288 research outputs found
Multiwavelength study of the radio emission from a tight galaxy pair Arp 143
We present results of the recent low-frequency radio observations of a tight
galaxy pair Arp 143 at 234 and 612 MHz. These data are analysed together with
the archive data at 1490, 4860, 8440, and 14940 MHz. From the analysis of the
radio emission we derive constraints on the age of the radio emitting
structures as well as on the properties of their magnetic field. We show that
the collisional ring of NGC 2445 hosts strong magnetic fields (reaching 12
G in its northwestern part) manifesting as a steep--spectrum, nonthermal
radiation at radio frequencies. The spectral age of this structure is higher
than estimates derived for the star-forming regions from the H
distribution, suggesting that the radio emission might have a different origin.
The galactic core is of a very young spectral age, suggesting an ongoing
starburst activity. Additionally we identify a possible ridge of emission
between the ring galaxy and its elliptical companion NGC 2444.Comment: 10 pages, 5 figures, 4 tables. Accepted for publication in MNRA
Unusual magnetic fields in the interacting spiral NGC 3627
By observing the interacting galaxy NGC 3627 in radio polarization we try to
answer the question to which degree the magnetic field follows the galactic gas
flows. We obtained total power and polarized intensity maps at 8.46 GHz and
4.85 GHz using the VLA in its compact D-configuration. In order to overcome the
zero-spacing problems, the interferometric data were combined with single-dish
measurements obtained with the Effelsberg 100-m radio telescope. The observed
magnetic field structure in NGC 3627 suggests that two field components are
superposed. One component smoothly fills the interarm space and shows up also
in the outermost disk regions, the other component follows a symmetric S-shaped
structure. In the western disk the latter component is well aligned with an
optical dust lane, following a bend which is possibly caused by external
interactions. However, in the SE disk the magnetic field crosses a heavy dust
lane segment, apparently being insensitive to strong density-wave effects. We
suggest that the magnetic field is decoupled from the gas by high turbulent
diffusion, in agreement with the large \ion{H}{i} line width in this region. We
discuss in detail the possible influence of compression effects and
non-axisymmetric gas flows on the general magnetic field asymmetries in NGC
3627. On the basis of the Faraday rotation distribution we also suggest the
existence of a large ionized halo around this galaxy.Comment: 11 pages, 11 figure
Discovery of a tidal dwarf galaxy in the Leo Triplet
We report discovery of a dwarf galaxy in the Leo Triplet. Analysis of the
neutral hydrogen distribution shows that it rotates independently of the tidal
tail of NGC 3628, with a radial velocity gradient of 35-40 km s over
approximately 13 kpc. The galaxy has a very high neutral gas content,
explaining large part of its total dynamic mass - suggesting small dark matter
content. As it is located at the tip of the gaseous tail, this strongly
suggests its tidal origin. Should it be the case, it would be one of the most
confident and closest (to the Milky Way) detections of a tidal dwarf galaxy
and, at the same time, a most detached from its parent galaxy (140
kpc) object of this type.Comment: 6 pages, 4 figures; The Astrophysical Journal, in pres
A search for extended radio emission from selected compact galaxy groups
Context. Studies on compact galaxy groups have led to the conclusion that a
plenitude of phenomena take place in between galaxies that form them. However,
radio data on these objects are extremely scarce and not much is known
concerning the existence and role of the magnetic field in intergalactic space.
Aims. We aim to study a small sample of galaxy groups that look promising as
possible sources of intergalactic magnetic fields; for example data from radio
surveys suggest that most of the radio emission is due to extended, diffuse
structures in and out of the galaxies. Methods. We used the Effelsberg 100 m
radio telescope at 4.85 GHz and NRAO VLA Sky Survey (NVSS) data at 1.40 GHz.
After subtraction of compact sources we analysed the maps searching for
diffuse, intergalactic radio emission. Spectral index and magnetic field
properties were derived. Results. Intergalactic magnetic fields exist in groups
HCG 15 and HCG 60, whereas there are no signs of them in HCG 68. There are also
hints of an intergalactic bridge in HCG 44 at 4.85 GHz. Conclusions.
Intergalactic magnetic fields exist in galaxy groups and their energy density
may be comparable to the thermal (X-ray) density, suggesting an important role
of the magnetic field in the intra-group medium, wherever it is detected.Comment: 13 pages, 4 figures, 3 tables, accepted for publication in A&
GangstaLife: Fusing Urban Ethnography with Netnography in Gang Studies
Recent research on street-involved populations has documented their online presence and has highlighted the effects of their online presentations on their lives in the real world. Given the increasing conflation between the online and offline world, contemporary urban ethnographers should pay increased attention to their participants’ online presence and interactions. However, methodological training of this sort is still in its infancy stages and has not yet evolved to guide the growing number of researchers undertaking this form of research. This article draws from our experiences using social media in our urban ethnographies with criminally involved groups, to examine the benefits, risks, and challenges of drawing on social media in urban ethnography. It is intended to serve as a foundational piece that will hopefully ignite scholarly dialogue, debate, and methodological training relating to deploying social media in urban—and specifically—gang ethnography
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