Ultraviolet Halos Around Spiral Galaxies. I. Morphology

Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N.

doi:10.3847/1538-4357/833/1/58

Cited by 27 publications

(28 citation statements)

References 75 publications

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“…Moreover, we note that the diffuse eDust that scatters the UV starlight from the midplane (Hodges-Kluck & Bregman 2014;Seon et al 2014;Shinn & Seon 2015;Hodges-Kluck et al 2016) and produces the UV reflection halo has a potential to scatter the Hα photons originating from H II regions in the galactic plane. Ferrara et al (1996) investigated the amount of Hα photons that originates in H II regions and scattered by dust at high altitude and found that ∼ 10% of the extraplanar Hα emission at z ∼ 600 pc can be attributed to the scattered light (see also Wood & Reynolds (1999) for a similar model in the Milky Way Galaxy).…”

Section: Introductionmentioning

confidence: 93%

“…Many studies in the mid-infrared (MIR) and far-IR (FIR) wavelengths have provided evidence of eDust (Alton et al 2000a,b;Irwin & Madden 2006;Burgdorf et al 2007;Kaneda et al 2009;Verstappen et al 2013;Bocchio et al 2016). Far-ultraviolet (FUV) and/or near-UV (NUV) observations of edge-on galaxies have revealed the stellar continuum scattered into the line of sight by the eDust (Seon et al 2014;Hodges-Kluck & Bregman 2014;Shinn & Seon 2015;Hodges-Kluck et al 2016). The FUV emission in the galactic outflows of starburst galaxies were also attributed to starlight scattered by dust in the outflow (Hoopes et al 2005).…”

Section: Introductionmentioning

confidence: 99%

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Comparison of the Extraplanar Hα and UV Emissions in the Halos of Nearby Edge-on Spiral Galaxies

Seon

Shinn

et al. 2018

ApJ

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We compare vertical profiles of the extraplanar Hα emission to those of the UV emission for 38 nearby edge-on late-type galaxies. It is found that detection of the "diffuse" extraplanar dust (eDust), traced by the vertically extended, scattered UV starlight, always coincides with the presence of the extraplanar Hα emission. A strong correlation between the scale heights of the extraplanar Hα and UV emissions is also found; the scale height at Hα is found to be ∼ 0.74 of the scale height at FUV. Our results may indicate the multiphase nature of the diffuse ionized gas and dust in the galactic halos. The existence of eDust in galaxies where the extraplanar Hα emission is detected suggests that a larger portion of the extraplanar Hα emission than that predicted in previous studies may be caused by Hα photons that originate from H II regions in the galactic plane and are subsequently scattered by the eDust. This possibility raise a in studying the eDIG. We also find that the scale heights of the extraplanar emissions normalized to the galaxy size correlate well with the star formation rate surface density of the galaxies. The properties of eDust in our galaxies is on a continuation line of that found through previous observations of the extraplanar polycyclic aromatic hydrocarbons emission in more active galaxies known to have galactic winds.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Comparison of the Extraplanar Hα and UV Emissions in the Halos of Nearby Edge-on Spiral Galaxies

Seon

Shinn

et al. 2018

ApJ

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“…For other galaxies, the warm gas disk is detected in various observations. Direct imaging on nearby edge-on galaxies has detected the warm gas disk at radii of ≈ 1 − 10 kpc in X-ray band, UV band, or nebula emission lines (Rand et al 2008;Li & Wang 2013;Boettcher et al 2016;Hodges-Kluck et al 2016). However, for the warm CGM, these observations are limited at larger radii (> 50 kpc) due to the current instrument limitations and the low surface brightness of the diffuse ionized gas.…”

Section: Introductionmentioning

confidence: 99%

The Warm Gaseous Disk and the Anisotropic Circumgalactic Medium of the Milky Way

Bregman

2019

ApJ

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The warm (log T ≈ 5) gas is an important gaseous component in the galaxy baryonic cycle. We built a 2-dimension disk-CGM model to study the warm gas distribution of the Milky Way (MW) using the absorption line surveys of Si IV and O VI. In this model, the disk component of both ions has the same density profile (n(r, z) = n 0 exp(−|z|/z 0 ) exp(−r/r 0 )) with a scale height of z 0 = 2.6 ± 0.4 kpc and a scale length of r 0 = 6.1 ± 1.2 kpc. For this disk component, we calculate the warm gas mass of log(M/M ⊙ ) = (7.6 ± 0.2) − log Z Z⊙ . The similar disk density profiles and total masses of Si IV and O VI-bearing gas set constraints on the ionization mechanisms. We suggest that the warm gas disk might be dominated by the Galactic fountain mechanism, which ejects and recycles gas to set both the scale height and the scale length of the warm gas disk. The CGM component in our model has a dependence on Galactic latitude with a higher column density along the direction perpendicular to the Galactic plane (b = 90 • ) than the column density along the radial direction (b = 0 • ). The column density difference between these two directions is 0.82 ± 0.32 dex at 6.3σ for both ions. This difference may be due to the enrichment of Galactic feedback to the entire CGM, or an additional interaction layer between the warm gas disk and the CGM; existing data cannot distinguish between these two scenarios. If this higher column density at b = 90 • is for the entire CGM, the total warm CGM mass is log(M/M ⊙ ) ≈ (9.5 − 9.8) − log Z 0.5Z⊙ within the MW virial radius of 250 kpc.

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“…Background AGN sightlines through external galaxies rarely pass through the disk, and when this occurs, it is impossible to spatially assign a height to the absorption. The exception to this is for edge-on galaxies, which have been studied in X-ray emission (Strickland et al 2004;Hodges-Kluck & Bregman 2013;Li & Wang 2013) and through dust-scattering halos (Hodges-Kluck & Bregman 2014;Hodges-Kluck et al 2016). The dust-scattering halos indicate a change in the nature of the dust metallicity at 5 − 10 kpc, suggesting a transition to the extended hot halo.…”

Section: Introductionmentioning

confidence: 99%

HST/COS Observations of the Warm Ionized Gaseous Halo of NGC 891

Bregman

Hodges-Kluck

2019

ApJ

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The metallicity of galactic gaseous halos provides insights into accretion and feedback of galaxies. The nearby edge-on galaxy NGC 891 has a multi-component gaseous halo and a background AGN (LQAC 035+042 003) projected 5 kpc above the disk near the minor axis. Against the UV continuum of this AGN, we detect lines from 13 ions associated with NGC 891 in new HST/COS spectra. Most of the absorption is from the warm ionized gas with log T = 4.22 ± 0.04, log n H = −1.26 ± 0.51, and log N H = 20.81 ± 0.20. The metallicity of volatile elements (i.e., C, N, and S) is about half solar ([X/H] ≈ −0.3 ± 0.3), while Mg, Fe, and Ni show lower metallicities of [X/H] ≈ −0.9. The absorption system shows the depletion pattern seen for warm Galactic diffuse clouds, which is consistent with a mixture of ejected solar metallicity disk gases and the hot X-ray emitting halo (Z = 0.1 − 0.2Z ⊙ ). The warm ionized gases are about 5 times more massive than the cold H I emitting gases around the galactic center, which might lead to accretion with a mean rate of 10 2 M ⊙ yr −1 for a period of time. We also detect low metallicity (≈ 0.1 Z ⊙ ) gases toward LQAC 035+042 003 at 110 km s −1 (a high velocity cloud) and toward another sight line (3C 66A; 108 kpc projected from NGC 891) at 30 km s −1 . This low metallicity material could be the cold mode accretion from IGM or the tidal disruption of satellites in the NGC 891 halo.

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Ultraviolet Halos Around Spiral Galaxies. I. Morphology

Cited by 27 publications

References 75 publications

Comparison of the Extraplanar Hα and UV Emissions in the Halos of Nearby Edge-on Spiral Galaxies

Comparison of the Extraplanar Hα and UV Emissions in the Halos of Nearby Edge-on Spiral Galaxies

The Warm Gaseous Disk and the Anisotropic Circumgalactic Medium of the Milky Way

HST/COS Observations of the Warm Ionized Gaseous Halo of NGC 891

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