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HI emission as a tracer of interstellar reddening

Daniel
July 19, 2017

HI emission as a tracer of interstellar reddening

I presented our new, HI-based extinction map at the 'Advances in Theoretical Cosmology in Light of Data' conference at Nordita, Sweden.

Daniel

July 19, 2017
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  1. HI emission as a tracer of interstellar reddening in collaboration

    with B. Hensley & O. Doré arXiv:1706.00011 Daniel Lenz Advances in Theoretical Cosmology in Light of Data July 19 © 2017 California Institute of Technology. Government sponsorship acknowledged.
  2. Which foregrounds do we care about? "(…) the name of

    the game is component separation, not noise reduction" H.K. Eriksen ❖ Dust and synchrotron foregrounds in CMB data ❖ De-lensing of CMB data for primordial gravitational waves ❖ CIB measurements ❖ Extinction for cosmological galaxy surveys Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map 2
  3. Reddening

  4. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map E(B-V) ❖

    E(B-V) = Extinction in B band - Extinction in V band ❖ More dust => larger E(B-V) ❖ E(B-V) maps essential for correcting observations for Galactic reddening 4
  5. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map Mapping E(B-V):

    Direct approach ❖ Find many sources with known spectrum (e.g. stars, passive galaxies) ❖ Measure spectra, attribute differences to dust ❖ E.g. Schlafly+ 2014 used 500 million stars from Pan-STARRS to measure reddening to 4.5 kpc ❖ Direct measurements are hard! ❖ Photometric/ spectroscopic errors ❖ Ensuring sources lie behind full dust column ❖ Ensuring adequate number of sources have been measured 5
  6. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map Dust emission

    as measure of E(B-V) ❖ E(B-V) is proportional to the dust column, so can convert dust column tracer to E(B-V) ❖ SFD used dust emission from IRAS to derive a calibration factor from FIR emission to E(B-V) ❖ Full-sky, high sensitivity measurements -2 -0.3 log10 (E(B V )SFD [mag]) Reddening map of Schlegel, Finkbeiner, and Davis (1998) 6
  7. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map The SFD

    reddening map ❖ Requires a temperature correction to go from dust emission to a dust column density ❖ FIR emission may have contributions from Zodiacal Light and unresolved galaxies -2 -0.3 log10 (E(B V )SFD [mag]) Reddening map of Schlegel, Finkbeiner, and Davis (1998) 7
  8. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map The SFD

    reddening map ❖ Requires a temperature correction to go from dust emission to a dust column density ❖ FIR emission may have contributions from Zodiacal Light and unresolved galaxies -2 -0.3 log10 (E(B V )SFD [mag]) Reddening map of Schlegel, Finkbeiner, and Davis (1998) 7
  9. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map HI emission

    as basis for E(B-V) ❖ Gas and dust are well-coupled in the ISM ❖ Perform an SFD-like analysis to convert HI emission to E(B-V) ❖ Resulting maps free from errors due to dust temperature, Zodi, and extragalactic emission ❖ Limited by non-HI gas along the line of sight 8
  10. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map HI4PI Survey

    ❖ Merges data from Effelsberg and Parkes ❖ Replaces LAB as state-of-the-art full-sky HI survey ❖ Higher sensitivity & resolution, fewer systematics, full sampling 20 21 22 log(NHI [cm 2]) 180 135 90 45 0 315 270 225 180 60 30 0 30 60 HI4PI collaboration
 (2017) 9
  11. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map 1020 1021

    1022 NHI [cm 2] 10 3 10 2 10 1 100 E(B V ) [mag] 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 NHI [cm 2] ⇥1020 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 E(B V ) [mag] E(B V ) [mag] = 1.216+0.009 0.009 ⇥ NHI [1022 cm 2] + 0.015+0.0002 0.0002 [mag] = 0.02406+0.00006 0.00006 100 101 102 103 104 # data points 0 10 20 30 40 50 60 70 80 # data points 1020 1021 1022 NHI [cm 2] 10 3 10 2 10 1 100 E(B V ) [mag] 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 NHI [cm 2] ⇥1020 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 E(B V ) [mag] E(B V ) [mag] = 1.113+0.002 0.002 ⇥ NHI [1022 cm 2] + 0.000+0.0001 0.0001 [mag] = 0.00570+0.00001 0.00001 100 101 102 103 104 # data points 0 100 200 300 400 # data points The E(B-V)/NHI ratio Pan-STARRS E(B-V), Schlafly+ (2014) SFD E(B-V) Star-based Dust-based 10
  12. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map 1020 1021

    1022 NHI [cm 2] 10 3 10 2 10 1 100 E(B V ) [mag] 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 NHI [cm 2] ⇥1020 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 E(B V ) [mag] E(B V ) [mag] = 1.216+0.009 0.009 ⇥ NHI [1022 cm 2] + 0.015+0.0002 0.0002 [mag] = 0.02406+0.00006 0.00006 100 101 102 103 104 # data points 0 10 20 30 40 50 60 70 80 # data points 1020 1021 1022 NHI [cm 2] 10 3 10 2 10 1 100 E(B V ) [mag] 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 NHI [cm 2] ⇥1020 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 E(B V ) [mag] E(B V ) [mag] = 1.113+0.002 0.002 ⇥ NHI [1022 cm 2] + 0.000+0.0001 0.0001 [mag] = 0.00570+0.00001 0.00001 100 101 102 103 104 # data points 0 100 200 300 400 # data points The E(B-V)/NHI ratio Pan-STARRS E(B-V), Schlafly+ (2014) SFD E(B-V) Star-based Dust-based 10
  13. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map 0 0.05

    E(B V )model [mag] The E(B-V) map 40% sky coverage, 16.1’ resolution Lenz, Hensley, Doré (2017, submitted) 11
  14. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map -0.01 0.01

    SFD - PG10 [mag] Dust systematics ❖ Peek & Graves (2010) used SDSS passively evolving galaxies as "standard crayons" ❖ Correction to the SFD map at 4.5 deg 12
  15. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map Dust systematics

    -0.01 0.01 SFD - PG10 [mag] -0.01 0.01 SFD - Model [mag] 13 Based on extragalactic sources Based on galactic HI
  16. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map HI systematics

    20 40 60 80 |b| [deg] 0.04 0.02 0.00 0.02 0.04 SFD Model [mag] 100 101 102 103 104 105 # data points 1 2 3 4 NHI [1020 cm 2] 0.04 0.02 0.00 0.02 0.04 SFD Model [mag] 100 101 102 103 104 105 # data points 14 Investigate systematics due to complex ISM physics
  17. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map Model extensions

    ❖ Several large-scale data sets available, all of which do not significantly improve the model ❖ A future work would need to combine multiphase gaseous data, FIR dust data, and Pan- STARRS/Gaia data 0.5 1.0 1.5 2.0 WCO [K km s 1] 0.04 0.02 0.00 0.02 0.04 SFD Model [mag] 0.5 1.0 1.5 2.0 2.5 3.0 SCII [nW m 2 sr 1] 0.04 0.02 0.00 0.02 0.04 SFD Model [mag] 1 2 3 4 H↵ [Rayleighs] 0.04 0.02 0.00 0.02 0.04 SFD Model [mag] 100 101 102 103 104 105 # data points 15
  18. Daniel Lenz, Caltech/JPL An improved, unbiased E(B-V) map When and

    why to use this extinction map ❖ New HI based extinction map ❖ In line with independent corrections, but much higher resolution and better sky coverage ❖ Yahata+ (2007) find correlation of SFD with large-scale structure ❖ For high latitudes, our map overcomes many of the SFD problems and is much more sensitive than stellar data- based E(B-V) maps 16