Showing papers by "Matt S. Owers published in 2018"
Liverpool John Moores University1, University of Hamburg2, Monash University, Clayton campus3, University of Western Australia4, University of St Andrews5, Cardiff University6, University of Edinburgh7, Ames Research Center8, University of New South Wales9, University of the Western Cape10, Max Planck Society11, University of Bonn12, Australian Astronomical Observatory13, University of Sussex14, Vanderbilt University15, Durham University16, Macquarie University17, Swinburne University of Technology18, University of Nottingham19, University of Sydney20, University of Bristol21, Australian National University22, European Space Research and Technology Centre23, University of Louisville24, Leiden University25, University of Copenhagen26, Queen Mary University of London27, European Southern Observatory28
TL;DR: The Galaxy And Mass Assembly (GAMA) survey as discussed by the authors is a spectroscopic redshift and multiwavelength photometric survey in three equatorial regions each of 60.0, G12, and G15.
Abstract: We describe data release 3 (DR3) of the Galaxy And Mass Assembly (GAMA) survey. The GAMA survey is a spectroscopic redshift and multiwavelength photometric survey in three equatorial regions each of 60.0 deg2 (G09, G12, and G15), and two southern regions of 55.7 deg2 (G02) and 50.6 deg2 (G23). DR3 consists of: the first release of data covering the G02 region and of data on H-ATLAS (Herschel – Astrophysical Terahertz Large Area Survey) sources in the equatorial regions; and updates to data on sources released in DR2. DR3 includes 154 809 sources with secure redshifts across four regions. A subset of the G02 region is 95.5 per cent redshift complete to r < 19.8 mag over an area of 19.5 deg2, with 20 086 galaxy redshifts, that overlaps substantially with the XXL survey (X-ray) and VIPERS (redshift survey). In the equatorial regions, the main survey has even higher completeness (98.5 per cent), and spectra for about 75 per cent of H-ATLAS filler targets were also obtained. This filler sample extends spectroscopic redshifts, for probable optical counterparts to H-ATLAS submillimetre sources, to 0.8 mag deeper (r < 20.6 mag) than the GAMA main survey. There are 25 814 galaxy redshifts for H-ATLAS sources from the GAMA main or filler surveys. GAMA DR3 is available at the survey website (www.gama-survey.org/dr3/).
176 citations
Aix-Marseille University1, University of Bristol2, DSM3, University of Bonn4, Universidad de Guanajuato5, University of Geneva6, INAF7, Durham University8, University of Padua9, Australian Astronomical Observatory10, Istanbul University11, European Space Agency12, Liverpool John Moores University13, Monash University14, University of Bologna15, University of St Andrews16, University of Nottingham17, University of Michigan18, Max Planck Society19, Chalmers University of Technology20, University of Hamburg21, University of Nice Sophia Antipolis22, Macquarie University23, University of Toulouse24, Aristotle University of Thessaloniki25, Jagiellonian University26, European Southern Observatory27, University of Birmingham28, University of Colorado Boulder29, Ames Research Center30, University of Oxford31, University of Victoria32
TL;DR: In this paper, the properties of the XXL cluster catalogue are described in detail, as well as associated catalogues of more specific objects such as super-clusters and fossil groups, and the complete subset of clusters for which the selection function is well determined plus all X-ray clusters which are, to date, confirmed.
Abstract: Context. In the currently debated context of using clusters of galaxies as cosmological probes, the need for well-defined cluster samples is critical.Aims. The XXL Survey has been specifically designed to provide a well characterised sample of some 500 X-ray detected clusters suitable for cosmological studies. The main goal of present article is to make public and describe the properties of the cluster catalogue in its present state, as well as of associated catalogues of more specific objects such as super-clusters and fossil groups.Methods. Following from the publication of the hundred brightest XXL clusters, we now release a sample containing 365 clusters in total, down to a flux of a few 10−15 erg s−1 cm−2 in the [0.5–2] keV band and in a 1′ aperture. This release contains the complete subset of clusters for which the selection function is well determined plus all X-ray clusters which are, to date, spectroscopically confirmed. In this paper, we give the details of the follow-up observations and explain the procedure adopted to validate the cluster spectroscopic redshifts. Considering the whole XXL cluster sample, we have provided two types of selection, both complete in a particular sense: one based on flux-morphology criteria, and an alternative based on the [0.5–2] keV flux within 1 arcmin of the cluster centre. We have also provided X-ray temperature measurements for 80% of the clusters having a flux larger than 9 × 10−15 erg s−1 cm−2 .Results. Our cluster sample extends from z ~ 0 to z ~ 1.2, with one cluster at z ~ 2. Clusters were identified through a mean number of six spectroscopically confirmed cluster members. The largest number of confirmed spectroscopic members in a cluster is 41. Our updated luminosity function and luminosity–temperature relation are compatible with our previous determinations based on the 100 brightest clusters, but show smaller uncertainties. We also present an enlarged list of super-clusters and a sample of 18 possible fossil groups.Conclusions. This intermediate publication is the last before the final release of the complete XXL cluster catalogue when the ongoing C2 cluster spectroscopic follow-up is complete. It provides a unique inventory of medium-mass clusters over a 50 deg2 area out to z ~ 1.
102 citations
California Institute of Technology1, Australian National University2, University of Western Australia3, University of Sydney4, Australian Astronomical Observatory5, Max Planck Society6, Vanderbilt University7, Swinburne University of Technology8, University of New South Wales9, University of North Carolina at Chapel Hill10, University of Queensland11, Macquarie University12, University of Melbourne13, Leibniz Institute for Astrophysics Potsdam14, University of Bonn15
TL;DR: In this paper, the authors presented the ∼800 star formation rate maps for the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey based on H'α emission maps, corrected for dust attenuation via the Balmer decrement, that are included in the SAMI Public Data Release 1.
Abstract: We present the ∼800 star formation rate maps for the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey based on H α emission maps, corrected for dust attenuation via the Balmer decrement, that are included in the SAMI Public Data Release 1. We mask out spaxels contaminated by non-stellar emission using the [O III]/H β, [N II]/H α, [S II]/H α, and [O I]/H α line ratios. Using these maps, we examine the global and resolved star-forming main sequences of SAMI galaxies as a function of morphology, environmental density, and stellar mass. Galaxies further below the star-forming main sequence are more likely to have flatter star formation profiles. Early-type galaxies split into two populations with similar stellar masses and central stellar mass surface densities. The main-sequence population has centrally concentrated star formation similar to late-type galaxies, while galaxies >3σ below the main sequence show significantly reduced star formation most strikingly in the nuclear regions. The split populations support a two-step quenching mechanism, wherein halo mass first cuts off the gas supply and remaining gas continues to form stars until the local stellar mass surface density can stabilize the reduced remaining fuel against further star formation. Across all morphologies, galaxies in denser environments show a decreased specific star formation rate from the outside in, supporting an environmental cause for quenching, such as ram-pressure stripping or galaxy interactions.
95 citations
TL;DR: In this article, the properties of the XXL cluster catalogue in its present state, as well as associated catalogues as super-clusters and fossil groups, are described in detail.
Abstract: In the currently debated context of using clusters of galaxies as cosmological probes, the need for well-defined cluster samples is critical. The XXL Survey has been specifically designed to provide a well characterised sample of some 500 X-ray detected clusters suitable for cosmological studies. The main goal of present article is to make public and describe the properties of the cluster catalogue in its present state, as well as of associated catalogues as super-clusters and fossil groups. We release a sample containing 365 clusters in total. We give the details of the follow-up observations and explain the procedure adopted to validate the cluster spectroscopic redshifts. Considering the whole XXL cluster sample, we have provided two types of selection, both complete in a particular sense: one based on flux-morphology criteria, and an alternative based on the [0.5-2] keV flux within one arcmin of the cluster centre. We have also provided X-ray temperature measurements for 80$\%$ of the clusters having a flux larger than 9$\times$10$^{-15}$$\rm \thinspace erg \, s^{-1} \, cm^{-2}$. Our cluster sample extends from z$\sim$0 to z$\sim$1.2, with one cluster at z$\sim$2. Clusters were identified through a mean number of six spectroscopically confirmed cluster members. Our updated luminosity function and luminosity-temperature relation are compatible with our previous determinations based on the 100 brightest clusters, but show smaller uncertainties. We also present an enlarged list of super-clusters and a sample of 18 possible fossil groups. This intermediate publication is the last before the final release of the complete XXL cluster catalogue when the ongoing C2 cluster spectroscopic follow-up is complete. It provides a unique inventory of medium-mass clusters over a 50~\dd\ area out to z$\sim$1.
94 citations
University of Sydney1, Australian National University2, Australian Astronomical Observatory3, Macquarie University4, California Institute of Technology5, University of New South Wales6, University of Western Australia7, University of Queensland8, Leiden University9, National Autonomous University of Mexico10, University of Wisconsin-Madison11, Swinburne University of Technology12
TL;DR: The second major release of data from the Sydney - Australian Astronomical Observatory Multi-Object Integral Field Spectrograph (SAMI) Galaxy Survey as discussed by the authors was released in 2013.
Abstract: We present the second major release of data from the Sydney - Australian Astronomical Observatory Multi-Object Integral Field Spectrograph (SAMI) Galaxy Survey. Data Release Two includes data for 1559 galaxies, about 50 per cent of the full survey. Galaxies included have a redshift range 0.004 11], the velocity dispersion strongly increases towards the centre, whereas below log (M-*/M-circle dot) < 10 we find no evidence for a clear increase in the central velocity dispersion. This suggests a transition mass around log (M-*/M-circle dot) similar to 10 for galaxies with or without a dispersion-dominated bulge.
79 citations
Durham University1, European Southern Observatory2, University of Oxford3, Lancaster University4, Institute for the Physics and Mathematics of the Universe5, Leiden University6, University of Edinburgh7, University of the Western Cape8, University of Copenhagen9, University of Sydney10, University of Western Australia11, Australian National University12, Swinburne University of Technology13, Australian Astronomical Observatory14, Macquarie University15
TL;DR: In this article, velocity dispersion properties of 472 z~0.9 star-forming galaxies observed as part of the KMOS Redshift One Spectroscopic Survey (KROSS) were analyzed.
Abstract: We analyse the velocity dispersion properties of 472 z~0.9 star-forming galaxies observed as part of the KMOS Redshift One Spectroscopic Survey (KROSS). The majority of this sample is rotationally dominated (83 +/- 5% with v_C/sigma_0 > 1) but also dynamically hot and highly turbulent. After correcting for beam smearing effects, the median intrinsic velocity dispersion for the final sample is sigma_0 = 43.2 +/- 0.8 km/s with a rotational velocity to dispersion ratio of v_C/sigma_0 = 2.6 +/- 0.1. To explore the relationship between velocity dispersion, stellar mass, star formation rate and redshift we combine KROSS with data from the SAMI survey (z~0.05) and an intermediate redshift MUSE sample (z~0.5). While there is, at most, a weak trend between velocity dispersion and stellar mass, at fixed mass there is a strong increase with redshift. At all redshifts, galaxies appear to follow the same weak trend of increasing velocity dispersion with star formation rate. Our results are consistent with an evolution of galaxy dynamics driven by disks that are more gas rich, and increasingly gravitationally unstable, as a function of increasing redshift. Finally, we test two analytic models that predict turbulence is driven by either gravitational instabilities or stellar feedback. Both provide an adequate description of the data, and further observations are required to rule out either model.
76 citations
Australian Astronomical Observatory1, University of Sydney2, University of Western Australia3, Australian National University4, California Institute of Technology5, Max Planck Society6, University of Queensland7, Macquarie University8, University of New South Wales9, University of North Carolina at Chapel Hill10, University of Newcastle11, University of Hamburg12, Swinburne University of Technology13, University of St Andrews14, University of Melbourne15
TL;DR: The first major release of data from the SAMI Galaxy Survey as discussed by the authors focuses on the emission-line physics of galaxies and includes data for 772 galaxies, about 20% of the full survey.
Abstract: We present the first major release of data from the SAMI Galaxy Survey. This data release focuses on the emission-line physics of galaxies. Data Release One includes data for 772 galaxies, about 20 per cent of the full survey. Galaxies included have the redshift range 0.004 < z < 0.092, a large mass range (7.6 < log M*/ M⊙ < 11.6), and star formation rates of ∼10^(−4) to ∼10^1M⊙ yr^(−1). For each galaxy, we include two spectral cubes and a set of spatially resolved 2D maps: single- and multi-component emission-line fits (with dust-extinction corrections for strong lines), local dust extinction, and star formation rate. Calibration of the fibre throughputs, fluxes, and differential atmospheric refraction has been improved over the Early Data Release. The data have average spatial resolution of 2.16 arcsec (full width at half-maximum) over the 15 arcsec diameter field of view and spectral (kinematic) resolution of R = 4263 (σ = 30 km s^(−1)) around H α. The relative flux calibration is better than 5 per cent, and absolute flux calibration has an rms of 10 per cent. The data are presented online through the Australian Astronomical Observatory's Data Central.
72 citations
University of St Andrews1, Johns Hopkins University2, University of Edinburgh3, University of Bristol4, Australian Astronomical Observatory5, Leiden University6, Macquarie University7, Monash University, Clayton campus8, University of Hull9, University of Central Lancashire10, Netherlands Institute for Space Research11, University of Groningen12, Ames Research Center13, University of Sydney14, Australian National University15, University of Louisville16, Swinburne University of Technology17
TL;DR: In this paper, the authors identify potentially rapidly transitioning post-starburst (PSB) and slower transitioning green-valley galaxies, and find that the quiescent population has grown more slowly in number density at high masses than at intermediate masses.
Abstract: 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 8 Gyr, the quiescent population has grown more slowly in number density at high masses ({M}_\ast >10^{11}{M_{s}) than at intermediate masses ({M}_\ast >10^{10.6}{M_{s}). There is evolution in both the PSB and green-valley stellar mass functions, consistent with higher mass galaxies quenching at earlier cosmic times. At intermediate masses ({M}_\ast >10^{10.6}{M_{s}), 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_{s}), 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.
63 citations
TL;DR: In this article, the authors present gas-phase metallicity and ionization parameter maps of 25 star-forming face-on spiral galaxies from the SAMI Galaxy Survey Data Release 1.
Abstract: We present gas-phase metallicity and ionization parameter maps of 25 star-forming face-on spiral galaxies from the SAMI Galaxy Survey Data Release 1. Self-consistent metallicity and ionization parameter maps are calculated simultaneously through an iterative process to account for the interdependence of the strong emission line diagnostics involving ([O II]+[O III])/Hβ (R_(23)) and [O III]/[O II](O32). The maps are created on a spaxel-by-spaxel basis because H II regions are not resolved at the SAMI spatial resolution. We combine the SAMI data with stellar mass, star formation rate (SFR), effective radius (R_e), ellipticity, and position angles (PA) from the GAMA survey to analyse their relation to the metallicity and ionization parameter. We find a weak trend of steepening metallicity gradient with galaxy stellar mass, with values ranging from −0.03 to −0.20 dex/R_e. Only two galaxies show radial gradients in the ionization parameter. We find that the ionization parameter has no significant correlation with either SFR, sSFR (specific SFR), or metallicity. For several individual galaxies, we find the structure in the ionization parameter maps suggestive of spiral arm features. We find a typical ionization parameter range of 7.0 < log (q) < 7.8 for our galaxy sample with no significant overall structure. An ionization parameter range of this magnitude is large enough to caution the use of metallicity diagnostics that have not considered the effects of a varying ionization parameter distribution.
62 citations
TL;DR: In this paper, a combined study of spatially resolved stellar kinematics and global stellar populations was performed using the SAMI Galaxy Survey, and the authors found a strong correlation of stellar population age with location in the (V/σ, $${\boldsymbol{\epsilon}}{{{b}e}}}$$¯¯ ϵ¯¯¯¯ e¯¯¯¯ ) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity.
Abstract: Stellar population and stellar kinematic studies provide unique but complementary insights into how galaxies build-up their stellar mass and angular momentum1–3. A galaxy’s mean stellar age reveals when stars were formed, but provides little constraint on how the galaxy’s mass was assembled. Resolved stellar dynamics
4
trace the change in angular momentum due to mergers, but major mergers tend to obscure the effect of earlier interactions
5
. With the rise of large multi-object integral field spectroscopic surveys, such as SAMI
6
and MaNGA
7
, and single-object integral field spectroscopic surveys (for example, ATLAS3D (ref. 8
), CALIFA
9
, MASSIVE
10
), it is now feasible to connect a galaxy′s star formation and merger history on the same resolved physical scales, over a large range in galaxy mass, morphology and environment4,11,12. Using the SAMI Galaxy Survey, here we present a combined study of spatially resolved stellar kinematics and global stellar populations. We find a strong correlation of stellar population age with location in the (V/σ, $${\boldsymbol{\epsilon}}_{{\boldsymbol{e}}}$$
ϵ
e
) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity. For the large majority of galaxies that are oblate rotating spheroids, we find that characteristic stellar age follows the intrinsic ellipticity of galaxies remarkably well.
53 citations
TL;DR: In this article, the authors present the first study of spatially-resolved stellar kinematics and global stellar populations in a large IFS galaxy survey, and find a strong correlation of stellar population age with location in the ($V / \sigma$, $\epsilon_{\rm{e}}$) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity.
Abstract: Stellar population and stellar kinematic studies provide unique but complementary insights into how galaxies build-up their stellar mass and angular momentum. A galaxy's mean stellar age reveals when stars were formed, but provides little constraint on how the galaxy's mass was assembled. Resolved stellar dynamics trace the change in angular momentum and orbital distribution of stars due to mergers, but major mergers tend to obscure the effect of earlier interactions. With the rise of large multi-object integral field spectroscopic (IFS) surveys, such as SAMI and MaNGA, and single-object IFS surveys (e.g., ATLAS$^{\rm{3D}}$, CALIFA, MASSIVE), it is now feasible to connect a galaxy's star formation and merger history on the same resolved physical scales, over a large range in galaxy mass, and across the full range of optical morphology and environment. Using the SAMI Galaxy Survey, here we present the first study of spatially-resolved stellar kinematics and global stellar populations in a large IFS galaxy survey. We find a strong correlation of stellar population age with location in the ($V / \sigma$, $\epsilon_{\rm{e}}$) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity. For the large majority of galaxies that are oblate rotating spheroids, we find that characteristic stellar age follows the intrinsic ellipticity of galaxies remarkably well. This trend is still observed when galaxies are separated into early-type and late-type samples.
TL;DR: In this article, the authors used the Galaxy And Mass Assembly survey to explore how the dispersion along the sSFR-M$*}$ relation varies with SFR indicator for a variety of selections for disc-like ''main sequence'' star-forming galaxies including colour, star-formation rate, visual morphology, bulge-to-total mass ratio, Sersic index and mixture modelling.
Abstract: Recently a number of studies have proposed that the dispersion along the star formation rate - stellar mass relation ($\sigma_{\mathrm{sSFR}}$-M$_{*}$) is indicative of variations in star-formation history (SFH) driven by feedback processes. They found a 'U'-shaped dispersion and attribute the increased scatter at low and high stellar masses to stellar and active galactic nuclei feed-back respectively. However, measuring $\sigma_{\mathrm{sSFR}}$ and the shape of the $\sigma_{\mathrm{sSFR}}$-M$_{*}$ relation is problematic and can vary dramatically depending on the sample selected, chosen separation of passive/star-forming systems, and method of deriving star-formation rates ($i.e.$ H$\alpha$ emission vs spectral energy distribution fitting). As such, any astrophysical conclusions drawn from measurements of $\sigma_{\mathrm{sSFR}}$ must consider these dependencies. Here we use the Galaxy And Mass Assembly survey to explore how $\sigma_{\mathrm{sSFR}}$ varies with SFR indicator for a variety of selections for disc-like `main sequence' star-forming galaxies including colour, star-formation rate, visual morphology, bulge-to-total mass ratio, Sersic index and mixture modelling. We find that irrespective of sample selection and/or SFR indicator, the dispersion along the sSFR-M$_{*}$ relation does follow a 'U'-shaped distribution. This suggests that the shape is physical and not an artefact of sample selection or method. We then compare the $\sigma_{\mathrm{sSFR}}$-M$_{*}$ relation to state-of-the-art hydrodynamical and semi-analytic models and find good agreement with our observed results. Finally, we find that for group satellites this 'U'-shaped distribution is not observed due to additional high scatter populations at intermediate stellar masses.
TL;DR: In this paper, the authors explore how the group environment may affect the evolution of star-forming galaxies and find that the fraction of starforming group members is higher in the PPS regions dominated by recently accreted galaxies, whereas passive galaxies dominate the virialized regions.
Abstract: We explore how the group environment may affect the evolution of star-forming galaxies. We select 1197 Galaxy And Mass Assembly (GAMA) 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 10 12 ≤(M200/M⊙)<10^14. 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 towards 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.
INAF1, University of Geneva2, Australian Astronomical Observatory3, Université Paris-Saclay4, University of Bonn5, National Academy of Sciences of Ukraine6, University of Bologna7, Aristotle University of Thessaloniki8, Aix-Marseille University9, Istanbul University10, Liverpool John Moores University11, Monash University12, University of St Andrews13, University of Nottingham14, Max Planck Society15, University of Hamburg16, University of Nice Sophia Antipolis17, University of Zagreb18, Macquarie University19, University of Toulouse20, European Southern Observatory21, University of Birmingham22, University of Oxford23
TL;DR: In this paper, the authors present the version of the point source catalogue of the XXL Survey that was used, in part, in the first series of XXL papers, and present the basic properties of the X-ray point sources and their counterparts.
Abstract: We present the version of the point source catalogue of the XXL Survey that was used, in part, in the first series of XXL papers. In this paper we release, in our database in Milan and at CDS: (i) the X-ray source catalogue with 26 056 objects in two areas of 25 deg2 with a flux limit (at 3σ) of ~10−15 erg s−1 cm−2 in [0.5–2] keV, and ~ 3 × 10−15 erg s−1 cm−2 in [2–10] keV, yielding a 90% completeness limit of 5.8 × 10−15 and 3.8 × 10−14 respectively;(ii) the associated multiwavelength catalogues with candidate counterparts of the X-ray sources in the infrared, near-infrared, optical, and ultraviolet (plus spectroscopic redshift when available); and (iii) a catalogue of spectroscopic redshifts recently obtained in the southern XXL area. We also present the basic properties of the X-ray point sources and their counterparts. Other catalogues described in the second series of XXL papers will be released contextually, and will constitute the second XXLdata release.
TL;DR: In this article, the authors used the semi-analytic galaxy formation model SAGE to model the triggering of active galactic nuclei in galaxy clusters using the ram pressure galaxies experience as they move throughout the intracluster medium, which is hypothesized to trigger star formation and AGN activity.
Abstract: We model the triggering of active galactic nuclei (AGN) in galaxy clusters using the semi-analytic galaxy formation model SAGE. We prescribe triggering methods based on the ram pressure galaxies experience as they move throughout the intracluster medium, which is hypothesized to trigger star formation and AGN activity. The clustercentric radius and velocity distribution of the simulated active galaxies produced by these models are compared with those of AGN and galaxies with intense star formation from a sample of low-redshift relaxed clusters from the Sloan Digital Sky Survey. The ram pressure triggering model that best explains the clustercentric radius and velocity distribution of these observed galaxies has AGN and star formation triggered if 2.5 × 10 −14 Pa P ram −13 Pa and P ram > 2 P internal ; this is consistent with expectations from hydrodynamical simulations of ram-pressure-induced star formation. Our results show that ram pressure is likely to be an important mechanism for triggering star formation and AGN activity in clusters.
TL;DR: In this article, the authors show that a reduced number of low-speed interactions, ram pressure stripping and intra-group/cluster medium temperature, the dominance of which increase with halo mass, work to inhibit AGN in the cores of groups and clusters with log 10 (M 200 /M ⊙ )>13.5, but do not significantly affect nuclear activity in cores of less massive structures.
Abstract: In galaxy clusters, efficiently accreting active galactic nuclei (AGN) 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, virialised, cluster core. Exploiting the depth and completeness (98 per cent at r 9.9 in 695 groups with 11.53≤log 10 (M 200 /M ⊙ )≤14.56 at z 13.5 , AGN are preferentially found in the infalling galaxy population with 3.6σ confidence. At lower halo masses we observe no difference in AGN fraction between core and infalling galaxies. These observations support a model where a reduced number of low-speed interactions, ram pressure stripping and intra-group/cluster medium temperature, the dominance of which increase with halo mass, work to inhibit AGN in the cores of groups and clusters with log 10 (M 200 /M ⊙ )>13.5 , but do not significantly affect nuclear activity in cores of less massive structures.
TL;DR: For early-type galaxies, the authors found that the color and stellar metallicity [Z/H] correlate more strongly with gravitational potential than with mass $M$, whereas stellar population age correlates best with surface density $Sigma.
Abstract: The well-established correlations between the mass of a galaxy and the properties of its stars are considered evidence for mass driving the evolution of the stellar population. However, for early-type galaxies (ETGs), we find that $g-i$ color and stellar metallicity [Z/H] correlate more strongly with gravitational potential $\Phi$ than with mass $M$, whereas stellar population age correlates best with surface density $\Sigma$. Specifically, for our sample of 625 ETGs with integral-field spectroscopy from the SAMI Galaxy Survey, compared to correlations with mass, the color--$\Phi$, [Z/H]--$\Phi$, and age--$\Sigma$ relations show both smaller scatter and less residual trend with galaxy size. For the star formation duration proxy [$\alpha$/Fe], we find comparable results for trends with $\Phi$ and $\Sigma$, with both being significantly stronger than the [$\alpha$/Fe]-$M$ relation. In determining the strength of a trend, we analyze both the overall scatter, and the observational uncertainty on the parameters, in order to compare the intrinsic scatter in each correlation. These results lead us to the following inferences and interpretations: (1) the color--$\Phi$ diagram is a more precise tool for determining the developmental stage of the stellar population than the conventional color--mass diagram; and (2) gravitational potential is the primary regulator of global stellar metallicity, via its relation to the gas escape velocity. Furthermore, we propose the following two mechanisms for the age and [$\alpha$/Fe] relations with $\Sigma$: (a) the age--$\Sigma$ and [$\alpha$/Fe]--$\Sigma$ correlations arise as results of compactness driven quenching mechanisms; and/or (b) as fossil records of the $\Sigma_{SFR}\propto\Sigma_{gas}$ relation in their disk-dominated progenitors.
INAF1, University of Padua2, University of Melbourne3, University of Geneva4, Université Paris-Saclay5, University of Bonn6, University of Bristol7, University of Birmingham8, Liverpool John Moores University9, Monash University10, University of St Andrews11, University of Western Australia12, University of Bologna13, University of Michigan14, European Space Research and Technology Centre15, University of KwaZulu-Natal16, Australian Astronomical Observatory17, Chalmers University of Technology18, University of Hamburg19, University of Nice Sophia Antipolis20, Macquarie University21, Aristotle University of Thessaloniki22, Academy of Sciences of Uzbekistan23, University of Zagreb24, University of Victoria25
TL;DR: In this article, a complete spectrophotometric sample of galaxies within X-ray detected, optically spectroscopically confirmed groups and clusters (G&C) covering a wide range of halo masses at z ≤ 0.6 was built.
Abstract: Context. The fraction of galaxies bound in groups in the nearby Universe is high (50% at z ∼ 0). Systematic studies of galaxy properties in groups are important in order to improve our understanding of the evolution of galaxies and of the physical phenomena occurring within this environment. Aims. We have built a complete spectrophotometric sample of galaxies within X-ray detected, optically spectroscopically confirmed groups and clusters (G&C), covering a wide range of halo masses at z ≤ 0.6. Methods. In the context of the XXL survey, we analyse a sample of 164 G&C in the XXL-North region (XXL-N), at z ≤ 0.6, with a wide range of virial masses (1.24 × 1013 ≤ M500,scal(Mo) ≤ 6.63 × 1014) and X-ray luminosities ((2.27 × 1041 ≤ L500,scalXXL(erg-s-1) ≤ 2.15 × 1044)). The G&C are X-ray selected and spectroscopically confirmed. We describe the membership assignment and the spectroscopic completeness analysis, and compute stellar masses. As a first scientific exploitation of the sample, we study the dependence of the galaxy stellar mass function (GSMF) on global environment. Results. We present a spectrophotometric characterisation of the G&C and their galaxies. The final sample contains 132 G&C, 22 111 field galaxies and 2225 G&C galaxies with r-band magnitude <20. Of the G&C, 95% have at least three spectroscopic members, and 70% at least ten. The shape of the GSMF seems not to depend on environment (field versus G&C) or X-ray luminosity (used as a proxy for the virial mass of the system). These results are confirmed by the study of the correlation between mean stellar mass of G&C members and L500,scalXXL. We release the spectrophotometric catalogue of galaxies with all the quantities computed in this work. Conclusions. As a first homogeneous census of galaxies within X-ray spectroscopically confirmed G&C at these redshifts, this sample will allow environmental studies of the evolution of galaxy properties.
TL;DR: For early-type galaxies, this article found that g − i color and stellar metallicity [Z/H] correlate more strongly with gravitational potential Φ than with mass M, whereas SP age correlates best with surface density Σ.
Abstract: The well-established correlations between the mass of a galaxy and the properties of its stars are considered to be evidence for mass driving the evolution of the stellar population (SP). However, for early-type galaxies (ETGs), we find that g − i color and stellar metallicity [Z/H] correlate more strongly with gravitational potential Φ than with mass M, whereas SP age correlates best with surface density Σ. Specifically, for our sample of 625 ETGs with integral-field spectroscopy from the Sydney-AAO Multi-object Integral-field Galaxy Survey, compared to correlations with mass, the color–Φ, [Z/H]–Φ, and age–Σ relations show both a smaller scatter and a lower residual trend with galaxy size. For the star formation duration proxy [α/Fe], we find comparable results for trends with Φ and Σ, with both being significantly stronger than the [α/Fe]–M relation. In determining the strength of a trend, we analyze both the overall scatter, and the observational uncertainty on the parameters, in order to compare the intrinsic scatter in each correlation. These results lead us to the following inferences and interpretations: (1) the color–Φ diagram is a more precise tool for determining the developmental stage of the SP than the conventional color–mass diagram; and (2) gravitational potential is the primary regulator of global stellar metallicity, via its relation to the gas escape velocity. Furthermore, we propose the following two mechanisms for the age and [α/Fe] relations with Σ: (a) the age–Σ and [α/Fe]–Σ correlations arise as results of compactness-driven quenching mechanisms; and/or (b) as fossil records of the Σ_(SFR) ∝ Σ_(gas) relation in their disk-dominated progenitors.
University of Queensland1, University of Western Australia2, University of St Andrews3, Australian Astronomical Observatory4, Swinburne University of Technology5, University of New South Wales6, Monash University, Clayton campus7, University of Louisville8, Macquarie University9, University of Hull10
TL;DR: In this article, the authors test if nearby blue spheroid (BSph) galaxies may become the progenitors of star-forming spiral galaxies or passively evolving elliptical galaxies.
Abstract: 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 < z < 0.02 (8-87 Mpc) 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 H-1 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 ass red galaxies.
University of Sydney1, Australian Astronomical Observatory2, University of New South Wales3, Commonwealth Scientific and Industrial Research Organisation4, University of Western Australia5, Australian National University6, Swinburne University of Technology7, California Institute of Technology8, Macquarie University9
TL;DR: In this article, the authors used spatially resolved Hα velocity fields from the SAMI Galaxy Survey to quantify kinematic asymmetry in nearby galaxies and environmental and stellar mass data from the Galaxy And Mass Assembly survey.
Abstract: In order to determine the causes of kinematic asymmetry in the Hα gas in the SAMI (Sydney–AAO Multi-object IFS) Galaxy Survey sample, we investigate the comparative influences of environment and intrinsic properties of galaxies on perturbation. We use spatially resolved Hα velocity fields from the SAMI Galaxy Survey to quantify kinematic asymmetry (ν_(asym)) in nearby galaxies and environmental and stellar mass data from the Galaxy And Mass Assembly survey. We find that local environment, measured as distance to nearest neighbour, is inversely correlated with kinematic asymmetry for galaxies with log (M*/M⊙) > 10.0, but there is no significant correlation for galaxies with log (M*/M⊙) < 10.0. Moreover, low-mass galaxies [log (M*/M⊙) < 9.0] have greater kinematic asymmetry at all separations, suggesting a different physical source of asymmetry is important in low-mass galaxies. We propose that secular effects derived from gas fraction and gas mass may be the primary causes of asymmetry in low-mass galaxies. High gas fraction is linked to high σm/V (where σm is Hα velocity dispersion and V the rotation velocity), which is strongly correlated with (ν_(asym)), and galaxies with log (M*/M⊙) < 9.0 have offset σm/V from the rest of the sample. Further, asymmetry as a fraction of dispersion decreases for galaxies with log (M*/M⊙) < 9.0. Gas mass and asymmetry are also inversely correlated in our sample. We propose that low gas masses in dwarf galaxies may lead to asymmetric distribution of gas clouds, leading to increased relative turbulence.
University of Michigan1, INAF2, University of Padua3, Aix-Marseille University4, University of Bristol5, University of Colorado Boulder6, Ames Research Center7, University of Bologna8, Liverpool John Moores University9, Monash University10, University of Western Australia11, University of St Andrews12, National Academy of Sciences of Ukraine13, University of KwaZulu-Natal14, Australian Astronomical Observatory15, Université Paris-Saclay16, University of Hamburg17, University of Nice Sophia Antipolis18, Macquarie University19, University of Bonn20, Aristotle University of Thessaloniki21, National Institute of Astrophysics, Optics and Electronics22, University of Birmingham23, Academy of Sciences of Uzbekistan24, Paris Diderot University25, Max Planck Society26
TL;DR: In this paper, the scaling of the kinetic energy of galaxies with hot gas temperature was determined by combining spectroscopic and X-ray observations in one field, and by imposing prior constraints on the relative energies of galaxies and dark matter, infer a power-law scaling of total mass with temperature.
Abstract: Context. An X-ray survey with the XMM-Newton telescope, XMM-XXL, has identified hundreds of galaxy groups and clusters in two 25 deg2 fields. Combining spectroscopic and X-ray observations in one field, we determine how the kinetic energy of galaxies scales with hot gas temperature and also, by imposing prior constraints on the relative energies of galaxies and dark matter, infer a power-law scaling of total mass with temperature.
Aims. Our goals are: i) to determine parameters of the scaling between galaxy velocity dispersion and X-ray temperature, T300 kpc, for the halos hosting XXL-selected clusters, and; ii) to infer the log-mean scaling of total halo mass with temperature, ⟨lnM200 | T300 kpc, z⟩.
Methods. We applied an ensemble velocity likelihood to a sample of >1500 spectroscopic redshifts within 132 spectroscopically confirmed clusters with redshifts z < 0.6 to model, ⟨lnσgal | T300 kpc, z⟩, where σgal is the velocity dispersion of XXL cluster member galaxies and T300 kpc is a 300 kpc aperture temperature. To infer total halo mass we used a precise virial relation for massive halos calibrated by N-body simulations along with a single degree of freedom summarising galaxy velocity bias with respect to dark matter.
Results. For the XXL-N cluster sample, we find σgal ∝ T300 kpc0.63±0.05, a slope significantly steeper than the self-similar expectation of 0.5. Assuming scale-independent galaxy velocity bias, we infer a mean logarithmic mass at a given X-ray temperature and redshift, 〈ln(E(z)M200/1014 M⊙)|T300 kpc, z〉 = πT + αT ln (T300 kpc/Tp) + βT ln (E(z)/E(zp)) using pivot values kTp = 2.2 keV and zp = 0.25, with normalization πT = 0.45 ± 0.24 and slope αT = 1.89 ± 0.15. We obtain only weak constraints on redshift evolution, βT = −1.29 ± 1.14.
Conclusions. The ratio of specific energies in hot gas and galaxies is scale dependent. Ensemble spectroscopic analysis is a viable method to infer mean scaling relations, particularly for the numerous low mass systems with small numbers of spectroscopic members per system. Galaxy velocity bias is the dominant systematic uncertainty in dynamical mass estimates.
Aix-Marseille University1, Max Planck Society2, INAF3, University of Melbourne4, National Autonomous University of Mexico5, Universidad de Guanajuato6, University of Bristol7, Université Paris-Saclay8, University of Bonn9, Liverpool John Moores University10, Monash University11, University of St Andrews12, University of Bologna13, University of Michigan14, European Space Research and Technology Centre15, University of KwaZulu-Natal16, Australian Astronomical Observatory17, Chalmers University of Technology18, Macquarie University19, University of Geneva20, Aristotle University of Thessaloniki21, University of Birmingham22, Academy of Sciences of Uzbekistan23, University of Zagreb24
TL;DR: In this article, the stellar populations of galaxies in different environments in the supercluster region were investigated, and a magnitude-limited (r ≤ 20) and a mass-limited sample (log(M ∗ Mo) ≥ 10.8) was obtained.
Abstract: Context. Superclusters form from the largest enhancements in the primordial density perturbation field and extend for tens of Mpc, tracing the large-scale structure of the Universe. X-ray detections and systematic characterisations of superclusters and the properties of their galaxies have only been possible in the last few years. Aims. We characterise XLSSsC N01, a rich supercluster at z ∼ 0.3 detected in the XXL Survey, composed of X-ray clusters of different virial masses and X-ray luminosities. As one of the first studies on this topic, we investigate the stellar populations of galaxies in different environments in the supercluster region. Methods. We study a magnitude-limited (r ≤ 20) and a mass-limited sample (log(M ∗ Mo) ≥ 10.8) of galaxies in the virialised region and in the outskirts of 11 XLSSsC N01 clusters, in high-density field regions, and in the low-density field. We compute the stellar population properties of galaxies using spectral energy distribution (SED) and spectral fitting techniques, and study the dependence of star formation rates (SFR), colours, and stellar ages on environment. Results. For r ≤ 20, the fraction of star-forming/blue galaxies, computed either from the specific-SFR (sSFR) or rest-frame colour, shows depletion within the cluster virial radii, where the number of galaxies with log (sSFR/ yr-1) > -12 and with (g - r) restframe < 0.6 is lower than in the field. For log(M ∗ Mo) ≥ 10.8, no trends with environment emerge, as massive galaxies are mostly already passive in all environments. No differences among low- and high-density field members and cluster members emerge in the sSFR-mass relation in the mass-complete regime. Finally, the luminosity-weighted age-mass relation of the passive populations within cluster virial radii show signatures of recent environmental quenching. Conclusions. The study of luminous and massive galaxies in this supercluster shows that while environment has a prominent role in determining the fractions of star-forming/blue galaxies, its effects on the star formation activity in star-forming galaxies are negligible.
Leiden University1, Pontifical Catholic University of Chile2, Durham University3, Case Western Reserve University4, Max Planck Society5, University of Sussex6, Australian Astronomical Observatory7, University of Western Australia8, University of Groningen9, Netherlands Institute for Space Research10, Ames Research Center11, University of Sydney12, University of New South Wales13, University of Louisville14, Macquarie University15, University of Bonn16
TL;DR: In this paper, the authors used 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.
Abstract: 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 H α star formers, drawn from the highly spatially complete Galaxy And Mass Assembly (GAMA) survey, show an increase in clustering at small separations. Moreover, the clustering strength shows a strong dependence on optical brightness and stellar mass, where (1) the clustering amplitude of optically brighter galaxies at a given separation is larger than that of optically fainter systems, (2) the small-scale-clustering properties (e.g. the strength, the scale at which the signal relative to the fiducial power law plateaus) of star-forming galaxies appear to differ as a function of increasing optical brightness of galaxies. According to cross- and mark-correlation analyses, the former result is largely driven by the increased dust content in optically bright star-forming galaxies. The latter could be interpreted as evidence of a correlation between interaction-scale and optical brightness of galaxies, where physical evidence of interactions between optically bright star formers, likely hosted within relatively massive haloes, persists over larger separations than those between optically faint star formers.
TL;DR: In this article, the balance in dynamical support of 384 galaxies with stellar kinematics out to > 1.5R_e in the Sydney AAO Multi-object Integral Field (SAMI) Galaxy Survey was studied.
Abstract: We study the balance in dynamical support of 384 galaxies with stellar kinematics out to >1.5R_e in the Sydney AAO Multi-object Integral Field (SAMI) Galaxy Survey. We present radial dynamical profiles of the local rotation dominance parameter, V/sigma, and local spin, lambda_loc. Although there is a broad range in amplitude, most kinematic profiles monotonically increase across the probed radial range. We do not find many galaxies with kinematic transitions such as those expected between the inner in-situ and outer accreted stars within the radial range probed. We compare the V/sigma gradient and maximum values to the visual morphologies of the galaxies to better understand the link between visual and kinematic morphologies. We find that the radial distribution of dynamical support in galaxies is linked to their visual morphology. Late-type systems have higher rotational support at all radii and steeper V/sigma gradients compared to early-type galaxies. We perform a search for embedded discs, which are rotationally supported discy structures embedded within large scale slowly or non-rotating structures. Visual inspection of the kinematics reveals at most three galaxies (out of 384) harbouring embedded discs. This is more than an order of magnitude fewer than the observed fraction in some local studies. Our tests suggest that this tension can be attributed to differences in the sample selection, spatial sampling and beam smearing due to seeing.
TL;DR: In this paper, the authors explore how the group environment may affect the evolution of star-forming galaxies and find that the fraction of starforming group members is higher in the PPS regions dominated by recently accreted galaxies, whereas passive galaxies dominate the virialized regions.
Abstract: We explore how the group environment may affect the evolution of star-forming galaxies. We select 1197 Galaxy And Mass Assembly (GAMA) groups at $0.05\leq z \leq 0.2$ 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 $10^{12}\leq (M_{200}/M_{\odot})< 10^{14}$. 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 towards the group center by a factor $\sim 1.2$ 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.
INAF1, Max Planck Society2, Aix-Marseille University3, University of Melbourne4, National Autonomous University of Mexico5, Universidad de Guanajuato6, University of Bristol7, Université Paris-Saclay8, University of Bonn9, Liverpool John Moores University10, Monash University11, University of St Andrews12, University of Bologna13, University of Michigan14, European Space Research and Technology Centre15, University of KwaZulu-Natal16, Australian Astronomical Observatory17, Chalmers University of Technology18, Macquarie University19, University of Geneva20, Aristotle University of Thessaloniki21, University of Birmingham22, Academy of Sciences of Uzbekistan23, University of Zagreb24
TL;DR: In this paper, the stellar populations of galaxies in different environments in the supercluster region were investigated, and the luminosity-weighted age-mass relation of the passive populations within cluster virial radii showed signatures of recent environmental quenching.
Abstract: Superclusters form from the largest enhancements in the primordial density perturbation field and extend for tens of Mpc, tracing the large-scale structure of the Universe. We characterise XLSSsCN01, a rich supercluster at z~0.3 detected in the XXL Survey, composed of X-ray clusters of different virial masses and luminosities. As one of the first studies on this topic, we investigate the stellar populations of galaxies in different environments in the supercluster region. We study a magnitude-limited (r 10.8) of galaxies in the virialised region and in the outskirts of 11 XLSSsCN01 clusters, in high- and low-density field. We compute the stellar population properties of galaxies using spectral energy distribution and spectral fitting techniques, and study the dependence of star formation rates (SFR), colours, and stellar ages on environment. For r -12 and with (g-r)_rf 10.8, no trends with environment emerge, as massive galaxies are mostly already passive in all environments. No differences among low- and high-density field members and cluster members emerge in the sSFR-mass relation. The luminosity-weighted age-mass relation of the passive populations within cluster virial radii show signatures of recent environmental quenching. The study of luminous and massive galaxies in this supercluster shows that while environment has a prominent role in determining the fractions of SFing/blue galaxies, its effects on the star formation activity in SFing galaxies are negligible.
INAF1, University of Geneva2, Australian Astronomical Observatory3, Université Paris-Saclay4, University of Bonn5, National Academy of Sciences of Ukraine6, University of Bologna7, Aristotle University of Thessaloniki8, Aix-Marseille University9, Istanbul University10, Liverpool John Moores University11, Monash University12, University of St Andrews13, University of Nottingham14, Max Planck Society15, University of Hamburg16, University of Nice Sophia Antipolis17, University of Zagreb18, Macquarie University19, University of Toulouse20, European Southern Observatory21, University of Birmingham22, University of Oxford23
TL;DR: In this article, the authors present the version of the point source catalogue of the XXL Survey that was used, in part, in the first series of XXL papers. And they also present the basic properties of the X-ray point sources and their counterparts.
Abstract: We present the version of the point source catalogue of the XXL Survey that was used, in part, in the first series of XXL papers. In this paper we release, in our database in Milan and at CDS: (i) the X-ray source catalogue with 26056 objects in two areas of 25 deg2; (ii) the associated multiwavelength catalogues with candidate counterparts of the X-ray sources in the infrared, near-infrared, optical, and ultraviolet (plus spectroscopic redshift when available); and (iii) a catalogue of spectroscopic redshifts recently obtained in the southern XXL area. We also present the basic properties of the X-ray point sources and their counterparts. Other catalogues described in the second series of XXL papers will be released contextually, and will constitute the second XXL data release.