32 research outputs found
Observations of cold extragalactic gas clouds at towards PKS 1610-771
We present results from MUSE observations of a 21-cm HI absorption system
detected with the Australian Square Kilometre Array Pathfinder radio telescope
at redshift towards the quasar PKS 1610-771. We
identify four galaxies (A, B, X and Y) at the same redshift as the 21-cm H I
Damped Lyman-{\alpha} (DLA) absorption system, with impact parameters ranging
from less than 10 kpc to almost 200 kpc from the quasar sightline. Ca II and Na
I absorption is seen in the MUSE spectrum of the background QSO, with
velocities coinciding with the initial HI 21-cm detection, but tracing less
dense and warmer gas. This metal-line component aligns with the rotating
ionised disc of galaxy B (impact parameter 18 kpc from the QSO) and appears to
be co-rotating with the galaxy disc. In contrast, the 21-cm HI absorber is
blueshifted relative to the galaxies nearest the absorber and has the opposite
sign to the velocity field of galaxy B. Since galaxies A and B are separated by
only 17 kpc on the sky and km s in velocity, it appears likely that
the 21-cm detection traces extragalactic clouds of gas formed from their
interaction. This system reveals that the cold 100 K neutral gas critical for
star formation can be associated with complex structures beyond the galaxy
disc, and is a first case study made in preparation for future large 21-cm
absorption surveys like the ASKAP First Large Absorption Survey in HI.Comment: Accepted. 13 pages, 7 figure
FAST discovery of a fast neutral hydrogen outflow
In this letter, we report the discovery of a fast neutral hydrogen outflow in
SDSS J145239.38+062738.0, a merging radio galaxy containing an optical type I
active galactic nuclei (AGN). This discovery was made through observations
conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST)
using redshifted 21-cm absorption. The outflow exhibits a blueshifted velocity
likely up to with respect to the systemic velocity
of the host galaxy with an absorption strength of corresponding to an optical depth of 0.002 at . The mass outflow rate ranges between and , implying an energy outflow rate ranging between
and , assuming 100 K
1000 K. Plausible drivers of the outflow include the star bursts,
the AGN radiation, and the radio jet, the last of which is considered the most
likely culprit according to the kinematics. By analysing the properties of the
outflow, the AGN, and the jet, we find that if the HI outflow is driven by the
AGN radiation, the AGN radiation seems not powerful enough to provide negative
feedback whereas the radio jet shows the potential to provide negative
feedback. Our observations contribute another example of a fast outflow
detected in neutral hydrogen, as well as demonstrate the capability of FAST in
detecting such outflows.Comment: Accepted by ApJ
Does a radio jet drive the massive multi-phase outflow in the ultra-luminous infrared galaxy IRAS 10565+2448?
We present new upgraded Giant Metrewave Radio Telescope (uGMRT) HI 21-cm
observations of the ultra-luminous infrared galaxy IRAS 10565+2448, previously
reported to show blueshifted, broad, and shallow HI absorption indicating an
outflow. Our higher spatial resolution observations have localised this
blueshifted outflow, which is 1.36 kpc southwest of the radio centre and
has a blueshifted velocity of and a full width at
half maximum (FWHM) of . The spatial extent and
kinematic properties of the HI outflow are consistent with the previously
detected cold molecular outflows in IRAS 10565+2448, suggesting that they
likely have the same driving mechanism and are tracing the same outflow. By
combining the multi-phase gas observations, we estimate a total outflowing mass
rate of at least and a total energy loss rate of
at least , where the contribution from the
ionised outflow is negligible, emphasising the importance of including both
cold neutral and molecular gas when quantifying the impact of outflows. We
present evidence of the presence of a radio jet and argue that this may play a
role in driving the observed outflows. The modest radio luminosity
of the jet in IRAS
10565+2448 implies that the jet contribution to driving outflows should not be
ignored in low radio luminosity AGN.Comment: 12 pages, 9 figures, accepted for publication in MNRA
The FLASH pilot survey: an HI absorption search against MRC 1-Jy radio sources
We report an ASKAP search for associated HI 21-cm absorption against bright
radio sources from the Molonglo Reference Catalogue (MRC) 1-Jy sample. The
search uses pilot survey data from the ASKAP First Large Absorption Survey in
\hi (FLASH) covering the redshift range . From a sample of 62
MRC 1-Jy radio galaxies and quasars in this redshift range we report three new
detections of associated HI 21-cm absorption, yielding an overall detection
fraction of . The detected systems comprise two radio
galaxies (MRC 2216281 at and MRC 0531237 at ) and one
quasar (MRC 2156245 at ). The MRC 0531237 absorption system is
the strongest found to date, with a velocity integrated optical depth of . All three objects with detected HI 21-cm
absorption are peaked-spectrum or compact steep-spectrum (CSS) radio sources,
classified based on our SED fits to the spectra. Two of them show strong
interplanetary scintillation at 162 MHz, implying that the radio continuum
source is smaller than 1 arcsec in size even at low frequencies. Among the
class of peaked-spectrum and compact steep-spectrum radio sources, the HI
detection fraction is . This is consistent within
with a detection fraction of in
earlier reported GPS and CSS samples at intermediate redshifts (). All three detections have a high 1.4 GHz radio luminosity, with MRC
0531237 and MRC 2216281 having the highest values in the sample, . The preponderance of extended radio sources in our sample
could partially explain the overall low detection fraction, while the effects
of a redshift evolution in gas properties and AGN UV luminosity on the neutral
gas absorption still need to be investigated.Comment: 28 pages, 9 figures and 7 Tables. Submitted to MNRA
The Gene Ontology knowledgebase in 2023
The Gene Ontology (GO) knowledgebase (http://geneontology.org) is a comprehensive resource concerning the functions of genes and gene products (proteins and noncoding RNAs). GO annotations cover genes from organisms across the tree of life as well as viruses, though most gene function knowledge currently derives from experiments carried out in a relatively small number of model organisms. Here, we provide an updated overview of the GO knowledgebase, as well as the efforts of the broad, international consortium of scientists that develops, maintains, and updates the GO knowledgebase. The GO knowledgebase consists of three components: (1) the GO-a computational knowledge structure describing the functional characteristics of genes; (2) GO annotations-evidence-supported statements asserting that a specific gene product has a particular functional characteristic; and (3) GO Causal Activity Models (GO-CAMs)-mechanistic models of molecular "pathways" (GO biological processes) created by linking multiple GO annotations using defined relations. Each of these components is continually expanded, revised, and updated in response to newly published discoveries and receives extensive QA checks, reviews, and user feedback. For each of these components, we provide a description of the current contents, recent developments to keep the knowledgebase up to date with new discoveries, and guidance on how users can best make use of the data that we provide. We conclude with future directions for the project
Trends of Runoff Variation and Effects of Main Causal Factors in Mun River, Thailand During 1980–2018
Mun River is the largest tributary of the Mekong River in Thailand and provides abundant water resources not only for an important agricultural area in Thailand but also for the lower Mekong River. To understand how the runoff of Mun River responds to climate change and human activities in recent decades, this study performed a detailed examination of the characteristics of runoff variation based on measurements at two hydrological gauging stations on the main stem of Mun River during 1980–2018. Using the Mann-Kendall test, Morlet wavelet transform and Double Cumulative Curve methods, this study identifies that the variation of annual runoff of Mun River encountered an abruption in 1999/2000, with an increased trend taking place since then. Furthermore, a detailed assessment of the effects of the variations in rainfall, temperature, evaporation, and land use types extracted from remote sensing images at the basin scale reveals that a significant reduction in forest area and slight reductions in evaporation and farmland area taking place since 1999 can lead to an increase in the runoff of Mun River, while the dramatic increase in garden area since 1999 tends to make the runoff decrease