arXiv subjects

Grant Wilson

Publications and source records attributed to Grant Wilson.

16 recordsLinked to original sources

arXiv2024

Improved Constraints on Mergers with SZ, Hydrodynamical simulations, Optical, and X-ray (ICM-SHOX). Paper II: Galaxy cluster sample overview

Galaxy cluster mergers are representative of a wide range of physics, making them an excellent probe of the properties of dark matter and the ionized plasma of the intracluster medium. To date, most studies have focused on mergers occurring in the plane of the sky, where morphological features can be readily identified. To allow study of mergers with arbitrary orientation, we have assembled multi-probe data for the eight-cluster ICM-SHOX sample sensitive to both morphology and line of sight velocity. The first ICM-SHOX paper (Silich+2023) provided an overview of our methodology applied to one member of the sample, MACS J0018.5+1626, in order to constrain its merger geometry. That work resulted in an exciting new discovery of a velocity space decoupling of its gas and dark matter distributions. In this work, we describe the availability and quality of multi-probe data for the full ICM-SHOX galaxy cluster sample. These datasets will form the observational basis of an upcoming full ICM-SHOX galaxy cluster sample analysis.

astro-ph.CO↗

arXiv2023

ICM-SHOX. Paper I: Methodology overview and discovery of a gas--dark matter velocity decoupling in the MACS J0018.5+1626 merger

Galaxy cluster mergers are rich sources of information to test cluster astrophysics and cosmology. However, cluster mergers produce complex projected signals that are difficult to interpret physically from individual observational probes. Multi-probe constraints on the gas and dark matter cluster components are necessary to infer merger parameters that are otherwise degenerate. We present ICM-SHOX (Improved Constraints on Mergers with SZ, Hydrodynamical simulations, Optical, and X-ray), a systematic framework to jointly infer multiple merger parameters quantitatively via a pipeline that directly compares a novel combination of multi-probe observables to mock observables derived from hydrodynamical simulations. We report a first application of the ICM-SHOX pipeline to MACS J0018.5+1626, wherein we systematically examine simulated snapshots characterized by a wide range of initial parameters to constrain the MACS J0018.5+1626 merger geometry. We constrain the epoch of MACS J0018.5+1626 to the range $0$--$60$ Myr post-pericenter passage, and the viewing angle is inclined $\approx 27$--$40$ degrees from the merger axis. We obtain constraints for the impact parameter ($\lesssim 250$ kpc), mass ratio ($\approx 1.5$--$3.0$), and initial relative velocity when the clusters are separated by 3 Mpc ($\approx 1700$--3000 km s$^{-1}$). The primary and secondary clusters initially (at 3 Mpc) have gas distributions that are moderately and strongly disturbed, respectively. We discover a velocity space decoupling of the dark matter and gas distributions in MACS J0018.5+1626, traced by cluster-member galaxy velocities and the kinematic Sunyaev-Zel'dovich effect, respectively. Our simulations indicate this decoupling is dependent on the different collisional properties of the two distributions for particular merger epochs, geometries, and viewing angles.

astro-ph.CO↗

arXiv2023

ALMA reveals a stable rotating gas disk in a paradoxical low-mass, ultra-dusty galaxy at z = 4.274

We report ALMA detections of [CII] and dust continuum in Az9, a multiply-imaged galaxy behind the Frontier Field cluster MACSJ0717.5+3745. The bright [CII] emission line provides a spectroscopic redshift of z = 4.274. This strongly lensed (mu = 7 +/- 1) galaxy has an intrinsic stellar mass of only 2e9 Msun and a total star formation rate of 26 Msun/yr (~80% of which is dust obscured). Using public magnification maps, we reconstruct the [CII] emission in the source plane to reveal a stable, rotation-dominated disk with V/sigma = 5.3, which is > 2x higher than predicted from simulations for similarly high-redshift, low-mass galaxies. In the source plane, the [CII] disk has a half-light radius of 1.8 kpc and, along with the dust, is spatially offset from the peak of the stellar light by 1.4 kpc. Az9 is not deficient in [CII]; L[CII]/LIR = 0.0027 consistent with local and high redshift normal star forming galaxies. While dust-obscured star formation is expected to dominate in higher mass galaxies, such a large reservoir of dust and gas in a lower mass disk galaxy 1.4 Gyr after the Big Bang challenges our picture of early galaxy evolution. Furthermore, the prevalence of such low-mass dusty galaxies has important implications for the selection of the highest redshift dropout galaxies with JWST. As one of the lowest stellar mass galaxies at z > 4 to be detected in dust continuum and [CII], Az9 is an excellent laboratory in which to study early dust enrichment in the interstellar medium.

astro-ph.GA↗

arXiv2021

Early Science with the Large Millimeter Telescope: Constraining the Gas Fraction of a Compact Quiescent Galaxy at z=1.883

We present constraints on the dust continuum flux and inferred gas content of a gravitationally lensed massive quiescent galaxy at $z$=1.883$\pm$0.001 using AzTEC 1.1mm imaging with the Large Millimeter Telescope. MRG-S0851 appears to be a prototypical massive compact quiescent galaxy, but has evidence that it experienced a centrally concentrated rejuvenation event in the last 100 Myr (see Akhshik et al. 2020). This galaxy is undetected in the AzTEC image but we calculate an upper limit on the millimeter flux and use this to estimate the H$_2$ mass limit via an empirically calibrated relation that assumes a constant molecular gas-to-dust ratio of 150. We constrain the 3$σ$ upper limit of the H$_2$ fraction from the dust continuum in MRG-S0851 to be ${M_{H_2}/M_{\star}}$ $\leq$ 6.8%. MRG-S0851 has a low gas fraction limit with a moderately low sSFR owing to the recent rejuvenation episode, which together results in a relatively short depletion time of $<$0.6 Gyr if no further H$_2$ gas is accreted. Empirical and analytical models both predict that we should have detected molecular gas in MRG-S0851, especially given the rejuvenation episode; this suggests that cold gas and/or dust is rapidly depleted in at least some early quiescent galaxies.

astro-ph.GA↗

arXiv2020

A Comparison of Machine Learning Algorithms Applied to American Legislature Polarization

We present a novel approach to the measurement of American state legislature polarization with an experimental comparison of three different machine learning algorithms. Our approach strictly relies on public data sources and open source software. The results suggest that artificial neural network regression has the best outcome compared to both support vector machine and ordinary least squares regression in the prediction of both state House and state Senate legislature polarization. In addition to the technical outcomes of our study, broader implications are assessed as a means of highlighting the importance of accessible information for the higher purpose of promoting civic responsibility.

cs.CY↗

arXiv2019

Nature of Faint Radio Sources in GOODS-North and GOODS-South Fields - I. Spectral Index and Radio-FIR Correlation

We present the first results from the deep and wide 5 GHz radio observations of the Great Observatories Origins Deep Survey (GOODS)-North ($σ=3.5 \; μJy \; beam^{-1}$, synthesized beam size $θ=$ 1.47 arcsec $\times$ 1.42 arcsec, and 52 sources over 109 arcmin$^{2}$) and GOODS-South ($σ=3.0 \; μJy \; beam^{-1}$, $θ=$0.98 arcsec $\times$ 0.45 arcsec, and 88 sources over 190 arcmin$^{2}$) fields using the Karl G. Jansky Very Large Array. We derive radio spectral indices α between 1.4 and 5 GHz using the beam-matched images and show that the overall spectral index distribution is broad even when the measured noise and flux bias are considered. We also find a clustering of faint radio sources around $α=0.8$, but only within $S_{5GHz} < 150 \; μJy$. We demonstrate that the correct radio spectral index is important for deriving accurate rest frame radio power and analyzing the radio-FIR correlation, and adopting a single value of $α=0.8$ leads to a significant scatter and a strong bias in the analysis of the radio-FIR correlation, resulting from the broad and asymmetric spectral index distribution. When characterized by specific star formation rates, the starburst population (58%) dominates the 5 GHz radio source population, and the quiescent galaxy population (30%) follows a distinct trend in spectral index distribution and the radio-FIR correlation. Lastly, we offer suggestions on sensitivity and angular resolution for future ultra-deep surveys designed to trace the cosmic history of star formation and AGN activity using radio continuum as a probe.

astro-ph.GA↗

arXiv2019

A High-resolution SZ View of the Warm-Hot Universe

The Sunyaev-Zeldovich (SZ) effect was first predicted nearly five decades ago, but has only recently become a mature tool for performing high resolution studies of the warm and hot ionized gas in and between galaxies, groups, and clusters. Galaxy groups and clusters are powerful probes of cosmology, and they also serve as hosts for roughly half of the galaxies in the Universe. In this white paper, we outline the advances in our understanding of thermodynamic and kinematic properties of the warm-hot universe that can come in the next decade through spatially and spectrally resolved measurements of the SZ effects. Many of these advances will be enabled through new/upcoming millimeter/submillimeter (mm/submm) instrumentation on existing facilities, but truly transformative advances will require construction of new facilities with larger fields of view and broad spectral coverage of the mm/submm bands.

astro-ph.CO↗

arXiv2018

Optical Design of the TolTEC Millimeter-wave Camera

TolTEC is a new camera being built for the 50-meter Large Millimeter-wave Telescope (LMT) in Puebla, Mexico to survey distant galaxies and star-forming regions in the Milky Way. The optical design simultaneously couples the field of view onto focal planes at 150, 220, and 280 GHz. The optical design and detector properties, as well as a data-driven model of the atmospheric emission of the LMT site, inform the sensitivity model of the integrated instrument. This model is used to optimize the instrument design, and to calculate the mapping speed as an early forecast of the science reach of the instrument.

astro-ph.IM↗

arXiv2016

Clumpy and Extended Starbursts in the Brightest Unlensed Submillimeter Galaxies

The central structure in three of the brightest unlensed z=3-4 submillimeter galaxies are investigated through 0.015" - 0.05" (120 -- 360~pc) 860 micron continuum images obtained using the Atacama Large Millimeter/submillimeter Array (ALMA). The distribution in the central kpc in AzTEC1 and AzTEC8 are extremely complex, and they are composed of multiple ~200 pc clumps. AzTEC4 consists of two sources that are separated by ~1.5 kpc, indicating a mid-stage merger. The peak star formation rate densities in the central clumps are ~300 - 3000 Msun/yr/kpc^2, suggesting regions with extreme star formation near the Eddington Limit. By comparing the flux obtained by ALMA and Submillimeter Array (SMA), we find that 68-90% of the emission is extended (> 1 kpc) in AzTEC 4 and 8. For AzTEC1, we identify at least 11 additional compact (~200 pc) clumps in the extended 3 - 4 kpc region. Overall, the data presented here suggest that the luminosity surface densities observed at < 150 pc scales are roughly similar to that observed in local ULIRGs, as in the eastern nucleus of Arp 220. Between 10 to 30% of the 860 micron continuum is concentrated in clumpy structures in the central kpc while the remaining flux is distributed over > 1 kpc regions, some of which could also be clumpy. These sources can be explained by a rapid inflow of gas such as a merger of gas-rich galaxies, surrounded by extended and clumpy starbursts. However, the cold mode accretion model is not ruled out.

astro-ph.GA↗

arXiv2013

The Atacama Cosmology Telescope: Cosmological parameters from three seasons of data

We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power ell^2 C_ell/2pi of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 +\- 1.4 muK^2 at ell=3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 muK^2. Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be Neff=2.79 +\- 0.56, in agreement with the canonical value of Neff=3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Sigma m_nu < 0.39 eV at 95% confidence when combining ACT and WMAP 7-year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Yp = 0.225 +\- 0.034, and measure no variation in the fine structure constant alpha since recombination, with alpha/alpha0 = 1.004 +/- 0.005. We also find no evidence for any running of the scalar spectral index, dns/dlnk = -0.004 +\- 0.012.

astro-ph.CO↗

arXiv2013

A Critical Assessment of Photometric Redshift Methods: A CANDELS Investigation

We present results from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) photometric redshift methods investigation. In this investigation, the results from eleven participants, each using a different combination of photometric redshift code, template spectral energy distributions (SEDs) and priors, are used to examine the properties of photometric redshifts applied to deep fields with broad-band multi-wavelength coverage. The photometry used includes U-band through mid-infrared filters and was derived using the TFIT method. Comparing the results, we find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others. However, we find codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photometric redshifts by adding zero-point offsets, template adjusting or adding extra smoothing errors. These results therefore stress the importance of the training procedure. We find a strong dependence of the photometric redshift accuracy on the signal-to-noise ratio of the photometry. On the other hand, we find a weak dependence of the photometric redshift scatter with redshift and galaxy color. We find that most photometric redshift codes quote redshift errors (e.g., 68% confidence intervals) that are too small compared to that expected from the spectroscopic control sample. We find that all codes show a statistically significant bias in the photometric redshifts. However, the bias is in all cases smaller than the scatter, the latter therefore dominates the errors. Finally, we find that combining results from multiple codes significantly decreases the photometric redshift scatter and outlier fraction. We discuss different ways of combining data to produce accurate photometric redshifts and error estimates.

astro-ph.CO↗

arXiv2012

The Atacama Cosmology Telescope: Data Characterization and Map Making

We present a description of the data reduction and mapmaking pipeline used for the 2008 observing season of the Atacama Cosmology Telescope (ACT). The data presented here at 148 GHz represent 12% of the 90 TB collected by ACT from 2007 to 2010. In 2008 we observed for 136 days, producing a total of 1423 hours of data (11 TB for the 148 GHz band only), with a daily average of 10.5 hours of observation. From these, 1085 hours were devoted to a 850 deg^2 stripe (11.2 hours by 9.1 deg) centered on a declination of -52.7 deg, while 175 hours were devoted to a 280 deg^2 stripe (4.5 hours by 4.8 deg) centered at the celestial equator. We discuss sources of statistical and systematic noise, calibration, telescope pointing, and data selection. Out of 1260 survey hours and 1024 detectors per array, 816 hours and 593 effective detectors remain after data selection for this frequency band, yielding a 38% survey efficiency. The total sensitivity in 2008, determined from the noise level between 5 Hz and 20 Hz in the time-ordered data stream (TOD), is 32 micro-Kelvin sqrt{s} in CMB units. Atmospheric brightness fluctuations constitute the main contaminant in the data and dominate the detector noise covariance at low frequencies in the TOD. The maps were made by solving the least-squares problem using the Preconditioned Conjugate Gradient method, incorporating the details of the detector and noise correlations. Cross-correlation with WMAP sky maps, as well as analysis from simulations, reveal that our maps are unbiased at multipoles ell > 300. This paper accompanies the public release of the 148 GHz southern stripe maps from 2008. The techniques described here will be applied to future maps and data releases.

astro-ph.IM↗

arXiv2011

Molecular Outflows From the Protocluster, Serpens South

We present the results of CO ($J=3-2$) and HCO$^+$ ($J=4-3$) mapping observations toward a nearby embedded cluster, Serpens South, using the ASTE 10 m telescope. Our CO ($J=3-2$) map reveals that many outflows are crowded in the dense cluster-forming clump that can be recognized as a HCO$^+$ clump with a size of $\sim$ 0.2 pc and mass of $\sim$ 80 M$_\odot$. The clump contains several subfragments with sizes of $\sim$ 0.05 pc. By comparing the CO ($J=3-2$) map with the 1.1 mm dust continuum image taken by AzTEC on ASTE, we find that the spatial extents of the outflow lobes are sometimes anti-correlated with the distribution of the dense gas and some of the outflow lobes apparently collide with the dense gas. The total outflow mass, momentum, and energy are estimated at 0.6 $M_\odot$, 8 $M_\odot$ km s$^{-1}$, and 64 $M_\odot$ km$^2$ s$^{-2}$, respectively. The energy injection rate due to the outflows is comparable to the turbulence dissipation rate in the clump, implying that the protostellar outflows can maintain the supersonic turbulence in this region. The total outflow energy seems only about 10 percent the clump gravitational energy. We conclude that the current outflow activity is not enough to destroy the whole cluster-forming clump, and therefore star formation is likely to continue for several or many local dynamical times.

astro-ph.SR↗

arXiv2011

IRAS 15099-5856: Remarkable Mid-Infrared Source with Prominent Crystalline Silicate Emission Embedded in the Supernova Remnant MSH15-52

We report new mid-infrared observations of the remarkable object IRAS 15099-5856 using the space telescopes AKARI and Spitzer, which demonstrate the presence of prominent crystalline silicate emission in this bright source. IRAS 15099-5856 has a complex morphology with a bright central compact source (IRS1) surrounded by knots, spurs, and several extended (~4') arc-like filaments. The source is seen only at >= 10 um. The Spitzer MIR spectrum of IRS1 shows prominent emission features from Mg-rich crystalline silicates, strong [Ne II] 12.81 um and several other faint ionic lines. We model the MIR spectrum as thermal emission from dust and compare with the Herbig Be star HD 100546 and the luminous blue variable R71, which show very similar MIR spectra. Molecular line observations reveal two molecular clouds around the source, but no associated dense molecular cores. We suggest that IRS1 is heated by UV radiation from the adjacent O star Muzzio 10 and that its crystalline silicates most likely originated in a mass outflow from the progenitor of the supernova remnant (SNR) MSH 15-52. IRS1, which is embedded in the SNR, could have been shielded from the SN blast wave if the progenitor was in a close binary system with Muzzio 10. If MSH15-52 is a remnant of Type Ib/c supernova (SN Ib/c), as has been previously proposed, this would confirm the binary model for SN Ib/c. IRS1 and the associated structures may be the relics of massive star death, as shaped by the supernova explosion, the pulsar wind and the intense ionizing radiation of the embedded O star.

astro-ph.GA↗

arXiv2010

Detection of Strong Millimeter Emission from the Circumstellar Dust Disk Around V1094 Sco: Cold and Massive Disk around a T Tauri Star in a Quiescent Accretion Phase?

We present the discovery of a cold massive dust disk around the T Tauri star V1094 Sco in the Lupus molecular cloud from the 1.1 millimeter continuum observations with AzTEC on ASTE. A compact ($r\lesssim$320 AU) continuum emission coincides with the stellar position having a flux density of 272 mJy which is largest among T Tauri stars in Lupus. We also present the detection of molecular gas associated with the star in the five-point observations in $^{12}$CO J=3--2 and $^{13}$CO J=3--2. Since our $^{12}$CO and $^{13}$CO observations did not show any signature of a large-scale outflow or a massive envelope, the compact dust emission is likely to come from a disk around the star. The observed SED of V1094 Sco shows no distinct turnover from near infrared to millimeter wavelengths, which can be well described by a flattened disk for the dust component, and no clear dip feature around 10 $\micron$ suggestive of absence of an inner hole in the disk. We fit a simple power-law disk model to the observed SED. The estimated disk mass ranges from 0.03 to $\gtrsim$0.12 $M_\sun$, which is one or two orders of magnitude larger than the median disk mass of T Tauri stars in Taurus.

astro-ph.SR↗

arXiv2010

Origins of the extragalactic background at 1mm from a combined analysis of the AzTEC and MAMBO data in GOODS-N

We present a study of the cosmic infrared background, which is a measure of the dust obscured activity in all galaxies in the Universe. We venture to isolate the galaxies responsible for the background at 1mm; with spectroscopic and photometric redshifts we constrain the redshift distribution of these galaxies. We create a deep 1.16mm map (sigma ~ 0.5mJy) by combining the AzTEC 1.1mm and MAMBO 1.2mm datasets in GOODS-N. This combined map contains 41 secure detections, 13 of which are new. By averaging the 1.16mm flux densities of individually undetected galaxies with 24um flux densities > 25uJy, we resolve 31--45 per cent of the 1.16mm background. Repeating our analysis on the SCUBA 850um map, we resolve a higher percentage (40--64 per cent) of the 850um background. A majority of the background resolved (attributed to individual galaxies) at both wavelengths comes from galaxies at z > 1.3. If the ratio of the resolved submillimeter to millimeter background is applied to a reasonable scenario for the origins of the unresolved submillimeter background, 60--88 per cent of the total 1.16mm background comes from galaxies at z > 1.3.

astro-ph.CO↗