Double-peaked Lyman α emission at z = 6.803: a reionization-era galaxy self-ionizing its local H II bubble

We report the discovery of a double-peaked Lyman α profile in a galaxy at z = 6.803, A370p_z1, in the parallel Frontier Field of Abell 370. The velocity separation between the blue and red peaks of the Lyman α profile (⁠Δ v = 101^{+38}_{-19}(±48)km s^{-1}) suggests an extremely high escape fraction of ionizing photons >59(51) per cent (2σ). The spectral energy distribution indicates a young (50 Myr), star-forming (⁠12 ± 6M_{⊙}yr^{-1}) galaxy with an IRAC excess implying strong [O III] + H β emission. On the basis of the high escape fraction measured, we demonstrate that A370p_z1 was solely capable of creating an ionized bubble sufficiently large to account for the blue component of its Lyman α profile. We discuss whether A370p_z1 may be representative of a larger population of luminous z ≃ 7 double-peaked Lyman α emitting sources with high escape fractions that self-ionized their surroundings without contributions from associated ultraviolet-fainter sources

Three Lyα Emitting Galaxies within a Quasar Proximity Zone at z ~ 5.8

Quasar proximity zones at z > 5.5 correspond to overdense and overionized environments. Galaxies found inside proximity zones can therefore display features that would otherwise be masked by absorption in the intergalactic medium. We demonstrate the utility of this quasar-galaxy synergy by reporting the discovery of the first three “proximate Lyα emitters” (LAEs) within the proximity zone of quasar J0836+0054 at z = 5.795 (Aerith A, B, and C). Aerith A, located behind the quasar with an impact parameter D^{\perp} = 278 \pm 8 pkpc, provides the first detection of an Lyα transverse proximity effect. We model the transmission and show that it constrains the onset of J0836ʼs quasar phase to 0.2Myr < 28Myr < t in the past. The second object, Aerith B at a distance D < 912 pkpc from the quasar, displays a bright and broad double-peaked Lyα emission line. The peak separation implies a low ionizing f_{esc} \leqslant 1%. We fit the Lyα line with an outflowing shell model, finding a typical central density log N_{HI}/cm^{-2} = 19.3_{-0.2}^{+0.8}, outflow velocity v_{out} = 16_{-11}^{+4}km s^{-1}, and gas temperature log T/K = 3.8_{-0.7}^{+0.8} compared to 2 < z < 3 analog LAEs. We detect object Aerith C via an Lyα emission line at z = 5.726. This corresponds with the edge of the quasar’s proximity zone (Dz < 0.02), suggesting that the proximity zone is truncated by a density fluctuation. Via the analyses conducted here, we illustrate how proximate LAEs offer unique insight into the ionizing properties of both quasars and galaxies during hydrogen reionization

Probing cosmic dawn: Ages and star formation histories of candidate z ≥ 9 galaxies

We discuss the spectral energy distributions and physical properties of six galaxies whose photometric redshifts suggest they lie beyond a redshift z ≃ 9. Each was selected on account of a prominent excess seen in the Spitzer/IRAC 4.5 μm band which, for a redshift above z = 9.0, likely indicates the presence of a rest-frame Balmer break and a stellar component that formed earlier than a redshift z ≃ 10. In addition to constraining the earlier star formation activity on the basis of fits using stellar population models with BAGPIPES, we have undertaken the necessary, but challenging, follow-up spectroscopy for each candidate using various combinations of Keck/MOSFIRE, VLT/X-shooter, Gemini/FLAMINGOS2, and ALMA. Based on either Lyman-α or [O III] 88 μm emission, we determine a convincing redshift of z = 8.78 for GN-z-10-3 and a likely redshift of z = 9.28 for the lensed galaxy MACS0416-JD. For GN-z9-1, we conclude the case remains promising for a source beyond z ≃ 9. Together with earlier spectroscopic data for MACS1149-JD1, our analysis of this enlarged sample provides further support for a cosmic star formation history extending beyond redshifts z ≃ 10. We use our best-fitting stellar population models to reconstruct the past rest-frame UV luminosities of our sources and discuss the implications for tracing earlier progenitors of such systems with the James Webb Space Telescope

Microarray studies reveal novel genes associated with endocrine resistance in breast cancer

Background Endocrine resistance is a major hurdle in breast cancer management, and determining the underlying factors driving its growth and aggressive behaviour should vastly improve treatment. Methods Microarray technology (BD Atlas Plastic Human 12 K Microarrays; GeneSifter software), verified by PCR, western blotting and immunocytochemisty, was used to identify genes increased in acquired resistant models to tamoxifen (TamR) or faslodex (FasR) as potential predictive/prognostic markers and new therapeutic targets. Results Alongside known breast cancer genes (β-catenin, PEA3, vitronectin, CD44), two novel genes in endocrine resistance were revealed (the latter never previously described in breast cancer): a securin/cell cycle regulator Pituitary Tumour Transforming Gene-1 (PTTG1), and GDNF receptor-alpha 3 (GFRα3) reported to promote cell survival signalling via RET coreceptor. Altered levels of PTTG1, GFRα3, or their associated family members were observed in further endocrine resistant states, including an additional faslodex resistant model that has progressed to a highly-aggressive state (FasR-Lt) and XMCF-7 cells resistant to oestrogen deprivation. PTTG1 and GFRα3 induction were also implicated in limiting response to anti-EGFR agents currently in breast cancer trials, with GFRα3 ligand (artemin) largely overcoming drug response. mRNA studies in clinical disease revealed PTTG1 associated with lymph node spread, high tumour grade and proliferation, while GFRα3 was enriched in ER-negative tumours and those expressing EGFR, profiles implying roles in clinical resistance and aggressive tumour behaviour. Promisingly, PTTG1 or GFRα3 siRNA knockdown promoted cell kill and inhibited proliferation in the resistant models. Conclusion Cumulatively, these data indicate PTTG1 and GFRα3 may provide useful biomarkers, and perhaps clinically relevant therapeutic targets for multiple resistant states

New constraints on quasar evolution: broad-line velocity shifts over 1.5 ≲ z ≲ 7.5

We present the results of a model-independent investigation of the rest-frame UV spectra from a comprehensive sample of $394$ quasars in the redshift range $1.5\leq z \leq 7.5$. We fit the main Broad Emission Lines (BELs) in the rest-frame range $1280 \text{\AA} \leq \lambda \leq 3000 \text{\AA}$ (O I, C II, Si IV, C III, C IV and Mg II) with a lightly-supervised spline fitting technique. Redshifts are derived from the peaks of each fitted BEL and used to compute relative velocity shifts. We show that our method gives unbiased velocity shifts and is insensitive to spectral resolution and instrumental parameters. It is found that the average blueshift of the \cfour\, line with respect to several low-ionisation lines in luminosity-matched samples does not significantly evolve over $1.5\gtrsim z\gtrsim6$. However, the average blueshift increases significantly by a factor $\sim 2.5$ at $z\gtrsim 6$. We propose that this redshift evolution can be explained by \cfour\, winds launched perpendicularly to an accretion disk with increased torus opacity at high-redshift, coupled with a potential orientation-driven selection bias. Our results open new exciting avenues of investigation into young quasars in the reionisation epoch

Genetic improvement of wheat for dry environments - a trait based approach

Item does not contain fulltext23 januari 201

Mass extinctions and supernova explosions

A nearby supernova (SN) explosion could have negatively influenced life on Earth, maybe even been responsible for mass extinctions. Mass extinction poses a significant extinction of numerous species on Earth, as recorded in the paleontologic, paleoclimatic, and geological record of our planet. Depending on the distance between the Sun and the SN, different types of threats have to be considered, such as ozone depletion on Earth, causing increased exposure to the Sun's ultraviolet radiation, or the direct exposure of lethal x-rays. Another indirect effect is cloud formation, induced by cosmic rays in the atmosphere which result in a drop in the Earth's temperature, causing major glaciations of the Earth. The discovery of highly intensive gamma ray bursts (GRBs), which could be connected to SNe, initiated further discussions on possible life-threatening events in Earth's history. The probability that GRBs hit the Earth is very low. Nevertheless, a past interaction of Earth with GRBs and/or SNe cannot be excluded and might even have been responsible for past extinction events.Comment: Chapter for forthcoming book: Handbook of Supernovae, P. Murdin and A. Alsabeti (eds.), Springer International Publishing (in press