Browsing by Author "Biswas, Rahul"

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    The LSST DESC DC2 Simulated Sky Survey
    (2021) Abolfathi, Bela; Alonso, David; Armstrong, Robert; Aubourg, Eric; Awan, Humna; Babuji, Yadu N.; Bauer, Franz Erik; Bean, Rachel; Beckett, George; Biswas, Rahul; Bogart, Joanne R.; Boutigny, Dominique; Chard, Kyle; Chiang, James; Claver, Chuck F.; Cohen-Tanugi, Johann; Combet, Celine; Connolly, Andrew J.; Daniel, Scott F.; Digel, Seth W.; Drlica-Wagner, Alex; Dubois, Richard; Gangler, Emmanuel; Gawiser, Eric; Glanzman, Thomas; Gris, Phillipe; Habib, Salman; Hearin, Andrew P.; Heitmann, Katrin; Hernandez, Fabio; Hlozek, Renee; Hollowed, Joseph; Ishak, Mustapha; Ivezic, Zeljko; Jarvis, Mike; Jha, Saurabh W.; Kahn, Steven M.; Kalmbach, J. Bryce; Kelly, Heather M.; Kovacs, Eve; Korytov, Danila; Krughoff, K. Simon; Lage, Craig S.; Lanusse, Francois; Larsen, Patricia; Le Guillou, Laurent; Li, Nan; Longley, Emily Phillips; Lupton, Robert H.; Mandelbaum, Rachel; Mao, Yao-Yuan; Marshall, Phil; Meyers, Joshua E.; Moniez, Marc; Morrison, Christopher B.; Nomerotski, Andrei; O'Connor, Paul; Park, HyeYun; Park, Ji Won; Peloton, Julien; Perrefort, Daniel; Perry, James; Plaszczynski, Stephane; Pope, Adrian; Rasmussen, Andrew; Reil, Kevin; Roodman, Aaron J.; Rykoff, Eli S.; Sanchez, F. Javier; Schmidt, Samuel J.; Scolnic, Daniel; Stubbs, Christopher W.; Tyson, J. Anthony; Uram, Thomas D.; Villarreal, Antonio; Walter, Christopher W.; Wiesner, Matthew P.; Wood-Vasey, W. Michael; Zuntz, Joe
    We describe the simulated sky survey underlying the second data challenge (DC2) carried out in preparation for analysis of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) by the LSST Dark Energy Science Collaboration (LSST DESC). Significant connections across multiple science domains will be a hallmark of LSST; the DC2 program represents a unique modeling effort that stresses this interconnectivity in a way that has not been attempted before. This effort encompasses a full end-to-end approach: starting from a large N-body simulation, through setting up LSST-like observations including realistic cadences, through image simulations, and finally processing with Rubin's LSST Science Pipelines. This last step ensures that we generate data products resembling those to be delivered by the Rubin Observatory as closely as is currently possible. The simulated DC2 sky survey covers six optical bands in a wide-fast-deep area of approximately 300 deg(2), as well as a deep drilling field of approximately 1 deg(2). We simulate 5 yr of the planned 10 yr survey. The DC2 sky survey has multiple purposes. First, the LSST DESC working groups can use the data set to develop a range of DESC analysis pipelines to prepare for the advent of actual data. Second, it serves as a realistic test bed for the image processing software under development for LSST by the Rubin Observatory. In particular, simulated data provide a controlled way to investigate certain image-level systematic effects. Finally, the DC2 sky survey enables the exploration of new scientific ideas in both static and time domain cosmology.
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    ZTF Early Observations of Type Ia Supernovae. III. Early-time Colors As a Test for Explosion Models and Multiple Populations
    (2020) Bulla, Mattia; Miller, Adam A.; Yao, Yuhan; Dessart, Luc; Dhawan, Suhail; Papadogiannakis, Semeli; Biswas, Rahul; Goobar, Ariel; Kulkarni, S. R.; Nordin, Jakob; Nugent, Peter; Polin, Abigail; Sollerman, Jesper; Bellm, Eric C.; Coughlin, Michael W.; Dekany, Richard; Golkhou, V. Zach; Graham, Matthew J.; Kasliwal, Mansi M.; Kupfer, Thomas; Laher, Russ R.; Masci, Frank J.; Porter, Michael; Rusholme, Ben; Shupe, David L.
    Colors of Type Ia supernovae (SNe Ia) in the first few days after explosion provide a potential discriminant between different models. In this paper, we present g - r colors of 65 SNe Ia discovered within 5 days from first light by the Zwicky Transient Facility in 2018, a sample that is about three times larger than that in the literature. We find that g - r colors are intrinsically rather homogeneous at early phases, with about half of the dispersion attributable to photometric uncertainties (0.18 mag). Colors are nearly constant starting from 6 days after first light (g-r similar to -0.15 mag), while the time evolution at earlier epochs is characterized by a continuous range of slopes, from events rapidly transitioning from redder to bluer colors (slope of similar to-0.25 mag day(-1)) to events with a flatter evolution. The continuum in the slope distribution is in good agreement both with models requiring some amount of Ni-56 mixed in the outermost regions of the ejecta and with "double-detonation" models having thin helium layers (M-He = 0.01 M-circle dot) and varying carbon-oxygen core masses. At the same time, six events show evidence for a distinctive "red bump" signature predicted by double-detonation models with larger helium masses. We finally identify a significant correlation between the early-timeg - rslopes and supernova brightness, with brighter events associated to flatter color evolution (p-value = 0.006). The distribution of slopes, however, is consistent with being drawn from a single population, with no evidence for two components as claimed in the literature based on B - V colors.