Publications by Roger Davies

The fifteenth data release of the Sloan Digital Sky Surveys: First release of MaNGA-derived quantities, data visualization tools, and Stellar Library

Astrophysical Journal Supplement Institute of Physics 240 (2019)

DS Aguado, R Ahumada, A Almeida, M Cappellari, R Davies, C Lintott

Twenty years have passed since first light for the Sloan Digital Sky Survey (SDSS). Here, we release data taken by the fourth phase of SDSS (SDSS-IV) across its first three years of operation (2014 July–2017 July). This is the third data release for SDSS-IV, and the 15th from SDSS (Data Release Fifteen; DR15). New data come from MaNGA—we release 4824 data cubes, as well as the first stellar spectra in the MaNGA Stellar Library (MaStar), the first set of survey-supported analysis products (e.g., stellar and gas kinematics, emission-line and other maps) from the MaNGA Data Analysis Pipeline, and a new data visualization and access tool we call "Marvin." The next data release, DR16, will include new data from both APOGEE-2 and eBOSS; those surveys release no new data here, but we document updates and corrections to their data processing pipelines. The release is cumulative; it also includes the most recent reductions and calibrations of all data taken by SDSS since first light. In this paper, we describe the location and format of the data and tools and cite technical references describing how it was obtained and processed. The SDSS website ( has also been updated, providing links to data downloads, tutorials, and examples of data use. Although SDSS-IV will continue to collect astronomical data until 2020, and will be followed by SDSS-V (2020–2025), we end this paper by describing plans to ensure the sustainability of the SDSS data archive for many years beyond the collection of data.

Radial measurements of IMF-sensitive absorption features in two massive ETGs


SP Vaughan, RL Davies, S Zieleniewski, RCW Houghton

The stellar population and initial mass function of NGC 1399 with MUSE


SP Vaughan, RL Davies, S Zieleniewski, RCW Houghton

Donald Lynden-Bell (1935-2018)

Nature Nature Publishing Group 555 (2018) 166-

R Davies

In 1969, Donald Lynden-Bell became the first astrophysicist to suggest that supermassive black holes in the cores of galaxies might generate the profuse energy put out by quasars — the astonishingly luminous distant bodies identified by astronomer Maarten Schmidt earlier that decade. Lynden-Bell proposed that quasars are powered by the release of gravitational energy as material falls into the deep potential well of the black hole, a process that is much more efficient than thermonuclear fusion

The KMOS Cluster Survey (KCS). II. The Effect of Environment on the Structural Properties of Massive Cluster Galaxies at Redshift 1.39 < z < 1.61


JCC Chan, A Beifiori, RP Saglia, JT Mendel, JP Stott, R Bender, A Galametz, DJ Wilman, M Cappellari, RL Davies, RCW Houghton, LJ Prichard, IJ Lewis, R Sharples, M Wegner

A photometric analysis of Abell 1689: two-dimensional multistructure decomposition, morphological classification and the Fundamental Plane


ED Bonta, RL Davies, RCW Houghton, F D'Eugenio, J Mendez-Abreu

The SAMI Galaxy Survey: the cluster redshift survey, target selection and cluster properties


MS Owers, JT Allen, I Baldry, JJ Bryant, GN Cecil, L Cortese, SM Croom, SP Driver, LMR Fogarty, AW Green, E Helmich, JTA De Jong, K Kuijken, S Mahajan, J McFarland, MB Pracy, AGS Robotham, G Sikkema, S Sweet, EN Taylor, GV Kleijn, AE Bauer, J Bland-Hawthorn, S Brough, M Colless, WJ Couch, RL Davies, MJ Drinkwater, M Goodwin, AM Hopkins, IS Konstantopoulos, C Foster, JS Lawrence, NPF Lorente, AM Medling, N Metcalfe, SN Richards, JV De Sande, N Scott, T Shanks, R Sharp, AD Thomas, C Tonini

The SAMI Galaxy Survey: Mass as the Driver of the Kinematic Morphology-Density Relation in Clusters


S Brough, J van de Sande, MS Owers, F d'Eugenio, R Sharp, L Cortese, N Scott, SM Croom, R Bassett, K Bekki, J Bland-Hawthorn, JJ Bryant, R Davies, MJ Drinkwater, SP Driver, C Foster, G Goldstein, AR Lopez-Sanchez, AM Medling, SM Sweet, DS Taranu, C Tonini, SK Yi, M Goodwin, JS Lawrence, SN Richards

The most massive galaxies in clusters are already fully grown at z similar to 0.5


LJ Oldham, RCW Houghton, RL Davies

Self-consistent Bulge/Disk/Halo Galaxy Dynamical Modeling Using Integral Field Kinematics


DS Taranu, D Obreschkow, JJ Dubinski, LMR Fogarty, J van de Sande, B Catinella, L Cortese, A Moffett, ASG Robotham, JT Allen, J Bland-Hawthorn, JJ Bryant, M Colless, SM Croom, F D'Eugenio, RL Davies, MJ Drinkwater, SP Driver, M Goodwin, IS Konstantopoulos, JS Lawrence, AR Lopez-Sanchez, NPF Lorente, AM Medling, JR Mould, MS Owers, C Power, SN Richards, C Tonini

Implications for the origin of early-type dwarf galaxies - the discovery of rotation in isolated, low-mass early-type galaxies


J Janz, SJ Penny, AW Graham, DA Forbes, RL Davies

Radial gradients in initial mass function sensitive absorption features in the Coma brightest cluster galaxies

Monthly Notices of the Royal Astronomical Society Oxford University Press 465 (2016) 192-212

S Zieleniewski, RCW Houghton, N Thatte, RL Davies, SP Vaughan

Using the Oxford ShortWavelength Integral Field specTrograph, we trace radial variations of initial mass function (IMF)-sensitive absorption features of three galaxies in the Coma cluster. We obtain resolved spectroscopy of the central 5 kpc for the two central brightest cluster galaxies (BCGs) NGC4889, NGC4874, and the BCG in the south-west group NGC4839, as well as unresolved data for NGC4873 as a low-σ* control.We present radial measurements of the IMF-sensitive features: sodium Na I SDSS , calcium triplet CaT, and iron-hydride FeH0.99, along with the magnesium Mg I0.88 and titanium oxide TiO0.89 features. We employ two separate methods for both telluric correction and sky subtraction around the faint FeH feature to verify our analysis. Within NGC4889 we find strong gradients of Na I SDSS and CaT but a flat FeH profile, which, from comparing to stellar population synthesis models, suggests an old, α-enhanced population with a Chabrier, or even bottom-light IMF. The age and abundance are in line with previous studies but the normal IMF is in contrast to recent results suggesting an increased IMF slope with increased velocity dispersion.We measure flat Na I SDSS and FeH profiles within NGC4874, and determine an old, possibly slightly α-enhanced and Chabrier IMF population. We find an α-enhanced, Chabrier IMF population in NGC4873. Within NGC4839 we measure both strong Na I SDSS and strong FeH, although with a large systematic uncertainty, suggesting a possible heavier IMF. The IMFswe infer for these galaxies are supported by published dynamical modelling. We stress that IMF constraints should be corroborated by further spectral coverage and independent methods on a galaxy-by-galaxy basis.

Sloan Digital Sky Survey IV: Mapping the Milky Way, nearby galaxies, and the distant Universe

Astronomical Journal Institute of Physics 154 (2017) 28-

MA Bershady, B Abolfathi, M Cappellari, R Davies

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median $z\sim 0.03$). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between $z\sim 0.6$ and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July.



J van de Sande, J Bland-Hawthorn, LMR Fogarty, L Cortese, F d'Eugenio, SM Croom, N Scott, JT Allen, S Brough, JJ Bryant, G Cecil, M Colless, WJ Couch, R Davies, PJ Elahi, C Foster, G Goldstein, M Goodwin, B Groves, I-T Ho, H Jeong, DH Jones, IS Konstantopoulos, JS Lawrence, SK Leslie, AR Lopez-Sanchez, RM McDermid, R McElroy, AM Medling, S Oh, MS Owers, SN Richards, AL Schaefer, R Sharp, SM Sweet, D Taranu, C Tonini, CJ Walcher, SK Yi

The KMOS Cluster Survey (KCS). I. The fundamental plane and the formation ages of cluster galaxies at redshift 1.4 &lt; Z &lt; 1.6

Astrophysical Journal American Astronomical Society 846 (2017) 1-25

A Beifiori, JT Mendel, JCC Chan, RP Saglia, R Bender, M Cappellari, RL Davies, A Galametz, RCW Houghton, LJ Prichard, R Smith, JP Stott, DJ Wilman, IJ Lewis, R Sharples, M Wegner

The American Astronomical Society. All rights reserved. We present the analysis of the fundamental plane (FP) for a sample of 19 massive red-sequence galaxies (M· &gt; ×4 10 10 M·) in three known overdensities at 1.39 1.61 &lt; &lt; z from the K-band Multi-object Spectrograph (KMOS) Cluster Survey, a guaranteed-time program with spectroscopy from the KMOS at the VLT and imaging from the Hubble Space Telescope. As expected, we find that the FP zero-point in B band evolves with redshift, from the value 0.443 of Coma to -0.10±0.09, -0.19±0.05, and -0.29±0.12 for our clusters at z = 1.39, z = 1.46, and z = 1.61, respectively. For the most massive galaxies (log 1 M M· &gt; 1) in our sample, we translate the FP zero-point evolution into a mass-to-light-ratio M/L evolution, finding D log 0.46 0.10 M L z B = - (D log )0.52 0.07 M L z B = -to(D log ) 0.55 0.10 M L z B = - respectively. We assess the potential contribution of the galaxy structural and stellar velocity dispersion evolution to the evolution of the FP zero-point and find it to be ∼6%-35% of the FP zero-point evolution. The rate of M/L evolution is consistent with galaxies evolving passively. Using single stellar population models, we find an average age of 2.33- +0.51 0.86 Gyr for the log 1 M M· &gt; 1 galaxies in our massive and virialized cluster at z = 1.39,1.59- +0.62 1.40 Gyr in a massive but not virialized cluster at z = 1.46, and 1.20- +0.47 1.03 Gyr in a protocluster at z = 1.61. After accounting for the difference in the age of the universe between redshifts, the ages of the galaxies in the three overdensities are consistent within the errors, with possibly a weak suggestion that galaxies in the most evolved structure are older.

Implications for the Origin of Early-type Dwarf Galaxies: A Detailed Look at the Isolated Rotating Early-type Dwarf Galaxy LEDA 2108986 (CG 611), Ramifications for the Fundamental Plane's S-K(2) Kinematic Scaling, and the Spin-Ellipticity Diagram


AW Graham, J Janz, SJ Penny, IV Chilingarian, BC Ciambur, DA Forbes, RL Davies

The SAMI Galaxy Survey: global stellar populations on the size-mass plane


N Scott, S Brough, SM Croom, RL Davies, J van de Sande, JT Allen, J Bland-Hawthorn, JJ Bryant, L Cortese, F D'Eugenio, C Federrath, I Ferreras, M Goodwin, B Groves, I Konstantopoulos, JS Lawrence, AM Medling, AJ Moffett, MS Owers, S Richards, ASG Robotham, C Tonini, SK Yi

The KMOS Cluster Survey (KCS). III. Fundamental plane of cluster galaxies at z ≃ 1.80 in JKCS 041

Astrophysical Journal Institute of Physics 850 (2017) 203-

LJ Prichard, RL Davies, A Beifiori, JCC Chan, M Cappellari, RCW Houghton, JT Mendel, R Bender, A Galametz, RP Saglia, JP Stott, DJ Wilman, IJ Lewis, R Sharples, M Wegner

We present data for 16 galaxies in the overdensity JKCS 041 at z ≃ 1.80 as part of the K-band Multi-Object Spectrograph (KMOS) Cluster Survey (KCS). With 20 hr integrations, we have obtained deep absorption-line spectra from which we derived velocity dispersions for seven quiescent galaxies. We combined photometric parameters derived from Hubble Space Telescope images with the dispersions to construct a fundamental plane (FP) for quiescent galaxies in JKCS 041. From the zero-point evolution of the FP, we derived a formation redshift for the galaxies of z form = 3.0 ± 0.3, corresponding to a mean age of 1.4 ± 0.2 Gyr. We tested the effect of structural and velocity dispersion evolution on our FP zero-point and found a negligible contribution when using dynamical mass-normalized parameters (∼3%) but a significant contribution from stellar-mass-normalized parameters (∼42%). From the relative velocities of the galaxies, we probed the 3D structure of these 16 confirmed members of JKCS 041 and found that a group of galaxies in the southwest of the overdensity had systematically higher velocities. We derived ages for the galaxies in the different groups from the FP. We found that the eastextending group had typically older galaxies (2.1 +0.3 0.2 Gyr) than those in the southwest group (0.3 ± 0.2 Gyr). Although based on small numbers, the overdensity dynamics, morphology, and age results could indicate that JKCS 041 is in formation and may comprise two merging groups of galaxies. This result could link large-scale structure to ages of galaxies for the first time at this redshift.

Sizes, colour gradients and resolved stellar mass distributions for the massive cluster galaxies in XMMUJ2235-2557 at z=1.39


JCC Chan, A Beifiori, JT Mendel, RP Saglia, R Bender, M Fossati, A Galametz, M Wegner, DJ Wilman, M Cappellari, RL Davies, RCW Houghton, LJ Prichard, IJ Lewis, R Sharples, JP Stott

The atlas 3D Project – XXXI. Nuclear radio emission in nearby early-type galaxies

Monthly Notices of the Royal Astronomical Society Oxford University Press 458 (2016) 2221–2268-

K Nyland, LM Young, JM Wrobel, M Sarzi, R Morganti, K Alatalo, L Blitz, F Bournaud, M Bureau, M Cappellari, AF Crocker, RL Davies, TA Davis, PT de Zeeuw, P-A Duc, E Emsellem, S Khochfar, D Krajnović, H Kuntschner, RM McDermid, T Naab, T Oosterloo, N Scott, P Serra, A-M Weijmans

We present the results of a high-resolution, 5 GHz, Karl G. Jansky Very Large Array study of the nuclear radio emission in a representative subset of the ATLAS3D survey of early-type galaxies (ETGs). We find that 51 ± 4 per cent of the ETGs in our sample contain nuclear radio emission with luminosities as low as 1018 W Hz-1. Most of the nuclear radio sources have compact (≲25-110 pc) morphologies, although ~10 per cent display multicomponent core+jet or extended jet/lobe structures. Based on the radio continuum properties, as well as optical emission line diagnostics and the nuclear X-ray properties, we conclude that the majority of the central 5 GHz sources detected in the ATLAS3D galaxies are associated with the presence of an active galactic nucleus (AGN). However, even at subarcsecond spatial resolution, the nuclear radio emission in some cases appears to arise from low-level nuclear star formation rather than an AGN, particularly when molecular gas and a young central stellar population is present. This is in contrast to popular assumptions in the literature that the presence of a compact, unresolved, nuclear radio continuum source universally signifies the presence of an AGN. Additionally, we examine the relationships between the 5 GHz luminosity and various galaxy properties including the molecular gas mass and - for the first time - the global kinematic state. We discuss implications for the growth, triggering, and fuelling of radio AGNs, as well as AGN-driven feedback in the continued evolution of nearby ETGs.