Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

CSL-1: a chance projection effect or serendipitous discovery of a gravitational lens induced by a cosmic string?

M. Sazhin, G. Longo, J. M. Alcala', R. Silvotti, G. Covone, O. Khovanskaya, M. Pavlov, M. Pannella, M. Radovich, V. Testa

TL;DR

CSL-1 presents a rare double image whose origin is contested between a chance projection of two identical ellipticals at $z = 0.46$ and gravitational lensing by a cosmic string. The authors perform comprehensive photometric and spectroscopic analyses, ruling out ordinary compact lenses and dust obscuration, and propose a cosmic-string lens model that can produce undistorted double images with a deficit angle $D = 8\pi \mu$. From the observed image separation of about $2''$, they estimate $\mu \approx 4\times 10^{-9}$ in Planck units and infer a symmetry-breaking energy scale near $E \sim 2\times 10^{15}$ GeV, with implications for GUT-scale physics. They outline high-resolution optical (and radio) tests to confirm the cosmic-string hypothesis, which, if validated, would provide groundbreaking evidence for cosmic strings and early-universe physics.

Abstract

CSL-1 (Capodimonte--Sternberg--Lens Candidate, No.1) is an extragalactic double source detected in the OAC-DF (Osservatorio Astronomico di Capodimonte - Deep Field). It can be interpreted either as the chance alignment of two identical galaxies at z=0.46 or as the first case of gravitational lensing by a cosmic string. Extensive modeling shows in fact that cosmic strings are the only type of lens which (at least at low angular resolution) can produce undistorted double images of a background source. We propose an experimentum crucis to disentangle between these two possible explanations. If the lensing by a cosmic string should be confirmed, it would provide the first measurements of energy scale of symmetry breaking and of the energy scale of Grand Unified Theory (GUT).

CSL-1: a chance projection effect or serendipitous discovery of a gravitational lens induced by a cosmic string?

TL;DR

CSL-1 presents a rare double image whose origin is contested between a chance projection of two identical ellipticals at and gravitational lensing by a cosmic string. The authors perform comprehensive photometric and spectroscopic analyses, ruling out ordinary compact lenses and dust obscuration, and propose a cosmic-string lens model that can produce undistorted double images with a deficit angle . From the observed image separation of about , they estimate in Planck units and infer a symmetry-breaking energy scale near GeV, with implications for GUT-scale physics. They outline high-resolution optical (and radio) tests to confirm the cosmic-string hypothesis, which, if validated, would provide groundbreaking evidence for cosmic strings and early-universe physics.

Abstract

CSL-1 (Capodimonte--Sternberg--Lens Candidate, No.1) is an extragalactic double source detected in the OAC-DF (Osservatorio Astronomico di Capodimonte - Deep Field). It can be interpreted either as the chance alignment of two identical galaxies at z=0.46 or as the first case of gravitational lensing by a cosmic string. Extensive modeling shows in fact that cosmic strings are the only type of lens which (at least at low angular resolution) can produce undistorted double images of a background source. We propose an experimentum crucis to disentangle between these two possible explanations. If the lensing by a cosmic string should be confirmed, it would provide the first measurements of energy scale of symmetry breaking and of the energy scale of Grand Unified Theory (GUT).

Paper Structure

This paper contains 10 sections, 6 equations, 8 figures, 3 tables.

Table of Contents

  1. Introduction
  2. The observed properties of CSL-1
  3. Morphological and photometric properties
  4. Spectral properties
  5. Putting all together
  6. CSL-1 as a peculiarly obscured object
  7. CSL-1 as a gravitational lens
  8. Compact lens models
  9. Cosmic string model
  10. Discussion and conclusions

Figures (8)

  • Figure 1: Left panel and central inset: appearance of CSL-1 in the R band. Right panel: 2D contours of CSL-1 from the near IR ($\lambda 914$) image. Coordinates are in pixels (1 px $= 0".238$) and the two components are labeled A and B as in the text.
  • Figure 2: Surface brightness profiles obtained for the the components A (dashed line) and B (solid line) in the 914 Å band. The profiles are normalized to the peak intensity and plotted in $r^{1/4}$ units.
  • Figure 3: Left panel: TNG spectra of the components of CSL-1 . Right panel: NTT spectra. A vertical shift was introduced for visualization purposes only. Lower panels: corresponding ratios obtained by dividing the spectra of the two components.
  • Figure 4: Correlation coefficient of NTT spectra of the two components of CSL-1 with background profile removed.
  • Figure 5: Solid line: observed H band profile for CSL-1 ; dashed line: profile expected in the H band following the procedure described in the text (dust index n=1).
  • ...and 3 more figures