A massive reservoir of low-excitation molecular gas at high redshift

Molecular hydrogen is an important component of galaxies because it fuels star formation and accretion onto AGN, the two processes that generate the large infrared luminosities of gas-rich galaxies. Observations of spectral-line emission from the tracer molecule CO are used to probe the properties of this gas. But the lines that have been studied in the local Universe, mostly the lower rotational transitions of J = 1-0 and J = 2-1, have hitherto been unobservable in high-redshift galaxies. Instead, higher transitions have been used, although the densities and temperatures required to excite these higher transitions may not be reached by much of the gas. As a result, past observations may have underestimated the total amount of molecular gas by a substantial amount. Here we report the discovery of large amounts of low-excitation molecular gas around the infrared-luminous quasar, APM 08279+5255 at z = 3.91, using the two lowest excitation lines of 12CO (J = 1-0 and J = 2-1). The maps confirm the presence of hot and dense gas near the nucleus, and reveal an extended reservoir of molecular gas with low excitation that is 10 to 100 times more massive than the gas traced by higher-excitation observations. This raises the possibility that significant amounts of low-excitation molecular gas may lurk in the environments of high-redshift (z > 3) galaxies.Comment: To appear as a Letter to Nature, 4th January 200

Molecular and atomic gas in dust lane early-type galaxies - I : Low star-formation efficiencies in minor merger remnants

In this work we present IRAM-30m telescope observations of a sample of bulge-dominated galaxies with large dust lanes, which have had a recent minor merger. We find these galaxies are very gas rich, with H2 masses between 4x10^8 and 2x10^10 Msun. We use these molecular gas masses, combined with atomic gas masses from an accompanying paper, to calculate gas-to-dust and gas-to-stellar mass ratios. The gas-to-dust ratios of our sample objects vary widely (between ~50 and 750), suggesting many objects have low gas-phase metallicities, and thus that the gas has been accreted through a recent merger with a lower mass companion. We calculate the implied minor companion masses and gas fractions, finding a median predicted stellar mass ratio of ~40:1. The minor companion likely had masses between ~10^7 - 10^10 Msun. The implied merger mass ratios are consistent with the expectation for low redshift gas-rich mergers from simulations. We then go on to present evidence that (no matter which star-formation rate indicator is used) our sample objects have very low star-formation efficiencies (star-formation rate per unit gas mass), lower even than the early-type galaxies from ATLAS3D which already show a suppression. This suggests that minor mergers can actually suppress star-formation activity. We discuss mechanisms that could cause such a suppression, include dynamical effects induced by the minor merger.Peer reviewe

The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14 happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov 2017 (this is the "post-print" and "post-proofs" version; minor corrections only from v1, and most of errors found in proofs corrected

Gas and Dust in the Extremely Red Object ERO J164502+4626.4

We report the first detection of the lowest CO transition in a sub-millimetre bright galaxy and extremely red object (ERO) at z = 1.44 using the Very Large Array. The total J = 1 - 0 line luminosity of ERO J164502+4626.4 is (7+-1) x 10^{10} K km s^{-1} pc^2, which yields a total molecular gas mass of ~6 x 10^{10} Msun. We also present a map of the 850-um continuum emission obtained using SCUBA, from which we infer a far-IR luminosity and dust mass of L_FIR ~ 9 x 10^{12} Lsun and M_d ~ 9 x 10^{8} Msun. We find tentative evidence that the CO and sub-mm dust emission is extended over several tens of kpc. If confirmed by high-resolution imaging, this implies that ERO J164502+4626.4 is not simply a high redshift counterpart of a typical Ultra Luminous Infrared Galaxy (ULIRG).Comment: 21 pages, 2 figures, accepted for publication in Ap

The m.13051G>A mitochondrial DNA mutation results in variable neurology and activated mitophagy

Maternally-inherited mitochondrial DNA (mtDNA) mutations cause symptoms of Leber’s hereditary optic neuropathy (LHON) in~ 1 in 30,000 individuals. Most of the affected individuals lack respiratory chain defects and there is no proven prophylactic treatment. We identified two families (Figure 1A) and one singleton case (Appendix e-1) harbouring the m.13051G>A pathogenic mtDNA mutation. This mutation was homoplasmic (Figure e-1) but no respiratory chain defect was apparent in skeletal muscle (Figure e-2, Table e-1). Three children were severely affected with lactic acidosis, two with Leigh syndrome (Patient 1 and 2; Figure 1B) and one with a Leigh-like phenotype (Patient 5). Previous authors have shown that mtDNA and mitochondrial mass are increased in individuals harbouring LHON mutations. They suggested that an up-regulation of mitochondrial biogenesis is protective, as the highest mitochondrial content was found in symptom-free carriers. We believe this increase in biogenesis reflects heightened mitochondrial turnover and therefore investigated mitophagy, a cellular mechanism whereby redundant or dysfunctional mitochondria are recycled

Breaking the "Redshift Deadlock" -- II: The redshift distribution for the submillimetre population of galaxies

In this paper we apply our Monte-Carlo photometric-redshift technique, introduced in paper I (Hughes et al. 2002), to the multi-wavelength data available for 77 galaxies selected at 850um and 1.25mm. We calculate a probability distribution for the redshift of each galaxy, which includes a detailed treatment of the observational errors and uncertainties in the evolutionary model. The cumulative redshift distribution of the submillimetre galaxy population that we present in this paper, based on 50 galaxies found in wide-area SCUBA surveys, is asymmetric, and broader than those published elsewhere, with a significant high-z tail for some of the evolutionary models considered. Approximately 40 to 90 per cent of the sub-mm population is expected to have redshifts in the interval 2 < z < 4. Whilst this result is completely consistent with earlier estimates for the sub-mm galaxy population, we also show that the colours of many (< 50 per cent) individual sub-mm sources, detected only at 850um with non-detections at other wavelengths, are consistent with those of starburst galaxies that lie at extreme redshifts, z > 4. Spectroscopic confirmation of the redshifts, through the detection of rest-frame FIR--mm wavelength molecular transition-lines, will ultimately calibrate the accuracy of this technique. We use the redshift probability distribution of HDF850.1 to illustrate the ability of the method to guide the choice of possible frequency tunings on the broad-band spectroscopic receivers that equip the large aperture single-dish mm and cm-wavelength telescopes.Comment: Accepted in MNRAS, 16 pages, 12 figures, an appendix with 25 additional pages of figures is available at http://www.inaoep.mx/~itziar/papers/dlIIapp.pd

The Canada-UK Deep Submillimetre Survey VIII: Source Identifications in the 3-hour field

We present optical, near-infrared and radio observations of the 3-hour field of the Canada-UK Deep Submillimetre Survey. Of the 27 submillimetre sources in the field, nine have secure identifications with either a radio source or a near-IR source. We show that the percentage of sources with secure identifications in the CUDSS is consistent with that found for the bright `8 mJy' submillimetre survey, once allowance is made for the different submillimetre and radio flux limits. Of the 14 secure identifications in the two CUDSS fields, eight are VROs or EROs, five have colours typical of normal galaxies, and one is a radio source which has not yet been detected at optical/near-IR wavelengths. Eleven of the identifications have optical/near-IR structures which are either disturbed or have some peculiarity which suggests that the host galaxy is part of an interacting system. One difference between the CUDSS results and the results from the 8-mJy survey is the large number of low-redshift objects in the CUDSS; we give several arguments why these are genuine low-redshift submillimetre sources rather than being gravitational lenses which are gravitationally amplifying a high-$z$ submillimetre source. We construct a $K-z$ diagram for various classes of high-redshift galaxy and show that the SCUBA galaxies are on average less luminous than classical radio galaxies, but are very similar in both their optical/IR luminosities and their colours to the host galaxies of the radio sources detected in $\mu$Jy radio surveys.Comment: accepted for publication in MNRAS, 18 pages, full-resolution versions of Figure 1 and 2 can be found at http://www.astro.cf.ac.uk/groups/cosmo/papers.htm

The mysterious morphology of MRC0943-242 as revealed by ALMA and MUSE

© 2016 ESO. We present a pilot study of the z = 2.923 radio galaxy MRC0943-242, where we combine information from ALMA and MUSE data cubes for the first time. Even with modest integration times, we disentangle the AGN and starburst dominated components. These data reveal a highly complex morphology as the AGN, starburst, and molecular gas components show up as widely separated sources in dust continuum, optical continuum, and CO line emission observations. CO(1-0) and CO(8-7) line emission suggest that there is a molecular gas reservoir offset from both the dust and the optical continuum that is located ~90 kpc from the AGN. The UV line emission has a complex structure in emission and absorption. The line emission is mostly due to a large scale ionisation cone energised by the AGN, and a Lya emitting bridge of gas between the radio galaxy and a heavily star-forming set of components. Strangely, the ionisation cone has no Lya emission. We find this is due to an optically thick layer of neutral gas with unity covering fraction spread out over a region of at least ~100 kpc from the AGN. Other less thick absorption components are associated with Lya emitting gas within a few tens of kpc from the radio galaxy and are connected by a bridge of emission. We speculate that this linear structure of dust, Lya and CO emission, and the redshifted absorption seen in the circum nuclear region may represent an accretion flow feeding gas into this massive AGN host galaxy

Global chemical effects of the microbiome include new bile-acid conjugations

A mosaic of cross-phylum chemical interactions occurs between all metazoans and their microbiomes. A number of molecular families that are known to be produced by the microbiome have a marked effect on the balance between health and disease. Considering the diversity of the human microbiome (which numbers over 40,000 operational taxonomic units), the effect of the microbiome on the chemistry of an entire animal remains underexplored. Here we use mass spectrometry informatics and data visualization approaches to provide an assessment of the effects of the microbiome on the chemistry of an entire mammal by comparing metabolomics data from germ-free and specific-pathogen-free mice. We found that the microbiota affects the chemistry of all organs. This included the amino acid conjugations of host bile acids that were used to produce phenylalanocholic acid, tyrosocholic acid and leucocholic acid, which have not previously been characterized despite extensive research on bile-acid chemistry. These bile-acid conjugates were also found in humans, and were enriched in patients with inflammatory bowel disease or cystic fibrosis. These compounds agonized the farnesoid X receptor in vitro, and mice gavaged with the compounds showed reduced expression of bile-acid synthesis genes in vivo. Further studies are required to confirm whether these compounds have a physiological role in the host, and whether they contribute to gut diseases that are associated with microbiome dysbiosis

Exploring a SNR/Molecular Cloud Association Within HESS J1745-303

HESS J1745-303 is an extended, unidentified VHE (very high energy) gamma-ray source discovered using HESS in the Galactic Plane Survey. Since no obvious counterpart has previously been found in longer-wavelength data, the processes that power the VHE emission are not well understood. Combining the latest VHE data with recent XMM-Newton observations and a variety of source catalogs and lower-energy survey data, we attempt to match (from an energetic and positional standpoint) the various parts of the emission of HESS J1745-303 with possible candidates. Though no single counterpart is found to fully explain the VHE emission, we postulate that at least a fraction of the VHE source may be explained by a supernova-remnant/molecular-cloud association and/or a high-spin-down-flux pulsar.Comment: 11 pages, 4 figures, Accepted for publication in Astronomy & Astrophysic