A deep redshift survey of field galaxies. Comments on the reality of the Butcher-Oemler effect

A spectroscopic survey of over 400 field galaxies has been completed in three fields for which we have deep UBVI photographic photometry. The galaxies typically range from B=20 to 22 and possess redshifts z from 0.1 to 0.5 that are often quite spiky in distribution. Little, if any, luminosity evolution is observed up to redshifts z approx 0.5. By such redshifts, however, an unexpectedly large fraction of luminous galaxies has very blue intrinsic colors that suggest extensive star formation; in contrast, the reddest galaxies still have colors that match those of present-day ellipticals

The world in balance sheet recession: Causes, cure, and politics

Hay bastante confusión en los círculos políticos, académicos y también en los mercados con respecto a la situación económica internacional que se desencadenó por la crisis de 2007-2008. Y como hay tanta confusión, las respuestas de política económica han sido en gran parte inconsistentes, no solo en EEUU si no por todo el mundo, y esto puede estar prolongando innecesariamente la recesión. Sin embargo, lo que estamos viviendo actualmente ocurrió en Japón hace exactamente quince años. Lo que está pasando ahora, después del estallido de la burbuja, es que el sector privado se está desapalancando o reduciendo su deuda al mínimo. Esto se denomina recesión de balances. Y, en este tipo de recesión, recortar los tipos de interés al cero y aumentar la base monetaria no se traduce en una mejora del acceso al crédito del sector privado y en una recuperación de la actividad económica. La política monetaria se vuelve ineficaz. Tal y como muestra la experiencia japonesa, la respuesta para prevenir el colapso de la actividad económica reside en la política fiscal, esto es, el gobierno debe incrementar el gasto financiándose a si mismo con los ahorros que el sector privado genera al desapalancarse. Solo después de que los balances hayan sido saneados y el sector privado esté deseando, y pueda, endeudarse, puede empezar el gobierno a reducir su déficit presupuestarioThere is quite a bit of confusion in the policy circles, in the academic circles and also in the markets regarding the international economic situation unleashed by the 2007-2008 crisis. And, as there is so much confusion, the economic policy responses have been largely inconsistent, not only in the United States but also all around the world, and this might be prolonging the recession unnecessarily. However, what we are currently going through happened in Japan exactly 15 years ago. What is happening now is that, after the bursting of the bubble, the private sector is deleveraging or reducing its debt to a minimum. This is called a balance sheet recession. And, in this type of recession, cutting the interest rate to zero and increasing the monetary base do not translate into an improvement of credit to the private sector and into a recovery of economic activity. The monetary policy becomes ineffective. As shown by the Japanese experience, the response to prevent the collapse of economic activity lies in the fiscal policy, i.e. the government should increase spending by financing itself with the savings the private sector generates in order to deleverage. Only after the balance sheets have been repaired and the private sector is willing to, and may, get into debt, should the government start to cut its budget deficit

El mundo en recesión de balances: causas, cura y políticas

Hay bastante confusión en los círculos políticos, académicos y también en los mercados con respecto a la situación económica internacional que se desencadenó por la crisis de 2007-2008. Y como hay tanta confusión, las respuestas de política económica han sido en gran parte inconsistentes, no solo en EEUU si no por todo el mundo, y esto puede estar prolongando innecesariamente la recesión. Sin embargo, lo que estamos viviendo actualmente ocurrió en Japón hace exactamente quince años. Lo que está pasando ahora, después del estallido de la burbuja, es que el sector privado se está desapalancando o reduciendo su deuda al mínimo. Esto se denomina recesión de balances. Y, en este tipo de recesión, recortar los tipos de interés al cero y aumentar la base monetaria no se traduce en una mejora del acceso al crédito del sector privado y en una recuperación de la actividad económica. La política monetaria se vuelve ineficaz. Tal y como muestra la experiencia japonesa, la respuesta para prevenir el colapso de la actividad económica reside en la política fiscal, esto es, el gobierno debe incrementar el gasto financiándose a si mismo con los ahorros que el sector privado genera al desapalancarse. Solo después de que los balances hayan sido saneados y el sector privado esté deseando, y pueda, endeudarse, puede empezar el gobierno a reducir su déficit presupuestario

HST Observations of the Distant Cluster 0016+16: Quantitative Morphology of Confirmed Cluster Members

We present HST images of 24 confirmed members of the distant galaxy cluster Cl0016+16 at redshift 0.55. The Balmer-strong (``E+A'') and emission- line galaxies frequently show unusual visual morphology, implying that galaxian interactions produce ``active'' galaxies in moderate-redshift clusters. We use the image concentration index as a quantitative measure of morphology to show that these unusual galaxies appear disklike, while the normal red galaxies resemble E/S0s. Although consistent with HST observations by Dressler et al. in Cl0939+4713 ($z=0.41$), our results differ from the Couch et al. finding that most Balmer-strong galaxies in AC114 ($z=0.31$) resemble ellipticals. The entire ``E+A'' sample is small, but if future studies confirm their diversity, it will suggest that they have different origins.Comment: 11 pages, uuencoded compressed PostScript, accepted to ApJ Letters, LICK-3

The Luminosity Function for L>L* Galaxies at z > 3

Through use of multiband (U, B, R, I) photometry we have isolated high redshift (3.0<z<3.5) galaxy candidates in a survey of 1.27 deg^2 to R = 21.25 and a survey of 0.02 deg^2 to R = 23.5. Our pool of candidates constrains the nature of the 3.0 < z < 3.5 luminosity function over the range L* < L < 100 L*, if we grant a similar level of completeness to these data as for very faint samples (to R = 25.5) selected in a similar fashion. Our constraints agree with the high redshift sky density at R = 20.5 estimated from Yee et al.'s (1996) serendipitous discovery of a bright, z = 2.7 galaxy, as well as the density at R ~ 23 by Steidel et al. (1996b). We strongly rule out -- by more than two orders of magnitude at M(R) = -25 -- the L > L* luminosity function for z = 3-5 galaxies obtained by a photometric redshift analysis of the Hubble Deep Field (HDF) by Gwyn & Hartwick (1996). Our results at R ~ 23 are more consistent with the photometric redshift analysis of the faint HDF galaxies by Sawicki & Yee (1996), but our present upper limits at the brightest magnitudes (R < 21.5, M(R) < -24) allow more generous volume densities of these super-L* galaxies.Comment: Accepted for publication in ApJ Letters; 14 pages Latex, including 3 figure

Survey incompleteness and the evolution of the QSO luminosity function

We concentrate on a type of QSO survey which depends on selecting QSO candidates based on combinations of colors. Since QSO's have emission lines and power-law continua, they are expected to yield broadband colors unlike those of stellar photospheres. Previously, the fraction of QSO's expected to be hiding (unselected) within the locus of stellar (U-J, J-F) colors was estimated at about 15 percent. We have now verified that the KK88 survey is at least 11 percent incomplete, but have determined that it may be as much as 34 percent incomplete. The 'missing' QSO's are expected to be predominantly at z less than or = 2.2. We have studied the proper motion and variability properties of all stellar objects with J less than or = 22.5 or F less than or = 21.5 in the SA 57 field which has previously been surveyed with a multicolor QSO search by KK88

Climate change: Impact on agriculture and costs of adaptation

"The Challenge The unimpeded growth of greenhouse gas emissions is raising the earth’s temperature. The consequences include melting glaciers, more precipitation, more and more extreme weather events, and shifting seasons. The accelerating pace of climate change, combined with global population and income growth, threatens food security everywhere. Agriculture is extremely vulnerable to climate change. Higher temperatures eventually reduce yields of desirable crops while encouraging weed and pest proliferation. Changes in precipitation patterns increase the likelihood of short-run crop failures and long-run production declines. Although there will be gains in some crops in some regions of the world, the overall impacts of climate change on agriculture are expected to be negative, threatening global food security. Populations in the developing world, which are already vulnerable and food insecure, are likely to be the most seriously affected. In 2005, nearly half of the economically active population in developing countries—2.5 billion people—relied on agriculture for its livelihood. Today, 75 percent of the world’s poor live in rural areas. This Food Policy Report presents research results that quantify the climate-change impacts mentioned above, assesses the consequences for food security, and estimates the investments that would offset the negative consequences for human well-being. This analysis brings together, for the first time, detailed modeling of crop growth under climate change with insights from an extremely detailed global agriculture model, using two climate scenarios to simulate future climate. The results of the analysis suggest that agriculture and human well-being will be negatively affected by climate change: * In developing countries, climate change will cause yield declines for the most important crops. South Asia will be particularly hard hit. * Climate change will have varying effects on irrigated yields across regions, but irrigated yields for all crops in South Asia will experience large declines. * Climate change will result in additional price increases for the most important agricultural crops–rice, wheat, maize, and soybeans. Higher feed prices will result in higher meat prices. As a result, climate change will reduce the growth in meat consumption slightly and cause a more substantial fall in cereals consumption. * Calorie availability in 2050 will not only be lower than in the no–climate-change scenario—it will actually decline relative to 2000 levels throughout the developing world. * By 2050, the decline in calorie availability will increase child malnutrition by 20 percent relative to a world with no climate change. Climate change will eliminate much of the improvement in child malnourishment levels that would occur with no climate change. * Thus, aggressive agricultural productivity investments of US$7.1–7.3 billion are needed to raise calorie consumption enough to offset the negative impacts of climate change on the health and well-being of children." from TextAdaptation, Agriculture, Climate change, Developing countries, food security,

Innovation Contests with Entry Auction

We consider procurement of an innovation from heterogeneous sellers. Innovations are random but depend on unobservable effort and private information. We compare two procurement mechanisms where potential sellers first bid in an auction for admission to an innovation contest. After the contest, an innovation is procured employing either a fixed prize or a first-price auction. We characterize Bayesian Nash equilibria such that both mechanisms are payoff-equivalent and induce the same efforts and innovations. In these equilibria, signaling in the entry auction does not occur since contestants play a simple strategy that does not depend on rivals' private information

The DEEP2 Galaxy Redshift Survey: Spectral classification of galaxies at z~1

We present a Principal Component Analysis (PCA)-based spectral classification, eta, for the first 5600 galaxies observed in the DEEP2 Redshift Survey. This parameter provides a very pronounced separation between absorption and emission dominated galaxy spectra - corresponding to passively evolving and actively star-forming galaxies in the survey respectively. In addition it is shown that despite the high resolution of the observed spectra, this parameter alone can be used to quite accurately reconstruct any given galaxy spectrum, suggesting there are not many `degrees of freedom' in the observed spectra of this galaxy population. It is argued that this form of classification, eta, will be particularly valuable in making future comparisons between high and low-redshift galaxy surveys for which very large spectroscopic samples are now readily available, particularly when used in conjunction with high-resolution spectral synthesis models which will be made public in the near future. We also discuss the relative advantages of this approach to distant galaxy classification compared to other methods such as colors and morphologies. Finally, we compare the classification derived here with that adopted for the 2dF Galaxy Redshift Survey and in so doing show that the two systems are very similar. This will be particularly useful in subsequent analyses when making comparisons between results from each of these surveys to study evolution in the galaxy populations and large-scale structure.Comment: 10 pages, 9 figures, Accepted for publication in Ap

Star Clusters in the Nearby Late-Type Galaxy NGC 1311

Ultraviolet, optical and near infrared images of the nearby (D ~ 5.5 Mpc) SBm galaxy NGC 1311, obtained with the Hubble Space Telescope, reveal a small population of 13 candidate star clusters. We identify candidate star clusters based on a combination of their luminosity, extent and spectral energy distribution. The masses of the cluster candidates range from ~1000 up to ~100000 Solar masses, and show a strong positive trend of larger mass with increasing with cluster age. Such a trend follows from the fading and dissolution of old, low-mass clusters, and the lack of any young super star clusters of the sort often formed in strong starbursts. The cluster age distribution is consistent with a bursting mode of cluster formation, with active episodes of age ~10 Myr, ~100 Myr and ~1 Gyr. The ranges of age and mass we probe are consistent with those of the star clusters found in quiescent Local Group dwarf galaxies.Comment: 21 pages, 11 figures, accepted by A