A Map of the Ionized Component of the Intermediate-Velocity Cloud Complex K

Haffner, L. M.; Reynolds, R. J.; Tufte, S. L.

doi:10.1086/322867

Cited by 36 publications

(36 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This result is similar to that for the intermediatevelocity clouds Complex K and Complex L, which have also been mapped in Hα with WHAM (Haffner et al 2001;Haffner 2005). In all three clouds, the presence of Hα and H i emission tend to track each other in corresponding sight lines, but there is no strong correlation between the Hα and H i intensities, with the exception of the tip of the Smith Cloud (blue "×" in Figure 2), which is the brightest portion in both Hα and H i.…”

Section: Discussion and Future Worksupporting

confidence: 86%

“…Typical Hα intensities for HVCs are 0.06-0.5 R (Tufte et al 1998;Haffner et al 2001;Weiner et al 2001Weiner et al , 2002Putman et al 2003;Haffner 2005); the intensities observed here for the Smith Cloud are in this range. The narrow range of Hα intensities for these clouds suggests that, like the WIM, all of these HVCs are ionized by a diffuse UV radiation field, not shocks or individual, local hot stars (see also Bland-Hawthorn et al 1998), which would produce significant variations in Hα intensity from cloud to cloud and even within a cloud.…”

Section: Discussion and Future Workmentioning

confidence: 48%

“…In all three clouds, the presence of Hα and H i emission tend to track each other in corresponding sight lines, but there is no strong correlation between the Hα and H i intensities, with the exception of the tip of the Smith Cloud (blue "×" in Figure 2), which is the brightest portion in both Hα and H i. Note that the peak Smith Cloud H i column density of 5.2 × 10 20 cm −2 (L08) is a factor of 10 higher than that for Complex K, 5.3×10 19 cm −2 (Haffner et al 2001), or Complex L, 3.6×10 19 cm −2 (P03). The lack of a strong correlation between Hα intensity and H i column density in the low-column density region of the cloud supports previous suggestions that the ionized gas is not mixed with the neutral gas and that variations in the Hα intensity outside the high-H i column density tip may be due to variations in the strength of the ionizing radiation field rather than the distribution of neutral gas.…”

Section: Discussion and Future Workmentioning

confidence: 92%

See 2 more Smart Citations

Ionized Gas in the Smith Cloud

Hill

Haffner

Reynolds

2009

ApJ

View full text Add to dashboard Cite

We present Wisconsin Hα Mapper observations of ionized gas in the Smith Cloud, a high-velocity cloud which Lockman et al. have recently suggested is interacting with the Galactic disk. Our Hα map shows the brightest Hα emission, 0.43 ± 0.04 R, coincident with the brightest H i, while slightly fainter Hα emission (0.25 ± 0.02 R) is observed in a region with H i intensities < 0.1 times as bright as the brightest H i. We derive an ionized mass of 3 × 10 6 M , comparable to the H i mass, with the H + mass spread over a considerably larger area than that of H i. An estimated Galactic extinction correction could adjust these values upward by 40%. Hα and [S ii] line widths toward the region of brightest emission constrain the electron temperature of the gas to be between 8000 K and 23,000 K. A detection of [N ii] λ6583 in the same direction with a line ratio [N ii]/Hα = 0.32 ± 0.05 constrains the metallicity of the cloud: for typical photoionization temperatures of 8000-12,000 K, the nitrogen abundance is 0.15-0.44 times solar. These results lend further support to the claim that the Smith Cloud is new material accreting onto the Galaxy.

show abstract

Section: Discussion and Future Worksupporting

confidence: 86%

Section: Discussion and Future Workmentioning

confidence: 48%

Section: Discussion and Future Workmentioning

confidence: 92%

See 1 more Smart Citation

Ionized Gas in the Smith Cloud

Hill

Haffner

Reynolds

2009

ApJ

View full text Add to dashboard Cite

show abstract

“…Several HVCs with strong direct distance constraints (see Wakker 2001 for a summary) have now been detected in H by WHAM (TRH98), Weiner et al (2001), and this survey. There is also an IVC (complex K; Haffner, Reynolds, & Tufte 2001) that has been completely mapped in H emission and has a distance constraint. The H emission measures from these clouds are …”

Section: The H Distance Constraintmentioning

confidence: 99%

Hα Emission from High‐Velocity Clouds and Their Distances

Putman

Bland-Hawthorn

Veilleux

et al. 2003

ApJ

181

209

View full text Add to dashboard Cite

We present deep H spectroscopy toward several high-velocity clouds (HVCs), which vary in structure from compact HVCs (CHVCs) to the Magellanic Stream. The clouds range from being bright ($640 mR) to having upper limits on the order of 30-70 mR. The H measurements are discussed in relation to their H i properties, and distance constraints are given to each of the complexes based onf f esc % 6% of the ionizing photons escaping normal to the Galactic disk ( f esc % 1% 2% when averaged over solid angle). The results suggest that many HVCs and CHVCs are within a $40 kpc radius from the Galaxy and are not members of the Local Group at megaparsec distances. However, the Magellanic Stream is inconsistent with this model and needs to be explained. It has bright H emission and little [N ii] emission and appears to fall into a different category than the currently detected HVCs. This may reflect the lower metallicities of the Magellanic Clouds compared to the Galaxy, but the strength of the H emission cannot be explained solely by photoionization from the Galaxy. The interaction of the Magellanic Stream with halo gas or the presence of yet unassociated young stars may assist in ionizing the Magellanic Stream.

show abstract

“…S is not depleted (Savage & Sembach 1996b and references therein), and its second ionization potential of 23.3 eV is high enough to ensure that S ii is the dominant ion in both neutral and partially ionized diffuse gas. From a study of H and [S ii] emission lines, Haffner et al (1999) find that typically S ii=S $ 0:3 0:8 in the WIM. We therefore have N (H i) þ N (H ii) ¼ (H=S) N (S ii), and thus we can derive the cooling rate per nucleon as…”

Section: Electron Density and Cmentioning

confidence: 99%

CiiRadiative Cooling of the Diffuse Gas in the Milky Way

Lehner¹,

Wakker²,

Savage³

2004

ApJ

View full text Add to dashboard Cite

The heating and cooling of the interstellar medium (ISM ) allow the gas in the ISM to coexist at very different temperatures in thermal pressure equilibrium. The rate at which the gas cools or heats is therefore a fundamental ingredient for any theory of the ISM. The heating cannot be directly determined, but the cooling can be inferred from observations of ÁC ii Ã , which is an important coolant in different environments. The amount of cooling can be measured through either the intensity of the 157.7 m [C ii] emission line or the C ii Ã absorption lines at 1037.018 and 1335.708 8, observable with the Far Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, respectively. We present the results of a survey of these far-UV absorption lines in 43 objects situated at j b j k 30 . Measured column densities of C ii Ã , S ii, P ii, and Fe ii are combined with H i 21 cm emission measurements to derive the cooling rates (per H atom using H i and per nucleon using S ii) and to analyze the ionization structure, depletion, and metallicity content of the low-, intermediate-, and high-velocity clouds (LVCs, IVCs, and HVCs) along the different sight lines. Based on the depletion and the ionization structure, the LVCs, IVCs, and HVCs consist mostly of warm neutral and ionized clouds. For the LVCs, the mean cooling rate in ergs s À1 per H atom is À25:70 þ0:19 À0:36 dex (1 dispersion). With a smaller sample and a bias toward high H i column density, the cooling rate per nucleon is similar. The corresponding total Galactic C ii luminosity in the 157.7 m emission line is L $ 2:6 ; 10 7 L . Combining N (C ii Ã ) with the intensity of H emission, we derive that $50% of the C ii Ã radiative cooling comes from the warm ionized medium (WIM). The large dispersion in the cooling rates is certainly due to a combination of differences in the ionization fraction, in the dust-to-gas fraction, and physical conditions between sight lines. For the IVC Intermediate-Velocity (IV ) Arch at z $ 1 kpc we find that on average the cooling is a factor of 2 lower than in the LVCs that probe gas at lower z. For an HVC (complex C, at z > 6 kpc) we find the much lower rate of À26:99 þ0:21 À0:53 dex, similar to the rates observed in a sample of damped Ly absorber systems (DLAs). The fact that in the Milky Way a substantial fraction of the C ii cooling comes from the WIM implies that this is probably also true in the DLAs. We also derive the electron density, assuming a typical temperature of the warm gas of 6000 K: for the LVCs, hn e i ¼ 0:08 AE 0:04 cm À3 , and for the IV Arch, hn e i ¼ 0:03 AE 0:01 cm À3 (1 dispersion). Finally, we measured the column densities N(S ii) and N(P ii) in many sight lines and confirm that sulphur appears undepleted in the ISM. Phosphorus becomes progressively more deficient when log N (H i) > 19:7 dex, which can mean that either P becomes more depleted into dust as more neutral gas is present or P is always depleted by about À0.3 dex, but the higher value of P ii at...

show abstract

A Map of the Ionized Component of the Intermediate-Velocity Cloud Complex K

Cited by 36 publications

References 24 publications

Ionized Gas in the Smith Cloud

Ionized Gas in the Smith Cloud

Hα Emission from High‐Velocity Clouds and Their Distances

CiiRadiative Cooling of the Diffuse Gas in the Milky Way

Contact Info

Product

Resources

About