arXiv subjects

Michael Maseda

Publications and source records attributed to Michael Maseda.

At least 55 records · Page 3Linked to original sources

arXiv2021

EMPRESS. IV. Extremely Metal-Poor Galaxies (EMPGs) Including Very Low-Mass Primordial Systems with M*=10^4--10^5 M_sun and 2--3% (O/H)_sun: High (Fe/O) Suggestive of Metal Enrichment by Hypernovae/Pair-Instability Supernovae

We present Keck/LRIS follow-up spectroscopy for 13 photometric candidates of extremely metal poor galaxies (EMPGs) selected by a machine-learning technique applied to the deep (~26 AB mag) optical and wide-area (~500 deg^2) Subaru imaging data in the EMPRESS survey. Nine out of the 13 candidates are EMPGs with an oxygen abundance (O/H) less than ~10% solar value (O/H)_sun, and four sources are contaminants of moderately metal-rich galaxies or no emission-line objects. Notably, two out of the nine EMPGs have extremely-low stellar masses and oxygen abundances of 5*10^4--7*10^5 M_sun and 2--3% (O/H)_sun, respectively. With a sample of five EMPGs with (Fe/O) measurements, two (three) of which are taken from this study (the literature), we confirm that two EMPGs with the lowest (O/H) ratios of ~2% (O/H)_sun show high (Fe/O) ratios of ~0.1, close to the solar abundance ratio. Comparing galaxy chemical enrichment models, we find that the two EMPGs cannot be explained by a scenario of metal-poor gas accretion/episodic star-formation history due to their low (N/O) ratios. We conclude that the two EMPGs can be reproduced by an inclusion of bright hypernovae and/or hypothetical pair-instability supernovae (SNe) preferentially produced in a metal-poor environment. This conclusion implies that primordial galaxies at z~10 could have a high abundance of Fe that is not originated from Type Ia SNe with delays, and that Fe may not serve as a cosmic clock for primordial galaxies.

astro-ph.GA↗

arXiv2021

The MUSE Extremely Deep Field: Evidence for SFR-induced cores in dark-matter dominated galaxies at z=1

Disc-halo decomposition on rotationally supported star-forming galaxies (SFGs) at $z>1$ are often limited to massive galaxies ($M_\star>10^{10}~M_\odot$) and rely on either deep Integral Field Spectroscopy data or stacking analyses. We present a study of the dark matter (DM) content of nine $z\approx1$ SFGs selected Using the brightest [OII] emitters in the deepest Multi-Unit Spectrograph Explorer (MUSE) field to date, namely the 140hr MUSE Extremely Deep Field, we perform disk-halo decompositions on 9 low-mass SFGs (with $10^{8.5} 10^{10}~M_\odot$. The DM halos show constant surface densities of $\sim100~M_\odot$ pc$^{-2}$. Half of the sample shows a strong preference for cored over cuspy DM profiles. The presence of DM cores appears to be related to galaxies with stellar-to-halo mass $\log M_\star/M_{\rm vir}\approx-2.5$. In addition, the cuspiness of the DM profiles is found to be a strong function of the recent star-formation activity. Both of these results are interpreted as evidence for feedback-induced core formation in the Cold Dark Matter context.

astro-ph.GA↗

arXiv2021

MUSEQuBES: Characterizing the circumgalactic medium of redshift $\approx3.3$ Ly$α$ emitters

We present the first characterization of the circumgalactic medium of Ly$α$ emitters (LAEs), using a sample of 96 $z\approx3.3$ LAEs detected with the VLT/MUSE in fields centered on 8 bright background quasars. The LAEs have low Ly$α$ luminosities ($\sim 10^{42}\,\text{erg}\,\text{s}^{-1}$) and star formation rates (SFRs) $\sim 1~\text{M}_\odot\,\text{yr}^{-1}$, which for main sequence galaxies corresponds to stellar masses of only $\sim 10^{8.6}\,\text{M}_\odot$. The median transverse distance between the LAEs and the quasar sightlines is 165 proper kpc (pkpc). We stacked the high-resolution quasar spectra and measured significant excess HI and CIV absorption near the LAEs out to 500 $\text{km}\,\text{s}^{-1}$ and at least $\approx 250$ pkpc (corresponding to $\approx 7$ virial radii). At $\lesssim 30~\text{km}\,\text{s}^{-1}$ from the galaxies the median HI and CIV optical depths are enhanced by an order of magnitude. The absorption is significantly stronger around the $\approx 1/3$ of our LAEs that are part of `groups', which we attribute to the large-scale structures in which they are embedded. We do not detect any strong dependence of either the HI or CIV absorption on transverse distance (over the range $\approx 50-250$ pkpc), redshift, or the properties of the Ly$α$ emission line (luminosity, full width at half maximum, or equivalent width). However, for HI, but not CIV, the absorption at $\lesssim 100\,\text{km}\,\text{s}^{-1}$ from the LAE does increase with the SFR. This suggests that LAEs surrounded by more HI tend to have higher SFRs.

astro-ph.GA↗

arXiv2021

Dynamical modelling of the twisted galaxy PGC 046832

We analyse VLT/MUSE observations of PGC 046832, the brightest cluster galaxy of Abell 3556. The velocity structure of this galaxy is startling and shows two reversals in sign along the minor axis, and one along the major axis. We use triaxial Schwarzschild models to infer the intrinsic shape, central black hole mass and orbit distribution of this galaxy. The shape determination suggests that the galaxy is highly triaxial in the centre (almost prolate) but has a low triaxiality (almost oblate) in the outer parts. The orbit distribution of the best-fit Schwarzschild model shows that the kinematic reversal along the projected minor axis is driven by a slight asymmetry in the distribution and amount of long axis tubes in the inner parts. The kinematic reversals along the projected major axis are driven by a high fraction of counter-rotating orbits at intermediate radii in the galaxy. Using chemical tagging of orbits in the Schwarzschild model, we do not find evidence for any association of these orbits with specific stellar population parameters. Although the inner part of the galaxy almost certainty formed through one or more dry mergers producing the prolate shape, the outer parts are consistent with both accretion and in situ formation. While axisymmetric models suggests the presence of a supermassive black hole with mass $\sim 6 \times 10^9$M$_{\odot}$ and $\sim 10^{10}$M$_{\odot}$ (with Schwarzschild and Jeans modelling, resp), triaxial Schwarzschild models provide only an upper limit of $\sim 2 \times 10^9$M$_{\odot}$.

astro-ph.GA↗

arXiv2021

Measuring the average molecular gas content of star-forming galaxies at $z=3-4$

We study the molecular gas content of 24 star-forming galaxies at $z=3-4$, with a median stellar mass of $10^{9.1}$ M$_{\odot}$, from the MUSE Hubble Ultra Deep Field (HUDF) Survey. Selected by their Lyman-alpha-emission and H-band magnitude, the galaxies show an average EW $\approx 20$ angstrom, below the typical selection threshold for Lyman Alpha Emitters (EW $> 25$ angstrom), and a rest-frame UV spectrum similar to Lyman Break Galaxies. We use rest-frame optical spectroscopy from KMOS and MOSFIRE, and the UV features observed with MUSE, to determine the systemic redshifts, which are offset from Lyman alpha by 346 km s$^{-1}$, with a 100 to 600 km s$^{-1}$ range. Stacking CO(4-3) and [CI](1-0) (and higher-$J$ CO lines) from the ALMA Spectroscopic Survey of the HUDF (ASPECS), we determine $3σ$ upper limits on the line luminosities of $4.0\times10^{8}$ K km s$^{-1}$pc$^{2}$ and $5.6\times10^{8}$ K km s$^{-1}$pc$^{2}$, respectively (for a 300 km s$^{-1}$ linewidth). Stacking the 1.2 mm and 3 mm dust continuum flux densities, we find a $3σ$ upper limits of 9 $μ$Jy and $1.2$ $μ$Jy, respectively. The inferred gas fractions, under the assumption of a 'Galactic' CO-to-H$_{2}$ conversion factor and gas-to-dust ratio, are in tension with previously determined scaling relations. This implies a substantially higher $α_{\rm CO} \ge 10$ and $δ_{\rm GDR} \ge 1200$, consistent with the sub-solar metallicity estimated for these galaxies ($12 + \log(O/H) \approx 7.8 \pm 0.2$). The low metallicity of $z \ge 3$ star-forming galaxies may thus make it very challenging to unveil their cold gas through CO or dust emission, warranting further exploration of alternative tracers, such as [CII].

astro-ph.GA↗

arXiv2021

The MUSE Extremely Deep Field: the Cosmic Web in Emission at High Redshift

We report the discovery of diffuse extended Ly-alpha emission from redshift 3.1 to 4.5, tracing cosmic web filaments on scales of 2.5-4 comoving Mpc. These structures have been observed in overdensities of Ly-alpha emitters in the MUSE Extremely Deep Field, a 140 hour deep MUSE observation located in the Hubble Ultra Deep Field. Among the 22 overdense regions identified, 5 are likely to harbor very extended Ly-alpha emission at high significance with an average surface brightness of $\mathrm{5 \times 10^{-20} erg s^{-1} cm^{-2} arcsec^{-2}}$. Remarkably, 70% of the total Ly-alpha luminosity from these filaments comes from beyond the circumgalactic medium of any identified Ly-alpha emitters. Fluorescent Ly-alpha emission powered by the cosmic UV background can only account for less than 34% of this emission at z$\approx$3 and for not more than 10% at higher redshift. We find that the bulk of this diffuse emission can be reproduced by the unresolved Ly-alpha emission of a large population of ultra low luminosity Ly-alpha emitters ($\mathrm{<10^{40} erg s^{-1}}$), provided that the faint end of the Ly-alpha luminosity function is steep ($α\lessapprox -1.8$), it extends down to luminosities lower than $\mathrm{10^{38} - 10^{37} erg s^{-1}}$ and the clustering of these Ly-alpha emitters is significant (filling factor $< 1/6$). If these Ly-alpha emitters are powered by star formation, then this implies their luminosity function needs to extend down to star formation rates $\mathrm{< 10^{-4} M_\odot yr^{-1}}$. These observations provide the first detection of the cosmic web in Ly-alpha emission in typical filamentary environments and the first observational clue for the existence of a large population of ultra low luminosity Ly-alpha emitters at high redshift.

astro-ph.CO↗

arXiv2021

An Atlas of MUSE Observations towards Twelve Massive Lensing Clusters

Spectroscopic surveys of massive galaxy clusters reveal the properties of faint background galaxies, thanks to the magnification provided by strong gravitational lensing. We present a systematic analysis of integral-field-spectroscopy observations of 12 massive clusters, conducted with the Multi Unit Spectroscopic Explorer (MUSE). All data were taken under very good seeing conditions (0.6") in effective exposure times between two and 15 hrs per pointing, for a total of 125 hrs. Our observations cover a total solid angle of ~23 arcmin$^2$ in the direction of clusters, many of which were previously studied by the MACS, Frontier Fields, GLASS and CLASH programs. The achieved emission line detection limit at 5$σ$ for a point source varies between (0.77--1.5)$\times$10$^{-18}$ erg\,s$^{-1}$\,cm$^{-2}$ at 7000Å. We present our developed strategy to reduce these observational data, detect sources and determine their redshifts. We construct robust mass models for each cluster to further confirm our redshift measurements using strong-lensing constraints, and identify a total of 312 strongly lensed sources producing 939 multiple images. The final redshift catalogs contain more than 3300 robust redshifts, of which 40\% are for cluster members and $\sim$30\% for lensed Lyman-$α$ emitters. 14\% of all sources are line emitters not seen in the available HST images, even at the depth of the FFs ($\sim29$ AB). We find that the magnification distribution of the lensed sources in the high-magnification regime ($μ{=}$ 2--25) follows the theoretical expectation of $N(z)\proptoμ^{-2}$. The quality of this dataset, number of lensed sources, and number of strong-lensing constraints enables detailed studies of the physical properties of both the lensing cluster and the background galaxies. The full data products from this work are made available to the community. [abridged]

astro-ph.GA↗

arXiv2020

MUSEQuBES: Calibrating the redshifts of Ly α emitters using stacked circumgalactic medium absorption profiles

Lyman$-α$ (Ly$α$) emission lines are typically found to be redshifted with respect to the systemic redshifts of galaxies, likely due to resonant scattering of Ly$α$ photons. Here we measure the average velocity offset for a sample of 96 $z\approx3.3$ Ly$α$ emitters (LAEs) with a median Ly$α$ flux (luminosity) of $\approx 10^{-17}~\rm erg~cm^{-2}~s^{-1}$ ($\approx10^{42}~\rm erg~s^{-1}$) and a median star formation rate (SFR) of $\approx1.3 \rm M_{\odot} yr^{-1}$ (not corrected for possible dust extinction), detected by the Multi-Unit Spectroscopic Explorer as part of our MUSEQuBES circumgalactic medium (CGM) survey. By postulating that the stacked CGM absorption profiles of these LAEs, probed by 8 background quasars, must be centered on the systemic redshift, we measure an average velocity offset, V$_{\rm offset} = 171 \pm 8$ $\rm km s^{-1}$, between the Ly$α$ emission peak and the systemic redshift. The observed V$_{\rm offset}$ is lower by factors of $\approx1.4$ and $\approx2.6$ compared to the velocity offsets measured for narrow-band selected LAEs and Lyman break galaxies, respectively, which probe galaxies with higher masses and SFRs. Consistent with earlier studies based on direct measurements for individual objects, we find that the V$_{\rm offset}$ is correlated with the full width at half-maximum of the red peak of the Ly$α$ line, and anti-correlated with the rest-frame equivalent width. Moreover, we find that $V_{\rm offset}$ is correlated with SFR with a sub-linear scaling relation, V$_{\rm offset}\propto \rm SFR^{0.16\pm0.03}$. Adopting the mass scaling for main sequence galaxies, such a relation suggests that V$_{\rm offset}$ scales with the circular velocity of the dark matter halos hosting the LAEs.

astro-ph.GA↗

arXiv2020

The nature of CR7 revealed with MUSE: a young starburst powering extended Lyman-$α$ emission at z=6.6

CR7 is among the most luminous Lyman-$α$ emitters (LAEs) known at $z = 6.6$ and consists of at least three UV components that are surrounded by Lyman-$α$ (Ly$α$) emission. Previous studies have suggested that it may host an extreme ionising source. Here, we present deep integral field spectroscopy of CR7 with VLT/MUSE. We measure extended emission with a similar halo scale length as typical LAEs at $z\approx5$. CR7's Ly$α$ halo is clearly elongated along the direction connecting the multiple components, likely tracing the underlying gas distribution. The Ly$α$ emission originates almost exclusively from the brightest UV component, but we also identify a faint kinematically distinct Ly$α$ emitting region nearby a fainter component. Combined with new near-infrared data, the MUSE data show that the rest-frame Ly$α$ equivalent width (EW) is $\approx100$ Å. This is a factor four higher than the EW measured in low-redshift analogues with carefully matched Ly$α$ profiles (and thus arguably HI column density), but this EW can plausibly be explained by star formation. Alternative scenarios requiring AGN powering are also disfavoured by the narrower and steeper Ly$α$ spectrum and much smaller IR to UV ratio compared to obscured AGN in other Ly$α$ blobs. CR7's Ly$α$ emission, while extremely luminous, resembles the emission in more common LAEs at lower redshifts very well and is likely powered by a young metal poor starburst.

astro-ph.GA↗

arXiv2020

The MUSE Hubble Ultra Deep Field Survey XIV. The evolution of the Lya emitter fraction from z=3 to z=6

The Lya emitter (LAE) fraction, X_LAE, is a potentially powerful probe of the evolution of the intergalactic neutral hydrogen gas fraction. However, uncertainties in the measurement of X_LAE are still debated. Thanks to deep data obtained with MUSE, we can measure the evolution of X_LAE homogeneously over a wide redshift range of z~3-6 for UV-faint galaxies (down to M_1500~-17.75). This is significantly fainter than in former studies, and allows us to probe the bulk of the population of high-z star-forming galaxies. We construct a UV-complete photo-redshift sample following UV luminosity functions and measure the Lya emission with MUSE using the second data release from the MUSE HUDF Survey. We derive the redshift evolution of X_LAE for M_1500 in [-21.75;-17.75] for the first time with a equivalent width range EW(Lya)>=65 A and find low values of X_ LAE<~30% at z<~6. For M_1500 in [-20.25;-18.75] and EW(Lya)<~25 A, our X_LAE values are consistent with those in the literature within 1sigma at z<~5, but our median values are systematically lower than reported values over the whole redshift range. In addition, we do not find a significant dependence of X_LAE on M_1500 for EW(Lya)>~50 A at z~3-4, in contrast with previous work. The differences in X_LAE mainly arise from selection biases for Lyman Break Galaxies (LBGs) in the literature: UV-faint LBGs are more easily selected if they have strong Lya emission, hence X_LAE is biased towards higher values. Our results suggest either a lower increase of X_LAE towards z~6 than previously suggested, or even a turnover of X_LAE at z~5.5, which may be the signature of a late or patchy reionization process. We compared our results with predictions from a cosmological galaxy evolution model. We find that a model with a bursty star formation (SF) can reproduce our observed X_LAE much better than models where SF is a smooth function of time.

astro-ph.GA↗

arXiv2020

The MUSE Hubble Ultra Deep Field Survey XIII. Spatially resolved spectral properties of Lyman alpha haloes around star-forming galaxies at z > 3

We present spatially resolved maps of six individually-detected Lyman alpha haloes (LAHs) as well as a first statistical analysis of the Lyman alpha (Lya) spectral signature in the circum-galactic medium of high-redshift star-forming galaxies using MUSE. Our resolved spectroscopic analysis of the LAHs reveals significant intrahalo variations of the Lya line profile. Using a three-dimensional two-component model for the Lya emission, we measure the full width at half maximum (FWHM), the peak velocity shift and the asymmetry of the Lya line in the core and in the halo of 19 galaxies. We find that the Lya line shape is statistically different in the halo compared to the core for ~40% of our galaxies. Similarly to object-by-object based studies and a recent resolved study using lensing, we find a correlation between the peak velocity shift and the width of the Lya line both at the interstellar and circum-galactic scales. While there is a lack of correlation between the spectral properties and the spatial scale lengths of our LAHs, we find a correlation between the width of the line in the LAH and the halo flux fraction. Interestingly, UV bright galaxies show broader, more redshifted and less asymmetric Lya lines in their haloes. The most significant correlation found is for the FWHM of the line and the UV continuum slope of the galaxy, suggesting that the redder galaxies have broader Lya lines. The generally broad and red line shapes found in the halo component suggests that the Lya haloes are powered either by scattering processes through an outflowing medium, fluorescent emission from outflowing cold clumps of gas, or a mix of both. Considering the large diversity of the Lya line profiles observed in our sample and the lack of strong correlation, the interpretation of our results is still broadly open and underlines the need for realistic spatially resolved models of the LAHs.

astro-ph.GA↗

arXiv2019

The ALMA Spectroscopic Survey in the HUDF: Nature and physical properties of gas-mass selected galaxies using MUSE spectroscopy

We discuss the nature and physical properties of gas-mass selected galaxies in the ALMA spectroscopic survey (ASPECS) of the Hubble Ultra Deep Field (HUDF). We capitalize on the deep optical integral-field spectroscopy from the MUSE HUDF Survey and multi-wavelength data to uniquely associate all 16 line-emitters, detected in the ALMA data without preselection, with rotational transitions of carbon monoxide (CO). We identify ten as CO(2-1) at $1 < z < 2$, five as CO(3-2) at $2 < z < 3$ and one as CO(4-3) at $z = 3.6$. Using the MUSE data as a prior, we identify two additional CO(2-1)-emitters, increasing the total sample size to 18. We infer metallicities consistent with (super-)solar for the CO-detected galaxies at $z \le 1.5$, motivating our choice of a Galactic conversion factor between CO luminosity and molecular gas mass for these galaxies. Using deep Chandra imaging of the HUDF, we determine an X-ray AGN fraction of 20% and 60% among the CO-emitters at $z \sim 1.4$ and $z \sim 2.6$, respectively. Being a CO-flux limited survey, ASPECS-LP detects molecular gas in galaxies on, above and below the main sequence (MS) at $z \sim 1.4$. For stellar masses $\ge 10^{10} (10^{10.5})$ M$_{\odot}$, we detect about 40% (50%) of all galaxies in the HUDF at $1 < z < 2$ ($2 < z < 3$). The combination of ALMA and MUSE integral-field spectroscopy thus enables an unprecedented view on MS galaxies during the peak of galaxy formation.

astro-ph.GA↗

arXiv2019

Exploring HeII$λ$1640 emission line properties at ${z\sim2-4}$

Deep optical spectroscopic surveys of galaxies provide us a unique opportunity to investigate rest-frame ultra-violet (UV) emission line properties of galaxies at ${z \sim 2-4.5}$. Here we combine VLT/MUSE Guaranteed Time Observations of the Hubble Deep Field South, Ultra Deep Field, COSMOS, and several quasar fields with other publicly available data from VLT/VIMOS and VLT/FORS2 to construct a catalogue of HeII$λ$1640 emitters at ${z\sim2}$. The deepest areas of our MUSE pointings reach a ${3σ}$ line flux limit of 3.1${\times}$10-19 erg/ s/ cm$^2$. After discarding broad line active galactic nuclei we find 13 HeII$λ$1640 detections from MUSE with a median MUV = $-20.1$ and 21 tentative HeII$λ$1640 detections from other public surveys. Excluding Ly$α$, all except two galaxies in our sample show at least one other rest-UV emission line, with CIII]$λ$1907,$λ$1909 being the most prominent. We use multi-wavelength data available in the Hubble legacy fields to derive basic galaxy properties of our sample via spectral energy distribution fitting techniques. Taking advantage of the high quality spectra obtained by MUSE (${\sim10 - 30}$h of exposure time per pointing), we use photo-ionisation models to study the rest-UV emission line diagnostics of the HeII$λ$1640 emitters. Line ratios of our sample can be reproduced by moderately sub-solar photo-ionisation models, however, we find that including effects of binary stars lead to degeneracies in most free parameters. Even after considering extra ionising photons produced by extreme sub-solar metallicity binary stellar models, photo-ionisation models are unable to reproduce rest-frame HeII$λ$1640 equivalent widths (${\sim}$ 0.2 - 10 A), thus additional mechanisms are necessary in models to match the observed HeII$λ$1640 properties.

astro-ph.GA↗

arXiv2019

The MUSE Atlas of Disks (MAD): Resolving Star Formation Rates and Gas Metallicities on < 100pc Scales

We study the physical properties of the ionized gas in local disks using the sample of 38 nearby $\sim10^{8.5-11.2}$M$_\odot$ Star-Forming Main Sequence (SFMS) galaxies observed so far as part of the MUSE Atlas of Disks (MAD). Specifically, we use all strong emission lines in the MUSE wavelength range 4650-9300 Å to investigate the resolved ionized gas properties on $\sim$100 pc scales. This spatial resolution enables us to disentangle HII regions from the Diffuse Ionized Gas (DIG) in the computation of gas metallicities and Star Formation Rates (SFRs) of star forming regions. The gas metallicities generally decrease with radius. The metallicity of the HII regions is on average $\sim$0.1 dex higher than that of the DIG, but the metallicity radial gradient in both components is similar. The mean metallicities within the inner galaxy cores correlate with the total stellar mass of the galaxies. On our <100 pc scales, we find two correlations previously reported at kpc scales: a spatially resolved Mass-Metallicity Relation (RMZR) and a spatially resolved SFMS (RSFMS). We find no secondary dependency of the RMZR with the SFR density. We find that both resolved relations have a local origin, as they do not depend on the total stellar mass. The observational results of this paper are consistent with the inside-out scenario for the growth of galactic disks.

astro-ph.GA↗

arXiv2018

Molecular Gas Contents and Scaling Relations for Massive Passive Galaxies at Intermediate Redshifts from the LEGA-C Survey

A decade of study has established that the molecular gas properties of star-forming galaxies follow coherent scaling relations out to z~3, suggesting remarkable regularity of the interplay between molecular gas, star formation, and stellar growth. Passive galaxies, however, are expected to be gas-poor and therefore faint, and thus little is known about molecular gas in passive galaxies beyond the local universe. Here we present deep Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO(2-1) emission in 8 massive (Mstar ~ 10^11 Msol) galaxies at z~0.7 selected to lie a factor of 3-10 below the star-forming sequence at this redshift, drawn from the Large Early Galaxy Astrophysics Census (LEGA-C) survey. We significantly detect half the sample, finding molecular gas fractions <~0.1. We show that the molecular and stellar rotational axes are broadly consistent, arguing that the molecular gas was not accreted after the galaxies became quiescent. We find that scaling relations extrapolated from the star-forming population over-predict both the gas fraction and gas depletion time for passive objects, suggesting the existence of either a break or large increase in scatter in these relations at low specific star formation rate. Finally, we show that the gas fractions of the passive galaxies we have observed at intermediate redshifts are naturally consistent with evolution into local massive early-type galaxies by continued low-level star formation, with no need for further gas accretion or dynamical stabilization of the gas reservoirs in the intervening 6 billion years.

astro-ph.GA↗

arXiv2017

The MUSE Hubble Ultra Deep Field Survey VIII : Extended Lyman-alpha haloes around high-redshift star-forming galaxies

We report the detection of extended Lyman-alpha (Lya) haloes around 145 individual star-forming galaxies at redshifts 3 M_{UV}> -22) Lya emitters (LAEs). Using a 2D, two-component decomposition of Lya emission assuming circular exponential distributions, we measure scale lengths and luminosities of Lya haloes. We find that 80% of our objects having reliable Lya halo measurements show Lya emission that is significantly more extended than the UV continuum detected by HST (by a factor ~4 to >20). The median exponential scale length of the Lya haloes in our sample is ~4.5 kpc. By comparing the maximal detected extent of the Lya emission with the predicted dark matter halo virial radii of simulated galaxies, we show that the detected Lya emission of our selected sample of LAEs probes a significant portion of the cold circum-galactic medium (CGM) of these galaxies (>50% in average). This result shows that there must be significant HI reservoirs in the CGM and reinforces the idea that Lya haloes are ubiquitous around high-redshift Lya emitting galaxies. Our characterization of the Lya haloes indicates that the majority of the Lya flux comes from the halo (~65%) and that their scale lengths seem to be linked to the UV properties of the galaxies. We do not observe a significant Lya halo size evolution with redshift. We also find that the Lya lines cover a large range of full width at half maximum (FWHM) from 118 to 512 km/s. While the FWHM does not seem to be correlated to the Lya scale length, most compact Lya haloes and those that are not detected with high significance tend to have narrower Lya profiles. Finally, we investigate the origin of the extended Lya emission but we conclude that our data do not allow us to disentangle the possible processes.

astro-ph.GA↗

arXiv2017

The MUSE Hubble Ultra Deep Field Survey: VII. FeII* Emission in Star-Forming Galaxies

Non-resonant FeII* 2365, 2396, 2612, 2626 emission can potentially trace galactic winds in emission and provide useful constraints to wind models. From the 3'x3' mosaic of the Hubble Ultra Deep Field (UDF) obtained with the VLT/MUSE integral field spectrograph, we identify a statistical sample of 40 FeII* emitters and 50 MgII 2796, 2803 emitters from a sample of 271 [OII] 3726, 3729 emitters with reliable redshifts from z = 0.85 - 1.5 down to 2E-18 (3 sigma) ergs/s/cm^2 (for [OII]), covering the stellar mass range 10^8 - 10^11 Msun. The FeII* and MgII emitters follow the galaxy main sequence, but with a clear dichotomy. Galaxies with masses below 10^9 Msun and star formation rates (SFRs) of <1 Msun/year have MgII emission without accompanying FeII* emission, whereas galaxies with masses above 10^10 Msun and SFRs >10 Msun/year have FeII* emission without accompanying MgII emission. Between these two regimes, galaxies have both MgII and FeII* emission, typically with MgII P-Cygni profiles. Indeed, the MgII profile shows a progression along the main sequence from pure emission to P-Cygni profiles to strong absorption, due to resonant trapping. Combining the deep MUSE data with HST ancillary information, we find that galaxies with pure MgII emission profiles have lower star formation rate surface densities than those with either MgII P-Cygni profiles or FeII* emission. These spectral signatures produced through continuum scattering and fluorescence, MgII P-Cygni profiles and FeII* emission, are better candidates for tracing galactic outflows than pure MgII emission, which may originate from HII regions. We compare the absorption and emission rest-frame equivalent widths for pairs of FeII transitions to predictions from outflow models and find that the observations consistently have less total re-emission than absorption, suggesting either dust extinction or non-isotropic outflow geometries.

astro-ph.GA↗

arXiv2017

The MUSE Hubble Ultra Deep Field Survey: I. Survey description, data reduction and source detection

We present the MUSE Hubble Ultra Deep Survey, a mosaic of nine MUSE fields covering 90\% of the entire HUDF region with a 10-hour deep exposure time, plus a deeper 31-hour exposure in a single 1.15 arcmin2 field. The improved observing strategy and advanced data reduction results in datacubes with sub-arcsecond spatial resolution (0.65 arcsec at 7000 A) and accurate astrometry (0.07 arcsec rms). We compare the broadband photometric properties of the datacubes to HST photometry, finding a good agreement in zeropoint up to mAB=28 but with an increasing scatter for faint objects. We have investigated the noise properties and developed an empirical way to account for the impact of the correlation introduced by the 3D drizzle interpolation. The achieved 3 sigma emission line detection limit for a point source is 1.5 and 3.1 10-19 erg.s-1.cm-2 for the single ultra-deep datacube and the mosaic, respectively. We extracted 6288 sources using an optimal extraction scheme that takes the published HST source locations as prior. In parallel, we performed a blind search of emission line galaxies using an original method based on advanced test statistics and filter matching. The blind search results in 1251 emission line galaxy candidates in the mosaic and 306 in the ultradeep datacube, including 72 sources without HST counterparts (mAB>31). In addition 88 sources missed in the HST catalog but with clear HST counterparts were identified. This data set is the deepest spectroscopic survey ever performed. In just over 100 hours of integration time, it provides nearly an order of magnitude more spectroscopic redshifts compared to the data that has been accumulated on the UDF over the past decade. The depth and high quality of these datacubes enables new and detailed studies of the physical properties of the galaxy population and their environments over a large redshift range.

astro-ph.GA↗