arXiv subjects

H. Plana

Publications and source records attributed to H. Plana.

At least 19 recordsLinked to original sources

arXiv2026

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) XX. Star formation in the tidal tail of NGC 4254

ALMA 12CO(1-0) observations of 42 star-forming regions located outside the disc of the Virgo Cluster galaxy NGC4254 within an HI gas tail produced during the galaxy's interaction with another cluster member have revealed the presence of ten giant molecular clouds (GMCs) in four of these regions. All of the GMCs were resolved at the angular resolution of the observations (~160 pc) and have molecular gas masses of M(H2)~(0.8-2.0)x10^6} Mo. These ten clouds are characterised by gas column densities [S(H2)~10 Mo pc^-2] and velocity dispersions [sigma_v(CO)~3-12 km s^-1] respectively lower and comparable to those encountered in similar GMCs in the Milky Way. They follow the relation between the gas column density and the star formation activity (Schmidt law) derived using similar data over the stellar disc of NGC4254 and other local and Virgo cluster galaxies. With analytic calculations and tuned simulations, we show that these clouds are unstable and thus expected to dissolve on relatively short timescales (~10-30 Myr). We show that they probably formed after the collapse of dense gas clouds in the HI gas tail stripped during the gravitational interaction that the galaxy suffered several hundreds millions of years ago. The clouds are short-lived and isolated given the low density of the surrounding intracluster medium, which cannot confine the gas expelled by stellar feedback. We discuss the implications of these results in the general context of the fate of stripped gas in hostile cluster environments.

astro-ph.GA↗

arXiv2026

Kinematics of the HII region NGC 7538 from study of the Ha line

Aims. Massive stars impact their surrounding initiating star-formation along their photo-dissociation region. Once the HII region is formed it is unclear if and how the second generation of stars impacts its aspect and evolution. Methods. We performed high spectral resolution (R ~ 23400) Ha Fabry-Perot observations in five fields covering the Galactic HII region NGC 7538 and lead profiles multi-gaussian fitting to extract the parameters as peak intensity, width and velocity. We then analyse the kinematics of the ionised gas building kinematic diagrams and second order structure functions for every field. Results. The observations reveal a general blue-shifted ionised gas flow larger than 11 km s-1 in NGC 7538, consistent with previous studies. Profiles originating from features that are dark in Ha due to extinction or from outside the region show velocity dispersion larger than the one typically found for the Warm Interstellar Medium. The analysis of kinematic diagrams and second-order structure functions reveals non-thermal motions attributed to turbulence and large-scale velocity gradients. In the direction of the HII region itself the turbulence seems to be shock-dominated, with a characteristic scale length between ~ 0.72 and 1.46 pc. In this context, we propose that the kinematics of the central part of the region could be explained by the superposition of the outflow coming from IRS1 and a wind bow shock formed ahead IRS6.

astro-ph.GA↗

arXiv2021

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).XI. Two dimensional H$α$ kinematics of the edge-on ram pressure stripped galaxy NGC 4330

Using the VESTIGE survey, a deep narrow-band H$α$ imaging survey of the Virgo cluster carried on at the CFHT with MegaCam, we discovered a long diffuse tail of ionised gas in the edge-on late-type galaxy NGC 4330. This peculiar feature witnesses an ongoing ram pressure stripping (RPS) event able to remove the gas in the outer disc region. Tuned hydrodynamic simulations suggest that the RPS event is occurring almost face-on, making NGC 4330 the ideal candidate to study the effects of the perturbation in the direction perpendicular to the disc plane. We present here two new independent sets of Fabry-Perot observations (R$\simeq$10000) in order to understand the effects of the RPS process on the ionised gas kinematics. Despite their limited sensitivity to the diffuse gas emission, the data allowed us to measure the velocity and the velocity dispersion fields over the galaxy disc and in several features at the edges or outside the stellar disc formed after the RPS event. We have constructed the position-velocity diagrams and the rotation curves of the galaxy using three different techniques. The data show, consistent with the hydrodynamic simulations, that the galaxy has an inner solid-body rotation up to $\sim$2.4 kpc, with non-circular streaming motions outwards the disc and in the several external features formed during the interaction of the galaxy with the surrounding intracluster medium. The data also indicate a decrease of the rotational velocity of the gas with increasing distance from the galaxy disc along the tails, suggesting a gradual but not linear loss of angular momentum in the stripped gas. Consistent with a RPS scenario, the $i$-band image shows a boxy shape at the southwest edge of the disc, where the stellar orbits might have been perturbed by the modification of the gravitational potential well of the galaxy due to the displacement of the gas in the $z$-direction.

astro-ph.GA↗

arXiv2020

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).IX. The effects of ram pressure stripping down to the scale of individual HII regions in the dwarf galaxy IC 3476

We study the IB(s)m galaxy IC 3476 observed in the context of VESTIGE, a blind narrow-band Halpha+[NII] imaging survey of the Virgo cluster. The deep narrow-band (NB) image reveals a very pertubed ionised gas distribution, characterised by a prominent banana-shaped structure in the front of the galaxy formed of giant HII regions crossing the stellar disc, with star forming structures at ~8 kpc from the edges of the stellar disc, detected also in a deep FUV ASTROSAT/UVIT image. This particular morphology indicates that the galaxy is undergoing an almost edge-on ram pressure stripping event. The NB image also shows that the star formation activity is totally quenched in the leading edge of the disc, where the gas has been removed during the interaction. The SED fitting analysis indicates that this quenching episode is very recent (~50 Myr), and roughly corresponds to an increase of the star formation activity in the inner regions with respect to what expected for secular evolution. The analysis of these data, whose angular resolution allows the study of the induced effects of the perturbation down to the scale of individual HII regions, also suggests that the increase of the star formation activity is due to the compression of the gas along the stellar disc of the galaxy, which is able to increase its mean electron density and boost the star formation process producing bright HII regions. The hydrodynamic interaction has deeply perturbed the velocity field of the ionised gas component while leaving unaffected that of the stellar disc. The comparison of the data with hydrodynamic simulations accounting for the different gas phases (atomic, molecular, ionised) consistently indicates that the perturbing event is very recent, once again confirming that ram pressure stripping is a violent phenomenon able to perturb on short timescales the evolution of galaxies in rich environments.

astro-ph.GA↗

arXiv2020

Dorado and its member galaxies. Ha imaging of the group backbone

ABRIDGED: Dorado is a nearby, rich and clumpy galaxy group that extends for several degrees in the Southern Hemisphere. For the first time, we map the Ha distribution as a possible indicator of star formation (SF) activity of Dorado members a large fraction of which show interaction and merging signatures. With the 2.5m du Pont and the 1m Swope telescopes we obtained narrow-band, calibrated images of 14 galaxies, forming the backbone of the group, mapping Ha+[N II] down to few 10$^{-17}$ erg~cm$^{-2}$~s$^{-1}$~arcsec$^{-2}$. We estimated the galaxy star formation rate (SFR) from the Ha fluxes, corrected for Galaxy foreground extinction and [N II] contamination. Ha+[N II] emission has been detected in all galaxies. HII regions clearly emerge in late-type galaxies (LTGs) , while in early-type galaxies (ETGs) the Ha+[N II] emission is dominated by [N II], especially in the central regions. However, HII complexes are also revealed in four ETGs. Considering the Dorado group as a whole, we notice that the Ha+[N II] equivalent width, a measure of the specific SF, increases with the morphological type, from early to late-type members, although it remains lower that what observed in similar surveys of spiral galaxies. The SFR of the spiral members is in the range of what observed in similar galaxies surveys James+ (2004), although, in three spirals the SFR is well below the median for their morphological classes. The SFR of some early-type members tends, at odds, to be higher than the average derived from Ha+[N II] surveys of this morphological family. We detected in Ha+[N II] all the ETGs observed and half of them show HII regions. These findings suggest that ETGs in this group are not dead galaxies: their SF has not shut down yet. Mechanisms such as gas stripping and gas accretion, through galaxy-galaxy interaction, seem relevant in modifying the SF in this evolutionary phase of Dorado.

astro-ph.GA↗

arXiv2020

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).VI. Environmental quenching on HII region scales

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band Halpha+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada-French-Hawaii telescope (CFHT). We use a new set of data extracted from VESTIGE to study the impact of the hostile cluster environment on the star formation process down to the scale of HII regions (~ 50 pc). HII regions are identified and their parameters measured using the HIIphot code on a sample of 114 late-type galaxies spanning a wide range in morphological type (Sa-Sd, Im, BCD), stellar mass (10^6.5 <= M_star <= 10^11 Mo), and star formation activity (10^-3 <= SFR <= 10 Mo yr^-1). Owing to the exquisite average resolution of the VESTIGE data (0.65 arcsec), we detect 11302 HII regions with an Halpha luminosity L(Halpha) >= 10^37 erg s^-1. We show that the typical number of HII regions in gas-stripped objects is significantly lower than in healthy late-types of similar stellar mass. We also show that in these gas-stripped galaxies the number of HII regions significantly drops outside the effective radius, suggesting that the quenching process occurs outside-in, in agreement with other multifrequency observations. These new results consistently confirm that the main mechanism responsible for the decrease of the star formation activity observed in cluster galaxies is ram pressure, allowing us to discard other milder processes such as starvation or strangulation unable to reproduce the observed radially truncated profiles.

astro-ph.GA↗

arXiv2019

SIGNALS: I. Survey Description

SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observing program designed to investigate massive star formation and HII regions in a sample of local extended galaxies. The program will use the imaging Fourier transform spectrograph SITELLE at the Canada-France-Hawaii Telescope. Over 355 hours (54.7 nights) have been allocated beginning in fall 2018 for eight consecutive semesters. Once completed, SIGNALS will provide a statistically reliable laboratory to investigate massive star formation, including over 50 000 resolved HII regions : the largest, most complete, and homogeneous database of spectroscopically and spatially resolved extragalactic HII regions ever assembled. For each field observed, three datacubes covering the spectral bands of the filters SN1 (363 -386 nm), SN2 (482 - 513 nm), and SN3 (647 - 685 nm) are gathered. The spectral resolution selected for each spectral band is 1000, 1000, and 5000, respectively. As defined, the project sample will facilitate the study of small-scale nebular physics and many other phenomena linked to star formation at a mean spatial resolution of 20 pc. This survey also has considerable legacy value for additional topics including planetary nebulae, diffuse ionized gas, andsupernova remnants. The purpose of this paper is to present a general outlook of the survey, notably the observing strategy, galaxy sample, and science requirements.

astro-ph.GA↗

arXiv2018

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).V. Properties of the ionised gas filament of M87

We have observed the giant elliptical galaxy M87 during the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Halpha+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada French Hawaii Telescope (CFHT). The deep narrow-band image confirmed the presence of a filament of ionised gas extending up to ~ 3 kpc in the north-western direction and ~ 8 kpc to the south-east, with a couple of plumes of ionised gas, the weakest of which, at ~ 18 kpc from the nucleus, was previously unknown. The analysis of deep optical images taken from the NGVS survey confirms that this gas filament is associated with dust seen in absorption which is now detected up to ~ 2.4 kpc from the nucleus. We have also analysed the physical and kinematical properties of the ionised gas filament using deep IFU MUSE data covering the central 4.8 x 4.8 kpc^2 of the galaxy. The spectroscopic data confirms a perturbed kinematics of the ionised gas, with differences in velocity of ~ 700-800 km s^-1 on scales of < 1 kpc. The analysis of 2D diagnostic diagrams and the observed relationship between the shock-sensitive [OI]/Halpha line ratio and the velocity dispersion of the gas suggest that the gas is shock-ionised.

astro-ph.GA↗

arXiv2018

A multi-wavelength study of the evolution of Early-Type Galaxies in Groups: the ultraviolet view

ABRIDGED- The UV-optical color magnitude diagram (CMD) of rich galaxy groups is characterised by a well developed Red Sequence (RS), a Blue Cloud (BC) and the so-called Green Valley (GV). Loose, less evolved groups of galaxies likely not virialized yet may lack a well defined RS. This is actually explained in the framework of galaxy evolution. We are focussing on understanding galaxy migration towards the RS, checking for signatures of such a transition in their photometric and morphological properties. We report on the UV properties of a sample of ETGs galaxies inhabiting the RS. The analysis of their structures, as derived by fitting a Sersic law to their UV luminosity profiles, suggests the presence of an underlying disk. This is the hallmark of dissipation processes that still must have a role in the evolution of this class of galaxies. SPH simulations with chemo-photometric implementations able to match the global properties of our targets are used to derive their evolutionary paths through UV-optical CDM, providing some fundamental information such as the crossing time through the GV, which depends on their luminosity. The transition from the BC to the RS takes several Gyrs, being about 3-5 Gyr for the the brightest galaxies and more long for fainter ones, if it occurs. The photometric study of nearby galaxy structures in UV is seriously hampered by either the limited FoV of the cameras (e.g in HST) or by the low spatial resolution of the images (e.g in the GALEX). Current missions equipped with telescopes and cameras sensitive to UV wavelengths, such as Swift-UVOT and Astrosat-UVIT, provide a relatively large FoV and better resolution than the GALEX. More powerful UV instruments (size, resolution and FoV) are obviously bound to yield fundamental advances in the accuracy and depth of the surface photometry and in the characterisation of the galaxy environment.

astro-ph.GA↗

arXiv2018

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).I. Introduction to the Survey

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band Halpha+[NII] imaging survey carried out with MegaCam at the Canada-France-Hawaii Telescope. The survey covers the whole Virgo cluster region from its core to one virial radius (104 deg^2). The sensitivity of the survey is of f(Halpha) ~ 4 x 10^-17 erg sec-1 cm^-2 (5 sigma detection limit) for point sources and Sigma (Halpha) ~ 2 x 10^-18 erg sec^-1 cm^-2 arcsec^-2 (1 sigma detection limit at 3 arcsec resolution) for extended sources, making VESTIGE the deepest and largest blind narrow-band survey of a nearby cluster. This paper presents the survey in all its technical aspects, including the survey design, the observing strategy, the achieved sensitivity in both the narrow-band Halpha+[NII] and in the broad-band r filter used for the stellar continuum subtraction, the data reduction, calibration, and products, as well as its status after the first observing semester. We briefly describe the Halpha properties of galaxies located in a 4x1 deg^2 strip in the core of the cluster north of M87, where several extended tails of ionised gas are detected. This paper also lists the main scientific motivations of VESTIGE, which include the study of the effects of the environment on galaxy evolution, the fate of the stripped gas in cluster objects, the star formation process in nearby galaxies of different type and stellar mass, the determination of the Halpha luminosity function and of the Halpha scaling relations down to ~ 10^6 Mo stellar mass objects, and the reconstruction of the dynamical structure of the Virgo cluster. This unique set of data will also be used to study the HII luminosity function in hundreds of galaxies, the diffuse Halpha+[NII] emission of the Milky Way at high Galactic latitude, and the properties of emission line galaxies at high redshift.

astro-ph.GA↗

arXiv2017

The NGC 454 system: anatomy of a mixed on-going merger

This paper focuses on NGC 454, a nearby interacting pair of galaxies (AM0112-554, RR23), composed of an early-type (NGC 454 E) and a star forming late-type companion (NGC 454 W). We aim at characterizing this wet merger candidate via a multi-lambda analysis, from near-UV to optical using SWIFT-UVOT, and mapping the Halpha intensity (I) distribution, velocity (Vr), and velocity dispersion (sigma) fields with SAM+Perot-Fabry at SOAR observations. Luminosity profiles suggest that NGC 454 E is an S0. Distortions in its outskirts caused by the on-going interaction are visible in both optical and near-UV frames. In NGC 454 W, the NUV-UVOT images and the Halpha show a set of star forming complexes connected by a faint tail. Halpha emission is detected along the line connecting NGC 454 E to the NGC 454 main HII complex. We investigate the (I-sigma), (I-Vr ) (Vr-sigma) diagnostic diagrams of the HII complexes, most of which can be interpreted in a framework of expanding bubbles. In the main HII complex, enclosed in the UV brightest region, the gas velocity dispersion is highly supersonic reaching 60 km/s. However, Halpha emission profiles are mostly asymmetric indicating the presence of multiple components with an irregular kinematics. Observations point towards an advanced stage of the encounter. Our SPH simulations with chemophotometric implementation suggest that this mixed pair can be understood in terms of a 1:1 gas/halos encounter giving rise to a merger in about 0.2 Gyr from the present stage.

astro-ph.GA↗

arXiv2016

Correction of distortion for optimal image stacking in Wide Field Adaptive Optics: Application to GeMS data

The advent of Wide Field Adaptive Optics (WFAO) systems marks the beginning of a new era in high spatial resolution imaging. The newly commissioned Gemini South Multi-Conjugate Adaptive Optics System (GeMS) combined with the infrared camera Gemini South Adaptive Optics Imager (GSAOI), delivers quasi diffraction-limited images over a field of 2 arc-minutes across. However, despite this excellent performance, some variable residues still limit the quality of the analyses. In particular, distortions severely affect GSAOI and become a critical issue for high-precision astrometry and photometry. In this paper, we investigate an optimal way to correct for the distortion following an inverse problem approach. Formalism as well as applications on GeMS data are presented.

astro-ph.IM↗

arXiv2016

Deep GeMS/GSAOI near-infrared observations of N159W in the Large Magellanic Cloud

Aims. The formation and properties of star clusters at the edge of H II regions are poorly known, partly due to limitations in angular resolution and sensitivity, which become particularly critical when dealing with extragalactic clusters. In this paper we study the stellar content and star-formation processes in the young N159W region in the Large Magellanic Cloud. Methods. We investigate the star-forming sites in N159W at unprecedented spatial resolution using JHKs-band images obtained with the GeMS/GSAOI instrument on the Gemini South telescope. The typical angular resolution of the images is of 100 mas, with a limiting magnitude in H of 22 mag (90 percent completeness). Photometry from our images is used to identify candidate young stellar objects (YSOs) in N159W. We also determine the H-band luminosity function of the star cluster at the centre of the H II region and use this to estimate its initial mass function (IMF). Results. We estimate an age of 2 + or - 1 Myr for the central cluster, with its IMF described by a power-law with an index of gamma = - 1.05 + or - 0.2 , and with a total estimated mass of 1300 solar mass. We also identify 104 candidate YSOs, which are concentrated in clumps and subclusters of stars, principally at the edges of the H II region. These clusters display signs of recent and active star-formation such as ultra-compact H II regions, and molecular outflows. This suggests that the YSOs are typically younger than the central cluster, pointing to sequential star-formation in N159W, which has probably been influenced by interactions with the expanding H II bubble.

astro-ph.IM↗

arXiv2016

Dynamical analysis of the cluster pair: A3407 + A3408

We carried out a dynamical study of the galaxy cluster pair A3407 \& A3408 based on a spectroscopic survey obtained with the 4 meter Blanco telescope at the CTIO, plus 6dF data, and ROSAT All-Sky-Survey. The sample consists of 122 member galaxies brighter than $m_R=20$. Our main goal is to probe the galaxy dynamics in this field and verify if the sample constitutes a single galaxy system or corresponds to an ongoing merging process. Statistical tests were applied to clusters members showing that both the composite system A3407 + A3408 as well as each individual cluster have Gaussian velocity distribution. A velocity gradient of $\sim 847\pm 114$ $\rm km\;s^{-1}$ was identified around the principal axis of the projected distribution of galaxies, indicating that the global field may be rotating. Applying the KMM algorithm to the distribution of galaxies we found that the solution with two clusters is better than the single unit solution at the 99\% c.l. This is consistent with the X-ray distribution around this field, which shows no common X-ray halo involving A3407 and A3408. We also estimated virial masses and applied a two-body model to probe the dynamics of the pair. The more likely scenario is that in which the pair is gravitationally bound and probably experiences a collapse phase, with the cluster cores crossing in less than $\sim$1 $h^{-1}$ Gyr, a pre-merger scenario. The complex X-ray morphology, the gas temperature, and some signs of galaxy evolution in A3408 suggests a post-merger scenario, with cores having crossed each other $\sim 1.65 h^{-1}$Gyr ago, as an alternative solution.

astro-ph.GA↗

arXiv2015

Deep near-infrared adaptive optics observations of a young embedded cluster at the edge of the RCW 41 HII region

We investigate the star formation activity in a young star forming cluster embedded at the edge of the RCW 41 HII region. As a complementary goal, we aim at demonstrating the gain provided by Wide-Field Adaptive Optics instruments to study young clusters. We used deep, JHKs images from the newly commissioned Gemini-GeMS/GSAOI instrument, complemented with Spitzer IRAC observations, in order to study the photometric properties of the young stellar cluster. GeMS is an AO instrument, delivering almost diffraction limited images over a field of 2' across. The exquisite angular resolution allows us to reach a limiting magnitude of J = 22 for 98% completeness. The combination of the IRAC photometry with our JHKs catalog is used to build color-color diagrams, and select Young Stellar Objects (YSOs) candidates. We detect the presence of 80 Young Stellar Object (YSO) candidates. Those YSOs are used to infer the cluster age, which is found to be in the range 1 to 5 Myr. We find that 1/3 of the YSOs are in a range between 3 to 5 Myr, while 2/3 of the YSO are < 3 Myr. When looking at the spatial distribution of these two populations, we evidence a potential age gradient across the field, suggesting sequential star formation. We construct the IMF, and show that we can sample the mass distribution well into the brown dwarf regime (down to 0.01 Msun). The logarithmic mass function rises to peak at 0.3 Msun, before turning over and declining into the brown dwarf regime. The total cluster mass derived is estimated to be 78 +/- 18 Msun, while the ratio of brown dwarfs to star derived is 18 p/- 5 %. When comparing with other young clusters, we find that the IMF shape of the young cluster embedded within RCW 41 is consistent with those of Trapezium, IC 348 or Chamaeleon I, except for the IMF peak, which happens to be at higher mass. This characteristic is also seen in clusters like NGC 6611 or even Taurus.

astro-ph.SR↗

arXiv2015

Gemini-IFU spectroscopy of HH 111

We present new optical observations of the HH 111 Herbig-Haro jet using the Gemini Multi Object Spectrograph in its Integral Field Unit mode. Eight fields of 5" x 3.5" have been positioned along and across the HH 111 jet, covering the spatial region from knot E to L in HH 111 (namely, knots E, F, G, H, J, K and L). We present images and velocity channel maps for the [O I] 6300+6360, Halpha, [N II] 6548+6583 and [S II] 6716+6730 lines, as well as for the [S II]6716/6730 line ratio. We find that the HH 111 jet has an inner region with lower excitation and higher radial velocity, surrounded by a broader region of higher excitation and lower radial velocity. Also, we find higher electron densities at lower radial velocities. These results imply that the HH 111 jet has a fast, axial region with lower velocity shocks surrounded by a lower velocity sheath with higher velocity shocks.

astro-ph.SR↗

arXiv2014

The H$α$ kinematics of interacting galaxies in 12 compact groups

We present new Fabry-Perot observations for a sample of 42 galaxies located in twelve compact groups of galaxies: HCG 1, HCG 14, HCG 25, HCG 44, HCG 53, HCG 57, HCG 61, HCG 69, HCG 93, VV 304, LGG 455 and Arp 314. From the 42 observed galaxies, a total of 26 objects are spiral galaxies, which range from Sa to Im morphological types. The remaining 16 objects are E, S0 and S0a galaxies. Using these observations, we have derived velocity maps, monochromatic and velocity dispersion maps for 24 galaxies, where 18 are spiral, three are S0a, two are S0 and one is an Im galaxy. From the 24 velocity fields obtained, we could derive rotation curves for 15 galaxies; only two of them exhibit rotation curves without any clear signature of interactions. Based on kinematic information, we have evaluated the evolutionary stage of the different groups of the current sample. We identify groups that range from having no H$α$ emission to displaying an extremely complex kinematics, where their members display strongly perturbed velocity fields and rotation curves. In the case of galaxies with no H$α$ emission, we suggest that past galaxy interactions removed their gaseous components, thereby quenching their star formation. However, we can not discard that the lack of H$α$ emission is linked with the detection limit for some of our observations.

astro-ph.GA↗

arXiv2014

The mass profile and dynamical status of the z~0.8 galaxy cluster LCDCS 0504

Constraints on the mass distribution in high-redshift clusters of galaxies are not currently very strong. We aim to constrain the mass profile, M(r), and dynamical status of the $z \sim 0.8$ LCDCS 0504 cluster of galaxies characterized by prominent giant gravitational arcs near its center. Our analysis is based on deep X-ray, optical, and infrared imaging, as well as optical spectroscopy. We model the mass distribution of the cluster with three different mass density profiles, whose parameters are constrained by the strong lensing features of the inner cluster region, by the X-ray emission from the intra-cluster medium, and by the kinematics of 71 cluster members. We obtain consistent M(r) determinations from three methods (dispersion-kurtosis, caustics and MAMPOSSt), out to the cluster virial radius and beyond. The mass profile inferred by the strong lensing analysis in the central cluster region is slightly above, but still consistent with, the kinematics estimate. On the other hand, the X-ray based M(r) is significantly below both the kinematics and strong lensing estimates. Theoretical predictions from $Λ$CDM cosmology for the concentration--mass relation are in agreement with our observational results, when taking into account the uncertainties in both the observational and theoretical estimates. There appears to be a central deficit in the intra-cluster gas mass fraction compared to nearby clusters. Despite the relaxed appearance of this cluster, the determinations of its mass profile by different probes show substantial discrepancies, the origin of which remains to be determined. The extension of a similar dynamical analysis to other clusters of the DAFT/FADA survey will allow to shed light on the possible systematics that affect the determination of mass profiles of high-z clusters, possibly related to our incomplete understanding of intracluster baryon physics.

astro-ph.CO↗