Papers by Erfan Nourbakhsh
Monthly Notices of the Royal Astronomical Society, 2020
Many scientific investigations of photometric galaxy surveys require redshift estimates, whose un... more Many scientific investigations of photometric galaxy surveys require redshift estimates, whose uncertainty properties are best encapsulated by photometric redshift (photo-z) posterior probability density functions (PDFs). A plethora of photo-z PDF estimation methodologies abound, producing discrepant results with no consensus on a preferred approach. We present the results of a comprehensive experiment comparing twelve photo-z algorithms applied to mock data produced forLarge Synoptic Survey Telescope The Rubin Observatory Legacy Survey of Space and Time (lsst) Dark Energy Science Collaboration (desc). By supplying perfect prior information, in the form of the complete template library and a representative training set as inputs to each code, we demonstrate the impact of the assumptions underlying each technique on the output photo-z PDFs. In the absence of a notion of true, unbiased photo-z PDFs, we evaluate and interpret multiple metrics of the ensemble properties of the derived p...
Given the fact that accretion discs are associated with their parent molecular cloud, we studied ... more Given the fact that accretion discs are associated with their parent molecular cloud, we studied its effects as a constraint on the outer boundary of the viscous-resistive polytropic self-gravitating accretion flows subject to the mass and angular momentum loss.
Self-similar and semi-analytical solutions are found for the height-averaged equations govern the... more Self-similar and semi-analytical solutions are found for the height-averaged equations govern the dynamical behavior of a polytropic, self-gravitating disk under the effects of winds, around the nascent object. In order to describe time evolution of the system, we adopt a radius dependent mass loss rate, then highlight its importance on both the traditional α and innovative β models of viscosity prescription. In agreement with some other studies, our solutions represent that Toomre parameter is less than one in most regions on the β-disk which indicate that in such disks gravitational instabilities can occur in various distances from the central accretor and so the β-disk model might provide a good explanation of how the planetary systems form. The purpose of the present work is twofold. First, examining the structure of disk with wind in comparison to no-wind solution; and second, to see if the adopted viscosity prescription affects significantly the dynamical behavior of the disk-...
arXiv: Cosmology and Nongalactic Astrophysics, 2019
Author(s): Drlica-Wagner, Alex; Mao, Yao-Yuan; Adhikari, Susmita; Armstrong, Robert; Banerjee, Ar... more Author(s): Drlica-Wagner, Alex; Mao, Yao-Yuan; Adhikari, Susmita; Armstrong, Robert; Banerjee, Arka; Banik, Nilanjan; Bechtol, Keith; Bird, Simeon; Boddy, Kimberly K; Bonaca, Ana; Bovy, Jo; Buckley, Matthew R; Bulbul, Esra; Chang, Chihway; Chapline, George; Cohen-Tanugi, Johann; Cuoco, Alessandro; Cyr-Racine, Francis-Yan; Dawson, William A; Rivero, Ana Diaz; Dvorkin, Cora; Erkal, Denis; Fassnacht, Christopher D; Garcia-Bellido, Juan; Giannotti, Maurizio; Gluscevic, Vera; Golovich, Nathan; Hendel, David; Hezaveh, Yashar D; Horiuchi, Shunsaku; Jee, M James; Kaplinghat, Manoj; Keeton, Charles R; Koposov, Sergey E; Lam, Casey Y; Li, Ting S; Lu, Jessica R; Mandelbaum, Rachel; McDermott, Samuel D; McNanna, Mitch; Medford, Michael; Meyer, Manuel; Marc, Moniez; Murgia, Simona; Nadler, Ethan O; Necib, Lina; Nuss, Eric; Pace, Andrew B; Peter, Annika HG; Polin, Daniel A; Prescod-Weinstein, Chanda; Read, Justin I; Rosenfeld, Rogerio; Shipp, Nora; Simon, Joshua D; Slatyer, Tracy R; Straniero, Os...
Proceedings of the International Astronomical Union, 2012
Given the fact that accretion discs are associated with their parent molecular cloud, we studied ... more Given the fact that accretion discs are associated with their parent molecular cloud, we studied its effects as a constraint on the outer boundary of the viscous-resistive polytropic self-gravitating accretion flows subject to the mass and angular momentum loss.
The Astrophysical Journal, 2013
Upcoming deep imaging surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Ti... more Upcoming deep imaging surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time will be confronted with challenges that come with increased depth. One of the leading systematic errors in deep surveys is the blending of objects due to higher surface density in the more crowded images; a considerable fraction of the galaxies which we hope to use for cosmology analyses will overlap each other on the observed sky. In order to investigate these challenges, we emulate blending in a mock catalogue consisting of galaxies at a depth equivalent to 1.3 years of the full 10-year Rubin Observatory that includes effects due to weak lensing, ground-based seeing, and the uncertainties due to extraction of catalogues from imaging data. The emulated catalogue indicates that approximately 12% of the observed galaxies are “unrecognized” blends that contain two or more objects but are detected as one. Using the positions and shears of half a billion distant galaxies, we compute shear...
The Open Journal of Astrophysics
Cambridge University Press, Published
Given the fact that accretion discs are associated with their parent molecular cloud, we studied ... more Given the fact that accretion discs are associated with their parent molecular cloud, we studied its effects as a constraint on the outer boundary of the viscous polytropic self-gravitating accretion flows subject to the mass and angular momentum loss.
Astrophysical Journal (ApJ), American Astronomical Society, Published
Self-similar and semi-analytical solutions are found for the height-averaged equations governing ... more Self-similar and semi-analytical solutions are found for the height-averaged equations governing the dynamical behavior of a polytropic, self-gravitating disk under the effects of winds, around the nascent object.
Talks by Erfan Nourbakhsh
The large spectroscopic and photometric surveys such as Two-degree-Field (2dF) Galaxy Redshift Su... more The large spectroscopic and photometric surveys such as Two-degree-Field (2dF) Galaxy Redshift Survey and Sloan Digital Sky Survey (SDSS) are of great importance for studying the evolutionary process of galaxies within groups. Here, we describe the group sample and group members selection process by applying the statistical background subtraction and the color-magnitude relations.
Poster Presentations by Erfan Nourbakhsh
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Papers by Erfan Nourbakhsh
Talks by Erfan Nourbakhsh
Poster Presentations by Erfan Nourbakhsh