Phase Lags in the Optical-Infrared Light Curves of AGB Stars

To search for phase lags in the optical-infrared light curves of asymptotic giant branch stars, we have compared infrared data from the COBE DIRBE satellite with optical light curves from the AAVSO and other sources. We found 17 examples of phase lags in the time of maximum in the infrared vs. that in the optical, and 4 stars with no observed lags. There is a clear difference between the Mira variables and the semi-regulars in the sample, with the maximum in the optical preceding that in the near-infrared in the Miras, while in most of the semi-regulars no lags are observed. Comparison to published theoretical models indicates that the phase lags in the Miras are due to strong titanium oxide absorption in the visual at stellar maximum, and suggests that Miras pulsate in the fundamental mode, while at least some semi-regulars are first overtone pulsators. There is a clear optical-near-infrared phase lag in the carbon-rich Mira V CrB; this is likely due to C2 and CN absorption variations in the optical.Comment: AJ, in pres

Extended Ultraviolet Disks and Ultraviolet-bright Disks in Low-mass E/S0 Galaxies

We have identified 15 extended ultraviolet (XUV) disks in a largely field sample of 38 E/S0 galaxies that have stellar masses primarily below ~4 × 10^(10) M_☉ and comparable numbers on the red and blue sequences. We use a new purely quantitative XUV-disk definition designed with reference to the "Type 1" XUV-disk definition found in the literature, requiring UV extension relative to a UV-defined star formation threshold radius. The 39% ± 9% XUV-disk frequency for these E/S0s is roughly twice the ~20% reported for late-type galaxies (although differences in XUV-disk criteria complicate the comparison), possibly indicating that XUV disks are preferentially associated with galaxies experiencing weak or inefficient star formation. Consistent with this interpretation, we find that the XUV disks in our sample do not correlate with enhanced outer-disk star formation as traced by blue optical outer-disk colors. However, UV-Bright (UV-B) disk galaxies with blue UV colors outside their optical 50% light radii do display enhanced optical outer-disk star formation as well as enhanced atomic gas content. UV-B disks occur in our E/S0s with a 42^(+9)_–8% frequency and need not coincide with XUV disks; thus their combined frequency is 61% ± 9%. For both XUV and UV-B disks, UV colors typically imply <1 Gyr ages, and most such disks extend beyond the optical R_(25) radius. XUV disks occur over the full sample mass range and on both the red and blue sequences, suggesting an association with galaxy interactions or another similarly general evolutionary process. In contrast, UV-B disks favor the blue sequence and may also prefer low masses, perhaps reflecting the onset of cold-mode gas accretion or another mass-dependent evolutionary process. Virtually all blue E/S0s in the gas-rich regime below stellar mass M_t ~ 5 × 10^9 M_☉ (the "gas-richness threshold mass") display UV-B disks, supporting the previously suggested association of this population with active disk growth

Disk Regrowth in E/S0 Galaxies and its Environmental Dependence

This work is focused on the investigation of observational evidence for the predicted disk regrowth process, which may allow spheroid-dominated E/S0 galaxies to rebuild spiral disks resembling that of the Milky Way Galaxy. By combining analysis of several complementary galaxy samples, we derive new observational constraints on the frequency, significance, and conditions of E/S0 disk regrowth. We find that UV-detected disks, which represent recent star formation activity, are exceptionally common in low-mass E/S0 galaxies, and we define a new class of UV-Bright (UV-B) disk E/S0s that is associated with significant (>10% by mass) recent disk growth, blue optical outer-disk colors, and enhanced atomic gas content. These UV-B disks are closely linked to a particular class of low-mass, optically blue E/S0s that were previously hypothesized to host active disk regrowth. The detection of UV-B disks around nearly all low-mass, blue E/S0s supports this picture and reinforces the potential importance of mass scales in the disk regrowth process. We also find that another type of mass scale, involving the mass of the group halo in which a galaxy resides, appears to play an important role in disk regrowth. Below a group halo mass of ~10^11.5 Msun, blue E/S0s, gas-dominated galaxies, and UV-B disks all become more common, which may imply that such low group halo mass environments are important for allowing disk regrowth to proceed. This picture is consistent with both the variations of E/S0 and spiral galaxy frequency as a function of environment, with spiral galaxy frequencies rising at low group halo mass, and the observed similarity between typical environments of E/S0 and spiral galaxies at low baryonic mass (<10^10 Msun). Finally, we find direct evidence for secondary stellar disks in the kinematics of 6 out of 24 S0 galaxies for which we can confidently assess the presence or absence of secondary disks, but due to the small number of identifications, we cannot yet draw firm conclusions about any preference for specific mass, environment, or color regimes among such galaxies.Doctor of Philosoph

Randomised controlled trial of exercise for low back pain : clinical outcomes, costs and preferences

Objective: To evaluate effectiveness of an exercise programme in a community setting for patients with low back pain to encourage a return to normal activities. Design: Randomised controlled trial of progressive exercise programme compared with usual primary care management. Patients' preferences for type of management were elicited independently of randomisation. Participants: 187 patients aged 18-60 years with mechanical low back pain of 4 weeks to 6 months' duration. Interventions: Exercise classes led by a physiotherapist that included strengthening exercises for all main muscle groups, stretching exercises, relaxation session, and brief education on back care. A cognitive-behavioural approach was used. Main outcome measures: Assessments of debilitating effects of back pain before and after intervention and at 6 months and 1 year later. Measures included Roland disability questionnaire, Aberdeen back pain scale, pain diaries, and use of healthcare services. Results: At 6 weeks after randomisation, the intervention group improved marginally more than the control group on the disability questionnaire and reported less distressing pain. At 6 months and 1 year, the intervention group showed significantly greater improvement in the disability questionnaire score (mean difference in changes 1.35, 95% confidence interval 0.13 to 2.57). At 1 year, the intervention group also showed significantly greater improvement in the Aberdeen back pain scale (4.44, 1.01 to 7.87) and reported only 378 days off work compared with 607 in the control group. The intervention group used fewer healthcare resources. Outcome was not influenced by patients' preferences. Conclusions: The exercise class was more clinically effective than traditional general practitioner management, regardless of patient preference, and was cost effective

ECO and RESOLVE: Galaxy Disk Growth in Environmental Context

We study the relationships between galaxy environments and galaxy properties related to disk (re)growth, considering two highly complete samples that are approximately baryonic mass limited into the high-mass dwarf galaxy regime, the Environmental COntext (ECO) catalog (data release herein) and the B-semester region of the REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey. We quantify galaxy environments using both group identification and smoothed galaxy density field methods. We use by-eye and quantitative morphological classifications plus atomic gas content measurements and estimates. We find that blue early-type (E/S0) galaxies, gas-dominated galaxies, and UV-bright disk host galaxies all become distinctly more common below group halo mass ~10^11.5 Msun, implying that this low group halo mass regime may be a preferred regime for significant disk growth activity. We also find that blue early-type and blue late-type galaxies inhabit environments of similar group halo mass at fixed baryonic mass, consistent with a scenario in which blue early types can regrow late-type disks. In fact, we find that the only significant difference in the typical group halo mass inhabited by different galaxy classes is for satellite galaxies with different colors, where at fixed baryonic mass red early and late types have higher typical group halo masses than blue early and late types. More generally, we argue that the traditional morphology-environment relation (i.e., that denser environments tend to have more early types) can be largely attributed to the morphology-galaxy mass relation for centrals and the color-environment relation for satellites.Comment: 26 pages and 28 figures; v2 contains minor figure and text updates to match final published version in ApJ; ECO data table release now available at http://resolve.astro.unc.edu/pages/data.ph