Cycle 11 General Observer Proposal

Redshifts and Recession Velocities of the Einstein Cross Q2337+030 and Huchra’s Lens ZW2337+030

Principal Investigator: Ms. Glenna Dunn Institution: Stony Brook University USA/NY Electronic mail: [email protected] Scientific category: COSMOLOGY Scientific keywords: GRAVITATIONAL LENSING, COSMOLOGICAL PARAMETERS AND DISTANCE SCALE, SPECTROSCOPY Instruments: COS Proprietary period: 12 Cycle 11 primary orbits: 10 Cycle 11 parallel orbits: 0

Special Proposal Types: Innovative

Abstract

The galaxy Huchra’s Lens ZW2237+030 acts as a to the Q2237+030, forming four distinct images of the quasar in a cruciform known as an Ein- stein Cross. I propose to analyze the spectra of the brightest of the four images and the foreground galaxy to measure the of the Lyman alpha lines. I intend to use the Cosmic Origins Spectrograph (COS) to observe the of the Lyman alpha lines in the ultraviolet. The measurements will allow for the calculations of several cosmological values through the use of the z parameter and the Hubble constant. These include the recessional velocites and distances of these objects, and the scale factor of the universe since the time the light was emitted from the objects. Ms. Glenna Dunn Redshifts and Recession Velocities of the Einstein Cross Q2337+030 and Huchra’s Lens ZW2337+030

Investigator Institution Country PI: Ms. Glenna Dunn Stony Brook University USA/NY Total number of investigators: 1

Observing Summary: Configuration,mode,aperture Total Target RA DEC V spectral elements orbits Flags Q2237+0305A 22 40 30.27 3 21 31.03 16.78 COS UV 5 G130M,G160M,G160L ZW2237+030 22 40 30 3 21 30 16.78 COS UV 5 G130M,G160M,G160L Grand total orbit request 10

2 Ms. Glenna Dunn Redshifts and Recession Velocities of the Einstein Cross Q2337+030 and Huchra’s Lens ZW2337+030

Scientific Justification

The spectroscopic analysis of Q2237+030 and ZW2237+030 and the determination of the redshift of each object will allow for the calcualtion of cosmological values that give quanti- tative insight to the structure of the universe. These include recessional velocities, distances, and the expansion of the universe over the period of time since the emission of light from the object and the time it reaches Earth. It is important to obtain these values because the study of and distant galaxies allows us to discern new information about the universe. The redshifts of both the quasar and the foreground galaxy will be found through an analysis of the Lyman alpha lines in the ultraviolet. The Cosmic Origins Spectrograph is an ideal tool for this type of observation, because it is designed specifically to observe faint extragalactic objects in the ultraviolet. A gravitationally lensed quasar and its lensing galaxy such as the Q2237+030 system are good candidates for the use of the COS because observations of these objects will further our understanding of a number of cosmological and structural parameters of the universe, which is one of the primary objectives of this instrument. The recessional velocities of each of these targets will be found by taking the ratio of the change in wavelength of the emission line to the standard value for the emission v ∆λ 1+ c line , which gives us z parameter. The equation z = , z = − v . This gives the ratio of λ r 1 c 2 v (z+1) −1 the recessional velocity to the speed of light, c = (z+1)2+1 . Since the recessional velocities are functions of distance, the the measurement of the spectral redshifts will also allow for the calculation of the distance to these objects through Hubble’s Law. The Hubble distance d v H to an object is given as = H0 where 0 is the Hubble constant as measured by WMAP  km at 71 4 sMpc . Finally, the z parameter will also give the scale factor of the universe, where z λ R(t0) 1 R t + 1 = λ0 = R(t) = R(t) . In this equation, ( 0) = 1 to designate present time. Therefore, if it is foud that the quasar has a z parameter of one, then we will know that the universe has expanded by a factor of two since the time that the quasar emitted the observed light. The measurement and study of the redshifts of spectral lines has wide implications in cosmolgy and the study of the universe. It would be advantageous to study this gravitation- ally lensed system using the Cosmic Origins Spectrograph becaause it involves two objects along the same light of sight at different distances which will therefore display different red- shifts and recessional velocites, both of which are ideally observed in the ultraviolet by an instrument such as the COS. Description of the Observations

I intend to take the ultraviolet spectra of the the brightest image of the quasar, Q2237+0305A, and the foreground lensing galaxy, ZW2237+030. I will use the Primary Science Aperture (PSA) and the Far Ultra-Violet detector (FUV) with the G130M, G160M, and G140L grat- ings. While the Lyman alpha lines are emitted at 1215.67 Angstrom, they are expected to redshift considerably. The G140L grating will be used to located the spectral line, and the

3 Ms. Glenna Dunn Redshifts and Recession Velocities of the Einstein Cross Q2337+030 and Huchra’s Lens ZW2337+030

high resolving power of the G130M and G160M gratings will be used to precisely measure the redshift of the spectral line. Each of the two targets will be observed with all three gratings, and one measurement will be taken per object per grating. The exposure time for the G10L grating on both targets will be 800s, and the G130M and G160M grating exposure times will be 500s. A total of 10 orbits are needed for this observation, with 5 orbits per target. Justify Duplications

All previous observations of Q2237+030 using the Hubble Space Telescope have focused on the imaging of this object. The observations were used to verify the presence of this object and analyze the configuration of the Einstein Cross that is formed by the gravitational lensing of this quasar. This would be the first HST observation to analyze the spectra of this object.

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