Star Forming Objects in the Tidal Tails of Compact Groups

A search for star forming objects belonging to tidal tails has been carried out in a sample of deep Halpha images of 16 compact groups of galaxies. A total of 36 objects with Halpha luminosity larger than 10^38 erg s-1 have been detected in five groups. The fraction of the total Halpha luminosity of their respective parent galaxies shown by the tidal objects is always below 5% except for the tidal features of HCG95, whose Halpha luminosity amounts to 65% of the total luminosity. Out of this 36 objects, 9 star forming tidal dwarf galaxy candidates have been finally identified on the basis of their projected distances to the nuclei of the parent galaxies and their total Halpha luminosities. Overall, the observed properties of the candidates resemble those previously reported for the so-called tidal dwarf galaxies.Comment: 5 gif figures. Accepted for publication in Astrophysical Journa

Alpine plants are on the move: Quantifying distribution shifts of Australian alpine plants through time

Aim Alpine plant species’ distributions are thought to have been shifting to higher elevations in response to climate change. By moving upslope, species can occupy cooler and more suitable environments as climate change warms their current ranges. Despite evidence of upslope migration in the northern hemisphere, there is limited evidence for elevational shifts in southern hemisphere plants. Our study aimed to determine if alpine plants in Australia have migrated upslope in the last 2 to 6 decades. Location Kosciuszko National Park, NSW, Australia. Methods We collated historic occurrence data for 36 Australian alpine plant species from herbarium specimens and historic field observations and combined these historic data with modern occurrence data collected in the field. Results Eleven of the thirty-six species had shifted upslope in mean elevation and four species showed downslope elevational shifts. The rate of change for upslope shifts varied between 4 and 10 m per year and the rate of change for most downslope shifts was between 4 and 8 m per year, with one species shifting downslope at a high rate of 18 m per year. Additionally, some species showed shifts upward in their upper range edge and/or upward or downward shifts in their lower range edge. Five species also showed range contractions in the difference between their lower and upper range edges over time, while two showed range expansions. We found no significant differences in elevational shifts through time among herbaceous dicotyledons, herbaceous monocotyledons and shrubs. Main Conclusions Plant elevational shifts are occurring rapidly in the Australian alpine zone. This may allow species to persist under climate change. However, if current warming trends continue, several species within the Australian alpine zone will likely run out of suitable habitat within a century

Behind the loss of salinity resistance during domestication: alternative eco-physiological strategies are revealed in tomato clade.

Salinity stress impairs growth and physiological performance in tomato, which is one of the most economically important vegetables and is widely cultivated in arid and semi-arid areas of the world. Plant landraces, which are heterogeneous, local adaptations of domesticated species, offer a unique opportunity to valorize available germplasm, underpinning the productivity, resilience, and adaptive capacity of staple crops in vulnerable environments. Here, we investigated the response of fully mature tomato plants from a commercial variety, an ancestral wild relative, and a landrace under short-term salinity exposure, as well as their ability to recover upon cessation of stress. The heterogeneous panel evaluated in this study revealed different adaptative strategies to cope the stress. Our data highlighted the ability of the tomato clade to handle low and intermediate salinity stress for short-term exposure time, as well as its capacity to recover after the cessation of stress, although inter- and intraspecific variations in morphological and physiological responses to salinity were observed. Overall, the landrace and the wild type performed similarly to control conditions under low salinity, demonstrating an improved ability to maintain ionic balance. In contrast, the commercial genotype showed susceptibility and severe symptoms even under low salinity, with pronounced reductions in K+/Na+ ratio, PSII photochemical efficiency, and photosynthetic pigments. This research confirmed that improved salt tolerant genotypes can lead to substantial, positive impacts on horticultural production. While the salt tolerance mechanism of domesticated tomato was efficient under mild stress conditions, it failed at higher salinity levels

The Relation Between Activity and Environment in Compact Groups of Galaxies

We present the results of the classification of spectral activity types for 193 galaxies from a new sample of 49 compact groups of galaxies in the southern hemisphere (SCGs). This sample was selected in automated fashion from a digitized galaxy catalogue, covering an area of ~5200 sq deg, around the South Galactic Pole. It is complete up to m ~14.5 in b_j for the brightest galaxy of the group. The spectral analysis of the SCG galaxies confirms the results previously obtained for a smaller sample of Hickson's compact groups (HCG). We confirm the luminosity-activity and morphology-activity relations, as well as the predominance of AGNs (41% of SCGs galaxies). We verified also that the number of early-type non-emission-line galaxies increases with the number of members in the group. The SCGs contain more star-forming galaxies (SFGs) and less non-emission-line galaxies than HCGs, which suggests that they probe a wider range of physical properties. The SFGs are composed in majority of HII Nucleus Galaxies, which have less intense star formation than starburst galaxies. The star formation activity in SCGs is, consequently, remarkably low. The SFGs show also evidence for nuclear activity. If these results are further confirmed, 70% of the galaxies in SCGs would then have an active nucleus, making these systems remarkably rich in AGNs. Curiously, however, this characteristic of CGs generally excludes Seyfert 1 galaxies.(Abridged)Comment: 53 pages, Latex, 9 encapsulated postscript figures, Accepted for publication in The Astronomical Journa

The ALHAMBRA photometric system

This paper presents the characterization of the optical range of the ALHAMBRA photometric system, a 20 contiguous, equal-width, medium-band CCD system with wavelength coverage from 3500A to 9700A. The photometric description of the system is done by presenting the full response curve as a product of the filters, CCD and atmospheric transmission curves, and using some first and second order moments of this response function. We also introduce the set of standard stars that defines the system, formed by 31 classic spectrophotometric standard stars which have been used in the calibration of other known photometric systems, and 288 stars, flux calibrated homogeneously, from the Next Generation Spectral Library (NGSL). Based on the NGSL, we determine the transformation equations between Sloan Digital Sky Survey (SDSS) ugriz photometry and the ALHAMBRA photometric system, in order to establish some relations between both systems. Finally we develop and discuss a strategy to calculate the photometric zero points of the different pointings in the ALHAMBRA project.Comment: Astronomical Journal on the 14th of January 201

Southern hemisphere plants show more delays than advances in flowering phenology

Shifts in flowering phenology have been studied in detail in the northern hemisphere and are a key plant response to climate change. However, there are relatively fewer data on species' phenological shifts in the southern hemisphere. We combined historic field data, data from herbarium specimens dating back to 1842 and modern field data for 37 Australian species to determine whether species were flowering earlier in the year than they had in the past. We also combined our results with data compiled in the southern and northern hemispheres, respectively, to determine whether southern hemisphere species are showing fewer advances in flowering phenology through time. Across our study species, we found that 12 species had undergone significant shifts in flowering time, with four species advancing their flowering and eight species delaying their flowering. The remaining 25 species showed no significant shifts in their flowering phenology. These findings are important because delays or lack of shifts in flowering phenology can lead to mismatches in trophic interactions between plants and pollinators or seed dispersers, which can have substantial impacts on ecosystem functioning and primary productivity. Combining our field results with data compiled from the literature showed that only 58.5% of southern hemisphere species were advancing their flowering time, compared with 81.6% of species that were advancing their flowering time in the northern hemisphere. Our study provides further evidence that it is not adequate for ecologists to assume that southern hemisphere ecosystems will respond to future climate change in the same way as ecosystems north of the Equator. Synthesis. Field data and data from the literature indicate that southern hemisphere species are showing fewer advances in their flowering phenology through time, especially in comparison to northern hemisphere species

J-PLUS: Identification of low-metallicity stars with artificial neural networks using SPHINX

We present a new methodology for the estimation of stellar atmospheric parameters from narrow- and intermediate-band photometry of the Javalambre Photometric Local Universe Survey (J-PLUS), and propose a method for target pre-selection of low-metallicity stars for follow-up spectroscopic studies. Photometric metallicity estimates for stars in the globular cluster M15 are determined using this method. By development of a neural-network-based photometry pipeline, we aim to produce estimates of effective temperature, $T_{\rm eff}$, and metallicity, [Fe/H], for a large subset of stars in the J-PLUS footprint. The Stellar Photometric Index Network Explorer, SPHINX, is developed to produce estimates of $T_{\rm eff}$ and [Fe/H], after training on a combination of J-PLUS photometric inputs and synthetic magnitudes computed for medium-resolution (R ~ 2000) spectra of the Sloan Digital Sky Survey. This methodology is applied to J-PLUS photometry of the globular cluster M15. Effective temperature estimates made with J-PLUS Early Data Release photometry exhibit low scatter, \sigma($T_{\rm eff}$) = 91 K, over the temperature range 4500 < $T_{\rm eff}$ (K) < 8500. For stars from the J-PLUS First Data Release with 4500 < $T_{\rm eff}$ (K) < 6200, 85 $\pm$ 3% of stars known to have [Fe/H] <-2.0 are recovered by SPHINX. A mean metallicity of [Fe/H]=-2.32 $\pm$ 0.01, with a residual spread of 0.3 dex, is determined for M15 using J-PLUS photometry of 664 likely cluster members. We confirm the performance of SPHINX within the ranges specified, and verify its utility as a stand-alone tool for photometric estimation of effective temperature and metallicity, and for pre-selection of metal-poor spectroscopic targets.Comment: 18 pages, 12 figure

Integral Field Spectroscopy of the Central Regions of 3C 120: Evidence of a Past Merging Event

IFS combined with HST WFPC imaging were used to characterize the central regions of the Seyfert 1 radio galaxy 3C 120. We carried out the analysis of the data, deriving intensity maps of different emission lines and the continua at different wavelengths from the observed spectra. Applying a 2D modeling to the HST images we decoupled the nucleus and the host galaxy, and analyzed the host morphology. The host is a highly distorted bulge dominated galaxy, rich in substructures. We developed a new technique to model the IFS data extending the 2D modeling. Using this technique we separated the Seyfert nucleus and the host galaxy spectra, and derived a residual data cube with spectral and spatial information of the different structures in 3C 120. Three continuum-dominated structures (named A, B, and C) and other three extended emission line regions (EELRs, named E1, E2 and E3) are found in 3C 120 which does not follow the general behavior of a bulge dominated galaxy. We also found shells in the central kpc that may be remnants of a past merging event in this galaxy. The origin of E1 is most probably due to the interaction of the radio-jet of 3C 120 with the intergalactic medium. Structures A, B, and the shell at the southeast of the nucleus seem to correspond to a larger morphological clumpy structure that may be a tidal tail, consequence of the past merging event. We found a bright EELR (E2) in the innermost part of this tidal tail, nearby the nucleus, which shows a high ionization level. The kinematics of the E2 region and its connection to the tidal tail suggest that the tail has channeled gas from the outer regions to the center.Comment: 55 pages, 18 figures and 5 tables Accepted by AP

Three Frontiers for the Future of Biodiversity Research Using Citizen Science Data

Citizen science is fundamentally shifting the future of biodiversity research. But although citizen science observations are contributing an increasingly large proportion of biodiversity data, they only feature in a relatively small percentage of research papers on biodiversity. We provide our perspective on three frontiers of citizen science research, areas that we feel to date have had minimal scientific exploration but that we believe deserve greater attention as they present substantial opportunities for the future of biodiversity research: sampling the undersampled, capitalizing on citizen science's unique ability to sample poorly sampled taxa and regions of the world, reducing taxonomic and spatial biases in global biodiversity data sets; estimating abundance and density in space and time, develop techniques to derive taxon-specific densities from presence or absence and presence-only data; and capitalizing on secondary data collection, moving beyond data on the occurrence of single species and gain further understanding of ecological interactions among species or habitats. The contribution of citizen science to understanding the important biodiversity questions of our time should be more fully realized

Stellar populations of galaxies in the ALHAMBRA survey up to z∼1z \sim 1. II. Stellar content of quiescent galaxies within the dust-corrected stellar mass−-colour and the UVJUVJ colour−-colour diagrams

Our aim is to determine the distribution of stellar population parameters (extinction, age, metallicity, and star formation rate) of quiescent galaxies within the rest-frame stellar mass$-$colour and $UVJ$ colour$-$colour diagrams corrected for extinction up to $z\sim1$. These novel diagrams reduce the contamination in samples of quiescent galaxies owing to dust-reddened galaxies, and they provide useful constraints on stellar population parameters. We set constraints on the stellar population parameters of quiescent galaxies combining the ALHAMBRA multi-filter photo-spectra with our SED-fitting code MUFFIT, making use of composite stellar population models. The extinction obtained by MUFFIT allowed us to remove dusty star-forming (DSF) galaxies from the sample of red $UVJ$ galaxies. The distributions of stellar population parameters across these rest-frame diagrams are revealed after the dust correction and are fitted by the LOESS method to reduce uncertainty effects. Quiescent galaxy samples defined via classical $UVJ$ diagrams are typically contaminated by a $\sim20$% fraction of DSF galaxies. A significant part of the galaxies in the green valley are actually obscured star-forming galaxies ($\sim30-65$%). Consequently, the transition of galaxies from the blue cloud to the red sequence, and hence the related mechanisms for quenching, seems to be much more efficient and faster than previously reported. The rest-frame stellar mass$-$colour and $UVJ$ colour$-$colour diagrams are useful for constraining the age, metallicity, extinction, and star formation rate of quiescent galaxies by only their redshift, rest-frame colours, and/or stellar mass. Dust correction plays an important role in understanding how quiescent galaxies are distributed in these diagrams and is key to performing a pure selection of quiescent galaxies via intrinsic colours.Comment: (37 pages, 29 figures, accepted for publication in A&A