Search

We present a speculative exploration of the properties of a proposed new Dark Matter (DM) candidate in a heretofore under-explored region of parameter space. Our proposed ultra-cold candidatae has been a matter of speculation for some time,and has recently been tentatively identified via direct-detection. While unconventional, demonstrated existence of this DM candidate would have wide-ranging implications for a range of fields, from particle cosmology to exobiology and the Search for Extraterrestrial Life (SETI)., Comment: 5 pages, 2 figures. Submitted to Vatican Publishing House

We investigate the relationship between the star formation rate (SFR), stellar mass ($M_*$) and molecular gas mass ($M_{H_2}$) for local star-forming galaxies. We further investigate these relationships for high-z (z=1-3) galaxies and for the hosts of a local sample of Active Galactic Nuclei (AGN). We explore which of these dependencies are intrinsic and which are an indirect by-product by employing partial correlation coefficients and random forest regression. We find that for local star-forming galaxies, high-z galaxies, and AGN host galaxies, the Schmidt-Kennicutt relation (SK, between $M_{H_2}$ and SFR), and the Molecular Gas Main Sequence (MGMS, between $M_{H_2}$ and $M_*$) are intrinsic primary relations, while the relationship between $M_*$ and SFR, i.e. the Star-Forming Main Sequence (SFMS), is an indirect by-product of the former two. Hence the Star-Forming Main Sequence is not a fundamental scaling relation for local or high-redshift galaxies. We find evidence for both the evolution of the MGMS and SK relation over cosmic time, where, at a given stellar mass, the higher the redshift, the greater the molecular gas mass and the star formation efficiency. We offer a parameterisation of both the MGMS and SK relation's evolution with redshift, showing how they combine to form the observed evolution of the SFMS. In addition, we find that the local AGN host galaxies follow an AGN-MGMS relation (as well as a AGN-SK relation), where the MGMS is offset to lower $M_{H_2}$ for a given $M_*$ compared to local SF galaxies., Comment: 16 pages, 14 figures, Accepted for publication in MNRAS

We present the first data release of the MaNGA-ARO Survey of CO Targets (MASCOT), an ESO Public Spectroscopic Survey conducted at the Arizona Radio Observatory (ARO). We measure the CO(1-0) line emission in a sample of 187 nearby galaxies selected from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey that has obtained integral field unit (IFU) spectroscopy for a sample of ~ 10,000 galaxies at low redshift. The main goal of MASCOT is to probe the molecular gas content of star-forming galaxies with stellar masses > 10^9.5 M_solar and with associated MaNGA IFU observations and well-constrained quantities like stellar masses, star formation rates and metallicities. In this paper we present the first results of the MASCOT survey, providing integrated CO(1-0) measurements that cover several effective radii of the galaxy and present CO luminosities, CO kinematics, and estimated H2 gas masses. We observe that the decline of galaxy star formation rate with respect to the star formation main sequence (SFMS) increases with the decrease of molecular gas and with a reduced star formation efficiency, in agreement with results of other integrated studies. Relating the molecular gas mass fractions with the slope of the stellar age gradients inferred from the MaNGA observations, we find that galaxies with lower molecular gas mass fractions tend to show older stellar populations close to the galactic center, while the opposite is true for galaxies with higher molecular gas mass fractions, providing tentative evidence for inside-out quenching., Comment: 12 pages plus 20 pages of data tables and figures, accepted to MNRAS, data will be released as supplementary material with the paper as well as on the MASCOT website (https://wwwstaff.ari.uni-heidelberg.de/dwylezalek/mascot.html)

The ALMaQUEST (ALMA-MaNGA QUEnching and STar formation) survey is a program with spatially-resolved $^{12}$CO(1-0) measurements obtained with the Atacama Large Millimeter Array (ALMA) for 46 galaxies selected from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) DR15 optical integral-field spectroscopic survey. The aim of the ALMaQUEST survey is to investigate the dependence of star formation activity on the cold molecular gas content at kpc scales in nearby galaxies. The sample consists of galaxies spanning a wide range in specific star formation rate (sSFR), including starburst (SB), main-sequence (MS), and green valley (GV) galaxies. In this paper, we present the sample selection and characteristics of the ALMA observations, and showcase some of the key results enabled by the combination of spatially-matched stellar populations and gas measurements. Considering the global (aperture-matched) stellar mass, molecular gas mass, and star formation rate of the sample, we find that the sSFR depends on both the star formation efficiency (SFE) and the molecular gas fraction ($f_{\rm H_{2}}$), although the correlation with the latter is slightly weaker. Furthermore, the dependence of sSFR on the molecular gas content (SFE or $f_{\rm H_{2}}$) is stronger than that on either the atomic gas fraction or the molecular-to-atomic gas fraction, albeit with the small HI sample size. On kpc scales, the variations in both SFE and $f_{\rm H_{2}}$ within individual galaxies can be as large as 1-2 dex thereby demonstrating that the availability of spatially-resolved observations is essential to understand the details of both star formation and quenching processes., Comment: 20 pages. ApJS accepted. Complete figure sets of Figures 7 & 8 are available in the online journal

According to the current understanding of cosmic structure formation, the precursors of the most massive structures in the Universe began to form shortly after the Big Bang, in regions corresponding to the largest fluctuations in the cosmic density field. Observing these structures during their period of active growth and assembly - the first few hundred million years of the Universe - is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. As a result, very few such objects have been detected so far. Here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 Myr after the Big Bang) that was discovered in a wide-field survey. High-resolution imaging reveals this source to be a pair of extremely massive star-forming galaxies. The larger of these galaxies is forming stars at a rate of 2900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. Its rapid star formation is probably triggered by its companion galaxy at a projected separation of just 8 kiloparsecs. This merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbor and physical conditions akin to those observed in lower-metallicity galaxies in the nearby Universe. These objects suggest the presence of a dark-matter halo with a mass of more than 400 billion solar masses, making it among the rarest dark-matter haloes that should exist in the Universe at this epoch., Comment: Nature, published online on 06 December 2017

We study the role of cold gas in quenching star formation in the green valley by analysing ALMA $^{12}$CO (1-0) observations of three galaxies with resolved optical spectroscopy from the MaNGA survey. We present resolution-matched maps of the star formation rate and molecular gas mass. These data are used to calculate the star formation efficiency (SFE) and gas fraction ($f_{\rm~gas}$) for these galaxies separately in the central `bulge' regions and outer disks. We find that, for the two galaxies whose global specific star formation rate (sSFR) deviates most from the star formation main sequence, the gas fraction in the bulges is significantly lower than that in their disks, supporting an `inside-out' model of galaxy quenching. For the two galaxies where SFE can be reliably determined in the central regions, the bulges and disks share similar SFEs. This suggests that a decline in $f_{\rm~gas}$ is the main driver of lowered sSFR in bulges compared to disks in green valley galaxies. Within the disks, there exist common correlations between the sSFR and SFE and between sSFR and $f_{\rm~gas}$ on kpc scales -- the local SFE or $f_{\rm~gas}$ in the disks declines with local sSFR. Our results support a picture in which the sSFR in bulges is primarily controlled by $f_{\rm~gas}$, whereas both SFE and $f_{\rm~gas}$ play a role in lowering the sSFR in disks. A larger sample is required to confirm if the trend established in this work is representative of green valley as a whole., Comment: 10 pages, 5 figures, 1 table; ApJ accepted

We report the discovery and constrain the physical conditions of the interstellar medium of the highest-redshift millimeter-selected dusty star-forming galaxy (DSFG) to date, SPT-S J031132-5823.4 (hereafter SPT0311-58), at $z=6.900 +/- 0.002$. SPT0311-58 was discovered via its 1.4mm thermal dust continuum emission in the South Pole Telescope (SPT)-SZ survey. The spectroscopic redshift was determined through an ALMA 3mm frequency scan that detected CO(6-5), CO(7-6) and [CI](2-1), and subsequently confirmed by detections of CO(3-2) with ATCA and [CII] with APEX. We constrain the properties of the ISM in SPT0311-58 with a radiative transfer analysis of the dust continuum photometry and the CO and [CI] line emission. This allows us to determine the gas content without ad hoc assumptions about gas mass scaling factors. SPT0311-58 is extremely massive, with an intrinsic gas mass of $M_{\rm gas} = 3.3 \pm 1.9 \times10^{11}\,M_{\odot}$. Its large mass and intense star formation is very rare for a source well into the Epoch of Reionization., Comment: Accepted by ApJL, Fixed compilation problem in v.2

We report the discovery of a mysterious giant $H_{\alpha}$ blob that is $\sim 8$ kpc away from the main MaNGA target 1-24145, one component of a dry galaxy merger, identified in the first-year SDSS-IV MaNGA data. The size of the $H_{\alpha}$ blob is $\sim$ 3-4 kpc in radius, and the $H_{\alpha}$ distribution is centrally concentrated. However, there is no optical continuum counterpart in deep broadband images reaching $\sim$26.9 mag arcsec$^{-2}$ in surface brightness. We estimate that the masses of ionized and cold gases are $3.3 \times 10^{5}$ $\rm M_{\odot}$ and $< 1.3 \times 10^{9}$ $\rm M_{\odot}$, respectively. The emission-line ratios indicate that the $H_{\alpha}$ blob is photoionized by a combination of massive young stars and AGN. Furthermore, the ionization line ratio decreases from MaNGA 1-24145 to the $H_{\alpha}$ blob, suggesting that the primary ionizing source may come from MaNGA 1-24145, likely a low-activity AGN. Possible explanations of this $H_{\alpha}$ blob include AGN outflow, the gas remnant being tidally or ram-pressure stripped from MaNGA 1-24145, or an extremely low surface brightness (LSB) galaxy. However, the stripping scenario is less favoured according to galaxy merger simulations and the morphology of the $H_{\alpha}$ blob. With the current data, we can not distinguish whether this $H_{\alpha}$ blob is ejected gas due to a past AGN outburst, or a special category of `ultra-diffuse galaxy' (UDG) interacting with MaNGA 1-24145 that further induces the gas inflow to fuel the AGN in MaNGA 1-24145., Comment: 13 pages, 11 figures, ApJ accepted

We present ALMA [CI]($1-0$) (rest frequency 492 GHz) observations for a sample of 13 strongly-lensed dusty star-forming galaxies originally discovered at 1.4mm in a blank-field survey by the South Pole Telescope. We compare these new data with available [CI] observations from the literature, allowing a study of the ISM properties of $\sim 30$ extreme dusty star-forming galaxies spanning a redshift range $2 < z < 5$. Using the [CI] line as a tracer of the molecular ISM, we find a mean molecular gas mass for SPT-DSFGs of $6.6 \times 10^{10}$ M$_{\odot}$. This is in tension with gas masses derived via low-$J$ $^{12}$CO and dust masses; bringing the estimates into accordance requires either (a) an elevated CO-to-H$_2$ conversion factor for our sample of $\alpha_{\rm CO} \sim 2.5$ and a gas-to-dust ratio $\sim200$, or (b) an high carbon abundance $X_{\rm CI} \sim 7\times10^{-5}$. Using observations of a range of additional atomic and molecular lines (including [CI], [CII], and multiple transitions of CO), we use a modern Photodissociation Region code (3D-PDR) to assess the physical conditions (including the density, UV radiation field strength, and gas temperature) within the ISM of the DSFGs in our sample. We find that the ISM within our DSFGs is characterised by dense gas permeated by strong UV fields. We note that previous efforts to characterise PDR regions in DSFGs may have significantly underestimated the density of the ISM. Combined, our analysis suggests that the ISM of extreme dusty starbursts at high redshift consists of dense, carbon-rich gas not directly comparable to the ISM of starbursts in the local Universe., Comment: 21 pages, 12 figures. Accepted for publication in MNRAS

We present Chandra ACIS-S and ATCA radio continuum observations of the strongly lensed dusty, star-forming galaxy SPT-S J034640-5204.9 (hereafter SPT0346-52) at $z$ = 5.656. This galaxy has also been observed with ALMA, HST, Spitzer, Herschel, APEX, and the VLT. Previous observations indicate that if the infrared (IR) emission is driven by star formation, then the inferred lensing-corrected star formation rate ($\sim$ 4500 $M_{\sun}$ yr$^{-1}$) and star formation rate surface density $\Sigma_{\rm SFR}$ ($\sim$ 2000 $M_{\sun} {yr^{-1}} {kpc^{-2}}$) are both exceptionally high. It remained unclear from the previous data, however, whether a central active galactic nucleus (AGN) contributes appreciably to the IR luminosity. The {\it Chandra} upper limit shows that SPT0346-52 is consistent with being star-formation dominated in the X-ray, and any AGN contribution to the IR emission is negligible. The ATCA radio continuum upper limits are also consistent with the FIR-to-radio correlation for star-forming galaxies with no indication of an additional AGN contribution. The observed prodigious intrinsic IR luminosity of (3.6 $\pm$ 0.3) $\times$ 10$^{13}$ $L_{\sun}$ originates almost solely from vigorous star formation activity. With an intrinsic source size of 0.61 $\pm$ 0.03 kpc, SPT0346-52 is confirmed to have one of the highest $\Sigma_{SFR}$ of any known galaxy. This high $\Sigma_{SFR}$, which approaches the Eddington limit for a radiation pressure supported starburst, may be explained by a combination of very high star formation efficiency and gas fraction., Comment: 8 pages, 6 figures, accepted for publication in ApJ

In this work we present an analysis of the behaviour of galaxies in a four-dimensional parameter space defined by stellar mass, metallicity, star formation rate, and molecular gas mass. We analyse a combined sample of 227 galaxies, which draws from a number of surveys across the redshift range 0 < z < 2 (> 90% of the sample at z~0), and covers > 3 decades in stellar mass.Using Principle Component Analysis, we demonstrate that galaxies in our sample lie on a 2-dimensional plane within this 4D parameter space, indicative of galaxies that exist in an equilibrium between gas inflow and outflow. Furthermore, we find that the metallicity of galaxies depends only on stellar mass and molecular gas mass. In other words, gas-phase metallicity has a negligible dependence on star formation rate, once the correlated effect of molecular gas content is accounted for. The well-known `fundamental metallicity relation', which describes a close and tight relationship between metallicity and SFR (at fixed stellar mass) is therefore entirely a by-product of the underlying physical relationship with molecular gas mass (via the Schmidt-Kennicutt relation)., Comment: 5 pages, 2 figures. Accepted for publication in A&A

We present ALMA detections of the [NII] 205$\mu$m and CO(12-11) emission lines, and the tentative detection of [CI] $^3$P$_1$ - $^3$P$_0$ for the strongly lensed ($\mu$=5.7$\pm$0.5) dusty, star-forming galaxy SPT-S J213242-5802.9 (hereafter SPT2132-58) at z=4.77. The [NII] and CO(12-11) lines are detected at 11.5 and 8.5 $\sigma$ level, respectively, by our band-6 observations. The [CI] line is detected at 3.2 $\sigma$ after a re-analysis of existing band-3 data. The [CI] luminosity implies a gas mass of 3.8$\pm$1.2$\times$10$^{10}$ M$_\odot$, and consequently a very short depletion timescale of 34$\pm$13 Myr and a CO-luminosity-to-gas-mass conversion factor $\alpha_{\rm CO}$ of 1.0$\pm$0.3 M$_\odot$ (K km s$^{-1}$ pc$^{2}$)$^{-1}$. SPT2132-58 is an extreme starburst with an intrinsic star formation rate of 1100$\pm$200 M$_\odot$/yr. We find a [CII]/[NII] ratio of 26$\pm$7, which is the highest reported at z$>$4. This suggests that SPT2132-58 hosts an evolved interstellar medium (0.5 Z$_\odot$

To understand cosmic mass assembly in the Universe at early epochs, we primarily rely on measurements of stellar mass and star formation rate of distant galaxies. In this paper, we present stellar masses and star formation rates of six high-redshift ($2.8\leq z \leq 5.7$) dusty, star-forming galaxies (DSFGs) that are strongly gravitationally lensed by foreground galaxies. These sources were first discovered by the South Pole Telescope (SPT) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from ALMA observations. We have conducted follow-up observations, obtaining multi-wavelength imaging data, using {\it HST}, {\it Spitzer}, {\it Herschel} and the Atacama Pathfinder EXperiment (APEX). We use the high-resolution {\it HST}/WFC3 images to disentangle the background source from the foreground lens in {\it Spitzer}/IRAC data. The detections and upper limits provide important constraints on the spectral energy distributions (SEDs) for these DSFGs, yielding stellar masses, IR luminosities, and star formation rates (SFRs). The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value $\sim$ 5 $\times 10^{10}M_{\Sun}$. The intrinsic IR luminosities range from 4$\times 10^{12}L_{\Sun}$ to 4$\times 10^{13}L_{\Sun}$. They all have prodigious intrinsic star formation rates of 510 to 4800 $M_{\Sun} {\rm yr}^{-1}$. Compared to the star-forming main sequence (MS), these six DSFGs have specific SFRs that all lie above the MS, including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing the ongoing strong starburst events which may be driven by major mergers., Comment: 18 pages, 13 figures, to be published in ApJ

We present spatially-resolved imaging obtained with the Australia Telescope Compact Array (ATCA) of three CO lines in two high-redshift gravitationally lensed dusty star-forming galaxies, discovered by the South Pole Telescope. Strong lensing allows us to probe the structure and dynamics of the molecular gas in these two objects, at z=2.78 and z=5.66, with effective source-plane resolution of less than 1kpc. We model the lensed emission from multiple CO transitions and the dust continuum in a consistent manner, finding that the cold molecular gas as traced by low-J CO always has a larger half-light radius than the 870um dust continuum emission. This size difference leads to up to 50% differences in the magnification factor for the cold gas compared to dust. In the z=2.78 galaxy, these CO observations confirm that the background source is undergoing a major merger, while the velocity field of the other source is more complex. We use the ATCA CO observations and comparable resolution Atacama Large Millimeter/submillimeter Array dust continuum imaging of the same objects to constrain the CO-H_2 conversion factor with three different procedures, finding good agreement between the methods and values consistent with those found for rapidly star-forming systems. We discuss these galaxies in the context of the star formation - gas mass surface density relation, noting that the change in emitting area with observed CO transition must be accounted for when comparing high-redshift galaxies to their lower redshift counterparts., Comment: 14 pages, 7 figures; accepted for publication in ApJ

There has been much recent work dedicated to exploring secondary correlations in the mass-metallicity relation, with significant dependence on both the star formation rate and HI content being demonstrated. Previously, a paucity of molecular gas data (combined with sample selection bias) hampered the investigation of any such relation with molecular gas content. In this work, we assemble a sample of 221 galaxies from a variety of surveys in the redshift range 0 < z < 2, to explore the connection between molecular gas content and metallicity. We explore the effect of gas mass on the mass-metallicity relation, finding that the offset from the relation is negatively correlated against both molecular and total gas mass. We then employ a principle component analysis technique to explore secondary dependences in the mass-metallicity relation, finding that the secondary dependence with gas mass is significantly stronger than with star formation rate, and as such the underlying `Fundamental Metallicity Relation' is between stellar mass, metallicity, and gas mass. In particular, the metallicity dependence on SFR is simply a byproduct of the dependence on the molecular gas content, via the Schmidt-Kennicutt relation. Finally, we note that our principle component analysis finds essentially no connection between gas-phase metallicity and the efficiency of star formation., Comment: 20 pages, 10 figures. Replacement version accepted for publication in MNRAS

We have analysed 18 ALMA continuum maps in Bands 6 and 7, with rms down to 7.8$\mu$Jy, to derive differential number counts down to 60$\mu$Jy and 100$\mu$Jy at $\lambda=$1.3 mm and $\lambda=$1.1 mm, respectively. The area covered by the combined fields is $\rm 9.5\times10^{-4}deg^2$ at 1.1mm and $\rm 6.6\times10^{-4}deg^{2}$ at 1.3mm. We improved the source extraction method by requiring that the dimension of the detected sources be consistent with the beam size. This method enabled us to remove spurious detections that have plagued the purity of the catalogues in previous studies. We detected 50 faint sources with S/N$>$3.5 down to 60$\mu$Jy, hence improving the statistics by a factor of four relative to previous studies. The inferred differential number counts are $\rm dN/d(Log_{10}S)=1\times10^5~deg^2$ at a 1.1 mm flux $S_{\lambda = 1.1~mm} = 130~\mu$Jy, and $\rm dN/d(Log_{10}S)=1.1\times10^5~deg^2$ at a 1.3 mm flux $\rm S_{\lambda = 1.3~mm} = 60~\mu$Jy. At the faintest flux limits, i.e. 30$\mu$Jy and 40$\mu$Jy, we obtain upper limits on the differential number counts of $\rm dN/d(Log_{10}S) < 7\times10^5~deg^2$ and $\rm dN/d(Log_{10}S)<3\times10^5~deg^2$, respectively. Our results provide a new lower limit to CIB intensity of 17.2${\rm Jy\ deg^{-2}}$ at 1.1mm and of 12.9${\rm Jy\ deg^{-2}}$ at 1.3mm. Moreover, the flattening of the integrated number counts at faint fluxes strongly suggests that we are probably close to the CIB intensity. Our data imply that galaxies with SFR$<40~M_{\odot}/yr$ certainly contribute less than 50% to the CIB while more than 50% of the CIB must be produced by galaxies with $\rm SFR>40~M_{\odot}/yr$. The differential number counts are in nice agreement with recent semi-analytical models of galaxy formation even as low as our faint fluxes. Consequently, this supports the galaxy evolutionary scenarios and assumptions made in these models., Comment: 11 pages, 9 figures, A&A accepted

We present ALLSMOG, the APEX Low-redshift Legacy Survey for MOlecular Gas. ALLSMOG is a survey designed to observe the CO(2-1) emission line with the APEX telescope, in a sample of local galaxies (0.01 < z < 0.03), with stellar masses in the range 8.5 < log(M*/Msun) < 10. This paper is a data release and initial analysis of the first two semesters of observations, consisting of 42 galaxies observed in CO(2-1). By combining these new CO(2-1) emission line data with archival HI data and SDSS optical spectroscopy, we compile a sample of low-mass galaxies with well defined molecular gas masses, atomic gas masses, and gas-phase metallicities. We explore scaling relations of gas fraction and gas consumption timescale, and test the extent to which our findings are dependent on a varying CO/H2 conversion factor. We find an increase in the H2/HI mass ratio with stellar mass which closely matches semi-analytic predictions. We find a mean molecular gas fraction for ALLSMOG galaxies of MH2/M* = (0.09 - 0.13), which decreases with stellar mass. We measure a mean molecular gas consumption timescale for ALLSMOG galaxies of 0.4 - 0.7 Gyr. We also confirm the non-universality of the molecular gas consumption timescale, which varies (with stellar mass) from ~100 Myr to ~2 Gyr. Importantly, we find that the trends in the H2/HI mass ratio, gas fraction, and the non-universal molecular gas consumption timescale are all robust to a range of recent metallicity-dependent CO/H2 conversion factors., Comment: 25 pages, 15 figures. Accepted for publication in MNRAS

We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250-770GHz. This spectrum was constructed by stacking ALMA 3mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z=2.0-5.7. In addition to multiple bright spectral features of 12CO, [CI], and H2O, we also detect several faint transitions of 13CO, HCN, HNC, HCO+, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the 13CO brightness in these objects is comparable to that of the only other z>2 star-forming galaxy in which 13CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense medium with T_kin ~ 55K and n_H2 >~ 10^5.5 cm^-3. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4-1.2mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations., Comment: 19 pages, 10 figures (2 in appendices); accepted for publication in ApJ

We present observations of SPT-S J053816-5030.8, a gravitationally-lensed dusty star forming galaxy (DSFG) at z = 2.7817, first discovered at millimeter wavelengths by the South Pole Telescope. SPT 0538-50 is typical of the brightest sources found by wide-field millimeter-wavelength surveys, being lensed by an intervening galaxy at moderate redshift (in this instance, at z = 0.441). We present a wide array of multi-wavelength spectroscopic and photometric data on SPT 0538-50, including data from ALMA, Herschel PACS and SPIRE, Hubble, Spitzer, VLT, ATCA, APEX, and the SMA. We use high resolution imaging from HST to de-blend SPT 0538-50, separating DSFG emission from that of the foreground lens. Combined with a source model derived from ALMA imaging (which suggests a magnification factor of 21 +/- 4), we derive the intrinsic properties of SPT 0538-50, including the stellar mass, far-IR luminosity, star formation rate, molecular gas mass, and - using molecular line fluxes - the excitation conditions within the ISM. The derived physical properties argue that we are witnessing compact, merger-driven star formation in SPT 0538-50, similar to local starburst galaxies, and unlike that seen in some other DSFGs at this epoch., Comment: 16 pages, 11 figures. Accepted for publication in ApJ

Recent results have suggested that the well known mass-metallicity relation has a strong dependence on the star formation rate, to the extent that a three dimensional `fundamental metallicity relation' exists which links the three parameters with minimal scatter. In this work, we use a sample of 4253 local galaxies observed in atomic hydrogen from the ALFALFA survey to demonstrate, for the first time, that a similar fundamental relation (the HI-FMR) also exists between stellar mass, gas-phase metallicity, and HI mass. This latter relation is likely more fundamental, driving the relation between metallicity, SFR and mass. At intermediate masses, the behaviour of the gas fundamental metallicity relation is very similar to that expressed via the star formation rate. However, we find that the dependence of metallicity on HI content persists to the highest stellar masses, in contrast to the `saturation' of metallicity with SFR. It is interesting to note that the dispersion of the relation is very low at intermediate stellar masses (9< log(M*/Msun) <11), suggesting that in this range galaxies evolve smoothy, in an equilibrium between gas inflow, outflow and star formation. At high and low stellar masses, the scatter of the relation is significantly higher, suggesting that merging events and/or stochastic accretion and star formation may drive galaxies outside the relation. We also assemble a sample of galaxies observed in CO. However, due to a small sample size, strong selection bias, and the influence of a metallicity-dependent CO/H2 conversion factor, the data are insufficient to test any influence of molecular gas on metallicity., Comment: 12 pages, 8 figures. Accepted for publication in MNRAS

We present the results from a survey for 12CO emission in 40 luminous sub-millimetre galaxies (SMGs), with 850um fluxes of S850 = 4 - 20 mJy, conducted with the Plateau de Bure Interferometer. We detect 12CO emission in 32 SMGs at z~1.2 - 4.1, including 16 SMGs not previously published. Using multiple 12CO line (J_up =2 - 7) observations, we derive a median spectral line energy distribution for luminous SMGs and use this to estimate a mean gas mass of (5.3 +/- 1.0) \times 10^10 Msun. We report the discovery of a fundamental relationship between 12CO FWHM and 12CO line luminosity in high-redshift starbursts, which we interpret as a natural consequence of the baryon-dominated dynamics within the regions probed by our observations. We use far-infrared luminosities to assess the star-formation efficiency in our SMGs, finding a steepening of the L'CO-LFIR relation as a function of increasing 12CO J_up transition. We derive dynamical masses and molecular gas masses, and use these to determine the redshift evolution of the gas content of SMGs, finding that they do not appear to be significantly more gas rich than less vigorously star-forming galaxies at high redshifts. Finally, we collate X-ray observations, and study the interdependence of gas and dynamical properties of SMGs with their AGN activity and supermassive black hole masses (MBH), finding that SMGs lie significantly below the local M_BH-sigma relation. We conclude that SMGs represent a class of massive, gas-rich ultraluminous galaxies with somewhat heterogeneous properties, ranging from starbursting disc-like systems with L~10^12 L_sun, to the most highly star-forming mergers in the Universe., Comment: 47 Pages, 50 figures. Submitted to MNRAS

We present total infrared (IR) and ultraviolet (UV) luminosity functions derived from large representative samples of galaxies at z ~ 0, selected at IR and UV wavelengths from the IRAS IIFSCz catalogue, and the GALEX AIS respectively. We augment these with deep Spitzer and GALEX imaging of galaxies in the 11 Mpc Local Volume Legacy Survey (LVL), allowing us to extend these luminosity functions to lower luminosities (~10^6 L_sun), and providing good constraints on the slope of the luminosity function at the extreme faint end for the first time. Using conventional star formation prescriptions, we generate from our data the SFR distribution function for the local Universe. We find that it has a Schechter form, that the faint-end slope has a constant value (to the limits of our data) of {\alpha} = -1.51 \pm 0.08, and the 'characteristic' SFR is 9.2 M_sun/yr. We also show the distribution function of the SFR volume density; we then use this to calculate a value for the total SFR volume density at z ~ 0 of 0.025 \pm 0.0016 M_sun/yr/Mpc^-3, of which ~ 20% is occurring in starbursts. Decomposing the total star formation by infrared luminosity, it can be seen that 9 \pm 1% is due to LIRGs, and 0.7 \pm 0.2% is occuring in ULIRGs. By comparing UV and IR emission for galaxies in our sample, we also calculate the fraction of star formation occurring in dust obscured environments, and examine the distribution of dusty star formation: we find a very shallow slope at the highly extincted end, which may be attributable to line of sight orientation effects as well as conventional internal extinction., Comment: 14 pages, 10 figures; accepted for publication in MNRAS

We present near-infrared spectroscopic observations from VLT ISAAC of thirteen 250\mu m-luminous galaxies in the CDF-S, seven of which have confirmed redshifts which average to = 2.0 \pm 0.4. Another two sources of the 13 have tentative z > 1 identifications. Eight of the nine redshifts were identified with H{\alpha} detection in H- and K-bands, three of which are confirmed redshifts from previous spectroscopic surveys. We use their near-IR spectra to measure H{\alpha} line widths and luminosities, which average to 415 \pm 20 km/s and 3 \times 10^35 W (implying SFR(H{\alpha})~200 M_\odot /yr), both similar to the H{\alpha} properties of SMGs. Just like SMGs, 250 \mu m-luminous galaxies have large H{\alpha} to far-infrared (FIR) extinction factors such that the H{\alpha} SFRs underestimate the FIR SFRs by ~8-80 times. Far-infrared photometric points from observed 24\mu m through 870\mu m are used to constrain the spectral energy distributions (SEDs) even though uncertainty caused by FIR confusion in the BLAST bands is significant. The population has a mean dust temperature of Td = 52 \pm 6 K, emissivity {\beta} = 1.73 \pm 0.13, and FIR luminosity LFIR = 3 \times 10^13 L_\odot. Although selection at 250\mu m allows for the detection of much hotter dust dominated HyLIRGs than SMG selection (at 850\mu m), we do not find any >60 K 'hot-dust' HyLIRGs. We have shown that near-infrared spectroscopy combined with good photometric redshifts is an efficient way to spectroscopically identify and characterise these rare, extreme systems, hundreds of which are being discovered by the newest generation of IR observatories including the Herschel Space Observatory., Comment: 12 pages, 6 figures; Revised with minor corrections from the referee, MNRAS

We present high spatial resolution (0.4", ~3.5 kpc) PdBI interferometric data on three ultra-luminous infrared galaxies (ULIRGs) at z~2: two submillimetre galaxies and one submillimetre faint star forming radio galaxy. The three galaxies have been ro- bustly detected in CO rotational transitions, either 12CO(J=4-3) or 12CO(J=3-2), allowing their sizes and gas masses to be accurately constrained. These are the highest spatial resolution observations observed to date (by a factor of ~2) for intermediate-excitation CO emission in z~2 ULIRGs. The galaxies appear extended over several resolution elements, having a mean radius of 3.7 kpc. High-resolution (0.3") combined MERLIN-VLA observations of their radio continua allow an analysis of the star formation behaviour of these galaxies, on comparable spatial scales to that of the CO observations. This 'matched beam' approach sheds light on the spatial distribution of both molecular gas and star formation, and we can therefore calculate accurate star formation rates and gas surface densities: this allows us to place the three systems in the context of a Kennicutt-Schmidt (KS)-style star formation law. We find a difference in size between the CO and radio emission regions, and as such we suggest that using the spatial extent of the CO emission region to estimate the surface density of star formation may lead to error. This size difference also causes the star formation efficiencies within systems to vary by up to a factor of 5. We also find, with our new accurate sizes, that SMGs lie significantly above the KS relation, indicating that stars are formed more efficiently in these extreme systems than in other high-z star forming galaxies., Comment: 17 pages, 10 figures; revised version accepted for publication in MNRAS

[abridged] We present interferometric CO observations of twelve z~2 submillimetre-faint, star-forming radio galaxies (SFRGs) which are thought to be ultraluminous infrared galaxies (ULIRGs) possibly dominated by warmer dust (T_dust ~> 40 K) than submillimetre galaxies (SMGs) of similar luminosities. Four other CO-observed SFRGs are included from the literature, and all observations are taken at the Plateau de Bure Interferometer (PdBI) in the compact configuration. Ten of the sixteen SFRGs observed in CO (63%) are detected at >4sigma with a mean inferred molecular gas mass of ~2*10^10 M_sun. SFRGs trend slightly above the local ULIRG L_FIR-L'_CO relation. Since SFRGs are about two times fainter in radio luminosity but exhibit similar CO luminosities to SMGs, this suggests SFRGs are slightly more efficient star formers than SMGs at the same redshifts. SFRGs also have a narrow mean CO line width, 320+-80km/s. SFRGs bridge the gap between properties of very luminous >5*10^12 L_sun SMGs and those of local ULIRGs and are consistent with intermediate stage major mergers. We suspect that more moderate-luminosity SMGs, not yet surveyed in CO, would show similar molecular gas properties to SFRGs. The AGN fraction of SFRGs is consistent with SMGs and is estimated to be 0.3+-0.1, suggesting that SFRGs are observed near the peak phase of star formation activity and not in a later, post-SMG enhanced AGN phase. This CO survey of SFRGs serves as a pilot project for the much more extensive survey of Herschel and SCUBA-2 selected sources which only partially overlap with SMGs. Better constraints on CO properties of a diverse high-z ULIRG population are needed from ALMA to determine the evolutionary origin of extreme starbursts, and what role ULIRGs serve in catalyzing the formation of massive stellar systems in the early Universe., Comment: 23 pages, 9 figures; MNRAS accepted

We present a demographic analysis of integrated star formation and gas properties for a sample of galaxies representative of the overall population at z~0. This research was undertaken in order to characterise the nature of star formation and interstellar medium behaviour in the local universe, and test the extent to which global star formation rates can be seen as dependent on the interstellar gas content. Archival 21 cm derived HI data are compiled from the literature, and are combined with CO (J=1-0) derived H_2 masses to calculate and characterise the total gas content for a large sample of local galaxies. The distribution in stellar mass-normalised HI content is found to exhibit the noted characteristic transition at stellar masses of ~3x10^10 M_sun, turning off towards low values, but no such transition is observed in the equivalent distribution of molecular gas. H-alpha based star formation rates and specific star formation rates are also compiled for a large (1110) sample of local galaxies. We confirm two transitions as found in previous work: a turnover towards low SFRs at high luminosities, indicative of the quenching of SF characteristic of the red sequence; and a broadening of the SF distribution in low-luminosity dwarf galaxies, again to extremely low SFRs of < 0.001 M_sun/yr. However, a new finding is that while the upper luminosity transition is mirrored by the turn over in HI content, suggesting that the low SFRs of the red sequence result from a lack of available gas supply, the transition towards a large spread of SFRs in the least luminous dwarf galaxies is not matched by a prominent increase in scatter in gas content. Possible mass-dependent quenching mechanisms are discussed, along with speculations that in low mass galaxies, the H-alpha luminosity may not faithfully trace the SFR., Comment: 15 pages, 12 figures; accepted for publication in MNRAS

Context. In quiescence, the proposed optical counterpart to the neutron star low mass X-ray binary 4U 2129+47 (V1727 Cyg) shows a spectrum consistent with a late F-type subgiant and no radial velocity variations on the 5.24 hour binary period. This could imply that V1727 Cyg is a chance line of sight interloper. Radial velocity measurements, however, showed evidence for a longer term ~40 km/s shift, which suggested that 4U 2129+47 could be a hierarchical triple system, with the F-type star in a wide orbit about the inner low mass X-ray binary. Aims. In order to confirm the long-term radial velocity shift reported in Garcia et al. (1989) and its amplitude, we obtained spectroscopic observations of V1727 Cyg during 1996 and 1998 with the William Herschel Telescope using the ISIS spectrograph. Methods. We determined radial velocities from the ISIS spectra by means of the cross-correlation technique with a template spectrum. Results. The resulting radial velocities show variations with a maximum amplitude of ~40 km/s, confirming previous results and supporting the F-type star as being the third body in a hierarchical triple system. The odds that this star could be an interloper are ~3e-6, Comment: 3 Pages, 2 Figures. Revised version in form accepted for publication in A&A