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We analyze how passive galaxies at z $\sim$ 1.5 populate the mass-size plane as a function of their stellar age, to understand if the observed size growth with time can be explained with the appearance of larger quenched galaxies at lower redshift. We use a sample of 32 passive galaxies extracted from the Wide Field Camera 3 Infrared Spectroscopic Parallel (WISP) survey with spectroscopic redshift 1.3 $\lesssim$ z $\lesssim$ 2.05, specific star-formation rates lower than 0.01 Gyr$^{-1}$, and stellar masses above 4.5 $\times$ 10$^{10}$ M$_\odot$. All galaxies have spectrally determined stellar ages from fitting of their rest-frame optical spectra and photometry with stellar population models. When dividing our sample into young (age $\leq$ 2.1 Gyr) and old (age $>$ 2.1 Gyr) galaxies we do not find a significant trend in the distributions of the difference between the observed radius and the one predicted by the mass-size relation. This result indicates that the relation between the galaxy age and its distance from the mass-size relation, if it exists, is rather shallow, with a slope alpha $\gtrsim$ -0.6. At face value, this finding suggests that multiple dry and/or wet minor mergers, rather than the appearance of newly quenched galaxies, are mainly responsible for the observed time evolution of the mass-size relation in passive galaxies., Comment: Accepted for publication in ApJ Letters; 6 pages, 3 figures, 1 table

We present results from near-infrared spectroscopy of 26 emission-line galaxies at z ~ 2 obtained with the FIRE spectrometer on the Magellan Baade telescope. The sample was selected from the WISP survey, which uses the near-infrared grism of the Hubble Space Telescope Wide Field Camera 3 to detect emission-line galaxies over 0.3 < z < 2.3. Our FIRE follow-up spectroscopy (R~5000) over 1.0-2.5 micron permits detailed measurements of physical properties of the z~2 emission-line galaxies. Dust-corrected star formation rates for the sample range from ~5-100 M_sun yr-1. We derive a median metallicity for the sample of ~0.45 Z_sun, and the estimated stellar masses range from ~10^8.5 - 10^9.5 M_sun. The average ionization parameters measured for the sample are typically much higher than what is found for local star-forming galaxies. We derive composite spectra from the FIRE sample, from which we infer typical nebular electron densities of ~100-400 cm^-3. Based on the location of the galaxies and composite spectra on BPT diagrams, we do not find evidence for significant AGN activity in the sample. Most of the galaxies as well as the composites are offset in the BPT diagram toward higher [O III]/H-beta at a given [N II]/H-alpha, in agreement with other observations of z > 1 star-forming galaxies, but composite spectra derived from the sample do not show an appreciable offset from the local star-forming sequence on the [O III]/H-beta versus [S II]/H-alpha diagram. We infer a high nitrogen-to-oxygen abundance ratio from the composite spectrum, which may contribute to the offset of the high-redshift galaxies from the local star-forming sequence in the [O III]/H-beta versus [N II]/H-alpha diagram. We speculate that the elevated nitrogen abundance could result from substantial numbers of Wolf-Rayet stars in starbursting galaxies at z~2. (Abridged), Comment: Accepted for publication in ApJ

We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10^{8}< M/M_{\sun} < 10^{10}, obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 < z < 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R23 metallicity diagnostic: ([OII]3726,3729 + [OIII] 4959,5007)/H\beta. Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M=10^{9.8} M_{\sun} to 12+log(O/H)= 8.2 at M=10^{8.2} M_{\sun}. After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M>10^{9.5} M_{\sun} and z~2.3. Within the statistical uncertainties, our MZ relation agrees with the z~2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift z=1.76 of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M_{*} relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high SFRs. Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation., Comment: Accepted for publication in ApJ Letters

We combine Hubble Space Telescope (HST) G102 & G141 NIR grism spectroscopy with HST/WFC3-UVIS, HST/WFC3-IR and Spitzer/IRAC[3.6\mu m] photometry to assemble a sample of massive (log(M_star/M_sun) ~ 11) and quenched galaxies at z~1.5. Our sample of 41 galaxies is the largest with G102+G141 NIR spectroscopy for quenched sources at these redshifts. In contrast to the local Universe, z~1.5 quenched galaxies in the high-mass range have a wide range of stellar population properties. We find their SEDs are well fitted with exponentially decreasing SFHs, and short star-formation time-scales (\tau<100Myr). Quenched galaxies also show a wide distribution in ages, between 1-4Gyr. In the (u-r)_0-versus-mass space quenched galaxies have a large spread in rest-frame color at a given mass. Most quenched galaxies populate the z~1.5 red-sequence (RS), but an important fraction of them (32%) have substantially bluer colors. Although with a large spread, we find that the quenched galaxies ON the RS have older median ages (3.1Gyr) than the quenched galaxies OFF the RS (1.5Gyr). We also show that a rejuvenated SED cannot reproduce the observed stacked spectra of (the bluer) quenched galaxies OFF the RS. We derive the upper limit on the fraction of massive galaxies ON the RS at z~1.5 to be <43%. We speculate that the young quenched galaxies OFF the RS are in a transition phase between vigorous star formation at z>2 and the z~1.5 RS. According to their estimated ages, the time required for quenched galaxies OFF the RS to join their counterparts ON the z~1.5 RS is of the order of ~1Gyr., Comment: 15 pages, 11 figures and appendix. Accepted for publication in ApJ

Lenticular galaxies have long been thought of as evolved spirals, but the processes involved to quench the star formation are still unclear. By studying the individual star formation histories of the bulges and disks of lenticulars, it is possible to look for clues to the processes that triggered their transformation from spirals. To accomplish this feat, we present a new method for spectroscopic bulge-disk decomposition, in which a long-slit spectrum is decomposed into two one-dimensional spectra representing purely the bulge and disk light. We present preliminary results from applying this method to lenticular galaxies in the Virgo and Fornax Clusters, in which we show that the most recent star formation activity in these galaxies occurred within the bulges. We also find that the bulges are in general more Fe-enriched than the disks of the same galaxy, and that this enrichment grows stronger as the age of the bulge becomes younger. These results point towards a scenario where the star formation in the disks of spiral galaxies are quenched, followed by a burst of star formation in the central regions from the gas that has been funnelled inwards through the disk., Comment: 4 pages, 2 figures, To appear in the conference proceedings of The Structure and Dynamics of Disk Galaxies, M.S. Seigar and P. Treuthardt, eds

There is cumulative evidence showing that, for the most massive galaxies, the fraction of disk-like objects compared to those with spheroidal properties increases with redshift. However, this evolution is thus far based on the surface brightness study of these objects. To explore the consistency of this scenario, it is necessary to measure the dynamical status of these galaxies. With this aim we have obtained seeing-limited near-infrared integral field spectra in the H-band for 10 massive galaxies (M_{stellar} >10^{11} h_{70}^-2 M_{Sun}) at z~1.4 with SINFONI at the VLT. Our sample is selected by their stellar mass and EW[OII] > 15 \AA, to secure their kinematic measurements, but without accounting for any morphological or flux criteria a priori. Through this 3D kinematic spectroscopy analysis we find that half (i.e. 50+/-7%) of our galaxies are compatible with being rotationally supported disks, in agreement with previous morphological expectations. This is a factor of approximately two higher than what is observed in the present Universe for objects of the same stellar mass. Strikingly, the majority of our sample of massive galaxies show extended and fairly high rotational velocity maps, implying that massive galaxies acquire rapidly rotational support and hence gravitational equilibrium. Our sample also show evidence for ongoing interactions and mergers. Summarizing, massive galaxies at high-z show a significant diversity and must have continued evolution beyond the fading of stellar populations, to become their present day counterparts., Comment: 31 pages, 23 figures, 4 tables. Accepted for publication in MNRAS. Some changes performed to match the journal version

We present an atlas of a sample of local (U)LIRGs covering the luminosity range log(L_IR/L_sun)=11.1-12.4. The atlas is based on near-infrared H and K-band VLT-SINFONI IFS, and presents the ionised, partially ionised, and warm molecular gas 2D flux distributions and kinematics over a FoV of 3x3 kpc (LIRGs) and 12x12kpc (ULIRGs) and with average linear resolutions of 0.2kpc and 0.9kpc, respectively. The different phases of the gas show a wide morphological variety with the nucleus as the brightest Br_g source for 33% of the LIRGs and 71% of the ULIRGs, whereas all the (U)LIRGs have their maximum H_2 emission in their nuclear regions. In LIRGs, the ionised gas distribution is dominated by the emission from the star-forming rings or giant HII regions in the spiral arms. The Br_g and [FeII] line at 1.644 micron trace the same structures, although the emission peaks at different locations in some of the objects, and the [FeII] seems to be more extended and diffuse. The ULIRG subsample contains mainly pre-coalescence interacting systems. Although the peaks of the molecular gas emission and the continuum coincide in 71% of the ULIRGs, regions with intense Pa_a (Br_g) emission tracing luminous star-forming regions located at distances of 2-4kpc away from the nucleus are also detected, usually associated with secondary nuclei or tidal tails. The gas kinematics in LIRGs are primarily due to rotational motions around the centre of the galaxy, although local deviations associated with radial flows and/or regions of higher velocity dispersions are present. The ionised and molecular gas share the same kinematics to first order, showing slight differences in the velocity amplitudes in some cases, whereas the average velocity dispersions are compatible within uncertainties. As expected, the kinematics of the ULIRG subsample is more complex, owing to the interacting nature of the objects of the sample., Comment: 40 pages, 24 figures, 7 tables, accepted for publication in A&A

Spectroscopic observations of Halpha and Hbeta emission lines of 128 star-forming galaxies in the redshift range 0.75

A new method for spectroscopic bulge-disc decomposition is presented, in which the spatial light profile in a two-dimensional spectrum is decomposed wavelength-by-wavelength into bulge and disc components, allowing separate one-dimensional spectra for each component to be constructed. This method has been applied to observations of a sample of nine S0s in the Fornax Cluster in order to obtain clean high-quality spectra of their individual bulge and disc components. So far this decomposition has only been fully successful when applied to galaxies with clean light profiles, consequently limiting the number of galaxies that could be separated into bulge and disc components. Lick index stellar population analysis of the component spectra reveals that in those galaxies where the bulge and disc could be distinguished, the bulges have systematically higher metallicities and younger stellar populations than the discs. This correlation is consistent with a picture in which S0 formation comprises the shutting down of star formation in the disc accompanied by a final burst of star formation in the bulge. The variation in spatial-fit parameters with wavelength also allows us to measure approximate colour gradients in the individual components. Such gradients were detected separately in both bulges and discs, in the sense that redder light is systematically more centrally concentrated in all components. However, a search for radial variations in the absorption line strengths determined for the individual components revealed that they are absent from the vast majority of S0 discs and bulges. The absence of gradients in line indices for most galaxies implies that the colour gradient cannot be attributed to age or metallicity variations, and is therefore most likely associated with varying degrees of obscuration by dust., Comment: 10 pages, 10 figures, 1 table, accepted for publication in MNRAS

Spatially resolved near-IR and X-ray imaging of the central region of the Luminous Infrared Galaxy NGC 5135 is presented. The kinematical signatures of strong outflows are detected in the [FeII]1.64 \mu m emission line in a compact region at 0.9 kpc from the nucleus. The derived mechanical energy release is consistent with a supernova rate of 0.05-0.1 yr$^{-1}$. The apex of the outflowing gas spatially coincides with the strongest [FeII] emission peak and with the dominant component of the extranuclear hard X-ray emission. All these features provide evidence for a plausible direct physical link between supernova-driven outflows and the hard X-ray emitting gas in a LIRG. This result is consistent with model predictions of starbursts concentrated in small volumes and with high thermalization efficiencies. A single high-mass X-ray binary (HMXB) as the major source of the hard X-ray emission although not favoured, cannot be ruled out. Outside the AGN, the hard X-ray emission in NGC 5135 appears to be dominated by the hot ISM produced by supernova explosions in a compact star-forming region, and not by the emission due to HMXB. If this scenario is common to U/LIRGs, the hard X-rays would only trace the most compact (< 100 pc) regions with high supernova and star formation densities, therefore a lower limit to their integrated star formation. The SFR derived in NGC 5135 based on its hard X-ray luminosity is a factor of two and four lower than the values obtained from the 24 \mu m and soft X-ray luminosities, respectively., Comment: Accepted for Publication in ApJ, 18 pages, 2 figures

We present absorption-line index gradients for a sample of S0 galaxies in the Fornax Cluster. The sample has been selected to span a wide range in galaxy mass, and the deep VLT-FORS2 spectroscopy allows us to explore the stellar populations all the way to the outer disk-dominated regions of these galaxies. We find that globally, in both bulges and disks, star formation ceased earliest in the most massive systems, as a further manifestation of downsizing. However, within many galaxies, we find an age gradient which indicates that star formation ended first in the outermost regions. Metallicity gradients, when detected, are always negative such that the galaxy centres are more metal-rich. This finding fits with a picture in which star formation continued in the central regions, with enriched material, after it had stopped in the outskirts. Age and metallicity gradients are correlated, suggesting that large differences in star formation history between the inner and outer parts of S0 galaxies yield large differences in their chemical enrichment. In agreement with previous results, we conclude that the radial variations in the stellar populations of S0 galaxies are compatible with the hypothesis that these galaxies are the descendants of spiral galaxies whose star formation has ceased. With the addition of radial gradient information, we are able to show that this shutdown of star formation occurred from the outside inward, with the later star formation in the central regions offering a plausible mechanism for enhancing the bulge light in these systems, as the transformation to more bulge-dominated S0 galaxies requires., Comment: 9 pages, 4 figures and Appendix, accepted for publication in MNRAS

By observing the local luminous infrared galaxy NGC5135 with the near-IR IFU spectrograph SINFONI (ESO-VLT), we report an approx. 600 pc (in projection) AGN outflow traced by [SiVI]1.96mum emission. This is the largest outflow traced by a coronal line ever reported. Its large spatial scale suggests that shocks, in addition to AGN continuum emission, are needed to locally produce [SiVI] emission. We also show, for the first time, clear kinematical evidence of the AGN-outflow vs. ISM interaction through variations in the 2D velocity fields of different gas phases. Such local perturbations in the kinematics clearly match the outflow structure. We use the [FeII]1.64mum emission, a supernovae tracer, to estimate the supernovae rate in different star-forming knots (approx. 250 pc across) within the central 2.3 kpc of NGC5135. The estimated supernovae rates go from 0.02 to 0.08 yr^{-1} being in excellent agreement with predictions from 6 cm radio emission in the same areas., Comment: 6 pages, 3 figures. To appear in A.S.P. Conference Series, "Galaxy Evolution: Infrared to Millimeter Wavelength Perspective", 25-29 October 2010, Guilin, China

We present a study of the central 2.3 kpc of NGC 5135, a nearby Luminous Infrared Galaxy (LIRG) with an AGN and circumnuclear starburst. Our main results are based on intermediate spectral resolution (~ 3000-4000) near infrared data taken with the SINFONI integral field spectrograph at the ESO VLT. The ionization of the different phases of the interstellar gas and the complex structures of the star formation have been mapped. Individual regions of interest have been identified and studied in detail. For the first time in this galaxy, we have detected the presence of a high excitation ionization cone centered on the AGN by using the [SiVI] (1.96 micron) line. So far, this structure is the largest reported in the literature for this coronal line, extending (in projection) as far as ~ 600 pc from the galaxy nucleus. In a complex spatial distribution, a variety of mechanisms are driving the gas ionization, including SNe remnant shocks, young stars and AGN photoionization. The excitation of the molecular gas, however, is mainly produced by X-rays and SNe remnant shocks. UV-mechanisms like fluorescence represent a marginal overall contribution to this process, contrary to the expectations we might have for a galaxy with a recent and strong star formation. Our SNe rate estimations from [FeII] (1.64 micron) are in excellent agreement with 6 cm radio emission predictions. Typical SNe rates between 0.01-0.04 yr^-1 were found for individual ~ 200 pc-scale regions, with an overall SNe rate of 0.4-0.5 yr^-1. Even though NGC 5135 has suffered a recent starburst (6-7 Myr ago), the data strongly suggest the presence of a second, older stellar population dominated by red giant/supergiant stars., Comment: Minor changes to previous version, including Fig. 1-4 captions, Fig. 4 units (upper panels) and reference list corrections

Using high signal-to-noise ratio VLT/FORS2 long-slit spectroscopy, we have studied the properties of the central stellar populations and dynamics of a sample of S0 galaxies in the Fornax Cluster. The central absorption-line indices in these galaxies correlate well with the central velocity dispersions (Sigma0) in accordance with what previous studies found for elliptical galaxies. However, contrary to what it is usually assumed for cluster ellipticals, the observed correlations seem to be driven by systematic age and alpha-element abundance variations, and not changes in overall metallicity. We also found that the observed scatter in the Index-Sigma0 relations can be partially explained by the rotationally-supported nature of these systems. Indeed, even tighter correlations exist between the line indices and the maximum circular velocity of the galaxies. This study suggests that the dynamical mass is the physical property driving these correlations, and for S0 galaxies such masses have to be estimated assuming a large degree of rotational support. The observed trends imply that the most massive S0s have the shortest star-formation timescales and the oldest stellar populations., Comment: 21 pages, 17 figures, 9 tables, accepted for publication in MNRAS

We test the theory that lenticular (S0) galaxies form from spirals whose star formation has been shut down. We use the globular cluster specific frequency S_N, defined as the number of globular clusters normalised by the galaxy luminosity as a diagnostic. NTT/EMMI long-slit spectroscopic observations of 11 S0 galaxies at z < 0.006 are used to measure the absorption-line indices, Hdelta, Hgamma, Mgb, Fe5270 and Fe5335 within the central r_e/8. By inverting single-stellar population models, luminosity-weighted mean ages, metallicities and alpha-element abundance ratios are derived. We estimate the amount of fading a galaxy has undergone by comparing each galaxy's S_N with its deviation from the mean spiral S_N. Galaxies with higher S_N have older stellar populations. Moreover, we find that the zero-point and amount of fading is consistent with a scenario where lenticulars are formed by the quenching of star formation in spiral galaxies. Our data also rule out any formation method for S0s which creates a large number of new globular clusters. We confirm that previous results showing a relationship between S_N and color are driven by the S_N - Age relation. Five galaxies show detectable Hbeta, [OIII], Halpha or [NII] emission lines. However, only in the two youngest galaxies is this emission unambiguously from star formation. Our results are consistent with the theory that S0 galaxies are formed when gas in normal spirals is removed, possibly as a result of a change in environment. The on-going star formation in the youngest galaxies hints that the timescale of quenching is ~< 1 Gyr. We speculate, therefore, that the truncation of star formation is a rather gentle process unlikely to involve a rapid burst of star formation., Comment: 6 pages, 4 figures, accepted for publication in Astronomy & Astrophysics

This thesis studies the origin of local S0 galaxies and their possible links to other morphological types. To address these issues, two different approaches have been adopted: a detailed study of the stellar populations of S0s in the Fornax Cluster and a study of the Tully-Fisher Relation (TFR) of local S0s in different environments., Comment: Ph.D. Thesis submitted to The University of Nottingham, U.K. Please download the complete version at http://www.nottingham.ac.uk/~ppxapgg/phdthesis.pdf

Based on FORS2-VLT long-slit spectroscopy, the analysis of the central absorption line indices of 9 S0 galaxies in the Fornax Cluster is presented. Central indices correlate with central velocity dispersions as observed in ellipticals. However, the stellar population properties of these S0s indicates that the observed trends are produced by relative differences in age and alpha-element abundances and not in metallicity ([Fe/H]) as previous studies have found in elliptical galaxies. The observed scatter in the line indices vs. velocity dispersion relations can be partially explained by the rotationally-supported nature of many of these systems. The presence of tighter line indices vs. maximum (circular) rotational velocity relations confirms this statement. It was also confirmed that the dynamical mass is the driving physical property of all these correlations and in our Fornax S0s it has to be estimated assuming rotational support., Comment: To appear in the Proceedings of IAU Symposium 241: "Stellar Populations as Building Blocks of Galaxies", 10-16 December, 2006 at La Palma, Canary Islands, Spain

We present a study of the local B and K-band Tully-Fisher Relation (TFR) between absolute magnitude and maximum circular speed in S0 galaxies. To make this study, we have combined kinematic data, including a new high-quality spectral data set from the Fornax Cluster, with homogeneous photometry from the RC3 and 2MASS catalogues, to construct the largest sample of S0 galaxies ever used in a study of the TFR. Independent of environment, S0 galaxies are found to lie systematically below the TFR for nearby spirals in both optical and infrared bands. This offset can be crudely interpreted as arising from the luminosity evolution of spiral galaxies that have faded since ceasing star formation. However, we also find a large scatter in the TFR. We show that most of this scatter is intrinsic, not due to the observational uncertainties. The presence of such a large scatter means that the population of S0 galaxies cannot have formed exclusively by the above simple fading mechanism after all transforming at a single epoch. To better understand the complexity of the transformation mechanism, we have searched for correlations between the offset from the TFR and other properties of the galaxies such as their structural properties, central velocity dispersions and ages (as estimated from line indices). For the Fornax Cluster data, the offset from the TFR relates with the estimated age of the stars in the individual galaxies, in the sense and of the magnitude expected if S0 galaxies had passively faded since being converted from spirals. This correlation implies that a significant part of the scatter in the TFR arises from the different times at which galaxies began their transformation., Comment: 17 pages, 11 figures, 3 tables, accepted for publication in MNRAS

We test the hypothesis that S0 galaxies are the descendants of fading spirals whose star formation has been shut down, by using the properties of their globular cluster (GC) systems. We estimate the amount by which the GC specific frequency (number of GCs per unit V-band luminosity) is enhanced in S0s relative to spirals. If the transformation hypothesis is correct, and no GCs are created or destroyed in the process, then this difference provides a measure of the degree to which the S0's V-band luminosity has faded relative to that of its spiral progenitor. We also explore whether the degree to which the GC specific frequency is enhanced in S0s correlates with the colour of the stellar population, as also predicted by this hypothesis in which galaxies become redder as they fade. We find that, on average, the GC specific frequency is a factor ~3 larger for S0s than for spirals, which can be interpreted as meaning that passively-evolving S0s have faded by about a factor of 3 from their spiral progenitors. This value fits remarkably well with the predictions of stellar population synthesis calculations, and the offset between the S0 and spiral Tully-Fisher relations. We also find that the global colours of S0 galaxies are strongly correlated with their GC specific frequencies: the redder the stellar population of an S0, the larger its specific frequency, as we might expect if we are catching different S0s at different stages of passively fading and reddening. Comparison to the predictions of stellar population synthesis models show that this explanation works quantitatively as well as qualitatively. These tests strongly support the hypothesis that S0 galaxies were once normal spirals, whose star formation was cut off, presumably due to a change of environment., Comment: 7 pages, 2 figures, accepted for publication in A&A

We have obtained long-slit spectroscopy for a sample of 9 S0 galaxies in the Fornax Cluster using the FORS2 spectrograph at the 8.2m ESO VLT. From these data, we have extracted the kinematic parameters, comprising the mean velocity, velocity dispersion and higher-moment H3 and H4 coefficients, as a function of position along the major axes of these galaxies. Comparison with published kinematics indicates that earlier data are often limited by their lower signal-to-noise ratio and relatively poor spectral resolution. The greater depth and higher dispersion of the new data mean that we reach well beyond the bulges of these systems, probing their disk kinematics in some detail for the first time. Qualitative inspection of the results for individual galaxies shows that they are not entirely simple systems, perhaps indicating a turbulent past. Nonetheless, we are able to derive reliable circular velocities for most of these systems, which points the way toward a study of their Tully-Fisher relation. This study, along with an analysis of the stellar populations of these systems out to large galactocentric distances, will form the bases of future papers exploiting these new high-quality data, hopefully shedding new light on the evolutionary history of these systems., Comment: 17 pages, 13 figures, 3 tables, accepted in MNRAS