Atomic Hydrogen in the Milky Way: A Stepping Stone in the Evolution of Galaxies

McClure-Griffiths, N. M.; Stanimirović, Snežana; Rybarczyk, Daniel R.

doi:10.1146/annurev-astro-052920-104851

Cited by 11 publications

(12 citation statements)

References 267 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this work, we revisit the Crovisier (1978) analysis in preparation for its application to the ever-growing sample of H I absorption spectra (e.g., HIBIGCAT; McClure-Griffiths et al 2023) and next-generation H I surveys (e.g., GASKAP; Dickey et al 2013). In particular, we discover a statistical bias that alters the interpretation of the Crovisier (1978) result, which we demonstrate through both a simple simulation as well as a robust derivation.…”

Section: Introductionmentioning

confidence: 90%

“…These results are consistent with the Dickey et al (2022) inference at R 0 in the fourth Galactic quadrant. Altogether, we begin to develop a clear picture of a vertical CNM distribution that is thin in the inner Galaxy, mimicking the molecular gas distribution, and slowly flares with Galactocentric distance (e.g., see Section 6.4.2. and Figure 10 in McClure-Griffiths et al 2023).…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Revisiting the Vertical Distribution of H i Absorbing Clouds in the Solar Neighborhood

Wenger,

Rybarczyk,

Stanimirović

2024

ApJ

Self Cite

View full text Add to dashboard Cite

The vertical distribution of cold neutral hydrogen (H i) clouds is a constraint on models of the structure, dynamics, and hydrostatic balance of the interstellar medium. In 1978, Crovisier pioneered a method to infer the vertical distribution of H i absorbing clouds in the solar neighborhood. Using data from the Nançay 21 cm absorption survey, Crovisier determined the mean vertical displacement of cold H i clouds, 〈∣z∣〉. We revisit that author’s analysis and explore the consequences of truncating the H i absorption sample in Galactic latitude. For any nonzero latitude limit, we find that the quantity inferred by Crovisier is not the mean vertical displacement but rather a ratio involving higher moments of the vertical distribution. The resultant distribution scale heights are thus ∼1.5 to ∼3 times smaller than previously determined. In light of this discovery, we develop a Bayesian Monte Carlo Markov Chain method to infer the vertical distribution of H i absorbing clouds. We fit our model to the original Nançay data and find a vertical distribution moment ratio 〈∣z∣3〉/〈∣z∣2〉 = 97 ± 15 pc, which corresponds to a Gaussian scale height σ z = 61 ± 9 pc, an exponential scale height λ z = 32 ± 5 pc, and a rectangular half-width W z,1/2 = 129 ± 20 pc. Consistent with recent simulations, the vertical scale height of cold H i clouds appears to remain constant between the inner Galaxy and the Galactocentric distance of the solar neighborhood. Local fluctuations might explain the large-scale height observed at the same Galactocentric distance on the far side of the Galaxy.

show abstract

Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 98%

Revisiting the Vertical Distribution of H i Absorbing Clouds in the Solar Neighborhood

Wenger,

Rybarczyk,

Stanimirović

2024

ApJ

Self Cite

View full text Add to dashboard Cite

show abstract

“…in units of K, σ = 3 km s −1 corresponds to gas with a maximum Kinetic temperature of approximately 1000 K. In reality, accounting for turbulent broadening, T k is probably much less. This can be assessed by looking at the data in the BIGHICAT meta-catalog compiled by McClure-Griffiths et al (2023;Section 4.4). Figure 8 shows a histogram of σ for all Gaussian components identified in absorption with closely matching profiles in emission.…”

Section: A Lower Limit On the Cold Gas Mass Fractionmentioning

confidence: 99%

“…We extended the comparison made with 21-SPONGE to the 373 unique lines of sight in the BIGHICAT meta-catalog compiled by McClure-Griffiths et al (2023).…”

Section: Bighicatmentioning

confidence: 99%

Mapping a Lower Limit on the Mass Fraction of the Cold Neutral Medium Using Fourier-transformed H i 21 cm Emission Line Spectra: Application to the DRAO Deep Field from DHIGLS and the HI4PI Survey

Marchal,

Martin,

Miville-Deschênes

et al. 2024

ApJ

Self Cite

View full text Add to dashboard Cite

We develop a new method for spatially mapping a lower limit on the mass fraction of the cold neutral medium by analyzing the amplitude structure of T ˆ b ( k v ) , the Fourier transform of T b (v), the spectrum of the brightness temperature of the H i 21 cm line emission with respect to the radial velocity v. This advances a broader effort exploiting 21 cm emission line data alone (without absorption line data, τ) to extract integrated properties of the multiphase structure of the H i gas and to map each phase separately. Using toy models, we illustrate the origin of interference patterns seen in T ˆ b ( k v ) . Building on this, a lower limit on the cold gas mass fraction is obtained from the amplitude of T ˆ b at high k v . Tested on a numerical simulation of thermally bi-stable turbulence, the lower limit from this method has a strong linear correlation with the “true” cold gas mass fraction from the simulation for a relatively low cold gas mass fraction. At a higher mass fraction, our lower limit is lower than the “true” value, because of a combination of interference and opacity effects. Comparison with absorption surveys shows a similar behavior, with a departure from linear correlation at N H I ≳ 3–5 × 1020 cm−2. Application to the DRAO Deep Field from DHIGLS reveals a complex network of cold filaments in the Spider, an important structural property of the thermal condensation of the H i gas. Application to the HI4PI survey in the velocity range −90 < v < 90 km s−1 produces a full sky map of a lower limit on the mass fraction of the cold neutral medium at 16.′2 resolution. Our new method has the ability to extract a lower limit on the cold gas mass fraction for massive amounts of emission line data alone with low computing time and memory, pointing the way to new approaches suitable for the new generation of radio interferometers.

show abstract

“…Dust plays an important role in the interstellar medium (ISM): it is a powerful catalyst for astrochemistry, it is the dominant source of opacity at optical wavelengths, and it couples neutral gas to magnetic fields (Draine 2011;Saintonge & Catinella 2022;McClure-Griffiths et al 2023). However, the detailed life cycle of dust grains in the ISM is not yet understood, nor do we fully know how the properties of dust vary across different phases of the ISM.…”

Section: Introductionmentioning

confidence: 99%

All We Are Is Dust in the WIM: Constraints on Dust Properties in the Milky Way’s Warm Ionized Medium

West,

Gaensler,

Miville-Deschênes

et al. 2023

ApJ

View full text Add to dashboard Cite

We present a comparison of the presence and properties of dust in two distinct phases of the Milky Way’s interstellar medium: the warm neutral medium (WNM) and the warm ionized medium (WIM). Using distant pulsars at high Galactic latitudes and vertical distance (∣b∣ > 40°, D sin ∣ b ∣ > 2 kpc ) as probes, we measure their dispersion measures and the neutral hydrogen component of the warm neutral medium (WNMH I) using H i column density. Together with dust intensity along these same sightlines, we separate the respective dust contributions of each ISM phase in order to determine whether the ionized component contributes to the dust signal. We measure the temperature (T), spectral index (β), and dust opacity (τ/N H) in both phases. We find T ( WNM H I ) = 20 − 2 + 3 K, β (WNMH I) = 1.5 ± 0.4, and τ 353/N H (WNMH I) = (1.0 ± 0.1) × 10−26 cm2. Assuming that the temperature and spectral index are the same in both the WNMH I and WIM, and given our simple model that widely separated lines of sight can be fit together, we find evidence that there is a dust signal associated with the ionized gas and τ 353 / N H ( WIM ) = ( 0.3 ± 0.3 ) × 10 − 26 , which is about 3 times smaller than τ 353/N H (WNMH I). We are 80% confident that τ 353 / N H ( WIM ) is at least 2 times smaller than τ 353/N H (WNMH I).

show abstract

Atomic Hydrogen in the Milky Way: A Stepping Stone in the Evolution of Galaxies

Cited by 11 publications

References 267 publications

Revisiting the Vertical Distribution of H i Absorbing Clouds in the Solar Neighborhood

Revisiting the Vertical Distribution of H i Absorbing Clouds in the Solar Neighborhood

Mapping a Lower Limit on the Mass Fraction of the Cold Neutral Medium Using Fourier-transformed H i 21 cm Emission Line Spectra: Application to the DRAO Deep Field from DHIGLS and the HI4PI Survey

All We Are Is Dust in the WIM: Constraints on Dust Properties in the Milky Way’s Warm Ionized Medium

Contact Info

Product

Resources

About