13 research outputs found
Are we seeing accretion flows in a 250kpc-sized Ly-alpha halo at z=3?
Using MUSE on the ESO-VLT, we obtained a 4 hour exposure of the z=3.12 radio
galaxy MRC0316-257. We detect features down to ~10^-19 erg/s/cm^2/arcsec^2 with
the highest surface brightness regions reaching more than a factor of 100
higher. We find Ly-alpha emission out to ~250 kpc in projection from the active
galactic nucleus (AGN). The emission shows arc-like morphologies arising at
150-250 kpc from the nucleus in projection with the connected filamentary
structures reaching down into the circum-nuclear region. The most distant arc
is offset by 700 km/s relative to circum-nuclear HeII 1640 emission, which we
assume to be at the systemic velocity. As we probe emission closer to the
nucleus, the filamentary emission narrows in projection on the sky, the
relative velocity decreases to ~250 km/s, and line full-width at half maximum
range from 300-700 km/s. From UV line ratios, the emission on scales of 10s of
kpc from the nucleus along a wide angle in the direction of the radio jets is
clearly excited by the radio jets and ionizing radiation of the AGN. Assuming
ionization equilibrium, the more extended emission outside of the axis of the
jet direction would require 100% or more illumination to explain the observed
surface brightness. High speed (>300 km/s) shocks into rare gas would provide
sufficiently high surface brightness. We discuss the possibility that the arcs
of Ly-alpha emission represent accretion shocks and the filamentary emission
represent gas flows into the halo, and compare our results with gas accretion
simulations.Comment: 4 pages, 2 figures, 1 table, A&A letters accepte
The relation between galaxy density and radio jet power for 1.4 GHz VLA selected AGNs in Stripe 82
Using a Karl G. Jansky Very Large Array (VLA) L-band (1-2 GHz) survey covering âŒ100âdeg2 of the Stripe 82 field, we have obtained a catalogue of 2716 radio AGNs. For these AGNs, we investigate the impact of galaxy density on 1.4 GHz radio luminosity (L1.4). We determine their close environment densities using the surface density parameter, ÎŁN, for N = 2 and N = 5, which we bin by redshift to obtain a pseudo-3D galaxy density measure. Matching the radio AGNs to sources without radio detections in terms of redshift, K-band magnitude and (g â K) colour index, we obtain samples of control galaxies and determine whether radio AGN environments differ from this general population
Faint [CI](1-0) emission in z 3.5 radio galaxies
We present Atacama Large Millimeter/sub-millimeter Array (ALMA) neutral
carbon, [C I](1-0), line observations that probe molecular hydrogen gas (H)
within seven radio galaxies at surrounded by extended
( kpc) Ly- nebulae. We extract [C I](1-0) emission from the
radio-active galactic nuclei (AGN) host galaxies whose positions are set by
near-infrared detections and radio detections of the cores. Additionally, we
place constraints on the galaxies' systemic redshifts via He II 1640
lines seen with the Multi-Unit Spectroscopic Explorer (MUSE). We detect faint
[C I] emission in four out of seven sources. In two of these galaxies, we
discover narrow line emission of full width at half maximum km
s which may trace emission from bright kpc-scale gas clouds within the
ISM. In the other two [C I]-detected galaxies, line dispersions range from
km s and may be tracing the rotational component of the
cold gas. Overall, the [C I] line luminosities correspond to H masses of
M for the detections
and M for the [C I] non-detections
in three out of seven galaxies within the sample. The molecular gas masses in
our sample are relatively low in comparison to previously reported measures for
similar galaxies which are M Our
results imply that the observed faintness in carbon emission is representative
of a decline in molecular gas supply from previous star-formation epochs and/or
a displacement of molecular gas from the ISM due to jet-powered outflows.Comment: 16 pages, 4 figures and 5 tables. Accepted for publication in MNRA
MIGHTEE: deep 1.4 GHz Source Counts and the Sky Temperature Contribution of Star Forming Galaxies and Active Galactic Nuclei
MIGHTEE: Deep 1.4 GHz Source Counts and the Sky Temperature Contribution of Star Forming Galaxies and Active Galactic Nuclei
We present deep 1.4 GHz source counts from 5 deg of the continuum
Early Science data release of the MeerKAT International Gigahertz Tiered
Extragalactic Exploration (MIGHTEE) survey down to 15
Jy. Using observations over two extragalactic fields (COSMOS and XMM-LSS),
we provide a comprehensive investigation into correcting the incompleteness of
the raw source counts within the survey to understand the true underlying
source count population. We use a variety of simulations that account for:
errors in source detection and characterisation, clustering, and variations in
the assumed source model used to simulate sources within the field and
characterise source count incompleteness. We present these deep source count
distributions and use them to investigate the contribution of extragalactic
sources to the sky background temperature at 1.4 GHz using a relatively large
sky area. We then use the wealth of ancillary data covering{a subset of the
COSMOS field to investigate the specific contributions from both active
galactic nuclei (AGN) and star forming galaxies (SFGs) to the source counts and
sky background temperature. We find, similar to previous deep studies, that we
are unable to reconcile the sky temperature observed by the ARCADE 2
experiment. We show that AGN provide the majority contribution to the sky
temperature contribution from radio sources, but the relative contribution of
SFGs rises sharply below 1 mJy, reaching an approximate 15-25% contribution to
the total sky background temperature (100 mK) at 15 Jy.Comment: 24 pages, 12 figures; Accepted for publication in MNRA
MIGHTEE: multi-wavelength counterparts in the COSMOS field
In this paper we combine the Early Science radio continuum data from the
MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey,
with optical and near-infrared data and release the cross-matched catalogues.
The radio data used in this work covers deg of the COSMOS field,
reaches a thermal noise of Jy/beam and contains radio
components. We visually inspect and cross-match the radio sample with optical
and near-infrared data from the Hyper Suprime-Cam (HSC) and UltraVISTA surveys.
This allows the properties of active galactic nuclei and star-forming
populations of galaxies to be probed out to . Additionally, we use
the likelihood ratio method to automatically cross-match the radio and optical
catalogues and compare this to the visually cross-matched catalogue. We find
that 94 per cent of our radio source catalogue can be matched with this method,
with a reliability of per cent. We proceed to show that visual
classification will still remain an essential process for the cross-matching of
complex and extended radio sources. In the near future, the MIGHTEE survey will
be expanded in area to cover a total of 20~deg; thus the combination
of automated and visual identification will be critical. We compare redshift
distribution of SFG and AGN to the SKADS and T-RECS simulations and find more
AGN than predicted at .Comment: 15 pages, 15 figures. Accepted for publication in MNRA
MUSE unravels the ionisation and origin of metal-enriched absorbers in the gas halo of a z = 2.92 radio galaxy
We have used the Multi-Unit Spectroscopic Explorer (MUSE) to study the circumgalactic medium (CGM) of a z = 2.92 radio galaxy, MRC 0943â242 by parametrising its emitting and absorbing gas. In both Lyα λ1216 and He ii λ1640 lines, we observe emission with velocity shifts of âv ' â1000 km sâ1 from the systemic redshift of the galaxy. These blueshifted components represent kinematically perturbed gas that is aligned with the radio axis, and is therefore a signature of jet-driven outflows. Three of the four known Lyα absorbers in this source are detected at the same velocities as C iv λλ1548, 1551 and N v λλ1239, 1243 absorbers, proving that the gas is metal-enriched more so than previously thought. At the velocity of a strong Lyα absorber which has an H i column of NH i/cmâ2 = 1019.2 and velocity shift of âv ' â400 km sâ1 , we also detect Si ii λ1260 and Si ii λ1527 absorption, which suggests that the absorbing gas is ionisation bounded. With the added sensitivity of this MUSE observation, we are more capable of adding constraints to absorber column densities and consequently determining what powers their ionisation. To do this, we obtain photoionisation grid models in cloudy which show that AGN radiation is capable of ionising the gas and producing the observed column densities in a gas of metallicity of Z/Z ' 0.01 with a nitrogen abundance a factor of 10 greater than that of hydrogen. This metal-enriched absorbing gas, which is also spatially extended over a projected distance of r & 60 kpc, is likely to have undergone chemical enrichment through stellar winds that have swept up metals from the interstellar-medium and deposited them in the outer regions of the galaxyâs halo
MIGHTEE: deep 1.4Â GHz source counts and the sky temperature contribution of star forming galaxies and active galactic nuclei
We present deep 1.4 GHz source counts from âŒ5 deg2 of the continuum Early Science data release of the MeerKAT International Gigahertz Tiered Extragalactic Exploration (MIGHTEE) survey down to S1.4GHz âŒ15 ÎŒJy. Using observations over two extragalactic fields (COSMOS and XMM-LSS), we provide a comprehensive investigation into correcting the incompleteness of the raw source counts within the survey to understand the true underlying source count population. We use a variety of simulations that account for: errors in source detection and characterisation, clustering, and variations in the assumed source model used to simulate sources within the field and characterise source count incompleteness. We present these deep source count distributions and use them to investigate the contribution of extragalactic sources to the sky background temperature at 1.4 GHz using a relatively large sky area. We then use the wealth of ancillary data covering a subset of the COSMOS field to investigate the specific contributions from both active galactic nuclei (AGN) and star forming galaxies (SFGs) to the source counts and sky background temperature. We find, similar to previous deep studies, that we are unable to reconcile the sky temperature observed by the ARCADE 2 experiment. We show that AGN provide the majority contribution to the sky temperature contribution from radio sources, but the relative contribution of SFGs rises sharply below 1 mJy, reaching an approximate 15-25 per cent contribution to the total sky background temperature (Tb âŒ100 mK) at âŒ15 ÎŒJy
MIGHTEE: deep 1.4Â GHz source counts and the sky temperature contribution of star-forming galaxies and active galactic nuclei
We present deep 1.4 GHz source counts from âŒ5 deg2 of the continuum Early Science data release of the MeerKAT International Gigahertz Tiered Extragalactic Exploration survey down to S1.4GHz âŒ15 ÎŒ Jy. Using observations over two extragalactic fields (COSMOS and XMM-LSS), we provide a comprehensive investigation into correcting the incompleteness of the raw source counts within the survey to understand the true underlying source count population. We use a variety of simulations that account for: errors in source detection and characterization, clustering, and variations in the assumed source model used to simulate sources within the field and characterize source count incompleteness. We present these deep source count distributions and use them to investigate the contribution of extragalactic sources to the sky background temperature at 1.4 GHz using a relatively large sky area. We then use the wealth of ancillary data covering a subset of the COSMOS field to investigate the specific contributions from both active galactic nuclei (AGN) and star-forming galaxies (SFGs) to the source counts and sky background temperature. We find, similar to previous deep studies, that we are unable to reconcile the sky temperature observed by the ARCADE 2 experiment. We show that AGN provide the majority contribution to the sky temperature contribution from radio sources, but the relative contribution of SFGs rises sharply below 1 mJy, reaching an approximate 15â25 per cent contribution to the total sky background temperature (Tb âŒ100 mK) at âŒ15 ÎŒ Jy
MIGHTEE: multi-wavelength counterparts in the COSMOS field
In this paper we combine the Early Science radio continuum data from the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey, with optical and near-infrared data and release the cross-matched catalogues. The radio data used in this work covers 0.86 deg2 of the COSMOS field, reaches a thermal noise of 1.7 ÎŒJy/beam and contains 6102 radio components. We visually inspect and cross-match the radio sample with optical and near-infrared data from the Hyper Suprime-Cam (HSC) and UltraVISTA surveys. This allows the properties of active galactic nuclei and star-forming populations of galaxies to be probed out to zâ5. Additionally, we use the likelihood ratio method to automatically cross-match the radio and optical catalogues and compare this to the visually cross-matched catalogue. We find that 94 per cent of our radio source catalogue can be matched with this method, with a reliability of 95 per cent. We proceed to show that visual classification will still remain an essential process for the cross-matching of complex and extended radio sources. In the near future, the MIGHTEE survey will be expanded in area to cover a total of âŒ20~deg2; thus the combination of automated and visual identification will be critical. We compare redshift distribution of SFG and AGN to the SKADS and T-RECS simulations and find more AGN than predicted at zâŒ1