28 research outputs found

    Local analogues of high-redshift star-forming galaxies: integral field spectroscopy of green peas

    Get PDF
    This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We use integral field spectroscopy, from the SWIFT and Palm3K instruments, to perform a spatially-resolved spectroscopic analysis of four nearby highly star-forming `green pea' (GP) galaxies, that are likely analogues of star-forming systems at z~2.5-3. By studying emission-line maps in Hα\alpha, [NII]λλ\lambda \lambda6548,6584 and [SII]λ\lambdaλ\lambda6716,6731, we explore the kinematic morphology of these systems and constrain properties such as gas-phase metallicities, electron densities and gas-ionization mechanisms. Two of our GPs are rotationally-supported while the others are dispersion-dominated systems. The rotationally-supported galaxies both show evidence for recent or ongoing mergers. However, given that these systems have intact disks, these interactions are likely to have low mass ratios (i.e. minor mergers), suggesting that the minor-merger process may be partly responsible for the high SFRs seen in these GPs. Nevertheless, the fact that the other two GPs appear morphologically undisturbed suggests that mergers (including minor mergers) are not necessary for driving the high star formation rates in such galaxies. We show that the GPs are metal-poor systems (25-40 per cent of solar) and that the gas ionization is not driven by AGN in any of our systems, indicating that AGN activity is not co-eval with star formation in these starbursting galaxies.Peer reviewedFinal Published versio

    Glutamate cycling may drive organic anion transport on the basal membrane of human placental syncytiotrophoblast

    No full text
    The organic anion transporter OAT4 (SLC22A11) and organic anion transporting polypeptide OATP2B1 (SLCO2B1) are expressed in the basal membrane of the placental syncytiotrophoblast. These transporters mediate exchange whereby uptake of one organic anion is coupled to efflux of a counter-ion. In placenta, these exchangers mediate placental uptake of substrates for oestrogen synthesis as well as clearing waste products and xenobiotics from the fetal circulation. However, the identity of the counter-ion driving this transport in the placenta, and in other tissues, is unclear. While glutamate is not a known OAT4 or OATP2B1 substrate, we propose that its high intracellular concentration has the potential to drive accumulation of substrates from the fetal circulation. In the isolated perfused placenta, glutamate exchange was observed between the placenta and the fetal circulation. This exchange could not be explained by known glutamate exchangers. However, glutamate efflux was trans-stimulated by an OAT4 and OATP2B1 substrate (bromosulphothalein). Exchange of glutamate for bromosulphothalein was only observed when glutamate reuptake was inhibited (by addition of aspartate). To determine if OAT4 and/or OATP2B1 mediate glutamate exchange, uptake and efflux of glutamate were investigated in Xenopus laevis oocytes. Our data demonstrate that in Xenopus oocytes expressing either OAT4 or OATP2B1 efflux of intracellular [14C]glutamate could be stimulated by conditions including extracellular glutamate (OAT4), estrone-sulphate and bromosulphothalein (both OAT4 and OATP2B1) or pravastatin (OATP2B1). Cycling of glutamate across the placenta involving efflux via OAT4 and OATP2B1 and subsequent reuptake will drive placental uptake of organic anions from the fetal circulation.<br/

    MUSE Analysis of Gas around Galaxies (MAGG) -- V: Linking ionized gas traced by CIV and SiIV absorbers to Lyα{\alpha} emitting galaxies at z3.04.5z\approx 3.0-4.5

    Full text link
    We use 28 quasar fields with high-resolution (HIRES and UVES) spectroscopy from the MUSE Analysis of Gas Around Galaxies survey to study the connection between Lyα{\alpha} emitters (LAEs) and metal-enriched ionized gas traced by CIV in absorption at redshift z34z\approx3-4. In a sample of 220 CIV absorbers, we identify 143 LAEs connected to CIV gas within a line-of-sight separation ±500kms1{\rm \pm 500\,km\,s^{-1}}, equal to a detection rate of 36±536\pm 5 per cent once we account for multiple LAEs connected to the same CIV absorber. The luminosity function of LAEs associated with CIV absorbers shows a 2.4\approx 2.4 higher normalization factor compared to the field. CIV with higher equivalent width and velocity width are associated with brighter LAEs or multiple galaxies, while weaker systems are less often identified near LAEs. The covering fraction in groups is up to 3\approx 3 times larger than for isolated galaxies. Compared to the correlation between optically-thick HI absorbers and LAEs, CIV systems are twice less likely to be found near LAEs especially at lower equivalent width. Similar results are found using SiIV as tracer of ionized gas. We propose three components to model the gas environment of LAEs: i) the circumgalactic medium of galaxies, accounting for the strongest correlations between absorption and emission; ii) overdense gas filaments connecting galaxies, driving the excess of LAEs at a few times the virial radius and the modulation of the luminosity and cross-correlation functions for strong absorbers; iii) an enriched and more diffuse medium, accounting for weaker CIV absorbers farther from galaxies.Comment: 28 pages, 21 figures, 10 tables. Submitted to MNRAS after accounting for reviewer's comment

    Ursodeoxycholic acid inhibits uptake and vasoconstrictor effects of taurocholate in human placenta

    Get PDF
    Intrahepatic cholestasis of pregnancy (ICP) causes increased transfer of maternal bile acids to the fetus and an increased incidence of sudden fetal death. Treatment includes ursodeoxycholic acid (UDCA), but it is not clear if UDCA protects the fetus. This study explores the placental transport of the bile acid taurocholate (TC) by the organic anion–transporting polypeptide, (OATP)4A1, its effects on the placental proteome and vascular function, and how these are modified by UDCA. Various methodological approaches including placental villous fragments and Xenopus laevis oocytes were used to investigate UDCA transport. Placental perfusions and myography investigated the effect of TC on vasculature. The effects of acute TC exposure on placental tissue were investigated using quantitative proteomics. UDCA inhibited OATP4A1 activity in placental villous fragments and oocytes. TC induced vasoconstriction in placental and rat vasculature, which was attenuated by UDCA. Quantitative proteomic analysis of villous fragments showed direct effects of TC on multiple placental pathways, including oxidative stress and autophagy. The effects of TC on the placental proteome and vasculature demonstrate how bile acids may cause fetal distress in ICP. UDCA inhibition of OATP4A1 suggests it will protect the mother and fetus against the vascular effects of TC by inhibiting its cellular uptake. UDCA may protect the fetus in ICP by inhibiting OATP4A1-mediated bile acid transfer and TC-induced placental vasoconstriction. Understanding the physiologic mechanisms of UDCA may allow better therapeutic interventions to be designed specifically for the fetus in the future.—Lofthouse, E. M., Torrens, C., Manousopoulou, A., Nahar, M., Cleal, J. K., O’Kelly, I. M., Sengers, B. G., Garbis, S. D., Lewis, R. M. Ursodeoxycholic acid inhibits uptake and vasoconstrictor effects of taurocholate in human placenta

    The MUSE Ultra Deep Field (MUDF). IV. A pair of X-ray weak quasars at the heart of two extended Ly{\alpha} nebulae

    Full text link
    We present the results obtained from follow-up observations of the MUSE Ultra Deep Field (MUDF) at X-ray energies with XMM-Newton. The MUDF is centred on a unique field with two bright, physically associated quasars at z3.23z\simeq3.23, separated by \sim500 kpc in projection. Both quasars are embedded within extended Lyα\alpha nebulae (100 kpc\gtrsim 100~\rm kpc at a surface brightness flux level of 6×1019erg s1 cm2 arcsec2\approx 6\times 10^{-19} \rm erg~s^{-1}~cm^{-2}~arcsec^{-2}), whose elongated morphology is suggestive of an extended filament connecting the quasar haloes. The new X-ray observations presented here allow us to characterise the physical properties (e.g. X-ray slope, luminosities, gas column densities) in the innermost region of the MUDF quasars. We find that both quasars are X-ray underluminous compared to objects at similar ultraviolet luminosities. Based on our X-ray spectral analysis, absorbing columns of NH(z)N_H(z)\gtrsim 1023^{23} cm2^{-2} appear unlikely, therefore such a weakness is possibly intrinsic. When also including literature data, we do not observe any detectable trend between the area of the nebulae and nuclear luminosities at both the rest-frame 2 keV and 2500 A˚\rm \mathring{A}. The area is also not correlated with the X-ray photon index nor with the integrated band flux in the hard band (2-10 keV). We also do not find any trend between the extended Lyα\alpha emission of the nebulae and the nuclear X-ray luminosity. Finally, the properties of the MUDF quasars' nebulae are consistent with the observed relation between the Lyα\alpha integrated luminosity of the nebulae and their area. Our results suggest that the quasar ionization power is not a strong driver of the morphology and size of the nebulae.Comment: 15 pages, 9 figures, reference added, published in MNRA

    MUSE Analysis of Gas around Galaxies (MAGG) - I: Survey design and the environment of a near pristine gas cloud at z ≈ 3.5

    Get PDF
    We present the design, methods, and first results of the MUSE Analysis of Gas around Galaxies (MAGG) survey, a large programme on the Multi Unit Spectroscopic Explorer (MUSE) instrument at the Very Large Telescope (VLT) which targets 28 z > 3.2 quasars to investigate the connection between optically-thick gas and galaxies at z ∼ 3 − 4. MAGG maps the environment of 52 strong absorption line systems at z ≳ 3, providing the first statistical sample of galaxies associated with gas-rich structures in the early Universe. In this paper, we study the galaxy population around a very metal poor gas cloud at z ≈ 3.53 towards the quasar J124957.23−015928.8. We detect three Lyα emitters within ≲200 km s−1 of the cloud redshift, at projected separations ≲185 kpc (physical). The presence of star-forming galaxies near a very metal-poor cloud indicates that metal enrichment is still spatially inhomogeneous at this redshift. Based on its very low metallicity and the presence of nearby galaxies, we propose that the most likely scenario for this LLS is that it lies within a filament which may be accreting onto a nearby galaxy. Taken together with the small number of other LLSs studied with MUSE, the observations to date show a range of different environments near strong absorption systems. The full MAGG survey will significantly expand this sample and enable a statistical analysis of the link between gas and galaxies to pin down the origin of these diverse environments at z ≈ 3 − 4

    Metal line emission from galaxy haloes at z~1

    Get PDF
    We present a study of the metal-enriched halo gas, traced using MgII and [OII] emission lines, in two large, blind galaxy surveys - the MUSE (Multi Unit Spectroscopic Explorer) Analysis of Gas around Galaxies (MAGG) and the MUSE Ultra Deep Field (MUDF). By stacking a sample of ~600 galaxies (stellar masses M* ~10^{6-12} Msun), we characterize for the first time the average metal line emission from a general population of galaxy haloes at 0.7 <= z <= 1.5. The MgII and [OII] line emission extends farther out than the stellar continuum emission, on average out to ~25 kpc and ~45 kpc, respectively, at a surface brightness (SB) level of 10^{-20} erg/s/cm2/arcsec2. The radial profile of the MgII SB is shallower than that of the [OII], suggesting that the resonant MgII emission is affected by dust and radiative transfer effects. The [OII] to MgII SB ratio is ~3 over ~20-40 kpc, also indicating a significant in situ origin of the extended metal emission. The average SB profiles are intrinsically brighter by a factor ~2-3 and more radially extended by a factor of ~1.3 at 1.0 < z <= 1.5 than at 0.7 <= z <= 1.0. The average extent of the metal emission also increases independently with increasing stellar mass and in overdense group environments. When considering individual detections, we find extended [OII] emission up to ~50 kpc around ~30-40 percent of the group galaxies, and extended (~30-40 kpc) MgII emission around two z~1 quasars in groups, which could arise from outflows or environmental processes.Comment: 24 pages, 21 figures, 2 tables, accepted for publication in MNRA

    Ursodeoxycholic acid inhibits uptake and vasoconstrictor effects of taurocholate in human placenta

    Get PDF
    Intrahepatic cholestasis of pregnancy (ICP) causes increased transfer of maternal bile acids to the fetus and an increased incidence of sudden fetal death. Treatment includes ursodeoxycholic acid (UDCA), but it is not clear if UDCA protects the fetus. This study explores the placental transport of the bile acid taurocholate (TC) by the organic anion–transporting polypeptide, (OATP)4A1, its effects on the placental proteome and vascular function, and how these are modified by UDCA. Various methodological approaches including placental villous fragments and Xenopus laevis oocytes were used to investigate UDCA transport. Placental perfusions and myography investigated the effect of TC on vasculature. The effects of acute TC exposure on placental tissue were investigated using quantitative proteomics. UDCA inhibited OATP4A1 activity in placental villous fragments and oocytes. TC induced vasoconstriction in placental and rat vasculature, which was attenuated by UDCA. Quantitative proteomic analysis of villous fragments showed direct effects of TC on multiple placental pathways, including oxidative stress and autophagy. The effects of TC on the placental proteome and vasculature demonstrate how bile acids may cause fetal distress in ICP. UDCA inhibition of OATP4A1 suggests it will protect the mother and fetus against the vascular effects of TC by inhibiting its cellular uptake. UDCA may protect the fetus in ICP by inhibiting OATP4A1-mediated bile acid transfer and TC-induced placental vasoconstriction. Understanding the physiologic mechanisms of UDCA may allow better therapeutic interventions to be designed specifically for the fetus in the future.—Lofthouse, E. M., Torrens, C., Manousopoulou, A., Nahar, M., Cleal, J. K., O’Kelly, I. M., Sengers, B. G., Garbis, S. D., Lewis, R. M. Ursodeoxycholic acid inhibits uptake and vasoconstrictor effects of taurocholate in human placenta

    Metal-enriched halo gas across galaxy overdensities over the last 10 billion years

    Get PDF
    We present a study of metal-enriched halo gas traced by Mg II and C IV absorption at z 1. It is clear from our results that environmental processes have a significant impact on the distribution of metals around galaxies and need to be fully accounted for when analysing correlations between gaseous haloes and galaxy properties
    corecore