Space Warps Talk

Letter on modeled candidate SN Refsdal

  • Budgieye by Budgieye moderator

    Citizen Scientists Perform Collaborative Modelling of a Gravitational Lens on multiple images of Supernova Refsdal using SpaghettiLens.
    By Budgieye

    Summary:

    Citizen scientist
    Citizen scientists can develop models of strong gravitational lenses by using a simple program called SpaghettiLens. This program has been tested previously by volunteers who ran simulations of lensed galaxies and quasars. In this study, we test the simulation program on multiple images of a supernova SN Refsdal which was lensed by an elliptical galaxy. Also, we ran additional estimations of the delay time as the light from various images of the supernova passed through the gravity well.... The results will hopefully show that our results can ....

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  • Budgieye by Budgieye moderator

    Introduction

    SpaghettiLens is program developed by Rafael Kueng for SpaceWarps volunteers in which they can easily model Strong Gravitational Lenses discovered in SpaceWarps, which is a citizen science project which uses volunteers to identify possible strong gravitational lenses in images of galaxies. The discovery of a lensed supernova has presented another opportunity for citizen scientists to test SpahettiLens and compare its performance with a

    In 1964, S. Fefsdal proposed that the light from a distant supernova could pass through a strong gravitational lens and produce multiple images. A set of images in the shape of an Einstein Cross has now been observed by Kelly et al 2014 in Hubble Space Telescope images in the Frontier Fields project, a variation of the "Deep Field" images.

    During the last 15 years, Hubble Space Telescope has produced several "Deep Field" images. The telescope collected light from parts of the sky where was apparently nothing, but showed thousands of galaxies.

    "The Hubble Space Telescope Frontier Fields" http://frontierfields.org/meet-the-frontier-fields/ . Instead of looking at blank parts of the sky, HST is staring at the area around galaxy clusters, using them as a strong gravitational lens to magnify distant galaxies.

    One galaxy cluster looked at in November 2014 is MACS J1149.5+2223 http://frontierfields.org/meet-the-frontier-fields/macsj1149/ Initial examination of the data by Kelly et al 2014 showed a lensed spiral galaxy showing 4 smeared images, with a bright spot in the middle of each lensed galaxy. The spots were labeled S1, S2, S3 and S4 and form an Einstein cross with an 2" diameter.

    enter image description here
    (Image: Patrick L. Kelly et al (arXiv:1411.6009 [astro-ph.CO]))

    The bright spots were not present in older archived images (Kelly, 2014) so is likely to be a supernova. The object can be shown to be a supernova in two ways. A light curve can be made as supernova fades over a period of months. Also, a spectral chart can be taken. HST can do these over the next few months. Kelly, 2014.

    If the object is a supernova, then the various lensed images will be transient since a supernova fades in several months. . A lensed image where the light has to go through a deeper gravity well, will take longer to get to us, creating a time delay in the arrival of the image. Since supernova are transient, the light from some images paths will have faded by the time other images arrive. Kelly 2014 suggests that additonal image of the supernova may have appeared already 20 years previously, or may appear in the future, possibly in about a decade. Oguri 2014 predicts that there should be 6 lensed images, one of the images would have appeared 17 years ago and consequently faded by the time that the Hubble images were taken, and another to appear in a year's time.

    The location of the images of the lensed supernova were determined by image subtraction, and green circles denoting their location added to the colour images, shown below (Kelly) . S1 and S2 show little change in brightness of during the two weeks of observation, S3 exhibits a clear rise in brightness, and S4 is faint and difficult to plot a light curve. (Kelly ) The red circles indicate the location of lensed images of the arm of the lensed galaxy. The elliptical galaxy is seen shining through the arms of a intervening spiral galaxy.

    enter image description here

    Kelly (2014) started modelling the lens on the observations obtained so far. He used a simple ellipsoid mass with a shear factor due to the mass of the other ellipticals of the cluster. The redshift of the lensing elliptical was determined to spectroscopy to be z=0.544 and the redshift of the lensed spiral to be z=1.491, though the redshift of the supernova itself will be determined in 2015. (I'm not sure where Kelly got this data, I suppose I could look up the Hubble data)

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  • Budgieye by Budgieye moderator

    Method: Spaghetti Lens Model and the collaborative process, Images of the supernova.

    The collaborative process

    The modeling tool "SpaghettiLens" which was designed by R. Kung was used by volunteers, and modeling results posted on a thread in SpaceWarps. The colour image with green circles from Kelly et al 2-14 was selected as the initial candidate and a model created. Volunteers then made modifications to the model, and posted the result also noting the parent of the model, the changes made to the model, the results of the changes and suggestions for further improvements. A volunteer could change their own model, or select another volunteers to change. One of us also selected the black and white image for modeling. The genealogy of the improvements to the model was recorded.

    SpaghettiLens has adjustable redshift values. For the lensed galaxy, we used z=1.491 and for the lensing ellptical galaxy we used z=0.544. The program can also add the effect of other galaxy masses in additon to the lensing galaxy.

    The criteria for a sucessful model is explained by Capella05 (2014). Several successful models were submitted to Rafael Kung for a determination of the delay time for the light (name of Kung's program?)

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  • Budgieye by Budgieye moderator

    Results

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  • Budgieye by Budgieye moderator

    Discussion

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  • Budgieye by Budgieye moderator

    Acknowedgements

    The Swiss Astronomical Society for kindly sponsoring a lens modelling workshop at the Universe of Zurich.

    The computer facilities at the Universe of Zurich.

    The Zooniverse citizen science project for their use of SpaceWarps website for volunteers to use.

    By the way, the new "shear" slider is an upper limit that you allow for SpL.
    The actual shear value chosen by SpL can be any value lower than the slider.
    Shear in lensing refers to big masses comparatively far away --in this
    case, the main part of the cluster--- that act as perturbers to the
    gravitational field of the galaxy. So feel free to pull the shear slider all the way to the right

    References

    Refsdal , S 1964 On the Possibility of Determining Hubble's Parameter and the Masses of Galaxies from the Gravitational Lens Effect http://mnras.oxfordjournals.org/content/128/4/307.full.pdf+html

    Kelly, P L et al,, Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
    Cite as: arXiv:1411.6009v2 [astro-ph.CO] for this version)

    Capella05 2014vCollaborative Gravitational Lens Modelling using SpaghettiLens - A SpaceWarps Project. http://letters.zooniverse.org/letters/86-collaborative_gravitational_lens_modelling_using_spaghettilens_a_spacewarps_project

    Kung et al 2014 Gravitational Lens Modelling in a Citizen Science Context ref. MN-14-3183-MJMATEX style file v2.2) Gravitational Lens Modelling in a Citizen Science Context Rafael Küng, Prasenjit Saha, Anupreeta More,Elisabeth Baeten, Jonathan Coles, Claude Cornen, Christine Macmillan, Phil Marshall, Surhud More, Jonas Odermatt,
    Aprajita Verma and Julianne K. Wilcox

    Norden et al Feb 2014 Lensed Type Ia supernovae as probes of cluster mass models http://mnras.oxfordjournals.org/content/440/3/2742.abstract Using three magnified Type Ia supernovae (SNe Ia) detected behind CLASH (Cluster Lensing and Supernovae with Hubble) clusters, we perform a first pilot study to see whether standardizable candles can be used to calibrate cluster mass maps created from strong lensing observations. Such calibrations will be crucial when next-generation Hubble Space Telescope cluster surveys (e.g. Frontier) provide magnification maps that will, in turn, form the basis for the exploration of the high-redshift Universe

    Masamune Oguri Nov 2014 Predicted properties of multiple images of the strongly lensed supernova SN Refsdal http://arxiv.org/abs/1411.6443.pdf http://arxiv.org/pdf/1411.6443v1.pdf arXiv:1411.6443 [astro-ph.CO] Mon. Not. R. Astron. Soc. 000, 1–4 () Printed 25 November 2014

    SpaceWarps, a Zooinverse project. http://spacewarps.org/

    Notes:

    http://archive.stsci.edu/prepds/frontier/ archived data for cluster in Frontier Fields

    http://hla.stsci.edu/hlaview.html#Images|filterText%3D%24filterTypes%3D|query_string=MACS J1149.5%2B2223&posfilename=&poslocalname=&posfilecount=&listdelimiter=whitespace&listformat=degrees&RA=177.392920&Dec=22.395140&Radius=0.200000&inst-control=all&inst=ACS&inst=ACSGrism&inst=WFC3&inst=WFPC2&inst=NICMOS&inst=NICGRISM&inst=COS&inst=WFPC2-PC&inst=STIS&inst=FOS&inst=GHRS&imagetype=best&prop_id=&spectral_elt=&proprietary=both&preview=1&output_size=256&cutout_size=12.8|ra=&dec=&sr=&level=&image=&inst=ACS%2CACSGrism%2CWFC3%2CWFPC2%2CNICMOS%2CNICGRISM%2CCOS%2CWFPC2-PC%2CSTIS%2CFOS%2CGHRS&ds= archived data

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