X-ray Emission from Haloes of Simulated Disc Galaxies

Bolometric and 0.2-2 keV X-ray luminosities of the hot gas haloes of simulated disc galaxies have been calculated at redshift z=0. The TreeSPH simulations are fully cosmological and the sample of 44 disc galaxies span a range in characteristic circular speeds of V_c = 130-325 km/s. The galaxies have been obtained in simulations with a considerable range of physical parameters, varying the baryonic fraction, the gas metallicity, the meta-galactic UV field, the cosmology, the dark matter type, and also the numerical resolution. The models are found to be in agreement with the (few) relevant X-ray observations available at present. The amount of hot gas in the haloes is also consistent with constraints from pulsar dispersion measures in the Milky Way. Forthcoming XMM and Chandra observations should enable much more stringent tests and provide constraints on the physical parameters. We find that simple cooling flow models over-predict X-ray luminosities by up to two orders of magnitude for high (but still realistic) cooling efficiencies relative to the models presented here. Our results display a clear trend that increasing cooling efficiency leads to decreasing X-ray luminosities at z=0. The reason is found to be that increased cooling efficiency leads to a decreased fraction of hot gas relative to total baryonic mass inside of the virial radius at present. At gas metal abundances of a third solar this hot gas fraction becomes as low as just a few percent. We also find that most of the X-ray emission comes from the inner parts (inner about 20 kpc) of the hot galactic haloes. Finally, we find for realistic choices of the physical parameters that disc galaxy haloes possibly were more than one order of magnitude brighter in soft X-ray emission at z=1, than at present.Comment: 8 pages, 7 figures, MNRAS LaTeX forma

Thirty-fold: Extreme gravitational lensing of a quiescent galaxy at z=1.6z=1.6

We report the discovery of eMACSJ1341-QG-1, a quiescent galaxy at $z=1.594$ located behind the massive galaxy cluster eMACSJ1341.9$-$2442 ($z=0.835$). The system was identified as a gravitationally lensed triple image in Hubble Space Telescope images obtained as part of a snapshot survey of the most X-ray luminous galaxy clusters at $z>0.5$ and spectroscopically confirmed in ground-based follow-up observations with the ESO/X-Shooter spectrograph. From the constraints provided by the triple image, we derive a first, crude model of the mass distribution of the cluster lens, which predicts a gravitational amplification of a factor of $\sim$30 for the primary image and a factor of $\sim$6 for the remaining two images of the source, making eMACSJ1341-QG-1 by far the most strongly amplified quiescent galaxy discovered to date. Our discovery underlines the power of SNAPshot observations of massive, X-ray selected galaxy clusters for lensing-assisted studies of faint background populations

Trace ideals for Fourier integral operators with non-smooth symbols II

We consider Fourier integral operators with symbols in modulation spaces and non-smooth phase functions whose second orders of derivatives belong to certain types of modulation space. We establish continuity and Schatten-von Neumann properties of such operators when acting on modulation spaces.Comment: 25 page

Discovery of an overdensity of faint red galaxies in the vicinity of the z=1.786 radio galaxy 3C 294

We report the discovery of an overdensity of faint red galaxies in the vicinity of the z=1.786 radio galaxy 3C 294. The overdensity, discovered in a 84 min Ks-band ISAAC/VLT image is significant at the 2.4 sigma level (compared to the local field density), and overlaps with the extended X-ray emission around 3C 294 detected with the Chandra X-ray Observatory. The near-infrared colours of the galaxies making up the overdensity show a large scatter and the galaxies do not follow a red sequence in the colour magnitude diagram. If the galaxies are in a cluster at z=1.786 they must be dominated by young stellar populations with different star-formation histories.Comment: Accepted for publication in MNRA

Distant red galaxies in the Hubble Ultra Deep Field

We take advantage of the Hubble Ultra Deep Field (UDF) data to study the restframe optical and ultra violet (UV) morphologies of the novel population of Distant Red Galaxies (DRGs). Six galaxies with J-Ks > 2.3 are found to Ks=21.5, five of which have photometric redshifts z_phot > 2, corresponding to a surface density of 0.9/arcmin^2. The surface brightness distributions of the z_phot > 2 galaxies are better represented by exponential disks than R^{1/4}-laws. Two of the z_phot > 2 galaxies are extended, while three have compact morphologies. The restframe optical morphology of the z_phot > 2 galaxies is quite different from the restframe UV morphology: all the galaxies have red central components which dominate in the NICMOS H_{160}-band images, and distinct off-center blue features which show up in (and often dominate) the ACS images. The mean measured effective radius of the z_phot > 2 galaxies is =1.9+/-1.4 kpc, similar (within the errors) to the mean size of LBGs at similar redshifts. All the DRGs are resolved in the ACS images, while four are resolved in the NICMOS images. Two of the z_phot > 2 galaxies are bright X-ray sources and hence host AGN. The diverse restframe optical and UV morphological properties of DRGs derived here suggest that they have complex stellar populations, consisting of both evolved populations that dominate the mass and the restframe optical light, and younger populations, which show up as patches of star formation in the restframe UV light; in many ways resembling the properties of normal local galaxies. This interpretation is supported by fits to the broadband SEDs, which for all five z_phot > 2 are best represented by models with extended star formation histories and substantial amounts of dust.Comment: Accepted for publication in APJ

Measuring Extinction Curves of Lensing Galaxies

We critique the method of constructing extinction curves of lensing galaxies using multiply imaged QSOs. If one of the two QSO images is lightly reddened or if the dust along both sightlines has the same properties then the method works well and produces an extinction curve for the lensing galaxy. These cases are likely rare and hard to confirm. However, if the dust along each sightline has different properties then the resulting curve is no longer a measurement of extinction. Instead, it is a measurement of the difference between two extinction curves. This "lens difference curve'' does contain information about the dust properties, but extracting a meaningful extinction curve is not possible without additional, currently unknown information. As a quantitative example, we show that the combination of two Cardelli, Clayton, & Mathis (CCM) type extinction curves having different values of R(V) will produce a CCM extinction curve with a value of R(V) which is dependent on the individual R(V) values and the ratio of V band extinctions. The resulting lens difference curve is not an average of the dust along the two sightlines. We find that lens difference curves with any value of R(V), even negative values, can be produced by a combination of two reddened sightlines with different CCM extinction curves with R(V) values consistent with Milky Way dust (2.1 < R(V) < 5.6). This may explain extreme values of R(V) inferred by this method in previous studies. But lens difference curves with more normal values of R(V) are just as likely to be composed of two dust extinction curves with R(V) values different than that of the lens difference curve. While it is not possible to determine the individual extinction curves making up a lens difference curve, there is information about a galaxy's dust contained in the lens difference curves.Comment: 15 pages, 4 figues, ApJ in pres

Sub-millimeter galaxies as progenitors of compact quiescent galaxies

Three billion years after the big bang (at redshift z=2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation and extremely compact with stellar mass densities at least an order of magnitude larger than in low redshift ellipticals, their descendants. Little is known about how they formed, but their evolved, dense stellar populations suggest formation within intense, compact starbursts 1-2 Gyr earlier (at 3<z<6). Simulations show that gas-rich major mergers can give rise to such starbursts which produce dense remnants. Sub-millimeter selected galaxies (SMGs) are prime examples of intense, gas-rich, starbursts. With a new, representative spectroscopic sample of compact quiescent galaxies at z=2 and a statistically well-understood sample of SMGs, we show that z=3-6 SMGs are consistent with being the progenitors of z=2 quiescent galaxies, matching their formation redshifts and their distributions of sizes, stellar masses and internal velocities. Assuming an evolutionary connection, their space densities also match if the mean duty cycle of SMG starbursts is 42 (+40/-29) Myr (consistent with independent estimates), which indicates that the bulk of stars in these massive galaxies were formed in a major, early surge of star-formation. These results suggests a coherent picture of the formation history of the most massive galaxies in the universe, from their initial burst of violent star-formation through their appearance as high stellar-density galaxy cores and to their ultimate fate as giant ellipticals.Comment: ApJ (in press