Active Disk Building in a local HI-Massive LIRG: The Synergy between Gas, Dust, and Star Formation

HIZOA J0836-43 is the most HI-massive (M_HI = 7.5x10^10 Msun) galaxy detected in the HIPASS volume and lies optically hidden behind the Milky Way. Markedly different from other extreme HI disks in the local universe, it is a luminous infrared galaxy (LIRG) with an actively star forming disk (>50 kpc), central to its ~ 130 kpc gas disk, with a total star formation rate (SFR) of ~20.5 Msun yr^{-1}. Spitzer spectroscopy reveals an unusual combination of powerful polycyclic aromatic hydrocarbon (PAH) emission coupled to a relatively weak warm dust continuum, suggesting photodissociation region (PDR)-dominated emission. Compared to a typical LIRG with similar total infrared luminosity (L_TIR=10^11 Lsun), the PAHs in HIZOA J0836-43 are more than twice as strong, whereas the warm dust continuum (lambda > 20micron) is best fit by a star forming galaxy with L_TIR=10^10 Lsun. Mopra CO observations suggest an extended molecular gas component (H_2 + He > 3.7x10^9 Msun) and a lower limit of ~ 64% for the gas mass fraction; this is above average compared to local disk systems, but similar to that of z~1.5 BzK galaxies (~57%). However, the star formation efficiency (SFE = L_IR/L'_CO) for HIZOA J0836-43 of 140 Lsun (K km s^{-1} pc^2)^{-1} is similar to that of local spirals and other disk galaxies at high redshift, in strong contrast to the increased SFE seen in merging and strongly interacting systems. HIZOA J0836-43 is actively forming stars and building a massive stellar disk. Its evolutionary phase of star formation (M_stellar, SFR, gas fraction) compared to more distant systems suggests that it would be considered typical at redshift z~1. This galaxy provides a rare opportunity in the nearby universe for studying (at z~0.036) how disks were building and galaxies evolving at z~1, when similarly large gas fractions were likely more common.Comment: Accepted for publication in The Astrophysical Journal. 16 pages, 8 figure

Analysis of galaxy SEDs from far-UV to far-IR with CIGALE: Studying a SINGS test sample

Photometric data of galaxies covering the rest-frame wavelength range from far-UV to far-IR make it possible to derive galaxy properties with a high reliability by fitting the attenuated stellar emission and the related dust emission at the same time. For this purpose we wrote the code CIGALE (Code Investigating GALaxy Emission) that uses model spectra composed of the Maraston (or PEGASE) stellar population models, synthetic attenuation functions based on a modified Calzetti law, spectral line templates, the Dale & Helou dust emission models, and optional spectral templates of obscured AGN. Depending on the input redshifts, filter fluxes are computed for the model set and compared to the galaxy photometry by carrying out a Bayesian-like analysis. CIGALE was tested by analysing 39 nearby galaxies selected from SINGS. The reliability of the different model parameters was evaluated by studying the resulting expectation values and their standard deviations in relation to the input model grid. Moreover, the influence of the filter set and the quality of photometric data on the code results was estimated. For up to 17 filters between 0.15 and 160 mum, we find robust results for the mass, star formation rate, effective age of the stellar population at 4000 A, bolometric luminosity, luminosity absorbed by dust, and attenuation in the far-UV. A study of the mutual relations between the reliable properties confirms the dependence of star formation activity on morphology in the local Universe and indicates a significant drop in this activity at about 10^11 M_sol towards higher total stellar masses. The dustiest sample galaxies are present in the same mass range. [abridged]Comment: 22 pages, 21 figures, accepted for publication in A&

The IRX-beta relation on sub-galactic scales in star-forming galaxies of the Herschel Reference Survey

UV and optical surveys are essential to gain insight into the processes driving galaxy formation and evolution. The rest-frame UV emission is key to measure the cosmic SFR. However, UV light is strongly reddened by dust. In starburst galaxies, the UV colour and the attenuation are linked, allowing to correct for dust extinction. Unfortunately, evidence has been accumulating that the relation between UV colour and attenuation is different for normal star-forming galaxies when compared to starburst galaxies. It is still not understood why star-forming galaxies deviate from the UV colour-attenuation relation of starburst galaxies. Previous work and models hint that the role of the shape of the attenuation curve and the age of stellar populations have an important role. In this paper we aim at understanding the fundamental reasons to explain this deviation. We have used the CIGALE SED fitting code to model the far UV to the far IR emission of a set of 7 reasonably face-on spiral galaxies from the HRS. We have explored the influence of a wide range of physical parameters to quantify their influence and impact on the accurate determination of the attenuation from the UV colour, and why normal galaxies do not follow the same relation as starburst galaxies. We have found that the deviation can be best explained by intrinsic UV colour differences between different regions in galaxies. Variations in the shape of the attenuation curve can also play a secondary role. Standard age estimators of the stellar populations prove to be poor predictors of the intrinsic UV colour. These results are also retrieved on a sample of 58 galaxies when considering their integrated fluxes. When correcting the emission of normal star-forming galaxies for the attenuation, it is crucial to take into account possible variations in the intrinsic UV colour as well as variations of the shape of the attenuation curve.Comment: Accepted for publication in A&A, 18 pages, 14 figures. The paper with high resolution figures can be downloaded at http://www.oamp.fr/people/mboquien/HRS/boquien_IRX_beta.pd

The Herschel Multi-tiered Extragalactic Survey: HerMES

The Herschel Multi-tiered Extragalactic Survey, HerMES, is a legacy program designed to map a set of nested fields totalling ~380 deg^2. Fields range in size from 0.01 to ~20 deg^2, using Herschel-SPIRE (at 250, 350 and 500 \mu m), and Herschel-PACS (at 100 and 160 \mu m), with an additional wider component of 270 deg^2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the re-processed optical and ultra-violet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multi-wavelength understanding of galaxy formation and evolution. The survey will detect of order 100,000 galaxies at 5\sigma in some of the best studied fields in the sky. Additionally, HerMES is closely coordinated with the PACS Evolutionary Probe survey. Making maximum use of the full spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to: facilitate redshift determination; rapidly identify unusual objects; and understand the relationships between thermal emission from dust and other processes. Scientific questions HerMES will be used to answer include: the total infrared emission of galaxies; the evolution of the luminosity function; the clustering properties of dusty galaxies; and the properties of populations of galaxies which lie below the confusion limit through lensing and statistical techniques. This paper defines the survey observations and data products, outlines the primary scientific goals of the HerMES team, and reviews some of the early results.Comment: 23 pages, 17 figures, 9 Tables, MNRAS accepte

Rescue of heterochromatin organization in Hutchinson-Gilford progeria by drug treatment

Hutchinson-Gilford progeria (HGPS) is a premature aging syndrome associated with LMNA mutations. Progeria cells bearing the G608G LMNA mutation are characterized by accumulation of a mutated lamin A precursor (progerin), nuclear dysmorphism and chromatin disorganization. In cultured HGPS fibroblasts, we found worsening of the cellular phenotype with patient age, mainly consisting of increased nuclear-shape abnormalities, progerin accumulation and heterochromatin loss. Moreover, transcript distribution was altered in HGPS nuclei, as determined by different techniques. In the attempt to improve the cellular phenotype, we applied treatment with drugs either affecting protein farnesylation or chromatin arrangement. Our results show that the combined treatment with mevinolin and the histone deacetylase inhibitor trichostatin A dramatically lowers progerin levels, leading to rescue of heterochromatin organization and reorganization of transcripts in HGPS fibroblasts. These results suggest that morpho-functional defects of HGPS nuclei are directly related to progerin accumulation and can be rectified by drug treatment

Reduced expression of lamin A/C correlates with poor histological differentiation and prognosis in primary gastric carcinoma

<p>Abstract</p> <p>Background</p> <p>Lamin A/C is very important in DNA replication, RNA dependent transcription and nuclear stabilization. Reduced or absent lamin A/C expression has been found to be a common feature of a variety of different cancers. To investigate the role of lamin A/C in gastric carcinoma (GC) pathogenesis, we analyzed the correlations between the lamin A/C expression level and clinicopathological factors and studied its prognostic role in primary GC.</p> <p>Methods</p> <p>The expression of lamin A/C at mRNA level was detected by the reverse transcription-polymerase chain reaction (RT-PCR) and real time RT-PCR, and western blot was used to examine the protein expression. Lamin A/C expression and its prognostic significance were investigated by performing immunohistochemical analysis on a total of 126 GC clinical tissue samples.</p> <p>Results</p> <p>Both lamin A/C mRNA and protein expression were downregulated in the majority of tumours compared with corresponding normal gastric tissues (<it>p </it>= 0.011 and <it>p </it>= 0.036, respectively). Real time RT-PCR further validated that downregulation of lamin A/C is associated with poor histological differentiation (r = 0.438, <it>p </it>= 0.025). The immunohistochemical staining showed an evident decrease of lamin A/C expression in 55.6% (70/126) GC cases. Importantly, the negative lamin A/C expression correlated strongly with histological classification (r = 0.361, <it>p </it>= 0.034). Survival analysis revealed that patients with lamin A/C downregulation have a poorer prognosis (<it>p </it>= 0.034). In addition, lamin A/C expression was found to be an independent prognostic factor by multivariate analysis.</p> <p>Conclusion</p> <p>Data of this study suggest that lamin A/C is involved in the pathogenesis of GC, and it may serve as a valuable biomarker for assessing the prognosis for primary GC.</p

Farnesylated Nuclear Proteins Kugelkern and Lamin Dm0 Affect Nuclear Morphology by Directly Interacting with the Nuclear Membrane

Nuclear shape changes are observed during a variety of developmental processes, pathological conditions and ageing. Here, the molecular mechanism is analyzed how the farnesylated nuclear proteins interact with the nuclear envelope and deform the phospholipid bilayer