Sloan Digital Sky Survey Telescope Research Articles

A Study of R-Magnitude Dependence in Spatial Orientation of Spin Vectors of SDSS DR-7 Galaxies of Redshift 0.10 < Z < 0.11

We present a study of spin vector orientations of 44749 r-magnitude SDSS (Sloan Digital Sky Survey) galaxies having redshift 0.10 to 0.11. The r -magnitudes are observed through 616.5 nm CCD (charge coupled device) filter attached to SDSS telescope located at New Mexico, USA. We have converted two dimensional data to three dimensional galaxy rotation axes. Our aim is to find out non-random effects in the spatial orientation of galaxies. In addition, we wanted to check r-magnitude dependence in the spatial orientation. The expected isotropy distribution curves are obtained by removing the selection effects and performing a random simulation method. In general, spin vector orientations of galaxies is found to be random, supporting Hierarchy model of galaxy formation. A local anisotropy is observed in few samples suggesting a gravitational tidal interaction between neighbor galaxies.

Chasing down variable stars from a decade-long dataset

Finding and characterizing variable stars is at the heart of a relatively modern branch of astronomy named time-domain astrophysics. Variable Stars are ordinary stars that change in brightness on widely varying degrees. Characterizing the details of how this brightness fluctuates and on what timescales, as well as the star's average properties (mean brightness, temperature, etc.), is greatly important to understanding the process of stellar evolution. For this project, we use data over ten years from the 0.5 meter Sloan Digital Sky Survey telescope. We will develop tools that can identify several variable stars, estimate their variability periods and timescales, and determine the shape of their brightness variations over this time.

Gravitational Fluctuations as an Alternative to Inflation

The ability to reproduce the observed matter power spectrum P ( k ) to high accuracy is often considered as a triumph of inflation. In this work, we explore an alternative explanation for the power spectrum based on nonperturbative quantum field-theoretical methods applied to Einstein’s gravity, instead of ones based on inflation models. In particular, the power spectral index, which governs the slope on the P ( k ) graph, can be related to critical scaling exponents derived from the Wilson renormalization group analysis. We find that the derived value fits favorably with the Sloan Digital Sky Survey telescope data. We then make use of the transfer functions, based only on the Boltzmann equations, which describe states out of equilibrium, and Einstein’s general relativity, to extrapolate the power spectrum to the Cosmic Microwave Background (CMB) regime. We observe that the results fit rather well with current data. Our approach contrasts with the conventional explanation, which uses inflation to generate the scale-invariant Harrison–Zel’dovich spectrum on CMB scales and uses the transfer function to extrapolate it to the galaxy regime. The results we present here only assume quantum field theory and Einstein’s gravity, and hence provide a competing explanation of the power spectrum, without relying on the assumptions usually associated with inflationary models. At the end, we also outline several testable predictions in this picture that deviate from the conventional picture of inflation and which hopefully will become verifiable in the near future with increasingly accurate measurements.

A Study of z-Magnitude Dependence in the Spatial Orientation of Angular Momentum Vectors of Galaxies having Redshift < 30,000 km s-1

I present a study of spin vector orientations of 229,675 z-magnitude SDSS (Sloan Digital Sky Survey) galaxies having red shift of 0.05 to 0.10. The z-magnitudes are observed through 913.3 nm CCD (charge coupled device) filter attached to SDSS telescope located at New Mexico, USA. We have converted two dimensional data to three-dimensional by Godlowskian Transformation. Our aim is to find out non-random effects in the spatial orientation of galaxies. The expected isotropy distribution curves are obtained by removing the selection effects and performing a random simulation method. In general, spinvector orientations of galaxies are found to be random, supporting Hierarchy model of galaxy formation. In some samples (z12 and z13) of polar angle distribution is observed anisotropy supporting Primordial Vorticity Theory. For azimuthal angle distribution in more sample we observed anisotropy result. A local anisotropy is observed in few samples suggesting a gravitational tidal interaction, merging process and gravitational lensing effect.

A Study of r- and u-Magnitude Dependence in the Spatial Orientation of Spin Vectors of SDSS Galaxies having redshift 0.10 < z < 0.11

We present a study of spin vector orientations of 44749 r and u-magnitude SDSS (Sloan Digital Sky Survey) galaxies having redshift 0.10 to 0.11. The r and u-magnitudes are observed through 616.5 nm and 354.3 nm CCD (charge coupled device) filter attached to SDSS telescope located at New Mexico, USA. We have converted two dimensional data to three dimensional galaxy rotation axes. Our aim is to find out non-random effects in the spatial orientation of galaxies. In addition, we wanted to check r and u-magnitude dependence in the spatial orientation. The expected isotropy distribution curves are obtained by removing the selection effects and performing a random simulation method. In general, spin vector orientations of galaxies is found to be random, supporting Hierarchy model of galaxy formation. A local anisotropy is observed in few samples suggesting a gravitational tidal interaction between neighbor galaxies, a merging process in which the angular momentum vector distort the original alignment of evolution of rotational supported system to the randomized system.The Himalayan Physics Year 5, Vol. 5, Kartik 2071 (Nov 2014)Page: 1-11

A Study of co-existence between the Hubble flow and the random alignments of spin vectors of SDSS galaxies

We present a study of spin vector orientation of 14,118 SDSS (Sloan Digital Sky Survey) galaxies having redshift in the range 0.19 to 0.20 (radial velocity 57,000 km/s to 60,000 km/s) with respect to galactic coordinate system using 7th data release (2008, October). These galaxies were observed through SDSS telescope of Apache Point Observatory located at New Mexico, USA. The photometric database is made available through our collaboration with institute of Astro-particle physics, Innsbruck University, Austria. We used the `Godlowskian' method to convert two dimensional data to three dimensional galaxy rotation axes. Our intension is to find out non-random effects in the spatial orientation of galaxies and to check redshift dependence. The expected isotropy distribution curves are obtained by removing the selection effects and performing a random simulation method. The observed and expected polar and azimuthal angle distributions are compared by using three statistical tests- chi-square, auto-correlation and the Fourier. It is found that the spatial orientation of galaxies tend to be oriented randomly with respect to the galactic coordinate system, supporting hierarchy model of galaxy evolution. In few cases we noticed a preference, probably due to the gravitational shearing or tidal effects in the large scale structure. In general, redshift is found to be independent of orientation. Hence, a very good correlation between the Hubble flow (redshift) and the random alignments of spin vectors of SDSS galaxies is noticed.DOI: http://dx.doi.org/10.3126/bibechana.v12i0.11787BIBECHANA 12 (2015) 114-127

Investigating emission-line galaxy surveys with the Sloan Digital Sky Survey infrastructure

The Baryon Acoustic Oscillation (BAO) feature in the power spectrum of galaxies provides a standard ruler to probe the accelerated expansion of the Universe. The current surveys covering a comoving volume sufficient to unveil the BAO scale are limited to redshift $z \lesssim 0.7$. In this paper, we study several galaxy selection schemes aiming at building an emission-line-galaxy (ELG) sample in the redshift range $0.6<z<1.7$, that would be suitable for future BAO studies using the Baryonic Oscillation Spectroscopic Survey (BOSS) spectrograph on the Sloan Digital Sky Survey (SDSS) telescope. We explore two different colour selections using both the SDSS and the Canada France Hawai Telescope Legacy Survey (CFHT-LS) photometry in the u, g, r, and i bands and evaluate their performance selecting luminous ELG. From about 2,000 ELG, we identified a selection scheme that has a 75 percent redshift measurement efficiency. This result confirms the feasibility of massive ELG surveys using the BOSS spectrograph on the SDSS telescope for a BAO detection at redshift $z\sim1$, in particular the proposed eBOSS experiment, which plans to use the SDSS telescope to combine the use of the BAO ruler with redshift space distortions using emission line galaxies and quasars in the redshift $0.6<z<2.2$.

The 2.5 m Telescope of the Sloan Digital Sky Survey

We describe the design, construction, and performance of the Sloan Digital Sky Survey telescope located at Apache Point Observatory. The telescope is a modified two-corrector Ritchey-Chretien design with a 2.5 m, f/2.25 primary, a 1.08 m secondary, a Gascoigne astigmatism corrector, and one of a pair of interchangeable highly aspheric correctors near the focal plane, one for imaging and the other for spectroscopy. The final focal ratio is f/5. The telescope is instrumented by a wide-area, multiband CCD camera and a pair of fiber-fed double spectrographs. Novel features of the telescope include the following: (1) A 3° diameter (0.65 m) focal plane that has excellent image quality and small geometric distortions over a wide wavelength range (3000-10,600 A) in the imaging mode, and good image quality combined with very small lateral and longitudinal color errors in the spectroscopic mode. The unusual requirement of very low distortion is set by the demands of time-delay-and-integrate (TDI) imaging. (2) Very high precision motion to support open-loop TDI observations. (3) A unique wind baffle/enclosure construction to maximize image quality and minimize construction costs. The telescope had first light in 1998 May and began regular survey operations in 2000.

A Strategy for Finding Near-Earth Objects with the SDSS Telescope

We present a detailed observational strategy for finding near-Earth objects (NEOs) with the Sloan Digital Sky Survey (SDSS) telescope. We investigate strategies in normal, unbinned mode, as well as binning the CCDs 2 × 2 or 3 × 3, which affects the sky coverage rate and the limiting apparent magnitude. We present results from 1 month, 3 year, and 10 year simulations of such surveys. For each cadence and binning mode, we evaluate the possibility of achieving the Spaceguard goal of detecting 90% of 1 km NEOs (absolute magnitude H ≤ 18 for an albedo of 0.1). We find that an unbinned survey is most effective at detecting H ≤ 20 NEOs in our sample. However, a 3 × 3 binned survey reaches the Spaceguard goal after only 7 years of operation. As the proposed large survey telescopes (Pan-STARRS, LSST) are at least 5–10 years from operation, an SDSS NEO survey could make a significant contribution to the detection and photometric characterization of the NEO population.

The Sloan Digital Sky Survey

The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey of 104 deg2 in the North Galactic Cap, currently underway with the 2.5-m SDSS Telescope at the Apache Point Observatory in New Mexico. The data products will include u, g, r, i and z-band imaging of several 108 sources and R = 2000 spectra of 106 galaxies. The imaging will have 10-sigma limiting (AB) magnitudes of (u, g, r, i, z) = (21.4, 22.6, 22.3, 21.7, 20.1). The “Main” sample of 9 x 105 galaxies, selected to have r &lt; 17.7 mag, will have spectra with signal-to-noise ratio on the order of ~ 10 per resolution element, and median redshift z ~ 0.1. There will also be a sample of 105 luminous elliptical galaxies, selected on the basis of apparent color and magnitude, which will extend out to redshift z ~ 0.4. The data will be released steadily over the next five years.On the order of one percent of the eventual data volume has been assembled at the time of this meeting, with a few hundred square degrees of survey-quality 5-band imaging, and over 104 survey-quality spectra. In the refereed literature there are detailed descriptions of the survey design, goals and hardware (York et al 2000; Gunn et al. 1998) and first scientific results (e.g., Ivezic et al 2000; Fischer et al. 2000; Leggett et al. 2000; Yanny et al. 2000).Relevant to measures of the extragalactic background emission, the survey has found many z &gt; 4 quasars and has measured the evolution in their space density (e.g., Fan et al. 2000). Measures of bright galaxy counts, the local galaxy luminosity function, and the evolution of elliptical galaxies are in preparation.