46 research outputs found

    The UVES Spectral Quasar Absorption Database (SQUAD) Data Release 1: The first 10 million seconds

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    We present the first data release (DR1) of the UVES Spectral Quasar Absorption Database (SQUAD), comprising 467 fully reduced, continuum-fitted high-resolution quasar spectra from the Ultraviolet and Visual Echelle Spectrograph (UVES) on the European Southern Observatory's Very Large Telescope. The quasars have redshifts z=0z=0-5, and a total exposure time of 10 million seconds provides continuum-to-noise ratios of 4-342 (median 20) per 2.5-km/s pixel at 5500 \AA. The SQUAD spectra are fully reproducible from the raw, archival UVES exposures with open-source software, including our UVES_popler tool for combining multiple extracted echelle exposures which we document here. All processing steps are completely transparent and can be improved upon or modified for specific applications. A primary goal of SQUAD is to enable statistical studies of large quasar and absorber samples, and we provide tools and basic information to assist three broad scientific uses: studies of damped Lyman-α\alpha systems (DLAs), absorption-line surveys and time-variable absorption lines. For example, we provide a catalogue of 155 DLAs whose Lyman-α\alpha lines are covered by the DR1 spectra, 18 of which are reported for the first time. The HI column densities of these new DLAs are measured from the DR1 spectra. DR1 is publicly available and includes all reduced data and information to reproduce the final spectra.Comment: 21 pages, 18 figures. Accepted by MNRAS. All final quasar spectra, reduced contributing exposures, and supplementary material available via https://github.com/MTMurphy77/UVES_SQUAD_DR

    Approximate volume and integration for basic semi-algebraic sets

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    Given a basic compact semi-algebraic set \K\subset\R^n, we introduce a methodology that generates a sequence converging to the volume of \K. This sequence is obtained from optimal values of a hierarchy of either semidefinite or linear programs. Not only the volume but also every finite vector of moments of the probability measure that is uniformly distributed on \K can be approximated as closely as desired, and so permits to approximate the integral on \K of any given polynomial; extension to integration against some weight functions is also provided. Finally, some numerical issues associated with the algorithms involved are briefly discussed

    Hα3: an Hα imaging survey of HI selected galaxies from ALFALFA. VI. The role of bars in quenching star formation from z = 3 to the present epoch

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    A growing body of evidence indicates that the star formation rate per unit stellar mass (sSFR) decreases with increasing mass in normal main-sequence star-forming galaxies. Many processes have been advocated as being responsible for this trend (also known as mass quenching), e.g., feedback from active galactic nuclei (AGNs), and the formation of classical bulges. In order to improve our insight into the mechanisms regulating the star formation in normal star-forming galaxies across cosmic epochs, we determine a refined star formation versus stellar mass relation in the local Universe. To this end we use the Hα narrow-band imaging follow-up survey (Hα3) of field galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Coma and Local superclusters. By complementing this local determination with high-redshift measurements from the literature, we reconstruct the star formation history of main-sequence galaxies as a function of stellar mass from the present epoch up to z = 3. In agreement with previous studies, our analysis shows that quenching mechanisms occur above a threshold stellar mass Mknee that evolves with redshift as ∝ (1 + z)2. Moreover, visual morphological classification of individual objects in our local sample reveals a sharp increase in the fraction of visually classified strong bars with mass, hinting that strong bars may contribute to the observed downturn in the sSFR above Mknee. We test this hypothesis using a simple but physically motivated numerical model for bar formation, finding that strong bars can rapidly quench star formation in the central few kpc of field galaxies. We conclude that strong bars contribute significantly to the red colors observed in the inner parts of massive galaxies, although additional mechanisms are likely required to quench the star formation in the outer regions of massive spiral galaxies. Intriguingly, when we extrapolate our model to higher redshifts, we successfully recover the observed redshift evolution for Mknee. Our study highlights how the formation of strong bars in massive galaxies is an important mechanism in regulating the redshift evolution of the sSFR for field main-sequence galaxies

    The complete census of optically selected AGNs in the Coma Supercluster: the dependence of AGN activity on the local environment

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    To investigate the dependence of the occurrence of active galactic nuclei (AGNs) on local galaxy density, we study the nuclear properties of ~5000 galaxies in the Coma Supercluster whose density spans 2 orders of magnitude from the sparse filaments to the cores of the rich clusters. We obtained optical spectra of the nuclei of 177 galaxies using the 1.5m Cassini telescope, which are added to the 4785 spectra available from SDSS (DR7) to fill-in the incomplete coverage by SDSS of luminous galaxies. We perform a spectral classification of the nuclei of galaxies (with a completeness of 98% at r<17.77), classifying the nuclear spectra in six classes: three of them (SEY, sAGN, LIN) refer to AGNs and the remaining three (HII, RET, PAS) refer to different stages of starburst activity. To perform such classification, we use the WHAN diagnostic, after correcting Halpha by 1.3 A for underlying absorption. We find that 482 (10%) of 5027 galaxies host an AGN: their frequency strongly increases with increasing luminosity of the parent galaxies, such that 32% of galaxies with Log(i-Lum)<10.2 (Solar) harbor an AGN at their interior. In addition to their presence in luminous galaxies, AGNs are also found in red galaxies with < 1.15 \pm 0.15 mag. The majority of SEY and sAGN (strong AGNs) are associated with luminous late-type (or S0a) galaxies, while LIN (weak AGNs) and RET ("retired"), are mostly found among E/S0as. The number density of AGNs, HII region-like, and retired galaxies is found to anti-correlate with the local density of galaxies, such that their frequency drops by a factor of two near the cluster cores, while the frequency of galaxies containing passive nuclei increases by the same amount towards the center of rich clusters. The dependence of AGN number density on the local galaxy density is greater than the one implied by morphology segregation alone.Comment: 15 pages, 10 figures, 4 tables. Accepted for publication in A&

    Does the intermediate-mass black hole in LEDA 87300 (RGG 118) follow the near-quadratic Mbh-Mspheroid relation?

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    The mass scaling relation between supermassive black holes and their host spheroids has previously been described by a quadratic or steeper relation at low masses (105 &lt; Mbh/Mo â‰Č 107). How this extends into the realm of intermediate-mass black holes (102 &lt; Mbh/Mo &lt; 105) is not yet clear, although for the barred Sm galaxy LEDA 87300, Baldassare et al. recently reported a nominal virial mass of Mbh = 5 104 Mo residing in a "spheroid" of stellar mass equal to 6.3 108 Mo. We point out, for the first time, that LEDA 87300 therefore appears to reside on the near-quadratic Mbh-Msph,∗ relation. However, Baldassare et al. modeled the bulge and bar as the single spheroidal component of this galaxy. Here we perform a 3-component bulge+bar+disk decomposition and find a bulge luminosity which is 7.7 times fainter than the published "bulge" luminosity. After correcting for dust, we find that Mbulge = 0.9 108 Mo and Mbulge/Mdisk = 0.04 - which is now in accord with ratios typically found in Scd-Sm galaxies. We go on to discuss slight revisions to the stellar velocity dispersion (40 11 km s-1) and black hole mass () and show that LEDA 87300 remains consistent with the Mbh-σ relation, and also the near-quadratic Mbh-Msph,∗ relation when using the reduced bulge mass. LEDA 87300 therefore offers the first support for the rapid but regulated (near-quadratic) growth of black holes, relative to their host bulge/spheroid, extending into the domain of intermediate-mass black holes

    Galaxy bulges and their massive black holes: a review

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    With references to both key and oft-forgotten pioneering works, this article starts by presenting a review into how we came to believe in the existence of massive black holes at the centres of galaxies. It then presents the historical development of the near-linear (black hole)-(host spheroid) mass relation, before explaining why this has recently been dramatically revised. Past disagreement over the slope of the (black hole)-(velocity dispersion) relation is also explained, and the discovery of sub-structure within the (black hole)-(velocity dispersion) diagram is discussed. As the search for the fundamental connection between massive black holes and their host galaxies continues, the competing array of additional black hole mass scaling relations for samples of predominantly inactive galaxies are presented.Comment: Invited (15 Feb. 2014) review article (submitted 16 Nov. 2014). 590 references, 9 figures, 25 pages in emulateApJ format. To appear in "Galactic Bulges", E. Laurikainen, R.F. Peletier, and D.A. Gadotti (eds.), Springer Publishin

    Supermassive black holes and their host spheroids. I. Disassembling galaxies

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    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using 3.6 ÎŒm Spitzer imagery, which is a superb tracer of the stellar mass (superior to the K band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction, and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and - for the first time - 2D kinematics, we were able to account for spheroids; large-scale, intermediate-scale, and nuclear disks; bars; rings; spiral arms; halos; extended or unresolved nuclear sources; and partially depleted cores. For each individual galaxy, we compared our best-fit model with previous studies, explained the discrepancies, and identified the optimal decomposition. Moreover, we have independently performed one-dimensional (1D) and two-dimensional (2D) decompositions and concluded that, at least when modeling large, nearby galaxies, 1D techniques have more advantages than 2D techniques. Finally, we developed a prescription to estimate the uncertainties on the 1D best-fit parameters for the 66 spheroids that takes into account systematic errors, unlike popular 2D codes that only consider statistical errors

    The use of neutrophil-lymphocyte ratio for the prediction of refractory disease and coronary artery lesions in patients with Kawasaki disease

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    Background: Kawasaki disease is a vasculitis that can lead to cardiac complications, including coronary artery disease and cardiogenic shock. Various scoring systems have been developed to determine those that will be refractory to routine intravenous immunoglobulin therapy or develop coronary artery disease. The objective of this study was to determine if the neutrophil-lymphocyte ratio could predict refractory disease and coronary artery lesions in patients with Kawasaki disease. Methods: A systematic review of the literature was performed to identify manuscripts describing comparisons of neutrophil-lymphocyte ratio between those who had refractory disease and those who did not, and between those who developed coronary artery lesions and those who did not. Mean difference was compared between groups. Areas under the curve were utilised to determine the pooled area under the curve. Results: 12 studies with 5593 patients were included in the final analyses of neutrophil-lymphocyte ratio for the prediction of refractory disease. Neutrophil-lymphocyte ratio before therapy was higher in refractory disease with a mean difference of 2.55 (p \u3c 0.01) and pooled area under the curve of 0.724. Neutrophil-lymphocyte ratio after therapy was higher in refractory disease with a mean difference of 1.42 (p \u3c 0.01) and pooled area under the curve for of 0.803. Five studies with 1690 patients were included in the final analyses of neutrophil-lymphocyte ratio for the prediction of coronary artery lesions. Neutrophil-lymphocyte ratio before therapy was higher in coronary artery lesions with a mean difference of 0.65 (p \u3c 0.01). Conclusion: The use of neutrophil-lymphocyte ratio may help physicians in the identification of patients at risk of refractory disease and coronary artery lesions in patients with Kawasaki disease

    Xanthine derivatives for kidney protection in the critically ill pediatric population: A systematic review

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    Different types of diuretics have been used to minimize fluid overload after resuscitation. This meta-analysis determined the effects of xanthine derivatives on creatinine, creatinine clearance, and urine output. Studies included data from pediatric patients, whoused theophylline or aminophylline, and included pre- and postxanthine data for at least one of the outcomes of interest. A total of 13 studies with 198 patients were included in the pooled analyses. The study recorded data prior, and a mean of 36 hours after xanthine administration. This meta-analysis demonstrates that xanthine derivatives in critically ill children, using a dose of approximately5 mg/kg, lead to a statistically significant increase in creatinine clearance and urine output without significantly altering serum creatinine. Xanthine derivatives may be beneficial for fluid management in critically ill children. Further studies are warranted assessing the association with additional clinical outcomes
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