Practical Modeling of Large-Scale Galactic Magnetic Fields: Status and Prospects

This is a review of the status of efforts to model the large-scale Galactic magnetic field (GMF). Though important for a variety of astrophysical processes, the GMF remains poorly understood despite some interesting new tracers being used in the field. Though we still have too many models that might fit the data, this is not to say that the field has not developed in the last few years. In particular, surveys of polarized dust have given us a new observable that is complementary to the more traditional radio tracers, and a variety of other new tracers and related measurements are becoming available to improve current modeling. This paper reviews: the tracers available; the models that have been studied; what has been learned so far; what the caveats and outstanding issues are; and one opinion of where the most promising future avenues of exploration lie.Comment: Published in Galaxies special issue "New Perspectives on Galactic Magnetism" (with minor formatting differences). v2 fixes some reference

Foreground Analysis Using Cross-Correlations of External Templates on the 7-year WMAP data

WMAP data when combined with ancillary data on free-free, synchrotron and dust allow an improved understanding of the spectrum of emission from each of these components. Here we examine the sky variation at intermediate and high latitudes using a cross-correlation technique. In particular, we compare the observed emission in several large partitions of the sky plus 33 selected sky regions to three "standard" templates. The regions are selected using a criterion based on the morphology of these template maps. The synchrotron emission shows evidence of steepening between GHz frequencies and the \emph{WMAP} bands. There are indications of spectral index variations across the sky but the current data are not precise enough to accurately quantify this from region-to-region. The emission correlated with the $H_{\alpha}$ template shows clear evidence of deviation from a free-free spectrum. The emission can be decomposed into a contribution from both free-free and spinning dust in the warm ionised medium of the Galaxy. The derived free-free emissivity corresponds to a mean electron temperature of $\sim 6000$ K, although the value depends critically on the impact of dust absorption on the $H_{\alpha}$ intensity. The WIM spinning dust emission has a peak emission in intensity in the range 40--50 GHz. The anomalous microwave emission associated with dust is detected at high significance in most of the 33 fields studied. The anomalous emission correlates well with the Finkbeiner et al. (1999) model 8 predictions (FDS8) at 94 GHz, and is well described globally by a power-law emission model with an effective spectral index between 20 and 60 GHz of $\beta \approx -2.7$. It is clear that attempts to explain the emission by spinning dust models require multiple components, which presumably relates to a complex mix of emission regions along a given line-of-sight.Comment: 31 pages, 14 figure

Helicity in the large-scale Galactic magnetic field

17 pages, 11 figures, Accepted to MNRAS 28 September 2020International audienceWe search for observational signatures of magnetic helicity in data from all-sky radio polarization surveys of the Milky Way Galaxy. Such a detection would help confirm the dynamo origin of the field and may provide new observational constraints for its shape. We compare our observational results to simulated observations for both a simple helical field, and for a more complex field that comes from a solution to the dynamo equation. Our simulated observations show that the large-scale helicity of a magnetic field is reflected in the large-scale structure of the fractional polarization derived from the observed synchrotron radiation and Faraday depth of the diffuse Galactic synchrotron emission. Comparing the models with the observations provides evidence for the presence of a quadrupolar magnetic field with a vertical component that is pointing away from the observer in both hemispheres of the Milky Way Galaxy. Since there is no reason to believe that the Galactic magnetic field is unusual when compared to other galaxies, this result provides further support for the dynamo origin of large-scale magnetic fields in galaxies

SKA studies of in-situ synchrotron radiation from molecular clouds

Observations of the properties of dense molecular clouds are critical in understanding the process of star-formation. One of the most important, but least understood, is the role of the magnetic fields. We discuss the possibility of using high-resolution, high-sensitivity radio observations with the SKA to measure for the first time the in-situ synchrotron radiation from these molecular clouds. If the cosmic-ray (CR) particles penetrate clouds as expected, then we can measure the B-field strength directly using radio data. So far, this signature has never been detected from the collapsing clouds themselves and would be a unique probe of the magnetic field. Dense cores are typically ∼0:05 pc in size, corresponding to ∼arcsec at ∼kpc distances, and flux density estimates are ∼mJy at 1 GHz. The SKA should be able to readily detect directly, for the first time, along lines-of-sight that are not contaminated by thermal emission or complex foreground/background synchrotron emission. Polarised synchrotron may also be detectable providing additional information about the regular/turbulent fields

Astro2020 APC White Paper: The need for better tools to design future CMB experiments

International audienceThis white paper addresses key challenges for the design of next-decade Cosmic Microwave Background (CMB) experiments, and for assessing their capability to extract cosmological information from CMB polarization. We focus here on the challenges posed by foreground emission, CMB lensing, and instrumental systematics to detect the signal that arises from gravitational waves sourced by inflation and parameterized by $r$, at the level of $r \sim 10^{-3}$ or lower, as proposed for future observational efforts. We argue that more accurate and robust analysis and simulation tools are required for these experiments to realize their promise. We are optimistic that the capability to simulate the joint impact of foregrounds, CMB lensing, and systematics can be developed to the level necessary to support the design of a space mission at $r \sim 10^{-4}$ in a few years. We make the case here for supporting such work. Although ground-based efforts present additional challenges (e.g., atmosphere, ground pickup), which are not addressed here, they would also benefit from these improved simulation capabilities

TOI-150b and TOI-163b: two transiting hot Jupiters, one eccentric and one inflated, revealed by TESS near and at the edge of the JWST CVZ

peer reviewedWe present the discovery of TYC9191-519-1b (TOI-150b, TIC 271893367) and HD271181b (TOI-163b, TIC 179317684), two hot Jupiters initially detected using 30-min cadence Transiting Exoplanet Survey Satellite (TESS) photometry from Sector 1 and thoroughly characterized through follow-up photometry (CHAT, Hazelwood, LCO/CTIO, El Sauce, TRAPPIST-S), high- resolution spectroscopy (FEROS, CORALIE), and speckle imaging (Gemini/DSSI), confirming the planetary nature of the two signals. A simultaneous joint fit of photometry and radial velocity using a new fitting package JULIET reveals that TOI-150b is a 1.254± 0.016 {R}_ {J}, massive (2.61^{+0.19}_{-0.12} {M}_ {J}) hot Jupiter in a 5.857-d orbit, while TOI-163b is an inflated (R_ {P} = 1.478^{+0.022}_{-0.029} R_ {J}, M_ {P} = 1.219± 0.11 {M}_ {J}) hot Jupiter on a P = 4.231-d orbit; both planets orbit F-type stars. A particularly interesting result is that TOI-150b shows an eccentric orbit (e=0.262^{+0.045}_{-0.037}), which is quite uncommon among hot Jupiters. We estimate that this is consistent, however, with the circularization time-scale, which is slightly larger than the age of the system. These two hot Jupiters are both prime candidates for further characterization - in particular, both are excellent candidates for determining spin-orbit alignments via the Rossiter-McLaughlin (RM) effect and for characterizing atmospheric thermal structures using secondary eclipse observations considering they are both located closely to the James Webb Space Telescope (JWST) Continuous Viewing Zone (CVZ)