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The existence of massive (1011solar masses) elliptical galaxies by redshift z ≈ 4 (refs 1, 2, 3; when the Universe was 1.5 billion years old) necessitates the presence of galaxies with star-formation rates exceeding 100 solar masses per year at z > 6 (corresponding to an age of the Universe of less than 1 billion years). Surveys have discovered hundreds of galaxies at these early cosmic epochs, but their star-formation rates are more than an order of magnitude lower. The only known galaxies with very high star-formation rates at z > 6 are, with one exception, the host galaxies of quasars, but these galaxies also host accreting supermassive (more than 109solar masses) black holes, which probably affect the properties of the galaxies. Here we report observations of an emission line of singly ionized carbon ([C ii] at a wavelength of 158 micrometres) in four galaxies at z > 6 that are companions of quasars, with velocity offsets of less than 600 kilometres per second and linear offsets of less than 100 kiloparsecs. The discovery of these four galaxies was serendipitous; they are close to their companion quasars and appear bright in the far-infrared. On the basis of the [C ii] measurements, we estimate star-formation rates in the companions of more than 100 solar masses per year. These sources are similar to the host galaxies of the quasars in [C ii] brightness, linewidth and implied dynamical mass, but do not show evidence for accreting supermassive black holes. Similar systems have previously been found at lower redshift. We find such close companions in four out of the twenty-five z > 6 quasars surveyed, a fraction that needs to be accounted for in simulations. If they are representative of the bright end of the [C ii] luminosity function, then they can account for the population of massive elliptical galaxies at z ≈ 4 in terms of the density of cosmic space.

The Near-Infrared Spectrograph (NIRSpec) is one of the four focal plane instruments on the James Webb Space Telescope. In this paper, we summarize the in-orbit performance of NIRSpec, as derived from data collected during its commissioning campaign and the first few months of nominal science operations. More specifically, we discuss the performance of some critical hardware components such as the two NIRSpec Hawaii-2RG detectors, wheel mechanisms, and the microshutter array. We also summarize the accuracy of the two target acquisition procedures used to accurately place science targets into the slit apertures, discuss the current status of the spectrophotometric and wavelength calibration of NIRSpec spectra, and provide the “as measured” sensitivity in all NIRSpec science modes. Finally, we point out a few important considerations for the preparation of NIRSpec science programs.

Aims.To test the dust torus model for active galactic nuclei directly, we study the extent and morphology of the nuclear dust distribution in the Circinus galaxyusing high resolution interferometric observations in the mid-infrared.

We present mass estimates for dark matter halos around galaxies from the COMBO-17 survey using weak gravitational lensing. COMBO-17, with photometry in 17 optical filters, provides precise photometric redshifts and spectral classification for objects with $R<24$. This permits to select and sort lens and source galaxies by their redshifts and lens luminosity or color, which bypasses many uncertainties in other weak lensing analyses arising from broadly estimated source and lens redshifts. We study the shear created by dark matter halos around 12 000 galaxy lenses at redshifts $z_\mathrm{d}=0.2{-}0.7$by fitting the mass normalization of either singular isothermal spheres (SIS) or Navarro-Frenk-White (NFW) profiles to background source orientations around the whole lens sample. We also consider halos around blue and red subsamples separately and constrain the scaling of halo mass with light. For the NFW model, we find virial masses $M_\mathrm{vir}^*=3.9\times 10^{11}h^{-1}~M_{\odot}$for blue and $M_\mathrm{vir}^*=7.1\times 10^{11}h^{-1}~M_{\odot}$for red galaxies of $L_\star=10^{10}h^{-2}~L_{\odot}$, respectively. The 1-σuncertainty on $\log M_\mathrm{vir}^*$for the whole lens sample is about 0.2. We compare our results to those obtained from the Red-Sequence Cluster Survey (RCS) and the Sloan Digital Sky Survey (SDSS). Taking differences in the actual modelling into account, we find very good agreement with these surveys.

We present an analysis of stellar mass estimates for a sample of 25000 galaxies from the COMBO-17 survey over the interval $0.2 < z < 1.0$. We have developed, implemented, and tested a new method of estimating stellar mass-to-light ratios, which relies on redshift and spectral energy distribution (SED) classification from 5 broadband and 12 medium band filters. We find that the majority (>$60\%$) of massive galaxies with $M_* > 10^{11} M_{\odot}$at all $z < 1$are non-star-forming; blue star-forming galaxies dominate at lower masses. We have used these mass estimates to explore the evolution of the stellar mass function since $z =1$. We find that the total stellar mass density of the universe has roughly doubled since $z \sim 1$. Our measurements are consistent with other measurements of the growth of stellar mass with cosmic time and with estimates of the time evolution of the cosmic star formation rate. Intriguingly, the integrated stellar mass of blue galaxies with young stars has not significantly changed since $z \sim 1$, even though these galaxies host the majority of the star formation: instead, the growth of the total stellar mass density is dominated by the growth of the total mass in the largely passive galaxies on the red sequence.

We investigate how galaxy-galaxy lensing measurements depend on the knowledge of redshifts for lens and source galaxies. Galaxy-galaxy lensing allows one to study dark matter halos of galaxies statistically using weak gravitational lensing. Redshift information is required to reliably distinguish foreground lens galaxies from background source galaxies and to convert the measured shear into constraints on the lens model. Without spectroscopy or multi-colour information, redshifts can be drawn from independently estimated probability distributions. The COMBO-17 survey provides redshifts for both lens and source galaxies. It thus offers the unique possibility to do this investigation with observational data. We find that it is of great importance to know the redshifts of individual lens galaxies in order to constrain the properties of their dark matter halos. Whether the redshifts are derived from ${\it UBVRI}$or the larger number of filters available in COMBO-17 is not very important. In contrast, knowledge of individual source redshifts improves the measurements only very little over the use of statistical source redshift distributions as long as the source redshift distribution is known accurately.

We present the COMBO-17 object catalogue of the Chandra Deep Field South for public use, covering a field which is $31\farcm5$$\times$$30\arcmin$in size. This catalogue lists astrometry, photometry in 17 passbands from 350 to 930 nm, and ground-based morphological data for 63 501 objects. The catalogue also contains multi-colour classification into the categories Star, Galaxyand Quasaras well as photometric redshifts. We include restframe luminosities in Johnson, SDSS and Bessell passbands and estimated errors. The redshifts are most reliable at $R<24$, where the sample contains approximately 100 quasars, 1000 stars and 10 000 galaxies. We use nearly 1000 spectroscopically identified objects in conjunction with detailed simulations to characterize the performance of COMBO-17. We show that the selection of quasars, more generally type-1 AGN, is nearly complete and minimally contaminated at $z=[0.5,5]$for luminosities above MB= -21.7. Their photometric redshifts are accurate to roughly 5000 km s-1. Galaxy redshifts are accurate to 1% in $\delta_z/(1+z)$at $R<21$. They degrade in quality for progressively fainter galaxies, reaching accuracies of 2% for galaxies with $R \sim 22$and of 10% for galaxies with $R>24$. The selection of stars is complete to $R \sim 23$, and deeper for M stars. We also present an updated discussion of our classification technique with maps of survey completeness, and discuss possible failures of the statistical classification in the faint regime at $R\ga 24$.

We present $J-H-K'$photometry for a sample of 45 high redshift quasars found by the Sloan Digital Sky Survey. The sample was originally selected on the basis of optical colors and spans a redshift range from 3.6 to 5.03. Our photometry reflects the rest-frame SED longward of Lyafor all redshifts. The results show that the near-IR colors of high redshift quasars are quite uniform. We have modelled the continuum shape of the quasars (from just beyond to ~4000 Å) with a power law of the form $f_\nu \propto \nu^\alpha$, and find $\langle \alpha \rangle =-0.57$with a scatter of 0.33. This value is similar to what is found for lower redshift quasars over the same restframe wavelength range, and we conclude that there is hardly any evolution in the continuum properties of optically selected quasars up to redshift 5. The spectral indices found by combining near-IR with optical photometry are in general consistent but slightly flatter than what is found for the same quasars using the optical spectra and photometry alone, showing that the continuum region used to determine the spectral indices can somewhat influence the results.

We report on deep multi-color imaging ($R_{5\sigma} = 26$) of the Chandra Deep Field South, obtained with the Wide Field Imager (WFI) at the MPG/ESO 2.2 m telescope on La Silla as part of the multi-color survey COMBO-17. As a result we present a catalogue of 63 501 objects in a field measuring $31\farcm5 \times 30\arcmin$with astrometry and BVRphotometry. A sample of 37 variable objects is selected from two-epoch photometry. We try to give interpretations based on color and variation amplitude.

We present the B-band luminosity function and comoving space and luminosity densities for a sample of 2779 I-band selected field galaxies based on multi-color data from the CADIS survey. The sample is complete down to $I_{815} = 22$without correction and with completeness correction extends to $I_{815}=23.0$. By means of a new multi-color analysis the objects are classified according to their spectral energy distributions (SEDs) and their redshifts are determined with typical errors of $\delta z \le 0.03$. We have split our sample into four redshift bins between $z=0.1$and $z=1.04$and into three SED bins E-Sa, Sa-Sc and starbursting (emission line) galaxies. The evolution of the luminosity function is clearly differential with SED. The normalization $\phi^*$of the luminosity function for the E-Sa galaxies decreases towards higher redshift, and we find evidence that the comoving galaxy space density decreases with redshift as well. In contrast, we find $\phi^*$and the comoving space density increasing with redshift for the Sa-Sc galaxies. For the starburst galaxies we find a steepening of the luminosity function at the faint end and their comoving space density increases with redshift.

We use a multi-color classification method introduced by Wolf et al. ([CITE]) to reliably identify stars, galaxies and quasars in the up to 16-dimensional color space provided by the filter set of the Calar Alto Deep Imaging Survey (CADIS). The samples of stars, galaxies and quasars obtained this way have been used for dedicated studies which are published in separate papers. The classification is good enough to detect quasars rather completely and efficiently without confirmative spectroscopy. The multi-color redshifts are accurate enough for most statistical applications, e.g. evolutionary studies of the galaxy luminosity function. Also, the separation between stars and galaxies reaches deeper than with morphological criteria, so that studies of the stellar population can be extended to fainter levels. We characterize the dataset presently available on the CADIS 1 h-, 9 h- and 16 h-fields. Using Monte-Carlo simulations we model the classification performance expected for CADIS. We present a summary of the classification results on the CADIS database and discuss unclassified objects. More than 99% of the whole catalog sample at $R< 22$(more than 95% at $R< 23$) are successfully classified matching the expectations derived from the simulations. A small number of peculiar objects challenging the classification is discussed in detail. Spectroscopic observations are used to check the reliability of the multi-color classification (6 mistakes among 151 objects with $R< 24$). From these, we also determine the accuracy of the multi-color redshifts which are rather good for galaxies ($\sigma_z \approx 0.03$) and useful for quasars. We find that the classification performance derived from the simulations compares well with results from the real survey. Finally, we locate areas for potential improvement of the classification.

The KINGFISH project (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel) is an imaging and spectroscopic survey of 61 nearby (d< 30 Mpc) galaxies, chosen to cover a wide range of galaxy properties and local interstellar medium (ISM) environments found in the nearby universe. Its broad goals are to characterize the ISM of present-day galaxies, the heating and cooling of their gaseous and dust components, and to better understand the physical processes linking star formation and the ISM. KINGFISH is a direct descendant of the SpitzerInfrared Nearby Galaxies Survey (SINGS), which produced complete Spitzerimaging and spectroscopic mapping and a comprehensive set of multiwavelength ancillary observations for the sample. The Herschelimaging consists of complete maps for the galaxies at 70, 100, 160, 250, 350, and 500 ?m. The spectral line imaging of the principal atomic ISM cooling lines ([O I] 63 ?m, [O III] 88 ?m, [N II] 122,205 ?m, and [C II] 158 ?m) covers the subregions in the centers and disks that already have been mapped in the mid-infrared with Spitzer. The KINGFISH and SINGS multiwavelength data sets combined provide panchromatic mapping of the galaxies sufficient to resolve individual star-forming regions, and tracing the important heating and cooling channels of the ISM, across a wide range of local extragalactic ISM environments. This article summarizes the scientific strategy for KINGFISH, the properties of the galaxy sample, the observing strategy, and data processing and products. It also presents a combined Spitzerand Herschelimage atlas for the KINGFISH galaxies, covering the wavelength range 3.6-500 ?m. All imaging and spectroscopy data products will be released to the Herscheluser-generated product archives.

We report on a program to obtain Hubble Space Telescope(HST) observations of galaxy-mass gravitational lens systems at optical and infrared wavelengths. Here we discuss the properties of 10 two-image gravitational lens systems (Q0142-100 = UM 673, B0218+357, SBS 0909+532, BRI 0952-0115, LBQS 1009-0252, Q1017-207 = J03.13, B1030+074, HE 1104-1805, Q1208+1011, and PKS 1830-211). We grouped these 10 systems because they have limited lens model constraints and often show poor contrast between the images and the lens galaxy. Of the 10 lens galaxies, seven are probably early-type galaxies, two are probably late-type galaxies (B0218+357 and PKS 1830-211), and one was not detected (Q1208+1011). We detect the host galaxies of the zs= 4.50 lensed quasar in BRI 0952-0115, the zs= 2.32 lensed quasar in HE 1104-1805, and the unlensed z= 1.63 quasar near LBQS 1009-0252. We fit a set of four standard lens models to each lens that had sufficient constraints to compare isothermal dark matter and constant mass-to-light lens models, and to explore the effects of local tidal shears.

We describe the goals of the CASTLES (CfA-Arizona-Space-Telescope-LEns-Survey) project including a sample of NICMOS images of gravitational lenses and a brief list of the preliminary findings.

Context.Current instrument developments at the largest telescopes worldwide involve the installation of multi-conjugated adaptive optics (MCAO) modules. The large field of view and more uniform correction provided by these systems is not only highly beneficial for photometric studies but also for astrometric analysis of, e.g., large dense clusters and exoplanet detection and characterization. The Multi-conjugated Adaptive optics Demonstrator (MAD) is the first such instrument and was temporarily installed and tested at the ESO/VLT in 2007.

We present Herschelfar-infrared (FIR) observations of two sub-mm bright quasars at high redshift: SDSS J1148+5251 (z= 6.42) and BR 1202–0725 (z= 4.69) obtained with the PACS instrument. Both objects are detected in the PACS photometric bands. The Herschelmeasurements provide additional data points that constrain the FIR spectral energy distributions (SEDs) of both sources, and they emphasise a broad range of dust temperatures in these objects. For λrest≲ 20 μm, the two SEDs are very similar to the average SEDs of quasars at low redshift. In the FIR, however, both quasars show excess emission compared to low-zQSO templates, most likely from cold dust powered by vigorous star formation in the QSO host galaxies. For SDSS J1148+5251 we detect another object at 160 μm with a distance of ~10´´ from the QSO. Although no physical connection between the quasar and this object can be shown with the available data, it could potentially confuse low-resolution measurements, thus resulting in an overestimate of the FIR luminosity of the z= 6.42 quasar.

Stellar density and bar strength should affect the temperatures of the cool (T~ 20–30 K) dust component in the inner regions of galaxies, which implies that the ratio of temperatures in the circumnuclear regions to the disk should depend on Hubble type. We investigate the differences between cool dust temperatures in the central 3 kpc and disk of 13 nearby galaxies by fitting models to measurements between 70 and 500 μm. We attempt to quantify temperature trends in nearby disk galaxies, with archival data from Spitzer/MIPS and new observations with Herschel/SPIRE, which were acquired during the first phases of the Herschelobservations for the KINGFISH (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel) sample. We fit single-temperature modified blackbodies to far-infrared and submillimeter measurements of the central and disk regions of galaxies to determine the temperature of the component(s) emitting at those wavelengths. We present the ratio of central-region-to-disk-temperatures of the cool dust component of 13 nearby galaxies as a function of morphological type. We find a significant temperature gradient in the cool dust component in all galaxies, with a mean center-to-disk temperature ratio of 1.15 ±0.03. The cool dust temperatures in the central ~3 kpc of nearby galaxies are 23 (±3)% hotter for morphological types earlier than Sc, and only 9 (±3)% hotter for later types. The temperature ratio is also correlated with bar strength, with only strongly barred galaxies having a ratio over 1.2. The strong radiation field in the high stellar density of a galactic bulge tends to heat the cool dust component to higher temperatures, at least in early-type spirals with relatively large bulges, especially when paired with a strong bar.

NGC 1097 is a nearby SBb galaxy with a Seyfert nucleus and a bright starburst ring. We study the physical properties of the interstellar medium (ISM) in the ring using spatially resolved far-infrared spectral maps of the circumnuclear starburst ring of NGC 1097, obtained with the PACS spectrometer on board the HerschelSpace Observatory. In particular, we map the important ISM cooling and diagnostic emission lines of [OI] 63 μm, [OIII] 88 μm, [NII] 122 μm, [CII] 158 μm and [NII] 205 μm. We observe that in the [OI] 63 μm, [OIII] 88 μm, and [NII] 122 μm line maps, the emission is enhanced in clumps along the NE part of the ring. We observe evidence of rapid rotation in the circumnuclear ring, with a rotation velocity of ~220 km s-1(inclination uncorrected) measured in all lines. The [OI] 63 μm/[CII] 158 μm ratio varies smoothly throughout the central region, and is enhanced on the northeastern part of the ring, which may indicate a stronger radiation field. This enhancement coincides with peaks in the [OI] 63 μm and [OIII] 88 μm maps. Variations of the [NII] 122 μm/[NII] 205 μm ratio correspond to a range in the ionized gas density between 150 and 400 cm-3.

Using photometry of NGC 1097 from the HerschelPACS (Photodetector Array Camera and Spectrometer) instrument, we study the resolved properties of thermal dust continuum emission from a circumnuclear starburst ring with a radius ~900 pc. These observations are the first to resolve the structure of a circumnuclear ring at wavelengths that probe the peak (i.e. λ~ 100 μm) of the dust spectral energy distribution. The ring dominates the far-infrared (far-IR) emission from the galaxy – the high angular resolution of PACS allows us to isolate the ring's contribution and we find it is responsible for 75, 60 and 55% of the total flux of NGC 1097 at 70, 100 and 160 μm, respectively. We compare the far-IR structure of the ring to what is seen at other wavelengths and identify a sequence of far-IR bright knots that correspond to those seen in radio and mid-IR images. The mid- and far-IR band ratios in the ring vary by less than ±20% azimuthally, indicating modest variation in the radiation field heating the dust on ~600 pc scales. We explore various explanations for the azimuthal uniformity in the far-IR colors of the ring including a lack of well-defined age gradients in the young stellar cluster population, a dominant contribution to the far-IR emission from dust heated by older (>10 Myr) stars and/or a quick smoothing of local enhancements in dust temperature due to the short orbital period of the ring. Finally, we improve previous limits on the far-IR flux from the inner ~600 pc of NGC 1097 by an order of magnitude, providing a better estimate of the total bolometric emission arising from the active galactic nucleus and its associated central starburst.

NGC 1097 is a nearby SBb galaxy with a Seyfert nucleus and a bright starburst ring. We study the physical properties of the interstellar medium (ISM) in the ring using spatially resolved far-infrared spectral maps of the circumnuclear starburst ring of NGC 1097, obtained with the PACS spectrometer on board the HerschelSpace Observatory. In particular, we map the important ISM cooling and diagnostic emission lines of [OI] 63 μm, [OIII] 88 μm, [NII] 122 μm, [CII] 158 μm and [NII] 205 μm. We observe that in the [OI] 63 μm, [OIII] 88 μm, and [NII] 122 μm line maps, the emission is enhanced in clumps along the NE part of the ring. We observe evidence of rapid rotation in the circumnuclear ring, with a rotation velocity of ~220 km s-1(inclination uncorrected) measured in all lines. The [OI] 63 μm/[CII] 158 μm ratio varies smoothly throughout the central region, and is enhanced on the northeastern part of the ring, which may indicate a stronger radiation field. This enhancement coincides with peaks in the [OI] 63 μm and [OIII] 88 μm maps. Variations of the [NII] 122 μm/[NII] 205 μm ratio correspond to a range in the ionized gas density between 150 and 400 cm-3.

Using photometry of NGC 1097 from the HerschelPACS (Photodetector Array Camera and Spectrometer) instrument, we study the resolved properties of thermal dust continuum emission from a circumnuclear starburst ring with a radius ~900 pc. These observations are the first to resolve the structure of a circumnuclear ring at wavelengths that probe the peak (i.e. λ~ 100 μm) of the dust spectral energy distribution. The ring dominates the far-infrared (far-IR) emission from the galaxy – the high angular resolution of PACS allows us to isolate the ring's contribution and we find it is responsible for 75, 60 and 55% of the total flux of NGC 1097 at 70, 100 and 160 μm, respectively. We compare the far-IR structure of the ring to what is seen at other wavelengths and identify a sequence of far-IR bright knots that correspond to those seen in radio and mid-IR images. The mid- and far-IR band ratios in the ring vary by less than ±20% azimuthally, indicating modest variation in the radiation field heating the dust on ~600 pc scales. We explore various explanations for the azimuthal uniformity in the far-IR colors of the ring including a lack of well-defined age gradients in the young stellar cluster population, a dominant contribution to the far-IR emission from dust heated by older (>10 Myr) stars and/or a quick smoothing of local enhancements in dust temperature due to the short orbital period of the ring. Finally, we improve previous limits on the far-IR flux from the inner ~600 pc of NGC 1097 by an order of magnitude, providing a better estimate of the total bolometric emission arising from the active galactic nucleus and its associated central starburst.

We present Herschelfar-infrared (FIR) observations of two sub-mm bright quasars at high redshift: SDSS J1148+5251 (z= 6.42) and BR 1202–0725 (z= 4.69) obtained with the PACS instrument. Both objects are detected in the PACS photometric bands. The Herschelmeasurements provide additional data points that constrain the FIR spectral energy distributions (SEDs) of both sources, and they emphasise a broad range of dust temperatures in these objects. For λrest≲ 20 μm, the two SEDs are very similar to the average SEDs of quasars at low redshift. In the FIR, however, both quasars show excess emission compared to low-zQSO templates, most likely from cold dust powered by vigorous star formation in the QSO host galaxies. For SDSS J1148+5251 we detect another object at 160 μm with a distance of ~10´´ from the QSO. Although no physical connection between the quasar and this object can be shown with the available data, it could potentially confuse low-resolution measurements, thus resulting in an overestimate of the FIR luminosity of the z= 6.42 quasar.

Stellar density and bar strength should affect the temperatures of the cool (T~ 20–30 K) dust component in the inner regions of galaxies, which implies that the ratio of temperatures in the circumnuclear regions to the disk should depend on Hubble type. We investigate the differences between cool dust temperatures in the central 3 kpc and disk of 13 nearby galaxies by fitting models to measurements between 70 and 500 μm. We attempt to quantify temperature trends in nearby disk galaxies, with archival data from Spitzer/MIPS and new observations with Herschel/SPIRE, which were acquired during the first phases of the Herschelobservations for the KINGFISH (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel) sample. We fit single-temperature modified blackbodies to far-infrared and submillimeter measurements of the central and disk regions of galaxies to determine the temperature of the component(s) emitting at those wavelengths. We present the ratio of central-region-to-disk-temperatures of the cool dust component of 13 nearby galaxies as a function of morphological type. We find a significant temperature gradient in the cool dust component in all galaxies, with a mean center-to-disk temperature ratio of 1.15 ±0.03. The cool dust temperatures in the central ~3 kpc of nearby galaxies are 23 (±3)% hotter for morphological types earlier than Sc, and only 9 (±3)% hotter for later types. The temperature ratio is also correlated with bar strength, with only strongly barred galaxies having a ratio over 1.2. The strong radiation field in the high stellar density of a galactic bulge tends to heat the cool dust component to higher temperatures, at least in early-type spirals with relatively large bulges, especially when paired with a strong bar.