Huub Röttgering

A luminous quasar at a redshift of z = 7.085

The intergalactic medium was not completely reionized until approximately a billion years after the Big Bang, as revealed by observations of quasars with redshifts of less than 6.5. It has been difficult to probe to higher redshifts, however, because quasars have historically been identified in optical surveys, which are insensitive to sources at redshifts exceeding 6.5. Here we report observations of a quasar (ULAS J112001.48+064124.3) at a redshift of 7.085, which is 0.77 billion years after the Big Bang. ULAS J1120+0641 has a luminosity of 6.3 × 1013L⊙ and hosts a black hole with a mass of 2 × 109M⊙ (where L⊙ and M⊙ are the luminosity and mass of the Sun). The measured radius of the ionized near zone around ULAS J1120+0641 is 1.9 megaparsecs, a factor of three smaller than is typical for quasars at redshifts between 6.0 and 6.4. The near-zone transmission profile is consistent with a Lyα damping wing, suggesting that the neutral fraction of the intergalactic medium in front of ULAS J1120+0641 exceeded 0.1.

The size evolution of galaxies since z~3: combining SDSS, GEMS, and FIRES

We present the evolution of the luminosity-size and stellar mass-size relations of luminous ( L-V greater than or similar to 3.4 x 10(10) h(70)(-2) L-circle dot) and massive ( M-* greater than or similar to 3 x 10(10) h(70)(-2) M-circle dot) galaxies in the last similar to 11 Gyr. We use very deep near-infrared images of the Hubble Deep Field-South and the MS 1054-03 field in the J(s), H, and K-s bands from FIRES to retrieve the sizes in the optical rest frame for galaxies with z > 1. We combine our results with those from GEMS at 0.2 < z < 1 and SDSS at z similar to 0.1 to achieve a comprehensive picture of the optical rest-frame size evolution from z = 0 to 3. Galaxies are differentiated according to their light concentration using the Sersic index n. For less concentrated objects, the galaxies at a given luminosity were typically similar to 3 +/- 0.5 ( +/- 2 sigma) times smaller at z similar to 2: 5 than those we see today. The stellar mass-size relation has evolved less: the mean size at a given stellar mass was similar to 2 +/- 0.5 times smaller at z similar to 2.5, evolving proportionally to ( 1 + z) - 0.40 +/- 0.06. Simple scaling relations between dark matter halos and baryons in a hierarchical cosmogony predict a stronger ( although consistent within the error bars) than observed evolution of the stellar mass-size relation. The observed luminosity-size evolution out to z similar to 2.5 matches well recent infall model predictions for Milky Way-type objects. For low-n galaxies, the evolution of the stellar mass-size relation would follow naturally if the individual galaxies grow inside out. For highly concentrated objects, the situation is as follows: at a given luminosity, these galaxies were similar to 2.7 +/- 1.1 times smaller at z similar to 2.5 ( or, put differently, were typically similar to 2.2 +/- 0.7 mag brighter at a given size than they are today), and at a given stellar mass the size has evolved proportionally to ( 1 + z)(-0.45 +/- 0.10).

THE REST-FRAME OPTICAL LUMINOSITY DENSITY, COLOR, AND STELLAR MASS DENSITY OF THE UNIVERSE FROM z = 0 TO z = 3

We present the evolution of the rest-frame optical luminosity density j, the integrated rest-frame optical color, and the stellar mass density, ?*, for a sample of Ks band-selected galaxies in the Hubble Deep Field-South (HDF-S). We derived j in the rest-frame U, B, and V bands and found that j increases by a factor of 1.9 ? 0.4, 2.9 ? 0.6, and 4.9 ? 1.0 in the V, B, and U rest-frame bands, respectively, between redshifts of 0.1 and 3.2. We derived the luminosity-weighted mean cosmic (U-B)rest and (B-V)rest colors as a function of redshift. The colors bluen almost monotonically with increasing redshift; at z = 0.1, the (U-B)rest and (B-V)rest colors are 0.16 and 0.75, respectively, while at z = 2.8 they are -0.39 and 0.29, respectively. We derived the luminosity-weighted mean M/L, using the correlation between (U-V)rest and log M/L that exists for a range in smooth star formation histories (SFHs) and moderate extinctions. We have shown that the mean of individual M/L estimates can overpredict the true value by ~70%, while our method overpredicts the true value by only ~35%. We find that the universe at z ~ 3 had ~10 times lower stellar mass density than it does today in galaxies with L > 1.4 ? 1010 h L?. Half of the stellar mass of the universe was formed by z ~ 1-1.5. The rate of increase in ?* with decreasing redshift is similar to but above that for independent estimates from the HDF-N, but it is slightly less than that predicted by the integral of the SFR(z) curve.

What Do We Learn from IRAC Observations of Galaxies at 2 < z < 3.5?*

We analyze very deep HST, VLT, and Spitzer photometry of galaxies at 2 2 galaxies. The estimated distributions of these properties do not change significantly when IRAC data are added to the UBVIJHK photometry. However, for individual galaxies the addition of IRAC can improve the constraints on the stellar populations, especially for red galaxies: uncertainties in stellar mass decrease by a factor of 2.7 for red [(U − V)rest > 1] galaxies, but only by a factor of 1.3 for blue [(U − V)rest 2. The most massive galaxies at high redshift have red rest-frame U - V colors compared to lower mass galaxies, even when allowing for complex star formation histories.

Particle Acceleration on Megaparsec Scales in a Merging Galaxy Cluster

Shocking Radio Relic Radio relics are diffuse, elongated radio sources located on the outskirts of galaxy clusters thought to trace shocks generated by collisions between galaxy clusters. Particles may be accelerated within the shock waves by a diffusive shock acceleration mechanism, which also accelerates particles in shock waves produced by supernova explosions. Van Weeren et al. (p. 347, published online 23 September) report the detection of a megaparsec-scale radio relic showing all the properties of diffusive shock acceleration expected at radio wavelengths. The results suggest that this acceleration mechanism operates on scales larger than those of supernova remnants and imply that merging clusters of galaxies can accelerate particles to energies much higher than those achieved in supernova remnants Observations show that shocks within the intracluster medium are capable of producing extremely energetic cosmic rays. Galaxy clusters form through a sequence of mergers of smaller galaxy clusters and groups. Models of diffusive shock acceleration suggest that in shocks that occur during cluster mergers, particles are accelerated to relativistic energies, similar to conditions within supernova remnants. In the presence of magnetic fields, these particles emit synchrotron radiation and may form so-called radio relics. We detected a radio relic that displays highly aligned magnetic fields, a strong spectral index gradient, and a narrow relic width, giving a measure of the magnetic field in an unexplored site of the universe. Our observations show that diffusive shock acceleration also operates on scales much larger than in supernova remnants and that shocks in galaxy clusters are capable of producing extremely energetic cosmic rays.

IRAC Mid-Infrared Imaging of the Hubble Deep Field-South: Star Formation Histories and Stellar Masses of Red Galaxies at z > 2

We present deep 3.6–8 mm imaging of the Hubble Deep Field–South with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We study distant red galaxies (DRGs) at z 1 2 selected by JsKs 1 2.3 and compare them with a sample of Lyman break galaxies (LBGs) at z p 2–3. The observed UV–to–8 mm spectral energy distributions are fitted with stellar population models to constrain star formation histories and derive stellar masses. We find that 70% of the DRGs are best described by dust-reddened star-forming models and 30% are very well fitted with old and “dead” models. Using only the IKs and Ks4.5 mm colors, we can effectively separate the two groups. The dead systems are among the most massive at z ∼ 2.5 (mean stellar mass AM * S p 0.8 #10 11 M,) and likely formed most of their stellar mass at z 1 5. To a limit of 0.5 #10 11 M,, their number density is ∼10 times lower than that of local early-type galaxies. Furthermore, we use the IRAC photometry to derive rest-frame near-infrared J, H, and K fluxes. The DRGs and LBGs together show a large variation (a factor of 6) in the rest-frame K-band mass-to-light ratios (M/LK), implying that even a Spitzer 8 mm–selected sample would be very different from a mass-selected sample. The average M/LK of the DRGs is about 3 times higher than that of the LBGs, and DRGs dominate the high-mass end. The M/LK values and ages of the two samples appear to correlate with derived stellar mass, with the most massive galaxies being the oldest and having the highest mass-to-light ratios, similar to what is found in the low-redshift universe. Subject headings: galaxies: evolution — galaxies: high-redshift — infrared: galaxies

Ultradeep Near-Infrared ISAAC Observations of the Hubble Deep Field South: Observations, Reduction, Multicolor Catalog, and Photometric Redshifts

We present deep near-infrared (NIR) Js-, H-, and Ks-band ISAAC imaging of the Wide Field Planetary Camera 2 (WFPC2) field of the Hubble Deep Field South (HDF-S). The 25 × 25 high Galactic latitude field was observed with the Very Large Telescope under the best seeing conditions, with integration times amounting to 33.6 hr in Js, 32.3 hr in H, and 35.6 hr in Ks. We reach total AB magnitudes for point sources of 26.8, 26.2, and 26.2, respectively (3 σ), which make it the deepest ground-based NIR observation to date and the deepest Ks-band data in any field. The effective seeing of the co-added images is ≈045 in Js, ≈048 in H, and ≈046 in Ks. Using published WFPC2 optical data, we constructed a Ks-limited multicolor catalog containing 833 sources down to K 26, of which 624 have seven-band optical-to-NIR photometry. These data allow us to select normal galaxies from their rest-frame optical properties to high redshift (z 4). The observations, data reduction, and properties of the final images are discussed, and we address the detection and photometry procedures that were used in making the catalog. In addition, we present deep number counts, color distributions, and photometric redshifts of the HDF-S galaxies. We find that our faint Ks-band number counts are flatter than published counts in other deep fields, which might reflect cosmic variations or different analysis techniques. Compared to the HDF-N, we find many galaxies with very red V-H colors at photometric redshifts 1.95 2.3 (in Johnson magnitudes). Because they are extremely faint in the observed optical, they would be missed by ultraviolet–optical selection techniques, such as the U-dropout method.

EMU: Evolutionary Map of the Universe

EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The primary goal of EMU is to make a deep (rms ~10 μJy/beam) radio continuum survey of the entire Southern sky at 1.3 GHz, extending as far North as +30° declination, with a resolution of 10 arcsec. EMU is expected to detect and catalogue about 70 million galaxies, including typical star-forming galaxies up to z ~ 1, powerful starbursts to even greater redshifts, and active galactic nuclei to the edge of the visible Universe. It will undoubtedly discover new classes of object. This paper defines the science goals and parameters of the survey, and describes the development of techniques necessary to maximise the science return from EMU.

Resolving the obscuring torus in NGC 1068 with the power of infrared interferometry: Revealing the inner funnel of dust

We present new interferometric data obtained with MIDI (MID infrared Interferometric instrument) for the Seyfert II galaxy NGC 1068, with an extensive coverage of sixteen uv points. These observations resolve the nuclear mid-infrared emission from NGC 1068 in unprecedented detail with a maximum resolution of 7 mas. For the first time, suffi cient uv points have been obtained, allowing us to generate an image of the source using maximum entropy image reconstruction. The features of the image are similar to tho se obtained by modelling. We find that the mid-infrared emission can be represented by two components, each with a Gaussian brightness distribution. The first, identified as the inner f unnel of the obscuring torus, is hot (∼800K), 1.35 parsec long, and 0.45 parsec thick in FWHM at a PA=−42 ◦ (from north to east). It has an absorption profile di fferent than standard interstellar dust and with evidence for clumpiness. The second component is 3× 4 pc in FWHM with T=∼300K, and we identify it with the cooler body of the torus. The compact component is tilted by∼ 45 ◦ with respect to the radio jet and has similar size and orientation to the obse rved water maser distribution. We show how the dust distribution relates to other observables within a few parsecs of the core of the galaxy such as the nuclear masers, the radio jet, and the i onization cone. We compare our findings to a similar study of the Circinus galaxy and other re levant studies. Our findings shed new light on the relation between the different parsec-scale components in NGC 1068 and the obscuring torus.

Radio Continuum Imaging of High-redshift Radio Galaxies

We present sensitive radio continuum observations at high resolution of 37 radio galaxies at z > 2. The observations were made with the Very Large Array (VLA) at 4.7 and 8.2 GHz, with typical resolutions of 045 and 025, respectively. Images of total and polarized intensity, and spectral index, are presented. Values for total and polarized intensity, and values of rotation measures, are tabulated for the hot spots in each source. The positions of the radio nuclei are tabulated along with a variety of other source parameters. Analysis of the polarization data reveals large rotation measures (RMs) towards seven sources. We argue that the RMs are due to magnetized, ionized gas local to the radio sources. The magnitude of the RMs are in excess of 1000 rad m-2 (rest frame) for these sources. Drawing an analogy to a class of lower redshift radio galaxies with extreme RMs, we speculate that these sources may be at the centers of dense X-ray emitting cluster atmospheres.