Measurements of Effective Optical Depth in the Lyα Forest from the BOSS DR12 Quasar Sample

Kamble, Vikrant; Dawson, Kyle; Bourboux, Hélion du Mas des; Bautista, Julian; Schneider, Donald P.

doi:10.3847/1538-4357/ab76bd

Cited by 9 publications

(8 citation statements)

References 68 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An error-weighted mean composite spectrum is constructed for all clusters using observer frame wavelengths longer than 3610.5 Å. Prior to averaging, pixels contaminated by sky emission are masked, all spectra are shifted to the rest-frame solution given by Z_PCA, and the spectra are corrected for galactic extinction and the effective optical depth of the Lyα forest using the model from Kamble et al (2020). All spectra are normalized over a wavelength range of 1500 to 2950 Å, which is common to all redshift bins.…”

Section: Composite Quasar Spectramentioning

confidence: 99%

Modeling the Spectral Diversity of Quasars in the Sixteenth Data Release from the Sloan Digital Sky Survey

Brodzeller,

Dawson

2021

Preprint

Self Cite

View full text Add to dashboard Cite

We present a new approach to capturing the broad diversity of emission line and continuum properties in quasar spectra. We identify populations of spectrally similar quasars through pixel-level clustering on 12,968 high signal-to-noise spectra from the Sloan Digital Sky Survey (SDSS) in the redshift range of 1.57 < z < 2.4. Our clustering analysis finds 396 quasar spectra that are not assigned to any population, 15 misclassified spectra, and six quasars with incorrect redshifts. We compress the quasar populations into a library of 684 high signal-to-noise composite spectra, anchored in redshift space by the Mg ii emission line. Principal component analysis on the library results in an eigenspectrum basis spanning 1067 to 4007 Å. We model independent samples of SDSS quasar spectra with the eigenbasis, allowing for a free redshift parameter. Our models achieve a median reduced chi-squared on non-BAL quasar spectra that is reduced by 8.5% relative to models using the eigenspectra from the SDSS spectroscopic pipeline. A significant contribution to the relative improvement is from the ability to reconstruct the range of emission line variation. The redshift estimates from our model are consistent with the Mg ii emission line redshift with an average offset that displays 51.4% less redshift-dependent variation relative to the SDSS eigenspectra. Our method for developing quasar spectra models can improve automated classification and predict the intrinsic spectrum in regions affected by intervening absorbers such as Lyα, C iv, and Mg ii, thus benefiting studies of large-scale structure.

show abstract

Section: Composite Quasar Spectramentioning

confidence: 99%

Modeling the Spectral Diversity of Quasars in the Sixteenth Data Release from the Sloan Digital Sky Survey

Brodzeller,

Dawson

2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The parameters of this matrix follow the values given in Kamble et al (2020), which used a power-law relation to measure the effective optical depth in the Lyman-α forest in SDSS DR12:…”

Section: Learning the Gp Null Modelmentioning

confidence: 99%

“…In Ho et al (2020), we only took the mean values of the meanflux parameters (βMF, τ0,MF) without their uncertainties, so the model evidence straightforwardly equals to Eq 14 without integration. In this work, we take the uncertainties of meanflux suppression into account and integrate them out, according to Kamble et al (2020) prior. The model evidence thus will be:…”

Section: Model Evidence For the Null Modelmentioning

confidence: 99%

“…where we assign the Kamble et al (2020) prior for the meanflux parameters as in Eq 17. We use the same prior for column density, p(NHI | MDLA), as Ho et al (2020).…”

Section: Model Evidence For the Dla Modelmentioning

confidence: 99%

“…(iii) The effective optical depth prior, (τ0, β), is updated from Kim et al (2007) to Kamble et al (2020).…”

Section: Summary Of the Modificationsmentioning

confidence: 99%

See 2 more Smart Citations

Damped Lyman-alpha Absorbers from Sloan Digital Sky Survey DR16Q with Gaussian processes

Ho,

Bird,

Garnett

2021

Preprint

View full text Add to dashboard Cite

We present a new catalogue of Damped Lyman-α absorbers from SDSS DR16Q, as well as new estimates of their statistical properties. Our estimates are computed with the Gaussian process models presented in Garnett et al. (2017); Ho et al. ( 2020) with an improved model for marginalising uncertainty in the mean optical depth of each quasar. We compute the column density distribution function (CDDF) at 2 < z < 5, the line density (dN/dX), and the neutral hydrogen density (Ω DLA ). Our Gaussian process model provides a posterior probability distribution of the number of DLAs per spectrum, thus allowing unbiased probabilistic predictions of the statistics of DLA populations even with the noisiest data. We measure a non-zero column density distribution function for N HI < 3 × 10 22 cm −2 with 95% confidence limits. Our results for DLA line density and total hydrogen density are consistent with previous measurements. Despite a small bias due to the poorly measured blue edges of the spectra, we demonstrate that our new model can measure the DLA population statistics when the DLA is in the Lyman-β forest region. We verify our results are not sensitive to the signal-to-noise ratios and redshifts of the background quasars although a residual correlation remains for detections from z QSO < 2.5, indicating some residual systematics when applying our models on very short spectra, where the SDSS spectral observing window only covers part of the Lyman-α forest.

show abstract

Using the redshift evolution of the Lyman-α effective opacity as a probe of dark matter models

Sarkar

Pandey

Sethi

2021

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

Lyman-α forest data are known to be a good probe of the small scale matter power. In this paper, we explore the redshift evolution of the observable effective optical depth τeff (z) from the Lyman-α data as a discriminator between dark matter models that differ from the ΛCDM model on small scales. We consider the thermal warm dark matter (WDM) and the ultra-light axion (ULA) models for the following set of parameters: the mass of ULA, ma ≃ 10-24–5 × 10-22 eV and WDM mass, m_ wdm = 0.1 – 4.6 keV. We simulate the line-of-sight HI density and velocity fields using semi-analytic methods. The simulated effective optical depth for the alternative dark matter models diverges from the ΛCDM model for z ≳ 3, which provides a meaningful probe of the matter power at small scales. Using likelihood analysis, we compare the simulated data with the high-resolution Lyman-α forest data in the redshift range 2 < z < 4.2. The analysis yields the following 1σ bounds on dark matter masses: m_ wdm > 0.7 keV and m_ a > 2 × 10-23 eV. To further test the efficacy of our proposed method, we simulate synthetic data sets compatible with the ΛCDM model in the redshift range 2 ≤ z ≤ 6.5 and compare with theory. The 1σ bounds obtained are significantly tighter: m_ wdm > 1.5 keV and m_ a > 7 × 10-23 eV. Although our method provides an alternative way of constraining dark matter models, we note that these bounds are weaker than those obtained by high-resolution hydrodynamical simulations.

show abstract

Measurements of Effective Optical Depth in the Lyα Forest from the BOSS DR12 Quasar Sample

Cited by 9 publications

References 68 publications

Modeling the Spectral Diversity of Quasars in the Sixteenth Data Release from the Sloan Digital Sky Survey

Modeling the Spectral Diversity of Quasars in the Sixteenth Data Release from the Sloan Digital Sky Survey

Damped Lyman-alpha Absorbers from Sloan Digital Sky Survey DR16Q with Gaussian processes

Using the redshift evolution of the Lyman-α effective opacity as a probe of dark matter models

Contact Info

Product

Resources

About