode of a spin-weighted spherical-harmonic decomposition of the background, which permit the signal to be mapped across the sky to any …

A Deep Look At The Nuclear Region Of Ugc 5101 Through High Angular Resolution Mid-Ir Data With Gtc/Canaricam, M. Martínez-Paredes, Almudena Alonso-Herrero, Itziar Aretxaga, C. Ramos Almeida, A. Hernán-Caballero, O. González-Martín, M. Pereira-Santaella, Christopher Packham, A. Asensio Ramos, T. Díaz-Santos, Moshe Elitzur, P. Esquej, I. García-Bernete, Masatoshi Imanishi, Nancy A. Levenson, José Miguel Rodríguez Espinosa

Physics and Astronomy Faculty Publications

We present an analysis of the nuclear infrared (IR, 1.6–18 μm) emission of the ultraluminous IR galaxy UGC 5101 to derive the properties of its active galactic nucleus (AGN) and its obscuring material. We use new mid-IR high angular resolution (0.3–0.5 arcsec) imaging using the Si-2 filter (λ_C = 8.7 μm) and 7.5–13 μm spectroscopy taken with CanariCam (CC) on the 10.4 m Gran Telescopio CANARIAS. We also use archival Hubble Space Telescope/NICMOS and Subaru/COMICS imaging and Spitzer/IRS spectroscopy. We estimate the near- and mid-IR unresolved nuclear emission by modelling the imaging data with GALFIT. We decompose …

Strong Variability Of The Coronal Line Region In Ngc 5548, Hermine Landt, Martin J. Ward, Katrien C. Steenbrugge, Gary J. Ferland

Physics and Astronomy Faculty Publications

We present the second extensive study of the coronal line variability in an active galaxy. Our data set for the well-studied Seyfert galaxy NGC 5548 consists of five epochs of quasi-simultaneous optical and near-infrared spectroscopy spanning a period of about five years and three epochs of X-ray spectroscopy overlapping in time with it. Whereas the broad emission lines and hot dust emission varied only moderately, the coronal lines varied strongly. However, the observed high variability is mainly due to a flux decrease. Using the optical [Fe vii] and X-ray O vii emission lines we estimate that the coronal line gas …

Sdss-Iv/Manga: Spectrophotometric Calibration Technique, Renbin Yan, Christy Tremonti, Matthew A. Bershady, David R. Law, David J. Schlegel, Kevin Bundy, Niv Drory, Nicholas Macdonald, Dmitry Bizyaev, Guillermo A. Blanc, Michael R. Blanton, Brian Cherinka, Arthur Eigenbrot, James E. Gunn, Paul Harding, David W. Hogg, José R. Sánchez-Gallego, Sebastian F. Sánchez, David A. Wake, Anne-Marie Weijmans, Ting Xiao, Kai Zhang

Physics and Astronomy Faculty Publications

Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), one of three core programs in the Sloan Digital Sky Survey-IV, is an integral-field spectroscopic survey of roughly 10,000 nearby galaxies. It employs dithered observations using 17 hexagonal bundles of 2'' fibers to obtain resolved spectroscopy over a wide wavelength range of 3600–10300 Å. To map the internal variations within each galaxy, we need to perform accurate spectral surface photometry, which is to calibrate the specific intensity at every spatial location sampled by each individual aperture element of the integral field unit. The calibration must correct only for the flux loss due …

Di-Hadron Correlations With Identified Leading Hadrons In 200 Gev Au + Au And D + Au Collisions At Star, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev, X. Bai

Physics and Astronomy Faculty Publications

The STAR Collaborationpresents for the first time two-dimensional di-hadron correlations with identified leading hadrons in 200 GeV central Au+Au and minimum-bias d+Au collisions to explore hadronization mechanisms in the quark gluon plasma. The enhancement of the jet-like yield for leading pions in Au + Au data with respect to the d + Au reference and the absence of such an enhancement for leading non-pions (protons and kaons) are discussed within the context of a quark recombination scenario. The correlated yield at large angles, specifically in the ridge region, is found to be significantly higher for leading non-pions than pions. …

On Calculating The Current-Voltage Characteristic Of Multi-Diode Models For Organic Solar Cells, Ken Roberts, Sree Ram Valluri

Physics and Astronomy Publications

We provide an alternative formulation of the exact calculation of the current-voltage characteristic of solar cells which have been modeled with a lumped parameters equivalent circuit with one or two diodes. Such models, for instance, are suitable for describing organic solar cells whose current-voltage characteristic curve has an inflection point, also known as an S-shaped anomaly. Our formulation avoids the risk of numerical overflow in the calculation. It is suitable for implementation in Fortran, C or on micro-controllers.

Supermassive Black Hole Seed Formation At High Redshifts: Long-Term Evolution Of The Direct Collapse, Isaac Shlosman, Jun-Hwan Choi, Mitchell C. Begelman, Kentaro Nagamine

Physics and Astronomy Faculty Publications

We use cosmological adaptive mesh refinement code enzo zoom-in simulations to study the long-term evolution of the collapsing gas within dark matter haloes at z. This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds. To circumvent the Courant condition at small radii, we apply the sink particle method, focusing on evolution on scales ∼0.01–10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. …

From JEff=1/2 Insulator To P-Wave Superconductor In Single-Crystal Sr2Ir1−XRuXO4 (0≤X≤1), Shujuan Yuan, Saicharan Aswartham, Jsaminka Terzic, H. Zheng, H. D. Zhao, P. Schlottmann, Gang Cao

Physics and Astronomy Faculty Publications

Sr₂IrO₄ is a magnetic insulator assisted by strong spin-orbit coupling (SOC) whereas Sr₂RuO₄ is a p-wave superconductor. The contrasting ground states have been shown to result from the critical role of the strong SOC in the iridate. Our investigation of structural, transport, and magnetic properties reveals that substituting 4dRu⁴⁺(4d⁴) ions for 5dIr⁴⁺(5d⁵) ions in Sr₂IrO₄ directly adds holes to the t_2g bands, reduces the SOC, and thus rebalances the competing energies in single-crystal Sr …

Observation Of Transverse Spin-Dependent Azimuthal Correlations Of Charged Pion Pairs In P↑+P At √S=200  Gev, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev

Physics and Astronomy Faculty Publications

We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in p^↑+p collisions at RHIC. These correlations directly probe quark transversity distributions. We measure signals in excess of 5 standard deviations at high transverse momenta, at high pseudorapidities η>0.5, and for pair masses around the mass of the ρ meson. This is the first direct transversity measurement in p+p collisions.

Relative Proper Motions In The Rho Ophiuchi Cluster, Bruce Wilking, Frederick Vrba, Timothy Sullivan

Physics Faculty Works

Near-infrared images optimized for astrometry have been obtained for four fields in the high-density L 1688 cloud core over a 12 year period. The targeted regions include deeply embedded young stellar objects (YSOs) and very low luminosity objects too faint and/or heavily veiled for spectroscopy. Relative proper motions in R.A. and decl. were computed for 111 sources and again for a subset of 65 YSOs, resulting in a mean proper motion of (0,0) for each field. Assuming each field has the same mean proper motion, YSOs in the four fields were combined to yield estimates of the velocity dispersions in …

An Organic Mixed Ion-Electron Conductor For Power Electronics, Abdellah Malti, Jesper Edberg, Hjalmar Granberg, Zia Ullah Khan, Jens W. Andreasen, Xianjie Liu, Dan Zhao, Hao Zhang, Yulong Yao, Joseph W. Brill, Isak Engquist, Mats Fahlman, Lars Wågberg, Xavier Crispin, Magnus Berggren

Physics and Astronomy Faculty Publications

A mixed ionic–electronic conductor based on nanofibrillated cellulose composited with poly(3,4-ethylene-dioxythio­phene):­poly(styrene-sulfonate) along with high boiling point solvents is demonstrated in bulky electrochemical devices. The high electronic and ionic conductivities of the resulting nanopaper are exploited in devices which exhibit record values for the charge storage capacitance (1F) in supercapacitors and transconductance (1S) in electrochemical transistors.

Solar Modulation Of The Cosmic Ray Intensity And The Measurement Of The Cerenkov Reemission In Nova’S Liquid Scintillator, Philip James Mason

Doctoral Dissertations

The NOνA (NuMI Off-axis electron neutrino Appearance) experiment is a long baseline neutrino oscillation experiment at Fermi National Accelerator Laboratory. Its purpose is to observe the oscillation of ν_μ (muon neutrino) to ν_e (electron neutrino) and to investigate the neutrino mass hierarchy and CP violation in the neutrino sector. Two detectors have been built for this purpose, a Near Detector 300 feet underground at Fermilab, and a Far Detector, on the surface at Ash River, Minnesota.

The completion of NOνA’s Far Detector in October 2014 enabled not only the recent measurement of neutrino oscillations, but an array of …

Electronic Structure And Insulating Gap In Epitaxial Vo2 Polymorphs, Shinbuhm Lee, Tricia L. Meyer, Changhee Sohn, Donghwa Lee, John Nichols, Dongkyu Lee, Sung S. Ambrose Seo, John W. Freeland, Tae Won Noh, Ho Nyung Lee

Physics and Astronomy Faculty Publications

Determining the origin of the insulating gap in the monoclinic VO₂(M1) is a long-standing issue. The difficulty of this study arises from the simultaneous occurrence of structural and electronic transitions upon thermal cycling. Here, we compare the electronic structure of the M1 phase with that of single crystalline insulating VO₂(A) and VO₂(B) thin films to better understand the insulating phase of VO₂. As these A and B phases do not undergo a structural transition upon thermal cycling, we comparatively study the origin of the gap opening in the insulating VO₂ phases. …

Evidence For Photoionization-Driven Broad Absorption Line Variability, Tinggui Wang, Chenwei Yang, Huiyuan Wang, Gary J. Ferland

Physics and Astronomy Faculty Publications

We present a qualitative analysis of the variability of quasar broad absorption lines using the large multi-epoch spectroscopic data set of the Sloan Digital Sky Survey Data Release 10. We confirm that variations of absorption lines are highly coordinated among different components of the same ion or the same absorption component of different ions for C ɪᴠ, Si ɪᴠ, and N ᴠ. Furthermore, we show that the equivalent widths (EWs) of the lines decrease or increase statistically when the continuum brightens or dims. This is further supported by the synchronized variations of emission and absorption-line EWs when the well-established intrinsic …

The Inferred Evolution Of The Cold Gas Properties Of Candels Galaxies At 0.5 < Z < 3.0, G. Popping, K. Caputi, S. C. Trager, Rachel S. Somerville, Avishai Dekel, Susan A. Kassin, Dale D. Kocevski, Anton M. Koekemoer, Sandra M. Faber, Henry C. Ferguson, A. Galametz, Norman A. Grogin, Yicheng Guo, Y. Lu, Arjen Van Der Wel, Benjamin J. Weiner

Physics and Astronomy Faculty Publications

We derive the total cold gas, atomic hydrogen, and molecular gas masses of approximately 24 000 galaxies covering four decades in stellar mass at redshifts 0.5 < z < 3.0, taken from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey survey. Our inferences are based on the inversion of a molecular hydrogen based star formation law, coupled with a prescription to separate atomic and molecular gas. We find that: (1) there is an increasing trend between the inferred cold gas (H i and H₂), H i, and H₂ mass and the stellar mass of galaxies down to stellar masses of 10⁸ M_⊙ already in place at z = 3; (2) the molecular fractions of cold gas increase with increasing stellar mass and look-back time; (3) there is hardly any evolution in the mean H i content of galaxies at fixed stellar mass; (4) the cold gas fraction and relative amount of molecular …

Decoupling Of The Antiferromagnetic And Insulating States In Tb-Doped Sr2Iro4, J. C. Wang, Saicharan Aswartham, Feng Ye, Jsaminka Terzic, H. Zheng, Daniel Haskel, Shalinee Chikara, Yong Choi, P. Schlottmann, Radu Custelcean, Shujuan Yuan, Gang Cao

Physics and Astronomy Faculty Publications

Sr₂IrO₄ is a spin-orbit-coupled insulator with an antiferromagnetic (AFM) transition at T_N=240K. We report results of a comprehensive study of single-crystal Sr₂Ir_1−xTb_xO₄(0≤x≤0.03). This study found that a mere 3% (x=0.03) of tetravalent Tb⁴⁺(4f⁷) substituting for Ir⁴⁺ (rather than Sr²⁺) completely suppresses the long-range collinear AFM transition but retains the insulating state, leading to a phase diagram featuring a decoupling of the magnetic interactions and charge gap. The insulating state at x=0.03 is characterized by …

Construction Of A 408 Nm Laser System For Use In Ion Interferometry, Lawrence Archibald

Theses and Dissertations

This work reports on the construction of a 408 nm laser system designed to drive stimulated Raman transitions between the F = 4 and F = 5 2 S 1/2 states of 87 Sr + using the 2 P 3/2 state as the intermediate state. This laser system will be used as part of a 87 Sr + ion interferometer. This work also includes a discussion of relevant theory describing the interaction of the ions and laser, along with a calculation of the transition rates as a function of laser power and detuning.

Scalable Synthesis And Energy Applications Of Defect Engineered Nano Materials, Mehmet Karakaya

All Dissertations

Nanomaterials and nanotechnologies have attracted a great deal of attention in a few decades due to their novel physical properties such as, high aspect ratio, surface morphology, impurities, etc. which lead to unique chemical, optical and electronic properties. The awareness of importance of nanomaterials has motivated researchers to develop nanomaterial growth techniques to further control nanostructures properties such as, size, surface morphology, etc. that may alter their fundamental behavior. Carbon nanotubes (CNTs) are one of the most promising materials with their rigidity, strength, elasticity and electric conductivity for future applications. Despite their excellent properties explored by the abundant research works, …

Dark Matter Halo Concentration And The Evolution Of Spiral Structure In N-Body, Barred Spiral Galaxies, Jazmin Esmeralda Berlanga Medina

Graduate Theses and Dissertations

Motivated by the evidence of relationships between pitch angle (the tightness of spiral arm structure in the disk), P, and various indicators of central mass concentration, as well as the theoretical relationship between halo mass concentration and the density of visible matter in the central part of the galaxy, we look at a possible relationship between P and cvir (the virial concentration of the dark matter halo) in N-body simulations of barred, spiral galaxies. We also look at the evolution of pitch angle over time in higher temporal resolution than any data currently available in the literature. We find that …

Ultraviolet Emission Lines Of Si Ii In Cool Star And Solar Spectra, Sibasish Laha, Francis P. Keenan, Gary J. Ferland, Catherine A. Ramsbottom, Kanti M. Aggarwal, Thomas R. Ayres, Marios Chatzikos, Peter A. M. Van Hoof, Robin J. R. Williams

Physics and Astronomy Faculty Publications

Recent atomic physics calculations for Si ii are employed within the cloudy modelling code to analyse Hubble Space Telescope (HST) STIS ultraviolet spectra of three cool stars, β Geminorum, α Centauri A and B, as well as previously published HST/GHRS observations of α Tau, plus solar quiet Sun data from the High Resolution Telescope and Spectrograph. Discrepancies found previously between theory and observation for line intensity ratios involving the 3s²3p ²P_J–3s3p^{2 4}P_J' intercombination multiplet of Si II at ∼ 2335 Å are significantly reduced, as are those for …

Azimuthal Anisotropy In U+U And Au+Au Collisions At Rhic, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev

Physics and Astronomy Faculty Publications

Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, v₂{2} and v₂{4}, for charged hadrons from U+U collisions at √^s_NN=193  GeV and Au+Au collisions at √^s_NN=200  GeV. Nearly fully overlapping collisions are selected based on the energy deposited by spectators in zero degree calorimeters (ZDCs). Within this sample, the observed dependence of v₂{2} on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations …

Collisional Excitation Of [C Ii], [O I] And Co In Massive Galaxies, R. E. A. Canning, Gary J. Ferland, A. C. Fabian, R. M. Johnstone, P. A. M. Van Hoof, R. L. Porter, N. Werner, R. J. R. Williams

Physics and Astronomy Faculty Publications

Many massive galaxies at the centres of relaxed galaxy clusters and groups have vast reservoirs of warm (∼10 000 K) and cold (≲100 K) gas. In many such low-redshift systems this gas is lifted into the hot interstellar medium in filamentary structures, which are long lived and are typically not forming stars. Two important questions are how far do these reservoirs cool and if cold gas is abundant what is the cause of the low star formation efficiency? Heating and excitation of the filaments from collisions and mixing of hot particles in the surrounding X-ray gas describes well the optical …

The Young Radio Lobe Of 3c 84: Inferred Gas Properties In The Central 10 Pc, Yutaka Fujita, Nozomu Kawakatu, Isaac Shlosman, Hirotaka Ito

Physics and Astronomy Faculty Publications

We analyse the environment of the supermassive black hole (SMBH) in the centre of a massive elliptical galaxy NGC 1275 in the Perseus cluster, hosting the radio source 3C 84. We focus on the young radio lobe observed inside the estimated Bondi accretion radius, and discusss the momentum balance between the jet associated with the lobe and the surrounding gas. The results are compared with the proper motion of the radio lobe obtained with the very long baseline interferometry. We find that under assumption of a high-density environment ( ≳ 100 cm⁻³), the jet power must be comparable …

A Determination Of The Gamma-Ray Flux And Photon Spectral Index Distributions Of Blazars From The Fermi-Lat 3lac, Jack Singal

Physics Faculty Publications

We present a determination of the distributions of gamma-ray photon flux – the so-called LogN–LogS relation – and photon spectral index for blazars, based on the third extragalactic source catalogue of the Fermi Gamma-ray Space Telescope's Large Area Telescope, and considering the photon energy range from 100 MeV to 100 GeV. The data set consists of the 774 blazars in the so-called Clean sample detected with a greater than approximately 7σ detection threshold and located above ±20° Galactic latitude. We use non-parametric methods verified in previous works to reconstruct the intrinsic distributions from the observed ones …

Structure Symmetry Determination And Magnetic Evolution In Sr2Ir1−XRhXO4, Feng Ye, Xiaoping Wang, Christina Hoffmann, Jinchen Wang, Songxue Chi, Masaaki Matsuda, Bryan C. Chakoumakos, Jaime A. Fernandez-Baca, Gang Cao

Physics and Astronomy Faculty Publications

We use single-crystal neutron diffraction to determine the crystal structure symmetry and the magnetic evolution in the rhodium-doped iridates Sr₂Ir_1−xRh_xO₄ (0≤ x ≤ 0.16). Throughout this doping range, the crystal structure retains a tetragonal symmetry (space group I4₁/a) with two distinct magnetic Ir sites in the unit cell forming staggered IrO₆ rotation. Upon Rh doping, the magnetic order is suppressed and the magnetic moment of Ir⁴⁺ is reduced from 0.21μ_B/Ir for x=0 to 0.18μ_B/Ir for x=0.12. The magnetic structure …

Energy Dependence Of Acceptance-Corrected Dielectron Excess Mass Spectrum At Mid-Rapidity In Au + Au Collisions At √SNn = 19.6 And 200 Gev, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev

Physics and Astronomy Faculty Publications

The acceptance-corrected dielectron excess mass spectra, where the known hadronic sources have been subtracted from the inclusive dielectron mass spectra, are reported for the first time at mid-rapidity ∣y_ee∣+ Au collisions at √^sNN = 19.6 and 200 GeV. The excess mass spectra are consistently described by a model calculation with a broadened ρ spectral function for M_ee < 1.1 GeV/c². The integrated dielectron excess yield at √^sNN = 19.6 GeV for 0.4 < M_ee < 0.75 GeV/c², normalized to the charged particle multiplicity at mid-rapidity, has a value similar to that in ln+ln collisions at …

Candels Visual Classifications: Scheme, Data Release, And First Results, Jeyhan S. Kartaltepe, Mark Mozena, Dale D. Kocevski, Daniel H. Mcintosh, Jennifer Lotz, Eric F. Bell, Sandra M. Faber, Harry C. Ferguson, David C. Koo, Robert Bassett, Maksym Bernyk, Kirsten Blancato, Frederic Bournaud, Paolo Cassata, M. Castellano, Edmond Cheung, Christopher J. Conselice, D. Croton, Tomas Dahlen, Duilia F. De Mello, Laura Degroot, Jennifer Donley, Javiera Guedes, Norman A. Grogin, Nimish Hathi, Matt Hilton, Brett Hollon, Anton M. Koekemoer, Nick Liu, Ray A. Lucas

Physics and Astronomy Faculty Publications

We have undertaken an ambitious program to visually classify all galaxies in the five CANDELS fields down to H < 24.5 involving the dedicated efforts of over 65 individual classifiers. Once completed, we expect to have detailed morphological classifications for over 50,000 galaxies spanning 0 < z < 4 over all the fields, with classifications from 3 to 5 independent classifiers for each galaxy. Here, we present our detailed visual classification scheme, which was designed to cover a wide range of CANDELS science goals. This scheme includes the basic Hubble sequence types, but also includes a detailed look at mergers and interactions, the clumpiness of galaxies, k-corrections, and a variety of other structural properties. In this paper, we focus on the first field to be completed—GOODS-S, which has been classified at various depths. The wide area coverage spanning the full field (wide+deep+ERS) includes 7634 galaxies that have been classified by at least three different people. In the deep area of the field, 2534 galaxies have been classified by at least five different people at three different depths. With this paper, we release to the public …

Revisiting Scalar Glueballs, Hai-Yang Cheng, Chun-Khiang Chua, Keh-Fei Liu

Physics and Astronomy Faculty Publications

It is commonly believed that the lowest-lying scalar glueball lies somewhere in the isosinglet scalar mesons f₀(1370), f₀(1500) and f₀(1710) denoted generically by f₀. In this work we consider lattice calculations and experimental data to infer the glue and qq components of f₀. These include the calculations of the scalar glueball masses in quenched and unquenched lattice QCD, measurements of the radiative decays J/ψ→γf₀, the ratio of f₀ decays to ππ, KK and ηη, the ratio of J/ψ decays …

A Catalog Of Visual-Like Morphologies In The 5 Candels Fields Using Deep Learning, M. Huertas-Company, R. Gravet, G. Cabrera-Vives, Pablo G. Pérez-González, J. Kartaltepe, Guillermo Barro, M. Bernardi, S. Mei, F. Shankar, P. Dimauro, E. F. Bell, Dale D. Kocevski, David C. Koo, Sandra M. Faber, Daniel H. Mcintosh

Physics and Astronomy Faculty Publications

We present a catalog of visual-like H-band morphologies of ~50.000 galaxies (H_f160w < 24.5) in the 5 CANDELS fields (GOODS-N, GOODS-S, UDS, EGS, and COSMOS). Morphologies are estimated using Convolutional Neural Networks (ConvNets). The median redshift of the sample is 〈z〉 ~ 1.25. The algorithm is trained on GOODS-S, for which visual classifications are publicly available, and then applied to the other 4 fields. Following the CANDELS main morphology classification scheme, our model retrieves for each galaxy the probabilities of having a spheroid or a disk, presenting an irregularity, being compact or a point source, and being unclassifiable. ConvNets are able to predict the fractions of votes given to a galaxy image with zero bias and ~10% scatter. The fraction of mis-classifications is …

On The Disk Wind Mass Loss Rates In Qsos, Nicolas A. Pereyra

Physics and Astronomy Faculty Publications and Presentations

We derive here a relatively simple expression for the total wind mass loss rates in QSOs within the accretion disk wind scenario. We show that the simple expression derived here for QSO disk wind mass loss rate is in a very good agreement with the more “exact” values obtained through significantly more complex and detailed numerically intensive 2.5D time-dependent simulations. Additionally we show that for typical QSO parameters, the disk itself will be emitting mostly in the UV/optical spectrum, in turn implying that the X-ray emission from QSOs likely is produced through some physical mechanism acting at radii smaller than …