R. C. Thomas
A5107343393- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Scientific Computing and Data Management
- Stellar, planetary, and galactic studies
- Neutrino Physics Research
- Astrophysical Phenomena and Observations
- Nuclear Physics and Applications
- Distributed and Parallel Computing Systems
- Computational Physics and Python Applications
- Advanced Data Storage Technologies
- Parallel Computing and Optimization Techniques
- Astro and Planetary Science
- Cloud Computing and Resource Management
- Algorithms and Data Compression
- Data Visualization and Analytics
- Geological and Geophysical Studies
- Astronomical Observations and Instrumentation
- Atmospheric Ozone and Climate
- Cosmology and Gravitation Theories
- Atomic and Subatomic Physics Research
- Big Data Technologies and Applications
- Cell Image Analysis Techniques
- Research Data Management Practices
Lawrence Berkeley National Laboratory
2014-2024
National Energy Research Scientific Computing Center
2017-2022
University of Utah
2022
University of Edinburgh
2022
MIT Lincoln Laboratory
2022
Microsoft (United States)
2022
Georgia Institute of Technology
2015
University of California, Berkeley
2015
Webster University
2004
We present photometric and spectroscopic observations of SN 2007if, an overluminous (MV = −20.4), red (B − V 0.16 at B-band maximum), slow-rising (trise 24 days) type Ia supernova (SN Ia) in a very faint (Mg −14.10) host galaxy. A spectrum 5 days past maximum light is direct match to the super-Chandrasekhar-mass candidate 2003fg, showing Si ii C ∼9000 km s−1. high signal-to-noise co-addition spectral time series reveals no Na i D absorption, suggesting negligible reddening galaxy, late-time...
As part of an on-going effort to identify, understand and correct for astrophysics biases in the standardization Type Ia supernovae (SNIa) cosmology, we have statistically classified a large sample nearby SNeIa into those located predominantly younger or older environments. This classification is based on specific star formation rate measured within projected distance 1kpc from each SN location (LsSFR). important refinement compared using local directly as it provides normalization relative...
We report Nearby Supernova Factory observations of SN 2005gj, the second confirmed case a "hybrid" Type Ia/IIn supernova. Our early-phase photometry 2005gj shows that interaction is much stronger than for prototype, 2002ic. first spectrum hot continuum with broad and narrow H-alpha emission. Later spectra, spanning over 4 months from outburst, show clear Ia features combined H-gamma, H-beta, HeI 5876,7065 in At higher resolution, P Cygni profiles are apparent. Surprisingly, we also observe...
The nearby supernova SN 2011fe can be observed in unprecedented detail. Therefore, it is an important test case for Type Ia (SN Ia) models, which may bring us closer to understanding the physical nature of these objects. Here, we explore how available and expected future observations used constrain explosion scenarios. We base our discussion on three-dimensional simulations a delayed detonation Chandrasekhar-mass white dwarf violent merger two dwarfs-realizations models appropriate most...
We present 32 epochs of optical (3300-9700 \AA) spectrophotometric observations the nearby quintessential "normal" type Ia supernova (SN Ia) SN 2011fe in galaxy M101, extending from -15 to +97 d with respect B-band maximum, obtained by Nearby Supernova Factory collaboration. is closest (\mu = 29.04) and brightest (Bmax 9.94 mag) observed since advent modern large scale programs for intensive periodic followup supernovae. Both synthetic light curve measurements spectral feature analysis...
We examine the relationship between Type Ia supernova (SN Ia) Hubble residuals and properties of their host galaxies using a sample 115 SNe from Nearby Supernova Factory. use galaxy stellar masses specific star formation rates fitted photometry for all hosts, as well gas-phase metallicities subset 69 star-forming (non-active galactic nucleus) to show that SN correlate with each these properties. With data we find new evidence correlation intrinsic color metallicity. When combine our those...
We present a sample of normal Type Ia supernovae (SNe Ia) from the Nearby Supernova Factory data set with spectrophotometry at sufficiently late phases to estimate ejected mass using bolometric light curve. measure 56Ni masses peak luminosity, then compare luminosity in 56Co-decay tail expected rate radioactive energy release ejecta given mass. infer Bayesian context semi-analytic model ejecta, incorporating constraints contemporary numerical models as priors on density structure and...
(Abridged) We study the host galaxy regions in close proximity to Type Ia supernovae (SNe Ia) analyze relations between properties of SN events and environments most similar where their progenitors formed. focus on local H\alpha\ emission as an indicator young environments. The Nearby Supernova Factory has obtained flux-calibrated spectral timeseries for SNe using integral field spectroscopy, allowing simultaneous measurement its immediate vicinity. For 89 we measure tracing ongoing star...
We employ 76 type Ia supernovae with optical spectrophotometry within 2.5 days of B-band maximum light obtained by the Nearby Supernova Factory to derive impact Si and Ca features on intrinsic luminosity determine a dust reddening law. use equivalent width II {\lambda}4131 in place curve stretch account for first-order variability. The resultant empirical spectral law exhibits strong associated {\lambda}6355. After applying correction based H&K we find consistent Cardelli extinction Using...
We present a new method to standardize type Ia supernova (SN Ia) luminosities 0.13 mag using flux ratios from single flux-calibrated spectrum per SN. Using Nearby Supernova Factory spectrophotomery of 58 SNe Ia, we performed an unbiased search for that correlate with SN luminosity. After developing the and selecting best training sample, verified results on separate validation sample data literature. identified multiple whose correlations luminosity are stronger than those light curve shape...
We present optical photometry and spectroscopy of five Type Ia supernovae discovered by the Nearby Supernova Factory selected to be spectroscopic analogs candidate super-Chandrasekhar-mass events SN 2003fg 2007if. Their spectra are characterized hot, highly ionized photospheres near maximum light, for which 1991T supplies best phase coverage among available close spectral templates. Like 2007if, these overluminous (−19.5 < MV −20) velocity Si ii λ6355 absorption minimum is consistent with...
Context. Our Local Group of galaxies appears to be moving relative the cosmic microwave background with source peculiar motion still uncertain. While in past this has been studied mostly using as distance indicators, weight type Ia supernovae (SNe Ia) increased recently continuously improving statistics available low-redshift supernovae. Aims. We measured bulk flow nearby universe ($0.015 < z 0.1$) 117 SNe observed by Nearby Supernova Factory, well Union2 compilation SN data already...
We present convincing evidence of unburned carbon at photospheric velocities in new observations 5 Type Ia supernovae (SNe Ia) obtained by the Nearby Supernova Factory. These SNe are identified examining 346 spectra from 124 before +2.5 d relative to maximum. Detections based on presence relatively strong C II 6580 absorption "notches" multiple each SN, aided automated fitting with SYNAPPS code. Four question otherwise spectroscopically unremarkable, ions and ejection typical Ia, but fifth...
Type Ia supernova cosmology depends on the ability to fit and standardize observations of magnitudes with an empirical model. We present here a series new models Supernova spectral time that capture greater amount diversity than possible are currently customary. These entitled SuperNova Empirical MOdels (\textsc{SNEMO}\footnote{https://snfactory.lbl.gov/snemo}). The constructed using spectrophotometric from $172$ individual supernovae Nearby Factory, comprising more $2000$ spectra. Using...
We present the results of applying new object classification techniques to difference images in context Nearby Supernova Factory supernova search. Most current searches subtract reference from images, identify objects these and apply simple threshold cuts on parameters such as statistical significance, shape, motion reject cosmic rays, asteroids, subtraction artifacts. Although most static cleanly, even a very low false positive detection rate can lead hundreds non-supernova candidates which...
We present photometric and spectroscopic observations of galaxies hosting Type Ia supernovae (SNe Ia) observed by the Nearby Supernova Factory (SNfactory). Combining GALEX UV data with optical near infrared photometry, we employ stellar population synthesis techniques to measure SN host galaxy masses, star-formation rates (SFRs), reddening due dust. reinforce key role in deriving accurate estimates SFRs dust extinction. Optical spectra are fitted simultaneously for their continua emission...
We consider parallel computation for Gaussian process calculations to overcome computational and memory constraints on the size of datasets that can be analyzed. Using a hybrid parallelization approach uses both threading (shared memory) message-passing (distributed memory), we implement core linear algebra operations used in spatial statistics regression an R package called bigGP relies C MPI. The divides matrix into blocks such load is balanced across processes while communication between...
As data sets from DOE user science facilities grow in both size and complexity there is an urgent need for new capabilities to transfer, analyze manage the underlying scientific discoveries. LBNL's Superfacility project brings together experimental observational research instruments with computational network at National Energy Research Scientific Computing Center (NERSC) Sciences Network (ESnet) goal of enabling science. Here, we report on recent innovations project, including advanced...
We present four spectra of the Type Ia supernova (SN Ia) 2006D extending from -7 to +13 days with respect B-band maximum. The include strongest signature unburned material at photospheric velocities observed in a SN date. earliest spectrum exhibits C II absorption features below 14,000 km/s, including distinctive \lambda 6580 feature. carbon signatures dissipate as approaches peak brightness. In addition discussing implications photospheric-velocity for white dwarf explosion models, we...
We introduce a method for identifying "twin" Type Ia supernovae, and using them to improve distance measurements. This novel approach supernova standardization is made possible by spectrophotometric time series observations from the Nearby Supernova Factory (SNfactory). begin with well-measured set of find pairs whose spectra match well across entire optical window, then test whether this leads smaller dispersion in their absolute brightnesses. analysis completed blinded fashion, ensuring...
We present a novel class of models for Type Ia supernova time-evolving spectral energy distributions (SEDs) and absolute magnitudes: they are each modeled as stochastic functions described by Gaussian processes. The values the SED magnitudes defined through well-defined regression prescriptions, so that data directly inform models. As proof concept, we implement model synthetic photometry built from spectrophotometric time series Nearby Supernova Factory. Absolute at peak B brightness...
We present Keck LRIS spectroscopy and $g$-band photometry of the metal-poor, low-luminosity host galaxy super-Chandrasekhar mass Type Ia supernova SN 2007if. Deep imaging reveals its apparent magnitude to be $m_g=23.15\pm0.06$, which at spectroscopically-measured redshift $z_{helio}=0.07450\pm0.00015$ corresponds an absolute $M_g=-14.45\pm0.06$. Galaxy $g-r$ color constrains mass-to-light ratio, giving a stellar estimate $\log(M_*/M_\odot)=7.32\pm0.17$. Balmer absorption in continuum, along...
Today, our picture of the Universe radically differs from that just over a decade ago. We now know is not only expanding as Hubble discovered in 1929, but rate expansion accelerating, propelled by mysterious new physics dubbed “Dark Energy”. This revolutionary discovery was made comparing brightness nearby Type Ia supernovae (which exploded past billion years) to much more distant ones (from up seven years ago). The reliability this comparison hinges upon very detailed understanding events....
As a candidate 'super-Chandrasekhar' or 09dc-like Type Ia supernova (SN Ia), SN 2012dn shares many characteristics with other members of this remarkable class objects but lacks their extraordinary luminosity. Here, we present and discuss the most comprehensive optical data set to date, comprised densely sampled series early-time spectra obtained within Nearby Supernova Factory project, plus photometry spectroscopy at VLT about 1 yr after explosion. The light curves, colour spectral time...