SDSS-IV eBOSS emission-line galaxy pilot survey

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMAstronomy and Astrophysics 592 (2016): A121reproduced with permission from Astronomy & AstrophysicsThe Sloan Digital Sky Survey IV extended Baryonic Oscillation Spectroscopic Survey (SDSS-IV/eBOSS) will observe 195 000 emission-line galaxies (ELGs) to measure the baryonic acoustic oscillation (BAO) standard ruler at redshift 0.9. To test different ELG selection algorithms, 9000 spectra were observed with the SDSS spectrograph as a pilot survey based on data from several imaging surveys. First, using visual inspection and redshift quality flags, we show that the automated spectroscopic redshifts assigned by the pipeline meet the quality requirements for a reliable BAO measurement. We also show the correlations between sky emission, signal-to-noise ratio in the emission lines, and redshift error. Then we provide a detailed description of each target selection algorithm we tested and compare them with the requirements of the eBOSS experiment. As a result, we provide reliable redshift distributions for the different target selection schemes we tested. Finally, we determine an target selection algorithms that is best suited to be applied on DECam photometry because they fulfill the eBOSS survey efficiency requirementsJ.C .and F.P. acknowledge support from the Spanish MICINNs Consolider-Ingenio 2010 Programme under grant MultiDark CSD2009-00064, MINECO Centro de Excelencia Severo Ochoa Programme under the grants SEV-2012-0249, FPA2012-34694, and the projects AYA2014- 60641-C2-1-P and AYA2012-31101. F.P. acknowledges the spanish MEC Salvador de Madariaga program, Ref. PRX14/00444. T.D. and J.P.K. acknowledge support from the LIDA ERC advanced grant. AR acknowledges funding from the P2IO LabEx (ANR-10-LABX-0038) in the framework Investissements d’Avenir (ANR- 11-IDEX-0003-01) managed by the French National Research Agency (ANR). The DES data management system is supported by the National Science Foundation under Grant Number AST-1138766. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2012-39559, ESP2013- 48274, FPA2013-47986, and Centro de Excelencia Severo Ochoa SEV-2012- 0234. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007−2013) including ERC grant agreements 240672, 291329, and 30647

Improved LeRoy-Bernstein near-dissociation expansion formula. Tutorial application to photoassociation spectroscopy of long-range states

NDE (Near-dissociation expansion) including LeRoy-Bernstein formulas are improved by taking into account the multipole expansion coefficients and the non asymptotic part of the potential curve. Applying these new simple analytical formulas to photoassociation spectra of cold alkali atoms, we improve the determination of the asymptotic coefficient, reaching a 1% accuracy, for long-range relativistic potential curve of diatomic molecules.Comment: This article is part of Daniel Comparat's PhD thesis available at http://tel.ccsd.cnrs.fr

Ionization of Rydberg atoms embedded in an ultracold plasma

We have studied the behavior of cold Rydberg atoms embedded in an ultracold plasma. We demonstrate that even deeply bound Rydberg atoms are completely ionized in such an environment, due to electron collisions. Using a fast pulse extraction of the electrons from the plasma we found that the number of excess positive charges, which is directly related to the electron temperature Te, is not strongly affected by the ionization of the Rydberg atoms. Assuming a Michie-King equilibrium distribution, in analogy with globular star cluster dynamics, we estimate Te. Without concluding on heating or cooling of the plasma by the Rydberg atoms, we discuss the range for changing the plasma temperature by adding Rydberg atoms.Comment: To be published in P.R.

The SDSS-IV extended baryon oscillation spectroscopic survey: luminous red galaxy target selection

The Astrophysical Journal 224.2 (2016): 34 reproduced by permission of the AASWe describe the algorithm used to select the luminous red galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-field Infrared Survey Explorer. LRG targets are required to meet a set of color selection criteria and have z-band and i-band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (median redshift 0.71). We demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS ancillary programs to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least ∼89% of the target sample yields secure redshift measurements. We also present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reache

Measuring galaxy [OII] emission line doublet with future ground-based wide-field spectroscopic surveys

The next generation of wide-field spectroscopic redshift surveys will map the large-scale galaxy distribution in the redshift range 0.7< z<2 to measure baryonic acoustic oscillations (BAO). The primary optical signature used in this redshift range comes from the [OII] emission line doublet, which provides a unique redshift identification that can minimize confusion with other single emission lines. To derive the required spectrograph resolution for these redshift surveys, we simulate observations of the [OII] (3727,3729) doublet for various instrument resolutions, and line velocities. We foresee two strategies about the choice of the resolution for future spectrographs for BAO surveys. For bright [OII] emitter surveys ([OII] flux ~30.10^{-17} erg /cm2/s like SDSS-IV/eBOSS), a resolution of R~3300 allows the separation of 90 percent of the doublets. The impact of the sky lines on the completeness in redshift is less than 6 percent. For faint [OII] emitter surveys ([OII] flux ~10.10^{-17} erg /cm2/s like DESi), the detection improves continuously with resolution, so we recommend the highest possible resolution, the limit being given by the number of pixels (4k by 4k) on the detector and the number of spectroscopic channels (2 or 3).Comment: 5 pages, 1 figur

Observation of a resonant four-body interaction in cold cesium Rydberg atoms

Cold Rydberg atoms subject to long-range dipole-dipole interactions represent a particularly interesting system for exploring few-body interactions and probing the transition from 2-body physics to the many-body regime. In this work we report the direct observation of a resonant 4-body Rydberg interaction. We exploit the occurrence of an accidental quasi-coincidence of a 2-body and a 4-body resonant Stark-tuned Forster process in cesium to observe a resonant energy transfer requiring the simultaneous interaction of at least four neighboring atoms. These results are relevant for the implementation of quantum gates with Rydberg atoms and for further studies of many-body physics.Comment: 5 pages, 5 figure

Entanglement of two individual atoms using the Rydberg blockade

We report on our recent progress on the manipulation of single rubidium atoms trapped in optical tweezers and the generation of entanglement between two atoms, each individually trapped in neighboring tweezers. To create an entangled state of two atoms in their ground states, we make use of the Rydberg blockade mechanism. The degree of entanglement is measured using global rotations of the internal states of both atoms. Such internal state rotations on a single atom are demonstrated with a high fidelity.Comment: Proceeding of the 19th International Conference on Laser Spectroscopy ICOLS 2009, 7-13 June 2009, Hokkaido, Japa

Multi-tracer extension of the halo model:probing quenching and conformity in eBOSS

We develop a new Multi-Tracer Halo Occupation Distribution (\texttt{MTHOD}) framework for the galaxy distribution and apply it to the extended Baryon Oscillation Spectroscopic Survey (eBOSS) final data between $z=0.7-1.1$. We obtain a best fit \mthod\, for each tracer and describe the host halo properties of these galaxies. The mean halo masses for LRGs, ELGs and QSOs are found to be 1.9 \times 10^{13} \msolaroh, 1.1 \times 10^{12} \msolaroh and 5 \times 10^{12} \msolaroh respectively in the eBOSS data. We use the \texttt{MTHOD} framework to create mock galaxy catalogues and predict auto- and cross-correlation functions for all the tracers. Comparing these results with data, we investigate galactic conformity, the phenomenon whereby the properties of neighbouring galaxies are mutually correlated in a manner that is not captured by the basic halo model. We detect \textsl{1-halo} conformity at more than 3$\sigma$ statistical significance, while obtaining upper limit on \textsl{2-halo} conformity. We also look at the environmental dependence of the galaxy quenching efficiency and find that halo mass driven quenching successfully explains the behaviour in high density regions, but it fails to describe the quenching efficiency in low density regions. In particular, we show that the quenching efficiency in low density filaments is higher in the observed data, as compared to the prediction of the \mthod\ with halo mass driven quenching. The mock galaxy catalogue constructed in this paper is publicly available on https://www.roe.ac.uk/~salam/MTHOD/ .Comment: 17 pages, 12 figures, the software and mock catalogue should be made available through: https://www.roe.ac.uk/~salam/MTHOD/ , Accepted for publication in MNRA

Stellar population properties of individual massive early-type galaxies at 1.4 &lt; <i>z</i> &lt; 2

We analyse publicly available, individual spectra of four massive (⁠M>1011M⊙⁠) early-type galaxies with redshifts in the range 1.4 ≤ z ≤ 2 to determine their stellar content, extending our previous work up to z ∼ 2. The wide wavelength range of the VLT/X-Shooter spectroscopic data in the UV–Optical–NIR arms along with the availability of spectro-photometry allows us to explore different techniques to obtain the stellar population properties, namely through age/metallicity-sensitive spectral indices, full spectral fitting, and broad-band photometric fitting. Moreover, together with the widely used optical Lick indices, we consider further indices in the UV rest frame, and demonstrate that UV indices significantly help the accuracy of the resulting population parameters. We find galaxy ages ranging from 0.2 to 4 Gyr, where the oldest galaxy is found at the lowest redshift, with an excellent agreement between ages determined via indices, full spectral fitting, or broad-band colours. These ages are in perfect agreement with ages of local galaxies at the same velocity dispersion when we assume pure passive evolution. Total metallicities derived from indices show some scatter (between less than half-solar to very high values, [Z/H] ∼ 0.6). We speculate on possible mechanisms explaining these values, but given the sample size and low S/N of the spectra no conclusion can be made. Indices in the UV rest frame generally lead to similar conclusions as optical indices. For the oldest galaxy (4 Gyr), we show that its UV indices can only be explained by stellar population models including a UV contribution from old stellar populations, suggesting that old, UV bright populations start to inhabit mature galaxies of a few Gyr of age. This is the highest redshift (z ∼ 1.4) detection of the UV upturn up to date