The fundamental plane of evolving red nuggets

We present an exploration of the mass structure of a sample of 12 strongly lensed massive, compact early-type galaxies at redshifts $z\sim0.6$ to provide further possible evidence for their inside-out growth. We obtain new ESI/Keck spectroscopy and infer the kinematics of both lens and source galaxies, and combine these with existing photometry to construct (a) the fundamental plane (FP) of the source galaxies and (b) physical models for their dark and luminous mass structure. We find their FP to be tilted towards the virial plane relative to the local FP, and attribute this to their unusual compactness, which causes their kinematics to be totally dominated by the stellar mass as opposed to their dark matter; that their FP is nevertheless still inconsistent with the virial plane implies that both the stellar and dark structure of early-type galaxies is non-homologous. We also find the intrinsic scatter of their FP to be comparable to the local value, indicating that variations in the stellar mass structure outweight variations in the dark halo in the central regions of early-type galaxies. Finally, we show that inference on the dark halo structure -- and, in turn, the underlying physics -- is sensitive to assumptions about the stellar initial mass function (IMF), but that physically-motivated assumptions about the IMF imply haloes with sub-NFW inner density slopes, and may present further evidence for the inside-out growth of compact early-type galaxies via minor mergers and accretion.Comment: 10 pages, 3 figures, 3 tables; submitted to MNRA

Land use patterns and access in Mexico City

The problem of distribution of land uses in urban space in Latin American cities has been examined under different perspectives. Most authors tend to model patterns of population and land use as a consequence of social and economic processes alone, failing to address urban space as an intrinsic variable. Instead, the theory of cities as movement economies argues that land use patterns are influenced by movement flows, which are in turn strongly affected by the urban grid. As a result, land uses such as retail would seek highly accessible locations to take advantage of such flows while residential uses would avoid them. However, space syntax techniques traditionally used to point out this relationship do not seem to reveal it so easily in non-organic cities like Mexico. This paper addresses the relationship between patterns of accessibility and land use in the first ring of Mexico City as a spatial strategy. A new functional description of the city where plots are nodes connected to flows that represent the street network is adopted. This model enables us to measure accessibility at the level of plots. Following this, we focus on the occurrence of land use types in highly or low accessible locations using cumulative distribution functions. If the distribution of land uses was random, the proportion of land use types would be more or less uniform throughout the area. It is shown that the relationship between accessibility and land use is not linear and is guided by movement economy forces. It is suggested that the understanding of these relationship is key to plan for sustainable growth objectively

The Place Premium: Wage Differences for Identical Workers across the US Border

We estimate the “place premium”—the wage gain that accrues to foreign workers who arrive to work in the United States. First, we estimate the predicted, purchasing-power adjusted wages of people inside and outside the United States who are otherwise observably identical—with the same country of birth, country of education, years of education, work experience, sex, and rural or urban residence. We use new and uniquely rich micro-data on the wages and characteristics of over two million individual formal-sector wage-earners in 43 countries (including the US). Second, we examine the extent to which these wage ratios for observably equivalent workers may overstate the gains to a marginal mover because movers may be positively selected on unobservable productivity in their home country. New evidence for nine of the countries, combined with a range of existing evidence, suggests that this overstatement can be significant, but is typically modest in magnitude. Third, we estimate the degree to which policy barriers to labor movement in and of themselves sustain the place premium, by bounding the premia observed under self-selected migration alone. Finally, we show that the policy induced portion of the place premium in wages represents one of the largest remaining price distortions in any global market; is much larger than wage discrimination in spatially integrated markets; and makes labor mobility capable of reducing households’ poverty at the margin by much more than any known in situ intervention.migration, wage discrimination, price distortions, policy barriers, place premium, poverty.

A critique of the econometrics of happiness: Are we underestimating the returns to education and income?

A large "happiness", or life satisfaction, literature in economics makes use of Likert-like scales in assessing survey respondents' cognitive evaluations of their lives. These measures are being used to estimate economic benefits in every empirical field of economics. Typically, analysis of these data have shown remarkably low direct returns of education for improving subjective well-being. In addition, arguably, the inferred impact of material wealth and income using this method is also unexpectedly low as compared with other, social factors, and as compared with economists' prior expectations which underlie, in some sense, support for using GDP as a proxy for more general quality of life goals. Discrete response scales used ubiquitously for the reporting of life satisfaction pose cognitive challenges to survey respondents, so differing cognitive abilities result in different uses of the scale, and thus potential bias in statistical inference. This problem has so far gone unnoticed. An overlooked feature of the distribution of responses to life satisfaction questions is that they exhibit certain enhancements at focal values, in particular at 0, 5, and 10 on the eleven-point scale. In this paper, I investigate the reasons for, and implications of, these response patterns. I use a model to account for the focal-value behavior using a latent variable approach to capture the "internal" cognitive evaluation before it is translated to the discrete scale of a survey question. This approach, supported by other more heuristic ones, finds a significant upward correction for the effects of both education and income on life satisfaction

Keck Deep Fields. I. Observations, Reductions, and the Selection of Faint Star-Forming Galaxies at Redshifts z~4, 3, and 2

We introduce a very deep, R_lim~27, multicolor imaging survey of very faint star-forming galaxies at z~4, z~3, z~2.2, and z~1.7. This survey, carried out on the Keck I telescope, uses the very same UGRI filter system that is employed by the Steidel team to select galaxies at these redshifts, and thus allows us to construct identically-selected, but much fainter, samples. However, our survey reaches ~1.5 mag deeper than the work of Steidel and his group, letting us probe substantially below the characteristic luminosity L* and thus study the properties and redshift evolution of the faint component of the high-z galaxy population. The survey covers 169 square arcminutes in three spatially independent patches on the sky and -- to R<~27 -- contains 427 GRI-selected z~4 LBGs, 1481 UGR-selected z~3 LBGs, 2417 UGR-selected z~2.2 star-forming galaxies, and 2043 UGR-selected z~1.7 star-forming galaxies. In this paper, the first in a series, we introduce the survey, describe our observing and data reduction strategies, and outline the selection of our z~4, z~3, z~2.2, and z~1.7 samples.Comment: To appear in Ap

How Much Do Teachers Earn?

In the continuing debate over how to improve education systems, many people argue that teachers` salaries need to be increased. This paper seeks to establish a reliable method for analyzing the issue using household survey data from Bolivia.

Red nuggets grow inside-out: evidence from gravitational lensing

We present a new sample of strong gravitational lens systems where both the foreground lenses and background sources are early-type galaxies. Using imaging from HST/ACS and Keck/NIRC2, we model the surface brightness distributions and show that the sources form a distinct population of massive, compact galaxies at redshifts $0.4 \lesssim z \lesssim 0.7$, lying systematically below the size-mass relation of the global elliptical galaxy population at those redshifts. These may therefore represent relics of high-redshift red nuggets or their partly-evolved descendants. We exploit the magnifying effect of lensing to investigate the structural properties, stellar masses and stellar populations of these objects with a view to understanding their evolution. We model these objects parametrically and find that they generally require two S\'ersic components to properly describe their light profiles, with one more spheroidal component alongside a more envelope-like component, which is slightly more extended though still compact. This is consistent with the hypothesis of the inside-out growth of these objects via minor mergers. We also find that the sources can be characterised by red-to-blue colour gradients as a function of radius which are stronger at low redshift -- indicative of ongoing accretion -- but that their environments generally appear consistent with that of the general elliptical galaxy population, contrary to recent suggestions that these objects are predominantly associated with clusters.Comment: 21 pages; accepted for publication in MNRA