Lizelke Klindt - Academia.edu (original) (raw)
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Papers by Lizelke Klindt
Proceedings of Frontier Research in Astrophysics — PoS(FRAPWS2014), 2016
Proceedings of SALT Science Conference 2015 — PoS(SSC2015), 2016
The Astrophysical Journal, 2022
The observed optical colors of quasars are generally interpreted in one of two frameworks: unifie... more The observed optical colors of quasars are generally interpreted in one of two frameworks: unified models that attribute the color to the random orientation of the accretion disk along the line of sight, and evolutionary models that invoke connections between quasar systems and their environments. We test these schemas by probing the dark matter halo environments of optically selected quasars as a function of g − i optical color by measuring the two-point correlation functions of ∼0.34 million eBOSS quasars as well as the gravitational deflection of cosmic microwave background photons around ∼0.66 million XDQSO photometric quasar candidates. We do not detect a trend of halo bias with optical color through either analysis, finding that optically selected quasars at 0.8 < z < 2.2 occupy halos of characteristic mass M h ∼ 3 × 1012 h −1 M ⊙ regardless of their color. This result implies that a quasar’s large-scale halo environment is not strongly connected to its observed optical ...
Certain selection criteria have been applied to sources listed in the Fermi-2LAC catalogue in ord... more Certain selection criteria have been applied to sources listed in the Fermi-2LAC catalogue in order to construct a target sample of twenty unidentified sources at high galactic latitudes with possible blazar characteristics. Blazars constitute the most violent and active astronomical objects which emit radiation at all wavelengths. Therefore multi-wavelength analysis provides the opportunity to construct a Spectral Energy Distribution (SED), which will allow the identification and modelling of the candidate sources. Preliminary spectroscopic results yield spectra of four observed targets which resemble that of BL Lac or flat spectrum radio quasars (FSRQs) with optical counterparts. Estimated redshifts are obtained within the range 0.11 < z < 0.37. Potential Ca II H&K, MgIb and/or NaD spectral lines have been detected in the spectra of four targets, which motivates further observations in order to identify spectral lines that are possibly present.
A non-negligible fraction of quasars are red at optical wavelengths, indicating (in the vast majo... more A non-negligible fraction of quasars are red at optical wavelengths, indicating (in the vast majority of cases) that the accretion disc is obscured by a column of dust which extinguishes the shorter-wavelength blue emission. In this paper we summarise recent work by our group, where we find fundamental differences in the radio properties of SDSS optically selected red quasars. We also present new analyses, using a consistent colour-selected quasar parent sample matched to four radio surveys (FIRST, VLA Stripe 82, VLA COSMOS 3 GHz and LoTSS DR1) across a frequency range 150 MHz-3 GHz and four orders of magnitude in radio flux. We show this enhancement is driven by systems with small-scale radio emission (∼kpc) and peaks around the radio-quiet threshold (defined as the ratio of 1.4 GHz luminosity to 6μm luminosity) across the four radio samples. Exploring the potential mechanisms behind this enhancement, we rule out star-formation and propose either small-scale jets or dusty winds int...
Monthly Notices of the Royal Astronomical Society, 2020
Red quasi-stellar objects (QSOs) are a subset of the luminous end of the cosmic population of act... more Red quasi-stellar objects (QSOs) are a subset of the luminous end of the cosmic population of active galactic nuclei (AGNs), most of which are reddened by intervening dust along the line of sight towards their central engines. In recent work from our team, we developed a systematic technique to select red QSOs from the Sloan Digital Sky Survey, and demonstrated that they have distinctive radio properties using the Faint Images of the Radio Sky at Twenty centimetres radio survey. Here we expand our study using low-frequency radio data from the LOFAR Two-metre Sky Survey (LoTSS). With the improvement in depth that LoTSS offers, we confirm key results: Compared to a control sample of normal ‘blue’ QSOs matched in redshift and accretion power, red QSOs have a higher radio detection rate and a higher incidence of compact radio morphologies. For the first time, we also demonstrate that these differences arise primarily in sources of intermediate radio loudness: Radio-intermediate red QSOs...
Proceedings of SALT Science Conference 2015 — PoS(SSC2015), 2016
Proceedings of 3rd Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2015), 2016
The Astrophysical Journal, 2018
Proceedings of Frontier Research in Astrophysics – II — PoS(FRAPWS2016), 2017
Proceedings of 4th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA 2016), 2017
Proceedings of Frontier Research in Astrophysics — PoS(FRAPWS2014), 2016
Proceedings of SALT Science Conference 2015 — PoS(SSC2015), 2016
The Astrophysical Journal, 2022
The observed optical colors of quasars are generally interpreted in one of two frameworks: unifie... more The observed optical colors of quasars are generally interpreted in one of two frameworks: unified models that attribute the color to the random orientation of the accretion disk along the line of sight, and evolutionary models that invoke connections between quasar systems and their environments. We test these schemas by probing the dark matter halo environments of optically selected quasars as a function of g − i optical color by measuring the two-point correlation functions of ∼0.34 million eBOSS quasars as well as the gravitational deflection of cosmic microwave background photons around ∼0.66 million XDQSO photometric quasar candidates. We do not detect a trend of halo bias with optical color through either analysis, finding that optically selected quasars at 0.8 < z < 2.2 occupy halos of characteristic mass M h ∼ 3 × 1012 h −1 M ⊙ regardless of their color. This result implies that a quasar’s large-scale halo environment is not strongly connected to its observed optical ...
Certain selection criteria have been applied to sources listed in the Fermi-2LAC catalogue in ord... more Certain selection criteria have been applied to sources listed in the Fermi-2LAC catalogue in order to construct a target sample of twenty unidentified sources at high galactic latitudes with possible blazar characteristics. Blazars constitute the most violent and active astronomical objects which emit radiation at all wavelengths. Therefore multi-wavelength analysis provides the opportunity to construct a Spectral Energy Distribution (SED), which will allow the identification and modelling of the candidate sources. Preliminary spectroscopic results yield spectra of four observed targets which resemble that of BL Lac or flat spectrum radio quasars (FSRQs) with optical counterparts. Estimated redshifts are obtained within the range 0.11 < z < 0.37. Potential Ca II H&K, MgIb and/or NaD spectral lines have been detected in the spectra of four targets, which motivates further observations in order to identify spectral lines that are possibly present.
A non-negligible fraction of quasars are red at optical wavelengths, indicating (in the vast majo... more A non-negligible fraction of quasars are red at optical wavelengths, indicating (in the vast majority of cases) that the accretion disc is obscured by a column of dust which extinguishes the shorter-wavelength blue emission. In this paper we summarise recent work by our group, where we find fundamental differences in the radio properties of SDSS optically selected red quasars. We also present new analyses, using a consistent colour-selected quasar parent sample matched to four radio surveys (FIRST, VLA Stripe 82, VLA COSMOS 3 GHz and LoTSS DR1) across a frequency range 150 MHz-3 GHz and four orders of magnitude in radio flux. We show this enhancement is driven by systems with small-scale radio emission (∼kpc) and peaks around the radio-quiet threshold (defined as the ratio of 1.4 GHz luminosity to 6μm luminosity) across the four radio samples. Exploring the potential mechanisms behind this enhancement, we rule out star-formation and propose either small-scale jets or dusty winds int...
Monthly Notices of the Royal Astronomical Society, 2020
Red quasi-stellar objects (QSOs) are a subset of the luminous end of the cosmic population of act... more Red quasi-stellar objects (QSOs) are a subset of the luminous end of the cosmic population of active galactic nuclei (AGNs), most of which are reddened by intervening dust along the line of sight towards their central engines. In recent work from our team, we developed a systematic technique to select red QSOs from the Sloan Digital Sky Survey, and demonstrated that they have distinctive radio properties using the Faint Images of the Radio Sky at Twenty centimetres radio survey. Here we expand our study using low-frequency radio data from the LOFAR Two-metre Sky Survey (LoTSS). With the improvement in depth that LoTSS offers, we confirm key results: Compared to a control sample of normal ‘blue’ QSOs matched in redshift and accretion power, red QSOs have a higher radio detection rate and a higher incidence of compact radio morphologies. For the first time, we also demonstrate that these differences arise primarily in sources of intermediate radio loudness: Radio-intermediate red QSOs...
Proceedings of SALT Science Conference 2015 — PoS(SSC2015), 2016
Proceedings of 3rd Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2015), 2016
The Astrophysical Journal, 2018
Proceedings of Frontier Research in Astrophysics – II — PoS(FRAPWS2016), 2017
Proceedings of 4th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA 2016), 2017