arXiv subjects

Philip Schmidt

Publications and source records attributed to Philip Schmidt.

At least 19 recordsLinked to original sources

arXiv2024

Remote sensing of a levitated superconductor with a flux-tunable microwave cavity

We present a cavity-electromechanical system comprising a superconducting quantum interference device which is embedded in a microwave resonator and coupled via a pick-up loop to a 6 $\mu$g magnetically-levitated superconducting sphere. The motion of the sphere in the magnetic trap induces a frequency shift in the SQUID-cavity system. We use microwave spectroscopy to characterize the system, and we demonstrate that the electromechanical interaction is tunable. The measured displacement sensitivity of $10^{-7} \, \mathrm{m} / \sqrt{\mathrm{Hz}}$, defines a path towards ground-state cooling of levitated particles with Planck-scale masses at millikelvin environment temperatures.

quant-ph↗

arXiv2023

High-Q magnetic levitation and control of superconducting microspheres at millikelvin temperatures

We report the levitation of a superconducting lead-tin sphere with 100 micrometer diameter (corresponding to a mass of 5.6 micrograms) in a static magnetic trap formed by two coils in an anti-Helmholtz configuration, with adjustable resonance frequencies up to 240 hertz. The center-of-mass motion of the sphere is monitored magnetically using a dc superconducting quantum interference device as well as optically and exhibits quality factors of up to 2.6e7. We also demonstrate 3D magnetic feedback control of the sphere's motion. The setup is housed in a dilution refrigerator operating at 15 millikelvin. By implementing a cryogenic vibration isolation system we can attenuate environmental vibrations at 200 hertz by approximately seven orders of magnitude. The combination of low temperature, large mass and high quality factor as well as adjustable resonance frequencies provides a promising platform for testing quantum physics in previously unexplored regimes with high mass and long coherence times.

quant-ph↗

arXiv2021

Mechanical frequency control in inductively coupled electromechanical systems

Nano-electromechanical systems implement the opto-mechanical interaction combining electromagnetic circuits and mechanical elements. We investigate an inductively coupled nano-electromechanical system, where a superconducting quantum interference device (SQUID) realizes the coupling. We show that the resonance frequency of the mechanically compliant string embedded into the SQUID loop can be controlled in two different ways: (i) the bias magnetic flux applied perpendicular to the SQUID loop, (ii) the magnitude of the in-plane bias magnetic field contributing to the nano-electromechanical coupling. These findings are quantitatively explained by the inductive interaction contributing to the effective spring constant of the mechanical resonator. In addition, we observe a residual field dependent shift of the mechanical resonance frequency, which we attribute to the finite flux pinning of vortices trapped in the magnetic field biased nanostring.

quant-ph↗

arXiv2020

CHANG-ES XXII: Coherent Magnetic Fields in the Halos of Spiral Galaxies

Context. The magnetic field in spiral galaxies is known to have a large-scale spiral structure along the galactic disk and is observed as X-shaped in the halo of some galaxies. While the disk field can be well explained by dynamo action, the 3-dimensional structure of the halo field and its physical nature is still unclear. Aims. As first steps towards understanding the halo fields, we want to clarify whether the observed X-shaped field is a wide-spread pattern in the halos of spiral galaxies and whether these halo fields are just turbulent fields ordered by compression or shear (anisotropic turbulent fields), or have a large-scale regular structure. Methods. The analysis of the Faraday rotation in the halo is the tool to discern anisotropic turbulent fields from large-scale magnetic fields. This, however, has been challenging until recently because of the faint halo emission in linear polarization. Our sensitive VLA broadband observations C-band and L-band of 35 spiral galaxies seen edge-on (called CHANG-ES) allowed us to perform RM-synthesis in their halos and to analyze the results. We further accomplished a stacking of the observed polarization maps of 28 CHANG-ES galaxies at C-band. Results. Though the stacked edge-on galaxies were of different Hubble types, star formation and interaction activities, the stacked image clearly reveals an X-shaped structure of the apparent magnetic field. We detected a large-scale (coherent) halo field in all 16 galaxies that have extended polarized intensity in their halos. We detected large-scale field reversals in all of their halos. In six galaxies they are along lines about vertical to the galactic midplane (vertical RMTL) with about 2 kpc separation. Only in NGC 3044 and possibly in NGC 3448 we observed vertical giant magnetic ropes (GMRs) similar to those detected recently in NGC 4631.

astro-ph.GA↗

arXiv2019

Sideband-resolved resonator electromechanics on the single-photon level based on a nonlinear Josephson inductance

Light-matter interaction in optomechanical systems is the foundation for ultra-sensitive detection schemes [1,2] as well as the generation of phononic and photonic quantum states [3-10]. Electromechanical systems realize this optomechanical interaction in the microwave regime. In this context, capacitive coupling arrangements demonstrated interaction rates of up to 280 Hz [11]. Complementary, early proposals [12-15] and experiments [16,17] suggest that inductive coupling schemes are tunable and have the potential to reach the vacuum strong-coupling regime. Here, we follow the latter approach by integrating a partly suspended superconducting quantum interference device (SQUID) into a microwave resonator. The mechanical displacement translates into a time varying flux in the SQUID loop, thereby providing an inductive electromechanical coupling. We demonstrate a sideband-resolved electromechanical system with a tunable vacuum coupling rate of up to 1.62 kHz, realizing sub-aN Hz-1/2 force sensitivities. Moreover, we study the frequency splitting of the microwave resonator for large mechanical amplitudes confirming the large coupling. The presented inductive coupling scheme shows the high potential of SQUID-based electromechanics for targeting the full wealth of the intrinsically nonlinear optomechanics Hamiltonian.

quant-ph↗

arXiv2019

CHANG-ES XVI: An in-depth view of the cosmic-ray transport in the edge-on spiral galaxies NGC 891 and NGC 4565

Cosmic-ray electrons (CREs) originating from the star-forming discs of spiral galaxies frequently form extended radio haloes that are best observable in edge-on galaxies. For the present study we selected two nearby edge-on galaxies from the CHANG-ES survey, NGC 891 and 4565, which differ largely in halo size and SFR. To figure out how such differences are related to the CRE transport in disc and halo, we use wide-band 1.5 and 6 GHz VLA observations obtained in the B, C, and D configurations, and combine the 6 GHz images with Effelsberg observations to correct for missing short spacings. We study the spatially resolved non-thermal spectral index distribution in terms of CRE spectral ageing, compute total magnetic field strengths assuming energy equipartition between CRs and magnetic fields, and also determine synchrotron scale heights. Based on the vertical profiles of synchrotron intensity and spectral index, we create purely advective and purely diffusive CRE transport models by numerically solving the 1D diffusion-loss equation. In particular, we investigate for the first time the radial dependence of synchrotron and magnetic field scale heights, advection speeds and diffusion coefficients in these two galaxies. We find the spectral index distribution of NGC 891 to be mostly consistent with continuous CRE injection, while in NGC 4565 the local synchrotron spectra are more in line with discrete-epoch CRE injection (JP or KP models). This implies that CRE injection timescales are lower than the synchrotron cooling timescales. The scale height of NGC 891 increases with radius, indicating that synchrotron losses are significant. NGC 891 is probably dominated by advective CRE transport at a velocity of $\gtrsim150\,\mathrm{km\,s^{-1}}$. In contrast, NGC 4565 is diffusion-dominated up to $z=1$ kpc or higher, with a diffusion coefficient of $\geq2\times10^{28}\,\mathrm{cm^2\,s^{-1}}$.

astro-ph.GA↗

arXiv2019

CHANG-ES XX. High Resolution Radio Continuum Images of Edge-on Galaxies and their AGNs -- Data Release 3

The CHANG-ES galaxy sample consists of 35 nearby edge-on galaxies that have been observed using the VLA at 1.6 GHz and 6.0 GHz. Here we present the 3rd data release of our sample, namely the B-configuration 1.6 GHz sample. In addition, we make available the {\it band-to-band} spectral index maps between 1.6 GHz and 6.0 GHz, the latter taken in the matching resolution C-configuration. The images can be downloaded from https://www.queensu.ca/changes. These are our highest resolution images ($\approx$ 3 arcsec) and we examine the possible presence of low luminosity active galactic nuclei in the sample as well as some in-disk structure. New features can be seen in the spectral index maps that are masked in the total intensity emission, including hidden spiral arms in NGC~3448 and two previously unknown radio lobes on either side of the nucleus of NGC~3628. Our AGN detection rate, using only radio criteria, is 55\% which we take as a lower limit because some weaker embedded AGNs are likely present which could be revealed at higher resolution. Archival XMM-Newton data were used to search for further fingerprints of the AGNs in the studied sample. In galaxy disks, discrete regions of flat spectral index are seen, likely due to a thermal emission fraction that is higher than the global average.

astro-ph.GA↗

arXiv2018

Wearable affect and stress recognition: A review

Affect recognition aims to detect a person's affective state based on observables, with the goal to e.g. provide reasoning for decision making or support mental wellbeing. Recently, besides approaches based on audio, visual or text information, solutions relying on wearable sensors as observables (recording mainly physiological and inertial parameters) have received increasing attention. Wearable systems offer an ideal platform for long-term affect recognition applications due to their rich functionality and form factor. However, existing literature lacks a comprehensive overview of state-of-the-art research in wearable-based affect recognition. Therefore, the aim of this paper is to provide a broad overview and in-depth understanding of the theoretical background, methods, and best practices of wearable affect and stress recognition. We summarise psychological models, and detail affect-related physiological changes and their measurement with wearables. We outline lab protocols eliciting affective states, and provide guidelines for ground truth generation in field studies. We also describe the standard data processing chain, and review common approaches to preprocessing, feature extraction, and classification. By providing a comprehensive summary of the state-of-the-art and guidelines to various aspects, we would like to enable other researchers in the field of affect recognition to conduct and evaluate user studies and develop wearable systems.

cs.HC↗

arXiv2018

Ultrawide-range photon number calibration using a hybrid system combining nano-electromechanics and superconducting circuit quantum electrodynamics

We present a hybrid system consisting of a superconducting coplanar waveguide resonator coupled to a nanomechanical string and a transmon qubit acting as nonlinear circuit element. We perform spectroscopy for both the transmon qubit and the nanomechanical string. Measuring the ac-Stark shift on the transmon qubit as well as the electromechanically induced absorption on the string allows us to determine the average photon number in the microwave resonator in both the low and high power regimes. In this way, we measure photon numbers that are up to nine orders of magnitude apart. We find a quantitative agreement between the calibration of photon numbers in the microwave resonator using the two methods. Our experiments demonstrate the successful combination of superconducting circuit quantum electrodynamics and nano-electromechanics on a single chip.

quant-ph↗

arXiv2018

CHANG-ES XI: Circular Polarization in the Cores of Nearby Galaxies

We detect 5 galaxies in the CHANG-ES (Continuum Halos in Nearby Galaxies -- an EVLA Survey) sample that show circular polarization (CP) at L-band in our high resolution data sets. Two of the galaxies (NGC~4388 and NGC~4845) show strong Stokes $V/I\,\equiv\,m_C\,\sim\,2$\%, two (NGC~660 and NGC~3628) have values of $m_C\sim \,0.3$\%, and NGC~3079 is a marginal detection at $m_C\sim \,0.2$\%. The two strongest $m_C$ galaxies also have the most luminous X-ray cores and the strongest internal absorption in X-rays. We have expanded on our previous Faraday conversion interpretation and analysis and provide analytical expressions for the expected $V$ signal for a general case in which the cosmic ray electron energy spectral index can take on any value. We provide examples as to how such expressions could be used to estimate magnetic field strengths and the lower energy cutoff for CR electrons. Four out of our detections are {\it resolved}, showing unique structures, including a {\it jet} in NGC~4388 and a CP `conversion disk' in NGC~4845. The conversion disk is inclined to the galactic disk but is perpendicular to a possible outflow direction. Such CP structures have never before been seen in any galaxy to our knowledge. None of the galaxy cores show linear polarization at L-band. Thus CP may provide a unique probe of physical conditions deep into radio AGNs.

astro-ph.GA↗

arXiv2018

CHANG-ES X: Spatially-resolved Separation of Thermal Contribution from Radio Continuum Emission in Edge-on Galaxies

We analyze the application of star formation rate (SFR) calibrations using H$α$ and 22 micron infrared imaging data in predicting the thermal radio component for a test sample of 3 edge-on galaxies (NGC 891, NGC 3044, and NGC 4631) in the Continuum Halos in Nearby Galaxies -- an EVLA Survey (CHANG-ES). We use a mixture of H$α$ and 24 micron calibration from Calzetti et al. (2007), and a linear 22 micron only calibration from Jarrett et al. (2013) on the test sample. We apply these relations on a pixel-to-pixel basis to create thermal prediction maps in the two CHANG-ES bands: L- and C-band (1.5 GHz and 6.0 GHz, respectively). We analyze the resulting non-thermal spectral index maps, and find a characteristic steepening of the non-thermal spectral index with vertical distance from the disk after application of all methods. We find possible evidence of extinction in the 22 micron data as compared to 70 micron Spitzer Multband Imaging Photometer (MIPS) imaging in NGC 891. We analyze a larger sample of edge-on and face-on galaxy 25 micron to 100 micron flux ratios, and find that the ratios for edge-ons are systematically lower by a factor of 1.36, a result we attribute to excess extinction in the mid-IR in edge-ons. We introduce a new calibration for correcting the H$α$ luminosity for dust when galaxies are edge-on or very dusty.

astro-ph.GA↗

arXiv2017

The NOD3 software package: A graphical user interface-supported reduction package for single-dish radio continuum and polarisation observations

The venerable NOD2 data reduction software package for single-dish radio continuum observations, developed for use at the 100-m Effelsberg radio telescope, has been successfully applied over many decades. Modern computing facilities call for a new design. We aim to develop an interactive software tool with a graphical user interface (GUI) for the reduction of single-dish radio continuum maps. Special effort is given on the reduction of distortions along the scanning direction (scanning effects) by combining maps scanned in orthogonal directions or dual- or multiple-horn observations that need to be processed in a restoration procedure. The package should also process polarisation data and offer the possibility to include special tasks written by the individual user. Based on the ideas of the NOD2 package we developed NOD3, which includes all necessary tasks from the raw maps to the final maps in total intensity and linear polarisation. Furthermore, plot routines and several methods for map analysis are available. The NOD3 package is written in Python which allows to extend the package by additional tasks. The required data format for the input maps is FITS. NOD3 is a sophisticated tool to process and analyse maps from single-dish observations that are affected by 'scanning effects' due to clouds, receiver instabilities, or radio-frequency interference (RFI). The 'basket-weaving' tool combines orthogonally scanned maps to a final map that is almost free of scanning effects. The new restoration tool for dual-beam observations reduces the noise by a factor of about two compared to the NOD2 version. Combining single-dish with interferometer data in the map plane ensures the full recovery of the total flux density.

astro-ph.IM↗

arXiv2016

Frequency control and coherent excitation transfer in a nanostring resonator network

Coupling, synchronization, and non-linear dynamics of resonator modes are omnipresent in nature and highly relevant for a multitude of applications ranging from lasers to Josephson arrays and spin torque oscillators. Nanomechanical resonators are ideal candidates to study these effects on a fundamental level and to realize all-mechanical platforms for information processing and storage. For larger resonator networks, however, this requires the ability to tune the mode frequencies selectively and to operate the resonators in the strong coupling regime. Here, we present a proof-of-principle realization of a resonator network consisting of two high-quality nanostring resonators, coupled mechanically by a shared support. First, we demonstrate that we can control the fundamental mode frequencies of both nanostrings independently by a strong drive tone resonant with one of the higher harmonics of the network, rendering local control gates redundant. The tuning mechanism relies on an effective increase of the pre-stress in a highly excited nanostring, known as geometric nonlinearity. Using this selective frequency control of the individual nanomechanical resonators, we investigate the coherent dynamics of the resonator network, which is a classical model system showing several of the characteristic features of strongly coupled quantum systems. In particular, we demonstrate mode splitting, classical Rabi oscillations, as well as adiabatic and diabatic transitions between the coupled states representing the classical analog of Landau-Zener tunneling. Therefore, this coupling and tuning concept opens the path to a selective phonon transfer between two spatially separated mechanical resonators.

cond-mat.mes-hall↗

arXiv2016

CHANG-ES VIII: Uncovering Hidden AGN Activity in Radio Polarization

We report on C-band (5 - 7 GHz) observations of the galaxy, NGC~2992, from the CHANG-ES sample. This galaxy displays an embedded nuclear double-lobed radio morphology within its spiral disk, as revealed in linearly polarized emission but {\it not} in total intensity emission. The radio lobes are kpc-sized, similar to what has been observed in the past for other Seyfert galaxies, and show ordered magnetic fields. NGC~2992 has shown previous evidence for AGN-related activity, but not the linearly polarized radio features that we present here. We draw attention to this galaxy as the first clear example (and prototype) of bipolar radio outflow that is revealed in linearly polarized emission only. Such polarization observations, which are unobscured by dust, provide a new tool for uncovering hidden weak AGN activity which may otherwise be masked by brighter unpolarized emission within which it is embedded. The radio lobes observed in NGC~2992 are interacting with the surrounding interstellar medium and offer new opportunities to investigate the interactions between nuclear outflows and the ISM in nearby galaxies. We also compare the radio emission with a new CHANDRA X-ray image of this galaxy. A new CHANG-ES image of NGC~3079 is also briefly shown as another example as to how much more obvious radio lobes appear in linear polarization as opposed to total intensity.

astro-ph.GA↗

arXiv2015

CHANG-ES IV: Radio continuum emission of 35 edge-on galaxies observed with the Karl G. Jansky Very Large Array in D-configuration, Data Release 1

We present the first part of the observations made for the Continuum Halos in Nearby Galaxies, an EVLA Survey (CHANG-ES) project. The aim of the CHANG-ES project is to study and characterize the nature of radio halos, their prevalence as well as their magnetic fields, and the cosmic rays illuminating these fields. This paper reports observations with the compact D configuration of the Karl G. Jansky Very Large Array (VLA) for the sample of 35 nearby edge-on galaxies of CHANG-ES. With the new wide bandwidth capabilities of the VLA, an unprecedented sensitivity was achieved for all polarization products. The beam resolution is an average of 9.6" and 36" with noise levels reaching approximately 6 and 30 microJy per beam for C- and L-bands, respectively (robust weighting). We present intensity maps in these two frequency bands (C and L), with different weightings, as well as spectral index maps, polarization maps, and new measurements of star formation rates (SFRs). The data products described herein are available to the public in the CHANG-ES data release available at www.queensu.ca/changes. We also present evidence of a trend among galaxies with larger halos having higher SFR surface density, and we show, for the first time, a radio continuum image of the median galaxy, taking advantage of the collective signal-to-noise ratio of 30 of our galaxies. This image shows clearly that a typical spiral galaxy is surrounded by a halo of magnetic fields and cosmic rays.

astro-ph.GA↗

arXiv2015

Synchrotron spectral index and interstellar medium densities of star-forming galaxies

The spectral index of synchrotron emission is an important parameter in understanding the properties of cosmic ray electrons (CREs) and the interstellar medium (ISM). We determine the synchrotron spectral index ($α_{\rm nt}$) of four nearby star-forming galaxies, namely NGC 4736, NGC 5055, NGC 5236 and NGC 6946 at sub-kpc linear scales. The $α_{\rm nt}$ was determined between 0.33 and 1.4 GHz for all the galaxies. We find the spectral index to be flatter ($\gtrsim -0.7$) in regions with total neutral (atomic + molecular) gas surface density, $Σ_{\rm gas} \gtrsim \rm 50~M_\odot pc^{-2}$, typically in the arms and inner parts of the galaxies. In regions with $Σ_{\rm gas} \lesssim \rm 50~M_\odot pc^{-2}$, especially in the interarm and outer regions of the galaxies, the spectral index steepens sharply to $<-1.0$. The flattening of $α_{\rm nt}$ is unlikely to be caused due to thermal free--free absorption at 0.33 GHz. Our result is consistent with the scenario where the CREs emitting at frequencies below $\sim0.3$ GHz are dominated by bremsstrahlung and/or ionization losses. For denser medium ($Σ_{\rm gas} \gtrsim \rm 200~M_\odot pc^{-2}$), having strong magnetic fields ($\sim 30~μ$G), $α_{\rm nt}$ is seen to be flatter than $-0.5$, perhaps caused due to ionization losses. We find that, due to the clumpy nature of the ISM, such dense regions cover only a small fraction of the galaxy ($\lesssim5$ percent). Thus, the galaxy-integrated spectrum may not show indication of such loss mechanisms and remain a power-law over a wide range of radio frequencies (between $\sim 0.1$ to 10 GHz).

astro-ph.GA↗

arXiv2013

Structure and Kinematics of the Nearby Dwarf Galaxy UGCA 105

Owing to their shallow stellar potential, dwarf galaxies possess thick gas disks, which makes them good candidates for studies of the galactic vertical kinematical structure. We present 21 cm line observations of the isolated nearby dwarf irregular galaxy UGCA 105, taken with the Westerbork Synthesis Radio Telescope (WSRT), and analyse the geometry of its neutral hydrogen (HI) disk and its kinematics. The galaxy shows a fragmented HI distribution. It is more extended than the optical disk, and hence allows one to determine its kinematics out to very large galacto-centric distances. The HI kinematics and morphology are well-ordered and symmetric for an irregular galaxy. The HI is sufficiently extended to observe a substantial amount of differential rotation. Moreover, UGCA 105 shows strong signatures for the presence of a kinematically anomalous gas component. Performing tilted-ring modelling by use of the least-squares fitting routine TiRiFiC, we found that the HI disk of UGCA 105 has a moderately warped and diffuse outermost part. Probing a wide range of parameter combinations, we succeeded in modelling the data cube as a disk with a strong vertical gradient in rotation velocity ($\approx -60\,\rm km\,s^{-1}\,kpc^{-1}$), as well as vertically increasing inwards motion ($\approx -70\,\rm km\,s^{-1}\,kpc^{-1}$) within the radius of the stellar disk. The inferred radial gas inflow amounts to $0.06\,\rm M_\odot \rm yr^{-1}$, which is similar to the star formation rate of the galaxy. The observed kinematics are hence compatible with direct or indirect accretion from the intergalactic medium, an extreme backflow of material that has formerly been expelled from the disk, or a combination of both.

astro-ph.GA↗

arXiv2012

Continuum Halos in Nearby Galaxies -- an EVLA Survey (CHANG-ES) -- I: Introduction to the Survey

We introduce a new survey to map the radio continuum halos of a sample of 35 edge-on spiral galaxies at 1.5 GHz and 6 GHz in all polarization products. The survey is exploiting the new wide bandwidth capabilities of the Karl G. Jansky Very Large Array (i.e. the Expanded Very Large Array, or EVLA) in a variety of array configurations (B, C, and D) in order to compile the most comprehensive data set yet obtained for the study of radio halo properties. This is the first survey of radio halos to include all polarization products. In this first paper, we outline the scientific motivation of the survey, the specific science goals, and the expected improvements in noise levels and spatial coverage from the survey. Our goals include investigating the physical conditions and origin of halos, characterizing cosmic ray transport and wind speed, measuring Faraday rotation and mapping the magnetic field, probing the in-disk and extraplanar far-infrared - radio continuum relation, and reconciling non-thermal radio emission with high-energy gamma-ray models. The sample size allows us to search for correlations between radio halos and other properties, including environment, star formation rate, and the presence of AGNs. In a companion paper (Paper II) we outline the data reduction steps and present the first results of the survey for the galaxy, NGC 4631.

astro-ph.CO↗