Corrected SFD: A More Accurate Galactic Dust Map with Minimal Extragalactic Contamination

Chiang, Yi-Kuan

doi:10.3847/1538-4357/acf4a1

Cited by 6 publications

(3 citation statements)

References 63 publications

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“…For example, Lenz et al (2017) compared the Schlegel et al (1998) maps with H 1 data (HI4PI Collaboration 2016) to derive the reddening E(B − V). This technique of modeling involves uncertainties relating to two factors: i) the gas-to-dust ratio, which may exhibit variations across the sky (Shull & Panopoulou 2024;Skalidis et al 2024), and ii) the dust modeling, which results in important differences at high latitudes (Chiang & Ménard 2019;Chiang 2023). Characteristic evidence for the high uncertainties in the dust maps is revealed by the differences between maps, especially at high latitudes.…”

Section: Discussionmentioning

confidence: 99%

Zero-polarization candidate regions for the calibration of wide-field optical polarimeters

Mandarakas,

Panopoulou,

Pelgrims

et al. 2024

A&A

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The calibration of optical polarimeters relies on the use of stars with negligible polarization (i.e., unpolarized standard stars) for determining the instrumental polarization zero point. For wide-field polarimeters, calibration is often done by imaging the same star over multiple positions in the field of view (FoV), which is a time-consuming process. A more effective technique is to target fields containing multiple standard stars. While this method has been used for fields with highly polarized stars, there are no such sky regions with well measured unpolarized standard stars. We aim to identify sky regions with tens of stars exhibiting negligible polarization that are suitable for a zero-point calibration of wide-field polarimeters. We selected stars in regions with extremely low reddening, located at high Galactic latitudes. We targeted four $ 40'$ fields in the northern and eight in the southern equatorial hemispheres. Observations were carried out at the Skinakas Observatory and the South African Astronomical Observatory. We found two fields in the north and seven in the south characterized by a mean polarization lower than $p<0.1<!PCT!>$. At least 9 out of the 12 fields can be used for a zero-point calibration of wide-field polarimeters.

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Section: Discussionmentioning

confidence: 99%

Zero-polarization candidate regions for the calibration of wide-field optical polarimeters

Mandarakas,

Panopoulou,

Pelgrims

et al. 2024

A&A

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“…The systematics maps (templates) we use are shown in Figure 8. We use the dust map of Chiang (2023), and convert it to a healpix map of NSIDE = 64. To do this, we evaluate the reddening E(B − V ) at the centers of pixels of a high-resolution NSIDE = 2048 healpixelization of the sphere, and apply the 0.86 correction factor proposed by Schlafly & Finkbeiner (2011).…”

Section: Selection Function Modelingmentioning

confidence: 99%

Quaia, the Gaia-unWISE Quasar Catalog: An All-sky Spectroscopic Quasar Sample

Storey-Fisher,

Hogg,

Rix

et al. 2024

ApJ

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We present a new, all-sky quasar catalog, Quaia, that samples the largest comoving volume of any existing spectroscopic quasar sample. The catalog draws on the 6,649,162 quasar candidates identified by the Gaia mission that have redshift estimates from the space observatory’s low-resolution blue photometer/red photometer spectra. This initial sample is highly homogeneous and complete, but has low purity, and 18% of even the bright (G < 20.0) confirmed quasars have discrepant redshift estimates (∣Δz/(1 + z)∣ > 0.2) compared to those from the Sloan Digital Sky Survey (SDSS). In this work, we combine the Gaia candidates with unWISE infrared data (based on the Wide-field Infrared Survey Explorer survey) to construct a catalog useful for cosmological and astrophysical quasar studies. We apply cuts based on proper motions and colors, reducing the number of contaminants by approximately four times. We improve the redshifts by training a k-Nearest Neighbor model on SDSS redshifts, and achieve estimates on the G < 20.0 sample with only 6% (10%) catastrophic errors with ∣Δz/(1 + z)∣ > 0.2 (0.1), a reduction of approximately three times (approximately two times) compared to the Gaia redshifts. The final catalog has 1,295,502 quasars with G < 20.5, and 755,850 candidates in an even cleaner G < 20.0 sample, with accompanying rigorous selection function models. We compare Quaia to existing quasar catalogs, showing that its large effective volume makes it a highly competitive sample for cosmological large-scale structure analyses. The catalog is publicly available at 10.5281/zenodo.10403370.

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“…The 0.86 factor is less than the conversion factor described in Section 2.2.1 ofLenz et al (2017), where 0.884 is for the Landolt V filter, and 0.865 is for the CTIO V filter Lenz et al (2017). also noted a mean ratio N H I /E(B − V ) = 8.2, using pixels in a revised reddening map(Schlafly et al 2014) based on Pan-STARRS1 optical photometry of 500 million stars.5 The map is provided on lambda.gsfc.nasa.gov byChiang (2023).…”

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confidence: 99%

Variations of Interstellar Gas-to-dust Ratios at High Galactic Latitudes

Shull,

Panopoulou

2024

ApJ

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Interstellar dust at high Galactic latitudes can influence astronomical foreground subtraction, produce diffuse scattered light, and soften the UV spectra of quasars. In a sample of 94 sight lines toward quasars at high latitude and low extinction, we evaluate the interstellar “gas-to-dust ratio” N H/E(B − V), using hydrogen column densities (H i and H2) and far-IR (FIR) estimates of dust reddening. In the Galactic plane, this ratio is 6.0 ± 0.2 (in units of 1021 cm−2 mag−1). On average, recent Planck estimates of E(B − V) in low-reddening sight lines are 12% higher than those from Schlafly & Finkbeiner, and N H I exhibits significant variations when measured at different radio telescopes. In a sample of 51 quasars with measurements of both H i and H2 and 0.01 ≤ E(B − V) ≲ 0.1, we find mean ratios 10.3 ± 0.4 (gas at all velocities) and 9.2 ± 0.3 (low-velocity only) using Planck E(B − V) data. High-latitude H2 fractions are generally small (2%–3% on average), although nine of 39 sight lines at ∣b∣ ≥ 40° have f H2 of 1%–17%. Because FIR-inferred E(B − V) is sensitive to modeled dust temperature T d and emissivity index β, gas-to-dust ratios have large, asymmetric errors at low E(B − V). The ratios are elevated in sight lines with high-velocity clouds, which contribute N H but little reddening. In Complex C, the ratio decreases by 40% when high-velocity gas is excluded. Decreases in dust content are expected in low-metallicity gas above the Galactic plane, resulting from grain destruction in shocks, settling to the disk, and thermal sputtering in hot halo gas.

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Corrected SFD: A More Accurate Galactic Dust Map with Minimal Extragalactic Contamination

Cited by 6 publications

References 63 publications

Zero-polarization candidate regions for the calibration of wide-field optical polarimeters

Zero-polarization candidate regions for the calibration of wide-field optical polarimeters

Quaia, the Gaia-unWISE Quasar Catalog: An All-sky Spectroscopic Quasar Sample

Variations of Interstellar Gas-to-dust Ratios at High Galactic Latitudes

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