The role of stellar radial motions in shaping galaxy surface brightness profiles

Aims. The physics driving features such as breaks observed in galaxy surface brightness (SB) profiles remains contentious. Here, we assess the importance of stellar radial motions in shaping their characteristics. Methods. We use the simulated Milky Way-mass cosmological discs from the Ramses Disc Environment Study (RaDES) to characterise the radial redistribution of stars in galaxies displaying type-I (pure exponentials), II (downbending), and III (upbending) SB profiles. We compare radial profiles of the mass fractions and the velocity dispersions of different sub-populations of stars according to their birth and current location. Results. Radial redistribution of stars is important in all galaxies regardless of their light profiles. Type-II breaks seem to be a consequence of the combined effects of outward-moving and accreted stars. The former produce shallower inner profiles (lack of stars in the inner disc) and accumulate material around the break radius and beyond, strengthening the break; the latter can weaken or even convert the break into a pure exponential. Further accretion from satellites can concentrate material in the outermost parts, leading to type-III breaks that can coexist with type-II breaks, but situated further out. Type-III galaxies would be the result of an important radial redistribution of material throughout the entire disc, as well as a concentration of accreted material in the outskirts. In addition, type-III galaxies display the most efficient radial redistribution and the largest number of accreted stars, followed by type-I and II systems, suggesting that type-I galaxies may be an intermediate case between types-II and III. In general, the velocity dispersion profiles of all galaxies tend to flatten or even increase around the locations where the breaks are found. The age and metallicity profiles are also affected, exhibiting different inner gradients depending on their SB profile, being steeper in the case of type-II systems (as found observationally). The steep type-II profiles might be inherent to their formation rather than acquired via radial redistribution

Dissecting galactic bulges in space and time I: The importance of early formation scenarios vs. secular evolution

This article has been accepted for publication in Monthly Notices Royal Astronomical Society ©: 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reservedThe details of bulge formation via collapse, mergers, secular processes or their interplay remain unresolved. To start answering this question and quantify the importance of distinct mechanisms, we mapped a sample of three galactic bulges using data from the integral field spectrograph WiFeS on the ANU's 2.3-m telescope in Siding Spring Observatory. Its highresolution gratings (R ~ 7000) allow us to present a detailed kinematic and stellar population analysis of their inner structures with classical and novel techniques. The comparison of those techniques calls for the necessity of inversion algorithms in order to understand complex substructures and separate populations. We use line-strength indices to derive single stellar population equivalent ages and metallicities. Additionally, we use full spectral fitting methods, here the code STECKMAP, to extract their star formation histories. The high quality of our data allows us to study the 2D distribution of different stellar populations (i.e. young, intermediate and old). We can identify their dominant populations based on these age-discriminated 2D light and mass contribution. In all galactic bulges studied, at least 50 per cent of the stellar mass already existed 12 Gyr ago, more than currently predicted by simulations. A younger component (age between ~1 and ~8 Gyr) is also prominent and its present day distribution seems to be affected much more strongly by morphological structures, especially bars, than the older one. This in-depth analysis of the three bulges supports the notion of increasing complexity in their evolution, likely to be found in numerous bulge structures if studied at this level of detail, which cannot be achieved by mergers alone and require a non-negligible contribution of secular evolutionMKS acknowledges the support of the Instituto de Astrofísica de Canarias via an Astrophysicist Resident fellowship and Ignacio Martín-Navarro, Andra Stroe and Stéphane Courteau for useful discussions. RC acknowledges the Ministerio de Ciencia e Innovación by means of their FPI program (grant AYA- 2010-21322-C03-03 and AYA-2013-48226-C3-3-P). JFB acknowledges support from the Ramón y Cajal Program and from the FP7 Marie Curie Actions of the European Commission, via the Initial Training Network DAGAL under REA grant agreement number 289313. TRL thanks the support of the Spanish Ministerio de Educación, Cultura y Deporte by means of the FPU fellowship. This research has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO; grants AYA2010-21322-C03-02 and AYA2009-11137) and by the Spanish Ministry of Science and Innovation (MICINN; grants AYA2011-24728 and Consolider-Ingenio CSD2010-00064) and by the Junta de Andalucía (FQM-108

Temporal changes of NDVI for qualitative environmental assessment of mangroves: Shrimp farming impact on the health decline of the arid mangroves in the Gulf of California (1990-2010)

We assessed the temporal evolution of vegetation activity of mangroves in the Southeastern coastal of the Gulf of California (Mexico) through a multi-temporal analysis of Landsat TM images from 1990 to 2010 where time series of the Normalized Difference Vegetation Index (NDVI) were obtained. A multivariate regression analysis showed the presence of statistically significant negative trends of NDVI (low vegetation activity) in the coverage of mangrove forest, mangrove forest with pickleweed, and pickleweed; however, we did not found any meteorological variable (built time series of average minimum and maximum temperatures, and of accumulated rainfall) that controlled the observed trends. A pixel-by-pixel spatially distributed analysis of the temporal trends of NDVI, complemented by digitalization through photo interpretation of the shrimp farms present in the study area, showed a spatial relationship between the zones of greatest loss of vegetation activity (1990–2010) and the areas with greater proliferation of shrimp farms in the study area. Our study demonstrated the applicability of NDVI for the environmental assessment of mangroves. The relationship between changes in remote sensing indices and environmental variables allows for an efficient evaluation of the main environmental impacts, which can be used for coastal planning and management.The research was supported by the Mexican Secretary of Natural Resources and Environment (SEMARNAT-CONACYT; grant number SEMARNAT-2002-C01-0147). SM-B and RJM are students of Academic Program of Geoinformatics (UACJ).Peer Reviewe

Galaxy and mass assembly (GAMA): The environmental impact on SFR and metallicity in galaxy groups

We present a study of the relationships and environmental dependencies between stellar mass, star formation rate, and gas metallicity for more than 700 galaxies in groups up to redshift 0.35 from the Galaxy And Mass Assembly (GAMA) survey. To identify the main drivers, our sample was analysed as a function of group-centric distance, projected galaxy number density, and stellar mass. By using control samples of more than 16 000 star-forming field galaxies and volume-limited samples, we find that the highest enhancement in SFR (0.3 dex) occurs in galaxies with the lowest local density. In contrast to previous work, our data show small enhancements of ∼0.1 dex in SFR for galaxies at the highest local densities or group-centric distances. Our data indicates quenching in SFR only for massive galaxies, suggesting that stellar mass might be the main driver of quenching processes for star forming galaxies. We can discard a morphological driven quenching, since the Sérsic index distribution for group and control galaxies are similar. The gas metallicity does not vary drastically. It increases ∼0.08 dex for galaxies at the highest local densities, and decreases for galaxies at the highest group-centric distances, in agreement with previous work. Altogether, the local density, rather than group-centric distance, shows the stronger impact in enhancing both, the SFR and gas metallicity. We applied the same methodology to galaxies from the IllustrisTNG simulations, and although we were able to reproduce the general observational trends, the differences between group and control samples only partially agree with the observations

Galaxy and mass assembly (GAMA): The environmental impact on SFR and metallicity in galaxy groups

We present a study of the relationships and environmental dependencies between stellar mass, star formation rate, and gas metallicity for more than 700 galaxies in groups up to redshift 0.35 from the Galaxy And Mass Assembly (GAMA) survey. To identify the main drivers, our sample was analysed as a function of group-centric distance, projected galaxy number density, and stellar mass. By using control samples of more than 16 000 star-forming field galaxies and volume-limited samples, we find that the highest enhancement in SFR (0.3 dex) occurs in galaxies with the lowest local density. In contrast to previous work, our data show small enhancements of ∼0.1 dex in SFR for galaxies at the highest local densities or group-centric distances. Our data indicates quenching in SFR only for massive galaxies, suggesting that stellar mass might be the main driver of quenching processes for star forming galaxies. We can discard a morphological driven quenching, since the Sérsic index distribution for group and control galaxies are similar. The gas metallicity does not vary drastically. It increases ∼0.08 dex for galaxies at the highest local densities, and decreases for galaxies at the highest group-centric distances, in agreement with previous work. Altogether, the local density, rather than group-centric distance, shows the stronger impact in enhancing both, the SFR and gas metallicity. We applied the same methodology to galaxies from the IllustrisTNG simulations, and although we were able to reproduce the general observational trends, the differences between group and control samples only partially agree with the observations

CO-CAVITY pilot survey:Molecular gas and star formation in void galaxies

We present the first molecular gas mass survey of void galaxies. We compare these new data together with data for the atomic gas mass and star formation rate ($\rm SFR$) from the literature to those of galaxies in filaments and walls in order to better understand how molecular gas and star formation are related to the large-scale environment. We observed at the IRAM 30 m telescope the CO(1-0) and CO(2-1) emission of 20 void galaxies selected from the Void Galaxy Survey (VGS), with a stellar mass range from $\rm 10^{8.5}$ to $\rm 10^{10.3}M_{\odot}$. We detected 15 objects in at least one CO line. We compared the molecular gas mass ($M_{\rm H_2}$), the star formation efficiency ($\rm SFE =SFR/M_{\rm H_2}$), the atomic gas mass, the molecular-to-atomic gas mass ratio, and the specific star formation rate (sSFR) of the void galaxies with two control samples of galaxies in filaments and walls, selected from xCOLD GASS and EDGE-CALIFA, for different stellar mass bins and taking the star formation activity into account. The results for the molecular gas mass for a sample of 20 voids galaxies allowed us to make a statistical comparison to galaxies in filaments and walls for the first time.Comment: 24 pages, 15 figures, accepted in A&A, language corrected versio

Gut-Brain Axis: Role of Microbiota in Parkinson’s Disease and Multiple Sclerosis

It has recently been discovered that the digestive tract is lined with about 100 million nerve cells; the digestive tract has been baptized, metaphorically speaking, as “the second brain,” which contains a multitude of neurotransmitters, viruses, and bacteria that help regulate our emotional state. This second brain, known as the enteric nervous system, is a unique anatomical unit that extends from the esophagus to the anus. Like the nervous system, it produces a whole series of psychoactive substances, such as serotonin, dopamine, and opioids for pain, and synthesizes benzodiazepines. In it, we find the microbiota: a set of microorganisms (viruses and bacteria). Together with the brain, the microbiota directly influences mood, character, or sleep. Knowledge about the possible relationship of the microbiota with frequent neurological diseases is still just beginning. Recently, possible changes in the microbiota have been linked to the onset of Parkinson’s disease (PD). Also, today, we know that there are differences between the microbiota of healthy people and people with multiple sclerosis and that these differences have also been related to the disease and its evolution