arXiv subjects

Paul van der Werf

Publications and source records attributed to Paul van der Werf.

At least 127 records · Page 7Linked to original sources

arXiv2013

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: High resolution 870um source counts

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.

astro-ph.CO↗

arXiv2012

The molecular gas in Luminous Infrared Galaxies: a new emergent picture

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 ....

astro-ph.GA↗

arXiv2012

An ALMA survey of Sub-millimetre Galaxies in the Extended Chandra Deep Field South: Detection of [C II] at z=4.4

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.

astro-ph.CO↗

arXiv2012

Herschel-PACS observations of [OI]63um towards submillimetre galaxies at z~1

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 1.1 3, 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.

astro-ph.CO↗

arXiv2012

Panchromatic Estimation of Star Formation Rates in BzK Galaxies at 1<z<3

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.

astro-ph.CO↗

arXiv2012

The Infrared Properties of Sources Matched in the WISE all-sky and Herschel-ATLAS Surveys

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.

astro-ph.CO↗

arXiv2012

The molecular gas in Luminous Infrared Galaxies I: CO lines, extreme physical conditions, and their drivers

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.....

astro-ph.CO↗

arXiv2012

The molecular gas in Luminous Infrared Galaxies II: extreme physical conditions, and their effects on the X_{co} factor

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.

astro-ph.CO↗

arXiv2010

A joint analysis of BLAST 250--500um and LABOCA 870um observations in the Extended Chandra Deep Field South

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 β=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.

astro-ph.CO↗

arXiv2010

Detection of molecular gas in a distant submillimetre galaxy at z=4.76 with ATCA

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.

astro-ph.CO↗

arXiv2010

Integral-field near-infrared spectroscopy of two blue dwarf galaxies: NGC 5253 and He 2-10

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.

astro-ph.CO↗

arXiv2010

Resolving debris discs in the far-infrared: early highlights from the DEBRIS survey

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.

astro-ph.SR↗

arXiv2010

CO Spectral Line Energy Distributions of IR-luminous galaxies and AGN

We report on new sensitive CO J=6-5 line observations of several luminous infrared Galaxies (LIRGs: L$_{\rm IR}$(8-1000$μ$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: ...

astro-ph.CO↗

arXiv2010

CO J=6--5 in Arp 220: strong effects of dust on high-J CO lines

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.

astro-ph.CO↗

arXiv2009

A submillimetre galaxy at z=4.76 in the LABOCA survey of the Extended Chandra Deep Field South

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.

astro-ph.GA↗

arXiv2008

METIS - the Mid-infrared E-ELT Imager and Spectrograph

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.

astro-ph↗

arXiv2007

A large CO and HCN line survey of Luminous Infrared Galaxies

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 $\rm 158 μm$, 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.

astro-ph↗

arXiv2006

Deep Submillimeter Observations of Two Lyman-alpha Emitting Galaxies at z~6.5

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<z<5.

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