ABSTRACT
We present $850\, \mu {\rm m}$ imaging of the XMM-LSS field observed for 170 h as part of the James Clerk Maxwell Telescope SCUBA-2 Large eXtragalactic Survey (S2LXS). S2LXS XMM-LSS maps an ...area of $9\, {\rm deg}^2$, reaching a moderate depth of $1\sigma \simeq 4\, {\rm mJy\, beam^{-1}}$. This is the largest contiguous area of extragalactic sky mapped by James Clerk Maxwell Telescope (JCMT) at $850\, \mu {\rm m}$ to date. The wide area of the S2LXS XMM-LSS survey allows us to probe the ultra-bright ($S_{\rm 850\mu m}\gtrsim 15\, {\rm mJy}$), yet rare submillimetre population. We present the S2LXS XMM-LSS catalogue, which comprises 40 sources detected at >5σ significance, with deboosted flux densities in the range of $7$–$48\, {\rm mJy}$. We robustly measure the bright-end of the $850\, \mu {\rm m}$ number counts at flux densities ${\gt }7\, {\rm mJy}$, reducing the Poisson errors compared to existing measurements. The S2LXS XMM-LSS observed number counts show the characteristic upturn at bright fluxes, expected to be motivated by local sources of submillimetre emission and high-redshift strongly lensed galaxies. We find that the observed $850\, \mu {\rm m}$ number counts are best reproduced by model predictions that include either strong lensing or source blending from a 15-arcsec beam, indicating that both may make an important contribution to the observed overabundance of bright single dish $850\, \mu {\rm m}$ selected sources. We make the S2LXS XMM-LSS $850\, \mu {\rm m}$ map and >5σ catalogue presented here publicly available.
Abstract
We present a new measurement of the evolving galaxy far-IR luminosity function (LF) extending out to redshifts z ≃ 5, with resulting implications for the level of dust-obscured star ...formation density in the young Universe. To achieve this, we have exploited recent advances in sub-mm/mm imaging with SCUBA-2 on the James Clerk Maxwell Telescope and the Atacama Large Millimeter/Submillimeter Array, which together provide unconfused imaging with sufficient dynamic range to provide meaningful coverage of the luminosity-redshift plane out to z > 4. Our results support previous indications that the faint-end slope of the far-IR LF is sufficiently flat that comoving luminosity density is dominated by bright objects (≃L*). However, we find that the number density/luminosity of such sources at high redshifts has been severely overestimated by studies that have attempted to push the highly confused Herschel SPIRE surveys beyond z ≃ 2. Consequently, we confirm recent reports that cosmic star formation density is dominated by UV-visible star formation at z > 4. Using both direct (1/V
max) and maximum likelihood determinations of the LF, we find that its high-redshift evolution is well characterized by continued positive luminosity evolution coupled with negative density evolution (with increasing redshift). This explains why bright sub-mm sources continue to be found at z > 5, even though their integrated contribution to cosmic star formation density at such early times is very small. The evolution of the far-IR galaxy LF thus appears similar in form to that already established for active galactic nuclei, possibly reflecting a similar dependence on the growth of galaxy mass.
We present new empirical constraints on the evolution of \({\rho }_{{{\rm{H}}}_{2}}\), the cosmological mass density of molecular hydrogen, back to z ≈ 2.5. We employ a statistical approach measuring ...the average observed 850 μm flux density of near-infrared selected galaxies as a function of redshift. The redshift range considered corresponds to a span where the 850 μm band probes the Rayleigh–Jeans tail of thermal dust emission in the rest frame, and can therefore be used as an estimate of the mass of the interstellar medium. Our sample comprises of ≈150,000 galaxies in the UK InfraRed Telescope Infrared Deep Sky Survey Ultra-Deep Survey field with near-infrared magnitudes K AB ≤ 25 mag and photometric redshifts with corresponding probability distribution functions derived from deep 12-band photometry. With a sample approximately 2 orders of magnitude larger than in previous works we significantly reduce statistical uncertainties on \({\rho }_{{{\rm{H}}}_{2}}\) to z ≈ 2.5. Our measurements are in broad agreement with recent direct estimates from blank field molecular gas surveys, finding that the epoch of molecular gas coincides with the peak epoch of star formation with \({\rho }_{{{\rm{H}}}_{2}}\approx 2\times {10}^{7}\,{M}_{\odot }\,{\mathrm{Mpc}}^{-3}\) at z ≈ 2. We demonstrate that \({\rho }_{{{\rm{H}}}_{2}}\) can be broadly modeled by inverting the star formation rate (SFR) density with a fixed or weakly evolving star formation efficiency. This “constant efficiency” model shows a similar evolution to our statistically derived \({\rho }_{{{\rm{H}}}_{2}}\), indicating that the dominant factor driving the peak star formation history at z ≈ 2 is a larger supply of molecular gas in galaxies rather than a significant evolution of the SFR efficiency within individual galaxies.
Motexafin gadolinium is a magnetic resonance imaging (MRI)--detectable redox active drug that localizes selectively in tumor cells and enhances the effect of radiation therapy. This phase Ib/II trial ...of motexafin gadolinium, administered concurrently with 30 Gy in 10 fractions whole-brain radiation therapy (WBRT), was conducted to determine maximum-tolerated dose (MTD), dose-limiting toxicity, pharmacokinetics, and biolocalization in patients with brain metastases. Additional endpoints were radiologic response rate and survival.
Motexafin gadolinium was administered before each radiation treatment in this open-label, multicenter, international trial. In phase Ib, drug dose was escalated until the MTD was exceeded. In phase II, drug was evaluated in a narrow dose range.
In phase Ib, the motexafin gadolinium dose was escalated in 39 patients (0.3 mg/kg to 8.4 mg/kg). In phase II, 22 patients received 5 mg/kg to 6.3 mg/kg motexafin gadolinium. Ten once-daily treatments were well tolerated. The MTD was 6.3 mg/kg, with dose-limiting reversible liver toxicity. Motexafin gadolinium's tumor selectivity was established using MRI. The radiologic response rate was 72% in phase II. Median survival was 4.7 months for all patients, 5.4 months for recursive partitioning analysis (RPA) class 2 patients, and 3.8 months for RPA class 3 patients. One-year actuarial survival for all patients was 25%.
Motexafin gadolinium was well tolerated at doses up to 6.3 mg/kg, was selectively accumulated in tumors, and, when combined with WBRT of 30 Gy in 10 fractions, was associated with a high radiologic response rate.
Plant genetic engineering led to the production of plant-derived mAb (mAbP), which provides a safe and economically feasible alternative to the current methods of antibody production in animal ...systems. In this study, the heavy and light chains of human anti-rabies mAb were expressed and assembled in planta under the control of two strong constitutive promoters. An alfalfa mosaic virus untranslated leader sequence and Lys-Asp-Glu-Leu (KDEL) endoplasmic reticulum retention signal were linked at the N and C terminus of the heavy chain, respectively. mAbPwas as effective at neutralizing the activity of the rabies virus as the mammalian-derived antibody (mAbM) or human rabies Ig (HRIG). The mAbPcontained mainly oligomannose type N-glycans (90%) and had no potentially antigenic α(1,3)-linked fucose residues. mAbPhad a shorter half-life than mAbM. The mAbPwas as efficient as HRIG for post-exposure prophylaxis against rabies virus in hamsters, indicating that differences in N-glycosylation do not affect the efficacy of the antibody in this model.
We use a sample of 4209 Lyman-break galaxies (LBGs) at z ≃ 3, 4, and 5 in the UKIRT Infrared Deep Sky Survey Ultra Deep Survey field to investigate the relationship between the observed slope of the ...stellar continuum emission in the ultraviolet, β, and the thermal dust emission, as quantified via the so-called 'infrared excess' (IRX=LIR/LUV). Through a stacking analysis, we directly measure the 850-μm flux density of LBGs in our deep (0.9 mJy) James Clerk Maxwell Telescope SCUBA-2 850-μm map as well as deep public Herschel/SPIRE 250-, 350-, and 500-μm imaging. We establish functional forms for the IRX-β relation to z ~ 5, confirming that there is no significant redshift evolution of the relation, and that the resulting average IRX-β curve is consistent with a Calzetti-like attenuation law. Comparing our results with recent works in the literature, we confirm that discrepancies in the slope of the IRX-β relation are driven by biases in the methodology used to determine the ultraviolet slopes. Consistent results are found when IRX-β is evaluated by stacking in bins of stellar mass, and we argue that the near-linear IRX-M* relationship is a better proxy for correcting observed ultraviolet luminosities to total star formation rates, provided an accurate handle on M* and also gives clues as to the physical driver of the role of dust-obscured star formation in high-redshift galaxies.
Long gamma-ray bursts (GRBs), among the most energetic events in the Universe, are explosions of massive and short-lived stars, so they pinpoint locations of recent star formation. However, several ...GRB host galaxies have recently been found to be deficient in molecular gas (H2), believed to be the fuel of star formation. Moreover, optical spectroscopy of GRB afterglows implies that the molecular phase constitutes only a small fraction of the gas along the GRB line of sight. Here we report the first ever 21 cm line observations of GRB host galaxies, using the AustraliaTelescope Compact Array, implying high levels of atomic hydrogen (H i), which suggests that the connection between atomic gas and star formation is stronger than previously thought. In this case, it is possible that star formation is directly fuelled by atomic gas (or that the H i-to-H2 conversion is very efficient, which rapidly exhaust molecular gas), as has been theoretically shown to be possible. This can happen in low-metallicity gas near the onset of star formation because cooling of gas (necessary for star formation) is faster than the H i-to-H2 conversion. Indeed, large atomic gas reservoirs, together with low molecular gas masses, stellar, and dust masses are consistent with GRB hosts being preferentially galaxies which have very recently started a star formation episode after accreting metal-poor gas from the intergalactic medium. This provides a natural route for forming GRBs in low-metallicity environments. The gas inflow scenario is also consistent with the existence of the companion H I object with no optical counterpart ~19 kpc from the GRB 060505 host, and with the fact that the H I centroids of the GRB 980425 and 060505 hosts do not coincide with optical centres of these galaxies, but are located close to the GRB positions.
Abstract
We present new empirical constraints on the evolution of
, the cosmological mass density of molecular hydrogen, back to
z
≈ 2.5. We employ a statistical approach measuring the average ...observed 850
μ
m flux density of near-infrared selected galaxies as a function of redshift. The redshift range considered corresponds to a span where the 850
μ
m band probes the Rayleigh–Jeans tail of thermal dust emission in the rest frame, and can therefore be used as an estimate of the mass of the interstellar medium. Our sample comprises of ≈150,000 galaxies in the UK InfraRed Telescope Infrared Deep Sky Survey Ultra-Deep Survey field with near-infrared magnitudes
K
AB
≤ 25 mag and photometric redshifts with corresponding probability distribution functions derived from deep 12-band photometry. With a sample approximately 2 orders of magnitude larger than in previous works we significantly reduce statistical uncertainties on
to
z
≈ 2.5. Our measurements are in broad agreement with recent direct estimates from blank field molecular gas surveys, finding that the epoch of molecular gas coincides with the peak epoch of star formation with
at
z
≈ 2. We demonstrate that
can be broadly modeled by inverting the star formation rate (SFR) density with a fixed or weakly evolving star formation efficiency. This “constant efficiency” model shows a similar evolution to our statistically derived
, indicating that the dominant factor driving the peak star formation history at
z
≈ 2 is a larger supply of molecular gas in galaxies rather than a significant evolution of the SFR efficiency within individual galaxies.
Gamma-ray bursts (GRBs) have been proposed as a tool for studying star formation in the Universe, so it is crucial to investigate whether their host galaxies and immediate environments are in any way ...special compared with other star-forming galaxies. Here we present spatially resolved maps of dust emission of the host galaxyof the closest known GRB 980425 at z = 0.0085 using our new high-resolution observations from Herschel, Atacama Pathfinder Experiment (APEX), Atacama Large Millimeter Array (ALMA) and Australia Telescope Compact Array (ATCA). We modelled the spectral energy distributions of the host and of the star-forming region displaying the Wolf-Rayet signatures in the spectrum (WR region), located 800 pc from the GRB position. The host is characterised by low dust content and a high fraction of UV-visible star formation, similar to other dwarf galaxies. These galaxies are abundant in the local universe, so it is not surprising to find a GRB in one of them, assuming the correspondence between the GRB rate and star formation. The WR region contributes substantially to the host emission at the far-infrared, millimetre, and radio wavelengths and we propose that this is a consequence of its high gas density. If dense environments are also found close to the positions of other GRBs, then the ISM density should also be considered, along with metallicity, an important factor influencing whether a given stellar population can produce a GRB.
Inflow of atomic gas fuelling star formation Michałowski, M. J.; Gentile, G.; Hjorth, J. ...
Proceedings of the International Astronomical Union,
08/2015, Letnik:
11, Številka:
A29B
Journal Article
Recenzirano
Odprti dostop
Gamma-ray burst host galaxies are deficient in molecular gas, and show anomalous metal-poor regions close to GRB positions. Using recent Australia Telescope Compact Array (ATCA) Hi observations we ...show that they have substantial atomic gas reservoirs. This suggests that star formation in these galaxies may be fuelled by recent inflow of metal-poor atomic gas. While this process is debated, it can happen in low-metallicity gas near the onset of star formation because gas cooling (necessary for star formation) is faster than the Hi-to-H2 conversion.
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