Browsing by Author "Johnston, E. J."

Now showing 1 - 6 of 6
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    Directly constraining the spatial coherence of the z ∼ 1 circumgalactic medium
    (2023) Afruni, A.; Lopez, S.; Anshul, P.; Tejos, N.; Noterdaeme, P.; Berg, T. A. M.; Ledoux, C.; Solimano, M.; Gonzalez-Lopez, J.; Gronke, M.; Barrientos Parra, Luis Felipe; Johnston, E. J.
    One of the biggest puzzles regarding the circumgalactic medium (CGM) is the structure of its cool (T ∼ 104 K) gas phase. While the kinematics of quasar absorption systems suggests the CGM is composed of a population of different clouds, constraining their extent and spatial distribution has proven challenging, both from theoretical and observational points of view. In this work, we study the spatial structure of the z ∼ 1 CGM with unprecedented detail via resolved spectroscopy of giant gravitational arcs. We put together a sample of Mg IIλλ2796, 2803 detections obtained with VLT/MUSE in 91 spatially independent and contiguous sight lines toward 3 arcs, each probing an isolated star-forming galaxy believed to be detected in absorption. We constrain the coherence scale of this gas (Clength) - which represents the spatial scale over which the Mg II equivalent width (EW) remains constant - by comparing EW variations measured across all sight lines with empirical models. We find 1.4 < Clength/kpc < 7.8 (95% confidence). This measurement, of unprecedented accuracy, represents the scale over which the cool gas tends to cluster in separate structures. We argue that, if Clength is a universal property of the CGM, it needs to be reproduced by current and future theoretical models in order for us to understand the exact role of this medium in galaxy evolution....
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    MUSE observations of the giant low surface brightness galaxy Malin 1: Numerous HII regions, star formation rate, metallicity, and dust attenuation
    (2024) Junais; Weilbacher, P. M.; Epinat, B.; Boissier, S.; Galaz, G.; Johnston, E. J.; Puzia, T. H.; Amram, P.; Malek, K.
    Context. Giant low surface brightness (GLSB) galaxies are an extreme class of objects with very faint and extended gas-rich disks. Malin 1 is the largest GLSB galaxy known to date and one of the largest individual spiral galaxies observed so far, but the properties and formation mechanisms of its giant disk are still poorly understood.Aims. We used VLT/MUSE IFU spectroscopic observations of Malin 1 to measure the star formation rate (SFR), dust attenuation, and gas metallicity within this intriguing galaxy.Methods. We performed a penalized pixel fitting modeling to extract emission line fluxes such as H alpha, H beta, [N II](6583) and [O III](5007) along the central region as well as from the extended disk of Malin 1.Results. Our observations reveal for the first time strong H alpha emission distributed across numerous regions throughout the extended disk of Malin 1. The emission extends to radial distances of similar to 100 kpc, which indicates recent star formation activity. We made an estimate of the dust attenuation in the disk of Malin 1 using the Balmer decrement and found that Malin 1 has a mean H alpha attenuation of 0.36 mag. We observe a steep decline in the radial distribution of the SFR surface density (Sigma(SFR)) within the inner 20 kpc, followed by a shallow decline in the extended disk. We estimated the gas phase metallicity in Malin 1. We also found for the first time that the metallicity shows a steep gradient from solar metallicity to subsolar values in the inner 20 kpc of the galaxy, followed by a flattening of the metallicity in the extended disk with a relatively high value of similar to 0.6 Z(circle dot). We found that the normalized abundance gradient of the inner disk of Malin 1 is similar to the values found in normal galaxies. However, the normalized gradient observed in the outer disk can be considered extreme when compared to other disk galaxies. A comparison of the SFR surface density and gas surface density shows that unlike normal disk galaxies or other low surface brightness galaxies, the outer disk of Malin 1 exhibits a relatively low star formation efficiency based on atomic gas-mass estimates, which may be mildly exacerbated by the vanishing upper molecular gas-mass limits found by recent CO studies.Conclusions. With the detection of emission lines in a large part of the extended disk of Malin 1, this work sheds light on the star formation processes in this unique galaxy, highlighting its extended star-forming disk, dust attenuation, almost flat metallicity distribution in the outer disk, and exceptionally low star formation efficiency. Together with previous results, our findings contribute to a more detailed understanding of the formation of the giant disk of Malin 1, and they also constrain possible proposed scenarios of the nature of GLSB galaxies in general.
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    Orientation effects on cool gas absorption from gravitational-arc tomography of a z=0.77 disc galaxy
    (2022) Fernandez-Figueroa, A.; Lopez, S.; Tejos, N.; Berg, T. A. M.; Ledoux, C.; Noterdaeme, P.; Afruni, A.; Barrientos, L. F.; Gonzalez-Lopez, J.; Hamel, M.; Johnston, E. J.; Katsianis, A.; Sharon, K.; Solimano, M.
    We use spatially resolved spectroscopy of a distant giant gravitational arc to test orientation effects on Mg ii absorption equivalent width (EW) and covering fraction () in the circumgalactic medium of a foreground star-forming galaxy (G1) at z similar to 0.77. Forty-two spatially-binned arc positions uniformly sample impact parameters (D) to G1 between 10 and 30 kpc and azimuthal angles alpha between 30 degrees and 90 degrees (minor axis). We find an EW-D anticorrelation, akin to that observed statistically in quasar absorber studies, and an apparent correlation of both EW and with alpha, revealing a non-isotropic gas distribution. In line with our previous results on Mg ii kinematics suggesting the presence of outflows in G1, at minimum a simple 3D static double-cone model (to represent the trace of bipolar outflows) is required to recreate the EW spatial distribution. The D and alpha values probed by the arc cannot confirm the presence of a disc, but the data highly disfavour a disc alone. Our results support the interpretation that the EW-alpha correlation observed statistically using other extant probes is partly shaped by bipolar metal-rich winds.
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    Telltale signs of metal recycling in the circumgalactic medium of a z 0.77 galaxy
    (2021) Tejos, N.; López, S.; Ledoux, C.; Fernández-Figueroa, A.; Rivas, N.; Sharon, K.; Johnston, E. J.; Florian, M. K.; D'Ago, G.; Katsianis, A.; Barrientos, F.; Berg, T.; Corro-Guerra, F.; Hamel, M.; Moya-Sierralta, C.; Poudel, S.; Rigby, J. R.; Solimano, M.
    We present gravitational-arc tomography of the cool-warm enriched circumgalactic medium (CGM) of an isolated galaxy ('G1') at z approximate to 0.77. Combining VLT/MUSE adaptive-optics and Magellan/MagE echelle spectroscopy, we obtain partially resolved kinematics of Mg II in absorption and [O II] in emission. The unique arc configuration allows us to probe 42 spatially independent arc positions transverse to G1, plus four positions in front of it. The transverse positions cover G1's minor and major axes at impact parameters of approximate to 10-30 and approximate to 60kpc, respectively. We observe a direct kinematic connection between the cool-warm enriched CGM (traced by Mg II) and the interstellar medium (traced by [O II]). This provides strong evidence for the existence of an extended disc that co-rotates with the galaxy out to tens of kiloparsecs. The Mg II velocity dispersion (sigma approximate to 30-100 km s(-1), depending on position) is of the same order as the modelled galaxy rotational velocity (v(rot) approximate to 80 km s(-1)), providing evidence for the presence of a turbulent and pressure-supported CGM component. We regard the absorption to be modulated by a galactic-scale outflow, as it offers a natural scenario for the observed line-of-sight dispersion and asymmetric profiles observed against both the arcs and the galaxy. An extended enriched co-rotating disc together with the signatures of a galactic outflow, are telltale signs of metal recycling in the z similar to 1 CGM.
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    The ALMA-CRISTAL survey Discovery of a 15 kpc-long gas plume in a z=4.54 Lyman-α blob
    (2024) Solimano, M.; Gonzalez-Lopez, J.; Aravena, M.; Herrera-Camus, R.; De Looze, I.; Schreiber, N. M. Foerster; Spilker, J.; Tadaki, K.; Assef, R. J.; Barcos-Munoz, L.; Davies, R. L.; Diaz-Santos, T.; Ferrara, A.; Fisher, D. B.; Guaita, L.; Ikeda, R.; Johnston, E. J.; Lutz, D.; Mitsuhashi, I.; Moya-Sierralta, C.; Relano, M.; Naab, T.; Posses, A. C.; Telikova, K.; Uebler, H.; van der Giessen, S.; Veilleux, S.; Villanueva, V.
    Massive star-forming galaxies in the high-redshift universe host large reservoirs of cold gas in their circumgalactic medium (CGM). Traditionally, these reservoirs have been linked to diffuse H I Lyman-alpha (Ly alpha) emission extending beyond approximate to 10 kpc scales. In recent years, millimeter and submillimeter observations have started to identify even colder gas in the CGM through molecular and/or atomic tracers such as the [C II] 158 mu m transition. In this context, we studied the well-known J1000+0234 system at z = 4.54 that hosts a massive dusty star-forming galaxy (DSFG), a UV-bright companion, and a Ly alpha blob. We combined new ALMA [C II] line observations taken by the CRISTAL survey with data from previous programs targeting the J1000+0234 system, and achieved a deep view into a DSFG and its rich environment at a 0 ''. 2 = 1.3 kpc resolution. We identified an elongated [C II]-emitting structure with a projected size of 15 kpc stemming from the bright DSFG at the center of the field, with no clear counterpart at any other wavelength. The plume is oriented approximate to 40 degrees away from the minor axis of the DSFG, and shows significant spatial variation of its spectral parameters. In particular, the [C II] emission shifts from 180 km s(-1 )to 400 km s(-1) between the bottom and top of the plume, relative to the DSFG's systemic velocity. At the same time, the line width starts at 400 - 600 km s(-1) but narrows down to 190 km s(-1) at the top end of the plume. We discuss four possible scenarios to interpret the [C II] plume: a conical outflow, a cold accretion stream, ram pressure stripping, and gravitational interactions. While we cannot strongly rule out any of these with the available data, we disfavor the ram pressure stripping scenario due to the requirement of special hydrodynamic conditions.
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    The MAGPI survey: Science goals, design, observing strategy, early results and theoretical framework
    (2021) Foster, C.; Mendel, J. T.; Lagos, C. D. P.; Wisnioski, E.; Yuan, T.; D'Eugenio, F.; Barone, T. M.; Harborne, K. E.; Vaughan, S. P.; Schulze, F.; Remus, R-S.; Gupta, A.; Collacchioni, F.; Khim, D. J.; Taylor, P.; Bassett, R.; Croom, S. M.; McDermid, R. M.; Poci, A.; Battisti, A. J.; Bland-Hawthorn, J.; Bellstedt, S.; Colless, M.; Davies, L. J. M.; Derkenne, C.; Driver, S.; Ferre-Mateu, A.; Fisher, D. B.; Gjergo, E.; Johnston, E. J.; Khalid, A.; Kobayashi, C.; Oh, S.; Peng, Y.; Robotham, A. S. G.; Sharda, P.; Sweet, S. M.; Taylor, E. N.; Tran, K. -V. H.; Trayford, J. W.; van de Sande, J.; Yi, S. K.; Zanisi, L.
    We present an overview of the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey, a Large Program on the European Southern Observatory Very Large Telescope. MAGPI is designed to study the physical drivers of galaxy transformation at a look-back time of 3-4 Gyr, during which the dynamical, morphological, and chemical properties of galaxies are predicted to evolve significantly. The survey uses new medium-deep adaptive optics aided Multi-Unit Spectroscopic Explorer (MUSE) observations of fields selected from the Galaxy and Mass Assembly (GAMA) survey, providing a wealth of publicly available ancillary multi-wavelength data. With these data, MAGPI will map the kinematic and chemical properties of stars and ionised gas for a sample of 60 massive (>7 x 10(10) M-circle dot) central galaxies at 0.25 < z < 0.35 in a representative range of environments (isolated, groups and clusters). The spatial resolution delivered by MUSE with Ground Layer Adaptive Optics (0.6 - 0.8 arcsec FWHM) will facilitate a direct comparison with Integral Field Spectroscopy surveys of the nearby Universe, such as SAMI and MaNGA, and at higher redshifts using adaptive optics, for example, SINS. In addition to the primary (central) galaxy sample, MAGPI will deliver resolved and unresolved spectra for as many as 150 satellite galaxies at 0.25 < z < 0.35, as well as hundreds of emission-line sources at z < 6. This paper outlines the science goals, survey design, and observing strategy of MAGPI. We also present a first look at the MAGPI data, and the theoretical framework to which MAGPI data will be compared using the current generation of cosmological hydrodynamical simulations including EAGLE, MAGNETICUM, HORIZON-AGN, and ILLUSTRIS-TNG. Our results show that cosmological hydrodynamical simulations make discrepant predictions in the spatially resolved properties of galaxies at z approximate to 0.3. MAGPI observations will place new constraints and allow for tangible improvements in galaxy formation theory.