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Results from a large, multi-J CO, {13}CO, and HCN line survey of Luminous Infrared Galaxies (L_{IR}>=10^{10} L_{\odot}) in the local Universe (z<=0.1), complemented by CO J=4--3 up to J=13--12 observations from the Herschel Space Observatory (HSO), paints a new picture for the average conditions of the molecular gas of the most luminous of these galaxies with turbulence and/or large cosmic ray (CR) energy densities U_{CR} rather than far-UV/optical photons from star-forming sites as the dominant heating sources. Especially in ULIRGs (L_{IR}>10^{12} L_{\odot}) the Photon Dominated Regions (PDRs) can encompass at most \sim few% of their molecular gas mass while the large U_{CR} and the strong turbulence in these merger/starbursts, can volumetrically heat much of their molecular gas to T_{kin}\sim(100-200)K, unhindered by the high dust extinctions. Moreover the strong supersonic turbulence in ULIRGs relocates much of their molecular gas at much higher average densities than in isolated spirals. This renders low-J CO lines incapable of constraining the properties of the bulk of the molecular gas in ULIRGs, with substantial and systematic underestimates of its mass possible when only such lines are used. A comparative study of multi-J HCN lines and CO SLEDs from J=1--0 up to J=13--12 of NGC 6240 and Arp 193 offers a clear example of two merger/starbursts whose similar low-J CO SLEDs, and L_{IR}/L_{CO,1-0}, L_{HCN, 1-0}/L_{CO,1-0} ratios, yield no indications about their strongly diverging CO SLEDs beyond J=4--3, and ultimately the different physical conditions in their molecular ISM. The much larger sensitivity of ALMA and its excellent site in the Atacama desert now allows the observations necessary to ...., Comment: 6 pages, 5 figures, invited talk at the IAU Symposium No 292, Beijing, China, 2013

We report the first counts of faint submillimetre galaxies (SMG) in the 870-um band derived from arcsecond resolution observations with the Atacama Large Millimeter Array (ALMA). We have used ALMA to map a sample of 122 870-um-selected submillimetre sources drawn from the (0.5x0.5)deg^2 LABOCA Extended Chandra Deep Field South Submillimetre Survey (LESS). These ALMA maps have an average depth of sigma(870um)~0.4mJy, some ~3x deeper than the original LABOCA survey and critically the angular resolution is more than an order of magnitude higher, FWHM of ~1.5" compared to ~19" for the LABOCA discovery map. This combination of sensitivity and resolution allows us to precisely pin-point the SMGs contributing to the submillimetre sources from the LABOCA map, free from the effects of confusion. We show that our ALMA-derived SMG counts broadly agree with the submillimetre source counts from previous, lower-resolution single-dish surveys, demonstrating that the bulk of the submillimetre sources are not caused by blending of unresolved SMGs. The difficulty which well-constrained theoretical models have in reproducing the high-surface densities of SMGs, thus remains. However, our observations do show that all of the very brightest sources in the LESS sample, S(870um)>12mJy, comprise emission from multiple, fainter SMGs, each with 870-um fluxes of <9mJy. This implies a natural limit to the star-formation rate in SMGs of <10^3 M_Sun/yr, which in turn suggests that the space densities of z>1 galaxies with gas masses in excess of ~5x10^10 M_Sun is <10^-5 Mpc^-3. We also discuss the influence of this blending on the identification and characterisation of the SMG counterparts to these bright submillimetre sources and suggest that it may be responsible for previous claims that they lie at higher redshifts than fainter SMGs., Comment: 9 pages, 3 figures, 2 tables; revised to match version accepted for publication in MNRAS

We propose a co-ordinated multi-observatory survey at the North Ecliptic Pole. This field is the natural extragalactic deep field location for most space observatories (e.g. containing the deepest Planck, WISE and eROSITA data), is in the continuous viewing zones for e.g. Herschel, HST, JWST, and is a natural high-visibility field for the L2 halo orbit of SPICA with deep and wide-field legacy surveys already planned. The field is also a likely deep survey location for the forthcoming Euclid mission. It is already a multi-wavelength legacy field in its own right (e.g. AKARI, LOFAR, SCUBA-2): the outstanding and unparalleled continuous mid-IR photometric coverage in this field and nowhere else enables a wide range of galaxy evolution diagnostics unachievable in any other survey field, by spanning the wavelengths of redshifted PAH and silicate features and the peak energy output of AGN hot dust. We argue from the science needs of Euclid and JWST, and from the comparative multiwavelength depths, that the logical approach is (1) a deep (H-UDF) UV/optical tile in the NEP over ~10 square arcminutes, and (2) an overlapping wide-field UV/optical HST survey tier covering >100 square arcminutes, with co-ordinated submm SPIRE mapping up to or beyond the submm point source confusion limit over a wider area and PACS data over the shallower HST tier., Comment: White paper submitted to the HST / Herschel Deep Fields working group. CANDELS reference added

We present ALMA 870-um (345GHz) observations of two sub-millimetre galaxies (SMGs) drawn from an ALMA study of the 126 sub-millimeter sources from the LABOCA Extended Chandra Deep Field South Survey (LESS). The ALMA data identify the counterparts to these previously unidentified sub-millimeter sources and serendipitously detect bright emission lines in their spectra which we show are most likely to be [C II]157.74um emission yielding redshifts of z=4.42 and z=4.44. This blind detection rate within the 7.5-GHz bandpass of ALMA is consistent with the previously derived photometric redshift distribution of SMGs and suggests a modest, but not dominant (<25%), tail of 870-um selected SMGs at z>4. We find that the ratio of L_CII/L_FIR in these SMGs is much higher than seen for similarly far-infrared-luminous galaxies at z~0, which is attributed to the more extended gas reservoirs in these high-redshift ULIRGs. Indeed, in one system we show that the [C II] emission shows hints of extended emission on >3kpc scales. Finally, we use the volume probed by our ALMA survey to show that the bright end of the [C II] luminosity function evolves strongly between z=0 and z~4.4, reflecting the increased ISM cooling in galaxies as a result of their higher star-formation rates. These observations demonstrate that even with short integrations, ALMA is able to detect the dominant fine structure cooling lines from high-redshift ULIRGs, measure their energetics and trace their evolution with redshift., Comment: Accepted for publication in MNRAS. 10 pages, 5 figures, 2 tables

We present Herschel-PACS spectroscopy of the [OI]63um far-infrared cooling line from a sample of six unlensed and spectroscopically-confirmed 870um-selected submillimetre (submm) galaxies (SMGs) at 1.13, tentatively detect [OI]63um in one SMG, and constrain the line flux for the non-detections. We also exploit the combination of submm continuum photometry from 250-870um and our new PACS continuum measurements to constrain the far-infrared (FIR) luminosity, L_FIR, in these SMGs to < 30%. We find that SMGs do not show a deficit in their [OI]63um-to-far-infrared continuum luminosity ratios (with ratios ranging from ~0.5-1.5%), similar to what was seen previously for the [CII]158um-to-FIR ratios in SMGs. These observed ratios are about an order of magnitude higher than what is seen typically for local ultra luminous infrared galaxies (ULIRGs), which adds to the growing body of evidence that SMGs are not simply `scaled up' versions of local ULIRGs. Rather, the PDR line-to-L_FIR ratios suggest that the star formation modes of SMGs are likely more akin to that of local normal (lower-luminosity) star-forming galaxies, with the bulk of the star formation occurring in extended regions, galaxy-scale (~kpc) in size. These observations represent the first step towards a census of the major PDR cooling lines in typical SMGs that will be attainable with ALMA, enabling detailed modelling to probe the global properties of the star formation and the evolutionary status of SMGs., Comment: 13 pages, 3 figures, accepted for publication in MNRAS

We describe the infrared properties of sources detected over ~36 deg^2 of sky in the GAMA 15-hr equatorial field, using data from both the Herschel Astrophysical Terahertz Large-Area Survey (H-ATLAS) and Wide-field Infrared Survey (WISE). With 5-sigma point-source depths of 34 and 0.048 mJy at 250 micron and 3.4 micron, respectively, we are able to identify 50.6% of the H-ATLAS sources in the WISE survey, corresponding to a surface density of ~630 deg^{-2}. Approximately two-thirds of these sources have measured spectroscopic or optical/near-IR photometric redshifts of z<1. For sources with spectroscopic redshifts at z<0.3, we find a linear correlation between the infrared luminosity at 3.4 micron and that at 250 micron, with +-50% scatter over ~1.5 orders of magnitude in luminosity, ~10^9 - 10^{10.5} L_sun. By contrast, the matched sources without previously measured redshifts (r>~20.5) have 250-350 micron flux density ratios that suggest either high-redshift galaxies (z>~1.5) or optically faint low-redshift galaxies with unusually low temperatures (T<~20). Their small 3.4-250 micron flux ratios favor a high-redshift galaxy population, as only the most actively star-forming galaxies at low redshift (e.g., Arp 220) exhibit comparable flux density ratios. Furthermore, we find a relatively large AGN fraction (~30%) in a 12 micron flux-limited subsample of H-ATLAS sources, also consistent with there being a significant population of high-redshift sources in the no-redshift sample., Comment: 6 pages, 5 figures, accepted to ApJ Letters

In this work we conclude the analysis of our CO line survey of Luminous Infrared Galaxies (LIRGs: L_{IR}>=10^{11}L_{sol}) in the local Universe (Paper\,I), by focusing on the influence of their average ISM properties on the total molecular gas mass estimates via the so-called X_{co}=M(H_2)/L_{co,1-0} factor. One-phase radiative transfer models of the global CO Spectral Line Energy Distributions (SLEDs) yield an X_{co} distribution with: \sim(0.6+/-0.2) M_{sol}(K km s^{-1} pc^2)^{-1} over a significant range of average gas densities, temperatures and dynamical states. The latter emerges as the most important parameter in determining X_{co}, with unbound states yielding low values and self-gravitating states the highest ones. Nevertheless in many (U)LIRGs where available higher-J CO lines (J=3--2, 4--3, and/or J=6--5) or HCN line data from the literature allow a separate assessment of the gas mass at high densities (>=10^{4} cm^{-3}) rather than a simple one-phase analysis we find that {\it near-Galactic X_{co} (3-6)\, M_sol\,(K\,km^{-1}\,pc^2)^{-1} values become possible.} We further show that in the highly turbulent molecular gas in ULIRGs a high-density component will be common and can be massive enough for its high X_{co} to dominate the average value for the entire galaxy. ......... ...this may have thus resulted to systematic underestimates of molecular gas mass in ULIRGs., Comment: 77 pages, 6 figures, one Table, accepted for publication at The Astrophysical Journal

We report results from a large molecular line survey of Luminous Infrared Galaxies (L_{IR} >= 10^{11} L_sol) in the local Universe (z<=0.1), conducted during the last decade with the James Clerk Maxwell Telescope (JCMT) and the IRAM 30-m telescope. This work presents the CO and {13}CO line data for 36 galaxies, further augmented by multi-J total CO luminosities available for other IR-bright galaxies from the literature. This yields a sample of N=70 galaxies with the star-formation (SF) powered fraction of their IR luminosities spanning L_{IR} (10^{10}-2x10^{12}) L_sol and a wide range of morphologies. Simple comparisons of their available CO Spectral Line Energy Distributions (SLEDs) with local ones, as well as radiative transfer models discern a surprisingly wide range of average ISM conditions, with most of the surprises found in the high-excitation regime. These take the form of global CO SLEDs dominated by a very warm (T_{kin}>=100 K) and dense (n>=10^4 cm^{-3}) gas phase, involving galaxy-sized (~(few)x10^9 M_sol) gas mass reservoirs under conditions that would otherwise amount only ~1% of mass per typical SF molecular cloud in the Galaxy. Some of the highest excitation CO SLEDs are found in the so-called Ultra Luminous Infrared Galaxies and seem irreducible to ensembles of ordinary SF-powered regions. Highly supersonic turbulence and high cosmic ray (CR) energy densities rather than far-UV/optical photons or SNR-induced shocks from individual SF sites can globally warm the large amounts of dense gas found in these merger-driven starbursts and easily power their extraordinary CO line excitation....., Comment: 29 pages, 12 Figures, 8 Tables, originally submitted and now accepted for publication in the Monthly Notices of the Royal Astronomical Society (only minor modifications with respect to the first version)

We model the evolution of IR galaxies using a phenomenological approach to match the observed source counts at different IR wavelengths. We introduce a new algorithm for reproducing source counts based on direct integration of probability distributions rather than Monte-Carlo sampling. We construct a simple model for the evolution of the luminosity function and the colour distribution of IR galaxies which utilizes a minimum number of free parameters. Moreover we analyze how each of these parameters is constrained by observational data. The model is based on pure luminosity evolution and adopts the Dale & Helou SED templates. We find that the 850um source counts and their redshift distribution depend strongly on the shape of the luminosity evolution function, but only weakly on the details of the SEDs. We derive the best-fit evolutionary model using the 850um counts and redshift distribution as constraints. Moreover our best-fit shows a flattening of the faint end of the luminosity function towards high redshifts and requires a colour evolution which implies the typical dust temperatures of objects with the same luminosities to decrease with redshift. We compare our best-fit model to observed source counts at shorter and longer wavelengths which indicates our model reproduces the 70um and 1100um source counts remarkably well, but under-produces the counts at intermediate wavelengths. Analysis reveals that the discrepancy arises at low redshifts, indicating that revision of the adopted SED library towards lower dust temperatures (at a fixed infrared luminosity) is required. This modification is equivalent to a population of cold galaxies existing at low redshifts, as also indicated by recent Herschel results, which are underrepresented in IRAS sample. We show that the modified model successfully reproduces the source counts in a wide range of IR and submm wavelengths., Comment: 21 pages, 11 figures, 2 tables. Accepted for publication in MNRAS. Supplementary information could be found at http://www.strw.leidenuniv.nl/genesis/

We present the detection of four rotational emission lines of water vapor, from energy levels Eu/k= 101 - 454 K, in the gravitationally lensed z=3.9 QSO host galaxy APM08279+5255. While the lowest H2O lines are collisionally excited in clumps of warm, dense gas (density of hydrogen nuclei n_H=(3.1 +/- 1.2) x 10^6 cm^-3, gas temperature T_g ~ 105 +/- 21 K), we find that the excitation of the higher lines is dominated by the intense local infrared radiation field. Since only collisionally excited emission contributes to gas cooling, we conclude that H2O is not a significant coolant of the warm molecular gas. Our excitation model requires the radiatively excited gas to be located in an extended region of high 100 micron opacity (tau_100 = 0.9 +/- 0.2). Locally, such extended infrared-opaque regions are found only in the nuclei of ultraluminous infrared galaxies. We propose a model where the infrared-opaque circumnuclear cloud, which is penetrated by the X-ray radiation field of the QSO nucleus, contains clumps of massive star formation where the H2O emission originates. The radiation pressure from the intense local infrared radiation field exceeds the thermal gas pressure by about an order of magnitude, suggesting close to Eddington-limited star formation in these clumps., Comment: accepted for publication in Astrophysical Journal Letters; typos fixed

We determine star formation rates (SFRs) in a sample of color-selected, star-forming (sBzK) galaxies (K(AB)<21.8) in the Extended Chandra Deep Field - South. To identify and avoid active galactic nuclei, we use X-ray, IRAC color, and IR/radio flux ratio selection methods. Photometric redshift-binned, average flux densities are measured with stacking analyses in Spitzer-MIPS IR, BLAST and APEX/LABOCA submillimeter, VLA and GMRT radio and Chandra X-ray data. We include averages of aperture fluxes in MUSYC UBVRIz'JHK images to determine UV-through-radio spectral energy distributions. We determine the total IR luminosities and compare SFR calibrations from FIR, 24 micron, UV, radio and X-ray wavebands. We find consistency with our best estimator, SFR(IR+UV), to within errors for the preferred radio SFR calibration. Our results imply that 24 micron only and X-ray SFR estimates should be applied to high redshift galaxies with caution. Average IR luminosities are consistent with luminous infrared galaxies. We find SFR(IR+UV) for our stacked sBzKs at median redshifts 1.4, 1.8, and 2.2 to be 55+/-6 (random error), 74+/-8 and 154+/-17 Msun yr^-1 respectively, with additional systematic uncertainty of a factor of ~2., Comment: 27 pages, 6 figures, 8 tables. Accepted for publication in The Astrophysical Journal

We present integral field spectroscopy in the near infrared (NIR) of He 2-10 and NGC 5253, two well known nearby dwarf irregular galaxies showing high star-formation rates. Our data provide an unprecedented detailed view of the interstellar medium and star formation in these galaxies, allowing us to obtain spatially resolved information from the NIR emission and absorption line tracers. We study the spatial distribution and kinematics of different components of the interstellar medium (ISM) mostly through the Bracket series lines, the molecular hydrogen spectrum, [FeII] emission, and CO absorptions. Although the ISM is mostly photo-excited, as derived by the [FeII]/Bry and H2 line ratios, some regions corresponding to non-thermal radio sources show a [FeII]/Bry excess due to a significant contribution of SN driven shocks. In He 2-10 we find that the molecular gas clouds, as traced by CO(2-1) and H2 infrared line, show consistent morphologies and velocities when studied with the two different tracers. Moreover, there is a clear association with the youngest super star clusters as traced by the ionized gas. In the same galaxy we observe a cavity depleted of gas, which is surrounded by some of the most active regions of star formation, that we interpret as a signature of feedback-induced star formation from older episodes of star formation. Finally, we measured high turbulence in the ISM of both galaxies, sigma~30-80 km/s, driven by the high star-formation activity., Comment: 12 pages, 10 figures, accepted for publication in A&A

A large sub-mm survey with Herschel will enable many exciting science opportunities, especially in an era of wide-field optical and radio surveys and high resolution cosmic microwave background experiments. The Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron, respectively, in the southern hemisphere (3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which have extensive multi-wavelength coverage and are easily accessible from ALMA. Two thirds of the of the sources are expected to be at z > 1, one third at z > 2 and about a 1000 at z > 5. (b) Remove point source confusion in secondary anisotropy studies with Planck and ground-based CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources leading to a 2% test of general relativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an unbiased study of the environmental dependence of star formation. (e) Perform an unbiased survey for star formation and dust at high Galactic latitude and make a census of debris disks and dust around AGB stars and white dwarfs., Comment: White paper supplement to the proposal submitted by the HSLS science team to ESA for Herschel open-time programs

We present results from the earliest observations of DEBRIS, a Herschel Key Programme to conduct a volume- and flux-limited survey for debris discs in A-type through M-type stars. PACS images (from chop/nod or scan-mode observations) at 100 and 160 micron are presented toward two A-type stars and one F-type star: beta Leo, beta UMa and eta Corvi. All three stars are known disc hosts. Herschel spatially resolves the dust emission around all three stars (marginally, in the case of beta UMa), providing new information about discs as close as 11 pc with sizes comparable to that of the Solar System. We have combined these data with existing flux density measurements of the discs to refine the SEDs and derive estimates of the fractional luminosities, temperatures and radii of the discs., Comment: to be published in A&A, 5 pages, 2 color figures

We have detected the CO(2-1) transition from the submillimetre galaxy (SMG) LESSJ033229.4-275619 at z=4.755 using the new Compact Array Broadband Backend system on the Australian Telescope Compact Array. These data have identified a massive gas reservoir available for star formation for the first time in an SMG at z~5. We use the luminosity and velocity width (FWHM of 160 km/s) of the CO(2--1) line emission to constrain the gas and dynamical mass of Mgas~1.6x10^10 Msun and Mdyn(<2kpc)~5x10^10 (0.25/sin^2(i)) Msun, respectively, similar to that observed for SMGs at lower redshifts of z~2-4, although we note that our observed CO FWHM is a factor of ~3 narrower than typically seen in SMGs. Together with the stellar mass we estimate a total baryonic mass of Mbary~1x10^11 Msun, consistent with the dynamical mass for this young galaxy within the uncertainties. Dynamical and baryonic mass limits of high-redshift galaxies are useful tests of galaxy formation models: using the known z~4-5 SMGs as examples of massive baryonic systems, we find that their space density is consistent with that predicted by current galaxy formation models. In addition, these observations have helped to confirm that z~4-5 SMGs possess the baryonic masses and gas consumption timescales necessary to be the progenitors of the luminous old red galaxies seen at z~3. Our results provide a preview of the science that ALMA will enable on the formation and evolution of the earliest massive galaxies in the Universe., Comment: Accepted for publication in MNRAS Letters July 5, 2010: 5 pages, 3 figures

We report on new sensitive CO J=6-5 line observations of several luminous infrared Galaxies (LIRGs: L$_{\rm IR}$(8-1000$\mu $m$)\ga 10^{11}$ L$_{\odot}$), 36% (8/22) of them ULIRGs (L$_{\rm IR}$$>10^{12}$ L$_{\odot}$), and two powerful local AGN: the optically luminous QSO PG 1119+120, and the powerful radio galaxy 3C 293 using the James Clerk Maxwell Telescope (JCMT) on Mauna Kea in Hawaii. We combine these observations with existing low-J CO data and dust emission Spectral Energy Distributions (SEDs) in the far-infrared - submillimetre from the literature to constrain the properties of the star-forming ISM in these systems. We then build the first {\it local} CO Spectral Line Energy Distributions (SLEDs) for the {\it global} molecular gas reservoirs that reach up to high J-levels. These CO SLEDs are neither biased by strong lensing (which affects many of those constructed for high-redshift galaxies), nor suffer from undersampling of CO-bright regions (as most current high-J CO observations of nearby extended systems do). We find: ..., Comment: 45 pages, 12 figures, accepted for publication at The Astrophysical Journal

We present a joint analysis of the overlapping BLAST 250, 350, 500um, and LABOCA 870um observations (from the LESS survey) of the ECDF-S. Out to z~3, the BLAST filters sample near the peak wavelength of far-infrared (FIR) emission from galaxies (rest-frame wavelengths ~60--200um), primarily produced by dust heated through absorption in star-forming clouds. However, identifying counterparts to individual BLAST peaks is very challenging, given the large beams (FWHM 36--60"). In contrast, the 870um observations have a significantly smaller 19" FWHM beam, and are sensitive to higher redshifts (z~1--5, and potentially beyond) due to the more favourable negative K-correction. We use the LESS data, as well as deep Spitzer and VLA imaging, to identify 118 individual sources that produce significant emission in the BLAST bands. We characterize the temperatures and FIR luminosities for a subset of 69 sources which have well-measured submm SEDs and redshift measurements out to z~3. For flux-limited sub-samples in each BLAST band, and a dust emissivity index \beta=2.0, we find a median temperature T=30K (all bands) as well as median redshifts: z=1.1 (interquartile range 0.2--1.9) for S250 > 40mJy; z=1.3 (interquartile range 0.6--2.1) for S350 > 30mJy; and z=1.6 (interquartile range 1.3--2.3) for S500 > 20mJy. Taking into account selection effects for our survey (a bias toward detecting lower-temperature galaxies), we find no evidence for evolution in the local FIR-temperature correlation out to z~2.5. Comparing with star-forming galaxy SED templates, about 8% of our sample appears to exhibit significant excesses in the radio and/or mid-IR, consistent with those sources harbouring an AGN. We describe the following techniques in two appendices: our `matched filter' for identifying sources in the presence of point-source confusion; and our approach for identifying counterparts using likelihood ratios., Comment: 54 pages, 16 figures, 10 tables. Accepted by MNRAS. This revision matches the accepted version: source list reduced from 125 to 118 objects; additional tests for matching catalogue, flux bias, and clustering; and simulation of SPIRE data. Data (maps, catalogues) are available at http://www.blastexperiment.info/results.php

We report new single dish CO J=6--5 line observations for the archetypal Ultra Luminous Infrared Galaxy (ULIRG) Arp 220 with the James Clerk Maxwell Telescope atop Mauna Kea in Hawaii. The J=6--5 line is found to be faint, with brightness temperature ratios (6--5)/(1--0), (6--5)/(3--2) of R_{65/10} = 0.080+/-0.017 and R_{65/32} = 0.082+/-0.019, suggesting very low excitation conditions that cannot be reconciled with the warm and very dense molecular gas present in one of the most extreme starbursts in the local Universe. We find that an optically thick dust continuum, with tau(f>350 GHz)>=1 for the bulk of the warm dust and gas in Arp 220, submerges this line to an almost black body curve, reducing its flux, and {\it affecting its CO Spectral Line Energy Distribution (SLED) at high frequencies}. This also resolves the CII line deficiency in this object, first observed by {\it ISO}: the near absence of that line is a dust optical depth effect, not a dense Photodissociation Region (PDR) phenomenon. Finally we briefly comment on the possibility of such extreme ISM states in other ULIRGs in the distant Universe, and its consequences for the diagnostic utility of high frequency molecular and atomic ISM lines in such systems. In the case of Arp 220 we anticipate that the now spaceborne Herschel Space Observatory will find faint high-J CO lines at f>=690 GHz that would appear as sub-thermally excited with respect to the low-J ones as a result of the effects of dust absorption., Comment: 18 pages, 5 figures, accepted for publication at the Astrophysical Journal

We report on the identification of the highest redshift submm-selected source currently known: LESSJ033229.4-275619. This source was detected in the Large Apex BOlometer CAmera (LABOCA) Extended Chandra Deep Field South (ECDFS) Submillimetre Survey (LESS), a sensitive 870-um survey (~1.2-mJy rms) of the full 30'x30' ECDFS with the LABOCA camera on the Atacama Pathfinder EXperiment (APEX) telescope. The submm emission is identified with a radio counterpart for which optical spectroscopy provides a redshift of z=4.76. We show that the bolometric emission is dominated by a starburst with a star formation rate of ~1000 Msun/yr, although we also identify a moderate luminosity Active Galactic Nucleus (AGN) in this galaxy. Thus it has characteristics similar to those of z~2 submm galaxies (SMGs), with a mix of starburst and obscured AGN signatures. This demonstrates that ultraluminous starburst activity is not just restricted to the hosts of the most luminous (and hence rare) QSOs at z~5, but was also occurring in less extreme galaxies at a time when the Universe was less than 10% of its current age. Assuming that we are seeing the major phase of star formation in this galaxy, then we demonstrate that it would be identified as a luminous distant red galaxy at z~3 and that the current estimate of the space density of z>4 SMGs is only sufficient to produce ~10% of the luminous red galaxy population at these early times. However, this leaves open the possibility that some of these galaxies formed through less intense, but more extended star formation events. If the progenitors of all of the luminous red galaxies at z~3 go through an ultraluminous starburst at z>4 then the required volume density of z>4 SMGs will exceed that predicted by current galaxy formation models by more than an order of magnitude., Comment: 10 pages, 4 figures, 1 table, Accepted for publication in MNRAS Feb 23

METIS, the Mid-infrared ELT Imager and Spectrograph (formerly called MIDIR), is a proposed instrument for the European Extremely Large Telescope (E-ELT), currently undergoing a phase-A study. The study is carried out within the framework of the ESO-sponsored E-ELT instrumentation studies. METIS will be designed to cover the E-ELT science needs at wavelengths longward of 3um, where the thermal background requires different operating schemes. In this paper we discuss the main science drivers from which the instrument baseline has been derived. Specific emphasis has been given to observations that require very high spatial and spectral resolution, which can only be achieved with a ground-based ELT. We also discuss the challenging aspects of background suppression techniques, adaptive optics in the mid-IR, and telescope site considerations. The METIS instrument baseline includes imaging and spectroscopy at the atmospheric L, M, and N bands with a possible extension to Q band imaging. Both coronagraphy and polarimetry are also being considered. However, we note that the concept is still not yet fully consolidated. The METIS studies are being performed by an international consortium with institutes from the Netherlands, Germany, France, United Kingdom, and Belgium., Comment: 15 pages, to be published in Proc SPIE 7014: Ground-based & Airborne Instrumentation for Astronomy II

Recently, mid-infrared instruments have become available on several large ground-based telescopes, resulting in data sets with unprecedented spatial resolution at these long wavelengths. In this paper we examine 'ground-based-only' diagnostics, which can be used in the study of star-forming regions in starburst galaxies. By combining output from the stellar population synthesis code Starburst 99 with the photoionization code Mappings, we model stellar clusters and their surrounding interstellar medium, focusing on the evolution of emission lines in the N- and Q-band atmospheric windows (8-13 and 16.5-24.5 micron respectively) and those in the near-infrared. We address the detailed sensitivity of various emission line diagnostics to stellar population age, metallicity, nebular density, and ionization parameter. Using our model results, we analyze observations of two stellar clusters in the overlap region of the Antennae galaxies obtained with VLT Imager and Spectrometer for mid Infrared (VISIR). We find evidence for clumpy, high density, ionized gas. The two clusters are young (younger than 2.5 and 3 Myr respectively), the surrounding interstellar matter is dense (10^4 cm^-3 or larger) and can be characterized by a high ionization parameter (logU > -1.53). Detailed analysis of the mid-infrared spectral features shows that a (near-)homogeneous medium cannot account for the observations, and that complex structure on scales below the resolution limit, containing several young stellar clusters embedded in clumpy gas, is more likely., Comment: 24 pages, 16 figures (3 in color), accepted for publication in ApJ

We report on detections of the high-excitation CO J=6-5, J=4-3 lines in Mrk231, a prototypical Ultra Luminous Infrared Galaxy (ULIRG) and Seyfert 1 QSO. These observations are combined with CO J=3-2, HCN J=4-3 (this work), and CO J=2-1, J=1-0, 13CO J=2-1, HCN J=1-0 measurements taken from the literature to provide better constraints on the properties of the molecular gas in an extreme starburst/QSO in the local Universe. We find that the CO J=4-3 and J=6-5 transitions trace a different gas phase from that dominating the lower three CO transitions, with n(H_2) ~ (1-3)x10^4 cm-3 and Tk ~ (40-70) K. This phase is responsible for the luminous HCN emission, and contains most of the H2 gas mass of this galaxy. The total CO line cooling emanating from this dense phase is found similar to that of the [CII] line at 158 micron, suggesting a very different thermal balance to that seen in lower IR-luminosity galaxies, and one likely dominated by dense photon-dominated regions. Our dense "sampling" of the CO rotational ladder and the HCN lines enables us to produce well-constrained Spectral Line Energy Distributions (SLEDs) for the dense molecular gas in Mrk231 and compare them to those of high redshift starbursts, many of which have SLEDs that may be affected by strong lensing. Finally, we use our local molecular line excitation template to assess the capabilities of future cm and mm/sub-mm arrays in detecting CO and HCN transitions in similar systems throughout the local and distant universe., Comment: accepted for publication in The Astrophysical Journal; 37 pages, preprint format; 5 figures (2 in color)

A large CO, HCN multi-transition survey of 30 Luminous Infrared Galaxies ($\rm L_{IR}>10^{11} L_{\odot}$) is nearing completion with the James Clerk Maxwell Telescope (JCMT) on Mauna Kea (Hawaii), and the IRAM 30-meter telescope at Pico Veleta (Spain). The CO J=1--0, 2--1, 3--2, 4--3,6--5, $ ^{13}$CO J=2--1, HCN J=1--0, 3--2, 4--3 observations, resulting from $\sim 250$ hours of JCMT, $\sim 100$ hours of 30-m observing time and data from the literature constitute {\it the largest extragalactic molecular line survey to date}, and can be used to address a wide range of issues and eventually allow the construction of reliable Spectral Line Energy Distributions (SLEDs) for the molecular gas in local starbursts. First results suggest that: a) HCN and HCO$^+$ J=1--0 line luminosities can be poor mass estimators of dense molecular gas ($\rm n\geq 10^4 cm^{-3}$) unless their excitation is accounted for, b) CO cooling of such gas in ULIRGs may be comparable to that of the CII line at $\rm 158 \mu m$, and c) low excitation of the {\it global} molecular gas reservoir remains possible in such systems. In such cases the expected low CO $\rm J+1\to J$ line luminosities for $\rm J+1\geq 4$ can lead to a strong bias against their detection from ULIRGs at high redshifts., Comment: 4 pages, to appear in Astrophysics and Space Science (special issue for 2006 conference "Science with ALMA: a new era for Astrophysics")

Using the Gemini Near-InfraRed Spectrograph (GNIRS), we have assembled a complete sample of 20 K-selected galaxies at 2.0

We present deep submillimeter imaging of two spectroscopically confirmed z~6.5 Lyman-alpha emitters (LAEs) in the Subaru Deep Field. Although we reach the nominal confusion limit at 850 micron, neither LAE is detected at 850 micron nor 450 micron, thus we conclude that the LAEs do not contain large dust masses (<2.3e8 Msun and <5.7e8 Msun). The limit on their average L(FIR)/L(UV) ratios (<~35) is substantially lower than seen for most submillimeter selected galaxies at z~3, and is within the range of values exhibited by Lyman-break galaxies. We place upper-limits on their individual star formation rates of <~248 Msun/yr and <~613 Msun/yr, and on the cosmic star formation rate density of the z~6.5 LAE population of <~0.05 Msun/yr/Mpc^3. In the two submm pointings, we also serendipitously detect seven sources at 850 micron that we estimate to lie at 1

We analyze very deep HST, VLT and Spitzer photometry of galaxies at 22 galaxies. The estimated distributions of these properties do not change significantly when adding IRAC data 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 > 1) galaxies, but only by a factor of 1.3 for blue (U-V < 1) galaxies. We find a similar color-dependence of the improvement for estimates of age and dust extinction. In addition, the improvement from adding IRAC depends on the availability of full near-infrared JHK coverage; if only K-band were available, the mass uncertainties of blue galaxies would decrease by a more substantial factor 1.9. Finally, we find that a trend of galaxy color with stellar mass is already present at z>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., Comment: Accepted for publication in the Astrophysical Journal, 16 pages, 16 figures

In this letter we present ground-based subarcsecond mid-infrared imaging and spectroscopy of young super star clusters in the overlap region of the merging galaxies NGC4038/4039 (the Antennae) obtained with the VLT Imager and Spectrometer for mid-Infrared (VISIR). With its unprecedented spatial resolution VISIR begins to resolve the HII/PDR complexes around the star-forming regions for the first time. In the N-band spectra of two young star clusters unexpectedly low polycyclic aromatic hydrocarbon (PAH) emission is observed, compared to what is seen with the Infrared Space Observatory (ISO) and with the Spitzer Space Telescope. We conclude that a large fraction of the PAH emission cannot directly be associated with the super star clusters, but originate from an extended region of at least 215 pc radius around the clusters. In the distribution of [NeII] 12.81 micron emission a highly obscured cluster is discovered that does not have an optical or near-infrared counterpart., Comment: 4 pages, 4 figures, accepted for publication in ApJL

(Abridged) We present the evolution of the volume averaged properties of the rest-frame optically luminous galaxy population to z~3, determined from four disjoint deep fields with optical to near-infrared wavelength coverage. We select galaxies above a rest-frame V-band luminosity of 3x10^10 Lsol and characterize their rest-frame UV through optical properties via the mean spectral energy distribution (SED). To measure evolution we apply the same selection criteria to a sample of galaxies from the Sloan Digital Sky Survey and COMBO-17. The mean rest-frame 2200Ang through V-band SED becomes steadily bluer with increasing redshift but at z<3 the mean SED falls within the range defined by ``normal'' galaxies in the nearby Universe. We measure stellar mass-to-light ratios (Mstar/L) by fitting models to the rest-frame UV-optical SEDs and derive the stellar mass density. The stellar mass density in luminous galaxies has increased by a factor of 3.5-7.9 from z=3 to z=0.1, including field-to-field variance uncertainties. After correcting to total, the measured mass densities at z<2 lie below the integral of the star formation rate (SFR) density as a function of redshift as derived from UV selected samples. This may indicate a systematic error in the mass densities or SFR(z) estimates. We find large discrepancies between recent model predictions for the evolution of the mass density and our results, even when our observational selection is applied to the models. Finally we determine that Distant Red Galaxies (selected to have J_s - K_s>2.3) in our LV selected samples contribute 30% and 64% of the stellar mass budget at z~2 and z~ 2.8 respectively. These galaxies are largely absent from UV surveys and this result highlights the need for mass selection of high redshift galaxies., Comment: Accepted for publication in the Astrophysical Journal, 24 pages, 16 figures

We use near-infrared (NIR) spectroscopy obtained with GNIRS on Gemini, NIRSPEC on KECK, and ISAAC on the VLT to study the rest-frame optical continua of three `Distant Red Galaxies' (having Js - Ks > 2.3) at z>2. All three galaxy spectra show the Balmer/4000 Angstrom break in the rest-frame optical. The spectra allow us to determine spectroscopic redshifts from the continuum with an estimated accuracy dz/(1+z) ~ 0.001-0.04. These redshifts agree well with the emission line redshifts for the 2 galaxies with Halpha emission. This technique is particularly important for galaxies that are faint in the rest-frame UV, as they are underrepresented in high redshift samples selected in optical surveys and are too faint for optical spectroscopy. Furthermore, we use the break, continuum shape, and equivalent width of Halpha together with evolutionary synthesis models to constrain the age, star formation timescale, dust content, stellar mass and star formation rate of the galaxies. Inclusion of the NIR spectra in the stellar population fits greatly reduces the range of possible solutions for stellar population properties. We find that the stellar populations differ greatly among the three galaxies, ranging from a young dusty starburst with a small break and strong emission lines to an evolved galaxy with a strong break and no detected line emission. The dusty starburst galaxy has an age of 0.3 Gyr and a stellar mass of 1*10^11 Msun. The spectra of the two most evolved galaxies imply ages of 1.3-1.4 Gyr and stellar masses of 4*10^11 Msun. The large range of properties seen in these galaxies strengthens our previous much more uncertain results from broadband photometry. Larger samples are required to determine the relative frequency of dusty starbursts and (nearly) passively evolving galaxies at z~2.5., Comment: Accepted for publication in the Astrophysical Journal. 12 pages, 6 figures

The presence of superstarclusters is a characteristic feature of starburst galaxies. We examine the properties of star forming regions and young star clusters in various environments, ranging from common to extreme. We then discuss new high spatial resolution mid-infrared imaging and spectroscopy of extreme superstarclusters in the obscured region of the Antennae (NGC4038-4039). We find that the PAH emission in this region is not dominated by the superstarclusters but is mostly diffuse. Emission line ratios found in our high spatial resolution data differ significantly from those in larger apertures, strongly affecting the derived results., Comment: invited talk, to appear in proceedings of the workshop "Extreme starbursts - near and far" in Lijiang, China, 2005; 5 pages; version with full resolution figures can be found at http://www.strw.leidenuniv.nl/~pvdwerf/pdf/Lijiang-VISIR.pdf

We present Spitzer 24micron imaging of 1.5 < z < 2.5 Distant Red Galaxies (DRGs) in the 10arcmin by 10arcmin Extended Hubble Deep Field South of the Multiwavelength Survey by Yale-Chile. We detect 65% of the DRGs with K_AB < 23.2 mag at S_24micron > 40uJy, and conclude that the bulk of the DRG population are dusty active galaxies. A mid-infrared (MIR) color analysis with IRAC data suggests that the MIR fluxes are not dominated by buried AGN, and we interpret the high detection rate as evidence for a high average star formation rate of = 130+/-30 M/yr. From this, we infer that DRGs are important contributors to the cosmic star formation rate density at z ~ 2, at a level of \~0.02 M/yr/Mpc^3 to our completeness limit of K_AB = 22.9 mag, Comment: 4 pages, 3 figures, accepted for publication in ApJL

We present the evolution of the luminosity-size and stellar mass-size relations of luminous (L_V>3.4x10^10h_70^-2L_sun) and of massive (M_*>3x10^10h_70^-2M_sun) galaxies in the last ~11 Gyr. We use very deep near-infrared images of the Hubble Deep Field-South and the MS1054-03 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

The infrared regime contains a number of unique diagnostic features for probing the astrophysics of starburst galaxies. After a brief summary of the most important tracers, we focus in detail on the use of emission lines to probe the upper part of the main sequence in a young superstarcluster in the Antennae, and the compact, dusty starburst in the nucleus of the nearby ultraluminous infrared galaxy Arp220, Comment: invited talk, to appear in Starburst - from 30 Doradus to Lyman break galaxies, eds. R. de Grijs and R.M. Gonzalez-Delgado; 6 pages with 4 figures

We present the results of observations from the IRAM array of the submm galaxy SMMJ16359+6612 lying at z=2.516 behind the massive cluster A2218. The foreground gravitational lens produces 3 images with a total mag. of 45 of this faint submm galaxy, which has an intrinsic submm flux of f_850mic=0.8mJy placing it below the confusion limit of blank-field surveys. The substantial magnification provides a rare opportunity to probe the nature of a distant sub-mJy submm-selected galaxy, part of the population which produces the bulk of the submm cosmic far-infrared background. Our observations detect the CO(3-2) line in all 3 images, as well as the CO(7-6) line and the dust continuum at 1.3mm for the brightest image. The CO(3-2) velocity profile displays a double-peak profile which is well fit by two Gaussians with FWHM of 220km/s and separated by 280km/s. We estimate the dynamical mass of the system to be ~1.5 10^10 M_sun and an H2 gas mass of 2.6 10^9 M_sun. We identify a spatial offset of ~1'' between the two CO(3-2) velocity components, modeling of which indicates that the offset corresponds to just ~3kpc in projection at z=2.5. The spatial and velocity properties of these two components are closely related to features detected in previously published Halpha spectroscopy. We conclude that this source is likely to be a compact merger of 2 fairly typical Ly-break galaxies with a maximal separation between the two nuclei of ~3kpc. This system is much less luminous and massive than other high-z submm galaxies studied to date, but it bears a close similarity to similarly luminous, dusty starburst resulting from lower-mass mergers in the local Universe., Comment: 8 pages, 2 figures, A&A in press (final accepted version)

Very deep near-infrared observations have recently uncovered a significant population of red galaxies at redshifts z>2. These distant red galaxies (DRGs) are efficiently selected by the criterion J-K>2.3. We use Chandra data to examine the X-ray emission from DRGs in the 5'x5' FIRES MS1054-03 field. Two of 40 DRGs with K<22 are detected by Chandra, and we infer that ~5 % of DRGs host active nuclei with L>1.2x10^43 ergs/s. This fraction is smaller than that inferred from optical and near-IR spectroscopy, probably largely due to strong spectroscopic selection biases. By stacking all undetected DRGs we find that their average X-ray flux in the 0.5-8 keV band is ~4.6x10^-17 ergs/s/cm^2. The detection is only significant in the soft and full energy bands. The mean detection may result from star formation, the presence of low luminosity AGN, or a combination of both. Assuming the detection is due exclusively to star formation, we find an average instantaneous star formation rate of 214 +- 68 (random) +- 73 (systematic) solar masses per year, in excellent agreement with previous results from spectral energy distribution fitting when constant star formation histories are assumed. These results may imply that DRGs contribute significantly to the cosmic star formation rate at z~2.5. However, the mean X-ray flux strictly provides only an upper limit to the star formation rate due to the uncertain contribution of low luminosity, possibly obscured AGNs. Observations at other wavelengths are needed to provide independent estimates of the star formation rate of DRGs., Comment: Accepted for publication in the Astrophysical Journal Letters

The SINFONI instrument for ESO's VLT combines integral field spectroscopy and adaptive optics (AO). We discuss detailed simulations of the adaptive optics module. These simulations are aimed at assessing the AO module performance, specifically for operations with extended sources and a laser guide star. Simulated point spread function (PSF) images will be used to support scientific preparations and the development of an exposure time calculator, while simulated wavefront sensor measurements will be used to study PSF reconstruction methods. We explain how the adaptive optics simulations work, focusing on the realistic modelling of the laser guide star for a curvature wavefront sensor. The predicted performance of the AO module is discussed, resulting in recommendations for the operation of the SINFONI AO module at the telescope., Comment: 12 pages, 6 figures, to appear in SPIE conference proceedings vol 5490, "Advancements in Adaptive Optics", eds. D. Bonaccini, B.L. Ellerbroek, R. Ragazonni, Glasgow UK, 21-25 June 2004

We recently identified a substantial population of galaxies at z>2 with red rest-frame optical colors. These distant red galaxies (DRGs) are efficiently selected by the simple observed color criterion J-K>2.3. In this paper we present NIR spectroscopy with Keck/NIRSPEC of six DRGs at 2.4

We present observations of a remarkable submillimetre-selected galaxy, SMMJ16359+6612. This distant galaxy lies behind the core of a massive cluster of galaxies, A2218, and is gravitationally lensed by the foreground cluster into three discrete images which were identified in deep submillimetre maps of the cluster core at both 450 and 850micron. Subsequent follow-up using deep optical and NIR images identify a faint counterpart to each of the 3 images, with similar red optical--NIR colours and HST morphologies. By exploiting a detailed mass model for the cluster lens we estimate that the combined images of this galaxy are magnified by a factor of ~45, implying that this galaxy would have un-lensed magnitudes K_s=22.9 and I=26.1, and an un-lensed 850micron flux density of only 0.8mJy. Moreover, the highly constrained lens model predicted the redshift of SMMJ16359+6612 to be z=2.6+/-0.4. We confirm this estimate using deep optical and NIR Keck spectroscopy, measuring a redshift of z=2.516. SMMJ16359+6612 is the faintest submm-selected galaxy so far identified with a precise redshift. Thanks to the large gravitational magnification of this source, we identify 3 sub-components in this submm galaxy, which are also seen in the NIRSPEC data, arguing for either a strong dust (lane) absorption or a merger. Interestingly, there are 2 other highly-amplified galaxies at almost identical redshifts in this field (although neither is a strong submm emitter). The 3 galaxies lie within a ~100kpc region on the background sky, suggesting this submm galaxy is located in a dense high-redshift group., Comment: 7 pages, 1 JPEG figure, MNRAS in press

We present the evolution of the rest-frame optical luminosity density, of the integrated rest-frame optical color, and of the stellar mass density for a sample of Ks-band selected galaxies in the HDF-S. We derived the luminosity density in the rest-frame U, B, and V-bands and found that the luminosity density 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 a redshift 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/LV using the correlation between (U-V)_rest and log_{10} M/LV which exists for a range in smooth SFHs and moderate extinctions. We have shown that the mean of individual M/LV estimates can overpredict the true value by ~70% while our method overpredicts the true values 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 LV>1.4 \times 10^{10} h_{70}^-2 Lsol. 50% of the stellar mass of the universe was formed by $z~1-1.5. The rate of increase in the stellar mass density with decreasing redshift is similar to but above that for independent estimates from the HDF-N, but is slightly less than that predicted by the integral of the SFR(z) curve., Comment: 19 pages, 12 figures, Accepted for Publication in the Dec. 20, 2003 edition of the Astrophysical Journal. Minor changes made to match the accepted version including short discussions on the effects of clustering and on possible systematic effects resulting from photometric redshift errors

The luminosity-size and stellar mass-size distributions of galaxies out to z~3 is presented. We use very deep near-infrared images of the Hubble Deep Field South in the J_s, H, and K_s bands, taken as part FIRES at the VLT, to follow the evolution of the optical rest-frame sizes of galaxies. For a total of 168 galaxies with K_{s,AB}<23.5, we find that the rest-frame V-band sizes r_{e,V} of luminous galaxies (~2x10^{10}h^{-2}L_sun) at 2~2x10^{10}h^{-2}M_sun, has changed by 20(+-20)% since z~2.5. Both results can be reconciled by the fact that the stellar M/L ratio is lower in the luminous high z galaxies than in nearby ones because they have young stellar populations. The lower incidence of large galaxies at z~3 seems to reflect the rarity of galaxies with high stellar mass., Comment: 39 pages, 14 figures, ApJ in press, new changes made to match the accepted version

We confirm spectroscopically the existence of a population of galaxies at z>~2 with rest-frame optical colors similar to normal nearby galaxies. The galaxies were identified by their red near-infrared colors in deep images obtained with ISAAC on the Very Large Telescope. Redshifts of six galaxies with Js-Ks>2.3 were measured from optical spectra obtained with the Keck Telescope. Five out of six are in the range 2.43<=z<=3.52, demonstrating that the Js-Ks color selection is quite efficient. The rest-frame ultraviolet spectra of confirmed z>2 galaxies display a range of properties, with two galaxies showing emission lines characteristic of AGN, two having Ly-alpha in emission, and one showing interstellar absorption lines only. Their full spectral energy distributions are well described by constant star formation models with ages 1.4-2.6 Gyr, except for one galaxy whose colors indicate a dusty starburst. The confirmed z>2 galaxies are very luminous, with Ks=19.2-19.9. Assuming that our bright spectroscopic sample is representative for the general population of Js-Ks selected objects, we find that the surface density of red z>~2 galaxies is ~0.9/arcmin^2 to Ks=21. The surface density is comparable to that of Lyman-break selected galaxies with Ks<21, when corrections are made for the different redshift distributions of the two samples. Although there will be some overlap between the two populations, most 'optical-break' galaxies are too faint in the rest-frame ultraviolet to be selected as Lyman-break galaxies. The most straightforward interpretation is that star formation in typical optical-break galaxies started earlier than in typical Lyman-break galaxies. Optical-break galaxies may be the oldest and most massive galaxies yet identified at z>2, and could evolve into early-type galaxies and bulges., Comment: Accepted for publication in the Astrophysical Journal Letters. (see also papers by Franx et al. and Daddi et al. in this listing)

We use very deep near-infrared photometry of the Hubble Deep Field South taken with ISAAC/VLT to identify a population of high redshift galaxies with rest- frame optical colors similar to those of nearby galaxies. The galaxies are chosen by their infrared colors Js-Ks > 2.3, aimed at selecting galaxies with redshifts above 2. When applied to our dataset, we find 14 galaxies with Ks < 22.5, corresponding to a surface density of 3+-0.8 /arcmin**2. The photometric redshifts all lie above 1.9, with a median of 2.6 and a rms of 0.7. The spectral energy distributions of these galaxies show a wide range: one is very blue in the rest-frame UV, and satisfies the normal Lyman-break criteria for high redshift, star-forming galaxies. Others are quite red throughout the observed spectral range, and are extremely faint in the optical, with a median V = 26.6. Hence these galaxies would not be included in photometric samples based on optical ground-based data, and spectroscopic follow-up is difficult. The spectral energy distributions often show a prominent break, identified as the Balmer break or 4000 Ang. break. The median age is 1 Gyr when fit with a constant star formation model with dust, or 0.7 Gyr when fit with a single burst model. Although significantly younger ages cannot be excluded when a larger range of models is allowed, the results indicate that these galaxies are among the oldest at these redshifts. The volume density to Ks=22.5 is half that of Lyman-break galaxies at z = 3. Since the mass-to-light ratios of the red galaxies are likely to be higher, the stellar mass density is inferred to be comparable to that of Lyman-break galaxies. These red galaxies may be the descendants of galaxies which started to form stars at very high redshifts, and they may evolve into the most massive galaxies at low redshift., Comment: LaTex, 5 pages and 4 figures. Accepted for publication in ApJ Letters. See also related preprints on astroph today by Daddi et al and van Dokkum et al

In this paper we review the present status and implications of H-alpha surveys at various redshifts. With the advent of sensitive wide-format near-infrared detectors on large telescopes, deep and extensive H-alpha surveys are now feasible to redshift z~2.5. The cosmic star formation history can therefore be traced out to this redshift using H-alpha alone, avoiding complications arising from the comparison of different tracers at different redshifts. The H-alpha surveys to date confirm the rapid increase in luminosity density from z=0 out to z=1, and show that this increase flattens off at higher redshifts, remaining approximately constant out to at least z~2.2. We also discuss the prospects for determining the masses of high redshift galaxies based on emission lines. A set of high-quality H-alpha rotation curves of samples of disk galaxies at a number of different redshifts would allow a study of the evolution of the Tully-Fisher relation and address fundamental issues in disk galaxy formation. Such a program remains challenging even with present-day large telescopes., Comment: invited review to appear in Proceedings of 2nd Hellenic Cosmology Workshop, eds. M. Plionis et al (Kluwer); 16 pages including 4 figures (low resolution); ps.gz file with full resolution figures is available at http://www.strw.leidenuniv.nl/~pvdwerf/biblio/frameset-reviews.html

We present the first results from the Faint Infra-Red Extragalactic Survey (FIRES) of the Hubble Deep Field South. Using a combination of deep near infrared data obtained with ISAAC at the VLT with the WFPC2 HST data, we construct a K-band selected sample of 136 galaxies with K(AB)<=23.5. We derive zphot's using a newly developed technique which models the observed spectral energy distribution with a linear combination of empirical galaxy templates. Testing our zphot technique against spectroscopic redshifts in the HDF-N yields dz/(1+z)~0.07 for z<6. We show that we can derive realistic error estimates in zphot by combining the systematic uncertainties derived from the HDF-N with errors in zphot which depend on the observed flux errors. The redshift histogram of galaxies in the HDF-S shows distinct structure with a sharp peak at z~0.5 and a broad enhancement at z~1-1.4. We find that 12% of our galaxies with K(vega)<21 lie at z>=2. While this is higher than the fraction predicted in Omega_M=1 hierarchical models of galaxy formation we find that published predictions using pure luminosity evolution models produce too many bright galaxies at redshifts greater than unity. Finally, we use our broad wavelength coverage to measure the rest-frame UBV luminosities Lrest for z<=3. There is a paucity of galaxies brighter than Lrest_V>=1.4e10 h^{-2}Lsun at z~1.5-2, however, at z>2 we find very luminous galaxies with Lrest_V>=5e10 h^{-2}Lsun (for Omega_M=0.3,Lambda=0.7, H_o=100 h km s^{-1}Mpc^{-1}). Local B-band luminosity functions predict 0.1 galaxies in the redshift range 2<=z<=3.5 and with Lrest_B>= 5e10 h^{-2}Lsun,B but we find 9. The discrepancy can be explained if L*_B increases by a factor of 2.4-3.2 with respect to locally determined values (abridged)., Comment: 46 pages, 15 figures, 3 Tables, Accepted for publication in Astronomical Journal, paper and high resolution figures available at http://www.strw.leidenuniv.nl/~fires/, minor changes to comply with referee's comments