The Remarkable High Pressure of the Local Leo Cold Cloud

Meyer, David M.; Lauroesch, J. T.; Peek, J. E. G.; Heiles, Carl

doi:10.1088/0004-637x/752/2/119

Cited by 36 publications

(46 citation statements)

References 47 publications

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“…Figure 3 revisits the relationships between N(C I tot ) and the corresponding column densities of Na I, K I, CH, H 2 , and H tot , for the Galactic sight lines included in the recent surveys of Burgh et al (2010) and JT11 (Appendix Table 8) and for the seven SMC and LMC sight lines examined in this study ( Table 4). The lower end of the relationship between N(C I tot ) and N(Na I) is largely defined by the Galactic components seen toward our seven SMC and LMC stars-which are quite consistent with an extrapolation of the trend seen at higher column densities in the C I data from Burgh et al (2010) and JT11 and with the values found for several lower column density Galactic sight lines (Jenkins 2002; Meyer et al 2012). As noted above, N(C I tot ) is fairly tightly correlated (r=0.91-0.98) with N(Na I), N (K I), and N(CH) in the local Galactic ISM (Table 5).…”

Section: Abundance and Behavior Of CIsupporting

confidence: 85%

Thermal Pressures in the Interstellar Medium of the Magellanic Clouds*

Welty

Lauroesch

Wong

et al. 2016

ApJ

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We discuss the thermal pressures (n H T) in predominantly cold, neutral interstellar gas in the Magellanic Clouds, derived from analyses of the fine-structure excitation of neutral carbon, as seen in high-resolution Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra of seven diverse sight lines in the LMC and SMC. Detailed fits to the line profiles of the absorption from C I, C I * , and C I ** yield consistent column densities for the three to six C I multiplets detected in each sight line. In the LMC and SMC, N(C I tot ) is consistent with Galactic trends versus N(Na I) and N(CH), but is slightly lower versus N(K I) and N(H 2 ). As for N(Na I) and N(K I), N(C I tot ) is generally significantly lower, for a given N(H tot ), in the LMC and (especially) in the SMC, compared to the local Galactic relationship. For the LMC and SMC components with well-determined column densities for C I, C I * , and C I ** , the derived thermal pressures are typically factors of a few higher than the values found for most cold, neutral clouds in the Galactic ISM. Such differences are consistent with the predictions of models for clouds in systems (like the LMC and SMC) that are characterized by lower metallicities, lower dust-to-gas ratios, and enhanced radiation fields-where higher pressures are required for stable cold, neutral clouds. The pressures may be further enhanced by energetic activity (e.g., due to stellar winds, star formation, and/or supernova remnants) in several of the regions probed by these sight lines. Comparisons are made with the C I observed in some quasar absorption-line systems.

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Section: Abundance and Behavior Of CIsupporting

confidence: 85%

Thermal Pressures in the Interstellar Medium of the Magellanic Clouds*

Welty

Lauroesch

Wong

et al. 2016

ApJ

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“…However, a recent study based on multi-epoch low resolution SDSS spectra (Hacker et al 2013) suggests that some narrow intervening systems (mainly Mg ii and Fe ii) might also display variability. These authors propose that time changes are due to the transverse motion of the LoS through the absorber coupled to the presence of structure in the absorbing gas at scales in the range 10-100 au, similar to what is observed for diffuse neutral gas in our own Galaxy (Crawford 2003;Lauroesch 2007;Welty 2007;Meyer et al 2012). Indeed, transverse peculiar velocity values of a few 100 km s −1 are expected for the target, the observer, and the intervening gas, which imply drifts over a few years falling in this range.…”

Section: Introductionsupporting

confidence: 72%

Time variations of narrow absorption lines in high resolution quasar spectra

Boissé

Bergeron

Prochaska

et al. 2015

A&A

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Aims. We have searched for temporal variations of narrow absorption lines in high resolution quasar spectra. A sample of five distant sources were assembled, for which two spectra are available, either VLT/UVES or Keck/HIRES, which were taken several years apart. Methods. We first investigate under which conditions variations in absorption line profiles can be detected reliably from high resolution spectra and discuss the implications of changes in terms of small-scale structure within the intervening gas or intrinsic origin. The targets selected allow us to investigate the time behaviour of a broad variety of absorption line systems by sampling diverse environments: the vicinity of active nuclei, galaxy halos, molecular-rich galaxy disks associated with damped Lyα systems, as well as neutral gas within our own Galaxy.Results. Intervening absorption lines from Mg ii, Fe ii, or proxy species with lines of lower opacity tracing the same kind of (moderately ionised) gas appear in general to be remarkably stable (1σ upper limits as low as 10% for some components on scales in the range 10-100 au), even for systems at z abs ≈ z e . Marginal variations are observed for Mg ii lines towards PKS 1229−021 at z abs = 0.83032; however, we detect no systems that display any change as large as those reported in low resolution SDSS spectra.The lack of clear variations for low β Mg ii systems does not support the existence of a specific population of absorbers made of sweptup gas towards blazars. In neutral or diffuse molecular media, clear changes are seen for Galactic Na i lines towards PKS 1229−02 (decrease in N by a factor of four for one of the five components over 9.7 yr), corresponding to structure on a scale of about 35 au, in good agreement with known properties of the Galactic interstellar medium. Tentative variations are detected for H 2 J = 3 lines towards FBQS J2340−0053 at z abs = 2.05454 ( 35% change in column density, N, over 0.7 yr in the rest frame), suggesting there is structure at the 10 au-scale for this warm molecular gas. A marginal change is also seen in C i from another velocity component of the same absorption system ( 70% variation in N(C i).

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“…Hence it is well within the cavity of the Local Bubble and the closest known cold neutral gas cloud (Peek et al 2011;Meyer et al 2012). Our targets skirt this cloud but some sight lines from the northern hemisphere survey crossed it.…”

Section: Mapsmentioning

confidence: 65%

Probing the Local Bubble with diffuse interstellar bands

Bailey

Loon

Farhang

et al. 2015

A&A

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Context. The Sun traverses a low-density, hot entity called the Local Bubble. Despite its relevance to life on Earth, the conditions in the Local Bubble and its exact configuration are not very well known. Besides that, there is some unknown interstellar substance that causes a host of absorption bands across the optical spectrum, called diffuse interstellar bands (DIBs). Aims. We have started a project to chart the Local Bubble in a novel way and learn more about the carriers of the DIBs, by using DIBs as tracers of diffuse gas and environmental conditions. Methods. We conducted a high signal-to-noise spectroscopic survey of 670 nearby early-type stars to map DIB absorption in and around the Local Bubble. The project started with a southern hemisphere survey conducted at the European Southern Observatory's New Technology Telescope and has since been extended to an all-sky survey using the Isaac Newton Telescope. Results. In this first paper in the series, we introduce the overall project and present the results from the southern hemisphere survey. We make available a catalogue of equivalent-width measurements of the DIBs at 5780, 5797, 5850, 6196, 6203, 6270, 6283, and 6614 Å, of the interstellar Na i D lines at 5890 and 5896 Å, and of the stellar He i line at 5876 Å. We find that the 5780 Å DIB is relatively strong throughout, as compared to the 5797 Å DIB, but especially within the Local Bubble and at the interface with a more neutral medium. The 6203 Å DIB shows similar behaviour with respect to the 6196 Å DIB. Some nearby stars show surprisingly strong DIBs, whereas some distant stars show very weak DIBs, indicating small-scale structure within, as well as outside, the Local Bubble. The sight lines with non-detections trace the extent of the Local Bubble especially clearly and show it opening out into the halo. Conclusions. The Local Bubble has a wall that is in contact with hot gas and/or a harsh interstellar radiation field. That wall is perforated, though, causing leakage of radiation and possibly hot gas. On the other hand, compact self-shielded cloudlets are present much closer to the Sun, probably within the Local Bubble itself. As for the carriers of the DIBs, our observations confirm the notion that these are large molecules whose differences in behaviour are mainly governed by their differing resilience and/or electrical charge, with more subtle differences possibly related to varying excitation.

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The Remarkable High Pressure of the Local Leo Cold Cloud

Cited by 36 publications

References 47 publications

Thermal Pressures in the Interstellar Medium of the Magellanic Clouds*

Thermal Pressures in the Interstellar Medium of the Magellanic Clouds*

Time variations of narrow absorption lines in high resolution quasar spectra

Probing the Local Bubble with diffuse interstellar bands

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