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- Galaxies: evolution (59)
- Galaxies: structure (58)
- Galaxies: spiral (54)
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- Galaxies: stellar content (25)
- Galaxies: photometry (22)
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- Galaxies: groups: general (8)
- Extinction (7)
- Galaxies (7)
- ISM: structure (7)
- Large-scale structure of Universe (7)
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Articles 61 - 90 of 207
Full-Text Articles in Physical Sciences and Mathematics
Galaxy And Mass Assembly (Gama): Defining Passive Galaxy Samples And Searching For The Uv Upturn, S. Phillipps, S. S. Ali, M. N. Bremer, R. De Propris, A. E. Sansom, M. E. Cluver, M. Alpaslan, S. Brough, M. J.I. Brown, L. J.M. Davies, S. P. Driver, M. W. Grootes, Benne W. Holwerda, A. M. Hopkins, P. A. James, K. Pimbblet, A. S.G. Robotham, E. N. Taylor, L. Wang
Galaxy And Mass Assembly (Gama): Defining Passive Galaxy Samples And Searching For The Uv Upturn, S. Phillipps, S. S. Ali, M. N. Bremer, R. De Propris, A. E. Sansom, M. E. Cluver, M. Alpaslan, S. Brough, M. J.I. Brown, L. J.M. Davies, S. P. Driver, M. W. Grootes, Benne W. Holwerda, A. M. Hopkins, P. A. James, K. Pimbblet, A. S.G. Robotham, E. N. Taylor, L. Wang
Faculty Scholarship
We use data from the GAMA and GALEX surveys to demonstrate that the UV upturn, an unexpected excess of ultraviolet flux from a hot stellar component, seen in the spectra of many early-type galaxies, arises from processes internal to individual galaxies with no measurable influence from the galaxies' larger environment. We first define a clean sample of passive galaxies without a significant contribution to their UV flux from low-level star formation. We confirm that galaxies with the optical colours of red sequence galaxies often have signs of residual star formation, which, without other information, would prevent a convincing demonstration of …
Galaxy And Mass Assembly (Gama): Properties And Evolution Of Red Spiral Galaxies, Smriti Mahajan, Kriti Kamal Gupta, Rahul Rana, M. J.I. Brown, S. Phillipps, Joss Bland-Hawthorn, M. N. Bremer, S. Brough, Benne W. Holwerda, A. M. Hopkins, J. Loveday, Kevin Pimbblet, Lingyu Wang
Galaxy And Mass Assembly (Gama): Properties And Evolution Of Red Spiral Galaxies, Smriti Mahajan, Kriti Kamal Gupta, Rahul Rana, M. J.I. Brown, S. Phillipps, Joss Bland-Hawthorn, M. N. Bremer, S. Brough, Benne W. Holwerda, A. M. Hopkins, J. Loveday, Kevin Pimbblet, Lingyu Wang
Faculty Scholarship
We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002 < z < 0.06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environment-related mechanism(s) that has removed dust and gas, leading to a lower star formation rate. We conclude that this process acts on long time-scales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The specific star formation rate (sSFR) and dust-to-stellar mass ratio of red spiral galaxies is found to be statistically lower than blue spiral galaxies. On the other hand, red spirals are on average 0.9 dex more massive, and reside in environments 2.6 times denser than their blue counterparts. We find no evidence of excessive nuclear activity, or higher inclination angles to support these as the major causes for the red optical colours seen in ≳47 per cent of all spirals in our sample. Furthermore, for a small subsample of our spiral galaxies that are detected in H I, we find that the SFR of gas-rich red spiral galaxies is lower by ∼1 dex than their blue counterparts.
Default Parallels: The Science Potential Of Jwst Parallel Observations During Tso Primary Observations, Benne W. Holwerda, Jonathan Fraine, Nelly Mouawad, Joanna S. Bridge
Default Parallels: The Science Potential Of Jwst Parallel Observations During Tso Primary Observations, Benne W. Holwerda, Jonathan Fraine, Nelly Mouawad, Joanna S. Bridge
Faculty Scholarship
The James Webb Space Telescope (JWST) will observe several stars for long cumulative durations while pursuing exoplanets as primary science targets for both Guaranteed Time Observations (GTO) and very likely General Observer (GO) programs. Here we argue in favor of an automatic default parallel program to observe, e.g., using the F200W/F277W filters or grism of NIRCAM/NIRISS in order to find high redshift (z (Formula Presented) 10) galaxies, cool red/brown dwarf substellar objects, solar system objects, and observations of serendipitous planetary transits. We argue here the need for automated exploratory astrophysical observations with unused JWST instruments during these long-duration exoplanet observations. …
Effect Of Galaxy Mergers On Star-Formation Rates, W. J. Pearson, L. Wang, M. Alpaslan, I. Baldry, M. Bilicki, M. J.I. Brown, M. W. Grootes, Benne W. Holwerda, T. D. Kitching, S. Kruk, F. F.S. Van Der Tak
Effect Of Galaxy Mergers On Star-Formation Rates, W. J. Pearson, L. Wang, M. Alpaslan, I. Baldry, M. Bilicki, M. J.I. Brown, M. W. Grootes, Benne W. Holwerda, T. D. Kitching, S. Kruk, F. F.S. Van Der Tak
Faculty Scholarship
Context. Galaxy mergers and interactions are an integral part of our basic understanding of how galaxies grow and evolve over time. However, the effect that galaxy mergers have on star-formation rates (SFRs) is contested, with observations of galaxy mergers showing reduced, enhanced, and highly enhanced star formation. Aims. We aim to determine the effect of galaxy mergers on the SFR of galaxies using statistically large samples of galaxies, totalling over 200 000, which is over a large redshift range from 0.0 to 4.0. Methods. We trained and used convolutional neural networks to create binary merger identifications (merger or non-merger) in …
Star-Forming, Rotating Spheroidal Galaxies In The Gama And Sami Surveys, Amanda J. Moffett, Steven Phillipps, Aaron S.G. Robotham, Simon P. Driver, Malcolm N. Bremer, Luca Cortese, O. Ivy Wong, Sarah Brough, Michael J.I. Brown, Julia J. Bryant, Christopher J. Conselice, Scott M. Croom, Koshy George, Greg Goldstein, Michael Goodwin, Benne W. Holwerda, Andrew M. Hopkins, Iraklis S. Konstantopoulos, Jon S. Lawrence, Nuria P.F. Lorente, Anne M. Medling, Matt S. Owers, Kevin A. Pimbblet, Samuel N. Richards, Sarah M. Sweet, Jesse Van De Sande
Star-Forming, Rotating Spheroidal Galaxies In The Gama And Sami Surveys, Amanda J. Moffett, Steven Phillipps, Aaron S.G. Robotham, Simon P. Driver, Malcolm N. Bremer, Luca Cortese, O. Ivy Wong, Sarah Brough, Michael J.I. Brown, Julia J. Bryant, Christopher J. Conselice, Scott M. Croom, Koshy George, Greg Goldstein, Michael Goodwin, Benne W. Holwerda, Andrew M. Hopkins, Iraklis S. Konstantopoulos, Jon S. Lawrence, Nuria P.F. Lorente, Anne M. Medling, Matt S. Owers, Kevin A. Pimbblet, Samuel N. Richards, Sarah M. Sweet, Jesse Van De Sande
Faculty Scholarship
The Galaxy And Mass Assembly (GAMA) survey has morphologically identified a class of 'Little Blue Spheroid' (LBS) galaxies whose relationship to other classes of galaxies we now examine in detail. Considering a sample of 868 LBSs, we find that such galaxies display similar but not identical colours, specific star formation rates, stellar population ages, massto- light ratios, and metallicities to Sd-Irr galaxies. We also find that LBSs typically occupy environments of even lower density than those of Sd-Irr galaxies, where ∼65 per cent of LBS galaxies live in isolation. Using deep, high-resolution imaging from VST KiDS and the new Bayesian, …
The Super Eight Galaxies: Properties Of A Sample Of Very Bright Galaxies At 7 < Z < 8, Joanna S. Bridge, Benne W. Holwerda, Mauro Stefanon, Rychard J. Bouwens, Pascal A. Oesch, Michele Trenti, Stephanie R. Bernard, Larry D. Bradley, Garth D. Illingworth, Samir Kusmic, Dan Magee, Takahiro Morishita, Guido W. Roberts-Borsani, Renske Smit, Rebecca L. Steele
The Super Eight Galaxies: Properties Of A Sample Of Very Bright Galaxies At 7 < Z < 8, Joanna S. Bridge, Benne W. Holwerda, Mauro Stefanon, Rychard J. Bouwens, Pascal A. Oesch, Michele Trenti, Stephanie R. Bernard, Larry D. Bradley, Garth D. Illingworth, Samir Kusmic, Dan Magee, Takahiro Morishita, Guido W. Roberts-Borsani, Renske Smit, Rebecca L. Steele
Faculty Scholarship
We present the Super Eight galaxies - a set of very luminous, high-redshift (7.1 < z < 8.0) galaxy candidates found in the Brightest of Reionizing Galaxies (BoRG) Survey fields. The original sample includes eight galaxies that are Y-band dropout objects with H-band magnitudes of m H < 25.5. Four of these objects were originally reported in Calvi et al. Combining new Hubble Space Telescope (HST) WFC3/F814W imaging and Spitzer IRAC data with archival imaging from BoRG and other surveys, we explore the properties of these galaxies. Photometric redshift fitting places six of these galaxies in the redshift range of 7.1 < z < 8.0, resulting in three new high-redshift galaxies and confirming three of the four high-redshift galaxy candidates from Calvi et al. We calculate the half-light radii of the Super Eight galaxies using the HST F160W filter and find that the Super Eight sizes are in line with the typical evolution of size with redshift. The Super Eights have a mean mass of log (M ∗/M o) ∼10, which is typical for sources in this luminosity range. Finally, we place our sample on the UV z ∼ 8 luminosity function and find that the Super Eight number density is consistent with other surveys in this magnitude and redshift range.
Galaxy Classification: A Machine Learning Analysis Of Gama Catalogue Data, Aleke Nolte, Lingyu Wang, Maciej Bilicki, Benne W. Holwerda, Michael Biehl
Galaxy Classification: A Machine Learning Analysis Of Gama Catalogue Data, Aleke Nolte, Lingyu Wang, Maciej Bilicki, Benne W. Holwerda, Michael Biehl
Faculty Scholarship
We present a machine learning analysis of five labelled galaxy catalogues from the Galaxy And Mass Assembly (GAMA): The SersicCatVIKING and SersicCatUKIDSS catalogues containing morphological features, the GaussFitSimplecatalogue containing spectroscopic features, the MagPhys catalogue including physical parameters for galaxies, and the Lambdar catalogue, which contains photometric measurements. Extending work previously presented at the ESANN 2018 conference – in an analysis based on Generalized Relevance Matrix Learning Vector Quantization and Random Forests – we find that neither the data from the individual catalogues nor a combined dataset based on all 5 catalogues fully supports the visual-inspection-based galaxy classification scheme employed to …
Morphometric Analysis And Application In Galaxy Evolution And High-Redshift Surveys., Samir Kusmic
Morphometric Analysis And Application In Galaxy Evolution And High-Redshift Surveys., Samir Kusmic
College of Arts & Sciences Senior Honors Theses
In this thesis, I will present my research work with statistical analysis towards a galaxy’s morphology and its morphometric. The first part would be with the galaxy morphometric and have heavy focus with one particular software: Source Extractor. Source Extractor was compared to GALFIT in order to see how accurate and precise we would expect the software to be with effective radii, scale length, inclination,position angle, and major and minor axes. This is towards preparation for future surveys with expectation of a large boom in galaxy discovery with the new observatories to be online (EUCLID, LSST, JWST, etc.). From our …
Galaxy And Mass Assembly (Gama): Time-Scales For Galaxies Crossing The Green Valley, S. Phillipps, M. N. Bremer, A. M. Hopkins, R. De Propris, E. N. Taylor, P. A. James, L. J.M. Davies, M. E. Cluver, S. P. Driver, S. A. Eales, Benne W. Holwerda, L. S. Kelvin, A. E. Sansom
Galaxy And Mass Assembly (Gama): Time-Scales For Galaxies Crossing The Green Valley, S. Phillipps, M. N. Bremer, A. M. Hopkins, R. De Propris, E. N. Taylor, P. A. James, L. J.M. Davies, M. E. Cluver, S. P. Driver, S. A. Eales, Benne W. Holwerda, L. S. Kelvin, A. E. Sansom
Faculty Scholarship
We explore the constraints that can be placed on the evolutionary time-scales for typical low-redshift galaxies evolving from the blue cloud through the green valley and on to the red sequence. We utilize galaxies from the GAMA survey with 0.1 < z < 0.2 and classify them according to the intrinsic (u∗ - r∗) colours of their stellar populations, as determined by fits to their multiwavelength spectral energy distributions. Using these fits to also determine stellar population ages and star formation time-scales, we argue that our results are consistent with a green valley population dominated by galaxies that are simply decreasing their star formation (running out of gas) over a time-scale of 2-4 Gyr which are seen at a specific epoch in their evolution (approximately 1.6 e-folding times after their peak in star formation). If their fitted star formation histories are extrapolated forward, the green galaxies will further redden over time, until they attain the colours of a passive population. In this picture, no specific quenching event which cuts-off their star formation is required, though it remains possible that the decline in star formation in green galaxies may be expedited by internal or external forces. However, there is no evidence that green galaxies have recently changed their star formation time-scales relative to their previous longer term star formation histories.
Galaxy And Mass Assembly (Gama): Environmental Quenching Of Centrals And Satellites In Groups, L. J.M. Davies, A. S.G. Robotham, C. Del P. Lagos, S. P. Driver, A. R.H. Stevens, Y. M. Bahé, M. Alpaslan, M. N. Bremer, M. J.I. Brown, S. Brough, J. Bland-Hawthorn, L. Cortese, P. Elahi, M. W. Grootes, Benne W. Holwerda, A. D. Ludlow, S. Mcgee, M. Owers, S. Phillipps
Galaxy And Mass Assembly (Gama): Environmental Quenching Of Centrals And Satellites In Groups, L. J.M. Davies, A. S.G. Robotham, C. Del P. Lagos, S. P. Driver, A. R.H. Stevens, Y. M. Bahé, M. Alpaslan, M. N. Bremer, M. J.I. Brown, S. Brough, J. Bland-Hawthorn, L. Cortese, P. Elahi, M. W. Grootes, Benne W. Holwerda, A. D. Ludlow, S. Mcgee, M. Owers, S. Phillipps
Faculty Scholarship
Recently a number of studies have found a similarity between the passive fraction of central and satellite galaxies when controlled for both stellar and halo mass. These results suggest that the quenching processes that affect galaxies are largely agnostic to central/satellite status, which contradicts the traditional picture of increased satellite quenching via environmental processes such as stripping, strangulation, and starvation. Here we explore this further using the Galaxy And Mass Assembly (GAMA) survey, which extends to ~2 dex lower in stellar mass than SDSS, is more complete for closely separated galaxies (≳395 per cent compared to ≳370 per cent), and …
The Dependence Of Intrinsic Alignment Of Galaxies On Wavelength Using Kids And Gama, Christos Georgiou, Harry Johnston, Henk Hoekstra, Massimo Viola, Konrad Kuijken, Benjamin Joachimi, Nora Elisa Chisari, Daniel J. Farrow, Hendrik Hildebrandt, Benne W. Holwerda, Arun Kannawadi
The Dependence Of Intrinsic Alignment Of Galaxies On Wavelength Using Kids And Gama, Christos Georgiou, Harry Johnston, Henk Hoekstra, Massimo Viola, Konrad Kuijken, Benjamin Joachimi, Nora Elisa Chisari, Daniel J. Farrow, Hendrik Hildebrandt, Benne W. Holwerda, Arun Kannawadi
Faculty Scholarship
The outer regions of galaxies are more susceptible to the tidal interactions that lead to intrinsic alignments of galaxies. The resulting alignment signal may therefore depend on the passband if the colours of galaxies vary spatially. To quantify this, we measured the shapes of galaxies with spectroscopic redshifts from the GAMA survey using deep gri imaging data from the KiloDegree Survey. The performance of the moment-based shape measurement algorithm DEIMOS was assessed using dedicated image simulations, which showed that the ellipticities could be determined with an accuracy better than 1% in all bands. Additional tests for potential systematic errors did …
Reproducible K-Means Clustering In Galaxy Feature Data From The Gama Survey, Sebastian Turner, Lee S. Kelvin, Ivan K. Baldry, Paulo J. Lisboa, Steven N. Longmore, Chris A. Collins, Benne W. Holwerda, Andrew M. Hopkins, Jochen Liske
Reproducible K-Means Clustering In Galaxy Feature Data From The Gama Survey, Sebastian Turner, Lee S. Kelvin, Ivan K. Baldry, Paulo J. Lisboa, Steven N. Longmore, Chris A. Collins, Benne W. Holwerda, Andrew M. Hopkins, Jochen Liske
Faculty Scholarship
A fundamental bimodality of galaxies in the local Universe is apparent in many of the features used to describe them. Multiple sub-populations exist within this framework, each representing galaxies following distinct evolutionary pathways. Accurately identifying and characterizing these sub-populations requires that a large number of galaxy features be analysed simultaneously. Future galaxy surveys such as LSST and Euclid will yield data volumes for which traditional approaches to galaxy classification will become unfeasible. To address this, we apply a robust k-means unsupervized clustering method to feature data derived from a sample of 7338 local-Universe galaxies selected from the Galaxy And Mass …
The Frequency Of Dust Lanes In Edge-On Spiral Galaxies Identified By Galaxy Zoo In Kids Imaging Of Gama Targets, Benne W. Holwerda, Lee Kelvin, Ivan Baldry, Chris Lintott, Mehmet Alpaslan, Kevin A. Pimbblet, Jochen Liske, Thomas Kitching, Steven Bamford, Jelte De Jong, Maciej Bilicki, Andrew Hopkins, Joanna Bridge, R. Steele, A. Jacques, S. Goswami, S. Kusmic, W. Roemer, S. Kruk, C. C. Popescu, K. Kuijken, L. Wang, A. Wright
The Frequency Of Dust Lanes In Edge-On Spiral Galaxies Identified By Galaxy Zoo In Kids Imaging Of Gama Targets, Benne W. Holwerda, Lee Kelvin, Ivan Baldry, Chris Lintott, Mehmet Alpaslan, Kevin A. Pimbblet, Jochen Liske, Thomas Kitching, Steven Bamford, Jelte De Jong, Maciej Bilicki, Andrew Hopkins, Joanna Bridge, R. Steele, A. Jacques, S. Goswami, S. Kusmic, W. Roemer, S. Kruk, C. C. Popescu, K. Kuijken, L. Wang, A. Wright
Faculty Scholarship
Dust lanes bisect the plane of a typical edge-on spiral galaxy as a dark optical absorption feature. Their appearance is linked to the gravitational stability of spiral disks; the fraction of edge-on galaxies that displays a dust lane is a direct indicator of the typical vertical balance between gravity and turbulence: a balance struck between the energy input from star formation and the gravitational pull into the plane of the disk. Based on morphological classifications by the Galaxy Zoo project on the Kilo Degree Survey (KiDS) imaging data in the Galaxy and Mass Assembly (GAMA) fields, we explore the relation …
Askap Commissioning Observations Of The Gama 23 Field, Denis A. Leahy, A. M. Hopkins, R. P. Norris, J. Marvil, J. D. Collier, E. N. Taylor, J. R. Allison, C. Anderson, M. Bell, M. Bilicki, J. Bland-Hawthorn, S. Brough, M. J.I. Brown, S. Driver, G. Gurkan, L. Harvey-Smith, I. Heywood, Benne W. Holwerda, J. Liske, A. R. Lopez-Sanchez, D. Mcconnell, A. Moffett, M. S. Owers, K. A. Pimbblet, W. Raja, N. Seymour, M. A. Voronkov, L. Wang
Askap Commissioning Observations Of The Gama 23 Field, Denis A. Leahy, A. M. Hopkins, R. P. Norris, J. Marvil, J. D. Collier, E. N. Taylor, J. R. Allison, C. Anderson, M. Bell, M. Bilicki, J. Bland-Hawthorn, S. Brough, M. J.I. Brown, S. Driver, G. Gurkan, L. Harvey-Smith, I. Heywood, Benne W. Holwerda, J. Liske, A. R. Lopez-Sanchez, D. Mcconnell, A. Moffett, M. S. Owers, K. A. Pimbblet, W. Raja, N. Seymour, M. A. Voronkov, L. Wang
Faculty Scholarship
We have observed the G23 field of the Galaxy AnMass Assembly (GAMA) survey using the Australian Square Kilometre Array Pathfinder (ASKAP) in its commissioning phase to validate the performance of the telescope and to characterise the detected galaxy populations. This observation covers ∼48 deg2 with synthesised beam of 32.7 arcsec by 17.8 arcsec at 936MHz, and ∼39 deg2 with synthesised beam of 15.8 arcsec by 12.0 arcsec at 1320MHz. At both frequencies, the root-mean-square (r.m.s.) noise is ∼0.1 mJy/beam. We combine these radio observations with the GAMA galaxy data, which includes spectroscopy of galaxies that are i-band selected with a …
Studying Galaxy Troughs And Ridges Using Weak Gravitational Lensing With The Kilo-Degree Survey, Margot M. Brouwer, Vasiliy Demchenko, Joachim Harnois-Déraps, Maciej Bilicki, Catherine Heymans, Henk Hoekstra, Konrad Kuijken, Mehmet Alpaslan, Sarah Brough, Yan Chuan Cai, Marcus V. Costa-Duarte, Andrej Dvornik, Thomas Erben, Hendrik Hildebrandt, Benne W. Holwerda, Peter Schneider, Cristóbal Sifón, Edo Van Uitert
Studying Galaxy Troughs And Ridges Using Weak Gravitational Lensing With The Kilo-Degree Survey, Margot M. Brouwer, Vasiliy Demchenko, Joachim Harnois-Déraps, Maciej Bilicki, Catherine Heymans, Henk Hoekstra, Konrad Kuijken, Mehmet Alpaslan, Sarah Brough, Yan Chuan Cai, Marcus V. Costa-Duarte, Andrej Dvornik, Thomas Erben, Hendrik Hildebrandt, Benne W. Holwerda, Peter Schneider, Cristóbal Sifón, Edo Van Uitert
Faculty Scholarship
We study projected underdensities in the cosmic galaxy density field known as 'troughs', and their overdense counterparts, which we call 'ridges'. We identify these regions using a bright sample of foreground galaxies from the photometric Kilo-Degree Survey (KiDS), specifically selected to mimic the spectroscopic Galaxy And Mass Assembly survey. Using background galaxies from KiDS, we measure the weak gravitational lensing profiles of the troughs/ridges. We quantify the amplitude of their lensing strength A as a function of galaxy density percentile rank P and galaxy overdensity δ, and find that the skewness in the galaxy density distribution is reflected in the …
Substellar And Low-Mass Dwarf Identification With Near-Infrared Imaging Space Observatories, Benne W. Holwerda, J. S. Bridge, R. Ryan, M. A. Kenworthy, N. Pirzkal, M. Andersen, S. Wilkins, R. Smit, S. R. Bernard, T. Meshkat, R. Steele, R. C. Bouwens
Substellar And Low-Mass Dwarf Identification With Near-Infrared Imaging Space Observatories, Benne W. Holwerda, J. S. Bridge, R. Ryan, M. A. Kenworthy, N. Pirzkal, M. Andersen, S. Wilkins, R. Smit, S. R. Bernard, T. Meshkat, R. Steele, R. C. Bouwens
Faculty Scholarship
Aims. We aim to evaluate the near-infrared colors of brown dwarfs as observed with four major infrared imaging space observatories: the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), the Euclid mission, and the WFIRST telescope. Methods. We used the SPLAT SPEX/ISPEX spectroscopic library to map out the colors of the M-, L-, and T-type dwarfs. We have identified which color-color combination is optimal for identifying broad type and which single color is optimal to then identify the subtype (e.g., T0-9). We evaluated each observatory separately as well as the narrow-field (HST and JWST) and wide-field (Euclid and …
The Causes Of The Red Sequence, The Blue Cloud, The Green Valley, And The Green Mountain, Stephen A. Eales, Maarten Baes, Nathan Bourne, Malcolm Bremer, Michael J.I. Brown, Christopher Clark, David Clements, Pieter De Vis, Simon Driver, Loretta Dunne, Simon Dye, Cristina Furlanetto, Benne W. Holwerda, R. J. Ivison, L. S. Kelvin, Maritza Lara-Lopez, Lerothodi Leeuw, Jon Loveday, Steve Maddox, Michal J. Michalowski, Steven Phillipps, Aaron Robotham, Dan Smith, Matthew Smith, Elisabetta Valiante, Paul Van Der Werf, Angus Wright
The Causes Of The Red Sequence, The Blue Cloud, The Green Valley, And The Green Mountain, Stephen A. Eales, Maarten Baes, Nathan Bourne, Malcolm Bremer, Michael J.I. Brown, Christopher Clark, David Clements, Pieter De Vis, Simon Driver, Loretta Dunne, Simon Dye, Cristina Furlanetto, Benne W. Holwerda, R. J. Ivison, L. S. Kelvin, Maritza Lara-Lopez, Lerothodi Leeuw, Jon Loveday, Steve Maddox, Michal J. Michalowski, Steven Phillipps, Aaron Robotham, Dan Smith, Matthew Smith, Elisabetta Valiante, Paul Van Der Werf, Angus Wright
Faculty Scholarship
The galaxies found in optical surveys fall in two distinct regions of a diagram of optical colour versus absolute magnitude: the red sequence and the blue cloud, with the green valley in between. We show that the galaxies found in a submillimetre survey have almost the opposite distribution in this diagram, forming a 'green mountain'. We show that these distinctive distributions follow naturally from a single, continuous, curved Galaxy Sequence in a diagram of specific star formation rate versus stellar mass, without there being the need for a separate star-forming galaxy main sequence and region of passive galaxies. The cause …
The Bright-End Galaxy Candidates At Z ∼ 9 From 79 Independent Hst Fields, T. Morishita, M. Trenti, M. Stiavelli, L. D. Bradley, D. Coe, P. A. Oesch, C. A. Mason, J. S. Bridge, Benne W. Holwerda, R. C. Livermore, B. Salmon, K. B. Schmidt, J. M. Shull, T. Treu
The Bright-End Galaxy Candidates At Z ∼ 9 From 79 Independent Hst Fields, T. Morishita, M. Trenti, M. Stiavelli, L. D. Bradley, D. Coe, P. A. Oesch, C. A. Mason, J. S. Bridge, Benne W. Holwerda, R. C. Livermore, B. Salmon, K. B. Schmidt, J. M. Shull, T. Treu
Faculty Scholarship
We present a full data analysis of the pure-parallel Hubble Space Telescope (HST) imaging observations in the Brightest of Reionizing Galaxies Survey (BoRG[z9]) in Cycle 22. The medium-deep exposures with five HST/WFC3IR+UVIS filter bands from 79 independent sightlines (∼370 arcmin2) provide the least biased determination of number density for z 9 bright galaxies against cosmic variance. After a strict two-step selection for candidate galaxies, including dropout color and photometric redshift analyses, and revision of previous BoRG candidates, we identify one source at z ∼ 10 and two sources at z ∼ 9. The z ∼ 10 candidate shows evidence of …
Galaxy And Mass Assembly (Gama): Accurate Number Densities And Environments Of Massive Ultra-Compact Galaxies At 0.02 < Z < 0.3, F. Buitrago, I. Ferreras, L. S. Kelvin, I. K. Baldry, L. Davies, J. Angthopo, S. Khochfar, A. M. Hopkins, S. P. Driver, S. Brough, J. Sabater, C. J. Conselice, J. Liske, Benne W. Holwerda, M. N. Bremer, S. Phillipps, A. R. López-Sánchez, A. W. Graham
Galaxy And Mass Assembly (Gama): Accurate Number Densities And Environments Of Massive Ultra-Compact Galaxies At 0.02 < Z < 0.3, F. Buitrago, I. Ferreras, L. S. Kelvin, I. K. Baldry, L. Davies, J. Angthopo, S. Khochfar, A. M. Hopkins, S. P. Driver, S. Brough, J. Sabater, C. J. Conselice, J. Liske, Benne W. Holwerda, M. N. Bremer, S. Phillipps, A. R. López-Sánchez, A. W. Graham
Faculty Scholarship
Context. Massive ultra-compact galaxies (MUGs) are common at z = 2-3, but very rare in the nearby Universe. Simulations predict that the few surviving MUGs should reside in galaxy clusters, whose large relative velocities prevent them from merging, thus maintaining their original properties (namely stellar populations, masses, sizes and dynamical state). Aims. Our goal is to obtain a complete census of the MUG population at 0.02 < z < 0.3, determining the number density, population properties and environment. Methods. We have taken advantage of the high-completeness, large-area spectroscopic GAMA survey, complementing it with deeper imaging from the KiDS and VIKING surveys. We find a set of 22 bona-fide MUGs, defined as having high stellar mass (> 8 × 1010 M™) and compact size (Re < 2 kpc). An additional set of seven lower-mass objects (6 × 1010 < Ma/M™ < 8 × 1010) are also potential candidates according to typical mass uncertainties. Results. The comoving number density of MUGs at low redshift (z < 0.3) is constrained at (1.0 ± 0.4)×10-6 Mpc-3, consistent with galaxy evolution models. However, we find a mixed distribution of old and young galaxies, with a quarter of the sample representing (old) relics. MUGs have a predominantly early or swollen disk morphology (Sérsic index 1 < n < 2.5) with high stellar surface densities (â Σea ∼1010 M™ Kpc-2). Interestingly, a large fraction feature close companions- A t least in projection-suggesting that many (but not all) reside in the central regions of groups. Halo masses show these galaxies inhabit average-mass groups. Conclusions. As MUGs are found to be almost equally distributed among environments of different masses, their relative fraction is higher in more massive overdensities, matching the expectations that some of these galaxies fell in these regions at early times. However, there must be another channel leading some of these galaxies to an abnormally low merger history because our sample shows a number of objects that do not inhabit particularly dense environments.
Deep Extragalactic Visible Legacy Survey (Devils): Motivation, Design, And Target Catalogue, L. J.M. Davies, A. S.G. Robotham, S. P. Driver, C. P. Lagos, L. Cortese, E. Mannering, C. Foster, C. Lidman, A. Hashemizadeh, S. Koushan, S. O'Toole, I. K. Baldry, M. Bilicki, J. Bland-Hawthorn, M. N. Bremer, M. J.I. Brown, J. J. Bryant, B. Catinella, S. M. Croom, M. W. Grootes, Benne W. Holwerda, M. J. Jarvis, N. Maddox, M. Meyer, A. J. Moffett, S. Phillipps, E. N. Taylor, R. A. Windhorst, C. Wolf
Deep Extragalactic Visible Legacy Survey (Devils): Motivation, Design, And Target Catalogue, L. J.M. Davies, A. S.G. Robotham, S. P. Driver, C. P. Lagos, L. Cortese, E. Mannering, C. Foster, C. Lidman, A. Hashemizadeh, S. Koushan, S. O'Toole, I. K. Baldry, M. Bilicki, J. Bland-Hawthorn, M. N. Bremer, M. J.I. Brown, J. J. Bryant, B. Catinella, S. M. Croom, M. W. Grootes, Benne W. Holwerda, M. J. Jarvis, N. Maddox, M. Meyer, A. J. Moffett, S. Phillipps, E. N. Taylor, R. A. Windhorst, C. Wolf
Faculty Scholarship
The Deep Extragalactic VIsible Legacy Survey (DEVILS) is a large spectroscopic campaign at the Anglo-Australian Telescope (AAT) aimed at bridging the near and distant Universe by producing the highest completeness survey of galaxies and groups at intermediate redshifts (0.3 < z < 1.0). Our sample consists of ~60 000 galaxies to Y < 21.2mag, over ~6 deg2 in threewell-studied deep extragalactic fields (Cosmic Origins Survey field, COSMOS; Extended Chandra Deep Field South, ECDFS; and the X-ray Multi-Mirror Mission Large-Scale Structure region, XMM-LSS - all Large Synoptic Survey Telescope deep-drill fields). This paper presents the broad experimental design of DEVILS. Our target sample has been selected from deep Visible and Infrared Survey Telescope for Astronomy (VISTA) Y-band imaging (VISTA Deep Extragalactic Observations, VIDEO and UltraVISTA), with photometry measured by PROFOUND. Photometric star/galaxy separation is done on the basis of near-infrared colours and has been validated by visual inspection. To maximize our observing efficiency for faint targets, we employ a redshift feedback strategy, which continually updates our target lists, feeding back the results from the previous night's observations. We also present an overview of the initial spectroscopic observations undertaken in late 2017 and early 2018.
Galaxy And Mass Assembly (Gama): The Environmental Dependence Of The Galaxy Main Sequence, L. Wang, P. Norberg, S. Brough, M. J.I. Brown, E. Da Cunha, L. J. Davies, S. P. Driver, Benne W. Holwerda, A. M. Hopkins, M. A. Lara-Lopez, J. Liske, J. Loveday, M. W. Grootes, C. C. Popescu, A. H. Wright
Galaxy And Mass Assembly (Gama): The Environmental Dependence Of The Galaxy Main Sequence, L. Wang, P. Norberg, S. Brough, M. J.I. Brown, E. Da Cunha, L. J. Davies, S. P. Driver, Benne W. Holwerda, A. M. Hopkins, M. A. Lara-Lopez, J. Liske, J. Loveday, M. W. Grootes, C. C. Popescu, A. H. Wright
Faculty Scholarship
Aims: We aim to investigate if the environment (characterised by the host dark matter halo mass) plays any role in shaping the galaxy star formation main sequence (MS). Methods: The Galaxy and Mass Assembly project (GAMA) combines a spectroscopic survey with photometric information in 21 bands from the far-ultraviolet (FUV) to the far-infrared (FIR). Stellar masses and dust-corrected star-formation rates (SFR) are derived from spectral energy distribution (SED) modelling using MAGPHYS. We use the GAMA galaxy group catalogue to examine the variation of the fraction of star-forming galaxies (SFG) and properties of the MS with respect to the environment. Results: …
Galaxy And Mass Assembly (Gama): The Signatures Of Galaxy Interactions As Viewed From Small-Scale Galaxy Clustering, M. L.P. Gunawardhana, P. Norberg, I. Zehavi, D. J. Farrow, J. Loveday, A. M. Hopkins, L. J.M. Davies, L. Wang, M. Alpaslan, J. Bland-Hawthorn, S. Brough, Benne W. Holwerda, M. S. Owers, A. H. Wright
Galaxy And Mass Assembly (Gama): The Signatures Of Galaxy Interactions As Viewed From Small-Scale Galaxy Clustering, M. L.P. Gunawardhana, P. Norberg, I. Zehavi, D. J. Farrow, J. Loveday, A. M. Hopkins, L. J.M. Davies, L. Wang, M. Alpaslan, J. Bland-Hawthorn, S. Brough, Benne W. Holwerda, M. S. Owers, A. H. Wright
Faculty Scholarship
Statistical studies of galaxy-galaxy interactions often utilize net change in physical properties of progenitors as a function of the separation between their nuclei to trace both the strength and the observable time-scale of their interaction. In this study, we use two-point auto-, cross-, and mark-correlation functions to investigate the extent to which small-scale clustering properties of star-forming galaxies can be used to gain physical insight into galaxy-galaxy interactions between galaxies of similar optical brightness and stellar mass. The Ha star formers, drawn from the highly spatially complete Galaxy And Mass Assembly (GAMA) survey, show an increase in clustering at small …
High Dynamic Range Optical Devices And Applications., Elijah Robert Jensen
High Dynamic Range Optical Devices And Applications., Elijah Robert Jensen
Electronic Theses and Dissertations
Much of what we know about fundamental physical law and the universe derives from observations and measurements using optical methods. The passive use of the electromagnetic spectrum can be the best way of studying physical phenomenon in general with minimal disturbance of the system in the process. While for many applications ambient visible light is sufficient, light outside of the visible range may convey more information. The signals of interest are also often a small fraction of the background, and their changes occur on time scales so quickly that they are visually imperceptible. This thesis reports techniques and technologies developed …
Hst Follow-Up Observations Of Two Bright Z ∼ 8 Candidate Galaxies From The Borg Pure-Parallel Survey, R. C. Livermore, M. Trenti, L. D. Bradley, S. R. Bernard, Benne W. Holwerda, C. A. Mason, T. Treu
Hst Follow-Up Observations Of Two Bright Z ∼ 8 Candidate Galaxies From The Borg Pure-Parallel Survey, R. C. Livermore, M. Trenti, L. D. Bradley, S. R. Bernard, Benne W. Holwerda, C. A. Mason, T. Treu
Faculty Scholarship
We present follow-up imaging of two bright (L > L∗) galaxy candidates at z ≳ 8 from the Brightest of Reionizing Galaxies (BoRG) survey with the F098M filter on the Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). The F098M filter provides an additional constraint on the flux blueward of the spectral break, and the observations are designed to discriminate between low- and high-z photometric redshift solutions for these galaxies. Our results confirm one galaxy, BoRG-0116+1425-747, as a highly probable z ∼ 8 source, but reveal that BoRG-0116+1425-630 - previously the brightest known z > 8 candidate (m AB = 24.5) - is …
Galaxy And Mass Assembly (Gama): Variation In Galaxy Structure Across The Green Valley, Lee S. Kelvin, Malcolm N. Bremer, Steven Phillipps, Philip A. James, Luke J.M. Davies, Roberto De Propris, Amanda J. Moffett, Susan M. Percival, Ivan K. Baldry, Chris A. Collins, Mehmet Alpaslan, Joss Bland-Hawthorn, Sarah Brough, Michelle Cluver, Simon P. Driver, Abdolhosein Hashemizadeh, Benne W. Holwerda, Jarkko Laine, Maritza A. Lara-Lopez, Jochen Liske, Witold Maciejewski, Nicola R. Napolitano, Samantha J. Penny, Cristina C. Popescu, Anne E. Sansom, Will Sutherland, Edward N. Taylor, Eelco Van Kampen, Lingyu Wang
Galaxy And Mass Assembly (Gama): Variation In Galaxy Structure Across The Green Valley, Lee S. Kelvin, Malcolm N. Bremer, Steven Phillipps, Philip A. James, Luke J.M. Davies, Roberto De Propris, Amanda J. Moffett, Susan M. Percival, Ivan K. Baldry, Chris A. Collins, Mehmet Alpaslan, Joss Bland-Hawthorn, Sarah Brough, Michelle Cluver, Simon P. Driver, Abdolhosein Hashemizadeh, Benne W. Holwerda, Jarkko Laine, Maritza A. Lara-Lopez, Jochen Liske, Witold Maciejewski, Nicola R. Napolitano, Samantha J. Penny, Cristina C. Popescu, Anne E. Sansom, Will Sutherland, Edward N. Taylor, Eelco Van Kampen, Lingyu Wang
Faculty Scholarship
Using a sample of 472 local Universe (z < 0.06) galaxies in the stellar mass range 10.25 < logM*/M⊙ < 10.75, we explore the variation in galaxy structure as a function of morphology and galaxy colour. Our sample of galaxies is subdivided into red, green, and blue colour groups and into elliptical and non-elliptical (disk-type) morphologies. Using Kilo- Degree Survey (KiDS) and Visible and Infrared Survey Telescope for Astronomy (VISTA) Kilo-Degree Infrared Galaxy Survey (VIKING) derived postage stamp images, a group of eight volunteers visually classified bars, rings, morphological lenses, tidal streams, shells, and signs of merger activity for all systems. We find a significant surplus of rings (2.3s) and lenses (2.9s) in disk-type galaxies as they transition across the green valley. Combined, this implies a joint ring/lens green valley surplus significance of 3.3s relative to equivalent disk-types within either the blue cloud or the red sequence. We recover a bar fraction of ~44 per cent which remains flat with colour, however, we find that the presence of a bar acts to modulate the incidence of rings and (to a lesser extent) lenses, with rings in barred disk-type galaxies more common by ~20-30 percentage points relative to their unbarred counterparts, regardless of colour. Additionally, green valley disk-type galaxies with a bar exhibit a significant 3.0s surplus of lenses relative to their blue/red analogues. The existence of such structures rules out violent transformative events as the primary end-of-life evolutionary mechanism, with a more passive scenario the favoured candidate for the majority of galaxies rapidly transitioning across the green valley.
Galaxy And Mass Assembly (Gama): Gas Fuelling Of Spiral Galaxies In The Local Universe Ii. - Direct Measurement Of The Dependencies On Redshift And Host Halo Mass Of Stellar Mass Growth In Central Disc Galaxies, M. W. Grootes, A. Dvornik, R. J. Laureijs, R. J. Tuffs, C. C. Popescu, A. S.G. Robotham, J. Liske, M. J.I. Brown, Benne W. Holwerda, L. Wang
Galaxy And Mass Assembly (Gama): Gas Fuelling Of Spiral Galaxies In The Local Universe Ii. - Direct Measurement Of The Dependencies On Redshift And Host Halo Mass Of Stellar Mass Growth In Central Disc Galaxies, M. W. Grootes, A. Dvornik, R. J. Laureijs, R. J. Tuffs, C. C. Popescu, A. S.G. Robotham, J. Liske, M. J.I. Brown, Benne W. Holwerda, L. Wang
Faculty Scholarship
We present a detailed analysis of the specific star formation rate-stellar mass (sSFR-M*) of z ≤ 0.13 disc central galaxies using a morphologically selected mass-complete sample (M* ≥ 109.5M⊙). Considering samples of grouped and ungrouped galaxies, we find the sSFR-M* relations of disc-dominated central galaxies to have no detectable dependence on host dark-matter halo (DMH) mass, even where weak-lensing measurements indicate a difference in halo mass of a factor ≳ 5.We further detect a gradual evolution of the sSFR-M* relation of non-grouped (field) central disc galaxies with redshift, even over a Δz ≈ 0.04 (≈5 × 108 yr) interval, while …
Galaxy And Mass Assembly (Gama): Morphological Transformation Of Galaxies Across The Green Valley, M. N. Bremer, S. Phillipps, S. Kelvin, R. De Propris, Rebecca Kennedy, Amanda J. Moffett, S. Bamford, L. J.M. Davies, S. P. Driver, B. Häußler, Benne W. Holwerda, A. Hopkins, P. A. James, J. Liske, S. Percival, N. Taylor
Galaxy And Mass Assembly (Gama): Morphological Transformation Of Galaxies Across The Green Valley, M. N. Bremer, S. Phillipps, S. Kelvin, R. De Propris, Rebecca Kennedy, Amanda J. Moffett, S. Bamford, L. J.M. Davies, S. P. Driver, B. Häußler, Benne W. Holwerda, A. Hopkins, P. A. James, J. Liske, S. Percival, N. Taylor
Faculty Scholarship
We explore constraints on the joint photometric and morphological evolution of typical low redshift galaxies as they move from the blue cloud through the green valley and on to the red sequence. We select Galaxy And Mass Assembly (GAMA) survey galaxies with 10.25 < log(M*/Mo˙) < 10.75 and z < 0.2 classified according to their intrinsic u* - r* colour. From single component Śersic fits, we find that the stellar mass-sensitive K-band profiles of red and green galaxy populations are very similar while g-band profiles indicate more disc-like morphologies for the green galaxies: apparent (optical) morphological differences arise primarily from radial mass-to-light ratio variations. Two-component fits show that most green galaxies have significant bulge and disc components and that the blue to red evolution is driven by colour change in the disc. Together, these strongly suggest that galaxies evolve from blue to red through secular disc fading and that a strong bulge is present prior to any decline in star formation. The relative abundance of the green population implies a typical time-scale for traversing the green valley ~1-2 Gyr and is independent of environment, unlike that of the red and blue populations. While environment likely plays a role in triggering the passage across the green valley, it appears to have little effect on time taken. These results are consistent with a green valley population dominated by (early type) disc galaxies that are insufficiently supplied with gas to maintain previous levels of disc star formation, eventually attaining passive colours. No single event is needed to quench their star formation.
Galaxy And Mass Assembly (Gama): Impact Of The Group Environment On Galaxy Star Formation, S. Barsanti, M. S. Owers, S. Brough, L. J.M. Davies, S. P. Driver, M. L.P. Gunawardhana, Benne W. Holwerda, J. Liske, J. Loveday, K. A. Pimbblet, A. S.G. Robotham, E. N. Taylor
Galaxy And Mass Assembly (Gama): Impact Of The Group Environment On Galaxy Star Formation, S. Barsanti, M. S. Owers, S. Brough, L. J.M. Davies, S. P. Driver, M. L.P. Gunawardhana, Benne W. Holwerda, J. Liske, J. Loveday, K. A. Pimbblet, A. S.G. Robotham, E. N. Taylor
Faculty Scholarship
We explore how the group environment may affect the evolution of star-forming galaxies. We select 1197 Galaxy And Mass Assembly groups at 0.05 ≤ z ≤ 0.2 and analyze the projected phase space (PPS) diagram, i.e., the galaxy velocity as a function of projected group-centric radius, as a local environmental metric in the low-mass halo regime 1012 ≤ (M 200/M o) < 1014. We study the properties of star-forming group galaxies, exploring the correlation of star formation rate (SFR) with radial distance and stellar mass. We find that the fraction of star-forming group members is higher in the PPS regions dominated by recently accreted galaxies, whereas passive galaxies dominate the virialized regions. We observe a small decline in specific SFR of star-forming galaxies toward the group center by a factor ∼1.2 with respect to field galaxies. Similar to cluster studies, we conclude for low-mass halos that star-forming group galaxies represent an infalling population from the field to the halo and show suppressed star formation.
Galaxy And Mass Assembly (Gama): The Effect Of Galaxy Group Environment On Active Galactic Nuclei, Yjan A. Gordon, Kevin A. Pimbblet, Matt S. Owers, Joss Bland-Hawthorn, Sarah Brough, Michael J.I. Brown, Michelle E. Cluver, Scott M. Croom, Benne W. Holwerda, Jonathan Loveday, Smriti Mahajan, Lingyu Wang
Galaxy And Mass Assembly (Gama): The Effect Of Galaxy Group Environment On Active Galactic Nuclei, Yjan A. Gordon, Kevin A. Pimbblet, Matt S. Owers, Joss Bland-Hawthorn, Sarah Brough, Michael J.I. Brown, Michelle E. Cluver, Scott M. Croom, Benne W. Holwerda, Jonathan Loveday, Smriti Mahajan, Lingyu Wang
Faculty Scholarship
In galaxy clusters, efficiently accreting active galactic nuclei (AGNs) are preferentially located in the infall regions of the cluster projected phase-space, and are rarely found in the cluster core. This has been attributed to both an increase in triggering opportunities for infalling galaxies, and a reduction of those mechanisms in the hot, virialized, cluster core. Exploiting the depth and completeness (98 per cent at r < 19.8mag) of the Galaxy And Mass Assembly survey (GAMA), we probe down the group halo mass function to assess whether AGNs are found in the same regions in groups as they are in clusters. We select 451 optical AGNs from 7498 galaxies with log10(M*/M⊙) > 9.9 in 695 groups with 11.53 ≤ log10(M200/M⊙) ≤ 14.56 at < 0.15. By analysing the projected phase-space positions of these galaxies, we demonstrate that when split both radially, and into physically derived infalling and core populations, AGN position within group projected phase-space is dependent on halo mass. For groups with log10(M200/M⊙) > 13.5,AGNs are preferentially found in the infalling galaxy populationwith 3.6s confidence. At lower halo masses, we observe no difference in AGN fraction between core …
Galaxy And Mass Assembly (Gama): Blue Spheroids Within 87 Mpc, Smriti Mahajan, Michael J. Drinkwater, S. Driver, A. M. Hopkins, Alister W. Graham, S. Brough, Michael J.I. Brown, Benne W. Holwerda, Matt S. Owers, Kevin A. Pimbblet
Galaxy And Mass Assembly (Gama): Blue Spheroids Within 87 Mpc, Smriti Mahajan, Michael J. Drinkwater, S. Driver, A. M. Hopkins, Alister W. Graham, S. Brough, Michael J.I. Brown, Benne W. Holwerda, Matt S. Owers, Kevin A. Pimbblet
Faculty Scholarship
In this paper, we test if nearby blue spheroid (BSph) galaxies may become the progenitors of star-forming spiral galaxies or passively evolving elliptical galaxies. Our sample comprises 428 galaxies of various morphologies in the redshift range 0.002 < Ζ < 0.02 (8-87 Mpc) with panchromatic data from the Galaxy and Mass Assembly survey. We find that BSph galaxies are structurally (mean effective surface brightness, effective radius) very similar to their passively evolving red counterparts. However, their star formation and other properties such as colour, age, and metallicity are more like star-forming spirals than spheroids (ellipticals and lenticulars). We show that BSph galaxies are statistically distinguishable from other spheroids as well as spirals in the multidimensional space mapped by luminosity-weighted age, metallicity, dust mass, and specific star formation rate. We use HI data to reveal that some of the BSphs are (further) developing their discs, hence their blue colours. They may eventually become spiral galaxies - if sufficient gas accretion occurs - or more likely fade into low-mass red galaxies.