Molecular hydrogen beyond the optical edge of an isolated spiral galaxy

We know little about the outermost portions of galaxies because there is little light coming from them. We do know that in many cases atomic hydrogen (HI) extends well beyond the optical radius \cite{Casertano91}. In the centers of galaxies, however, molecular hydrogen (H2) usually dominates by a large factor, raising the question of whether H2 is abundant also in the outer regions but hitherto unseen.Here we report the detection of emission from carbon monoxide (CO), the most abundant tracer of H2, beyond the optical radius of the nearby galaxy NGC 4414. The molecular clouds probably formed in the regions of relatively high HI column density and in the absence of spiral density waves. The relative strength of the lines from the two lowest rotational levels indicates that both the temperature and density of the H2 are quite low compared to conditions closer to the center. The inferred surface density of the molecular material continues the monotonic decrease from the inner regions. We conclude that while molecular clouds can form in the outer region of this galaxy, there is little mass associated with them.Comment: 3 Nature page

Leadership, character and its development: a qualitative exploration.

The purpose of this study was to explore (1) what organisational leaders consider to be character elements of leaders within the workplace, (2) what influences leaders’ character development, and (3) how an organisation can continue the process of character development. The literature review and findings revealed that leadership, integrity, industriousness, empathy, loyalty, optimism, fairness and compassion are the most sought after character elements within leaders in the workplace. Leadership and integrity were found to be the most supported character elements. The findings also indicate that work environmental factors, a person’s own efforts, and the daily experiences of work life contribute towards character development

HCN versus HCO+ as dense molecular gas mass tracer in Luminous Infrared Galaxies

It has been recently argued that the HCN J=1--0 line emission may not be an unbiased tracer of dense molecular gas (\rm n\ga 10^4 cm^{-3}) in Luminous Infrared Galaxies (LIRGs: $\rm L_{FIR}> 10^{11} L_{\odot}$) and HCO$^+$ J=1--0 may constitute a better tracer instead (Graci\'a-Carpio et al. 2006), casting doubt into earlier claims supporting the former as a good tracer of such gas (Gao & Solomon 2004; Wu et al. 2006). In this paper new sensitive HCN J=4--3 observations of four such galaxies are presented, revealing a surprisingly wide excitation range for their dense gas phase that may render the J=1--0 transition from either species a poor proxy of its mass. Moreover the well-known sensitivity of the HCO$^+$ abundance on the ionization degree of the molecular gas (an important issue omitted from the ongoing discussion about the relative merits of HCN and HCO$^+$ as dense gas tracers) may severely reduce the HCO$^+$ abundance in the star-forming and highly turbulent molecular gas found in LIRGs, while HCN remains abundant. This may result to the decreasing HCO$^+$/HCN J=1--0 line ratio with increasing IR luminosity found in LIRGs, and casts doubts on the HCO$^+$ rather than the HCN as a good dense molecular gas tracer. Multi-transition observations of both molecules are needed to identify the best such tracer, its relation to ongoing star formation, and constrain what may be a considerable range of dense gas properties in such galaxies.Comment: 16 pages, 4 figures, Accepted for publication in the Astrophysical Journa

Chandra Detection of Massive Black Holes in Galactic Cooling Flows

Anticipating forthcoming observations with the Chandra X-ray telescope, we describe the continuation of interstellar cooling flows deep into the cores of elliptical galaxies. Interstellar gas within about r = 50 parsecs from the massive black hole is heated to T > 1 keV and should be visible unless thermal heating is diluted by non-thermal pressure. Since our flows are subsonic near the massive black holes, distributed cooling continues within 300 pc from the center. Dark, low mass stars formed in this region may be responsible for some of the mass attributed to central black holes.Comment: 6 pages with 3 figures; accepted by Astrophysical Journal Letter

Where Do Cooling Flows Cool?

Although only about 5 percent of the total baryonic mass in luminous elliptical galaxies is in the form of cooled interstellar gas, it is concentrated within the optical effective radius r_e where it influences the local dynamical mass. The mass of cooled gas must be spatially distributed since it greatly exceeds the masses of central black holes. We explore here the proposition that a population of low mass, optically dark stars is created from the cooled gas. We consider a wide variety of radial distributions for the interstellar cooling, but only a few are consistent with observed X-ray surface brightness profiles. In a region of concentrated interstellar cooling, the X-ray emission can exceed that observed, suggesting the presence of additional support by magnetic stresses or non-thermal pressure. In general we find that the mass of cooled gas contributes significantly to stellar dynamical mass to light ratios which vary with galactic radius. If the stars formed from cooled interstellar gas are optically luminous, their influence on the the mass to light ratio would be reduced. The mass of cooled gas inside r_e is sensitive to the rate that old stars lose mass, which is nearly independent of the initial mass function of the old stellar population.Comment: 18 pages with 6 figures; accepted by Astrophysical Journa

Spitzer Uncovers Active Galactic Nuclei Missed by Optical Surveys in 7 Late-type Galaxies

We report the discovery using Spitzers high resolution spectrograph of 7 Active Galactic Nuclei (AGN) in a sample of 32 late-type galaxies that show no definitive signatures of AGN in their optical spectra. Our observations suggest that the AGN detection rate in late-type galaxies is possibly 4 times larger than what optical spectroscopic observations alone suggest. We demonstrate using photoionization models with an input AGN and an extreme EUV-bright starburst ionizing radiation field that the observed mid-infrared line ratios cannot be replicated unless an AGN contribution, in some cases as little as 10% of the total galaxy luminosity, is included. These models show that when the fraction of the total luminosity due to the AGN is low, optical diagnostics are insensitive to the presence of the AGN. In this regime of parameter space, the mid-infrared diagnostics offer a powerful tool for uncovering AGN missed by optical spectroscopy. The AGN bolometric luminosities in our sample range from ~3 X 10^41 - ~2 X 10^43 ergs s^-1, which, based on the Eddington limit, corresponds to a lower mass limit for the black hole that ranges from ~3 X 10^3Mdot to as high as ~1.5 X 10^5Mdot. These lower mass limits however do not put a strain on the well-known relationship between the black hole mass and the host galaxy's stellar velocity dispersion established in predominantly early-type galaxies. Our findings add to the growing evidence that black holes do form and grow in low-bulge environments and that they are significantly more common than optical studies indicate.Comment: 8 figures, 17 pages, astro-ph\0801.2766 (Abel & Satyapal 2008; ApJ accepted) and this posting designed to form a two-part investigatio

Molecular Gas in Candidate Double Barred Galaxies III. A Lack of Molecular Gas?

Most models of double-barred galaxies suggest that a molecular gas component is crucial for maintaining long-lived nuclear bars. We have undertaken a CO survey in an attempt to determine the gas content of these systems and to locate double barred galaxies with strong CO emission that could be candidates for high resolution mapping. We observed 10 galaxies in CO J=2-1 and J=3-2 and did not detect any galaxies that had not already been detected in previous CO surveys. We preferentially detect emission from galaxies containing some form of nuclear activity. Simulations of these galaxies require that they contain 2% to 10% gas by mass in order to maintain long-lived nuclear bars. The fluxes for the galaxies for which we have detections suggest that the gas mass fraction is in agreement with these models requirements. The lack of emission in the other galaxies suggests that they contain as little as 7 x 10^6 solar masses of molecular material which corresponds to < 0.1% gas by mass. This result combined with the wide variety of CO distributions observed in double barred galaxies suggests the need for models of double-barred galaxies that do not require a large, well ordered molecular gas component.Comment: 17 pages (3 figures embedded on pg 17). To appear in the March 10 issue of the Astrophysical Journa

Nurses' understanding and experience of applying painful stimuli when assessing components of the Glasgow Coma Scale

Aims and Objectives To evaluate nurses' application, understanding and experience of applying painful stimuli when assessing components of the Glasgow Coma Scale. Background The Glasgow Coma Scale has been subjected to much scrutiny and debate since its publication in 1974. However, criticism, confusion and misunderstandings in relation to the use of painful stimuli and its application remain. An absence of evidence informed guidance on the use and duration of application of painful stimuli remains, with the potential to negatively impact on decision‐making, delay responsiveness to neurological deterioration and result in adverse incidents. Design and Methods This international study used an online self‐reported survey design to ascertain neuroscience nurses' perceptions and experiences around the application of painful stimuli as part of a GCS assessment (n=273). STROBE checklist was used. Results Data revealed varied practices and a sense of confusion from participants. Anatomical sites for the assessment of pain varied, but most respondents identified the trapezius grip/pinch in assessing eye opening and motor response. Most respondents identified they assess eye opening and motor responses together and apply pain for less than 6 seconds to elicit a response. Witnessed complications secondary to applying a painful stimulus were varied and of concern. Conclusion Neuroscience nurses in this study clearly required evidence informed guidelines to underpin practice in both applying painful stimuli and in managing the experience of the person in their care and the family response. A standardised approach to education is necessary to ensure greater interrater reliability of assessment not only within nursing but across professions. Relevance to Practice Results of this study illustrate inconsistency and confusion when using the Glasgow Coma Scale in practice; this has the potential to compromise care. Clarity around the issues highlighted is necessary. Moreover, these results can inform future guidelines and education required for supporting nurses in practice.<br/

Cold dust in a selected sample of nearby galaxies. I. The interacting galaxy NGC4631

We have observed the continuum emission of the interacting galaxy NGC4631 at 0.87 and 1.23mm using the Heinrich-Hertz-Telescope on Mt. Graham and the IRAM 30-m telescope on Pico Veleta. We have obtained fully sampled maps which cover the optical emission out to a radius of about 7' at both wavelengths. For a detailed analysis, we carefully subtracted the line contributions and synchrotron and free-free emission from the data, which added up to 6% at 1.23mm and 10% at 0.87mm. We combined the flux densities with FIR data to obtain dust spectra and calculate dust temperatures, absorption cross sections, and masses. Assuming a ``standard'' dust model, which consists of two populations of big grains at moderate and warm temperatures, we obtained temperatures of 18K and 50K for the both components. However, such a model suffers from an excess of the radiation at 1.23mm, and the dust absorption cross section seems to be enhanced by a factor 3 compared to previous results and theoretical expectations. At large galactocentric radii, where the galaxy shows disturbances as a result of gravitational interaction, this effect seems to be even stronger. Some possibilities to resolve these problems are discussed. The data could be explained by a very cold dust component at a temperature of 4-6K, an increased abundance of very small grains, or a component of grains with unusual optical properties. We favour the latter possibility, since the first two lead to inconsistencies.Comment: 12 pages, 6 figures, accepted for publication in Astronomy & Astrophysics. Updated version with minor errors corrected (typos, LaTeX formatting, missing citation