Nearby Galaxies at Low Frequencies: Processes and Probes

Transcription

1 Nearby Galaxies at Low Frequencies: Processes and Probes May 30 June 2, 2017 List of participants (as of May 10, 2017) 1. Aalto Susanne, Chalmers Univ. of Technology, Sweden 2. Basu Aritra, Max-Planck Institute for Radio Astronomy, Bonn, Germany 3. Black John, Chalmers Univ. of Technology, Sweden 4. Bourke Stephen, Onsala Space Observatory, Sweden 5. Carozzi Tobia, Onsala Space Observatory, Sweden 6. Conway John, Onsala Space Observatory, Sweden 7. Dettmar Ralf-Jürgen, Ruhr University, Bochum, Germany 8. Fletcher Andrew, Newcastle University, U.K. [at Obs] 9. Heald George, CSIRO Astronomy and Space Science, Perth, Australia 10. Heesen Volker, University of Hamburg, Germany 11. Horellou Cathy, Chalmers Univ. of Technology, Sweden 12. König Sabine, Chalmers Univ. of Technology, Sweden 13. Mao Sui Ann, Max-Planck Institute for Radio Astronomy, Bonn, Germany 14. Mulcahy David, Jodrell Bank Centre for Astrophysics, Manchester, U.K. 15. Nikiel-Wroczynski Blazej, Astron. Obs. Jagiellonian Univ., Krakow, Poland 16. Nilsson Anton, Onsala Space Observatory, Sweden 17. Paladino Rosita, INAF-Istituto di Radioastronomia, Bologna, Italy 18. Sridhar Sarrvesh, Kapteyn Institute, Groningen, The Netherlands 19. Stein Yelena, Bochum, Germany 20. Varenius Eskil, Onsala Space Observatory, Sweden The workshop is hosted by Onsala Space Observatory and the Division of Astronomy and Plasma Physics at the Department of Space, Earth and Environment, Chalmers. The workshop is sponsored by the Gothenburg Centre for Advanced Studies in Science and Technology (GoCAS).

2 Nearby Galaxies at Low Frequencies: Processes and Probes May 30 June 2, 2017 (as of May 10, 2017) Location:! Tue, Wed, and Fri morning at Chalmers University of Technology in Gothenburg, in the E building (Dept of Space, Earth and Environment 1 ), Hörsalsvägen 11. Room EDIT (3rd floor). The EDIT room will be available from 9:00 on Tuesday morning.! Thu at Onsala Space Observatory. Transportation will be arranged. Tuesday 30 May (Chalmers) Program 13:30-15:00: Intro + Spiral galaxies session [3 x 30 min] - Welcome. Goals of the meeting. Summary of the activities of the LOFAR Nearby Galaxies Working Groups (Cathy Horellou). - Exploring the low frequency nature of nearby galaxies with observations and modeling (David Mulcahy). - Spiral arms at low frequencies (Andrew Fletcher). 15:30-16:00 Coffee and tea break 16:00-17:30: Star-forming galaxies with LOFAR [3 x 30 min] - The low-frequency radio continuum star formation rate relation in nearby galaxies with LOFAR (Volker Heesen). - Subarcsecond imaging of nearby galaxies with LOFAR (Eskil Varenius). - Discussion. 1 formerly Department of Earth and Space Sciences (until May 1, 2017)

3 Wednesday 31 May (Chalmers) 9:00-10:30: Dwarf galaxies session [3 x 20 min + 30 min discussion] - New insights from high-resolution, low-frequency observations of the dwarf galaxy IC 10 (Aritra Basu). - LOFAR observations of IC 10 (Volker Heesen). - Other dwarf galaxies observed with LOFAR (Sarrvesh Sridhar). - Discussion. 10:30-11:00 Coffee and tea break 11:00-12:30 - TBA, Nearby galaxies news from Australia (George Heald). - Outflows in nearby galaxies, ALMA observations (Susanne Aalto). 12:30-14:00 Lunch break 14:00-15:30 Edge-on galaxies session! - The CHANG-ES survey of edge-on galaxies: overview, first results, and synergies with MKSP (Ralf-Jürgen Dettmar). - Nearby Galaxies with CHANG-ES: NGC 4013, NGC 4217 and NGC 4666 (Yelena Stein). - Discussion 15:30-16:00 Coffee and tea break 16:00-17:00 Discussions. To dinner by boat or tram/bus. 19:00-21:30: Dinner at the River Restaurant on the pier in Gothenburg.

4 Thursday 1 June (Onsala Space Observatory) 9:00:! Departure from Chalmers, transport to the Observatory. 9:45-11:00: Walk around the Observatory, coffee break 11:00-12:00: SKA Magnetism session 11:00-11:40: Probing interstellar magnetic fields with the SKA (Sui Ann Mao). 11:40-12:00: SKA Band 1 polarimetry modeling (Tobia Carozzi). 12:00-12:30: Discussion. 12:30-13:30: Lunch break 13:30-14:00: Presentation of Onsala Space Observatory (John Conway). 14:00-15:30: Magnetism session (continued)! - LOFAR observations of polarized radio sources in the M 51 field (Anton Nilsson).! - Can we expect regular magnetic fields in galaxy groups (and if so, can we use LOFAR to find them)? (Blazej Nikiel-Wroczynski).! - Discussion. 15:30-16:00 Coffee and tea break 16:00-18:00: Discussion of ongoing LOFAR projects - LOFAR - ALMA - SKA.! - LOFAR - erosita collaboration. - NGC 4258, M101 (Sarrvesh Sridhar). - M33 (Rosita Paladino). - Radio spectral energy distributions of nearby galaxies (Blazej Nikiel- Wroczynski, Krzysztof Chyzy).!

5 Friday 2 June (Chalmers, EDIT room) 9:00-12:30: Discussion. Topics will include: - Future work in cooperation, with and without new funding. Possibilities to increase wo/ man power, exchanges, extended visits, etc. - List of papers and timescales. - Future projects, new LOFAR and other observing proposals. - Exploitation of Tier 1 survey. - Polarization: - LOFAR polarization busy weeks. - Background polarized sources. - Collaboration between Magnetism and Surveys KSP (Nearby Galaxies; AGN; Clusters WGs) - Bologna LOFAR meeting. - TBA.

6 Nearby Galaxies at Low Frequencies: Processes and Probes May 30 June 2, 2017 List of talks and abstracts (in order of appearance; as of May 10, 2017) * Cathy Horellou: Practical info, goal of the meeting, and summary of the activities of the LOFAR Nearby Galaxies Working Groups * David Mulcahy: Exploring the low frequency nature of nearby galaxies with observations and modeling [Invited talk] Abstract: Observing nearby galaxies at low frequencies enables the study of weak magnetic fields in the extended disk and halo as Cosmic Ray electrons suffer less from synchrotron losses and thus are able to travel further. Until the advent of LOFAR, no such detailed studies could be performed due to the lack of resolution and calibration strategies for correcting for the ionosphere. With the aid of numerical models together with observations, we can further extract more accurate information on the cosmic ray electron propagation in determining what propagation process dominate in each galaxy in addition to the magnitude of this process. In this talk I will present recent LOFAR observations and modelling of the face-on galaxy M51 and the edge-on galaxy NGC891. We observe a significant extension in the disk of M51 compared to higher frequencies and are able to determine the main propagation process in this galaxy. We observe significant signs of absorption in the disk of NGC891, the first time observed in a normal star forming galaxy and finally we explore the Cosmic Ray propagation in the halo. * Andrew Fletcher: Spiral arms at low frequencies [Invited talk] Abstract: The ongoing debate about whether spiral arms are long-lived or temporary structures will be summarised. I will then outline some ideas about how low-frequency observations can be used to try to discriminate between theories. More generally, ways in which better information about arm and interarm differences can be obtained from low-frequency observations of nearby galaxies will be discussed. * Volker Heeren: The low-frequency radio continuum star formation rate relation in nearby galaxies with LOFAR [Invited talk] Abstract: We present first results of our survey of nearby galaxies with 140-MHz data from pointed observations and from the LOFAR 2-m Sky Survey (LoTSS). With the facet calibration technique we are now able to reach an rms noise level close to the thermal noise of ~150 µjy/beam at 7 10 arcsec spatial resolution. These maps are sensitivity matched with medium-deep (1 hr) observations of other state-of-the-art radio interferometers such as the Jansky VLA. We have selected our galaxies from the

7 SINGS and KINGFISH infrared surveys, which provide us with ample of ancillary data. The infrared maps from HERSCHEL and Spitzer can be combined with GALEX farultraviolet maps in order to construct reliable star-formation rate surface density maps, corrected for internal absorption by dust. Balmer Halpha maps can be used to separate the thermal radio continuum emission, although at 140 MHz we expect the thermal fraction to be small (< 10 per cent). We also have ancillary radio maps, both 1.4-GHz continuum maps from the WSRT SINGS survey, as well as HI line emission maps from the VLA THINGS survey. We also have selected some highly inclined (>80 degree) galaxies from the CHANG-ES survey with complementary Jansky VLA data at 1.5 and 6 GHz. These data can be used to study the spatially resolved radio continuum star formation rate (RC SFR) relation on a 1-kpc scale in a statically meaningful sample. As part of this study, we will explore the effects of cosmic-ray transport by diffusion in galactic discs, the relation between the magnetic field and gas density as well as gas kinematics and the vertical cosmic ray transport by advection in galactic winds. * Eskil Varenius: Subarcsecond imaging of nearby galaxies with LOFAR Abstract: LOFAR offers the unique capability of subarcsecond imaging at metre wavelengths. In this talk I will show subarcsecond images of multiple nearby galaxies obtained with LOFAR, and discuss a few scientific key results for each galaxy. I will focus on radio continuum observations using the LOFAR High Band Antennas (HBA), which can probe in great detail e.g. steep spectrum outflows and free-free absorption properties in nearby galaxies. I will also summarise some key limitations and possibilities of curent subarcsecond imaging techniques and given an outlook for future subarcsecond observations. * Aritra Basu: New insights from high-resolution, low-frequency observations of the dwarf galaxy IC 10 Abstract: Dwarf irregular galaxies are believed to be the building blocks of normal star forming galaxies in the nearby Universe. Detailed spatially resolved studies of these objects are imperative to understand both local and global properties of the interstellar medium in large galaxies. We have performed the highest sensitivity and angular resolution study at 320 MHz of the dwarf irregular galaxy IC 10, probing 45 pc spatial scales. The spatially resolved synchrotron emission, and mid- and far-infrared (MIR and FIR) emission at 24 and 70 micron, respectively, are well correlated but have different physical origin. Our study shows that the radio--fir relation arises due to a combination of magnetic field, dust temperature, and cosmic ray injection variations. Radio--MIR relation is a direct consequence of star formation, thereby providing valuable insights into the physics of the well known radio--infrared correlation. Further, these high spatial resolution observations indicate that an efficient (~10%) fluctuation dynamo, perhaps driven by mildly supersonic incompressible turbulence, is responsible for magnetic field amplification and thereby generating magnetic field strengths comparable to large spiral galaxies. The high efficiency of magnetic field amplification and its strong coupling with star formation rate likely sets up the radio--fir correlation in cosmologically young galaxies.

8 * Ralf-Jürgen Dettmar: The CHANG-ES survey of edge-on galaxies: overview, first results, and synergies with MKSP * Yelena Stein: Nearby Galaxies with CHANG-ES: NGC 4013, NGC 4217 and NGC 4666 Abstract: The CHANG-ES survey contains 35 edge-on spiral galaxies. These were observed with the Jansky Very Large Array (Jansky VLA, Socorro, New Mexico) in 1.5 GHz/20 cm and 6 GHz/6 cm with all polarization products and in different array configurations. I am presenting results on three CHANG-ES galaxies NGC 4013, NGC 4217 and NGC 4666 using the RM-Synthesis technique described by Brentjens et al. (2005) to derive polarization vectors and Rotation Measure (RM) maps. Additionally, I derived the magnetic fields and making a thermal/nonthermal decompostion of these galaxies. * Sui Ann Mao: Probing interstellar magnetic fields with the SKA [Invited talk] Abstract: The unprecedented sensitivity, angular resolution and broadband coverage of SKA polarimetric observations will allow us to address many long-standing mysteries in cosmic magnetism science. In this talk, I will present several ambitious galactic magnetism science topics that SKA polarization data will enable in the next decade. * Tobia Carozzi: SKA Band 1 polarimetry modeling Abstract: I will present the design of the SKA band 1 from the perspective of polarimetry. Most of the design is made using commercial electromagnetic simulators, but such S/W packages do not readily produce quantities and metrics for radio astronomical polarimetry. I will show what the polarimetry metrics are and how they live up to the SKA requirements. Furthermore I will present a S/W that I have developed so that these design models can be used by radio astronomers to polarimetrically calibrate their polarimetry datasets. * Anton Nilsson: LOFAR observations of polarized radio sources in the M 51 field We have reanalyzed the LOFAR observation of the M51 field by Mulcahy et al. (2014), focusing on polarization of the background sources. We use the False Discovery Rate method to constrain the proportion of falsely detected sources, finding 7 sources of which 5% (0.35) are expected to be false detections. * George Heald: TBA [Invited talk] Abstract: TBA * Susanne Aalto: Outflows in nearby galaxies, ALMA observations * Blazej Nikiel-Wroczynski: Can we expect regular magnetic fields in galaxy groups (and if so, can we use LOFAR to find them)? Abstract: The powerful method of Rotation Measure Synthesis allows to disentangle different agents that contribute to the total Faraday Rotation, hence allowing for a search of regular magnetic fields in various objects. We know that our own Galaxy, as

9 well as distant galaxies can be easily revealed; so are the clusters. Yet there is a question, whether we can expect such discoveries in galaxy groups? In my talk I will try to draw some estimations on the basis of 20 cm observations of the Stephan's Quintet, that could help us plan future LOFAR (and SKA, maybe?) polarisation observations of low-quantity galaxy systems.