arXiv subjects

T. Jones

Publications and source records attributed to T. Jones.

At least 37 records · Page 2Linked to original sources

arXiv2018

Quantifying the suppression of the (un)-obscured star formation in galaxy cluster cores at 0.2$\lesssim$$z$$\lesssim$0.9

We quantify the star formation (SF) in the inner cores ($\mathcal{R}$/$R_{200}$$\leq$0.3) of 24 massive galaxy clusters at 0.2$\lesssim$$z$$\lesssim$0.9 observed by the $Herschel$ Lensing Survey and the Cluster Lensing and Supernova survey with $Hubble$. These programmes, covering the rest-frame ultraviolet to far-infrared regimes, allow us to accurately characterize stellar mass-limited ($\mathcal{M}_{*}$$>$$10^{10}$ $M_{\odot}$) samples of star-forming cluster members (not)-detected in the mid- and/or far-infrared. We release the catalogues with the photometry, photometric redshifts, and physical properties of these samples. We also quantify the SF displayed by comparable field samples from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. We find that in intermediate-$z$ cluster cores, the SF activity is suppressed with respect the field in terms of both the fraction ($\mathcal{F}$) of star-forming galaxies (SFG) and the rate at which they form stars ($\mathcal{SFR}$ and $s\mathcal{SFR} = \mathcal{SFR}/\mathcal{M}_{*}$). On average, the $\mathcal{F}$ of SFGs is a factor $\sim$$2$ smaller in cluster cores than in the field. Furthermore, SFGs present average $\mathcal{SFR}$ and $s\mathcal{SFR}$ typically $\sim$0.3 dex smaller in the clusters than in the field along the whole redshift range probed. Our results favour long time-scale quenching physical processes as the main driver of SF suppression in the inner cores of clusters since $z$$\sim$0.9, with shorter time-scale processes being very likely responsible for a fraction of the missing SFG population.

astro-ph.GA↗

arXiv2018

Towards Exascale Simulations of the ICM Dynamo with WENO-Wombat

In galaxy clusters, modern radio interferometers observe non-thermal radio sources with unprecedented spatial and spectral resolution. For the first time, the new data allows to infer the structure of the intra-cluster magnetic fields on small scales via Faraday tomography. This leap forward demands new numerical models for the amplification of magnetic fields in cosmic structure formation - the cosmological magnetic dynamo. Here we present a novel numerical approach to astrophyiscal MHD simulations aimed to resolve this small-scale dynamo in future cosmological simulations. As a first step, we implement a fifth order WENO scheme in the new code WOMBAT. We show that this scheme doubles the effective resolution of the simulation and is thus less expensive than common second order schemes. WOMBAT uses a novel approach to parallelization and load balancing developed in collaboration with performance engineers at Cray Inc. This will allow us scale simulation to the exaflop regime and achieve kpc resolution in future cosmological simulations of galaxy clusters. Here we demonstrate the excellent scaling properties of the code and argue that resolved simulations of the cosmological small scale dynamo within the whole virial radius are possible in the next years.

physics.comp-ph↗

arXiv2018

Metal Deficiency in Two Massive Dead Galaxies at $z\sim2$

Local massive early-type galaxies are believed to have completed most of their star formation $\sim10$Gyr ago and evolved without having substantial star formation since. If so, their progenitors should have roughly solar stellar metallicities ($Z_*$), comparable to their values today. We report the discovery of two lensed massive ($\log M_*/M_\odot\sim11$), $z\sim2.2$ dead galaxies, that appear markedly metal deficient given this scenario. Using 17-band $HST$+$K_{s}$+$Spitzer$ photometry and deep $HST$ grism spectra from the GLASS and SN Refsdal follow-up campaigns covering features near $λ_{\rm rest}\sim4000$Å, we find these systems to be dominated by A-type stars with $\log Z_*/Z_\odot=-0.40\pm0.02$ and $-0.49\pm0.03$ ($30$-$40\%$ solar) under standard assumptions. The second system's lower metallicity is robust to isochrone changes, though this choice can drive the first system's from $\log Z_*/Z_\odot=-0.6$ to 0.1. If these two galaxies are representative of larger samples, this finding suggests that evolutionary paths other than dry minor-merging are required for these massive galaxies. Future analyses with direct metallicity measurements-e.g., by the $James\ Webb\ Space\ Telescope$-will provide critical insight into the nature of such phenomena.

astro-ph.GA↗

arXiv2015

ALMA detection of [CII] 158 micron emission from a strongly lensed z=2 star-forming galaxy

Our objectives are to determine the properties of the interstellar medium (ISM) and of star-formation in typical star-forming galaxies at high redshift. Following up on our previous multi-wavelength observations with HST, Spitzer, Herschel, and the Plateau de Bure Interferometer (PdBI), we have studied a strongly lensed z=2.013 galaxy, the arc behind the galaxy cluster MACS J0451+0006, with ALMA to measure the [CII] 158 micron emission line, one of the main coolants of the ISM. [CII] emission from the southern part of this galaxy is detected at 10 $σ$. Taking into account strong gravitational lensing, which provides a magnification of $μ=49$, the intrinsic lensing-corrected [CII]158 micron luminosity is $L(CII)=1.2 \times 10^8 L_\odot$. The observed ratio of [CII]-to-IR emission, $L(CII)/L(FIR) \approx (1.2-2.4) \times 10^{-3}$, is found to be similar to that in nearby galaxies. The same also holds for the observed ratio $L(CII)/L(CO)=2.3 \times 10^3$, which is comparable to that of star-forming galaxies and active galaxy nuclei (AGN) at low redshift. We utilize strong gravitational lensing to extend diagnostic studies of the cold ISM to an order of magnitude lower luminosity ($L(IR) \sim (1.1-1.3) \times 10^{11} L_\odot$) and SFR than previous work at high redshift. While larger samples are needed, our results provide evidence that the cold ISM of typical high redshift galaxies has physical characteristics similar to normal star forming galaxies in the local Universe.

astro-ph.GA↗

arXiv2014

[CII] and 12CO(1-0) Emission Maps in HLSJ091828.6+514223: A Strongly Lensed Interacting System at z=5.24

We present Submillimeter Array (SMA) [CII] 158um and Jansky Very Large Array (JVLA) $^{12}$CO(1-0) line emission maps for the bright, lensed, submillimeter source at $z=5.2430$ behind Abell 773: HLSJ091828.6+514223 (HLS0918). We combine these measurements with previously reported line profiles, including multiple $^{12}$CO rotational transitions, [CI], water and [NII], providing some of the best constraints on the properties of the interstellar medium (ISM) in a galaxy at $z>5$. HLS0918 has a total far-infrared (FIR) luminosity L_FIR(8-1000um) = (1.6$\pm$0.1)x10^14 L_sun/mu, where the total magnification mu_total = 8.9$\pm$1.9, via a new lens model from the [CII] and continuum maps. Despite a HyLIRG luminosity, the FIR continuum shape resembles that of a local LIRG. We simultaneously fit all of the observed spectral line profiles, finding four components which correspond cleanly to discrete spatial structures identified in the maps. The two most redshifted spectral components occupy the nucleus of a massive galaxy, with a source plane separation <1 kpc. The reddest dominates the continuum map (de-magnified L_FIR = (1.1$\pm$0.2)x10^13 L_sun), and excites strong water emission in both nuclear components via a powerful FIR radiation field from the intense star formation. A third star-forming component is most likely a region of a merging companion (dV ~ 500 km/s) exhibiting generally similar gas properties. The bluest component originates from a spatially distinct region, and photo-dissociation region (PDR) analysis suggests that it is lower density, cooler and forming stars less vigorously than the other components. Strikingly, it has very strong [NII] emission which may suggest an ionized, molecular outflow. This comprehensive view of gas properties and morphology in HLS0918 previews the science possible for a large sample of high-redshift galaxies once ALMA attains full sensitivity.

astro-ph.CO↗

arXiv2013

MICE: the Muon Ionization Cooling Experiment. Step I: First Measurement of Emittance with Particle Physics Detectors

The Muon Ionization Cooling Experiment (MICE) is a strategic R&D project intended to demonstrate the only practical solution to providing high brilliance beams necessary for a neutrino factory or muon collider. MICE is under development at the Rutherford Appleton Laboratory (RAL) in the United Kingdom. It comprises a dedicated beamline to generate a range of input muon emittances and momenta, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. The emittance of the incoming beam will be measured in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in Liquid Hydrogen (LH2) absorbers to RF cavity acceleration. A second spectrometer, identical to the first, and a second muon identification system will measure the outgoing emittance. In the 2010 run at RAL the muon beamline and most detectors were fully commissioned and a first measurement of the emittance of the muon beam with particle physics (time-of-flight) detectors was performed. The analysis of these data was recently completed and is discussed in this paper. Future steps for MICE, where beam emittance and emittance reduction (cooling) are to be measured with greater accuracy, are also presented.

physics.acc-ph↗

arXiv2012

Hubble Space Telescope H-alpha imaging of star-forming galaxies at z = 1-1.5: evolution in the size and luminosity of giant HII regions

We present HST/WFC3 narrowband imaging of the H-alpha emission in a sample of eight gravitationally-lensed galaxies at z = 1 - 1.5. The magnification caused by the foreground clusters enables us to obtain a median source plane spatial resolution of 360pc, as well as providing magnifications in flux ranging from ~10x to ~50x. This enables us to identify resolved star-forming HII regions at this epoch and therefore study their H-alpha luminosity distributions for comparisons with equivalent samples at z ~ 2 and in the local Universe. We find evolution in the both luminosity and surface brightness of HII regions with redshift. The distribution of clump properties can be quantified with an HII region luminosity function, which can be fit by a power law with an exponential break at some cut-off, and we find that the cut-off evolves with redshift. We therefore conclude that `clumpy' galaxies are seen at high redshift because of the evolution of the cut-off mass; the galaxies themselves follow similar scaling relations to those at z = 0, but their HII regions are larger and brighter and thus appear as clumps which dominate the morphology of the galaxy. A simple theoretical argument based on gas collapsing on scales of the Jeans mass in a marginally unstable disk shows that the clumpy morphologies of high-z galaxies are driven by the competing effects of higher gas fractions causing perturbations on larger scales, partially compensated by higher epicyclic frequencies which stabilise the disk.

astro-ph.CO↗

arXiv2011

The SINS survey of z~2 galaxy kinematics: properties of the giant star forming clumps

We have studied the properties of giant star forming clumps in five z~2 star-forming disks with deep SINFONI AO spectroscopy at the ESO VLT. The clumps reside in disk regions where the Toomre Q-parameter is below unity, consistent with their being bound and having formed from gravitational instability. Broad Hα/[NII] line wings demonstrate that the clumps are launching sites of powerful outflows. The inferred outflow rates are comparable to or exceed the star formation rates, in one case by a factor of eight. Typical clumps may lose a fraction of their original gas by feedback in a few hundred million years, allowing them to migrate into the center. The most active clumps may lose much of their mass and disrupt in the disk. The clumps leave a modest imprint on the gas kinematics. Velocity gradients across the clumps are 10-40 km/s/kpc, similar to the galactic rotation gradients. Given beam smearing and clump sizes, these gradients may be consistent with significant rotational support in typical clumps. Extreme clumps may not be rotationally supported; either they are not virialized, or they are predominantly pressure supported. The velocity dispersion is spatially rather constant and increases only weakly with star formation surface density. The large velocity dispersions may be driven by the release of gravitational energy, either at the outer disk/accreting streams interface, and/or by the clump migration within the disk. Spatial variations in the inferred gas phase oxygen abundance are broadly consistent with inside-out growing disks, and/or with inward migration of the clumps.

astro-ph.CO↗

arXiv2009

Testing the Possible Intrinsic Origin of the Excess of Very Strong MgII Absorbers Along GRB Lines-of-Sight

The startling discovery of Prochter et al. (2006) that the frequency of very strong (W_r(2796)>1 A) MgII absorbers along gamma-ray burst (GRB) lines of sight ([dN/dz]_{GRB} = 0.90) is more than three times the frequency along quasar lines of sight ([dN/dz]_{QSO} = 0.24), over similar redshift ranges, has yet to be understood. We reconsider the possibility that the excess of very strong MgII absorbers toward GRBs is intrinsic either to the GRBs themselves or to their immediate environment, and associated with bulk outflows with velocities as large as v_{max} ~ 0.3c. In order to examine this hypothesis, we accumulate a sample of 27 W_r(2796) > 1 A absorption systems found toward 81 quasars, and compare their properties to those of 9 W_r(2796)>1 A absorption systems found toward 6 GRBs; all systems have been observed at high spectral resolution (R = 45,000) using the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope. We make multiple comparisons of the absorber properties across the two populations, testing for differences in metallicity, ionization state, abundance patterns, dust abundance, kinematics, and phase structure. We find no significant differences between the two absorber populations using any of these metrics, implying that, if the excess absorbers toward GRB lines of sight are indeed intrinsic, they must be produced in a process which has strong similarities to the processes yielding strong MgII systems in association with intervening galaxies. Although this may seem a priori unlikely, given the high outflow velocities required for any intrinsic model, we note that the same conclusion was reached, recently, with respect to the narrow absorption line systems seen in some quasars.

astro-ph↗

arXiv2009

MAXIPOL: Data Analysis and Results

We present results from and the analysis of data from MAXIPOL, a balloon-borne experiment designed to measure the polarization in the Cosmic Microwave Background (CMB). MAXIPOL is the first CMB experiment to obtain results using a rotating half-wave plate as a rapid polarization modulator. We report results from observations of a sky area of 8 deg^2 with 10-arcmin resolution, providing information up to l~700. We use a maximum-likelihood method to estimate maps of the Q and U Stokes parameters from the demodulated time streams, and then both Bayesian and frequentist approaches to compute the EE, EB, and BB power spectra. Detailed formalisms of the analyses are given. A variety of tests show no evidence for systematic errors. The Bayesian analysis gives weak evidence for an EE signal. The EE power is 55^{+51}_{-45} μK^2 at the 68% confidence level for l=151-693. Its likelihood function is asymmetric and skewed positive such that with a uniform prior the probability of a positive EE power is 96%. The powers of EB and BB signals at the 68% confidence level are 18^{+27}_{-34} μK^2 and -31^{+31}_{-19} μK^2 respectively and thus consistent with zero. The upper limit of the BB-mode at the 95% confidence level is 9.5 μK. Results from the frequentist approach are in agreement within statistical errors. These results are consistent with the current concordance LCDM model.

astro-ph↗

arXiv2008

Section on Extragalactic Science Topics of the White Paper on the Status and Future of Ground-Based TeV Gamma-Ray Astronomy

This is a report on the findings of the extragalactic science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed section discusses extragalactic science topics including active galactic nuclei, cosmic ray acceleration in galaxies, galaxy clusters and large scale structure formation shocks, and the study of the extragalactic infrared and optical background radiation. The scientific potential of ground based gamma-ray observations of Gamma-Ray Bursts and dark matter annihilation radiation is covered in other sections of the white paper.

astro-ph↗

arXiv2008

Section on Supernova remnants and cosmic rays of the White Paper on the Status and Future of Ground-based Gamma-ray Astronomy

This is a report on the findings of the SNR/cosmic-ray working group for the white paper on the status and future of ground-based gamma-ray astronomy. The white paper is an APS commissioned document, and the overall version has also been released and can be found on astro-ph. This detailed section of the white paper discusses the status of past and current attempts to observe shell-type supernova remnants and diffuse emission from cosmic rays at GeV-TeV energies. We concentrate on the potential of future ground-based gamma-ray experiments to study the acceleration of relativistic charged particles which is one of the main unsolved, yet fundamental, problems in modern astrophysics. The acceleration of particles relies on interactions between energetic particles and magnetic turbulence. In the case of SNRs we can perform spatially resolved studies in systems with known geometry, and the plasma physics deduced from these observations will help us to understand other systems where rapid particle acceleration is believed to occur and where observations as detailed as those of SNRs are not possible.

astro-ph↗

arXiv2006

MAXIPOL: Cosmic Microwave Background Polarimetry Using a Rotating Half-Wave Plate

We discuss MAXIPOL, a bolometric balloon-borne experiment designed to measure the E-mode polarization of the cosmic microwave background radiation (CMB). MAXIPOL is the first bolometric CMB experiment to observe the sky using rapid polarization modulation. To build MAXIPOL, the CMB temperature anisotropy experiment MAXIMA was retrofitted with a rotating half-wave plate and a stationary analyzer. We describe the instrument, the observations, the calibration and the reduction of data collected with twelve polarimeters operating at 140 GHz and with a FWHM beam size of 10 arcmin. We present maps of the Q and U Stokes parameters of an 8 deg^2 region of the sky near the star Beta Ursae Minoris. The power spectra computed from these maps give weak evidence for an EE signal. The maximum-likelihood amplitude of l(l+1)C^{EE}_{l}/(2 pi) is 55_{-45}^{+51} uK^2 (68%), and the likelihood function is asymmetric and skewed positive such that with a uniform prior the probability that the amplitude is positive is 96%. This result is consistent with the expected concordance LCDM amplitude of 14 uK^2. The maximum likelihood amplitudes for l(l+1)C^{BB}_{l}/(2 pi) and $\ell(\ell+1)C^{EB}_{\ell}/2π$ are -31_{-19}^{+31} and 18_{-34}^{+27} uK^2 (68%), respectively, which are consistent with zero. All of the results are for one bin in the range 151 < l < 693. Tests revealed no residual systematic errors in the time or map domain. A comprehensive discussion of the analysis of the data is presented in a companion paper.

astro-ph↗

arXiv2006

Experimental determination of the complete spin structure for anti-proton + proton -> anti-Λ+ Λat anti-proton beam momentum of 1.637 GeV/c

The reaction anti-proton + proton -> anti-Λ+ Λ-> anti-proton + π^+ + proton + π^- has been measured with high statistics at anti-proton beam momentum of 1.637 GeV/c. The use of a transversely-polarized frozen-spin target combined with the self-analyzing property of Λ/anti-Λdecay allows access to unprecedented information on the spin structure of the interaction. The most general spin-scattering matrix can be written in terms of eleven real parameters for each bin of scattering angle, each of these parameters is determined with reasonable precision. From these results all conceivable spin-correlations are determined with inherent self-consistency. Good agreement is found with the few previously existing measurements of spin observables in anti-proton + proton -> anti-Λ+ Λnear this energy. Existing theoretical models do not give good predictions for those spin-observables that had not been previously measured.

nucl-ex↗

arXiv2006

Theory and Application of Dissociative Electron Capture in Molecular Identification

The coupling of an electron monochromator (EM) to a mass spectrometer (MS) has created a new analytical technique, EM-MS, for the investigation of electrophilic compounds. This method provides a powerful tool for molecular identification of compounds contained in complex matrices, such as environmental samples. EM-MS expands the application and selectivity of traditional MS through the inclusion of a new dimension in the space of molecular characteristics--the electron resonance energy spectrum. However, before this tool can realize its full potential, it will be necessary to create a library of resonance energy scans from standards of the molecules for which EM-MS offers a practical means of detection. Here, an approach supplementing direct measurement with chemical inference and quantum scattering theory is presented to demonstrate the feasibility of directly calculating resonance energy spectra. This approach makes use of the symmetry of the transition-matrix element of the captured electron to discriminate between the spectra of isomers. As a way of validating this approach, the resonance values for twenty-five nitrated aromatic compounds were measured along with their relative abundance. Subsequently, the spectra for the isomers of nitrotoluene were shown to be consistent with the symmetry-based model. The initial success of this treatment suggests that it might be possible to predict negative ion resonances and thus create a library of EM-MS standards.

physics.chem-ph↗

arXiv2005

Evidence for the Decay Sigma+ -> p mu+ mu-

We report the first evidence for the decay Sigma+ -> p mu+ mu- from data taken by the HyperCP experiment(E871) at Fermilab. Based on three observed events, the branching ratio is B(Sigma+ -> p,mu+,mu-) = [8.6 +6.6,-5.4(stat) +/-5.5(syst)] x 10**-8. The narrow range of dimuon masses may indicate that the decay proceeds via a neutral intermediate state, Sigma+ -> p P0, P0 -> mu+ mu-, with a P0 mass of 214.3 +/- 0.5 MeV/c**2 and branching ratio B(Sigma+ -> p P0; P0 -> mu+ mu-) = [3.1 +2.4,-1.(stat) +/-1.5(syst)] x 10**-8.

hep-ex↗

arXiv2005

The EBEX Experiment

EBEX is a balloon-borne polarimeter designed to measure the intensity and polarization of the cosmic microwave background radiation. The measurements would probe the inflationary epoch that took place shortly after the big bang and would significantly improve constraints on the values of several cosmological parameters. EBEX is unique in its broad frequency coverage and in its ability to provide critical information about the level of polarized Galactic foregrounds which will be necessary for all future CMB polarization experiments. EBEX consists of a 1.5 m Dragone-type telescope that provides a resolution of less than 8 arcminutes over four focal planes each of 4 degree diffraction limited field of view at frequencies up to 450 GHz. The experiment is designed to accommodate 330 transition edge bolometric detectors per focal plane, for a total of up to 1320 detectors. EBEX will operate with frequency bands centered at 150, 250, 350, and 450 GHz. Polarimetry is achieved with a rotating achromatic half-wave plate. EBEX is currently in the design and construction phase, and first light is scheduled for 2008.

astro-ph↗

arXiv2004

Search for CP Violation in Charged-Xi and Lambda Hyperon Decays

We have compared the proton and antiproton angular distributions in 117 million Xi-minus -> Lambda + pi-minus -> proton + pi-minus + pi-minus and 41 million anti-Xi-minus -> anti-Lamba + pi-plus -> antiproton + pi-plus + pi-plus decays using a subset of the data from the HyperCP experiment (E871) at Fermilab. We find no evidence of CP violation, with the direct-CP-violating parameter $A_{ΞΛ} = \frac{α_Ξα_Λ - \barα_Ξ\barα_Λ}{α_Ξα_Λ + \barα_Ξ\barα_Λ} = [0.0+/-5.1(stat)+/-4.4(syst)]{\times}10^{-4}$.

hep-ex↗