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Yang Y.,Max Planck Institute for Astronomy | Decarli R.,Max Planck Institute for Astronomy | Dannerbauer H.,CEA Saclay Nuclear Research Center | Dannerbauer H.,University of Vienna | And 14 more authors.
Astrophysical Journal | Year: 2012

In order to constrain the bolometric luminosities, dust properties, and molecular gas content of giant Lyα nebulae, the so-called Lyα blobs, we have carried out a study of dust continuum and CO line emission in two well-studied representatives of this population at z ∼ 3: an Lyα blob discovered by its strong Spitzer Multiband Infrared Photometer 24 μm detection (LABd05) and the Steidel blob 1 (SSA22-LAB01). We find that the spectral energy distribution of LABd05 is well described by an active-galactic-nucleus-starburst composite template with L FIR = (4.0 0.5) × 1012 L, comparable to high-z submillimeter galaxies and ultraluminous infrared galaxies. New Large APEX Bolometer Camera 870 μm measurements rule out the reported Submillimeter Common-User Bolometer Array detection of the SSA22-LAB01 (S 850 μm = 16.8mJy) at the >4σ level. Consistent with this, ultradeep Plateau de Bure Interferometer observations with 2″ spatial resolution also fail to detect any 1.2mm continuum source down to 0.45mJy beam-1 (3σ). Combined with the existing (sub)millimeter observations in the literature, we conclude that the FIR luminosity of SSA22-LAB01 remains uncertain. No CO line is detected in either case down to integrated flux limits of S νΔV ≲ 0.25-1.0Jykms-1, indicating a modest molecular gas reservoir, M(H2) < (1-3) × 1010M. The non-detections exclude, with high significance (12σ), the previous tentative detection of a CO J=4-3 line in the SSA22-LAB01. The increased sensitivity afforded by the Atacama Large Millimeter/submillimeter Array will be critical in studying molecular gas and dust in these interesting systems. © 2012 The American Astronomical Society. All rights reserved. Source

Naab T.,Max Planck Institute for Astrophysics | Oser L.,Max Planck Institute for Astrophysics | Oser L.,Columbia University | Emsellem E.,European Southern Observatory | And 32 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We present a detailed two-dimensional stellar dynamical analysis of a sample of 44 cosmological hydrodynamical simulations of individual central galaxies with stellar masses of 2 × 1010M{N-ary circled dot operator} ≲ M* ≲ 6 × 1011M≲. Kinematic maps of the stellar line-of-sight velocity, velocity dispersion and higher order Gauss-Hermite moments h3 and h4 are constructed for each central galaxy and for the most massive satellites. The amount of rotation is quantified using the λR-parameter. The velocity, velocity dispersion, h3 and h4 fields of the simulated galaxies show a diversity similar to observed kinematic maps of early-type galaxies in the ATLAS3D survey. This includes fast (regular), slow and misaligned rotation, hot spheroids with embedded cold disc components as well as galaxies with counter-rotating cores or central depressions in the velocity dispersion. We link the present-day kinematic properties to the individual cosmological formation histories of the galaxies. In general, major galaxy mergers have a significant influence on the rotation properties resulting in both a spin-down as well as a spin-up of the merger remnant. Lower mass galaxies with significant (≳18 per cent) in situ formation of stars since z ≈ 2, or with additional gas-rich major mergers - resulting in a spin-up - in their formation history, form elongated (σ 0.45) fast rotators (λR 0.46) with a clear anticorrelation of h3 and v/σ. An additional formation path for fast rotators includes gas-poor major mergers leading to a spin-up of the remnants (λR 0.43). This formation path does not result in anticorrelated h3 and v/σ. The formation histories of slow rotators can include late major mergers. If the merger is gas rich, the remnant typically is a less flattened slow rotator with a central dip in the velocity dispersion. If the merger is gas poor, the remnant is very elongated (σ 0.43) and slowly rotating (λR 0.11). The galaxies most consistent with the rare class of non-rotating round early-type galaxies grow by gas-poor minor mergers alone. In general, more massive galaxies have less in situ star formation since z 2, rotate slower and have older stellar populations. We discuss general implications for the formation of fast and slowly rotating galaxies as well as the weaknesses and strengths of the underlying models. © 2014 The Authors. Source

Forero-Romero J.E.,Leibnitz Institute For Astrophysik Potsdam Aip | Yepes G.,Autonomous University of Madrid | Gottlober S.,Leibnitz Institute For Astrophysik Potsdam Aip | Knollmann S.R.,Autonomous University of Madrid | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

Using clara (code for Lyman alpha radiation analysis) we constrain the escape fraction of Lyman α radiation in galaxies in the redshift range 5 ≲z≲ 7, based on the MareNostrum High-z Universe, a smoothed particle hydrodynamics cosmological simulation with more than two billion particles. We approximate Lyman α emitters (LAEs) as dusty gaseous slabs with Lyman α radiation sources homogeneously mixed in the gas. Escape fractions for such a configuration and for different gas and dust contents are calculated using our newly developed radiative transfer code clara. The results are applied to the MareNostrum High-z Universe numerical galaxies. The model shows a weak redshift evolution and good agreement with estimations of the escape fraction as a function of reddening from observations at z~ 2.2 and z~ 3. We extend the slab model by including additional dust in a clumpy component in order to reproduce the ultraviolet (UV) continuum luminosity function (LF) and UV colours at redshifts z > rsim 5. The LAE LF, based on the extended clumpy model, reproduces broadly the bright end of the LF derived from observations at z~ 5 and z~ 6. At z~ 7, our model overpredicts the LF by roughly a factor of 4, presumably because the effects of the neutral intergalactic medium are not taken into account. The remaining tension between the observed and simulated faint end of the LF, both in the UV continuum and Lyman α at redshifts z~ 5 and z~ 6, points towards an overabundance of simulated LAEs hosted in haloes of masses 1.0 × 1010≤Mh≤ 4.0 × 1010h-1M⊙. Given the difficulties in explaining the observed overabundance by dust absorption, a probable origin of the mismatch is the high star formation rate in the simulated haloes around the quoted mass range. A more efficient supernova feedback should be able to regulate the star formation process in the shallow potential wells of these haloes. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS. Source

Serra P.,Netherlands Institute for Radio Astronomy | Serra P.,CSIRO | Oser L.,Max Planck Institute for Astrophysics | Oser L.,Columbia University | And 35 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

One quarter of all nearby early-type galaxies (ETGs) outside Virgo host a disc/ring of HI with size from a few to tens of kpc and mass up to 109M{N-ary circled plus operator} . Here we investigate whether this HI is related to the presence of a stellar disc within the host making use of the classification of ETGs in fast and slow rotators (FR/SR). We find a large diversity of HI masses and morphologies within both families. Surprisingly, SRs are detected as often, host as much HI and have a similar rate of HI discs/rings as FRs. Accretion of HI is therefore not always linked to the growth of an inner stellar disc. The weak relation between HI and stellar disc is confirmed by their frequent kinematical misalignment in FRs, including cases of polar and counterrotating gas. In SRs theHI is usually polar.This complex picture highlights a diversity ofETGformation histories which may be lost in the relative simplicity of their inner structure and emerges when studying their outer regions.We find that CDMhydrodynamical simulations have difficulties reproducing the HI properties of ETGs. The gas discs formed in simulations are either too massive or too small depending on the star formation feedback implementation. Kinematical misalignments match the observations only qualitatively. The main point of conflict is that nearly all simulated FRs and a large fraction of all simulated SRs host corotating HI. This establishes the HI properties of ETGs as a novel challenge to simulations. © 2014 The Authors. Source

Weijmans A.-M.,University of St. Andrews | Weijmans A.-M.,University of Toronto | De Zeeuw P.T.,European Southern Observatory | De Zeeuw P.T.,Leiden University | And 30 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We use the ATLAS3D sample to perform a study of the intrinsic shapes of early-type galaxies, taking advantage of the available combined photometric and kinematic data. Based on our ellipticity measurements from the Sloan Digital Sky Survey Data Release 7, and additional imaging from the Isaac Newton Telescope, we first invert the shape distribution of fast and slow rotators under the assumption of axisymmetry. The so-obtained intrinsic shape distribution for the fast rotators can be described with a Gaussian with a mean flattening of q = 0.25 and standard deviation σq = 0.14, and an additional tail towards rounder shapes. The slow rotators are much rounder, and are well described with a Gaussian with mean q = 0.63 and σq = 0.09. We then checked that our results were consistent when applying a different and independent method to obtain intrinsic shape distributions, by fitting the observed ellipticity distributions directly using Gaussian parametrizations for the intrinsic axis ratios. Although both fast and slow rotators are identified as early-type galaxies in morphological studies, and in many previous shape studies are therefore grouped together, their shape distributions are significantly different, hinting at different formation scenarios. The intrinsic shape distribution of the fast rotators shows similarities with the spiral galaxy population. Including the observed kinematic misalignment in our intrinsic shape study shows that the fast rotators are predominantly axisymmetric, with only very little room for triaxiality. For the slow rotators though there are very strong indications that they are (mildly) triaxial. © 2014. Source

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