Depth-specific fluctuations of gene expression and protein abundance modulate the photophysiology in the seagrass <i>Posidonia oceanica</i>

Here we present the results of a multiple organizational level analysis conceived to identify acclimative/adaptive strategies exhibited by the seagrass Posidonia oceanica to the daily fluctuations in the light environment, at contrasting depths. We assessed changes in photophysiological parameters, leaf respiration, pigments, and protein and mRNA expression levels. The results show that the diel oscillations of P. oceanica photophysiological and respiratory responses were related to transcripts and proteins expression of the genes involved in those processes and that there was a response asynchrony between shallow and deep plants probably caused by the strong differences in the light environment. The photochemical pathway of energy use was more effective in shallow plants due to higher light availability, but these plants needed more investment in photoprotection and photorepair, requiring higher translation and protein synthesis than deep plants. The genetic differentiation between deep and shallow stands suggests the existence of locally adapted genotypes to contrasting light environments. The depth-specific diel rhythms of photosynthetic and respiratory processes, from molecular to physiological levels, must be considered in the management and conservation of these key coastal ecosystems

High-resolution imaging of stars, dust, and star formation in nuclear rings in galaxies

Original paper can be found at http://www.astrosociety.org/pubs/cs/222-252.html Copyright Astronomical Society of the PacificNuclear rings in barred spiral galaxies offer an opportunity to study starburst properties, as well as the evolution of star formation in the central regions of galaxies. To further our understanding in these areas, a large imaging survey of over 80 galaxies with previous evidence for the existence of nuclear ring structure has been performed in the Ha emission line and the B and I broad bands using the William Herschel Telescope. Here, we present images of a subset of these galaxies, which reveal well-resolved nuclear rings in Ha. The rings consist of numerous "hotspots" (i.e., Ha-bright star-forming regions). For each hotspot we calculate Ha equivalent widths and compare the results to population synthesis models to obtain age estimates. Typical cluster ages are no more than 10 Myr

Age dating a starburst: Gemini/CIRPASS observations of the core of M 83

Original paper can be found at: http://www.astrosociety.org/pubs/cs/309.html--Copyright Astronomical Society of the PacificThe circumnuclear starburst in NGC 5236 (M 83) has been studied photometrically by Harris et al. (2001) using HST/WFPC2 images in the broad-band near-UV and optical, as well as narrow-band H® and H¯ to derive colors and line equivalent widths for 45 clusters. Despite the excellent spatial resolution of these observations, optical photometric analyses such as this su®er from: (i) patchy (and not easily quanti¯able) dust extinction; (ii) the fact that the reddening vector parallels the evolutionary tracks in a two-color diagram; and (iii) selection e®ects, which tend to exclude the very youngest (t < 5 Myr) clusters which have strong emission lines, but only a weak stellar continuum. Additionally, it is not possible to distinguish an instantaneous burst of star formation from a constant star formation rate, on the basis of broad-band colors alone. [opening paragraph

Massive star formation in the central regions of spiral galaxies

Peer reviewe

The distribution of star formation in the central regions of spiral galaxies

Original paper can be found at http://www.virtualjournals.org/proceedings/confproceed/783.jsp Copyright American Institute of Physics. DOI: 10.1063/1.2034984 [Full text of this article is not available in the UHRA]Nuclear rings are characterized by their high star formation rates, and are believed to be the products of gas inflow towards the inner regions of spiral galaxies. We present first results from a statistical survey of these rings, aimed to provide an insight into their triggering mechanisms and star formation properties. We gathered photometric data for 22 nuclear star-forming rings from a larger H survey of nearby spirals, of which we highlight three interesting cases (NGC 1343, NGC 1530, and NGC 5953). The high-quality images reveal that the rings are comprised of several distinct star-forming clusters within a few kiloparsecs of the nucleus. We analyzed each nuclear ring to obtain morphological parameters such as ellipticity, position angle, and size. We then compute the equivalent widths of each H emitting (HII) region forming the nuclear ring. Using modern population synthesis models, we convert the equivalent widths into an estimate of the age of each cluster. In general, ages range from 1 Myr to 10 Myrs throughout the rings. We compare the ages to the positions along each ring to detect possible age-related patterns. Where a bar exists in the host galaxy, we determine the approximate intersection points of the bar to the ring to probe whether the youngest hotspots occur near this intersection. We find that three rings from the sample show age gradients or bisymmetries along the plane of the ring, and in one case the youngest cluster does indeed intersect with one of the bar's interaction points to the ring

Age-dating a star-burst with GEMINI/CIRPASS observations of the core of M83

‘The definitive version is available at www3.interscience.wiley.com '. Copyright WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim DOI: 10.1002/asna.200310186 [Full text of this article is not available in the UHRA]We present preliminary results from a set of near-IR integral field spectroscopic observations of the central, star-burst, regions of the barred spiral galaxy M83, obtained with CIRPASS on Gemini-S. We present maps in the Paβ and [FeII] 1.257 μm emission lines which appear surprisingly different. We outline the procedure in which we will use Paβ emission line strengths and measures of CO absorption to determine the relative and absolute ages of individual star-forming knots in the central kpc region of M83. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)Peer reviewe

The Circumnuclear Starburst in M83

Original paper can be found at http://www.virtualjournals.org/proceedings/confproceed/783.jsp Copyright American Institute of Physics. DOI: 10.1063/1.2034980 [Full text of this article is not available in the UHRA]We present results from near-infrared integral-field spectroscopy of the circumnuclear starburst in M83, using the CIRPASS instrument on Gemini South. The combination of Pa, CO (6,3), and [Fe II] equivalent width measurements over large contiguous regions allows us to track the spatial propagation of star formation across the ringlet, which is too heavily obscured to be properly analysed at optical wavelengths. We find the clearest evidence yet for an age gradient, with the youngest clusters found closest to where the dust lane crosses the ringlet. We discuss the implications for gas fueling by the bar