Background The recently published INTERGROWTH-21st Project international population standard for newborn size is intended for global use, but its ability to identify small infants at risk of adverse ...outcomes in a general obstetric population has not been reported. Objective The objective of the study was to compare adverse neonatal outcomes among small-for-gestational-age (SGA) infants between the INTERGROWTH-21st standard and a customized birthweight standard (accounting for maternal characteristics of height, weight, parity, and ethnicity). We hypothesized that in a multiethnic general obstetric population in Auckland, New Zealand, a customized birthweight standard would better identify SGA infants at-risk of neonatal morbidity/mortality and stillbirth than the INTERGROWTH-21st standard. Study Design Using prospectively gathered maternity data from a general obstetric population in Auckland, New Zealand, from 2006 to 2013 (n = 53,484 births at ≥ 33 weeks), infants were classified as SGA (birthweight < 10th centile) by INTERGROWTH-21st and customized standards. Infants were further categorized as SGA by both criteria, INTERGROWTH-21st only, customized only, or not SGA (met neither criteria). Composite adverse neonatal outcome was defined as neonatal death, neonatal intensive care admission > 48 hours, or ventilation > 4 hours or 5-minute Apgar score < 7. Relative risks for primary outcomes were estimated using modified Poisson regression, with the non-SGA group as the referent. Results Incidence of SGA was 4.5% by INTERGROWTH-21st and 11.6% by customized standard. Compared with those not SGA, infants identified as small for gestational age by both criteria had the highest risk of adverse neonatal outcome (relative risk RR, 4.1, 95% confidence interval CI, 3.7–4.6) and stillbirth (RR, 8.3, 95% CI, 5.1–13.4). Infants SGA by customized standard only (n = 4015) had an increased risk of adverse neonatal outcome (RR, 2.0, 95% CI, 1.8–2.2) and stillbirth (RR, 3.0, 95% CI, 1.7–5.3). Few infants were identified as SGA by INTERGROWTH-21st only (n = 172), and risks of adverse neonatal outcome and stillbirth were not increased. Findings were unchanged when analyses were limited to term infants (n = 50,739). The INTERGROWTH-21st standard identified more Indian (12.8%) and Asian (5.8%) but fewer European (3.0%) and Pacific (2.9%) infants as SGA ( P < .01). Customized criteria identified more than 3 times as many SGA infants among Maori (14.5%), Pacific (13.5%), and European (11.2%) infants and twice as many among Asian (10.3%) infants (P<0.01) compared with INTERGROWTH-21st criteria. The majority of SGA infants by INTERGROWTH-21st only were born to Indian and Asian mothers (95.4%). Conclusions In our general obstetric population, birthweight customization identified more SGA infants at risk of perinatal mortality and morbidity compared with the INTERGROWTH-21st standard. The INTERGROWTH-21st standard failed to detect many at-risk SGA infants, particularly among ethnic groups with larger maternal size while disproportionately identifying higher rates of SGA among those with smaller maternal size. Local validation is needed prior to implementation of the INTERGROWTH-21st standard to avoid misclassification of infant birth size.
Abstract
Many radio galaxies show the presence of dense and dusty gas near the active nucleus. This can be traced by both 21 cm H i absorption and soft X-ray absorption, offering new insight into the ...physical nature of the circumnuclear medium of these distant galaxies. To better understand this relationship, we investigate soft X-ray absorption as an indicator for the detection of associated H i absorption, as part of preparation for the First Large Absorption Survey in H i to be undertaken with the Australian Square Kilometre Array Pathfinder (ASKAP). We present the results of our pilot study using the Boolardy Engineering Test Array, a precursor to ASKAP, to search for new absorption detections in radio sources brighter than 1 Jy that also feature soft X-ray absorption. Based on this pilot survey, we detected H i absorption towards the radio source PKS 1657−298 at a redshift of z = 0.42. This source also features the highest X-ray absorption ratio of our pilot sample by a factor of 3, which is consistent with our general findings that X-ray absorption predicates the presence of dense neutral gas. By comparing the X-ray properties of active galactic nuclei with and without detection of H i absorption at radio wavelengths, we find that X-ray hardness ratio and H i absorption optical depth are correlated at a statistical significance of 4.71σ. We conclude by considering the impact of these findings on future radio and X-ray absorption studies.
Abstract
We study the environments of low- and high-excitation radio galaxies (LERGs and HERGs, respectively) in the redshift range 0.01 < z < 0.4, using a sample of 399 radio galaxies and ...environmental measurements from the Galaxy And Mass Assembly (GAMA) survey. In our analysis we use the fifth nearest neighbour density (Σ5) and the GAMA galaxy groups catalogue (G3Cv6) and construct control samples of galaxies matched in stellar mass and colour to the radio-detected sample. We find that LERGs and HERGs exist in different environments and that this difference is dependent on radio luminosity. High-luminosity LERGs (L
NVSS ≳ 1024 W Hz−1) lie in much denser environments than a matched radio-quiet control sample (about three times as dense, as measured by Σ5), and are more likely to be members of galaxy groups (
$82^{+5}_{-7}$
per cent of LERGs are in GAMA groups, compared to
$58^{+3}_{-3}$
per cent of the control sample.). In contrast, the environments of the HERGs and lower luminosity LERGs are indistinguishable from that of a matched control sample. Our results imply that high-luminosity LERGs lie in more massive haloes than non-radio galaxies of similar stellar mass and colour, in agreement with earlier studies. When we control for the preference of LERGs to be found in groups, both high- and low-luminosity LERGs are found in higher-mass haloes (∼0.2 dex; at least 97 per cent significant) than the non-radio control sample.
The HIPASS catalogue – I. Data presentation Meyer, M. J.; Zwaan, M. A.; Webster, R. L. ...
Monthly notices of the Royal Astronomical Society,
June 2004, Letnik:
350, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The H i Parkes All-Sky Survey (HIPASS) catalogue forms the largest uniform catalogue of H i sources compiled to date, with 4315 sources identified purely by their H i content. The catalogue data ...comprise the southern region δ < + 2° of HIPASS, the first blind H i survey to cover the entire southern sky. The rms noise for this survey is 13 mJy beam −1 and the velocity range is −1280 to 12 700 km s −1. Data search, verification and parametrization methods are discussed along with a description of measured quantities. Full catalogue data are made available to the astronomical community including positions, velocities, velocity widths, integrated fluxes and peak flux densities. Also available are on-sky moment maps, position–velocity moment maps and spectra of catalogue sources. A number of local large-scale features are observed in the space distribution of sources, including the super-Galactic plane and the Local Void. Notably, large-scale structure is seen at low Galactic latitudes, a region normally obscured at optical wavelengths.
Abstract
The identification of active galactic nuclei (AGNs) in large surveys has been hampered by seemingly discordant classifications arising from differing diagnostic methods, usually tracing ...distinct processes specific to a particular wavelength regime. However, as shown in Yao et al., the combination of optical emission-line measurements and mid-infrared photometry can be used to optimize the discrimination capability between AGN and star formation activity. In this paper we test our new classification scheme by combining the existing GAMA-WISE data with high-quality MeerKAT radio continuum data covering 8 deg
2
of the GAMA G23 region. Using this sample of 1841 galaxies (
z
< 0.25), we investigate the total infrared (derived from 12
μ
m) to radio luminosity ratio,
q
(TIR)
, and its relationship to optical–infrared AGN and star-forming (SF) classifications. We find that while
q
(TIR)
is efficient at detecting AGN activity in massive galaxies generally appearing quiescent in the infrared, it becomes less reliable for cases where the emission from star formation in the host galaxy is dominant. However, we find that the
q
(TIR)
can identify up to 70% more AGNs not discernible at optical and/or infrared wavelengths. The median
q
(TIR)
of our SF sample is 2.57 ± 0.23, consistent with previous local universe estimates.
We present a source catalogue of 9040 radio sources resulting from high-resolution observations of 8385 Parkes-MIT-NRAO (PMN) sources with the Australia Telescope Compact Array. The catalogue lists ...flux density and structural measurements at 4.8 and 8.6GHz, derived from observations of all PMN sources in the declination range -87° < delta < -385 (exclusive of Galactic latitudes |b| < 2°) with flux density S4850≥ 70mJy (50mJy south of delta=-73°). We assess the quality of the data, which were gathered in 1992-1994, describe the population of catalogued sources and compare it to samples from complementary catalogues. In particular we find 127 radio sources with probable association with gamma-ray sources observed by the orbiting Fermi Large Area Telescope. PUBLICATION ABSTRACT
In the low-redshift Universe, the most powerful radio sources are often associated with gas-rich galaxy mergers or interactions. We here present evidence for an advanced, gas-rich (‘wet’) merger ...associated with a powerful radio galaxy at a redshift of z ∼ 2. This radio galaxy, MRC 0152-209, is the most infrared-luminous high-redshift radio galaxy known in the Southern hemisphere. Using the Australia Telescope Compact Array, we obtained high-resolution CO(1–0) data of cold molecular gas, which we complement with Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 (WFPC2) imaging and William Herschel Telescope long-slit spectroscopy. We find that, while roughly M
H2 ∼ 2 × 1010 M⊙ of molecular gas coincides with the central host galaxy, another M
H2 ∼ 3 × 1010 M⊙ is spread across a total extent of ∼60 kpc. Most of this widespread CO(1–0) appears to follow prominent tidal features visible in the rest-frame near-UV HST/WFPC2 imaging. Lyα emission shows an excess over He II, but a deficiency over L
IR, which is likely the result of photoionization by enhanced but very obscured star formation that was triggered by the merger. In terms of feedback, the radio source is aligned with widespread CO(1–0) emission, which suggests that there is a physical link between the propagating radio jets and the presence of cold molecular gas on scales of the galaxy's halo. Its optical appearance, combined with the transformational stage at which we witness the evolution of MRC 0152-209, leads us to adopt the name ‘Dragonfly Galaxy’.
We present a CO(1-0) survey for cold molecular gas in a representative sample of 13 high-z radio galaxies (HzRGs) at 1.4 < z < 2.8, using the Australia Telescope Compact Array. We detect CO(1-0) ...emission associated with five sources: MRC 0114-211, MRC 0152-209, MRC 0156-252, MRC 1138-262 and MRC 2048-272. The CO(1-0) luminosities are in the range
K km s−1 pc2. For MRC 0152-209 and MRC 1138-262, part of the CO(1-0) emission coincides with the radio galaxy, while part is spread on scales of tens of kpc and likely associated with galaxy mergers. The molecular gas mass derived for these two systems is M
H2 ∼ 6 × 1010 M (M
H2/
= 0.8). For the remaining three CO-detected sources, the CO(1-0) emission is located in the halo (∼50-kpc) environment. These three HzRGs are among the fainter far-IR emitters in our sample, suggesting that similar reservoirs of cold molecular halo gas may have been missed in earlier studies due to pre-selection of IR-bright sources. In all three cases, the CO(1-0) is aligned along the radio axis and found beyond the brightest radio hotspot, in a region devoid of 4.5 μm emission in Spitzer imaging. The CO(1-0) profiles are broad, with velocity widths of ∼1000-3600 km s−1. We discuss several possible scenarios to explain these halo reservoirs of CO(1-0). Following these results, we complement our CO(1-0) study with detections of extended CO from the literature and find at marginal statistical significance (95 per cent level) that CO in HzRGs is preferentially aligned towards the radio jet axis. For the eight sources in which we do not detect CO(1-0), we set realistic upper limits of
K km s−1 pc2. Our survey reveals a CO(1-0) detection rate of 38 per cent, allowing us to compare the CO(1-0) content of HzRGs with that of other types of high-z galaxies.
The high-redshift radio galaxy MRC 1138−262 ('Spiderweb Galaxy'; z = 2.16) is one of the most massive systems in the early Universe and surrounded by a dense 'web' of proto-cluster galaxies. Using ...the Australia Telescope Compact Array, we detected CO(1-0) emission from cold molecular gas - the raw ingredient for star formation - across the Spiderweb Galaxy. We infer a molecular gas mass of M
H2 = 6 × 1010 M (for M
H2/L′CO = 0.8). While the bulk of the molecular gas coincides with the central radio galaxy, there are indications that a substantial fraction of this gas is associated with satellite galaxies or spread across the intergalactic medium on scales of tens of kpc. In addition, we tentatively detect CO(1-0) in the star-forming proto-cluster galaxy HAE 229, 250 kpc to the West. Our observations are consistent with the fact that the Spiderweb Galaxy is building up its stellar mass through a massive burst of widespread star formation. At maximum star formation efficiency, the molecular gas will be able to sustain the current star formation rate (SFR 1400 M yr−1, as traced by Seymour et al.) for about 40 Myr. This is similar to the estimated typical lifetime of a major starburst event in infrared luminous merger systems.
Existing studies of the atomic hydrogen gas content in distant galaxies, through the absorption of the 21-cm line, often infer that the total column density,
, is anticorrelated with the linear ...extent of the background radio source, d
em. We investigate this interpretation, by dissecting the various parameters from which
is derived, and find that the relationship is driven primarily by the observed optical depth, τobs, which, for a given absorber size, is anticorrelated with d
em. Therefore, the inferred
anticorrelation is merely the consequence of geometry, in conjunction with the assumption of a common spin temperature/covering factor ratio for each member of the sample, an assumption for which there is scant observational justification. While geometry can explain the observed correlation, many radio sources comprise two radio lobes and so we model the projected area of a two-component emitter intercepted by a foreground absorber. From this, the observed τobs-d
em relationship is best reproduced through models which approximate either of the two Fanaroff & Riley classifications, although the observed scatter in the sample cannot be duplicated using a single deprojected radio source size. Furthermore, the trend is best reproduced using an absorber of diameter ∼ 100-1000 pc, which is also the range of values of d
em at which the 21-cm detection rate peaks. This may indicate that this is the characteristic linear size of the absorbing gas structure.
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