OSSOS. IX. Two Objects in Neptune's 9: 1 Resonance - Implications for Resonance Sticking in the Scattering Population

We discuss the detection in the Outer Solar System Origins Survey (OSSOS) of two objects in Neptune's distant 9:1 mean motion resonance at semimajor axis $a\approx~130$~au. Both objects are securely resonant on 10~Myr timescales, with one securely in the 9:1 resonance's leading asymmetric libration island and the other in either the symmetric or trailing asymmetric island. These objects are the largest semimajor axis objects with secure resonant classifications, and their detection in a carefully characterized survey allows for the first robust resonance population estimate beyond 100~au. The detection of these objects implies a 9:1 resonance population of $1.1\times10^4$ objects with $H_r<8.66$ ($D~\gtrsim~100$~km) on similar orbits (95\% confidence range of $\sim0.4-3\times10^4$). Integrations over 4~Gyr of an ensemble of clones spanning these objects' orbit fit uncertainties reveal that they both have median resonance occupation timescales of $\sim1$~Gyr. These timescales are consistent with the hypothesis that these objects originate in the scattering population but became transiently stuck to Neptune's 9:1 resonance within the last $\sim1$~Gyr of solar system evolution. Based on simulations of a model of the current scattering population, we estimate the expected resonance sticking population in the 9:1 resonance to be 1000-4500 objects with $H_r<8.66$; this is marginally consistent with the OSSOS 9:1 population estimate. We conclude that resonance sticking is a plausible explanation for the observed 9:1 population, but we also discuss the possibility of a primordial 9:1 population, which would have interesting implications for the Kuiper belt's dynamical history.Comment: accepted for publication in A

The redshift distribution and luminosity functions of galaxies in the Hubble Deep Field

Photometric redshifts have been determined for the galaxies in the Hubble Deep Field. The resulting redshift distribution shows two peaks: one at z ~ 0.6 and one at z ~ 2.2. Luminosity functions derived from the redshifts show strong luminosity evolution as a function of redshift. This evolution is consistent with the Babul and Rees scenario wherein massive galaxies form stars at high redshift while star formation in dwarf galaxies is delayed until after z = 1.Peer reviewed: YesNRC publication: N

OSSOS: The eccentricity and inclination distributions of the stable neptunian Trojans

International audienceThe minor planets on orbits that are dynamically stable in Neptune's 1:1 resonance on Gyr timescales were likely em:laced by Neptune's outward migration. We explore the intrinsic libration amplitude, eccentricity, and inclination distribution of Neptune's stable Trojans, using the detections and survey efficiency of the Outer Solar System Origins Survey (OSSOS) and Pan-STARRS1. We find that the libration amplitude of the stable Neptunian Trojan population can be well modeled as a Rayleigh distribution with a libration amplitude width σ A φ of 15 •. When taken as a whole, the Neptune Trojan population can be acceptably modeled with a Rayleigh eccentricity distribution of width σ e of 0.045 and a typical sin(i) × Gaussian inclination distribution with a width σ i of 14 ± 2 • ; however, these distributions are only marginally acceptable. This is likely because, even after accounting for survey detection biases, the known large (H r < 8) and small (H r ≥ 8) Neptune Trojans appear to have markedly different eccentricities and inclinations. We propose that like the classical Kuiper belt, the stable intrinsic Neptunian Trojan population have dynamically 'hot' and dynamically 'cold' components to its eccentricity/inclination distribution, with σ e−cold ∼ 0.02/σ i−cold ∼ 6 • and σ e−hot ∼ 0.05/σ i−hot ∼ 18 •. In this scenario, the 'cold' L4 Neptunian Trojan population lacks the H r ≥ 8.0 members and has 13 +11 −6 'cold' Trojans with H r < 8.0. On the other hand, the 'hot' L4 Neptunian Trojan population has 136 +84 −75 Trojans with H r < 10-a population 2.4 times greater than that of the L4 Jovian Trojans in the same luminosity range

OSSOS: XI. No active centaurs in the Outer Solar System Origins Survey

International audienceContext. Centaurs are icy objects in transition between the transneptunian region and the inner solar system, orbiting the Sun in the giant planet region. Some Centaurs display cometary activity, which cannot be sustained by the sublimation of water ice in this part of the solar system, and has been hypothesized to be due to the crystallization of amorphous water ice. Aims. In this work, we look at Centaurs discovered by the Outer Solar System Origins Survey (OSSOS) and search for cometary activity. Tentative detections would improve understanding of the origins of activity among these objects. Methods. We search for comae and structures by fitting and subtracting both Point Spread Functions (PSF) and Trailed point-Spread Functions (TSF) from the OSSOS images of each Centaur. When available, Col-OSSOS images were used to search for comae too. Results. No cometary activity is detected in the OSSOS sample. We track the recent orbital evolution of each new Centaur to confirm that none would actually be predicted to be active, and we provide size estimates for the objects. Conclusions. The addition of 20 OSSOS objects to the population of ∼250 known Centaurs is consistent with the currently understood scenario, in which drastic drops in perihelion distance induce changes in the thermal balance prone to trigger cometary activity in the giant planet region

Next Generation Virgo Cluster Survey. XXI. The weak lensing masses of the CFHTLS and NGVS RedGOLD galaxy clusters and calibration of the optical richness

International audienceWe measured stacked weak lensing cluster masses for a sample of 1323 galaxy clusters detected by the RedGOLD algorithm in the Canada–France–Hawaii Telescope Legacy Survey W1 and the Next Generation Virgo Cluster Survey at $0.2\lt z\lt 0.5$, in the optical richness range $10\lt \lambda \lt 70$. This is the most comprehensive lensing study of a $\sim 100 \%$ complete and $\sim 80 \%$ pure optical cluster catalog in this redshift range. We test different mass models, and our final model includes a basic halo model with a Navarro Frenk and White profile, as well as correction terms that take into account cluster miscentering, non-weak shear, the two-halo term, the contribution of the Brightest Cluster Galaxy, and an a posteriori correction for the intrinsic scatter in the mass–richness relation. With this model, we obtain a mass–richness relation of $\mathrm{log}{M}_{200}/{M}_{\odot }\,=(14.46\pm 0.02)+(1.04\pm 0.09)\mathrm{log}(\lambda /40)$ (statistical uncertainties). This result is consistent with other published lensing mass–richness relations. We give the coefficients of the scaling relations between the lensing mass and X-ray mass proxies, L (X) and T (X), and compare them with previous results. When compared to X-ray masses and mass proxies, our results are in agreement with most previous results and simulations, and consistent with the expected deviations from self-similarity

Col-OSSOS Color and Inclination Are Correlated throughout the Kuiper Belt

Both physical and dynamical properties must be considered to constrain the origins of the dynamically excited distant solar system populations. We present high-precision (g-r) colors for 25 small (H-r > 5) dynamically excited trans-Neptunian objects (TNOs) and centaurs acquired as part of the Colours of the Outer Solar System Origins Survey. We combine our data set with previously published measurements and consider a set of 229 colors of outer solar system objects on dynamically excited orbits. The overall color distribution is bimodal and can be decomposed into two distinct classes, termed gray and red, that each has a normal color distribution. The two color classes have different inclination distributions: red objects have lower inclinations than the gray ones. This trend holds for all dynamically excited TNO populations. Even in the worst-case scenario, biases in the discovery surveys cannot account for this trend; it is intrinsic to the TNO population. Considering that TNOs are the precursors of centaurs, and that their inclinations are roughly preserved as they become centaurs, our finding solves the conundrum of centaurs being the only outer solar system population identified so far to exhibit this property. The different orbital distributions of the gray and red dynamically excited TNOs provide strong evidence that their colors are due to different formation locations in a disk of planetesimals with a compositional gradient.Col-OSSOS program; CanadianSpace Agency; UK STFC [ST/L000709/1]; Gemini Observatory; NASA [NNX14AG93G, NNX15AH59G]; Portuguese FCT-Foundation for Science and Technology [SFRH/BGCT/113686/2015]; FCT-Foundation for Science and Technology [UID/Multi/00611/2013]; FEDER-European Regional Development Fund through COMPETE 2020-Operational Programme Competitiveness and Internationalisation [POCI-01-0145-FEDER-006922]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The Next Generation Virgo Cluster Survey (NGVS). XXVII. The Size and Structure of Globular Cluster Systems and Their Connection to Dark Matter Halos

International audienceWe study the size and structure of globular cluster (GC) systems of 118 early-type galaxies from the NGVS, MATLAS, and ACSVCS surveys. Fitting Sérsic profiles, we investigate the relationship between effective radii of GC systems (R$_{e,gc}$) and galaxy properties. GC systems are 2–4 times more extended than host galaxies across the entire stellar mass range of our sample (10$^{8.3}$M$_{⊙}$ < M$_{*}$ < 10$^{11.6}$M$_{⊙}$). The relationship between R$_{e,gc}$ and galaxy stellar mass exhibits a characteristic “knee” at a stellar mass of M$_{p}$ ≃ 10$^{10.8}$, similar to the galaxy R$_{e}$–stellar mass relationship. We present a new characterization of the traditional blue and red GC color subpopulations, describing them with respect to host galaxy color (Δ$_{gi}$): GCs with similar colors to their hosts have a “red” Δ$_{gi}$, and those significantly bluer GCs have a “blue” Δ$_{gi}$. The GC populations with red Δ$_{gi}$, even in dwarf galaxies, are twice as extended as the stars, suggesting that formation or survival mechanisms favor the outer regions. We find a tight correlation between R$_{e,gc}$ and the total number of GCs, with intrinsic scatter ≲0.1 dex spanning two and three orders of magnitude in size and number, respectively. This holds for both red and blue subpopulations, albeit with different slopes. Assuming that N$_{GC,Total}$ correlates with M$_{200}$, we find that the red GC systems have effective radii of roughly 1%–5% R$_{200}$, while the blue GC systems in massive galaxies can have sizes as large as ∼10% R$_{200}$. Environmental dependence on R$_{e,gc}$ is also found, with lower-density environments exhibiting more extended GC systems at fixed mass