Very Large Spectroscopic Surveys with the VLT

Recently, it has been recognised that very large spectroscopic surveys (several million spectra) are required to advance our understanding of Dark Energy (via baryonic wiggles) and the detailed history of our Local Group of galaxies (via Galactic Archeology or near-field cosmology). In this paper I make a preliminary exploration of how this might be done by putting a wide field, optical, prime-focus fibre-fed spectroscopic facility on one of the VLT's UTs.Comment: 6 pages. To be published in the proceedings "Science with the VLT in the ELT era

Pricing externalities from passenger transportation in Mexico city

The Mexico City Metropolitan Area has been suffering severely from transportation externalities such as accidents, air pollution, and traffic congestion. This study examines pricing instruments to reduce these externalities using an analytical and numerical model. The study shows that the optimal levels of a gasoline tax and a congestion toll on automobiles could generate social benefits, measured in terms of welfare gain, of US$132 and US$109 per capita, respectively, through the reduction of externalities. The largest component of the welfare gains comes from reduced congestion, followed by local air pollution reduction. The optimal toll and tax would, however, double the cost of driving and could be politically sensitive. Still, more than half of those welfare gains could be obtained through a more modest tax or toll, equivalent to $1 per gallon of gasoline. The welfare gains from reforming the pricing of public transportation are small relative to those from reforming the taxation of automobiles. Although the choice among travel modes depends on specific circumstances, in the absence of road travel pricing that accounts for externalities, there will be potential for higher investment in roads relative to mass transit. Given the rapidly increasing demand for transportation infrastructure in Mexico City, careful efforts should be made to include the full social costs of travel in evaluating alternative infrastructure investments.Transport Economics Policy&Planning,Roads&Highways,Energy Production and Transportation,Transport and Environment,Transport in Urban Areas

How Should Passenger Travel in Mexico City Be Priced?

This paper uses an analytical-simulation model to examine the optimal extent and welfare effects of pricing reforms for passenger transportation in Mexico City. The model incorporates travel by auto, microbus, public bus, and rail, plus externalities from local and global air pollution, traffic congestion, and road accidents. In our benchmark case, the optimal gasoline tax is $2.72 (29.6 pesos) per gallon, or 16 times the current tax. However, a per-mile toll would reduce traffic congestion, the largest externality, more directly, and we put the optimized auto toll at 20.3 cents per mile. Tolls should also be imposed on microbuses even though the welfare gains are relatively modest, as are those from reforming public transit fares.gasoline taxes, mileage tolls, transit subsidy, pollution, congestion, Mexico City, welfare effects

Revenue recycling and the welfare effects of road pricing

The authors explore the interaction between taxes on work-related traffic congestion and preexisting distortionary taxes in the labor market. A congestion tax raises the overall costs of commuting to work and discourages labor force participation at the margin when revenues are returned in lump-sum transfers. The resulting efficiency loss in the labor market can be larger that the Pigouvian efficiency gains from internalizing the congestion externality. By contrast, if congestion tax revenues are used to reduce labor taxes, the net impact on the labor supply is positive and the efficiency gain in the labor market can raise the overall welfare gains of the congestion tax by as much as 100 percent. Recycling congestion tax revenues in public transit subsidies produces a positive, but smaller, impact on the labor supply. In short, the authors'results indicate that the presence of preexisting tax distortions, and the form of revenue recycling, can crucially affect the size - and possibly even the sign - of the welfare effect of road pricing schemes. The efficiency gains from recycling congestion tax revenues in other tax reductions can amount to several times the Pigouvian welfare gains from congestion reduction.Public Sector Economics&Finance,Economic Theory&Research,Labor Policies,Environmental Economics&Policies,Banks&Banking Reform,Environmental Economics&Policies,Public Sector Economics&Finance,Economic Theory&Research,Banks&Banking Reform,Municipal Financial Management

A Data Cube Extraction Pipeline for a Coronagraphic Integral Field Spectrograph

Project 1640 is a high contrast near-infrared instrument probing the vicinities of nearby stars through the unique combination of an integral field spectrograph with a Lyot coronagraph and a high-order adaptive optics system. The extraordinary data reduction demands, similar those which several new exoplanet imaging instruments will face in the near future, have been met by the novel software algorithms described herein. The Project 1640 Data Cube Extraction Pipeline (PCXP) automates the translation of 3.8*10^4 closely packed, coarsely sampled spectra to a data cube. We implement a robust empirical model of the spectrograph focal plane geometry to register the detector image at sub-pixel precision, and map the cube extraction. We demonstrate our ability to accurately retrieve source spectra based on an observation of Saturn's moon Titan.Comment: 35 pages, 15 figures; accepted for publication in PAS

SPIRAL Phase A: A Prototype Integral Field Spectrograph for the AAT

We present details of a prototype fiber feed for use on the Anglo-Australian Telescope (AAT) that uses a dedicated fiber-fed medium/high resolution (R > 10000) visible-band spectrograph to give integral field spectroscopy (IFS) of an extended object. A focal reducer couples light from the telescope to the close-packed lenslet array and fiber feed, allowing the spectrograph be used on other telescopes with the change of a single lens. By considering the properties of the fibers in the design of the spectrograph, an efficient design can be realised, and we present the first scientific results of a prototype spectrograph using a fiber feed with 37 spatial elements, namely the detection of Lithium confirming a brown dwarf candidate and IFS of the supernova remnant SN1987A.Comment: 41 pages, 15 figures, 3 tables; accepted by PAS

some new techniques for faint object spectroscopy in astronomy

Astronomers require large amounts of spectroscopic data for faint astronomical sources if they are to successfully confront today's most important cosmological and astrophysica1 problems. However, until recently such data has been particularly difficult to acquire and the supply of telescope time available has fallen well short of demand. This thesis describes spectroscopic techniques of high efficiency that allow the data to be obtained using a minimum of telescope time. The technical aspects discussed include instrumentation, observing practices and data reduction. In particular, a new faint object spectrograph for the La Palma Observatory and an automated multi-fibre spectrograph coupler for the Anglo-Australian Telescope are described. It is now feasible for extensive spectroscopic surveys to be carried out at very faint magnitudes

High-resolution spectroscopy and high contrast imaging with the ELT: looking for O-2 in Proxima b

We research the requirements of high contrast imaging when combined with the cross-correlation (CC) of high-resolution spectra with known spectroscopic templates for detecting and characterizing exoplanets in reflected light. We simulate applying the technique to a potentially habitable Proxima b-like planet and show that the O2 A-band spectral feature could feasibly be detected on nearby rocky exoplanets using future instruments on the ELT. The technique is then more widely analysed showing that detections of planets and O2 with signal-to-noise ratio in the CC function (SNRCC) >3 can be obtained when the signal-to-noise ratio of the simulated planet spectrum (SNRspec) is from 0.25 to 1.2. We place constraints on the spectral resolution, instrument contrast, point spread function (PSF), exposure times and systematic error in stellar light subtraction for making such detections. We find that accurate stellar light subtraction (with 99.99 per cent removal) and PSFs with high spatial resolutions are key to making detections. Lastly a further investigation suggests the ELT could potentially discover and characterize planets of all sizes around different spectral type stars, as well as detecting O2 on super-Earths with habitable zone orbits around nearby M stars.GAH acknowledges the support of an STFC PhD Studentship in writing the manuscript

Spectroscopic Gravitational Lensing and Limits on the Dark Matter Substructure in Q2237+0305

Spatially resolved spectroscopic data from the CIRPASS integral field unit (IFU) on Gemini are used to measure the gravitational lensing of the 4-image quasar Q2237+0305 on different size scales. A method for measuring the substructure present in the lens using observations at multiple wavelengths is demonstrated to be very effective and independent of many of the degeneracies inherent in previous methods. The magnification ratios of the QSO's narrow line region (NLR) and broad line region (BLR) are measured and found to be disagree with each other and with the published radio and mid-infrared magnification ratios. The disagreement between the BLR ratios and the radio/mid-infrared ratios is interpreted as microlensing by stars in the lens galaxy of the BLR The disagreement between the radio/mid-infrared ratios and the NLR ratios is interpreted as a signature of substructure on a larger scale, possibly the missing small scale structure predicted by the standard cold dark matter (CDM) model. Certain combinations of the radial profile and the substructure surface densities are ruled out using extensive lensing simulations. A substructure mass scale as large as 10^8 M is strongly disfavored while 10^4 M is too small if the radio and mid-infrared emission regions have the expected sizes of ~10 pc. The standard elliptical isothermal lens mass profile is not compatible with a substructure surface density of < 280 M/pc^2 at the 95% confidence level. This is 4-7% of the galaxy's surface density (depending on which image position is used to evaluate this). The required substructure surface density at the required mass scale is high in comparison with the present expectations within the CDM model.Comment: 29 pages, 16 figures, submitted to Ap

Constraining mass ratio and extinction in the FU Orionis binary system with infrared integral field spectroscopy

We report low resolution near infrared spectroscopic observations of the eruptive star FU Orionis using the Integral Field Spectrograph Project 1640 installed at the Palomar Hale telescope. This work focuses on elucidating the nature of the faint source, located 0.5" south of FU Ori, and identified in 2003 as FU Ori S. We first use our observations in conjunction with published data to demonstrate that the two stars are indeed physically associated and form a true binary pair. We then proceed to extract J and H band spectro-photometry using the damped LOCI algorithm, a reduction method tailored for high contrast science with IFS. This is the first communication reporting the high accuracy of this technique, pioneered by the Project 1640 team, on a faint astronomical source. We use our low resolution near infrared spectrum in conjunction with 10.2 micron interferometric data to constrain the infrared excess of FU Ori S. We then focus on estimating the bulk physical properties of FU Ori S. Our models lead to estimates of an object heavily reddened, A_V =8-12, with an effective temperature of ~ 4000-6500 K . Finally we put these results in the context of the FU Ori N-S system and argue that our analysis provides evidence that FU Ori S might be the more massive component of this binary syste