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Modern astrophysics relies on intricate instrument setups to meet the demands of sensitivity, sky coverage, and multi-channel observations. An example is the CONCERTO project, employing advanced technology like kinetic inductance detectors and a Martin-Puplett interferometer. This instrument, installed at the APEX telescope atop the Chajnantor plateau, began commissioning observations in April 2021. Following a successful commissioning phase that concluded in June 2021, CONCERTO was offered to the scientific community for observations, with a final observing run in December 2022. CONCERTO boasts an 18.5 arcmin field of view and a spectral resolution down to 1.45 GHz in the 130-310 GHz electromagnetic band. We developed a comprehensive instrument model of CONCERTO inspired by Fourier transform spectrometry principles to optimize performance and address systematic errors. This model integrates instrument noises, subsystem characteristics, and celestial signals, leveraging both physical data and simulations. Our methodology involves delineating simulation components, executing on-sky simulations, and comparing results with real observations. The resulting instrument model is pivotal, enabling a precise error correction and enhancing the reliability of astrophysical insights obtained from observational data. In this work, we focus on the description of three white-noise noise components included in the instrument model that characterize the white-noise level: the photon, the generation-recombination, and the amplifier noises., Comment: 8 pages, 1 figure, Proceeding of the SPIE conference Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XII, SPIE Astronomical Telescopes + Instrumentation 2024

CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn) is a low-resolution Fourier transform spectrometer dedicated to the study of star-forming galaxies and clusters of galaxies in the transparent millimeter windows from the ground. It is characterized by a wide instantaneous 18.6 arcmin field of view, operates at 130-310 GHz, and was installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5100 m above sea level. CONCERTO's double focal planes host two arrays of 2152 kinetic inductance detectors and represent a pioneering instrument to meet a state-of-the-art scientific challenge. This paper introduces the CONCERTO instrument and explains its status, shows the first CONCERTO spectral maps of Orion, and describes the perspectives of the project., Comment: 6 pages, 2 figures, to appear in Proc. of the mm Universe 2023 conference, Grenoble (France), June 2023, published by F. Mayet et al. (Eds), EPJ Web of conferences, EDP Sciences

We have carried out HST snapshot observations at 1.1 $\mu$m of 281 candidate strongly lensed galaxies identified in the wide-area extragalactic surveys conducted with the Herschel space observatory. Our candidates comprise systems with flux densities at $500\,\mu$m$ S_{500}\geq 80$ mJy. We model and subtract the surface brightness distribution for 130 systems, where we identify a candidate for the foreground lens candidate. After combining visual inspection, archival high-resolution observations, and lens subtraction, we divide the systems into different classes according to their lensing likelihood. We confirm 65 systems to be lensed. Of these, 30 are new discoveries. We successfully perform lens modelling and source reconstruction on 23 systems, where the foreground lenses are isolated galaxies and the background sources are detected in the HST images. All the systems are successfully modelled as a singular isothermal ellipsoid. The Einstein radii of the lenses and the magnifications of the background sources are consistent with previous studies. However, the background source circularised radii (between 0.34 kpc and 1.30 kpc) are $\sim$3 times smaller than the ones measured in the sub-mm/mm for a similarly selected and partially overlapping sample. We compare our lenses with those in the SLACS survey, confirming that our lens-independent selection is more effective at picking up fainter and diffuse galaxies and group lenses. This sample represents the first step towards characterising the near-IR properties and stellar masses of the gravitationally lensed dusty star-forming galaxies., Comment: 57 pages, 18 figures, 11 tables. Accepted for publication in MNRAS

Understanding the nature of high-$z$ dusty galaxies requires a comprehensive view of their ISM and molecular complexity. However, the molecular ISM at high-$z$ is commonly studied using only a few species beyond CO, limiting our understanding. In this paper, we present the results of deep 3 mm spectral line surveys using the NOEMA targeting two lensed dusty galaxies: APM 08279+5255 (APM), a quasar at redshift $z=3.911$, and NCv1.143 (NC), a $z=3.565$ starburst galaxy. The spectral line surveys cover rest-frame frequencies from about 330-550 GHz. We report the detection of 38 and 25 emission lines in APM and NC, respectively. The spectra reveal the chemical richness and the complexity of the physical properties of the ISM. By comparing the spectra of the two sources and combining the gas excitation analysis, we find that the physical properties and the chemical imprints of the ISM are different between them: the molecular gas is more excited in APM, exhibiting higher molecular-gas temperatures and densities compared to NC; the chemical abundances in APM are akin to the values of local AGN, showing boosted relative abundances of the dense gas tracers that might be related to high-temperature chemistry and/or XDRs, while NC more closely resembles local starburst galaxies. The most significant differences are found in H2O, where the 448GHz H2O line is significantly brighter in APM, likely linked to the intense far-infrared radiation from the dust powered by AGN. Our astrochemical model suggests that at such high column densities, FUV radiation is less important in regulating the ISM, while CRs (X-rays/shocks) are the key players in shaping the abundance of the molecules and the initial conditions of star formation. Such deep spectral line surveys open a new window to study the physical and chemical properties of the ISM and the radiation field of galaxies in the early Universe. (abridged), Comment: Accepted for publication in A&A. 39 pages (including 9 pages of Appendix). Updated after language editing

CarbON CII line in post-rEionization and ReionizaTiOn (CONCERTO) is a low-resolution spectrometer with an instantaneous field-of-view of 18.6 arcmin, operating in the 130-310 GHz transparent atmospheric window. It is installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5100 m above sea level. The Fourier transform spectrometer (FTS) contains two focal planes hosting a total of 4304 kinetic inductance detectors. The FTS interferometric pattern is recorded on the fly while continuously scanning the sky. One of the goals of CONCERTO is to characterize the large-scale structure of the Universe by observing the integrated emission from unresolved galaxies. This methodology is an innovative technique and is called line intensity mapping. In this paper, we describe the CONCERTO instrument, the effect of the vibration of the FTS beamsplitter, and the status of the CONCERTO main survey., Comment: 9 pages, 7 figures, to appear in the Proceedings of SPIE Astronomical Telescopes + Instrumentation 2022

We describe the on-line algorithms developed to probe Lumped Element Kinetic Inductance Detectors (LEKID) in this paper. LEKIDs are millimeter wavelength detectors for astronomy. LEKID arrays are currently operated in different instruments as: NIKA2 at the IRAM telescope in Spain, KISS at the Teide Observatory telescope in Tenerife, and CONCERTO at the APEX 12-meter telescope in Chile. LEKIDs are superconducting microwave resonators able to detect the incoming light at millimeter wavelengths and they are well adapted for frequency multiplexing (currently up to 360 pixels on a single microwave guide). Nevertheless, their use for astronomical observations requires specific readout and acquisition systems both to deal with the instrumental and multiplexing complexity, and to adapt to the observational requirements (e.g. fast sampling rate, background variations, on-line calibration, photometric accuracy, etc). This paper presents the different steps of treatment from identifying the resonance frequency of each LEKID to the continuous automatic control of drifting LEKID resonance frequencies induced by background variations.

Lyman-$\alpha$ blobs (LABs) are spatially extended nebulae of emission in the Ly$\alpha$ line of hydrogen, seen at high redshifts$^{1,2}$, and most commonly found in the dense environment of star-forming galaxies$^{3,4}$. The origin of Ly$\alpha$ emission in the LABs is still unclear and under debate$^{5}$. Proposed powering sources generally fall into two categories: (1) photoionization, galactic super-winds/outflows, resonant scattering of Ly$\alpha$ photons from starbursts or active galactic nuclei (AGNs)$^{6,7,8,9,10}$ and (2) cooling radiation from cold streams of gas accreting onto galaxies$^{12}$. Here we analyze the gas kinematics within a LAB providing rare observational evidence for infalling gas. This is consistent with the release of gravitational accretion energy as cold streams radiate Ly$\alpha$ photons. It also provides direct evidence for possible cold streams feeding the central galaxies. The infalling gas is not important by mass but hints at more than one mechanism to explain the origin of the extended Ly$\alpha$ emission around young galaxies. It is also possible that the infalling gas may represent material falling back to the galaxy from where it originated, forming a galactic fountain., Comment: 30 pages, 7 figures, submitted to Nature Astronomy. The full-text access to a view-only version of the published paper is available by using the following SharedIt link: https://rdcu.be/b2JkM

Millimeter-wave continuum astronomy is today an indispensable tool for both general Astrophysics studies and Cosmology. General purpose, large field-of-view instruments are needed to map the sky at intermediate angular scales not accessible by the high-resolution interferometers and by the coarse angular resolution space-borne or ground-based surveys. These instruments have to be installed at the focal plane of the largest single-dish telescopes. In this context, we have constructed and deployed a multi-thousands pixels dual-band (150 and 260 GHz, respectively 2mm and 1.15mm wavelengths) camera to image an instantaneous field-of-view of 6.5arc-min and configurable to map the linear polarization at 260GHz. We are providing a detailed description of this instrument, named NIKA2 (New IRAM KID Arrays 2), in particular focusing on the cryogenics, the optics, the focal plane arrays based on Kinetic Inductance Detectors (KID) and the readout electronics. We are presenting the performance measured on the sky during the commissioning runs that took place between October 2015 and April 2017 at the 30-meter IRAM (Institut of Millimetric Radio Astronomy) telescope at Pico Veleta. NIKA2 has been successfully deployed and commissioned, performing in-line with the ambitious expectations. In particular, NIKA2 exhibits FWHM angular resolutions of around 11 and 17.5 arc-seconds at respectively 260 and 150GHz. The NEFD (Noise Equivalent Flux Densities) demonstrated on the maps are, at these two respective frequencies, 33 and 8 mJy*sqrt(s). A first successful science verification run has been achieved in April 2017. The instrument is currently offered to the astronomical community during the coming winter and will remain available for at least the next ten years., Comment: Accepted for publication on Astronomy & Astrophysics, in press

Infrared-Faint Radio Sources (IFRSs) are an unusual class of objects that are relatively bright at radio wavelengths but have faint or undetected infrared counterparts even in deep surveys. We identify and investigate the nature of IFRSs using deep radio (S$_{\rm 1.4~GHz}$ $\sim$ 100 $\mu$Jy beam$^{-1}$ at 5$\sigma$), optical (m$_{\rm r}$ $\sim$ 26 - 27.7 at 5$\sigma$), and near-IR (S$_{\rm 3.6~{\mu}m}$ $\sim$ 1.3 - 2.0 $\mu$Jy beam$^{-1}$ at 5$\sigma$) data available in two deep fields namely the Subaru X-ray Deep Field (SXDF) and the Very Large Array - VIMOS VLT Deep Survey (VLA-VVDS) field. In 1.8 deg$^{2}$ of the two fields we identify a total of nine confirmed and ten candidate IFRSs. We find that our IFRSs are high-redshift radio-loud AGN, with 12/19 sources having redshift estimates in the range of $z$ $\sim$ 1.7 - 4.3, while a limit of $z$ $\geq$ 2.0 is placed for the remaining seven sources. Notably, our study finds, for the first time, IFRSs with measured redshift $>$ 3.0, and also, the redshift estimates for IFRSs in the faintest 3.6 $\mu$m flux regime i.e., S$_{\rm 3.6~{\mu}m}$ $<$ 1.3 ${\mu}$Jy. Radio observations show that our IFRSs exhibit both compact unresolved as well as extended double-lobe morphologies, and have predominantly steep radio spectra between 1.4 GHz and 325 MHz. The non-detection of all but one IFRSs in the X-ray band and the optical-to-MIR colour (m$_{\rm r}$ - m$_{\rm 24~{\mu}m}$) suggest that a significant fraction of IFRSs are likely to be hosted in dusty obscured galaxies., Comment: 20 pages, 8 figures, 4 tables, accepted for publication in MNRAS

Double-lobe radio galaxies in the local Universe have traditionally been found to be hosted in elliptical or lenticular galaxies. We report the discovery of four spiral-host double-lobe radio galaxies (J0836+0532, J1159+5820, J1352+3126 and J1649+2635) that are discovered by cross-matching a large sample of 187005 spiral galaxies from SDSS DR7 to the full catalogues of FIRST and NVSS. J0836+0532 is reported for the first time. The host galaxies are forming stars at an average rate of 1.7 $-$ 10 M$_{\odot}$ yr$^{-1}$ and possess Super Massive Black Holes (SMBHs) with masses of a few times 10$^{8}$ M$_{\odot}$. Their radio morphologies are similar to FR-II radio galaxies with total projected linear sizes ranging from 86 kpc to 420 kpc, but their total 1.4 GHz radio luminosities are only in the range 10$^{24}$ $-$ 10$^{25}$ W Hz$^{-1}$. We propose that the formation of spiral-host double-lobe radio galaxies can be attributed to more than one factor, such as the occurrence of strong interactions, mergers, and the presence of unusually massive SMBHs, such that the spiral structures are not destroyed. Only one of our sources (J1649+2635) is found in a cluster environment, indicating that processes other than accretion through cooling flows e.g., galaxy-galaxy mergers or interactions could be plausible scenarios for triggering radio-loud AGN activity in spiral galaxies., Comment: 18 pages, 6 figures, 9 tables, accepted for publication in MNRAS

We report the discovery of a relic Giant Radio Galaxy (GRG) J021659-044920 at redshift $z \sim 1.3$ that exhibits large-scale extended, nearly co-spatial, radio and X-ray emission from radio lobes, but no detection of Active Galactic Nuclei core, jets and hotspots. The total angular extent of the GRG at the observed frame 0.325 GHz, using Giant Metrewave Radio Telescope observations is found to be ${\sim}$ 2.4 arcmin, that corresponds to a total projected linear size of $\sim$ 1.2 Mpc. The integrated radio spectrum between 0.240 and 1.4 GHz shows high spectral curvature (${\alpha}_{\rm 0.610~GHz}^{\rm 1.4~GHz} - {\alpha}_{\rm 0.240~GHz}^{\rm 0.325~GHz}$ $>$ 1.19) with sharp steepening above 0.325 GHz, consistent with relic radio emission that is $\sim$ 8 $\times$ 10$^{6}$ yr old. The radio spectral index map between observed frame 0.325 and 1.4~GHz for the two lobes varies from 1.4 to 2.5 with the steepening trend from outer-end to inner-end, indicating backflow of plasma in the lobes. The extended X-ray emission characterized by an absorbed power-law with photon index $\sim$ 1.86 favours inverse-Compton scattering of the Cosmic Microwave Background (ICCMB) photons as the plausible origin. Using both X-ray and radio fluxes under the assumption of ICCMB we estimate the magnetic field in the lobes to be 3.3 $\mu$G. The magnetic field estimate based on energy equipartition is $\sim$ 3.5 $\mu$G. Our work presents a case study of a rare example of a GRG caught in dying phase in the distant Universe., Comment: 10 pages, 5 figures, 3 tables. Published in MNRAS. Corrected typos and added a reference

We study the radio--far infrared (FIR) correlation in "blue cloud" galaxies chosen from the PRism MUltiobject Survey (PRIMUS) up to redshift ($z$) of 1.2 in the XMM-LSS field. We use rest-frame emission at 1.4 GHz in the radio and both monochromatic (at 70$\mu$m) and bolometric (between $8-1000~\mu$m) emission in the FIR. To probe the nature of the correlation up to $z\sim1.2$, where direct detection of blue star-forming galaxies is impossible with current technology, we employ the technique of image stacking at 0.325 and 1.4 GHz in the radio and in six infrared bands, viz. 24, 70, 160, 250, 350 and $500~\mu$m. For comparison, we also study the correlation for more luminous galaxies that are directly detected. The stacking analysis allows us to probe the radio--FIR correlation for galaxies that are up to 2 orders of magnitude fainter than the ones detected directly. The $k-$correction in the infrared wavebands is obtained by fitting the observed spectral energy distribution (SED) with a composite mid-IR power law and a single temperature greybody model. We find that the radio luminosity at 1.4 GHz ($L_{\rm 1.4GHz}$) is strongly correlated with monochromatic FIR luminosity at 70 $\mu$m ($L_{\rm 70\mu m}$) having slope $1.09\pm0.05$ and with bolometric luminosity ($L_{\rm TIR}$) having slope $1.11\pm0.04$. The quantity $q_{\rm TIR} (=\log_{10}[L_{\rm TIR}/(3.75\times 10^{12} L_{\rm 1.4 GHz})])$ is observed to decrease with redshift as $q_{\rm TIR} \propto (1+z)^{-0.16\pm0.03}$ probably caused due to the non-linear slope of the radio--FIR correlation. Within the uncertainties of our measurement and the limitations of our flux-limited and color-selected sample, we do not find any evolution of the radio--FIR correlation with redshift., Comment: 17 pages, 8 figures. Accepted to be published in Astrophysical Journal

Seyfert and LINER galaxies are known to exhibit compact radio emission on $\sim$ 10 to 100 parsec scales, but larger Kiloparsec-Scale Radio structures (KSRs) often remain undetected in sub-arcsec high resolution observations. We investigate the prevalence and nature of KSRs in Seyfert and LINER galaxies using the 1.4 GHz VLA FIRST and NVSS observations. Our sample consists of 2651 sources detected in FIRST and of these 1737 sources also have NVSS counterparts. Considering the ratio of total to peak flux density ($\theta$ $=$ ${\rm (S_{\rm int}/S_{\rm peak})^{1/2}}$) as a parameter to infer the presence of extended radio emission we show that $\geq$ 30$\%$ of FIRST detected sources possess extended radio structures on scales larger than 1.0 kpc. The use of low-resolution NVSS observations help us to recover faint extended KSRs that are resolved out in FIRST observations and results in $\geq$ 42.5$\%$ KSR sources in FIRST-NVSS subsample. This fraction is only a lower limit owing to the combination of projection, resolution and sensitivity effects. Our study demonstrates that KSRs may be more common than previously thought and are found across all redshifts, luminosities and radio-loudness. The extranuclear radio luminosity of KSR sources is found to be positively correlated with the core radio luminosity as well as the [O~III] $\lambda$5007{\AA} line luminosity and this can be interpreted as KSRs being powered by AGN rather than star-formation. The distributions of the FIR-to-radio ratios and mid-IR colors of KSR sources are also consistent with their AGN origin. However, contribution from star-formation cannot be ruled out particularly in sources with low radio luminosities., Comment: 15 pages, 13 figures, 4 tables, accepted for publication in MNRAS

Ultra Steep Spectrum (USS) radio sources are one of the efficient tracers of powerful High-z Radio Galaxies (HzRGs). In contrast to searches for powerful HzRGs from radio surveys of moderate depths, fainter USS samples derived from deeper radio surveys can be useful in finding HzRGs at even higher redshifts and in unveiling a population of obscured weaker radio-loud AGN at moderate redshifts. Using our 325 MHz GMRT observations (5-sigma ~ 800 microJy) and 1.4 GHz VLA observations (5-sigma ~ 80 - 100 microJy) available in two subfields (viz., VLA-VIMOS VLT Deep Survey (VLA-VVDS) and Subaru X-ray Deep Field (SXDF)) of the XMM-LSS field, we derive a large sample of 160 faint USS radio sources and characterize their nature. The optical, IR counterparts of our USS sample sources are searched using existing deep surveys, at respective wavelengths. We attempt to unveil the nature of our faint USS sources using diagnostic techniques based on mid-IR colors, flux ratios of radio to mid-IR, and radio luminosities. Redshift estimates are available for 86/116 (~ 74%) USS sources in the VLA-VVDS field and for 39/44 (~ 87%) USS sources in the SXDF fields with median values (z_median) ~ 1.18 and ~ 1.57, which are higher than that for non-USS radio sources (z_median non-USS ~ 0.99 and ~ 0.96), in the two subfields, respectively. The flux ratio of radio to mid-IR (S_1.4 GHz/S_3.6 micron) versus redshift diagnostic plot suggests that more than half of our USS sample sources distributed over z ~ 0.5 to 3.8 are likely to be hosted in obscured environments. A significant fraction (~ 26% in the VLA-VVDS and ~ 13% in the SXDF) of our USS sources without redshift estimates mostly remain unidentified in the existing optical, IR surveys, and exhibit high radio to mid-IR flux ratio limits similar to HzRGs, and thus, can be considered as potential HzRG candidates., Comment: 13 figures, 4 tables, accepted for publication in Astronomy and Astrophysics

We have carried out a deep (150 micro Jy rms) P-band, continuum imaging survey of about 40 square degrees of sky in the XMM-LSS, Lockman Hole and ELAIS-N1 fields with the GMRT. Our deep radio data, combined with deep archival observations in the X-ray (XMM/Chandra), optical (SDSS, CFHTLS), near-infrared (UKIDSS, VISTA/VIDEO), mid-infrared (Spitzer/SWIRE, Spitzer/SERVS) and far-infrared (Spitzer/SWIRE, Herschel/HerMES) will enable us to obtain an accurate census of star-forming and active galaxies out to z~2. This panchromatic coverage enables accurate determination of photometric redshifts and accurate modeling of the spectral energy distribution. We are using our large, merged photometric catalog of over 10000 galaxies to pursue a number of science goals., Comment: 4 pages, 2 figures, to appear in the proceedings of the conference "The Meterwavelength Sky", to be published by the Astronomical Society of India

Ultra Steep Spectrum (USS) radio sources are one of the efficient tracers of High Redshift Radio Galaxies (HzRGs). To search for HzRGs candidates, we investigate properties of a large sample of faint USS sources derived from our deep 325 MHz GMRT observations combined with 1.4 GHz VLA data on the two subfields (i.e., VLA-VIMOS VLT Deep Survey (VVDS) and Subaru X-ray Deep Field (SXDF)) in the XMM-LSS field. The available redshift estimates show that majority of our USS sample sources are at higher redshifts with the median redshifts ~ 1.18 and ~ 1.57 in the VLA-VVDS and SXDF fields. In the VLA-VVDS field, ~ 20% of USS sources lack the redshift estimates as well as the detection in the deep optical, IR surveys, and thus these sources may be considered as potential high-z candidates. The radio luminosity distributions suggest that a substantial fraction (~ 40%) of our USS sample sources are radio-loud sources, distributed over redshifts ~ 0.5 to 4., Comment: 4 pages, 1 figure, to appear in the proceedings of "The Metrewavelength Sky" conference held at NCRA-TIFR, Pune, during 9 - 13 December 2013

The photometer section of SPIRE is one of the key instruments on board of Herschel. Its legacy depends very much on how well the scanmap observations that it carried out during the Herschel mission can be converted to high quality maps. In order to have a comprehensive assessment on the current status of SPIRE map-making, as well as to provide guidance for future development of the SPIRE scan-map data reduction pipeline, we carried out a test campaign on SPIRE map-making. In this report, we present results of the tests in this campaign., Comment: This document has an executive summary, 6 chapters, and 102 pages. More information can be found at: https://nhscsci.ipac.caltech.edu/sc/index.php/Spire/SPIREMap-MakingTest2013

We present an X-ray stacking analysis of a sample of 38 submillimeter galaxies with =2.6 discovered at >4{\sigma} significance in the Lockman Hole North with the MAMBO array. We find a 5{\sigma} detection in the stacked soft band (0.5-2.0 keV) image, and no significant detection in the hard band (2.0-8 keV). We also perform rest-frame spectral stacking based on spectroscopic and photometric redshifts and find a ~4{\sigma} detection of Fe K{\alpha} emission with an equivalent width of EW>1 keV. The centroid of the Fe K{\alpha} emission lies near 6.7 keV, indicating a possible contribution from highly ionized Fe XXV or Fe XXVI; there is also a slight indication that the line emission is more spatially extended than the X-ray continuum. This is the first X-ray analysis of a complete, flux-limited sample of SMGs with statistically robust radio counterparts., Comment: 20 pages, 11 figures, accepted for publication in ApJ

We present deep 1.2 mm continuum mapping of a 566 arcmin^2 area within the Lockman Hole North field, previously a target of the Spitzer Wide-area Infrared Extragalactic (SWIRE) survey and extremely deep 20 cm mapping with the Very Large Array, which we have obtained using the Max-Planck millimeter bolometer (MAMBO) array on the IRAM 30 m telescope. After filtering, our full map has an RMS sensitivity ranging from 0.45 to 1.5 mJy/beam, with an average of 0.75 mJy/beam. Using the pixel flux distribution in a map made from our best data, we determine the shape, normalization, and approximate flux density cutoff for 1.2 mm number counts well below our nominal sensitivity and confusion limits. After validating our full dataset through comparison with this map, we successfully detect 41 1.2 mm sources with S/N > 4.0 and S(1.2 mm)\simeq 2-5 mJy. We use the most significant of these detections to directly determine the integral number counts down to 1.8 mJy, which are consistent with the results of the pixel flux distribution analysis. 93% of our 41 individual detections have 20 cm counterparts, 49% have Spitzer/MIPS 24 micron counterparts, and one may have a significant Chandra X-ray counterpart. We resolve \simeq 3% of the cosmic infrared background (CIB) at 1.2 mm into significant detections, and directly estimate a 0.05 mJy faint-end cutoff for the counts that is consistent with the full intensity of the 1.2 mm CIB. The median redshift of our 17 detections with spectroscopic or robust photometric redshifts is z(median)=2.3, and rises to z(median)=2.9 when we include redshifts estimated from the radio/far-infrared spectral index. By using a nearest neighbor and angular correlation function analysis, we find evidence that our S/N>4.0 detections are clustered at the 95% confidence level., Comment: 40 pages, 25 figures, accepted for publication in ApJ

We report new observations of CO (2-1) line emission toward five z~6 quasars using the Ka-band receiver system on the Expanded Very Large Array (EVLA). Strong detections were obtained in two of them, SDSS J092721.82+200123.7 and CFHQS J142952.17+544717.6, and a marginal detection was obtained in another source, SDSS J084035.09+562419.9. Upper limits of the CO (2-1) line emission have been obtained for the other two objects. The CO (2-1) line detection in J0927+2001, together with previous measurements of the CO (6-5) and (5-4) lines, reveals important constraints on the CO excitation in the central ~10 kpc region of the quasar host galaxy. The CO (2-1) line emission from J1429+5447 is resolved into two distinct peaks separated by 1.2" (~6.9 kpc), indicating a possible gas-rich, major merging system, and the optical quasar position is consistent with the west peak. This result is in good agreement with the picture in which intense host galaxy star formation is coeval with rapid supermassive black hole accretion in the most distant universe. The two EVLA detections are ideal targets for further high-resolution imaging (e.g., with ALMA or EVLA observations) to study the gas distribution, dynamics, and SMBH-bulge mass relation in these earliest quasar-host galaxy systems., Comment: 13 pages, 4 figures, accepted for publication in the EVLA ApJL Special Issue

We want to study the mid-infrared properties and the starburst and AGN contributions, of 24um sources at z~2, through analysis of mid-infrared spectra combined with millimeter, radio, and infrared photometry. Mid-infrared spectroscopy allows us to recover accurate redshifts. A complete sample of 16 Spitzer-selected sources (ULIRGs) believed to be starbursts at z~2 ("5.8um-peakers") was selected in the (0.5 sq.deg.) J1064+56 SWIRE Lockman Hole field. These sources have S(24um)>0.5mJy, a stellar emission peak redshifted to 5.8um, and r'(Vega)>23. The entire sample was observed with the low resolution units of the Spitzer/IRS infrared spectrograph. These sources have 1.2mm observations with IRAM 30m/MAMBO and very deep 20cm observations from the VLA. Nine of our sources also benefit from 350um observation and detection from CSO/SHARC-II. The entire sample shows good quality IRS spectra dominated by strong PAH features. The main PAH features at 6.2, 7.7, 8.6, and 11.3um have high S/N average luminosities of 2.90, 10.38, 3.62, and 2.29x10^{10}Lsun, respectively. We derived accurate redshifts spanning from 1.75 to 2.28. The average of these redshifts is 2.017. This result confirms that the selection criteria of "5.8um-peakers" associated with a strong detection at 24um are reliable to select sources at z~2. We have analyzed the different correlations between PAH emission and infrared, millimeter, and radio emission. Practically all our sources are strongly dominated by starburst emission. We have also defined two subsamples based on the equivalent width at 7.7um to investigate AGN contributions. Our sample contains strong starbursts and represents a particularly 24um-bright class of SMGs. The very good correlation between PAH and far-IR luminosities is now confirmed in high-z starburst ULIRGs. These sources show a small AGN contribution to the mid-IR, around ~20% in most cases., Comment: 19 pages, 14 figures + 2 figure in appendix Accepted in A&A on 26/08/201

Aims: We want to place stronger lower limits on the Cosmic Infrared Background (CIB) brightness at 24, 70 and 160 um and measure the extragalactic number counts at these wavelengths in an homogeneous way from various surveys. Methods: Using Spitzer legacy data over 53.6 deg^2 of various depths, we build catalogs with the same extraction method at each wavelength. [...] Number count uncertainties are estimated with a counts-in-cells moment method, in order to take into account galaxy clustering. Furthermore, we use a stacking analysis to estimate number counts of sources not detected at 70 and 160 um. [...] Results: Number counts reach 35 muJy (resp. 3.5 mJy and 40 mJy) at 24 um (resp. 70 and 160um). We reach deeper flux densities of 0.38 mJy at 70 and 3.1 at 160 um using a stacking analysis. [...] Conclusions: These counts are integrated to estimate new CIB firm lower limits of 2.21-0.09+0.09 nW.m^-2.sr^-1 (resp. 5.2-0.4+0.4 and 9.0-1.1+1.1 nW.m^-2.sr^-1) at 24 um (resp. 70 and 160 um), and extrapolated to give new estimates of the CIB due to galaxies of 2.78-0.16+0.18 nW.m^-2.sr^-1 (resp. 6.4-0.6+0.7 and 14.6-2.9+7.1 nW.m^-2.sr^-1). Products (PSF, counts, CIB contributions, software) are publicly available for download at http://www.ias.u-psud.fr/irgalaxies/, Comment: 15 pages, 14 figures, 7 tables, accepted by A&A

We present 870 micron images of four low metallicity galaxies (NGC1705, Haro11, Mrk1089 and UM311) observed with the Large APEX BOlometer CAmera (LABOCA). We model their spectral energy distributions combining the submm observations of LABOCA, 2MASS, IRAS, Spitzer photometric data and the IRS data for Haro11. We find that a significant mass of dust is revealed when using submm constraints compared to that measured with only mid-IR to far-IR observations extending only to 160 microns. For NGC1705 and Haro11, an excess in submillimeter wavelengths is detected and we rerun our SED procedure adding a cold dust component (10K) to better describe the high 870 micron flux derived from LABOCA observations, which significantly improves the fit. We find that at least 70% of the dust mass of these two galaxies can reside in a cold dust component. We also show that the subsequent dust-to-gas mass ratios, considering HI and CO observations, can be strikingly high for Haro11 in comparison with what is usually expected for these low-metallicity environments. Furthermore, we derive the SFR of our galaxies and compare them to the Schmidt law. Haro11 falls anomalously far from the Schmidt relation. These results may suggest that a reservoir of hidden gas could be present in molecular form not traced by the current CO observations. We also derive the total IR luminosities derived from our models and compare them with relations that derive this luminosity from Spitzer bands. We find that the Draine & Li (2007) formula compares well to our direct IR determinations., Comment: 22 pages, 7 figures, 10 tables, accepted for publication in A&A

We have used the IRAM Plateau de Bure mm interferometer and the UKIRT 1-5 um Imager Spectrometer to test the connection between the major phases of spheroid growth and nuclear accretion by mapping CO emission in nine submm-detected QSOs at z=1.7-2.6 with black hole (BH) masses derived from near-infrared spectroscopy. With a previously published QSO, we present sensitive CO(3-2) observations of 10 submm-detected QSOs selected at the epoch of peak activity in both QSOs and submm galaxies (SMGs). CO is detected in 5/6 very optically luminous (M_B~-28) submm-detected QSOs with BH masses M_BH~10^9-10^10 Msun, confirming the presence of large gas reservoirs of M_gas~3.4x10^10 Msun. However, we find that their BH masses are ~30 times too large and their surface density is ~300 times too small to be related to typical SMGs in an evolutionary sequence. Conversely, we measure weaker CO emission in four fainter (M_B~-25) submm-detected QSOs with properties, BH masses (M_BH~5x10^8 Msun), and surface densities similar to SMGs. These QSOs appear to lie near the local M_BH/M_sph relation, making them plausible `transition objects' in the proposed evolutionary sequence linking QSOs to the formation of massive young galaxies and BHs at high-redshift. We show that SMGs have a higher incidence of bimodal CO line profiles than seen in our QSO sample, which we interpret as an effect of their relative inclinations, with the QSOs seen more face-on. Finally, we find that the gas masses of the four fainter submm-detected QSOs imply that their star formation episodes could be sustained for ~10 Myr, and are consistent with representing a phase in the formation of massive galaxies which overlaps a preceding SMG starburst phase, before subsequently evolving into a population of present-day massive ellipticals. [abridged], Comment: 20 pages, 10 figures, accepted for publication in MNRAS; updated references, improved upper limits given in section 3

The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed to locate quasars during the epoch of reionization. In this paper we present the discovery of the first four CFHQS quasars at redshift greater than 6, including the most distant known quasar, CFHQS J2329-0301 at z=6.43. We describe the observational method used to identify the quasars and present optical, infrared, and millimeter photometry and optical and near-infrared spectroscopy. We investigate the dust properties of these quasars finding an unusual dust extinction curve for one quasar and a high far-infrared luminosity due to dust emission for another. The mean millimeter continuum flux for CFHQS quasars is substantially lower than that for SDSS quasars at the same redshift, likely due to a correlation with quasar UV luminosity. For two quasars with sufficiently high signal-to-noise optical spectra, we use the spectra to investigate the ionization state of hydrogen at z>5. For CFHQS J1509-1749 at z=6.12, we find significant evolution (beyond a simple extrapolation of lower redshift data) in the Gunn-Peterson optical depth at z>5.4. The line-of-sight to this quasar has one of the highest known optical depths at z~5.8. An analysis of the sizes of the highly-ionized near-zones in the spectra of two quasars at z=6.12 and z=6.43 suggest the IGM surrounding these quasars was substantially ionized before these quasars turned on. Together, these observations point towards an extended reionization process, but we caution that cosmic variance is still a major limitation in z>6 quasar observations., Comment: 15 pages, 9 figures, AJ, in press, minor changes to previous version

We present millimeter and radio observations of 13 SDSS quasars at reshifts z~6. We observed eleven of them with the Max-Planck Millimeter Bolometer Array (MAMBO-2) at the IRAM 30m-telescope at 250 GHz and all of them with the Very Large Array (VLA) at 1.4 GHz. Four sources are detected by MAMBO-2 and six are detected by the VLA at >=3 sigma level. These sources, together with another 6 published in previous papers,yield a submillimeter/millimeter and radio observed SDSS quasar sample at z~6. We use this sample to investigate the far-infrared (FIR) andradio properties of optically bright quasars in the early universe. We compare this sample to lower redshift samples of quasars observed inthe submillimeter and millimeter wavelengths ((sub)mm), and find that the distribution of the FIR to B band optical luminosity ratio (L_FIR/L_B) is similar from z~2 to 6. We find a weak correlation between the FIR luminosity (L_FIR) and B band optical luminosity (L_B) byincluding the (sub)mm observed samples at all redshifts. Some strong (sub)mm detections in the z~6 sample have radio-to-FIR ratios within the range defined by star forming galaxies, which suggests possible co-eval star forming activity with the powerful AGN in these sources. We calculate the rest frame radio to optical ratios (R*_1.4=L_{v, 1.4GHz}/L_{v, 4400A}) for all of the VLA observed sources in the z~6 quasar sample. Only one radio detection in this sample, J083643.85+005453.3, has R*_1.4~40 and can be considered radio loud. There are no strong radio sources (R*_1.4>=100) among these SDSS quasars at z~6. These data are consistent with, although do not set strong constraints on, a decreasing radio-loud quasar fraction with increasing redshift., Comment: 27 pages including 6 figures. AJ accepted

We present a search for HCN emission from four high redshift far infrared (IR) luminous galaxies. Current data and models suggest that these high $z$ IR luminous galaxies represent a major starburst phase in the formation of spheroidal galaxies, although many of the sources also host luminous active galactic nuclei (AGN), such that a contribution to the dust heating by the AGN cannot be precluded. HCN emission is a star formation indicator, tracing dense molecular hydrogen gas within star-forming molecular clouds (n(H$_2$) $\sim 10^5$ cm$^{-3}$). HCN luminosity is linearly correlated with IR luminosity for low redshift galaxies, unlike CO emission which can also trace gas at much lower density. We report a marginal detection of HCN (1-0) emission from the $z=2.5832$ QSO J1409+5628, with a velocity integrated line luminosity of $L_{\rm HCN}'=6.7\pm2.2 \times10^{9}$ K km s$^{-1}$ pc$^2$, while we obtain 3$\sigma$ upper limits to the HCN luminosity of the $z=3.200$ QSO J0751+2716 of $L_{\rm HCN}'=1.0\times10^{9}$ K km s$^{-1}$ pc$^2$, $L_{\rm HCN}'=1.6\times10^{9}$ K km s$^{-1}$ pc$^2$ for the $z= 2.565$ starburst galaxy J1401+0252, and $L_{\rm HCN}'=1.0\times10^{10}$ K km s$^{-1}$ pc$^2$ for the $z = 6.42$ QSO J1148+5251. We compare the HCN data on these sources, plus three other high-$z$ IR luminous galaxies, to observations of lower redshift star-forming galaxies. The values of the HCN/far-IR luminosity ratios (or limits) for all the high $z$ sources are within the scatter of the relationship between HCN and far-IR emission for low $z$ star-forming galaxies (truncated)., Comment: aastex format, 4 figures. to appear in the Astrophysical Journal; Revised lens magnification estimate for 1401+0252