D. Riechers - Cornell University

D. Riechers
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D. Riechers
Cornell University
United States

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Astrophysics of Galaxies (50)
Cosmology and Nongalactic Astrophysics (12)

Publications Authored By D. Riechers

The existence of massive ($10^{11}$ solar masses) elliptical galaxies by redshift z~4 (when the Universe was 1.5 billion years old) necessitates the presence of galaxies with star-formation rates exceeding 100 solar masses per year at z>6 (corresponding to an age of the Universe of less than 1 billion years). Surveys have discovered hundreds of galaxies at these early cosmic epochs, but their star-formation rates are more than an order of magnitude lower. Read More

We present the final data release of the APEX low-redshift legacy survey for molecular gas (ALLSMOG), comprising CO(2-1) emission line observations of 88 nearby, low-mass (10^8.5Read More

We have modelled ALMA imaging of six strong gravitationally lensed galaxies detected by the Herschel Space Observatory. Both the cleaned image plane data and the directly observed interferometric visibilities have been modelled, enabling comparison of both approaches. In the majority of cases, the recovered lens models are consistent between modelling methods, although a few systems show some small differences, particularly those with more poorly resolved Einstein rings. Read More

The identification of high-redshift massive galaxies with old stellar populations may pose challenges to some models of galaxy formation. However, to securely classify a galaxy as quiescent, it is necessary to exclude significant ongoing star formation, something that can be challenging to achieve at high redshift. In this letter, we analyse deep ALMA/870um and SCUBA-2/450um imaging of the claimed "post-starburst" galaxy ZF-20115 at z=3. Read More

We report observations of dense molecular gas in the star-forming galaxy EGS 13004291 (z=1.197) using the Plateau de Bure Interferometer. We tentatively detect HCN and HNC (J=2-1) emission when stacked together at ~4sigma significance, yielding line luminosities of L_HCN (J=2-1) =(9 +/- 3) x 10^9 K km s^-1 pc^2 and L_HNC (J=2-1)= (5 +/-2) x 10^9 K km s^-1 pc^2 respectively. Read More

We report observations of CO(J=2-1) and CO(J=3-2) line emission towards the quadruply-lensed quasar RXS J1131-1231 at z = 0.654 obtained using the Plateau de Bure Interferometer (PdBI) and the Combined Array for Research in Millimeter-wave Astronomy (CARMA). Our lens modeling shows that the asymmetry in the double-horned CO(J = 2-1) line profile is mainly a result of differential lensing, where the magnification factor varies from ~3 to ~9 across different kinematic components. Read More

We present ALMA and VLA detections of the dense molecular gas tracers HCN, HCO$^+$ and HNC in two lensed, high-redshift starbursts selected from the {\it Herschel}-ATLAS survey: {\it H}-ATLAS\,J090740.0$-$004200 (SDP.9, $z \sim 1. Read More

We present the detection of four far-infrared fine-structure oxygen lines, as well as strong upper limits for the CO(2-1) and [N II] 205 um lines, in 3C 368, a well-studied radio-loud galaxy at z = 1.131. These new oxygen lines, taken in conjunction with previously observed neon and carbon fine-structure lines, suggest a powerful active galactic nucleus (AGN), accompanied by vigorous and extended star formation. Read More

Affiliations: 1Centre for Extragalactic Astronomy, Durham University, 2University of California, Irvine, 3University of California, Irvine, 4University of Edinburgh, 5Imperial College London, 6Instituto de Astrofísica de Canarias, 7University of Edinburgh, 8University of Nottingham, 9Cardiff University, 10Virginia Tech, 11University of Nottingham, 12Universidad de Valparaóso, 13University of Edinburgh, 14University of Edinburgh, 15University of Edinburgh, 16Cornell University, 17Oxford Astrophysics, University of Oxford, 18University of British Columbia, 19Cardiff University, 20SRON Netherlands Institute for Space Research, 21Leiden University, 22Cardiff University, 23Herschel Science Centre, 24Oxford Astrophysics, University of Oxford

Submillimeter galaxies (SMGs) at $z\gtrsim1$ are luminous in the far-infrared and have star-formation rates, SFR, of hundreds to thousands of solar masses per year. However, it is unclear whether they are true analogs of local ULIRGs or whether the mode of their star formation is more similar to that in local disk galaxies. We target these questions by using Herschel-PACS to examine the conditions in the interstellar medium (ISM) in far-infrared luminous SMGs at z~1-4. Read More

We present the results of combined deep Keck/NIRC2, HST/WFC3 near-infrared and Herschel far infrared observations of an extremely star forming dusty lensed galaxy identified from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS J133542.9+300401). The galaxy is gravitationally lensed by a massive WISE identified galaxy cluster at $z\sim1$. Read More

We present a sample of 80 candidate strongly lensed galaxies with flux density above 100mJy at 500{\mu}m extracted from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), over an area of 600 square degrees. Available imaging and spectroscopic data allow us to confirm the strong lensing in 20 cases and to reject it in one case. For other 8 objects the lensing scenario is strongly supported by the presence of two sources along the same line of sight with distinct photometric redshifts. Read More

Until recently, only a handful of dusty, star-forming galaxies (DSFGs) were known at $z>4$, most of them significantly amplified by gravitational lensing. Here, we have increased the number of such DSFGs substantially, selecting galaxies from the uniquely wide 250-, 350- and 500-$\mu$m Herschel-ATLAS imaging survey on the basis of their extremely red far-infrared colors and faint 350- and 500-$\mu$m flux densities - ergo they are expected to be largely unlensed, luminous, rare and very distant. The addition of ground-based continuum photometry at longer wavelengths from the JCMT and APEX allows us to identify the dust peak in their SEDs, better constraining their redshifts. Read More

Observations using the 7 mm receiver system on the Australia Telescope Compact Array have revealed large reservoirs of molecular gas in two high-redshift radio galaxies: HATLAS J090426.9+015448 (z = 2.37) and HATLAS J140930. Read More

We present Karl G Jansky Very Large Array (VLA) observations of CO(2-1) line emission and rest-frame 250GHz continuum emission of the Hyper-Luminous IR Galaxies (HyLIRGs) BRI1202-0725 (z=4.69) and BRI1335-0417 (z=4.41), with an angular resolution as high as 0. Read More

In this paper we use ASPECS, the ALMA Spectroscopic Survey in the {\em Hubble} Ultra Deep Field (UDF) in band 3 and band 6, to place blind constraints on the CO luminosity function and the evolution of the cosmic molecular gas density as a function of redshift up to $z\sim 4.5$. This study is based on galaxies that have been solely selected through their CO emission and not through any other property. Read More

We study the molecular gas properties of high-$z$ galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets a $\sim1$ arcmin$^2$ region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3mm and 1mm bands. Of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. Among these, 11 have infrared luminosities $L_{\rm{}IR}>10^{11}$ L$_\odot$, i. Read More

We present a search for [CII] line and dust continuum emission from optical dropout galaxies at $z>6$ using ASPECS, our ALMA Spectroscopic Survey in the Hubble Ultra-Deep Field (UDF). Our observations, which cover the frequency range $212-272$ GHz, encompass approximately the range $6Read More

We present direct estimates of the mean sky brightness temperature in observing bands around 99GHz and 242GHz due to line emission from distant galaxies. These values are calculated from the summed line emission observed in a blind, deep survey for specrtal line emission from high redshift galaxies using ALMA (the 'ASPECS' survey). In the 99 GHz band, the mean brightness will be dominated by rotational transitions of CO from intermediate and high redshift galaxies. Read More

(abridged) We report rest-frame submillimeter H2O emission line observations of 11 HyLIRGs/ULIRGs at z~2-4 selected among the brightest lensed galaxies discovered in the Herschel-ATLAS. Using the IRAM NOEMA, we have detected 14 new H2O emission lines. The apparent luminosities of the H2O emission lines are $\mu L_{\rm{H_2O}} \sim 6-21 \times 10^8 L_\odot$, with velocity-integrated line fluxes ranging from 4-15 Jy km s$^{-1}$. Read More

We report interferometric measurements of [NII] 205 um fine-structure line emission from a representative sample of three galaxies at z=5-6 using the Atacama Large (sub)Millimeter Array (ALMA). These galaxies were previously detected in [CII] and far-infrared continuum emission and span almost two orders of magnitude in star formation rate (SFR). Our results show at least two different regimes of ionized inter-stellar medium properties for galaxies in the first billion years of cosmic time, separated by their L_[CII]/L_[NII] ratio. Read More

We present CO(1-0) observations obtained at the Karl G. Jansky Very Large Array (VLA) for 14 z~2 galaxies with existing CO(3-2) measurements, including 11 galaxies which contain active galactic nuclei (AGN) and three submillimeter galaxies (SMGs). We combine this sample with an additional 15 z~2 galaxies from the literature that have both CO(1-0) and CO(3-2) measurements in order to evaluate differences in CO excitation between SMGs and AGN host galaxies, measure the effects of CO excitation on the derived molecular gas properties of these populations, and to look for correlations between the molecular gas excitation and other physical parameters. Read More

We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of 9 star-forming (5 < SFR < 70 Msun/yr) z ~ 6 galaxies for which high-quality spectra of the [CII]158 micron line has been previously obtained with ALMA. We first fit each line with a Gaussian function and compute the residuals by subtracting the best fitting model from the data. We combine the residuals of all sample galaxies and find that the total signal is characterized by a flux excess that can be ascribed to broad wings of the [CII] line, which we interpret as a signature of starburst-driven outflows. Read More

Exploiting the sensitivity and spatial resolution of the Atacama Large Millimeter/submillimeter Array (ALMA), we have studied the morphology and the physical scale of the interstellar medium - both gas and dust - in SGP38326, an unlensed pair of interacting starbursts at $z= 4.425$. SGP38326 is the most luminous star bursting system known at $z > 4$ with an IR-derived ${\rm SFR \sim 4300 \,} M_\odot \, {\rm yr}^{-1}$. Read More

We report the detection of CO(J=3-2) line emission in the strongly-lensed submillimeter galaxy (SMG) SMM J0939+8315 at z=2.221, using the Combined Array for Research in Millimeter-wave Astronomy. SMM J0939+8315 hosts a type-2 quasar, and is gravitationally lensed by the radio galaxy 3C220. Read More

We present a list of candidate gravitationally lensed dusty star-forming galaxies (DSFGs) from the HerMES Large Mode Survey (HeLMS) and the Herschel Stripe 82 Survey (HerS). Together, these partially overlapping surveys cover 372 deg$^{2}$ on the sky. After removing local spiral galaxies and known radio-loud blazars, our candidate list of lensed DSFGs is composed of 77 sources with 500 $\mu$m flux densities ($S_{500}$) greater than 100 mJy. Read More

Selecting sources with rising flux densities towards longer wavelengths from Herschel/SPIRE maps is an efficient way to produce a catalogue rich in high-redshift (z > 4) dusty star-forming galaxies. The effectiveness of this approach has already been confirmed by spectroscopic follow-up observations, but the previously available catalogues made this way are limited by small survey areas. Here we apply a map-based search method to 274 deg$^2$ of the HerMES Large Mode Survey (HeLMS) and create a catalogue of 477 objects with SPIRE flux densities $S_{500} > S_{350} >S_{250}$ and a $5 \sigma$ cut-off $S_{500} > $ 52 mJy. Read More

We present a source-plane reconstruction of a ${\it Herschel}$ and ${\it Planck}$-detected gravitationally-lensed dusty star-forming galaxy (DSFG) at $z=1.68$ using {\it Hubble}, Sub-millimeter Array (SMA), and Keck observations. The background sub-millimeter galaxy (SMG) is strongly lensed by a foreground galaxy cluster at $z=0. Read More

We show that the use of red colour as the basis for selecting candidate high redshift dusty galaxies from surveys made with Herschel has proved highly successful. The highest redshift such object, HFLS3, lies at z=6.34 and numerous other sources have been found. Read More

Affiliations: 1UT Austin, 2NRAO Charlottesville, 3NRAO Charlottesville, 4NRAO Socorro, 5UW-Madison, 6Haverford, 7NRAO Socorro, 8Carnegie Observatories, 9Swinburne, 10CSIC-INTA, 11ESO, 12CSIRO, 13Tokyo, 14IPAC, 15Cornell, 16CEA Saclay, 17MPIA

The Next-Generation Very Large Array (ngVLA) will be critical for understanding how galaxies are built and evolve at the earliest epochs. The sensitivity and frequency coverage will allow for the detection of cold gas and dust in `normal' distant galaxies, including the low-J transitions of molecular gas tracers such as CO, HNC, and HCO+; synchrotron and free-free continuum emission; and even the exciting possibility of thermal dust emission at the highest (z~7) redshifts. In particular, by enabling the total molecular gas reservoirs to be traced to unprecedented sensitivities across a huge range of epochs simultaneously -- something no other radio or submillimeter facility will be capable of -- the detection of the crucial low-J transitions of CO in a diverse body of galaxies will be the cornerstone of ngVLA's contribution to high-redshift galaxy evolution science. Read More

We present Karl G. Jansky Very Large Array (VLA) observations of the CO ($J = 2 \rightarrow 1$) line emission towards the $z = 6.419$ quasar SDSS J$114816. Read More

We present the rest-frame optical spectral energy distribution and stellar masses of six Herschel- selected gravitationally lensed dusty, star-forming galaxies (DSFGs) at 1 < z < 3. These galaxies were first identified with Herschel/SPIRE imaging data from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). The targets were observed with Spitzer/IRAC at 3. Read More

The Herschel Multi-tiered Extragalactic Survey (HerMES) has identified large numbers of dusty star-forming galaxies (DSFGs) over a wide range in redshift. A detailed understanding of these DSFGs is hampered by the limited spatial resolution of Herschel. We present 870um 0. Read More

We describe the search for Lyman-break galaxies (LBGs) near the sub-millimeter bright starburst galaxy HFLS3 at $z$$=$6.34 and a study on the environment of this massive galaxy during the end of reionization.We performed two independent selections of LBGs on images obtained with the \textit{Gran Telescopio Canarias} (GTC) and the \textit{Hubble Space Telescope} (HST) by combining non-detections in bands blueward of the Lyman-break and color selection. Read More

Evolution in the measured rest frame ultraviolet spectral slope and ultraviolet to optical flux ratios indicate a rapid evolution in the dust obscuration of galaxies during the first 3 billion years of cosmic time (z>4). This evolution implies a change in the average interstellar medium properties, but the measurements are systematically uncertain due to untested assumptions, and the inability to measure heavily obscured regions of the galaxies. Previous attempts to directly measure the interstellar medium in normal galaxies at these redshifts have failed for a number of reasons with one notable exception. Read More

We explore the behaviour of [CII]-157.74um forbidden fine-structure line observed in a sample of 28 galaxies selected from ~50deg^2 of the H-ATLAS survey. The sample is restricted to galaxies with flux densities higher than S_160um>150mJy and optical spectra from the GAMA survey at 0. Read More

We present Hubble Space Telescope (HST) WFC3 imaging and grism spectroscopy observations of the {\it Herschel}-selected gravitationally-lensed starburst galaxy HATLASJ1429-0028. The lensing system consists of an edge-on foreground disk galaxy at $z=0.218$ with a nearly complete Einstein ring of the infrared luminous galaxy at $z=1. Read More

Affiliations: 1SKAO, 2MPIA, 3NRAO, 4MPIA, 5Universidad Diego Portales, 6CASS, 7NRAO, 8Caltech, 9Cornell University, 10University of Sussex, 11KIAA, Peking

The Square Kilometre Array will be a revolutionary instrument for the study of gas in the distant Universe. SKA1 will have sufficient sensitivity to detect and image atomic 21 cm HI in individual galaxies at significant cosmological distances, complementing ongoing ALMA imaging of redshifted high-J CO line emission and far-infrared interstellar medium lines such as [CII] 157.7 um. Read More

We study the physical properties of a sample of 6 SMGs in the COSMOS field, spectroscopically confirmed to lie at z>4. We use new GMRT 325 MHz and 3 GHz JVLA data to probe the rest-frame 1.4 GHz emission at z=4, and to estimate the sizes of the star-forming (SF) regions of these sources, resp. Read More

We present high-resolution observations of the 880 $\mu$m (rest-frame FIR) continuum emission in the z$=$4.05 submillimeter galaxy GN20 from the IRAM Plateau de Bure Interferometer (PdBI). These data resolve the obscured star formation in this unlensed galaxy on scales of 0. Read More

The broad spectral bandwidth at mm and cm-wavelengths provided by the recent upgrades to the Karl G. Jansky Very Large Array (VLA) has made it possible to conduct unbiased searches for molecular CO line emission at redshifts, z > 1.31. Read More

We investigate the CO excitation of normal star forming disk galaxies at z=1.5 using IRAM PdBI observations of the CO[2-1], CO[3-2] and CO[5-4] transitions for 4 galaxies, including VLA observations of CO[1-0] for 3 of them, with the aim of constraining the average state of H2 gas. Exploiting prior knowledge of the velocity range, spatial extent and size of the CO emission we measure reliable line fluxes with S/N>4-7 for individual transitions. Read More

We present Herschel far-IR photometry and spectroscopy as well as ground based CO observations of an intermediate redshift (0.21 < z < 0.88) sample of Herschel-selected (ultra)-luminous infrared galaxies (L_IR > 10^11. Read More