Environment, Ram Pressure, and Shell Formation in HoII

Neutral hydrogen VLA D-array observations of the dwarf irregular galaxy HoII, a prototype galaxy for studies of shell formation, are presented. HI is detected to radii over 16' or 4 R_25, and M_HI=6.44x10^8 M_sun. The total HI map has a comet-like appearance suggesting that HoII is affected by ram pressure from an intragroup medium (IGM). A rotation curve corrected for asymmetric drift was derived and an analysis of the mass distribution yields a total mass 6.3x10^9 M_sun, of which about 80% is dark. HoII lies northeast of the M81 group's core, along with Kar52 (M81dwA) and UGC4483. No signs of interaction are observed and it is argued that HoII is part of the NGC2403 subgroup, infalling towards M81. A case is made for ram pressure stripping and an IGM in the M81 group. Stripping of the disk outer parts would require an IGM density n_IGM>=4.0x10^-6 atoms/cm^3 at the location of HoII. This corresponds to 1% of the virial mass of the group uniformly distributed over a volume just enclosing HoII and is consistent with the X-ray properties of small groups. It is argued that existing observations of HoII do not support self-propagating star formation scenarios, whereby the HI holes and shells are created by supernova explosions and stellar winds. Many HI holes are located in low surface density regions of the disk, where no star formation is expected or observed. Ram pressure has the capacity to enlarge preexisting holes and lower their creation energies, helping to bridge the gap between the observed star formation rate and that required to create the holes. (abridged)Comment: 43 pages, including 7 figures. 4 figures available as JPEG only. Complete manuscript including full resolution figures available at http://www.strw.leidenuniv.nl/~bureau/pub_list.html . Accepted for publication in The Astronomical Journa

Just a Taste: Lectures on Flavor Physics

We review the flavor structure of the Standard Model and the ways in which the flavor parameters are measured. This is an extended writeup of the TASI 2016 lectures on flavor physics. Earlier versions of these lectures were presented at pre-SUSY 2015 and Cornell University's Physics 7661 course in 2010.Comment: 138 pages, includes problems and solutions. To be published in the proceedings of TASI 201

The Evolution of Galaxies and Their Environment

The Third Teton Summer School on Astrophysics discussed the formation of galaxies, star formation in galaxies, galaxies and quasars at high red shift, and the intergalactic and intercluster medium and cooling flows. Observation and theoretical research on these topics was presented at the meeting and summaries of the contributed papers are included in this volume

Kinematics study of M81 and M82 Galaxies

The measurement of proper motion combined with the radial velocities, is an important tool for our understanding of the dynamics and evolution of galaxies in a group environment. One of the nearest group is the M$,$81 group at a distance of $sim$3.63$pm$0.34$,$Mpc citep{Freedmann1994}. It is a fascinating interacting galaxy system consisting of the galaxies M$,$81, M$,$82 and NGC$,$3077. In the first part of this work, we present the proper motions of M$,$81 and M$,$82 galaxies, derived from Very Long Baseline Interferometry (VLBI) radio observations. The observations were conducted in three epochs between 2007 and 2009 at X- (8.4$,$GHz) and U-band (15.3$,$GHz), and four epochs between 2007 and 2015 at K-band (22.2$,$GHz). On the one hand, the proper motion of M$,$81 relative to Milky Way was derived from background quasars (0945+6924, 0948+6848, 1004+6936). This was done by fitting a rectilinear motion to the position offsets of the quasars. The positions offsets of quasar 0948+6848 were found to be contaminated from its jet motion. We averaged the observed proper motion of the other two quasars to obtain the proper motion relative to the Sun of M$,$81 as $mu_{alpha}=0pm5.7,$$mu$as$,$yr$^{-1}$ and $mu_{delta}=mathrm{-22.5pm2.1},$$mu$as$,$yr$^{-1}$ at 22.2$,$GHz. Correcting for the peculiar motion of the Sun and the rotation of the Milky Way, this measurement yields a proper motion relative to the Milky Way of 10.2$pm$5.7$,$$mu$as$,$yr$^{-1}$ ($sim$179$pm$100$,$km$,$s$^{-1}$) towards the East and $-$24.5$pm$2.2$,$$mu$as$,$yr$^{-1}$ ($sim$$-$429$pm$39$,$km$,$s$^{-1}$) towards the North. With the total radial motion of M$,$81 towards the Milky Way reported as 73$pm$6$,$km$,$s$^{-1}$, we derive the total space velocity of M$,$81 relative to the MW as 471textpm 108$,$km$,$s$^{-1}$. On the other hand, the proper motion of M$,$82 is derived from observations of three H$_{2}$O masers located at opposite sides of its dynamic center. After correcting for the internal rotation of M$,$82, the average observed proper motion of the three maser features yields a proper motion relative to M81 of $mu_{alpha}$= 8.3$pm$5.5$,$$mu$as$,$yr$^{-1}$ (143$pm$95$,$km$,$s$^{-1}$) towards the East and $mu_{delta}$= 10.6$pm$4.3$,$$mu$as$,$yr$^{-1}$(182$pm$74$,$km$,$s$^{-1}$) towards the North. With a derived radial motion of 237$pm$6$,$km$,$s$^{-1}$ towards M81, we obtain its total space velocity to be 331$pm$120$,$km$,$s$^{-1}$ relative to M$,$81 galaxy. Moreover, with a separation distance between the centers being 38$,$kpc, M$,$82 is embedded in the dark matter halo of M$,$81, and can be considered bound. We therefore derive a lower limit of the mass of M$,$81 to be (4.8$pm$0.6)$times$10$^{11}$M$_{odot}$. In the second epoch of the observations of the water masers in M$,$82, a bright new radio source was discovered citep{Brunthaler2009a}, which turned out to be a new supernova. This led to a follow up program with the Very Large Array (VLA) and VLBI, which represents the second part of this thesis. We fit two models to the data, a simple power-law, $Spropto t^{beta}$, and a simplified Weiler model, yielding decline indices, $beta$, of $-$1.22$pm$0.07 (days 100 --1500) and $-$1.41$pm$0.02 (days 76--2167), respectively. The late time radio light curve evolution shows flux-density flares at $sim$970 and $sim$1400 days which are a factor of $sim$2 and $sim$4 higher than the expected flux, respectively. We derive the spectral index, $alpha$, $mathrm{S_{nu}proptonu^{alpha}}$, for frequencies 1.4 to 43$,$GHz for SN$,$2008iz during the period from $sim$430 to 2167 days after the supernova explosion. The value of $alpha$ shows no signs of evolution and it remains steep ($approx$$-$1) throughout the period, unlike that of the well-studied SN$,$1993J which started flattening at $sim$day 970. From the 4.8 and 8.4$,$GHz VLBI images, the supernova expansion is seen to start with a shell like structure that gets more and more asymmetric, then breaks up in the later epochs with bright structures dominating the southern part of the ring. This structural evolution differs significantly from that of SN$,$1993J which had remained circularly symmetric over 4000 days after the explosion. The VLBI 4.8 and 8.4$,$GHz images are used to derive a deceleration index, $m$, for SN$,$2008iz, of 0.86$pm$0.02, and the average expansion velocity between days 73 and 1400 as (12.1$pm$0.2)$times$10$^{3}$$,$km$,$s$^{-1}$. From the energy equipartition between magnetic fields and particles, we estimate the minimum total energy in relativistic particles and the magnetic fields during the supernova expansion and also find the magnetic field amplification factor for SN$,$2008iz to be in the range of 55 to 400

J-PLUS : a catalogue of globular cluster candidates around the M 81/M 82/NGC 3077 triplet of galaxies

Globular clusters (GCs) are proxies of the formation assemblies of their host galaxies. However, few studies exist targeting GC systems of spiral galaxies up to several effective radii. Through 12-band Javalambre Photometric Local Universe Survey (J-PLUS) imaging, we study the point sources around the M 81/M 82/NGC 3077 triplet in search of new GC candidates. We develop a tailored classification scheme to search for GC candidates based on their similarity to known GCs via a principal component analysis projection. Our method accounts for missing data and photometric errors. We report 642 new GC candidates in a region of 3.5 deg2 around the triplet, ranked according to their Gaia astrometric proper motions when available. We find tantalizing evidence for an overdensity of GC candidate sources forming a bridge connecting M 81 and M 82. Finally, the spatial distribution of the GC candidates (g − i) colours is consistent with halo/intra-cluster GCs, i.e. it gets bluer as they get further from the closest galaxy in the field. We further employ a regression-tree-based model to estimate the metallicity distribution of the GC candidates based on their J-PLUS bands. The metallicity distribution of the sample candidates is broad and displays a bump towards the metal-rich end. Our list increases the population of GC candidates around the triplet by threefold, stresses the usefulness of multiband surveys in finding these objects, and provides a testbed for further studies analysing their spatial distribution around nearby (spirals) galaxies

Critical technology elements (WP1)

The overall objective of the DigiMon project is to “accelerate the implementation of CCS by developing and demonstrating an affordable, flexible, societally embedded and smart Digital Monitoring early warning system”, for monitoring any CO2 storage reservoir and subsurface barrier system. Within the project the objective of WP1 was to develop individual technologies, data acquisition, analysis techniques and workflows in preparation for inclusion in the DigiMon system. The technologies and data processing techniques developed as part of WP1 include distributed fibre-optic sensing (DFOS) for seismic surveys and chemical sensing, 4D gravity and seafloor deformation measurements, a new seismic source and seismic monitoring survey design. For these technologies the key targets for WP1 were • Develop individual components of the system to raise individual technology readiness levels (TRLs), • Validate and optimise processing software for individual system components, • Develop an effective Distributed Acoustic Sensing (DAS) data interpretation workflow. This work was performed with the expected outcomes of • Raising the DAS TRL for passive seismic monitoring, • An assessment the feasibility of using Distributed Chemical Sensing (DCS) for CO2 detection, • Reducing the cost of 4D gravity and seafloor deformation measurements