arXiv subjects

S. D. Johnson

Publications and source records attributed to S. D. Johnson.

10 recordsLinked to original sources

arXiv2024

MAGIC: Muse gAlaxy Groups In Cosmos -- A survey to probe the impact of environment on galaxy evolution over the last 8 Gyr

We introduce the MUSE gAlaxy Groups in COSMOS (MAGIC) survey, which was built to study the impact of environment on galaxy evolution over the last 8 Gyr. It consists of 17 MUSE fields targeting 14 massive structures at intermediate redshift ($0.3 21.5$. The spectroscopic redshift completeness is high: in the redshift range of [OII] emitters ($0.25 \le z < 1.5$), where most of the groups are found, it globally reaches a maximum of 80% down to $z_{app}^{++}=25.9$, and locally decreases from $\sim 100$% to $\sim50$% in magnitude bins from $z_{app}^{++}=23-24$ to $z_{app}^{++}=25.5$. We find that the fraction of quiescent galaxies increases with local density and with the time spent in groups. A morphological dichotomy is also found between bulge-dominated quiescent and disk-dominated star-forming galaxies. As environment gets denser, the peak of the stellar mass distribution shifts towards $M_*>10^{10}~M_\odot$, and the fraction of galaxies with $M_*<10^9~M_\odot$ decreases significantly, even for star-forming galaxies. We also highlight peculiar features such as close groups, extended nebulae, and a gravitational arc. Our results suggest that galaxies are preprocessed in groups of increasing mass before entering rich groups and clusters. We publicly release two catalogs containing the properties of galaxies and groups, respectively.

astro-ph.GA↗

arXiv2024

MALS discovery of a rare HI 21-cm absorber at $z\sim1.35$: origin of the absorbing gas in powerful AGN

We report a new, rare detection of HI 21-cm absorption associated with a quasar (only six known at $1 5$ GHz). The simplest explanation would be that no large HI column (N(HI)$>10^{17}$ cm$^{-2}$) is present towards the radio `core' and the optical AGN. Based on the joint optical and radio analysis of a heterogeneous sample of 16 quasars ($z_{median}$ = 0.7) and 15 radio galaxies ($z_{median}$ = 0.3) with HI 21-cm absorption detection and matched in 1.4 GHz luminosity (L$_{\rm 1.4\,GHz}$), a consistent picture emerges where quasars are primarily tracing the gas in the inner circumnuclear disk and cocoon created by the jet-ISM interaction. These exhibit L$_{1.4\,\rm GHz}$ - $ΔV_{\rm null}$ correlation, and frequent mismatch between the radio and optical spectral lines. The radio galaxies show no such correlation and likely trace the gas from the cocoon and the galaxy-wide ISM outside the photoionization cone. The analysis presented here demonstrates the potential of radio spectroscopic observations to reveal the origin of the absorbing gas associated with AGN that may be missed in optical observations.

astro-ph.GA↗

arXiv2023

First results from the JWST Early Release Science Program Q3D: Benchmark Comparison of Optical and Mid-IR Tracers of a Dusty, Ionized Red Quasar Wind at z=0.435

The [OIII] 5007 A emission line is the most common tracer of warm, ionized outflows in active galactic nuclei across cosmic time. JWST newly allows us to use mid-infrared spectral features at both high spatial and spectral resolution to probe these same winds. Here we present a comparison of ground-based, seeing-limited [OIII] and space-based, diffraction-limited [SIV] 10.51 micron maps of the powerful, kiloparsec-scale outflow in the Type 1 red quasar SDSS J110648.32+480712.3. The JWST data are from the Mid-InfraRed Instrument (MIRI). There is a close match in resolution between the datasets (0."6), in ionization potential of the O$^{+2}$ and S$^{+3}$ ions (35 eV), and in line sensitivity (1e-17 to 2e-17 erg/s/cm$^2$/arcsec$^2$). The [OIII] and [SIV] line shapes match in velocity and linewidth over much of the 20 kpc outflowing nebula, and [SIV] is the brightest line in the rest-frame 3.5-19.5 micron range, demonstrating its usefulness as a mid-IR probe of quasar outflows. [OIII] is nevertheless intriniscally brighter and provides better contrast with the point-source continuum, which is strong in the mid-IR. There is a strong anticorrelation of [OIII]/[SIV] with average velocity, which is consistent with a scenario of differential obscuration between the approaching (blueshifted) and receding (redshifted) sides of the flow. The dust in the wind may also obscure the central quasar, consistent with models that attribute red quasar extinction to dusty winds.

astro-ph.GA↗

arXiv2021

Improving blazar redshift constraints with the edge of the Ly$α$ forest: 1ES 1553+113 and implications for observations of the WHIM

Blazars are some of the brightest UV and X-ray sources in the sky and are valuable probes of the elusive warm-hot intergalactic medium (WHIM; $T{\simeq} 10^5-10^7$ K). However, many of the brightest blazars$-$called BL Lac objects such as 1ES1553+113$-$have quasi-featureless spectra and poorly constrained redshifts. Here, we significantly improve the precision of indirect redshift constraints for blazars based on the edge of the $\rm{H\,I}$ Ly$α$ forest observed in their UV spectra. We develop a robust technique to constrain the redshift of a $z<0.5$ AGN or blazar with a $1σ$ uncertainty of ${\approx}0.01$ using only the position of its highest-redshift Ly$α$ absorber with $\log N_{\rm{H\,I}}/{\rm cm^{-2}} > 12.6$. We use a large sample of 192 AGN/QSOs at $0.01\lesssim z\lesssim0.45$ that have high-quality COS FUV spectra to characterize the intrinsic scatter in the gap between the AGN redshift and the edge of their Ly$α$ forest. We present new COS NUV data for 1ES1553+113 and confirm its redshift of $z=0.433$ using our technique. We apply our Ly$α$-forest-based redshift estimation technique to nine additional blazars with archival ${\it HST}$ UV spectra, most of which are key targets for future X-ray missions. Our inferred redshift constraints improve estimates for two BL Lacs (1ES1118+424 and S50716+714) and are consistent with previous estimates for the rest. Our results emphasize the need to obtain further UV spectra of bright blazars, of which many have uncertain redshifts, in order to maximize the scientific value of future X-ray WHIM observations that will improve our understanding of galaxy evolution.

astro-ph.GA↗

arXiv2020

Probing the AGN Unification Model at redshift z $\sim$ 3 with MUSE observations of giant Ly$α$ nebulae

A prediction of the classic active galactic nuclei (AGN) unification model is the presence of ionisation cones with different orientations depending on the AGN type. Confirmations of this model exist for present times, but it is less clear in the early Universe. Here, we use the morphology of giant Ly$α$ nebulae around AGNs at redshift z$\sim$3 to probe AGN emission and therefore the validity of the AGN unification model at this redshift. We compare the spatial morphology of 19 nebulae previously found around type I AGNs with a new sample of 4 Ly$α$ nebulae detected around type II AGNs. Using two independent techniques, we find that nebulae around type II AGNs are more asymmetric than around type I, at least at radial distances $r>30$~physical kpc (pkpc) from the ionizing source. We conclude that the type I and type II AGNs in our sample show evidence of different surrounding ionising geometries. This suggests that the classical AGN unification model is also valid for high-redshift sources. Finally, we discuss how the lack of asymmetry in the inner parts (r$\lesssim$30 pkpc) and the associated high values of the HeII to Ly$α$ ratios in these regions could indicate additional sources of (hard) ionizing radiation originating within or in proximity of the AGN host galaxies. This work demonstrates that the morphologies of giant Ly$α$ nebulae can be used to understand and study the geometry of high redshift AGNs on circum-nuclear scales and it lays the foundation for future studies using much larger statistical samples.

astro-ph.GA↗

arXiv2019

The X-ray Halo Scaling Relations of Supermassive Black Holes

We carry out a comprehensive Bayesian correlation analysis between hot halos and direct masses of supermassive black holes (SMBHs), by retrieving the X-ray plasma properties (temperature, luminosity, density, pressure, masses) over galactic to cluster scales for 85 diverse systems. We find new key scalings, with the tightest relation being the $M_\bullet-T_{\rm x}$, followed by $M_\bullet-L_{\rm x}$. The tighter scatter (down to 0.2 dex) and stronger correlation coefficient of all the X-ray halo scalings compared with the optical counterparts (as the $M_\bullet-σ_{\rm e}$) suggest that plasma halos play a more central role than stars in tracing and growing SMBHs (especially those that are ultramassive). Moreover, $M_\bullet$ correlates better with the gas mass than dark matter mass. We show the important role of the environment, morphology, and relic galaxies/coronae, as well as the main departures from virialization/self-similarity via the optical/X-ray fundamental planes. We test the three major channels for SMBH growth: hot/Bondi-like models have inconsistent anti-correlation with X-ray halos and too low feeding; cosmological simulations find SMBH mergers as sub-dominant over most of the cosmic time and too rare to induce a central-limit-theorem effect; the scalings are consistent with chaotic cold accretion (CCA), the rain of matter condensing out of the turbulent X-ray halos that sustains a long-term self-regulated feedback loop. The new correlations are major observational constraints for models of SMBH feeding/feedback in galaxies, groups, and clusters (e.g., to test cosmological hydrodynamical simulations), and enable the study of SMBHs not only through X-rays, but also via the Sunyaev-Zel'dovich effect (Compton parameter), lensing (total masses), and cosmology (gas fractions).

astro-ph.GA↗

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.

astro-ph.GA↗

arXiv2012

Detection of high-field superconducting phase in CeCoIn$_5$ with magnetic susceptibility

We measure the ac susceptibility of single-crystal CeCoIn5 in dc field parallel to the c axis and find further evidence for a high-field phase transition within the superconducting phase in this orientation. We apply up to 2.3 kbar uniaxial pressure along the c axis and discuss the pressure dependence of the high-field phase. We also report the behavior of Hc2 under uniaxial pressure for field along c.

cond-mat.supr-con↗

arXiv2011

Superconductivity in Single-Crystal YIn3

We measure the superconducting transition of YIn$_3$ by resistivity, susceptibility, and specific heat. Despite using high-quality single-crystal samples, the transitions detected by the three techniques are shifted from each other in temperature, suggesting a region of filamentary superconductivity. We discuss the possible implications for filamentary superconductivity in unconventional superconductors.

cond-mat.supr-con↗

arXiv2011

Non-linear effect of uniaxial pressure on superconductivity in CeCoIn5

We study single-crystal CeCoIn5 with uniaxial pressure up to 3.97 kbar applied along the c-axis. We find a non-linear dependence of the superconducting transition temperature Tc on pressure, with a maximum close to 2 kbar. The transition also broadens significantly as pressure increases. We discuss the temperature dependence in terms of the general trend that Tc decreases in anisotropic heavy-fermion compounds as they move towards three-dimensional behavior.

cond-mat.supr-con↗