ALBERT

Description: We present Early Science observations with the Large Millimeter Telescope, AzTEC 1.1 mm continuum images and wide bandwidth spectra (73–111 GHz) acquired with the Redshift Search Receiver, towards four bright lensed submillimetre galaxies identified through the Herschel Lensing Survey-snapshot and the Submillimetre Common-User Bolometer Array-2 Cluster Snapshot Survey. This pilot project studies the star formation history and the physical properties of the molecular gas and dust content of the highest redshift galaxies identified through the benefits of gravitational magnification. We robustly detect dust continuum emission for the full sample and CO emission lines for three of the targets. We find that one source shows spectroscopic multiplicity and is a blend of three galaxies at different redshifts ( z  = 2.040, 3.252, and 4.680), reminiscent of previous high-resolution imaging follow-up of unlensed submillimetre galaxies, but with a completely different search method, that confirm recent theoretical predictions of physically unassociated blended galaxies. Identifying the detected lines as 12 CO ( J up  = 2–5) we derive spectroscopic redshifts, molecular gas masses, and dust masses from the continuum emission. The mean H 2 gas mass of the full sample is (2.0 ± 0.2)  x  10 11 M /μ, and the mean dust mass is (2.0 ± 0.2)  x  10 9 M /μ, where μ  2–5 is the expected lens amplification. Using these independent estimations we infer a gas-to-dust ratio of GDR   55–75, in agreement with other measurements of submillimetre galaxies. Our magnified high-luminosity galaxies fall on the same locus as other high-redshift submillimetre galaxies, extending the $L^{\prime }_{\rm CO}$ – L FIR correlation observed for local luminous and ultraluminous infrared galaxies to higher far-infrared and CO luminosities.

Description: The expansion of the GGGGCC hexanucleotide repeat in the non-coding region of the chromosome 9 open-reading frame 72 ( C9orf72 ) gene is the most common cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) (c9FTD/ALS). Recently, it was reported that an unconventional mechanism of repeat-associated non-ATG (RAN) translation arises from C9orf72 expansion. Sense and anti-sense transcripts of the expanded C9orf72 repeat, i.e. the dipeptide repeat protein (DRP) of glycine–alanine (poly-GA), glycine–proline (poly-GP), glycine–arginine (poly-GR), proline–arginine (poly-PR) and proline–alanine (poly-PA), are deposited in the brains of patients with c9FTD/ALS. However, the pathological significance of RAN-translated peptides remains unknown. We generated synthetic cDNAs encoding 100 repeats of DRP without a GGGGCC repeat and evaluated the effects of these proteins on cultured cells and cortical neurons in vivo. Our results revealed that the poly-GA protein formed highly aggregated ubiquitin/p62-positive inclusion bodies in neuronal cells. In contrast, the highly basic proteins poly-GR and PR also formed unique ubiquitin/p62-negative cytoplasmic inclusions, which co-localized with the components of RNA granules. The evaluation of cytotoxicity revealed that overexpressed poly-GA, poly-GP and poly-GR increased the substrates of the ubiquitin–proteasome system (UPS), including TDP-43, and enhanced the sensitivity to a proteasome inhibitor, indicating that these DRPs are cytotoxic, possibly via UPS dysfunction. The present data indicate that a gain-of-function mechanism of toxic DRPs possibly contributes to pathogenesis in c9FTD/ALS and that DRPs may serve as novel therapeutic targets in c9FTD/ALS.

Description: We present statistical properties of diffuse Lyα haloes (LAHs) around high- z star-forming galaxies with large Subaru samples of Lyα emitters (LAEs) at z = 2.2. We make subsamples defined by the physical quantities of LAEs’ central Lyα luminosities, ultraviolet (UV) magnitudes, Lyα equivalent widths, and UV slopes, and investigate LAHs’ radial surface brightness (SB) profiles and scale lengths r n as a function of these physical quantities. We find that there exist prominent LAHs around LAEs with faint Lyα luminosities, bright UV luminosities, and small Lyα equivalent widths in cumulative radial Lyα SB profiles. We confirm this trend with the anticorrelation between r n and Lyα luminosities (equivalent widths) based on the Spearman's rank correlation coefficient that is = –0.9 (–0.7) corresponding to the 96 per cent (93 per cent) confidence level, although the correlation between r n and UV magnitudes is not clearly found in the rank correlation coefficient. Our results suggest that LAEs with properties similar to typical Lyman-break galaxies (with faint Lyα luminosities and small equivalent widths) possess more prominent LAHs. We investigate scenarios for the major physical origins of LAHs with our results. Because we find relatively small Lyα equivalent widths up to 77 Å in LAHs that include LAEs’ central components, these results suggest that the cold stream scenario is not preferred. There remain two possible scenarios of Lyα scattering in circumgalactic medium and satellite galaxies that cannot be tested with our observational data.

Description: Context. Ultraviolet (UV) emission-line spectra are used to spectroscopically confirm high-z galaxies and increasingly also to determine their physical properties. Aims. We construct photoionization models to interpret the observed UV spectra of distant galaxies in terms of the dominant radiation field and the physical condition of the interstellar medium (ISM). These models are applied to new spectroscopic observations from the VIMOS Ultra Deep Survey (VUDS). Methods. We construct a large grid of photoionization models, which use several incident radiation fields (stellar populations, active galactic nuclei (AGNs), mix of stars and AGNs, blackbodies, and others), and cover a wide range of metallicities and ionization parameters. From these models we derive new spectral UV line diagnostics using equivalent widths (EWs) of [CIII]λ1909 doublet, CIVλ1549 doublet and the line ratios of [CIII], CIV, and He IIλ1640 recombination lines. We apply these diagnostics to a sample of 450 [CIII]-emitting galaxies at redshifts z = 2–4 previously identified in VUDS. Results. We demonstrate that our photoionization models successfully reproduce observations of nearby and high-redshift sources with known radiation field and/or metallicity. For star-forming galaxies our models predict that [CIII] EW peaks at sub-solar metallicities, whereas CIV EW peaks at even lower metallicity. Using the UV diagnostics, we show that the average star-forming galaxy (EW([CIII]) ~ 2 Å) based on the composite of the 450 UV-selected galaxies’ spectra The inferred metallicity and ionization parameter is typically Z = 0.3–0.5 Z⊙ and logU = −2.7 to − 3, in agreement with earlier works at similar redshifts. The models also indicate an average age of 50–200 Myr since the beginning of the current star-formation, and an ionizing photon production rate, ξion, of logξion/erg−1 Hz = 25.3–25.4. Among the sources with EW([CIII]) 〉= 10 Å, approximately 30% are likely dominated by AGNs. The metallicity derived for galaxies with EW(CIII) = 10–20 Å is low, Z = 0.02–0.2 Z⊙, and the ionization parameter higher (logU ~−1.7) than the average star-forming galaxy. To explain the average UV observations of the strongest but rarest [CIII] emitters (EW([CIII]) 〉 20 Å), we find that stellar photoionization is clearly insufficient. A radiation field consisting of a mix of a young stellar population (logξion/erg−1 Hz ~ 25.7) plus an AGN component is required. Furthermore an enhanced C/O abundance ratio (up to the solar value) is needed for metallicities Z = 0.1–0.2 Z⊙ and logU = −1.7 to − 1.5. Conclusions. A large grid of photoionization models has allowed us to propose new diagnostic diagrams to classify the nature of the ionizing radiation field (star formation or AGN) of distant galaxies using UV emission lines, and to constrain their ISM properties. We have applied this grid to a sample of [CIII]-emitting galaxies at z = 2–4 detected in VUDS, finding a range of physical properties and clear evidence for significant AGN contribution in rare sources with very strong [CIII] emission. The UV diagnostics we propose should also serve as an important basis for the interpretation of upcoming observations of high-redshift galaxies.

Description: Alpha-synuclein (αSyn) plays a central role in the pathogenesis of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Recent multicenter genetic studies have revealed that mutations in the glucocerebrosidase 1 ( GBA1 ) gene, which are responsible for Gaucher's disease, are strong risk factors for PD and DLB. However, the mechanistic link between the functional loss of glucocerebrosidase (GCase) and the toxicity of αSyn in vivo is not fully understood. In this study, we employed Drosophila models to examine the effect of GCase deficiency on the neurotoxicity of αSyn and its molecular mechanism. Behavioral and histological analyses showed that knockdown of the Drosophila homolog of GBA1 ( dGBA1 ) exacerbates the locomotor dysfunction, loss of dopaminergic neurons and retinal degeneration of αSyn-expressing flies. This phenotypic aggravation was associated with the accumulation of proteinase K (PK)-resistant αSyn, rather than with changes in the total amount of αSyn, raising the possibility that glucosylceramide (GlcCer), a substrate of GCase, accelerates the misfolding of αSyn. Indeed, in vitro experiments revealed that GlcCer directly promotes the conversion of recombinant αSyn into the PK-resistant form, representing a toxic conformational change. Similar to dGBA1 knockdown, knockdown of the Drosophila homolog of β - galactosidase ( β-Gal ) also aggravated locomotor dysfunction of the αSyn flies, and its substrate GM1 ganglioside accelerated the formation of PK-resistant αSyn. Our findings suggest that the functional loss of GCase or β-Gal promotes the toxic conversion of αSyn via aberrant interactions between αSyn and their substrate glycolipids, leading to the aggravation of αSyn-mediated neurodegeneration.

Description: We present physical properties of spectroscopically confirmed Lyα emitters (LAEs) with very large rest-frame Lyα equivalent widths EW 0 (Lyα). Although the definition of large EW 0 (Lyα) LAEs is usually difficult due to limited statistical and systematic uncertainties, we identify six LAEs selected from ~3000 LAEs at z ~ 2 with reliable measurements of EW 0 (Lyα) ~= 200–400 Å given by careful continuum determinations with our deep photometric and spectroscopic data. These large EW 0 (Lyα) LAEs do not have signatures of AGN, but notably small stellar masses of M * = 10 7–8 M and high specific star formation rates (star formation rate per unit galaxy stellar mass) of ~100 Gyr –1 . These LAEs are characterized by the median values of L (Lyα) = 3.7 x 10 42  erg s –1 and M UV = –18.0 as well as the blue UV continuum slope of β = –2.5 ± 0.2 and the low dust extinction $E(B-V)_{\rm *} = 0.02^{+0.04}_{-0.02}$ , which indicate a high median Lyα escape fraction of $f_{\rm esc}^{\rm Ly\alpha }=0.68\pm 0.30$ . This large $f_{\rm esc}^{\rm Ly\alpha }$ value is explained by the low H i column density in the interstellar medium which is consistent with full width at half-maximum (FWHM) of the Lyα line, FWHM(Lyα) = 212 ± 32 km s –1 , significantly narrower than those of small EW 0 (Lyα) LAEs. Based on the stellar evolution models, our observational constraints of the large EW 0 (Lyα), the small β, and the rest-frame He ii EW imply that at least a half of our large EW 0 (Lyα) LAEs would have young stellar ages of 20 Myr and very low metallicities of Z 〈 0.02 Z regardless of the star formation history.

Description: We analyze the CIII]-λ1908 Å emission properties in a sample of 3899 star-forming galaxies (SFGs) at 2 〈  z 〈  3.8 drawn from the VIMOS Ultra-Deep Survey (VUDS). We find a median rest-frame equivalent width EW(CIII]) = 2.0 ± 0.2 to 2.2 ± 0.2 Å for the whole SFG population at 2 〈  z 〈  3 and 3 〈  z 〈  4, respectively. About 24% of SFGs are showing EW(CIII]) 〉 3 Å, including ∼20% with modest emission 3 〈 EW(CIII]) 〈 10 Å and ∼4% with strong emission EW(CIII])〉 10 Å. A small but significant fraction of 1.2% of SFGs presents strong CIII] emission 20 〈 EW(CIII]) 〈 40 Å; the four strongest emitters (EW(CIII]) 〉 40 Å up to ∼95 Å) are associated with broad-line AGN. While this makes CIII] the second most frequent emission line in the UV rest-frame spectra of SFGs after Lyman-α, this line alone cannot be considered an efficient substitute for measuring a galaxy redshift in the absence of Lyα emission, unless the spectral resolution is R 〉  3000 to distinguish among different possible doublets. We find a large dispersion in the weak correlation between EW(CIII]) and EW(Lyα), with galaxies showing strong CIII] and no Lyα, and vice versa. The spectra of SFGs with 10 〈 EW(CIII]) 〈 40 Å present strong emission lines that include CIV-λ1549, HeII-λ1640, and OIII-λ1664, but also weaker emission features of highly ionized elements such as SiIV-λ1403, NIV-λ1485, NIII-λ1750, or SiIII-λ1888, indicating the presence of a hard radiation field. We present a broad range of observational evidence supporting the presence of AGN in the strong CIII] emitting population. As EW(CIII]) is rising, we identify increasingly powerful outflows with velocities up to 1014 km s−1; this is beyond what stellar winds are commonly producing. The strongest CIII] emitters are preferentially located below the main sequence of star-forming galaxies; the median star formation rate is reduced by a factor of two. In addition, we find that the median stellar age of the strongest emitters is ∼0.8 Gyr, which is about three times that of galaxies with EW(CIII]) 〈 10 Å. X-ray stacked imaging of the strong CIII] emitters sample show a marginal 2σ detection that is consistent with low-luminosity AGN log(LX(2−10 keV)) ∼ 42.9 erg s−1. Previously presented spectral line analysis and classification support that the strongest emitters require the presence of an AGN. We conclude that this complementary set of evidence is indicative of significant AGN feedback acting in SFGs at 2 〈  z 〈  3.8, and it strongly contributes to star formation quenching. We find that quenching timescales of ∼0.25−0.5 × 109 years are necessary for this AGN feedback to turn part of the star-forming galaxy population with Mstar 〉  1010 M⊙ at z ∼ 3 into the population of quiescent galaxies observed at redshift z ∼ 1−2.

Description: We have obtained the first complete ultraviolet (UV) spectrum of a strong Lyman continuum (LyC) emitter at low redshift – the compact, low-metallicity, star-forming galaxy J1154+2443 – with a Lyman continuum escape fraction of 46% discovered recently. The Space Telescope Imaging Spectrograph spectrum shows strong Lyα and C III] λ1909 emission, as well as O III] λ1666. Our observations show that strong LyC emitters can have UV emission lines with a high equivalent width (e.g. EW(C III]) = 11.7 ± 2.9 Å rest-frame), although their equivalent widths should be reduced due to the loss of ionizing photons. The intrinsic ionizing photon production efficiency of J1154+2443 is high, log(ξ0ion = 25.56 erg−1 Hz), comparable to that of other recently discovered z ~ 0.3−0.4 LyC emitters. Combining our measurements and earlier determinations from the literature, we find a trend of increasing ξ0ion with increasing C III] λ1909 equivalent width, which can be understood by a combination of decreasing stellar population age and metallicity. Simple ionization and density-bounded photoionization models can explain the main observational features including the UV spectrum of J1154+2443.

Description: Observations have shown that massive star-forming clumps are present in the internal structure of high-redshift galaxies. One way to study these clumps in detail with a higher spatial resolution is by exploiting the power of strong gravitational lensing which stretches images on the sky. In this work, we present an analysis of the clumpy galaxy A68-HLS115 at z = 1.5858, located behind the cluster Abell 68, but strongly lensed by a cluster galaxy member. Resolved observations with SINFONI/VLT in the near-infrared (NIR) show Hα, Hβ, [NII], and [OIII] emission lines. Combined with images covering the B band to the far-infrared (FIR) and CO(2–1) observations, this makes this galaxy one of the only sources for which such multi-band observations are available and for which it is possible to study the properties of resolved star-forming clumps and to perform a detailed analysis of the integrated properties, kinematics, and metallicity. We obtain a stability of υrot/σ0 = 2.73 by modeling the kinematics, which means that the galaxy is dominated by rotation, but this ratio also indicates that the disk is marginally stable. We find a high intrinsic velocity dispersion of 80 ± 10 km s−1 that could be explained by the high gas fraction of fgas = 0.75 ± 0.15 observed in this galaxy. This high fgas and the observed sSFR of 3.12 Gyr−1 suggest that the disk turbulence and instabilities are mostly regulated by incoming gas (available gas reservoir for star formation). The direct measure of the Toomre stability criterion of Qcrit = 0.70 could also indicate the presence of a quasi-stable thick disk. Finally, we identify three clumps in the Hα map which have similar velocity dispersions, metallicities, and seem to be embedded in the rotating disk. These three clumps contribute together to ∼40% on the SFRHα of the galaxy and show a star formation rate density about ∼100 times higher than HII regions in the local Universe.