35 research outputs found
Splashing of liquids: interplay of surface roughness with surrounding gas
We investigate the interplay between substrate roughness and surrounding gas
pressure in controlling the dynamics of splashing when a liquid drop hits a dry
solid surface. We associate two distinct forms of splashing with each of these
control parameters: prompt splashing is due to surface roughness and corona
splashing is due to instabilities produced by the surrounding gas. The size
distribution of ejected droplets reveals the length scales of the underlying
droplet-creation process in both cases.Comment: 6 pages, 6 figure
Sub-arcsecond imaging of Arp\,299-A at 150 MHz with LOFAR: Evidence for a starburst-driven outflow
We report on the first sub-arcsecond (0.44 0.41 arcsec)
angular resolution image at 150 MHz of the A-nucleus in the Luminous Infrared
Galaxy Arp299, from International Low Frequency Array (LOFAR) Telescope
observations. The most remarkable finding is that of an intriguing two-sided,
filamentary structure emanating from A-nucleus, which we interpret as an
outflow that extends up to at least 14 arcseconds from the A-nucleus in the N-S
direction ( 5 kpc deprojected size) and accounts for almost 40% of the
extended emission of the entire galaxy system. We also discuss HST/NICMOS
[FeII] 1.64 and H 2.12 images of Arp299-A,
which show similar features to those unveiled by our 150 MHz LOFAR
observations, thus giving string morphological support for the outflow
scenario. Finally, we discuss unpublished NaI D spectra that confirm the
outflow nature of this structure. From energetic arguments, we rule out the
low-luminosity active galactic nucleus in Arp299-A as a driver for the
outflow. On the contrary, the powerful, compact starburst in the central
regions of Arp299-A provides plenty of mechanical energy to sustain an
outflow, and we conclude that the intense supernova (SN) activity in the
nuclear region of Arp299-A is driving the observed outflow. We estimate that
the starburst wind can support a mass-outflow rate in the range (11-63) at speeds of up to (370 - 890) , and is
relatively young, with an estimated kinematic age of (3 - 7) Myr. Those results
open an avenue to the use of low-frequency (150 MHz), sub-arcsecond imaging
with LOFAR to detect outflows in the central regions of local luminous infrared
galaxies
ALMA High-frequency Long Baseline Campaign in 2017:Band-to-band Phase Referencing in Submillimeter Waves
In 2017, an Atacama Large Millimeter/submillimeter Array (ALMA)
high-frequency long baseline campaign was organized to test image capabilities
with baselines up to 16 km at submillimeter (submm) wavelengths. We
investigated image qualities using ALMA receiver Bands 7, 8, 9, and 10 (285-875
GHz) by adopting band-to-band (B2B) phase referencing in which a phase
calibrator is tracked at a lower frequency. For B2B phase referencing, it is
expected that a closer phase calibrator to a target can be used, comparing to
standard in-band phase referencing. In the first step, it is ensured that an
instrumental phase offset difference between low- and high-frequency Bands can
be removed using a differential gain calibration in which a phase calibrator is
certainly detected while frequency switching. In the next step, comparative
experiments are arranged to investigate the image quality between B2B and
in-band phase referencing with phase calibrators at various separation angles.
In the final step, we conducted long baseline imaging tests for a quasar at 289
GHz in Band 7 and 405 GHz in Band 8 and complex structure sources of HL Tau and
VY CMa at ~670 GHz in Band 9. The B2B phase referencing was successfully
applied, allowing us to achieve an angular resolution of 14x11 and 10x8 mas for
HL Tau and VY CMa, respectively. There is a high probability of finding a
low-frequency calibrator within 5.4 deg in B2B phase referencing, bright enough
to use an 8 s scan length combined with a 7.5 GHz bandwidth.Comment: 61 pages, 17 figures, 8 table
The PARADIGM project I: a multiscale radio morphological analysis of local U/LIRGS
Disentangling the radio flux contribution from star formation (SF) and active-galactic-nuclei (AGNs) activity is a long-standing problem in extragalactic astronomy, since at frequencies of âČ 10 GHz, both processes emit synchrotron radiation. We present in this work the general objectives of the PARADIGM (PAnchromatic high-Resolution Analysis of DIstant Galaxy Mergers) project, a multi-instrument concept to explore SF and mass assembly of galaxies. We introduce two novel general approaches for a detailed multiscale study of the radio emission in local (ultra) luminous infrared galaxies (U/LIRGs). In this work, we use archival interferometric data from the Very Large Array (VLA) centred at ⌠6 GHz (C band) and present new observations from the e-Multi-Element Radio-Linked Interferometer Network (e-MERLIN) for UGCâ5101, VVâ705, VVâ250, and UGCâ8696. Using our image decomposition methods, we robustly disentangle the radio emission into distinct components by combining information from the two interferometric arrays. We use e-MERLIN as a probe of the core-compact radio emission (AGN or starburst) at ⌠20 pc scales, and as a probe of nuclear diffuse emission, at scales âŒ100â200 pc. With VLA, we characterize the source morphology and the flux density on scales from âŒ200 pc up to and above 1 kpc. As a result, we find deconvolved and convolved sizes for nuclear regions from âŒ10 to âŒ200 pc. At larger scales, we find sizes of 1.5â2 kpc for diffuse structures (with effective sizes of ⌠300â400 pc). We demonstrate that the radio emission from nuclear extended structures (⌠100 pc) can dominate over core-compact components, providing a significant fraction of the total multiscale SF output. We establish a multiscale radio tracer for SF by combining information from different instruments. Consequently, this work sets a starting point to potentially correct for overestimations of AGN fractions and underestimates of SF activity
ALMA Imaging of the CO(6-5) Line Emission in NGC 7130
In this paper, we report our high-resolution (0".20 Ă 0".14 or ~70 Ă 49 pc) observations of the CO(6-5) line emission, which probes warm and dense molecular gas, and the 434 ÎŒm dust continuum in the nuclear region of NGC 7130, obtained with the Atacama Large Millimeter Array (ALMA). The CO line and dust continuum fluxes detected in our ALMA observations are 1230 ± 74 Jy km s^(â1) and 814 ± 52 mJy, respectively, which account for 100% and 51% of their total fluxes. We find that the CO(6-5) and dust emissions are generally spatially correlated, but their brightest peaks show an offset of ~70 pc, suggesting that the gas and dust emissions may start decoupling at this physical scale. The brightest peak of the CO(6-5) emission does not spatially correspond to the radio continuum peak, which is likely dominated by an active galactic nucleus (AGN). This, together with our additional quantitative analysis, suggests that the heating contribution of the AGN to the CO(6-5) emission in NGC 7130 is negligible. The CO(6-5) and the extinction-corrected Pa-α maps display striking differences, suggestive of either a breakdown of the correlation between warm dense gas and star formation at linear scales of <100 pc or a large uncertainty in our extinction correction to the observed Pa-α image. Over a larger scale of ~2.1 kpc, the double-lobed structure found in the CO(6-5) emission agrees well with the dust lanes in the optical/near-infrared images
Molecular Gas in the NGC 6240 Merging Galaxy System at the Highest Spatial Resolution
We present the highest-resolutionâ15 pc (0.â03)âALMA ÂčÂČCO(2â1) line emission and 1.3 mm continuum maps, tracers of the molecular gas and dust, respectively, in the nearby merging galaxy system NGC 6240, which hosts two supermassive black holes growing simultaneously. These observations provide an excellent spatial match to existing Hubble Space Telescope (HST) optical and near-infrared observations of this system. A significant molecular gas mass, ~9 Ă 10âč Mâ, is located between the two nuclei, forming a clumpy stream kinematically dominated by turbulence, rather than a smooth rotating disk, as previously assumed from lower-resolution data. Evidence for rotation is seen in the gas surrounding the southern nucleus but not in the northern one. Dynamical shells can be seen, likely associated with nuclear supernova remnants. We further detect the presence of significant high-velocity outflows, some of them reaching velocities >500 km sâ»Âč, affecting a significant fraction, ~11%, of the molecular gas in the nuclear region. Inside the spheres of influence of the northern and southern supermassive black holes, we find molecular masses of 7.4 Ă 10âž and 3.3 Ă 10âč Mâ, respectively. We are thus directly imaging the reservoir of gas that can accrete onto each supermassive black hole. These new ALMA maps highlight the critical need for high-resolution observations of molecular gas in order to understand the feeding of supermassive black holes and its connection to galaxy evolution in the context of a major galaxy merger