I’m a researcher at Stockholm University interested in supernovae and cosmic dust
About me
I’m a researcher at the Physics Department of Stockholm University and the Oskar Klein Centre for Cosmoparticle physics.
My research is related to cosmic dust and all sorts of supernovae from the Zwicky Transient Facility (ZTF), the Public ESO Spectroscopic Survey for Transient Objects (PESSTO) and the Spitzer Infrared Intensive Transient Survey (SPIRITS).
I was previously at the at the department of Astronomy and Physics at Uppsala University and the Weizmann Institute of Science.
Research
Transient surveys
I am involved in the Zwicky Transient Facility (ZTF), which discover supernovae at optical wavelengths by systematically imaging the sky, several times per night, with the robotic Palomar 48-inch telescope.
I’m also part of the the Spitzer Infrared Intensive Transients Survey (SPIRITS), which was the first survey of its kind, exploring the dynamic infrared sky.
Supernovae
Supernovae are the explosive deaths of stars. Since stars of different mass follow different evolutionary tracks they face different end stages, which gives rise to a large variety of luminosities and spectral features among the supernovae.
One special type of supernovae, Type Ia, appears to always explode with the same brightness, making them useful as distance indicators. The acceler1ated expansion of the Universe was discovered using SNe Ia, leading to Perlmutter, Schmidt & Riess being awarded the Nobel Prize in 2011. While the use of SNe Ia remains essential for the studying the properties of the “dark energy” driving this accelerated expansion, the lack of understanding of the SN progenitor systems and the empirically derived standardization corrections represent severe limitations for SNe Ia as cosmological probes.
Cosmic dust
One astrophysical source of uncertainty in supernova observations comes from cosmic dust particles. Dust in the circumstellar (CS) environment of SNe, in the insterstellar medium of SN host galaxies and possibly even in the intergalactic medium have important implications for the observed colors and luminosities of SNe Ia; typically making them redder and fainter.
By measuring the wavelength dependence of the dust extinction from UV-to-IR observations and using other proxies for dust (such as Sodium absorption lines in high-resolution spectra) there is increasing evidence that some SNe show evidence for unusual dust. This, together with time-varying blue-shifted Sodium absorption, could indicate the presence of dust in the CS environment. Detecting or constraining the amounts of CS dust also has implications on the progenitor systems.
Highlights
Light rays from a supernova bent by the curvature of space-time around a galaxy
Together with a team led by Ariel Goobar at Stockholm University, we have detected for the first time multiple images from a gravitationally lensed Type Ia supernova.… Read more “Light rays from a supernova bent by the curvature of space-time around a galaxy”
A shocked neighbor?!
In a paper led by Yi Cao, we have a new exciting result! An early glimpse of ultraviolet light from a Type Ia supernova, iPTF14atg, reveals what… Read more “A shocked neighbor?!”
The Nearest Standard Candle Supernova in Several Decades
Supernova 2014J in the nearby galaxy Messier 82 (less than 12 million light-years away) exploded on January 14, 2014 and was the closest ”standard candle” supernova in… Read more “The Nearest Standard Candle Supernova in Several Decades”
Publications
Recent papers:
- A Uniform Type Ia Supernova Distance Ladder with the Zwicky Transient Facility: Absolute Calibration Based on the Tip of the Red Giant Branch (TRGB) Method
Dhawan, S.; Goobar, A.; Johansson, J. and 21 coauthors
eprint arXiv:2203.04241 (submitted)
- The Zwicky Transient Facility Type Ia supernova survey: first data release and results
Dhawan, S.; Goobar, A.; Smith, M.; Johansson, J. and 16 coauthors
Monthly Notices of the Royal Astronomical Society, Volume 510, Issue 2, pp.2228-2241
- Near-IR Type Ia SN distances: host galaxy extinction and mass-step corrections revisited
Johansson, J.; Cenko, S. B.; Fox, O. D; and 17 coauthors
The Astrophysical Journal, Volume 923, Issue 2, id.237, 15 pp.
- Microlensing and the type Ia supernova iPTF16geu
Diego, J.; Bernstein, G.; Chen, W.; Goobar, A.; Johansson, J.; Kelly, P. ; Mörtsell, E. ; Nightingale, J.
eprint arXiv:2112.04524 (accepted to A&A)
- The Hubble Tension Revisited: Additional Local Distance Ladder Uncertainties
Mörtsell, E.; Goobar, A.; Johansson, J.; and Dhawan, S.
eprint arXiv:2106.09400
- The Hubble Tension Bites the Dust: Sensitivity of the Hubble Constant Determination to Cepheid Color Calibration
Mörtsell, E.; Goobar, A.; Johansson, J.; and Dhawan, S.
eprint arXiv:2105.11461
- Spectroscopy of the first resolved strongly lensed Type Ia supernova iPTF16geu
Johansson, J.; Goobar, A.; Price, S. H.; and 14 coauthors
Monthly Notices of the Royal Astronomical Society, Volume 502, Issue 1, pp.510-520
- Lens modelling of the strongly lensed Type Ia supernova iPTF16geu
Mörtsell, E.; Johansson, J.; Dhawan, S.; Goobar, A.; Amanullah, R.; and 1 coauthor
Monthly Notices of the Royal Astronomical Society, Volume 496, Issue 3, pp.3270-3280
- Magnification, dust, and time-delay constraints from the first resolved strongly lensed Type Ia supernova iPTF16geu
Dhawan, S.; Johansson, J.; Goobar, A.; Amanullah, R.; Mörtsell, E.; and 12 coauthors
Monthly Notices of the Royal Astronomical Society, Volume 491, Issue 2, p.2639-2654