Galaxy And Mass Assembly (GAMA): growing up in a bad neighbourhood - how do low-mass galaxies become passive?

Both theoretical predictions and observations of the very nearby Universe suggest that low-mass galaxies (log$_{10}$[M$_{*}$/M$_{\odot}$]<9.5) are likely to remain star-forming unless they are affected by their local environment. To test this premise, we compare and contrast the local environment of both passive and star-forming galaxies as a function of stellar mass, using the Galaxy and Mass Assembly survey. We find that passive fractions are higher in both interacting pair and group galaxies than the field at all stellar masses, and that this effect is most apparent in the lowest mass galaxies. We also find that essentially all passive log$_{10}$[M$_{*}$/M$_{\odot}$]<8.5 galaxies are found in pair/group environments, suggesting that local interactions with a more massive neighbour cause them to cease forming new stars. We find that the effects of immediate environment (local galaxy-galaxy interactions) in forming passive systems increases with decreasing stellar mass, and highlight that this is potentially due to increasing interaction timescales giving sufficient time for the galaxy to become passive via starvation. We then present a simplistic model to test this premise, and show that given our speculative assumptions, it is consistent with our observed results.Comment: 20 pages, 12 figures, Accepted to MNRA

Ambiguity, multiple streams, and EU policy

The multiple streams framework draws insight from interactions between agency and institutions to explore the impact of context, time, and meaning on policy change and to assess the institutional and issue complexities permeating the European Union (EU) policy process. The authors specify the assumptions and structure of the framework and review studies that have adapted it to reflect more fully EU decision-making processes. The nature of policy entrepreneurship and policy windows are assessed to identify areas of improvement. Finally, the authors sketch out a research agenda that refines the logic of political manipulation which permeates the lens and the institutional complexity which frames the EU policy process

Galaxy And Mass Assembly (GAMA) : stellar mass functions by Hubble type

This work was supported by the Austrian Science Foundation FWF under grant P23946. AWG was supported under the Australian Research Council's funding scheme FT110100263.We present an estimate of the galaxy stellar mass function and its division by morphological type in the local (0.025 < z < 0.06) Universe. Adopting robust morphological classifications as previously presented (Kelvin et al.) for a sample of 3727 galaxies taken from the Galaxy And Mass Assembly survey, we define a local volume and stellar mass limited sub-sample of 2711 galaxies to a lower stellar mass limit of M = 109.0 MΘ. We confirm that the galaxy stellar mass function is well described by a double-Schechter function given by Μ* = 1010.64 MΘ, α1 = 0.43, φ1* = 4.18 dex-1 Mpc-3, α2 = −1.50 and φ2* = 0.74 dex-1 Mpc-3. The constituent morphological-type stellar mass functions are well sampled above our lower stellar mass limit, excepting the faint little blue spheroid population of galaxies. We find approximately 71-4+3 per cent of the stellar mass in the local Universe is found within spheroid-dominated galaxies; ellipticals and S0-Sas. The remaining 29-3+4 per cent falls predominantly within late-type disc-dominated systems, Sab-Scds and Sd-Irrs. Adopting reasonable bulge-to-total ratios implies that approximately half the stellar mass today resides in spheroidal structures, and half in disc structures. Within this local sample, we find approximate stellar mass proportions for E : S0-Sa : Sab-Scd : Sd-Irr of 34 : 37 : 24 :5.Publisher PDFPeer reviewe

Galaxy And Mass Assembly (GAMA) : The mechanisms for quiescent galaxy formation at z<1

© 2016 The Authors. One key problem in astrophysics is understanding how and why galaxies switch off their star formation, building the quiescent population that we observe in the local Universe. From the Galaxy And Mass Assembly and VIsible MultiObject Spectrograph Public Extragalactic Redshift surveys, we use spectroscopic indices to select quiescent and candidate transition galaxies.We identify potentially rapidly transitioning post-starburst (PSB) galaxies and slower transitioning green-valley galaxies. Over the last 8Gyr, the quiescent population has grown more slowly in number density at high masses (M * > 10 11 M ⊙ ) than at intermediate masses (M * > 10 10.6 M ⊙ ). There is evolution in both the PSB and green-valley stellar mass functions, consistent with higher mass galaxies quenching at earlier cosmic times.At intermediatemasses (M * > 10 10.6 M ⊙ ), we find a green-valley transition time-scale of 2.6 Gyr. Alternatively, at z ~ 0.7, the entire growth rate could be explained by fast-quenching PSB galaxies, with a visibility time-scale of 0.5 Gyr. At lower redshift, the number density of PSBs is so low that an unphysically short visibility window would be required for them to contribute significantly to the quiescent population growth. The importance of the fast-quenching route may rapidly diminish at z 10 11 M ⊙ ), there is tension between the large number of candidate transition galaxies compared to the slow growth of the quiescent population. This could be resolved if not all high-mass PSB and green-valley galaxies are transitioning from star forming to quiescent, for example if they rejuvenate out of the quiescent population following the accretion of gas and triggering of star formation, or if they fail to completely quench their star formation

Galaxy And Mass Assembly (GAMA) blended spectra catalogue: strong galaxy-galaxy lens and occulting galaxy pair candidates

We present the catalogue of blended galaxy spectra from the Galaxy And Mass Assembly (GAMA) survey. These are cases where light from two galaxies are significantly detected in a single GAMA fibre. Galaxy pairs identified from their blended spectrum fall into two principal classes: they are either strong lenses, a passive galaxy lensing an emission-line galaxy; or occulting galaxies, serendipitous overlaps of two galaxies, of any type. Blended spectra can thus be used to reliably identify strong lenses for follow-up observations (high-resolution imaging) and occulting pairs, especially those that are a late-type partly obscuring an early-type galaxy which are of interest for the study of dust content of spiral and irregular galaxies. The GAMA survey setup and its AUTOZ automated redshift determination were used to identify candidate blended galaxy spectra from the cross-correlation peaks. We identify 280 blended spectra with a minimum velocity separation of 600 km s−1, of which 104 are lens pair candidates, 71 emission-line-passive pairs, 78 are pairs of emission-line galaxies and 27 are pairs of galaxies with passive spectra. We have visually inspected the candidates in the Sloan Digital Sky Survey (SDSS) and Kilo Degree Survey (KiDS) images. Many blended objects are ellipticals with blue fuzz (Ef in our classification). These latter ‘Ef’ classifications are candidates for possible strong lenses, massive ellipticals with an emission-line galaxy in one or more lensed images. The GAMA lens and occulting galaxy candidate samples are similar in size to those identified in the entire SDSS. This blended spectrum sample stands as a testament of the power of this highly complete, second-largest spectroscopic survey in existence and offers the possibility to expand e.g. strong gravitational lens surveys

Galaxy And Mass Assembly (GAMA) : growing up in a bad neighbourhood - how do low-mass galaxies become passive?

Both theoretical predictions and observations of the very nearby Universe suggest that low-mass galaxies(log10[M*/M⊙] < 9.5) are likely to remain star-forming unless they are affected by their local environment. To test this premise, we compare and contrast the local environment of both passive and star-forming galaxies as a function of stellar mass, using the Galaxy and Mass Assembly survey. We find that passive fractions are higher in both interacting pair and group galaxies than the field at all stellar masses, and that this effect is most apparent in the lowest mass galaxies. We also find that essentially all passive log10[M*/M⊙] < 8.5 galaxies are found in pair/group environments, suggesting that local interactions with a more massive neighbour cause them to cease forming new stars. We find that the effects of immediate environment (local galaxy–galaxy interactions) in forming passive systems increase with decreasing stellar mass, and highlight that this is potentially due to increasing interaction time-scales giving sufficient time for the galaxy to become passive via starvation. We then present a simplistic model to test this premise, and show that given our speculative assumptions, it is consistent with our observed results.Publisher PDFPeer reviewe

Galaxy And Mass Assembly (GAMA) : the large-scale structure of galaxies and comparison to mock universes

MA acknowledges funding from the University of St Andrews and the International Centre for Radio Astronomy Research. ASGR is supported by funding from a UWA Fellowship. PN acknowledges the support of the Royal Society through the award of a University Research Fellowship and the European Research Council, through receipt of a Starting Grant (DEGAS-259586). MJIB acknowledges the financial support of the Australian Research Council Future Fellowship 100100280. TMR acknowledges support from a European Research Council Starting Grant (DEGAS-259586).From a volume-limited sample of 45 542 galaxies and 6000 groups with z ≤ 0.213, we use an adapted minimal spanning tree algorithm to identify and classify large-scale structures within the Galaxy And Mass Assembly (GAMA) survey. Using galaxy groups, we identify 643 filaments across the three equatorial GAMA fields that span up to 200 h−1 Mpc in length, each with an average of eight groups within them. By analysing galaxies not belonging to groups, we identify a secondary population of smaller coherent structures composed entirely of galaxies, dubbed ‘tendrils’ that appear to link filaments together, or penetrate into voids, generally measuring around 10 h−1 Mpc in length and containing on average six galaxies. Finally, we are also able to identify a population of isolated void galaxies. By running this algorithm on GAMA mock galaxy catalogues, we compare the characteristics of large-scale structure between observed and mock data, finding that mock filaments reproduce observed ones extremely well. This provides a probe of higher order distribution statistics not captured by the popularly used two-point correlation function.Peer reviewe

Galaxy And Mass Assembly (GAMA): curation and reanalysis of 16.6k redshifts in the G10/COSMOS region

We discuss the construction of the Galaxy And Mass Assembly (GAMA) 10h region (G10) using publicly available data in the Cosmic Evolution Survey region (COSMOS) in order to extend the GAMA survey to z ∼ 1 in a single deg2 field. In order to obtain the maximum number of high precision spectroscopic redshifts we re-reduce all archival zCOSMOS-bright data and use the GAMA automatic cross-correlation redshift fitting code autoz. We use all available redshift information (autoz, zCOSMOS-bright 10k, PRIMUS, VVDS, SDSS and photometric redshifts) to calculate robust best-fitting redshifts for all galaxies and visually inspect all 1D and 2D spectra to obtain 16 583 robust redshifts in the full COSMOS region. We then define the G10 region to be the central ∼1 deg2 of COSMOS, which has relatively high spectroscopic completeness, and encompasses the CHILES VLA region. We define a combined r < 23.0 mag and i < 22.0 mag G10 sample (selected to have the highest bijective overlap) with which to perform future analysis, containing 9861 sources with reliable high-precision VLT-VIMOS spectra. All tables, spectra and imaging are available at http://ict.icrar.org/cutout/G10

Galaxy And Mass Assembly (GAMA): the 0.013 < z < 0.1 cosmic spectral energy distribution from 0.1 m to 1 mm

We use the Galaxy And Mass Assembly survey (GAMA) I data set combined with GALEX, Sloan Digital Sky Survey (SDSS) and UKIRT Infrared Deep Sky Survey (UKIDSS) imaging to construct the low-redshift (z < 0.1) galaxy luminosity functions in FUV, NUV, ugriz and YJHK bands from within a single well-constrained volume of 3.4 × 105 (Mpc h−1)3. The derived luminosity distributions are normalized to the SDSS data release 7 (DR7) main survey to reduce the estimated cosmic variance to the 5 per cent level. The data are used to construct the cosmic spectral energy distribution (CSED) from 0.1 to 2.1 μm free from any wavelength-dependent cosmic variance for both the elliptical and non-elliptical populations. The two populations exhibit dramatically different CSEDs as expected for a predominantly old and young population, respectively. Using the Driver et al. prescription for the azimuthally averaged photon escape fraction, the non-ellipticals are corrected for the impact of dust attenuation and the combined CSED constructed. The final results show that the Universe is currently generating (1.8 ± 0.3) × 1035 h W Mpc−3 of which (1.2 ± 0.1) × 1035 h W Mpc−3 is directly released into the inter-galactic medium and (0.6 ± 0.1) × 1035 h W Mpc−3 is reprocessed and reradiated by dust in the far-IR. Using the GAMA data and our dust model we predict the mid- and far-IR emission which agrees remarkably well with available data. We therefore provide a robust description of the pre- and post-dust attenuated energy output of the nearby Universe from 0.1 μm to 0.6 mm. The largest uncertainty in this measurement lies in the mid- and far-IR bands stemming from the dust attenuation correction and its currently poorly constrained dependence on environment, stellar mass and morphology

MUSE spectroscopy and deep observations of a unique compact JWST target, lensing cluster CLIO

We present the results of a VLT MUSE/FORS2 and Spitzer survey of a unique compact lensing cluster CLIO at z = 0.42, discovered through the GAMA survey using spectroscopic redshifts. Compact and massive clusters such as this are understudied, but provide a unique prospective on dark matter distributions and for finding background lensed high-z galaxies. The CLIO cluster was identified for follow-up observations due to its almost unique combination of high-mass and dark matter halo concentration, as well as having observed lensing arcs from ground-based images. Using dual band optical and infra-red imaging from FORS2 and Spitzer, in combination with MUSE optical spectroscopy we identify 89 cluster members and find background sources out to z = 6.49. We describe the physical state of this cluster, finding a strong correlation between environment and galaxy spectral type. Under the assumption of an NFW profile, we measure the total mass of CLIO to be M200 = (4.49 ± 0.25) × 1014 M⊙. We build and present an initial strong-lensing model for this cluster, and measure a relatively low intracluster light (ICL) fraction of 7.21 ± 1.53 per cent through galaxy profile fitting. Due to its strong potential for lensing background galaxies and its low ICL, the CLIO cluster will be a target for our 110 h James Webb Space Telescope ‘Webb Medium-Deep Field’ (WMDF) GTO program.Publisher PDFPeer reviewe