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GalICS II: the [alpha/Fe]-mass relation in elliptical galaxies

ArXiv 0810.5753 (2008)

Authors:

A Pipino, JEG Devriendt, D Thomas, J Silk, S Kaviraj

Abstract:

We aim at reproducing the mass- and sigma-[alpha/Fe] relations in the stellar populations of early-type galaxies by means of a cosmologically motivated assembly history for the spheroids. We implement a detailed treatment for the chemical evolution of H, He, O and Fe in GalICS, a semi-analytical model for galaxy formation which successfully reproduces basic low- and high-redshift galaxy properties. The contribution of supernovae (both type Ia and II) as well as low- and intermediate-mass stars to chemical feedback are taken into account. We find that this chemically improved GalICS does not produce the observed mass- and sigma-[alpha/Fe] relations. The slope is too shallow and scatter too large, in particular in the low and intermediate mass range. The model shows significant improvement at the highest masses and velocity dispersions, where the predicted [alpha/Fe] ratios are now marginally consistent with observed values. We show that this result comes from the implementation of AGN (plus halo) quenching of the star formation in massive haloes. A thorough exploration of the parameter space shows that the failure of reproducing the mass- and sigma-[alpha/Fe] relations can partly be attributed to the way in which star formation and feedback are currently modelled. The merger process is responsible for a part of the scatter. We suggest that the next generation of semi-analytical model should feature feedback (either stellar of from AGN) mechanisms linked to single galaxies and not only to the halo, especially in the low and intermediate mass range. The integral star formation history of a single galaxy determines its final stellar [alpha/Fe] as it might be expected from the results of closed box chemical evolution models. (abridged)
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The 2dF-SDSS LRG and QSO Survey: The spectroscopic QSO catalogue

ArXiv 0810.4955 (2008)

Authors:

Scott M Croom, Gordon T Richards, Tom Shanks, Brian J Boyle, Robert G Sharp, Joss Bland-Hawthorn, Terry Bridges, Robert J Brunner, Russell Cannon, Daniel Carson, Kuenley Chiu, Matthew Colless, Warrick Couch, Roberto De Propris, Michael J Drinkwater, Alastair Edge, Stephen Fine, Jon Loveday, Lance Miller, Adam D Myers, Robert C Nichol, Phil Outram, Kevin Pimbblet, Isaac Roseboom, Nicholas Ross, Donald P Schneider, Allyn Smith, Chris Stoughton, Michael A Strauss, David Wake

Abstract:

We present the final spectroscopic QSO catalogue from the 2dF-SDSS LRG and QSO (2SLAQ) Survey. This is a deep, 18
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Living in a void: testing the Copernican principle with distant supernovae.

Phys Rev Lett 101:13 (2008) 131302

Authors:

Timothy Clifton, Pedro G Ferreira, Kate Land

Abstract:

We show that the local redshift dependence of the luminosity distance can be used to test the Copernican principle that we are not in a central or otherwise special region of the Universe. Future surveys of type Ia supernovae that focus on a redshift range of approximately 0.1-0.4 will be ideally suited to observationally determine the validity of the Copernican principle on new scales, as well as probing the degree to which dark energy must be considered a necessary ingredient in the Universe.
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The Cℓover experiment

Proceedings of SPIE the International Society for Optical Engineering 7020 (2008)

Authors:

L Piccirillo, P Ade, MD Audley, C Baines, R Battye, M Brown, P Calisse, A Challinor, WD Duncan, P Ferreira, W Gear, DM Glowacka, D Goldie, PK Grimes, M Halpern, V Haynes, GC Hilton, KD Irwin, B Johnson, M Jones, A Lasenby, P Leahy, J Leech, S Lewis, B Maffei, L Martinis, PD Mauskopf, SJ Melhuish, CE North, D O'Dea, S Parsley, G Pisano, CD Reintsema, G Savini, RV Sudiwala, D Sutton, A Taylor, G Teleberg, D Titterington, VN Tsaneva, C Tucker, R Watson, S Withington, G Yassin, J Zhang

Abstract:

CℓOVER is a multi-frequency experiment optimised to measure the Cosmic Microwave Background (CMB) polarization, in particular the B-mode component. CℓOVER comprises two instruments observing respectively at 97 GHz and 150/225 GHz. The focal plane of both instruments consists of an array of corrugated feed-horns coupled to TES detectors cooled at 100 mK. The primary science goal of CℓOVER is to be sensitive to gravitational waves down to r ∼ 0.03 (at 3σ) in two years of operations.
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Tracing high density gas in M 82 and NGC 4038

The Astropysical Journal Letters (2008)

Authors:

E Bayet, C Lintott, S Viti, J Martín-Pintado, S Martín, DA Williams, JMC Rawlings

Abstract:

We present the first detection of CS in the Antennae galaxies towards the NGC 4038 nucleus, as well as the first detections of two high-J (5-4 and 7-6) CS lines in the center of M 82. The CS(7-6) line in M 82 shows a profile that is surprisingly different to those of other low-J CS transitions we observed. This implies the presence of a separate, denser and warmer molecular gas component. The derived physical properties and the likely location of the CS(7-6) emission suggests an association with the supershell in the centre of M 82.
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