arXiv subjects

S. Cantalupo

Publications and source records attributed to S. Cantalupo.

33 records · Page 2Linked to original sources

arXiv2019

The MUSE Ultra Deep Field (MUDF). II. Survey design and the gaseous properties of galaxy groups at 0.5 < z < 1.5

We present the goals, design, and first results of the MUSE Ultra Deep Field (MUDF) survey, a large programme using the Multi Unit Spectroscopic Explorer (MUSE) instrument at the ESO Very Large Telescope. The MUDF survey is collecting ~ 150 hours on-source of integral field optical spectroscopy in a 1.5 x 1.2 square arcmin region which hosts several astrophysical structures along the line of sight, including two bright z ~ 3.2 quasars with close separation (~ 500 kpc). Following the description of the data reduction procedures, we present the analysis of the galaxy environment and gaseous properties of seven groups detected at redshifts 0.5 < z < 1.5, spanning a large dynamic range in halo mass, log(Mh/Msun) ~ 11 - 13.5. For four of the groups, we find associated MgII absorbers tracing cool gas in high-resolution spectroscopy of the two quasars, including one case of correlated absorption in both sightlines at distance ~ 480 kpc. The absorption strength associated with the groups is higher than what has been reported for more isolated galaxies of comparable mass and impact parameters. We do not find evidence for widespread cool gas giving rise to strong absorption within these groups. Combining these results with the distribution of neutral and ionised gas seen in emission in lower-redshift groups, we conclude that gravitational interactions in the group environment strip gas from the galaxy haloes into the intragroup medium, boosting the cross section of cool gas and leading to the high fraction of strong MgII absorbers that we detect.

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arXiv2019

A giant Ly$α$ nebula and a small-scale clumpy outflow in the system of the exotic quasar J0952+0114 unveiled by MUSE

The well-known quasar SDSS J095253.83+011421.9 (J0952+0114) at z=3.02 has one of the most peculiar spectra discovered so far, showing the presence of narrow Ly$α$ and broad metal emission lines. Although recent studies have suggested that a Proximate Damped Ly$α$ system (PDLA) causes this peculiar spectrum, the origin of the gas associated with the PDLA is unknown. Here we report the results of MUSE observations that reveal a new giant ($\approx$ 100 physical kpc) Lyman $α$ nebula. The detailed analysis of the Ly$α$ velocity, velocity dispersion, and surface brightness profiles suggests that the J0952+0114 Ly$α$ nebula shares similar properties of other QSO nebulae previously detected with MUSE, implying that the PDLA in J0952+0144 is covering only a small fraction of the QSO emission solid angle. We also detected bright and spectrally narrow CIV$λ$1550 and HeII$λ$1640 extended emission around J0952+0114 with velocity centroids similar to the peak of the extended and central narrow Ly$α$ emission. The presence of a peculiarly bright, unresolved, and relatively broad HeII$λ$1640 emission in the central region at exactly the same PDLA redshift hints at the possibility that the PDLA originates in a clumpy outflow with a bulk velocity of about 500 km/s. The smaller velocity dispersion of the large scale Ly$α$ emission suggests that the high-speed outflow is confined to the central region. Lastly, the derived spatially resolved HeII/Ly$α$ and CIV/Ly$α$ maps show a positive gradient with the distance to the QSO hinting at a non-homogeneous ionization parameter distribution.

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arXiv2019

The MUSE Ultra Deep Field (MUDF). I. Discovery of a group of Ly$α$ nebulae associated with a bright $z\approx 3.23$ quasar pair

We present first results from Multi Unit Spectroscopic Explorer (MUSE) observations at the Very Large Telescope in the MUSE Ultra Deep Field (MUDF), a $\approx 1.2\times 1.4$ arcmin$^2$ region for which we are collecting $\approx$200 hours of integral field spectroscopy. The $\approx 40$-hour observation completed to date reveals the presence of a group of three Ly$α$ nebulae associated with a bright quasar pair at $z\simeq3.23$ with projected separation of $\approx 500\rm~kpc$. Two of the nebulae are physically associated with the quasars which are likely powering the Ly$α$ emission, and extend for $\gtrsim 100~\rm kpc$ at a surface brightness level of $\approx 6\times 10^{-19}~\rm erg~s^{-1}~cm^{-2}~arcsec^{-2}$. A third smaller ($\approx$35 kpc) nebula lies at a velocity offset of $\approx 1550$ km s$^{-1}$. Despite their clustered nature, the two large nebulae have properties similar to those observed in isolated quasars and exhibit no sharp decline in flux at the current depth, suggesting an even more extended distribution of gas around the quasars. We interpret the shape and the alignment of the two brighter nebulae as suggestive of the presence of an extended structure connecting the two quasar host galaxies, as seen for massive galaxies forming within gas-rich filaments in cosmological simulations.

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arXiv2018

Nearly all the sky is covered by Lyman-alpha emission around high redshift galaxies

Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, fed by inflows from the intergalactic medium and by outflows due to galactic winds. Absorption-line measurements along the sightlines to bright and rare background quasars indicate that this circumgalactic medium pervades far beyond the extent of starlight in galaxies, but very little is known about the spatial distribution of this gas. A new window into circumgalactic environments was recently opened with the discovery of ubiquitous extended Lyman-alpha emission from hydrogen around high-redshift galaxies, facilitated by the extraordinary sensitivity of the MUSE instrument at the ESO Very Large Telescope. Due to the faintness of this emission, such measurements were previously limited to especially favourable systems or to massive statistical averaging. Here we demonstrate that low surface brightness Lyman-alpha emission surrounding faint galaxies at redshifts between 3 and 6 adds up to a projected sky coverage of nearly 100%. The corresponding rate of incidence (the mean number of Lyman-alpha emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high column density absorbers frequently detected in the spectra of distant quasars. This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected also in emission.

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arXiv2018

QSO MUSEUM I: A sample of 61 extended Ly$α$-emission nebulae surrounding $z\sim3$ quasars

Motivated by the recent discovery of rare Enormous Lyman-Alpha Nebulae (ELAN) around z~2 quasars, we have initiated a long-term observational campaign with the MUSE instrument to directly uncover the astrophysics of the gas around quasars. We present here the first 61 targets of our effort under the acronym QSO MUSEUM (Quasar Snapshot Observations with MUse: Search for Extended Ultraviolet eMission). These quasars have a median redshfit of z=3.17, absolute $i$ magnitude in the range $-29.67\leq M_i(z=2)\leq-27.03$, and different levels of radio-loudness. This sample unveils diverse specimens of Ly$α$ nebulosities extending for tens of kiloparsecs around these quasars (on average out to a maximum projected distance of 80 kpc) above a surface brightness SB$>8.8\times10^{-19}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$ ($2σ$). The bulk of the extended Ly$α$ emission is within R<50 kpc, and is characterized by relatively quiescent kinematics, with average velocity dispersions of $\langle σ_{\rm Lyα}\rangle < 400$~km~s$^{-1}$. Therefore, the motions within all these Ly$α$ nebulosities have amplitudes consistent with gravitational motions expected in dark matter halos hosting quasars at these redshifts, possibly reflecting the complexity in propagating a fast wind on large scales. Our current data suggest a combination of photoionization and resonant scattering as powering mechanisms of the Ly$α$ emission. We discover the first $z\sim3$ ELAN, which confirms a very low probability ($\sim1\%$) of occurrence of such extreme systems at these cosmic epochs. Finally, we discuss the redshift evolution currently seen in extended Ly$α$ emission around radio-quiet quasars from $z\sim3$ to $z\sim2$, concluding that it is possibly linked to a decrease of cool gas mass within the quasars' CGM from $z\sim3$ to $z\sim2$, and thus to the balance of cool vs hot media.

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arXiv2018

Properties and redshift evolution of star-forming galaxies with high [OIII]/[OII] ratios with MUSE at 0.28<z<0.85

We present a study of the [OIII]5007/[OII]3727 (O32) ratios of star-forming galaxies drawn from MUSE data spanning a redshift range 0.28 4. Here we aim to understand the properties and the occurrences of galaxies with such high line ratios. Combining data from several MUSE GTO programmes, we select a population of star-forming galaxies with bright emission lines, from which we draw 406 galaxies for our analysis based on their position in the z-dependent star formation rate (SFR) - stellar mass (M*) plane. Out of this sample 15 are identified as extreme oxygen emitters based on their O32 ratios (3.7%) and 104 galaxies have O32>1 (26%). Our analysis shows no significant correlation between M*, SFR, and the distance from the SFR-M* relation with O32. We find a decrease in the fraction of galaxies with O32>1 with increasing M*, however, this is most likely a result of the relationship between O32 and metallicity, rather than between O32 and M*. We draw a comparison sample of local analogues with ~0.03 from SDSS, and find similar incidence rates for this sample. In order to investigate the evolution in the fraction of high O32 emitters with redshift, we bin the sample into three redshift subsamples of equal number, but find no evidence for a dependence on redshift. Furthermore, we compare the observed line ratios with those predicted by nebular models with no LyC escape and find that most of the extreme oxygen emitters can be reproduced by low metallicity models. The remaining galaxies are likely LyC emitter candidates. Finally, based on a comparison between electron temperature estimates from the [OIII4363]/[OIII]5007 ratio of the extreme oxygen emitters and nebular models, we argue that the galaxies with the most extreme O32 ratios have young light-weighted ages.

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arXiv2018

Recovering the systemic redshift of galaxies from their Lyman-alpha line profile

The Lyman alpha (lya) line of Hydrogen is a prominent feature in the spectra of star-forming galaxies, usually redshifted by a few hundreds of km/s compared to the systemic redshift. This large offset hampers follow-up surveys, galaxy pair statistics and correlations with quasar absorption lines when only lya is available. We propose diagnostics that can be used to recover the systemic redshift directly from the properties of the lya line profile. We use spectroscopic observations of Lyman-Alpha Emitters (LAEs) for which a precise measurement of the systemic redshift is available. Our sample contains 13 sources detected between z~3 and z~6 as part of various Multi Unit Spectroscopic Explorer (MUSE) Guaranteed Time Observations (GTO). We also include a compilation of spectroscopic lya data from the literature spanning a wide redshift range (z~0-8). First, restricting our analysis to double-peaked lya spectra, we find a tight correlation between the velocity offset of the red peak with respect to the systemic redshift, Vpeak, and the separation of the peaks. Secondly, we find a correlation between Vpeak and the full width at half maximum of the lya line. Fitting formulas, to estimate systemic redshifts of galaxies with an accuracy of +-100 km/s when only the lya emission line is available, are given for the two methods.

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arXiv2017

The MUSE-Wide survey: Detection of a clustering signal from Lyman-α-emitters at 3<z<6

We present a clustering analysis of a sample of 238 Ly{$α$}-emitters at redshift 3<z<6 from the MUSE-Wide survey. This survey mosaics extragalactic legacy fields with 1h MUSE pointings to detect statistically relevant samples of emission line galaxies. We analysed the first year observations from MUSE-Wide making use of the clustering signal in the line-of-sight direction. This method relies on comparing pair-counts at close redshifts for a fixed transverse distance and thus exploits the full potential of the redshift range covered by our sample. A clear clustering signal with a correlation length of r0 = 2.9(+1.0/-1.1) Mpc (comoving) is detected. Whilst this result is based on only about a quarter of the full survey size, it already shows the immense potential of MUSE for efficiently observing and studying the clustering of Ly{$α$}-emitters.

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arXiv2017

MUSE-inspired view of the quasar Q2059-360, its Lyman alpha blob, and its neighborhood

The radio-quiet quasar Q2059-360 at redshift $z=3.08$ is known to be close to a small Lyman $α$ blob (LAB) and to be absorbed by a proximate damped Ly$α$ (PDLA) system. Here, we present the Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopy follow-up of this quasi-stellar object (QSO). Our primary goal is to characterize this LAB in detail by mapping it both spatially and spectrally using the Ly$α$ line, and by looking for high-ionization lines to constrain the emission mechanism. Combining the high sensitivity of the MUSE integral field spectrograph mounted on the Yepun telescope at ESO-VLT with the natural coronagraph provided by the PDLA, we map the LAB down to the QSO position, after robust subtraction of QSO light in the spectral domain. In addition to confirming earlier results for the small bright component of the LAB, we unveil a faint filamentary emission protruding to the south over about 80 pkpc (physical kpc); this results in a total size of about 120 pkpc. We derive the velocity field of the LAB (assuming no transfer effects) and map the Ly$α$ line width. Upper limits are set to the flux of the N V $λ1238-1242$, C IV $λ1548-1551$, He II $λ1640$, and C III] $λ1548-1551$ lines. We have discovered two probable Ly$α$ emitters at the same redshift as the LAB and at projected distances of 265 kpc and 207 kpc from the QSO; their Ly$α$ luminosities might well be enhanced by the QSO radiation. We also find an emission line galaxy at $z=0.33$ near the line of sight to the QSO. This LAB shares the same general characteristics as the 17 others surrounding radio-quiet QSOs presented previously. However, there are indications that it may be centered on the PDLA galaxy rather than on the QSO.

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arXiv2017

Probing the intra-group medium of a z = 0.28 galaxy group

We present new MUSE observations of a galaxy group probed by a background quasar. The quasar sightline passes between multiple $z=0.28$ galaxies, whilst showing at the same redshift low ionised metal line species, including Ca II, Mg I, Mg II and Fe II. Based on the galaxy redshifts measured from the MUSE data, we estimate the galaxies to be part of a small galaxy group with a halo mass of $\approx6\times10^{12}$ M$_{\odot}$. We use the MUSE data to reveal the two dimensional dynamical properties of the gas and stars in the group galaxies, and relate these to the absorber kinematics. With these data we consider a number of scenarios for the nature of the gas probed by the sightline absorbers: a co-rotating gas halo associated with a single galaxy within the group; outflowing material from a single group member powered by recent star-formation; and cool dense gas associated with an intra-group medium. We find that the dynamics, galaxy impact parameters, star-formation rates, and the absorber strength suggest the cool gas can not be clearly associated with any single galaxy within the group. Instead we find that the observations are consistent with a superposition of cool gas clouds originating with the observed galaxies as they fall into the group potential, and are now likely in the process of forming the intra-group medium.

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arXiv2016

Possible Signatures of a Cold-Flow Disk from MUSE using a z=1 galaxy--quasar pair towards SDSSJ1422-0001

We use a background quasar to detect the presence of circum-galactic gas around a $z=0.91$ low-mass star forming galaxy. Data from the new Multi Unit Spectroscopic Explorer (MUSE) on the VLT show that the host galaxy has a dust-corrected star-formation rate (SFR) of 4.7$\pm$0.2 Msun/yr, with no companion down to 0.22 Msun/yr (5 $σ$) within 240 kpc (30"). Using a high-resolution spectrum (UVES) of the background quasar, which is fortuitously aligned with the galaxy major axis (with an azimuth angle $α$ of only $15^\circ$), we find, in the gas kinematics traced by low-ionization lines, distinct signatures consistent with those expected for a "cold flow disk" extending at least 12 kpc ($3\times R_{1/2}$). We estimate the mass accretion rate $\dot M_{\rm in}$ to be at least two to three times larger than the SFR, using the geometric constraints from the IFU data and the HI column density of $\log N_{\rm HI} \simeq 20.4$ obtained from a {\it HST}/COS NUV spectrum. From a detailed analysis of the low-ionization lines (e.g. ZnII, CrII, TiII, MnII, SiII), the accreting material appears to be enriched to about 0.4 $Z_\odot$ (albeit with large uncertainties: $\log Z/Z_\odot=-0.4~\pm~0.4$), which is comparable to the galaxy metallicity ($12+\log \rm O/H=8.7\pm0.2$), implying a large recycling fraction from past outflows. Blue-shifted MgII and FeII absorptions in the galaxy spectrum from the MUSE data reveal the presence of an outflow. The MgII and FeII doublet ratios indicate emission infilling due to scattering processes, but the MUSE data do not show any signs of fluorescent FeII* emission.

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arXiv2016

MUSE observations of the lensing cluster Abell 1689

We present the results obtained with MUSE on the core of the lensing cluster A1689. Integral-field observations with MUSE provide a unique view of the central region, allowing us to conduct a complete census on both cluster galaxies and lensed background sources, identified based on their spectral features without preselection. We investigate the multiple-image configuration for all known sources in the field. Previous to our survey, 28 different lensed galaxies displaying 46 multiple images were known in the MUSE field of view, most of them based on photometric redshifts and lensing considerations. Among them, we spectroscopically confirm 12 images based on their emission-lines, corresponding to 7 different lensed galaxies between z = 0.95 and 5.0. In addition, 14 new galaxies have been spectroscopically identified in this area, with redshifts ranging between 0.8 and 6.2. All background sources within the MUSE field of view correspond to multiple-imaged systems lensed by A1689. 17 sources in total are found at z > 3 based on their Lyman-alpha emission, with Lyman-alpha luminosities ranging between 40.5 < log(Lyα) < 42.5 after correction for magnification. This sample is particularly sensitive to the slope of the LF toward the faintest-end. The density of sources obtained in this survey is consistent with a steep value of α < -1.5, although this result still needs further investigation. These results illustrate the efficiency of MUSE in the characterization of lensing clusters on one hand, and the study of faint and distant populations of galaxies on the other hand. In particular, our current survey of lensing clusters should provide a unique census of sources responsible for the reionization in a representative volume at z ~ 4-7.

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arXiv2015

Extended Lyman alpha haloes around individual high-redshift galaxies revealed by MUSE

We report the detection of extended Ly alpha emission around individual star-forming galaxies at redshifts z = 3-6 in an ultradeep exposure of the Hubble Deep Field South obtained with MUSE on the ESO-VLT. The data reach a limiting surface brightness (1sigma) of ~1 x 10^-19 erg s^-1 cm^-2 arcsec^-2 in azimuthally averaged radial profiles, an order of magnitude improvement over previous narrowband imaging. Our sample consists of 26 spectroscopically confirmed Ly alpha-emitting, but mostly continuum-faint (m_AB >~ 27) galaxies. In most objects the Ly alpha emission is considerably more extended than the UV continuum light. While 5 of the faintest galaxies in the sample show no significantly detected Ly alpha haloes, the derived upper limits suggest that this is just due to insufficient S/N. Ly alpha haloes therefore appear to be (nearly) ubiquitous even for low-mass (~10^8-10^9 M_sun) star-forming galaxies at z>3. We decompose the Ly alpha emission of each object into a compact `continuum-like' and an extended halo component, and infer sizes and luminosities of the haloes. The extended Ly alpha emission approximately follows an exponential surface brightness distribution with a scale length of a few kpc. While these haloes are thus quite modest in terms of their absolute sizes, they are larger by a factor of 5-15 than the corresponding rest-frame UV continuum sources as seen by HST. They are also much more extended, by a factor ~5, than Ly alpha haloes around low-redshift star-forming galaxies. Between ~40% and >90% of the observed Ly alpha flux comes from the extended halo component, with no obvious correlation of this fraction with either the absolute or the relative size of the Ly alpha halo. Our observations provide direct insights into the spatial distribution of at least partly neutral gas residing in the circumgalactic medium of low to intermediate mass galaxies at z > 3.

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arXiv2014

The MUSE 3D view of the Hubble Deep Field South

We observed the Hubble Deep Field South with the new panoramic integral field spectrograph MUSE that we built and just commissioned at the VLT. The data cube resulting from 27 hours of integration covers one arcmin^2 field of view at an unprecedented depth with a 1 sigma emission line surface brightness limit of 1x$10^{-19}$ erg/s/cm$^2$/arcsec$^2$ and contains ~90,000 spectra. We present the combined and calibrated data cube, and we perform a first-pass analysis of the sources detected in the HDF-S imaging. We measured the redshifts of 189 sources up to a magnitude F814W = 29.5, increasing by more than an order of magnitude the number of known spectroscopic redshifts in this field. We also discovered 26 Lya emitting galaxies which are not detected in the HST WFPC2 deep broad band images. The intermediate spectral resolution of 2.3Å allows us to separate resolved asymmetric Lya emitters, [O II] emitters, and C III] emitters and the large instantaneous wavelength range of 4500Å helps to identify single emission lines. We also show how the three dimensional information of MUSE helps to resolve sources which are confused at ground-based image quality. Overall, secure identifications are provided for 83% of the 227 emission line sources detected in the MUSE data cube and for 32% of the 586 sources identified in the HST catalog of Casertano et al 2000. The overall redshift distribution is fairly flat to z=6.3, with a reduction between z=1.5 to 2.9, in the well-known redshift desert. The field of view of MUSE also allowed us to detect 17 groups within the field. We checked that the number counts of [O II] and Ly-a emitters are roughly consistent with predictions from the literature. Using two examples we demonstrate that MUSE is able to provide exquisite spatially resolved spectroscopic information on intermediate redshift galaxies present in the field.

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arXiv2013

Galaxy Formation with local photoionisation feedback I. Methods

We present a first study of the effect of local photoionising radiation on gas cooling in smoothed particle hydrodynamics simulations of galaxy formation. We explore the combined effect of ionising radiation from young and old stellar populations. The method computes the effect of multiple radiative sources using the same tree algorithm used for gravity, so it is computationally efficient and well resolved. The method foregoes calculating absorption and scattering in favour of a constant escape fraction for young stars to keep the calculation efficient enough to simulate the entire evolution of a galaxy in a cosmological context to the present day. This allows us to quantify the effect of the local photoionisation feedback through the whole history of a galaxy`s formation. The simulation of a Milky Way like galaxy using the local photoionisation model forms ~ 40 % less stars than a simulation that only includes a standard uniform background UV field. The local photoionisation model decreases star formation by increasing the cooling time of the gas in the halo and increasing the equilibrium temperature of dense gas in the disc. Coupling the local radiation field to gas cooling from the halo provides a preventive feedback mechanism which keeps the central disc light and produces slowly rising rotation curves without resorting to extreme feedback mechanisms. These preliminary results indicate that the effect of local photoionising sources is significant and should not be ignored in models of galaxy formation.

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