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).
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 Environment1), 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.
Program
Tuesday 30 May (Chalmers)
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)
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.
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 NikielWroczynski, Krzysztof Chyzy).
!
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.
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
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.
* 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
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.