We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (
g
bar
) with the observed ...gravitational acceleration (
g
obs
), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in
g
obs
into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between
g
obs
and
g
bar
agrees well with the MG predictions. In addition, we find a difference of at least 6
σ
between the RARs of early- and late-type galaxies (split by Sérsic index and
u
−
r
colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (
M
gas
≈
M
⋆
) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.
Dynamical cluster masses from photometric surveys Contigiani, Omar; Hoekstra, Henk; Brouwer, Margot M ...
Monthly Notices of the Royal Astronomical Society,
01/2023, Letnik:
518, Številka:
2
Journal Article
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ABSTRACT
The masses of galaxy clusters can be measured using data obtained exclusively from wide photometric surveys in one of two ways: directly from the amplitude of the weak lensing signal or, ...indirectly, through the use of scaling relations calibrated using binned lensing measurements. In this paper, we build on a recently proposed idea and implement an alternative method based on the radial profile of the satellite distribution. This technique relies on splashback, a feature associated with the apocentre of recently accreted galaxies that offers a clear window into the phase-space structure of clusters without the use of velocity information. We carry out this dynamical measurement using the stacked satellite distribution around a sample of luminous red galaxies in the fourth data release of the Kilo-Degree Survey and validate our results using abundance-matching and lensing masses. To illustrate the power of this measurement, we combine dynamical and lensing mass estimates to robustly constrain scalar–tensor theories of gravity at cluster scales. Our results exclude departures from General Relativity of the order of unity. We conclude the paper by discussing the implications for future data sets. Because splashback mass measurements scale only with the survey volume, stage-IV photometric surveys are well-positioned to use splashback to provide high-redshift cluster masses.
ABSTRACT
We use KiDS weak lensing data to measure variations in mean halo mass as a function of several key galaxy properties (namely stellar colour, specific star formation rate, Sérsic index, and ...effective radius) for a volume-limited sample of GAMA galaxies in a narrow stellar mass range M* ∼ (2–5) × 1010 M⊙. This mass range is particularly interesting, inasmuch as it is where bimodalities in galaxy properties are most pronounced, and near to the break in both the galaxy stellar mass function and the stellar-to-halo mass relation (SHMR). In this narrow mass range, we find that both size and Sérsic index are better predictors of halo mass than either colour or SSFR, with the data showing a slight preference for Sérsic index. In other words, we find that mean halo mass is more tightly correlated with galaxy structure than either past star formation history or current star formation rate. Our results lead to an approximate lower bound on the dispersion in halo masses among log M* ≈ 10.5 galaxies: We find that the dispersion is ≳0.3 dex. This would imply either that offsets from the mean SHMR are closely coupled to size/structure or that the dispersion in the SHMR is larger than what past results have suggested. Our results thus provide new empirical constraints on the relationship between stellar and halo mass assembly at this particularly interesting mass range.
Abstract
Verlinde proposed that the observed excess gravity in galaxies and clusters is the consequence of emergent gravity (EG). In this theory, the standard gravitational laws are modified on ...galactic and larger scales due to the displacement of dark energy by baryonic matter. EG gives an estimate of the excess gravity (described as an apparent dark matter density) in terms of the baryonic mass distribution and the Hubble parameter. In this work, we present the first test of EG using weak gravitational lensing, within the regime of validity of the current model. Although there is no direct description of lensing and cosmology in EG yet, we can make a reasonable estimate of the expected lensing signal of low-redshift galaxies by assuming a background Lambda cold dark matter cosmology. We measure the (apparent) average surface mass density profiles of 33 613 isolated central galaxies and compare them to those predicted by EG based on the galaxies’ baryonic masses. To this end, we employ the ∼180 deg2 overlap of the Kilo-Degree Survey with the spectroscopic Galaxy And Mass Assembly survey. We find that the prediction from EG, despite requiring no free parameters, is in good agreement with the observed galaxy–galaxy lensing profiles in four different stellar mass bins. Although this performance is remarkable, this study is only a first step. Further advancements on both the theoretical framework and observational tests of EG are needed before it can be considered a fully developed and solidly tested theory.
Preterm infants requiring surgery are at risk of impaired neurocognitive development caused, possibly, by cerebral ischemia associated with impaired cerebrovascular autoregulation (CAR). We evaluated ...CAR before, during, and after laparotomy.
This was a hypothesis generating prospective observational cohort study.
We included preterm infants requiring surgery for necrotizing enterocolitis (NEC) or spontaneous intestinal perforation (SIP). Before, during, and after surgery we measured cerebral oxygen saturation using NIRS and calculated cerebral fractional tissue oxygen extraction (cFTOE).
Impaired CAR was defined if correlation coefficients (rho) between mean cFTOE and mean arterial blood pressure values were ≤−0.30 with P < .05. We used logistic regression analyses to determine factors associated with impaired CAR.
Nineteen infants with median (IQR) GA 27.6 weeks (26.6–31.0), birth weight 1090 g (924–1430), and postnatal age 9 days (7–12) were included. CAR was impaired more often during surgery than before (12 versus 3, P = .02) or after (12 versus 0, P < .01). A higher PCO2 level was associated with impaired CAR during surgery (OR 3.04, 95% CI, 1.11–8.12 for every 1 kPa increase).
More than half of preterm infants with NEC or SIP displayed evidence of impaired CAR during laparotomy. Further research should focus on mechanisms contributing to impaired CAR in preterm infants during surgery.
•Preterm infants who undergo major surgery are at a greater risk of impaired neurodevelopment than their peers.•Impaired cerebrovascular autoregulation during surgery might account for brain damage.•More than half of infants with NEC or SIP displayed evidence for impaired cerebrovascular autoregulation during laparotomy.
The Kilo-Degree Survey (KiDS) is a multi-band imaging survey designed for cosmological studies from weak lensing and photometric redshifts. It uses the European Southern Observatory VLT Survey ...Telescope with its wide-field camera OmegaCAM. KiDS images are taken in four filters similar to the Sloan Digital Sky Survey ugri bands. The best seeing time is reserved for deep r-band observations. The median 5σ limiting AB magnitude is 24.9 and the median seeing is below 0.7 arcsec. Initial KiDS observations have concentrated on the Galaxy and Mass Assembly (GAMA) regions near the celestial equator, where extensive, highly complete redshift catalogues are available. A total of 109 survey tiles, 1 square degree each, form the basis of the first set of lensing analyses of halo properties of GAMA galaxies. Nine galaxies per square arcminute enter the lensing analysis, for an effective inverse shear variance of 69 arcmin−2. Accounting for the shape measurement weight, the median redshift of the sources is 0.53. KiDS data processing follows two parallel tracks, one optimized for weak lensing measurement and one for accurate matched-aperture photometry (for photometric redshifts). This technical paper describes the lensing and photometric redshift measurements (including a detailed description of the Gaussian aperture and photometry pipeline), summarizes the data quality and presents extensive tests for systematic errors that might affect the lensing analyses. We also provide first demonstrations of the suitability of the data for cosmological measurements, and describe our blinding procedure for preventing confirmation bias in the scientific analyses. The KiDS catalogues presented in this paper are released to the community through http://kids.strw.leidenuniv.nl.
We use the first 100 deg2 of overlap between the Kilo-Degree Survey and the Galaxy And Mass Assembly survey to determine the average galaxy halo mass of ∼10 000 spectroscopically confirmed satellite ...galaxies in massive (M > 1013 h
−1 M⊙) galaxy groups. Separating the sample as a function of projected distance to the group centre, we jointly model the satellites and their host groups with Navarro–Frenk–White density profiles, fully accounting for the data covariance. The probed satellite galaxies in these groups have total masses log 〈M
sub/(h
−1 M⊙)〉 ≈ 11.7–12.2 consistent across group-centric distance within the errorbars. Given their typical stellar masses, log 〈M
⋆, sat/(h
−2 M⊙)〉 ∼ 10.5, such total masses imply stellar mass fractions of 〈M
⋆, sat〉/〈M
sub〉 ≈ 0.04 h
−1. The average subhalo hosting these satellite galaxies has a mass M
sub ∼ 0.015M
host independent of host halo mass, in broad agreement with the expectations of structure formation in a Λ cold dark matter universe.
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