arXiv subjects

S. Morris

Publications and source records attributed to S. Morris.

14 recordsLinked to original sources

arXiv2020

MOSAIC on the ELT: high-multiplex spectroscopy to unravel the physics of stars and galaxies from the dark ages to the present-day

The powerful combination of the cutting-edge multi-object spectrograph MOSAIC with the world largest telescope, the ELT, will allow us to probe deeper into the Universe than was possible. MOSAIC is an extremely efficient instrument in providing spectra for the numerous faint sources in the Universe, including the very first galaxies and sources of cosmic reionization. MOSAIC has a high multiplex in the NIR and in the VIS, in addition to multi-Integral Field Units (Multi-IFUs) in NIR. As such it is perfectly suited to carry out an inventory of dark matter (from rotation curves) and baryons in the cool-warm gas phases in galactic haloes at z=3-4. MOSAIC will enable detailed maps of the intergalactic medium at z=3, the evolutionary history of dwarf galaxies during a Hubble time, the chemistry directly measured from stars up to several Mpc. Finally, it will measure all faint features seen in cluster gravitational lenses or in streams surrounding nearby galactic halos, providing MOSAIC to be a powerful instrument with an extremely large space of discoveries. The preliminary design of MOSAIC is expected to begin next year, and its level of readiness is already high, given the instrumental studies made by the team.

astro-ph.GA↗

arXiv2019

Simulating MOS science on the ELT: Ly$\alpha$ forest tomography

Mapping of the large-scale structure through cosmic time has numerous applications in the studies of cosmology and galaxy evolution. At $z > 2$, the structure can be traced by the neutral intergalactic medium (IGM) by way of observing the Ly$\alpha$, forest towards densely-sampled lines-of-sight of bright background sources, such as quasars and star forming galaxies. We investigate the scientific potential of MOSAIC, a planned multi-object spectrograph on the European Extremely Large Telescope (ELT), for the 3D mapping of the IGM at $z \gtrsim 3$. We simulate a survey of $3 \lesssim z \lesssim 4$ galaxies down to a limiting magnitude of $m_{r}\sim 25.5$ mag in an area of 1 degree$^2$ in the sky. Galaxies and their spectra (including the line-of-sight Ly$\alpha$ absorption) are taken from the lightcone extracted from the Horizon-AGN cosmological hydrodynamical simulation. The quality of the reconstruction of the original density field is studied for different spectral resolutions and signal-to-noise ratios of the spectra. We demonstrate that the minimum $S/N$ (per resolution element) of the faintest galaxies that such survey has to reach is $S/N = 4$. We show that a survey with such sensitivity enables a robust extraction of cosmic filaments and the detection of the theoretically-predicted galaxy stellar mass and star-formation rate gradients towards filaments. By simulating the realistic performance of MOSAIC we obtain $S/N(T_{\rm obs}, R, m_{r})$ scaling relations. We estimate that $\lesssim 35~(65)$ nights of observation time are required to carry out the survey with the instrument's high multiplex mode and with the spectral resolution of $R=1000~(2000)$. A survey with a MOSAIC-concept instrument on the ELT is found to enable the mapping of the IGM at $z > 3$ on Mpc scales, and as such will be complementary to and competitive with other planned IGM tomography surveys. [abridged]

astro-ph.GA↗

arXiv2019

Optical integral field spectroscopy of intermediate redshift infrared bright galaxies

The extreme infrared (IR) luminosity of local luminous and ultra-luminous IR galaxies (U/LIRGs; 11 < log LIR /Lsun < 12 and log LIR /Lsun > 12, respectively) is mainly powered by star-formation processes triggered by mergers or interactions. While U/LIRGs are rare locally, at z > 1, they become more common, they dominate the star-formation rate (SFR) density, and a fraction of them are found to be normal disk galaxies. Therefore, there must be an evolution of the mechanism triggering these intense starbursts with redshift. To investigate this evolution, we present new optical SWIFT integral field spectroscopic H{\alpha}+[NII] observations of a sample of 9 intermediate-z (0.2 < z < 0.4) U/LIRG systems selected from Herschel 250{\mu}m observations. The main results are the following: (a) the ratios between the velocity dispersion and the rotation curve amplitude indicate that 10-25% (1-2 out of 8) might be compatible with being isolated disks while the remaining objects are interacting/merging systems; (b) the ratio between un-obscured and obscured SFR traced by H{\alpha} and LIR, respectively, is similar in both local and these intermediate-z U/LIRGs; and (c) the ratio between 250{\mu}m and the total IR luminosities of these intermediate-z U/LIRGs is higher than that of local U/LIRGs with the same LIR . This indicates a reduced dust temperature in these intermediate-z U/LIRGs. This, together with their already measured enhanced molecular gas content, suggests that the interstellar medium conditions are different in our sample of intermediate-z galaxies when compared to local U/LIRGs.

astro-ph.GA↗

arXiv2019

The MUSE Ultra Deep Field (MUDF). I. Discovery of a group of Ly$\alpha$ 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$\alpha$ 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$\alpha$ 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.

astro-ph.GA↗

arXiv2016

The E-ELT Multi-Object Spectrograph: latest news from MOSAIC

There are 8000 galaxies, including 1600 at z larger than 1.6, which could be simultaneously observed in an E-ELT field of view of 40 sq. arcmin. A considerable fraction of astrophysical discoveries require large statistical samples, which can only be obtained with multi-object spectrographs (MOS). MOSAIC will provide a vast discovery space, enabled by a multiplex of 200 and spectral resolving powers of R=5000 and 20000. MOSAIC will also offer the unique capability of more than 10 "high-definition" (multi-object adaptive optics, MOAO) integral-field units, optimised to investigate the physics of the sources of reionization. The combination of these modes will make MOSAIC the world-leading MOS facility, contributing to all fields of contemporary astronomy, from extra-solar planets, to the study of the halo of the Milky Way and its satellites, and from resolved stellar populations in nearby galaxies out to observations of the earliest "first-light" structures in the Universe. It will also study the distribution of the dark and ordinary matter at all scales and epochs of the Universe. Recent studies of critical technical issues such as sky-background subtraction and MOAO have demonstrated that such a MOS is feasible with state-of-the-art technology and techniques. Current studies of the MOSAIC team include further trade-offs on the wavelength coverage, a solution for compensating for the non-telecentric new design of the telescope, and tests of the saturation of skylines especially in the near-IR bands. In the 2020s the E-ELT will become the world's largest optical/IR telescope, and we argue that it has to be equipped as soon as possible with a MOS to provide the most efficient, and likely the best way to follow-up on James Webb Space Telescope (JWST) observations.

astro-ph.IM↗

arXiv2016

EELT-HIRES the high-resolution spectrograph for the E-ELT

The first generation of E-ELT instruments will include an optical-infrared High Resolution Spectrograph, conventionally indicated as EELT-HIRES, which will be capable of providing unique breakthroughs in the fields of exoplanets, star and planet formation, physics and evolution of stars and galaxies, cosmology and fundamental physics. A 2-year long phase A study for EELT-HIRES has just started and will be performed by a consortium composed of institutes and organisations from Brazil, Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden, Switzerland and United Kingdom. In this paper we describe the science goals and the preliminary technical concept for EELT-HIRES which will be developed during the phase A, as well as its planned development and consortium organisation during the study.

astro-ph.IM↗

arXiv2010

Spectroscopic confirmation of a galaxy at redshift z=8.6

Galaxies had their most significant impact on the Universe when they assembled their first generations of stars. Energetic photons emitted by young, massive stars in primeval galaxies ionized the intergalactic medium surrounding their host galaxies, cleared sight-lines along which the light of the young galaxies could escape, and fundamentally altered the physical state of the intergalactic gas in the Universe continuously until the present day. Observations of the Cosmic Microwave Background, and of galaxies and quasars at the highest redshifts, suggest that the Universe was reionised through a complex process that was completed about a billion years after the Big Bang, by redshift z~6. Detecting ionizing Ly-alpha photons from increasingly distant galaxies places important constraints on the timing, location and nature of the sources responsible for reionisation. Here we report the detection of Ly-a photons emitted less than 600 million years after the Big Bang. UDFy-38135539 is at a redshift z=8.5549+-0.0002, which is greater than those of the previously known most distant objects, at z=8.2 and z=6.97. We find that this single source is unlikely to provide enough photons to ionize the volume necessary for the emission line to escape, requiring a significant contribution from other, probably fainter galaxies nearby.

astro-ph.CO↗

arXiv2010

EAGLE multi-object AO concept study for the E-ELT

EAGLE is the multi-object, spatially-resolved, near-IR spectrograph instrument concept for the E-ELT, relying on a distributed Adaptive Optics, so-called Multi Object Adaptive Optics. This paper presents the results of a phase A study. Using 84x84 actuator deformable mirrors, the performed analysis demonstrates that 6 laser guide stars and up to 5 natural guide stars of magnitude R<17, picked-up in a 7.3' diameter patrol field of view, allow us to obtain an overall performance in terms of Ensquared Energy of 35% in a 75x75 mas^2 spaxel at H band, whatever the target direction in the centred 5' science field for median seeing conditions. The computed sky coverage at galactic latitudes |b|~60 is close to 90%.

astro-ph.IM↗

arXiv2009

The physics of galaxy evolution with EAGLE

One of the prominent science goal of the ELTs will be to study the physics and mass assembly of galaxies at very high redshifts. Here, we present the galaxy evolution science case for EAGLE, which is a NIR multi-integral field spectrograph for the E-ELT currently under phase A study. We summarize results of simulations conducted to derive high-level requirements. In particular, we show how we have derived the specifications for the ensquared energy that the AO system needs to provide to reach the scientific goals of the instrument. Finally, we present future strategies to conduct galaxy surveys with EAGLE.

astro-ph.IM↗

arXiv2006

Performance Modeling of a Wide Field Ground Layer Adaptive Optics System

Using five independent analytic and Monte Carlo simulation codes, we have studied the performance of wide field ground layer adaptive optics (GLAO), which can use a single, relatively low order deformable mirror to correct the wavefront errors from the lowest altitude turbulence. GLAO concentrates more light from a point source in a smaller area on the science detector, but unlike traditional adaptive optics, images do not become diffraction-limited. Rather the GLAO point spread function (PSF) has the same functional form as a seeing-limited PSF, and can be characterized by familiar performance metrics such as Full-Width Half-Max (FWHM). The FWHM of a GLAO PSF is reduced by 0.1" or more for optical and near-infrared wavelengths over different atmospheric conditions. For the Cerro Pachon atmospheric model this correction is even greater when the image quality is worst, which effectively eliminates "bad-seeing" nights; the best seeing-limited image quality, available only 20% of the time, can be achieved 60 to 80% of the time with GLAO. This concentration of energy in the PSF will reduce required exposure times and improve the efficiency of an observatory up to 30 to 40%. These performance gains are relatively insensitive to a number of trades including the exact field of view of a wide field GLAO system, the conjugate altitude and actuator density of the deformable mirror, and the number and configuration of the guide stars.

astro-ph↗

arXiv2005

Can a photometric redshift code reliably determine dust extinction?

Photometric redshifts can be routinely obtained to accuracies of better than 0.1 in Delta(z)/(1+z). However, the issue of dust extinction is one that has still not been well quantified. In this paper the success of two template-fitting photometric redshift codes (IMPZ and HYPERZ) at reliably returning Av in addition to redshift is explored. New data on the CNOC2 spectroscopic sample of 0.2<z<0.7 galaxies are presented. These data allow us to estimate Av values from the observed Balmer decrements. We also investigate whether the empirical value of gamma=0.44, the ratio between gas- and star- derived extinction, as determined by Calzetti (2001), is necessarily the best value for this sample. When comparing the two codes to the Balmer-derived Av, a correlation between the photometrically derived Av, Phot-Av, and the Balmer-Av is found. The correlation is improved when the empirical value of gamma=0.44 is allowed to vary. From least-squares-fitting the minimum in the reduced chi^2 distribution is found for gamma~0.25 +/- 0.2. For the sample of galaxies here, the factor of two difference in covering factor implied by the Calzetti ratio is found to be plausible. The CNOC2 galaxies with detected Balmer lines have some preference for an increased covering factor difference, which would perhaps imply they are undergoing more rapid, `bursty' star formation than the galaxies Calzetti used in her derivation.

astro-ph↗

arXiv2002

CP Violation and Dilaton Stabilization in Heterotic String Models

We study the possibility of spontaneous CP violation in string models with the dilaton field stabilized at a phenomenologically acceptable value. We consider three mechanisms to stabilize the dilaton: multiple gaugino condensates, a nonperturbative Kahler potential, and a superpotential based on S-duality, and analyze consequent CP phases in the soft SUSY breaking terms. Due to non-universality forced upon the theory by requiring a non-trivial CKM phase, the EDM problem becomes more severe. Even if there are no complex phases in the VEVs of the SUSY breaking fields, the electric dipole moments are overproduced by orders of magnitude. We also address the question of modular invariance of the physical CP phases.

hep-th↗

arXiv2001

MIFS: A Mega Integral Field Spectrograph for the VLT

We describe MIFS, a second generation integral-field spectrograph for the VLT, operating in the visible wavelength range. It combines a 1'x1' field of view with the improved spatial resolution provided by multi-conjugate adaptive optics and covers a large simultaneous spectral range (0.6-1.0 microns). A separate mode exploits the highest spatial resolution provided by adaptive optics. With this unique combination of capabilities, MIFS has a wide domain of application and a large discovery potential. The MIFS low-spatial resolution mode (sampled at 0.2") combined with the initial MCAO capabilities planned for the VLT will provide ultra-deep fields with a limiting magnitude for spectroscopy of R~28. MIFS will improve the present day detection limit of Lyman alpha emitters by a factor of 100, and will detect low-mass star-forming galaxies to z~7. The MIFS high-spatial resolution mode (3"x3" field sampled at 0.01") is optimized for the next step in (MC)AO. It will probe, e.g., the relationship between supermassive central black holes and their host galaxy and the physics of winds from accretion disks in young stellar objects at unprecedented spatial resolution. MIFS will extend Europe's lead in integral-field spectroscopy. It capitalizes on new developments in adaptive optics, and is a key step towards instrumentation for OWL.

astro-ph↗

arXiv1996

Galaxy Evolution in Abell 2390

The galaxy population in the intermediate-redshift ($z=0.228$) rich cluster Abell 2390 is investigated. We present velocities, colors, and morphological information for an exceptionally large sample of 323 galaxies (216 cluster members) in a 46$^\prime \times 7^\prime$ (6 $h^{-1}$ Mpc $\times$ 1 $h^{-1}$ Mpc) strip centered on the cD galaxy. This sample of confirmed cluster members is second only to that for the Coma cluster in terms of sample size and spatial coverage in the cluster rest frame, and is the first to trace the transition between a rich cluster and the field at intermediate redshift. The galaxy population in the cluster changes gradually from a very evolved, early-type population in the inner 0.4 \hmpc\ of the cluster to a progressively later-type population in the extensive outer envelope of the cluster from 1 to 3 \hmpc\/ in radius. Radial gradients in galaxy $g-r$ color, 4000 Å\/ break, H$δ$ and [O II] line strengths and morphology are seen in the cluster, and are investigated by comparing the data to models computed with the GISSEL spectral synthesis package. The results suggest that the cluster has been gradually built up by the infall of field galaxies over $\sim 8$ Gyr and that star formation has been truncated in infalling galaxies during the accretion process. The morphological composition of the cluster is shown to be consistent with such a scenario. If true for other clusters, infall-truncated star formation as seen in Abell 2390 may explain both the Butcher-Oemler effect and the large fraction of S0 galaxies in clusters. Only $\simlt$5\% of the galaxies observed in Abell 2390 exhibit evidence for star formation at levels stronger than those seen in typical late-type systems. This suggests that starbursts do not play a major role in driving cluster galaxy evolution at the redshift of

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