An Empirical Relation Between The Large-Scale Magnetic Field And The Dynamical Mass In Galaxies

The origin and evolution of cosmic magnetic fields as well as the influence of the magnetic fields on the evolution of galaxies are unknown. Though not without challenges, the dynamo theory can explain the large-scale coherent magnetic fields which govern galaxies, but observational evidence for the theory is so far very scarce. Putting together the available data of non-interacting, non-cluster galaxies with known large-scale magnetic fields, we find a tight correlation between the integrated polarized flux density, S(PI), and the rotation speed, v(rot), of galaxies. This leads to an almost linear correlation between the large-scale magnetic field B and v(rot), assuming that the number of cosmic ray electrons is proportional to the star formation rate, and a super-linear correlation assuming equipartition between magnetic fields and cosmic rays. This correlation cannot be attributed to an active linear alpha-Omega dynamo, as no correlation holds with global shear or angular speed. It indicates instead a coupling between the large-scale magnetic field and the dynamical mass of the galaxies, B ~ M^(0.25-0.4). Hence, faster rotating and/or more massive galaxies have stronger large-scale magnetic fields. The observed B-v(rot) correlation shows that the anisotropic turbulent magnetic field dominates B in fast rotating galaxies as the turbulent magnetic field, coupled with gas, is enhanced and ordered due to the strong gas compression and/or local shear in these systems. This study supports an stationary condition for the large-scale magnetic field as long as the dynamical mass of galaxies is constant.Comment: 23 pages, 4 figures, accepted for publication in the Astrophysical Journal Letter

The DiskMass Survey. X. Radio synthesis imaging of spiral galaxies

We present results from 21 cm radio synthesis imaging of 28 spiral galaxies from the DiskMass Survey obtained with the VLA, WSRT, and GMRT facilities. We detail the observations and data reduction procedures and present a brief analysis of the radio data. We construct 21 cm continuum images, global HI emission-line profiles, column-density maps, velocity fields, and position-velocity diagrams. From these we determine star formation rates (SFRs), HI line widths, total HI masses, rotation curves, and azimuthally-averaged radial HI column-density profiles. All galaxies have an HI disk that extends beyond the readily observable stellar disk, with an average ratio and scatter of R_{HI}/R_{25}=1.35+/-0.22, and a majority of the galaxies appear to have a warped HI disk. A tight correlation exists between total HI mass and HI diameter, with the largest disks having a slightly lower average column density. Galaxies with relatively large HI disks tend to exhibit an enhanced stellar velocity dispersion at larger radii, suggesting the influence of the gas disk on the stellar dynamics in the outer regions of disk galaxies. We find a striking similarity among the radial HI surface density profiles, where the average, normalized radial profile of the late-type spirals is described surprisingly well with a Gaussian profile. These results can be used to estimate HI surface density profiles in galaxies that only have a total HI flux measurement. We compare our 21 cm radio continuum luminosities with 60 micron luminosities from IRAS observations for a subsample of 15 galaxies and find that these follow a tight radio-infrared relation, with a hint of a deviation from this relation at low luminosities. We also find a strong correlation between the average SFR surface density and the K-band surface brightness of the stellar disk.Comment: 22 pages + Appendix, 16 figures + Atlas, 5 tables. Accepted for publication in Astronomy & Astrophysic

The DiskMass Survey. VIII. On the Relationship Between Disk Stability and Star Formation

We study the relationship between the stability level of late-type galaxy disks and their star-formation activity using integral-field gaseous and stellar kinematic data. Specifically, we compare the two-component (gas+stars) stability parameter from Romeo & Wiegert (Q_RW), incorporating stellar kinematic data for the first time, and the star-formation rate estimated from 21cm continuum emission. We determine the stability level of each disk probabilistically using a Bayesian analysis of our data and a simple dynamical model. Our method incorporates the shape of the stellar velocity ellipsoid (SVE) and yields robust SVE measurements for over 90% of our sample. Averaging over this subsample, we find a meridional shape of sigma_z/sigma_R = 0.51^{+0.36}_{-0.25} for the SVE and, at 1.5 disk scale lengths, a stability parameter of Q_RW = 2.0 +/- 0.9. We also find that the disk-averaged star-formation-rate surface density (Sigma-dot_e,*) is correlated with the disk-averaged gas and stellar mass surface densities (Sigma_e,g and Sigma_e,*) and anti-correlated with Q_RW. We show that an anti-correlation between Sigma-dot_e,* and Q_RW can be predicted using empirical scaling relations, such that this outcome is consistent with well-established statistical properties of star-forming galaxies. Interestingly, Sigma-dot_e,* is not correlated with the gas-only or star-only Toomre parameters, demonstrating the merit of calculating a multi-component stability parameter when comparing to star-formation activity. Finally, our results are consistent with the Ostriker et al. model of self-regulated star-formation, which predicts Sigma-dot_e,*/Sigma_e,g/sqrt(Sigma_e,*). Based on this and other theoretical expectations, we discuss the possibility of a physical link between disk stability level and star-formation rate in light of our empirical results.Comment: Accepted for publication in ApJ. 15 pages, 6 figures, 2 tables. An electronic version of Table 1 is available by request, or at http://www.astro.rug.nl/~westfall/research/dmVIII_table1.tx

Inversion of droplet aerosol analyzer data for long-term aerosol–cloud interaction measurements

The droplet aerosol analyzer (DAA) was developed to study the influence of aerosol properties on clouds. It measures the ambient particle size of individual droplets and interstitial particles, the size of the dry (residual) particles after the evaporation of water vapor and the number concentration of the dry (residual) particles. A method was developed for the evaluation of DAA data to obtain the three-parameter data set: ambient particle diameter, dry (residual) particle diameter and number concentration. First results from in-cloud measurements performed on the summit of Mt. Brocken in Germany are presented. Various aspects of the cloud–aerosol data set are presented, such as the number concentration of interstitial particles and cloud droplets, the dry residue particle size distribution, droplet size distributions, scavenging ratios due to cloud droplet formation and size-dependent solute concentrations. This data set makes it possible to study clouds and the influence of the aerosol population on clouds

Showing Their True Colors? How EU Flag Display Affects Perceptions of Party Elites’ European Attachment

Evidence suggests that incidental national flag exposure activates nationalistic feelings and that incidental exposure to the EU flag can affect citizen attachments to Europe. However, we know little about what inferences citizens make based on the EU flag when they see it displayed by parties in an electoral context. To test the expectation that this display affects citizens’ evaluations of party elites’ EU attachment, we conducted a large-scale experiment embedded in a Swedish survey in which respondents were exposed to communications from one of the two main Swedish parties, containing or not containing the image of the flag. We find that simple visual display does little to move perceptions. However, if citizens perceive that a particular party displayed the flag, then they are more likely to evaluate its party elites as more attached to Europe

A mutation in POLE predisposing to a multi-tumour phenotype

Somatic mutations in the POLE gene encoding the catalytic subunit of DNA polymerase epsilon have been found in sporadic colorectal cancers (CRCs) and are most likely of importance in tumour development and/or progression. Recently, families with dominantly inherited colorectal adenomas and colorectal cancer were shown to have a causative heterozygous germline mutation in the proofreading exonuclease domain of POLE. The highly penetrant mutation was associated with predisposition to CRC only and no extra-colonic tumours were observed. We have identified a mutation in a large family in which the carriers not only developed CRC, they also demonstrate a highly penetrant predisposition to extra-intestinal tumours such as ovarian, endometrial and brain tumours. The mutation, NM_006231.2:c.1089C>A, p.Asn363Lys, also located in the proofreading exonuclease domain is directly involved in DNA binding. Theoretical prediction of the amino acid substitution suggests a profound effect of the substrate binding capability and a more severe impairment of the catalytic activity compared to the previously reported germline mutation. A possible genotype to phenotype correlation for deleterious mutations in POLE might exist that needs to be considered in the follow-up of mutation carriers

Short- and long-term stratospheric impact of smoke from the 2019–2020 Australian wildfires

At the end of December 2019 and beginning of 2020, massive firestorms in Australia formed pyrocumulonimbus clouds (pyroCbs) that acted like enormous smokestacks, pumping smoke to the upper troposphere and stratosphere. We study the smoke with data from four satellite-based sensors: the aerosol observation platforms CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization), OMPS-LP (Ozone Mapping and Profiler Suite Limb Profiler), and OMPS-NM (Ozone Mapping and Profiler Suite Nadir Mapper) and water vapor retrievals from MLS (Microwave Limb Sounder). Smoke was lofted to the upper troposphere and stratosphere during two events and spread almost exclusively within the extratropics. Smoke from the first event, starting 29 December, was injected directly into the stratosphere by pyroCbs, causing a rapid initial increase in AOD (aerosol optical depth). CALIOP identifies a rapid decline in this stratospheric smoke (half-life: 10 d), not captured in previous studies of the Australian fires, indicating photochemical processing of organic aerosol. This decay rate is in line with model predictions of mid-tropospheric organic aerosol loss by photolytic removal and is in agreement with our estimates of decay rates after the North American fires in August 2017. PyroCbs from the second event, 4 January, injected small amounts of smoke directly into the stratosphere. Large amounts of smoke were injected to the upper troposphere, from where it ascended into the stratosphere during several weeks, forming a second peak in the aerosol load. Hence, we find that pyroCbs can impact the stratospheric aerosol load both via direct injection to the stratosphere and through injection of smoke to the upper troposphere from where the smoke ascends into the stratosphere. The stratospheric AOD from the second-event fires decreased more slowly than the AOD from the first event, likely due to a combination of photolytic loss starting already in the troposphere and continued supply of smoke from the upper troposphere offsetting the loss rate. Together these injections yielded a major increase in the aerosol load for almost 1 year.</p