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  1. Abstract The high-frequency radio sky has historically remained largely unexplored due to the typical faintness of sources in this regime, and the modest survey speed compared to observations at lower frequencies. However, high-frequency radio surveys offer an invaluable tracer of high-redshift star formation, as they directly target the faint radio free–free emission. We present deep continuum observations at 34 GHz in the COSMOS and GOODS-North fields from the Karl G. Jansky Very Large Array (VLA), as part of the COLD z survey. The deep COSMOS mosaic spans down to σ = 1.3 μ Jy beam −1 , while the wider GOODS-N observations cover to σ = 5.3 μ Jy beam −1 . We detect a total of 18 galaxies at 34 GHz, of which nine show radio emission consistent with being powered by star formation; although for two sources, this is likely due to thermal emission from dust. Utilizing deep ancillary radio data at 1.4, 3, 5, and 10 GHz, we decompose the spectra of the remaining seven star-forming galaxies into their synchrotron and thermal free–free components, and find typical thermal fractions and synchrotron spectral indices comparable to those observed in local star-forming galaxies. We further determine free–free star formation rates (SFRs), and show that these are in agreement with SFRs from spectral energy distribution-fitting and the far-infrared/radio correlation. Our observations place strong constraints on the high-frequency radio emission in typical galaxies at high redshift, and provide some of the first insights into what is set to become a key area of study with future radio facilities, such as the Square Kilometer Array Phase 1 and next-generation VLA. 
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  2. null (Ed.)
    We present a multiline survey of the interstellar medium (ISM) in two z  > 6 quasar host galaxies, PJ231−20 ( z  = 6.59) and PJ308−21 ( z  = 6.23), and their two companion galaxies. Observations were carried out using the Atacama Large (sub-)Millimeter Array (ALMA). We targeted 11 transitions including atomic fine-structure lines (FSLs) and molecular lines: [NII] 205 μm , [CI] 369 μm , CO ( J up  = 7, 10, 15, 16), H 2 O 3 12  − 2 21 , 3 21  − 3 12 , 3 03  − 2 12 , and the OH 163 μm doublet. The underlying far-infrared (FIR) continuum samples the Rayleigh-Jeans tail of the respective dust emission. By combining this information with our earlier ALMA [CII] 158 μm observations, we explored the effects of star formation and black hole feedback on the ISM of the galaxies using the CLOUDY radiative transfer models. We estimated dust masses, spectral indexes, IR luminosities, and star-formation rates from the FIR continuum. The analysis of the FSLs indicates that the [CII] 158 μm and [CI] 369 μm emission arises predominantly from the neutral medium in photodissociation regions (PDRs). We find that line deficits agree with those of local luminous IR galaxies. The CO spectral line energy distributions (SLEDs) reveal significant high- J CO excitation in both quasar hosts. Our CO SLED modeling of the quasar PJ231−20 shows that PDRs dominate the molecular mass and CO luminosities for J up  ≤ 7, while the J up  ≥ 10 CO emission is likely driven by X-ray dissociation regions produced by the active galactic nucleus (AGN) at the very center of the quasar host. The J up  > 10 lines are undetected in the other galaxies in our study. The H 2 O 3 21  − 3 12 line detection in the same quasar places this object on the L H 2 O  −  L TIR relation found for low- z sources, thus suggesting that this water vapor transition is predominantly excited by IR pumping. Models of the H 2 O SLED and of the H 2 O-to-OH 163 μm ratio point to PDR contributions with high volume and column density ( n H  ∼ 0.8 × 10 5 cm −3 , N H  = 10 24 cm −2 ) in an intense radiation field. Our analysis suggests a less highly excited medium in the companion galaxies. However, the current data do not allow us to definitively rule out an AGN in these sources, as suggested by previous studies of the same objects. This work demonstrates the power of multiline studies of FIR diagnostics in order to dissect the physical conditions in the first massive galaxies emerging from cosmic dawn. 
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  3. ABSTRACT We present Herschel–PACS spectroscopy of four main-sequence star-forming galaxies at z ∼ 1.5. We detect [OI]63 μm line emission in BzK-21000 at z = 1.5213, and measure a line luminosity, $L_{\rm [O\, {\small I}]63\, \mu m} = (3.9\pm 0.7)\times 10^9$ L⊙. Our PDR modelling of the interstellar medium in BzK-21000 suggests a UV radiation field strength, G ∼ 320G0, and gas density, n ∼ 1800 cm−3, consistent with previous LVG modelling of the molecular CO line excitation. The other three targets in our sample are individually undetected in these data, and we perform a spectral stacking analysis which yields a detection of their average emission and an [O i]63 μm line luminosity, $L_{\rm [O\, {\small I}]63\, \mu m} = (1.1\pm 0.2)\times 10^9$ L⊙. We find that the implied luminosity ratio, $L_{\rm [O\, {\small I}]63\, \mu m}/L_{\rm IR}$, of the undetected BzK-selected star-forming galaxies broadly agrees with that of low-redshift star-forming galaxies, while BzK-21000 has a similar ratio to that of a dusty star-forming galaxy at z ∼ 6. The high [O i]63 μm line luminosities observed in BzK-21000 and the z ∼ 1−3 dusty and sub-mm luminous star-forming galaxies may be associated with extended reservoirs of low density, cool neutral gas. 
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  4. ABSTRACT

    We have carried out the first spatially resolved investigation of the multiphase interstellar medium (ISM) at high redshift, using the z = 4.24 strongly lensed submillimetre galaxy H-ATLASJ142413.9+022303 (ID141). We present high-resolution (down to ∼350 pc) ALMA observations in dust continuum emission and in the CO(7–6), $\rm H_2O (2_{1,1} - 2_{0,2})$, [C i] (1–0), and [C i] (2–1) lines, the latter two allowing us to spatially resolve the cool phase of the ISM for the first time. Our modelling of the kinematics reveals that the system appears to be dominated by a rotationally-supported gas disc with evidence of a nearby perturber. We find that the [C i] (1–0) line has a very different distribution to the other lines, showing the existence of a reservoir of cool gas that might have been missed in studies of other galaxies. We have estimated the mass of the ISM using four different tracers, always obtaining an estimate in the range of $\rm 3.2{\!-\!}3.8 \times 10^{11}\ M_{\odot }$, significantly higher than our dynamical mass estimate of $\rm 0.8{\!-\!}1.3 \times 10^{11}\ M_{\odot }$. We suggest that this conflict and other similar conflicts reported in the literature is because the gas-to-tracer ratios are ≃4 times lower than the Galactic values used to calibrate the ISM in high-redshift galaxies. We demonstrate that this could result from a top-heavy initial mass function and strong chemical evolution. Using a variety of quantitative indicators, we show that, extreme though it is at z = 4.24, ID141 will likely join the population of quiescent galaxies that appears in the Universe at z ∼ 3.

     
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  5. Aims. The dust content of normal galaxies and the dust mass density (DMD) at high- z ( z  > 4) are unconstrained given the source confusion and the sensitivity limitations of previous observations. The ALMA Large Program to INvestigate [CII] at Early times (ALPINE), which targeted 118 ultra-violet (UV)-selected star-forming galaxies at 4.4 <  z  < 5.9, provides a new opportunity to tackle this issue for the first time with a statistically robust dataset. Methods. We exploited the rest-frame far-infrared (FIR) fluxes of 23 galaxies individually detected in their continuum emission, as well as stacked continuum images, to measure the dust content of the 118 UV-selected ALPINE galaxies. We focused on the dust scaling relations and, by comparison with predictions from chemical evolution models, we probed the evolutionary stage of UV-selected galaxies at high- z . By using the observed correlation between the UV luminosity and the dust mass, we estimated the DMD of UV-selected galaxies at z  ∼ 5, weighting the galaxies by means of the UV luminosity function. The derived DMD is compared with the value we estimated from ten ALPINE galaxies blindly detected in the FIR continuum, at the redshift of the ALPINE targets. Results. Our ALMA survey allows the exploration for the first time of the dust content in normal star-forming galaxies at z  > 4 in a statistically robust sample of sources. The comparison of the observed dust scaling relations with chemical evolution models suggests that ALPINE galaxies are not likely progenitors of disc galaxies, but of intermediate- and low-mass proto-spheroids, resulting in present-day bulges of spiral or elliptical galaxies. Interestingly, this conclusion is in line with the independent morphological analysis that shows that the majority (∼70%) of the dust-continuum detected galaxies have a disturbed morphology. The DMD obtained at z  ∼ 5 from UV-selected sources is ∼30% of the value obtained from blind FIR-selected sources, showing that the UV selection misses the most dust-rich, UV-obscured galaxies. 
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  6. Star formation rate (SFR) measurements at z  > 4 have relied mostly on the rest-frame far-ultraviolet (FUV) observations. The corrections for dust attenuation based on the IRX- β relation are highly uncertain and are still debated in the literature. Hence, rest-frame far-infrared (FIR) observations are necessary to constrain the dust-obscured component of the SFR. In this paper, we exploit the rest-frame FIR continuum observations collected by the ALMA Large Program to INvestigate [CII] at Early times (ALPINE) to directly constrain the obscured SFR in galaxies at 4.4 <  z  < 5.9. We used stacks of continuum images to measure average infrared luminosities taking both detected and undetected sources into account. Based on these measurements, we measured the position of the main sequence of star-forming galaxies and the specific SFR (sSFR) at z  ∼ 4.5 and z  ∼ 5.5. We find that the main sequence and sSFR do not significantly evolve between z  ∼ 4.5 and z  ∼ 5.5, as opposed to lower redshifts. We developed a method to derive the obscured SFR density (SFRD) using the stellar masses or FUV-magnitudes as a proxy of FIR fluxes measured on the stacks and combining them with the galaxy stellar mass functions and FUV luminosity functions from the literature. We obtain consistent results independent of the chosen proxy. We find that the obscured fraction of SFRD is decreasing with increasing redshift, but even at z  ∼ 5.5 it constitutes around 61% of the total SFRD. 
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  7. ABSTRACT We measure the 850-μm source densities of 46 candidate protoclusters selected from the Planck high-z catalogue (PHz) and the Planck Catalogue of Compact Sources (PCCS) that were followed up with Herschel-SPIRE and SCUBA-2. This paper aims to search for overdensities of 850-μm sources in order to select the fields that are most likely to be genuine protoclusters. Of the 46 candidate protoclusters, 25 have significant overdensities (>5 times the field counts), 11 have intermediate overdensities (3–5 times the field counts), and 10 have no overdensity (<3 times the field counts) of 850-μm sources. We find that the enhanced number densities are unlikely to be the result of sample variance. Compared with the number counts of another sample selected from Planck’s compact source catalogues, this [PHz + PCCS]-selected sample has a higher fraction of candidate protoclusters with significant overdensities, though both samples show overdensities of 850-μm sources above intermediate level. Based on the estimated star formation rate densities (SFRDs), we suggest that both samples can efficiently select protoclusters with starbursting galaxies near the redshift at which the global field SFRD peaks (2 < z < 3). Based on the confirmation of overdensities found here, future follow-up observations on other PHz targets may greatly increase the number of genuine dusty star-forming galaxy-rich clusters/protoclusters. 
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  8. Abstract The Cosmic Evolution Survey (COSMOS) has become a cornerstone of extragalactic astronomy. Since the last public catalog in 2015, a wealth of new imaging and spectroscopic data have been collected in the COSMOS field. This paper describes the collection, processing, and analysis of these new imaging data to produce a new reference photometric redshift catalog. Source detection and multiwavelength photometry are performed for 1.7 million sources across the 2 deg 2 of the COSMOS field, ∼966,000 of which are measured with all available broadband data using both traditional aperture photometric methods and a new profile-fitting photometric extraction tool, The Farmer , which we have developed. A detailed comparison of the two resulting photometric catalogs is presented. Photometric redshifts are computed for all sources in each catalog utilizing two independent photometric redshift codes. Finally, a comparison is made between the performance of the photometric methodologies and of the redshift codes to demonstrate an exceptional degree of self-consistency in the resulting photometric redshifts. The i < 21 sources have subpercent photometric redshift accuracy and even the faintest sources at 25 < i < 27 reach a precision of 5%. Finally, these results are discussed in the context of previous, current, and future surveys in the COSMOS field. Compared to COSMOS2015, it reaches the same photometric redshift precision at almost one magnitude deeper. Both photometric catalogs and their photometric redshift solutions and physical parameters will be made available through the usual astronomical archive systems (ESO Phase 3, IPAC-IRSA, and CDS). 
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