Did Galaxy Assembly and Supermassive Black-Hole Growth go hand-in-hand?

In this paper, we address whether the growth of supermassive black-holes has kept pace with the process of galaxy assembly. For this purpose, we first searched the Hubble Ultra Deep Field (HUDF) for "tadpole galaxies", which have a knot at one end and an extended tail. They appear dynamically unrelaxed -- presumably early-stage mergers -- and make up ~6% of the field galaxy population. Their redshift distribution follows that of field galaxies, indicating that -- if tadpole galaxies are indeed dynamically young -- the process of galaxy assembly generally kept up with the reservoir of field galaxies as a function of epoch. Next, we present a search for HUDF objects with point-source components that are optically variable (at the >~3.0 sigma level) on timescales of weeks--months. Among 4644 objects to i_AB=28.0 mag (10 sigma), 45 have variable point-like components, which are likely weak AGN. About 1% of all field objects show variability for 0.1 < z < 4.5, and their redshift distribution is similar to that of field galaxies. Hence supermassive black-hole growth in weak AGN likely also kept up with the process of galaxy assembly. However, the faint AGN sample has almost no overlap with the tadpole sample, which was predicted by recent hydrodynamical numerical simulations. This suggests that tadpole galaxies are early-stage mergers, which likely preceded the ``turn-on'' of the AGN component and the onset of visible point-source variability by >~1 Gyr.Comment: 9 pages, Latex2e requires 'elsart' and 'elsart3' (included), 10 postscript figures. To appear in the Proceedings of the Leiden Workshop on "QSO Host Galaxies: Evolution and Environment", eds. P.D. Barthel & D.B. Sanders (New Astron. Rev., 2006

Cold gas in elliptical galaxies

We explore the evolution of the cold gas (molecular and neutral hydrogen) of elliptical galaxies and merger remnants ordered into a time sequence on the basis of spectroscopic age estimates. We find that the fraction of cold gas in early merger remnants decreases significantly for ~1-2 Gyr, but subsequent evolution toward evolved elliptical systems sees very little change. This trend can be attributed to an initial gas depletion by strong star-formation which subsequently declines to quiescent rates. This explanation is consistent with the merger picture for the formation of elliptical galaxies. We also explore the relation between HI-to-H2 mass ratio and spectroscopic galaxy age, but find no evidence for a statistically significant trend. This suggests little net HI to H2 conversion for the systems in the present sample.Comment: 11 pages, 6 figures, accepted for publication by MNRA

Building operational research capacity in the Pacific

Operational research (OR) in public health aims to investigate strategies, interventions, tools or knowledge that can enhance the quality, coverage, effectiveness or performance of health systems. Attention has recently been drawn to the lack of OR capacity in public health programmes throughout the Pacific Islands, despite considerable investment in implementation. This lack of ongoing and critical reflection may prevent health programme staff from understanding why programme objectives are not being fully achieved, and hinder long-term gains in public health. The International Union Against Tuberculosis and Lung Disease (The Union) has been collaborating with Pacific agencies to conduct OR courses based on the training model developed by The Union and Médecins Sans Frontières Brussels-Luxembourg in 2009. The first of these commenced in 2011 in collaboration with the Fiji National University, the Fiji Ministry of Health, the World Health Organization and other partners. The Union and the Secretariat of the Pacific Community organised a second course for participants from other Pacific Island countries and territories in 2012, and an additional course for Fijian participants commenced in 2013. Twelve participants enrolled in each of the three courses. Of the two courses completed by end 2013, 18 of 24 participants completed their OR and submitted papers by the course deadline, and 17 papers have been published to date. This article describes the context, process and outputs of the Pacific courses, as well as innovations, adaptations and challenges

Generation of in situ sequencing based OncoMaps to spatially resolve gene expression profiles of diagnostic and prognostic markers in breast cancer

Background: Gene expression analysis of breast cancer largely relies on homogenized tissue samples. Due to the high degree of cellular and molecular heterogeneity of tumor tissues, bulk tissue-based analytical approaches can only provide very limited system-level information about different signaling mechanisms and cellular interactions within the complex tissue context. Methods: We describe an analytical approach using in situ sequencing (ISS), enabling highly multiplexed, spatially and morphologically resolved gene expression profiling. Ninety-one genes including prognostic and predictive marker profiles, as well as genes involved in specific cellular pathways were mapped within whole breast cancer tissue sections, covering luminal A/B-like, HER2-positive and triple negative tumors. Finally, all these features were combined and assembled into a molecular-morphological OncoMap for each tumor tissue. Findings: Our in situ approach spatially revealed intratumoral heterogeneity with regard to tumor subtype as well as to the OncotypeDX recurrence score and even uncovered areas of minor cellular subpopulations. Since ISS-resolved molecular profiles are linked to their histological context, a deeper analysis of the core and periphery of tumor foci enabled identification of specific gene expression patterns associated with these morphologically relevant regions. Interpretation: ISS generated OncoMaps represent useful tools to extend our general understanding of the biological processes behind tumor progression and can further support the identification of novel therapeutical targets as well as refine tumor diagnostics. Fund: Swedish Cancerfonden, UCAN, Vetenskapsrådet, Cancer Genomics Netherlands, Iris, Stig och Gerry Castenbäcks Stiftelse, BRECT, PCM Program, King Gustaf V Jubilee Fund, BRO, KI and Stockholm County Council, Alice Wallenberg Foundation

Towards a unified theory of Sobolev inequalities

We discuss our work on pointwise inequalities for the gradient which are connected with the isoperimetric profile associated to a given geometry. We show how they can be used to unify certain aspects of the theory of Sobolev inequalities. In particular, we discuss our recent papers on fractional order inequalities, Coulhon type inequalities, transference and dimensionless inequalities and our forthcoming work on sharp higher order Sobolev inequalities that can be obtained by iteration.Comment: 39 pages, made some changes to section 1

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Young and Intermediate-age Distance Indicators

Distance measurements beyond geometrical and semi-geometrical methods, rely mainly on standard candles. As the name suggests, these objects have known luminosities by virtue of their intrinsic proprieties and play a major role in our understanding of modern cosmology. The main caveats associated with standard candles are their absolute calibration, contamination of the sample from other sources and systematic uncertainties. The absolute calibration mainly depends on their chemical composition and age. To understand the impact of these effects on the distance scale, it is essential to develop methods based on different sample of standard candles. Here we review the fundamental properties of young and intermediate-age distance indicators such as Cepheids, Mira variables and Red Clump stars and the recent developments in their application as distance indicators.Comment: Review article, 63 pages (28 figures), Accepted for publication in Space Science Reviews (Chapter 3 of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Age