Unobscured Type 2 Active Galactic Nuclei

Type 2 active galactic nuclei (AGNs) with intrinsically weak broad emission lines (BELs) would be exceptions to the unified model. After examining a number of proposed candidates critically, we find that the sample is contaminated significantly by objects with BELs of strengths indicating that they actually contain intermediate-type AGNs, plus a few Compton-thick sources as revealed by extremely low ratios of X-ray to nuclear IR luminosities. We develop quantitative metrics that show two (NGC 3147 and NGC 4594) of the remaining candidates to have BELs 2-3 orders of magnitude weaker than those of typical type 1 AGNs. Several more galaxies remain as candidates to have anomalously weak BELs, but this status cannot be confirmed with the existing information. Although the parent sample is poorly defined, the two confirmed objects are well under 1% of its total number of members, showing that the absence of a BEL is possible, but very uncommon in AGN. We evaluate these two objects in detail using multi-wavelength measurements including new IR data obtained with Spitzer and ground-based optical spectropolarimeteric observations. They have little X-ray extinction with N_H < ~10^(21) cm^(–2). Their IR spectra show strong silicate emission (NGC 4594) or weak aromatic features on a generally power-law continuum with a suggestion of silicates in emission (NGC 3147). No polarized BEL is detected in NGC 3147. These results indicate that the two unobscured type 2 objects have circumnuclear tori that are approximately face-on. Combined with their X-ray and optical/UV properties, this behavior implies that we have an unobscured view of the nuclei and thus that they have intrinsically weak BELs. We compare their properties with those of the other less-extreme candidates. We then compare the distributions of bolometric luminosities and accretion rates of these objects with theoretical models that predict weak BELs

Galaxies Probing Galaxies at High Resolution: Co-Rotating Gas Associated with a Milky Way Analog at z=0.4

We present results on gas flows in the halo of a Milky Way-like galaxy at z=0.413 based on high-resolution spectroscopy of a background galaxy. This is the first study of circumgalactic gas at high spectral resolution towards an extended background source (i.e., a galaxy rather than a quasar). Using longslit spectroscopy of the foreground galaxy, we observe spatially extended H alpha emission with circular rotation velocity v=270 km/s. Using echelle spectroscopy of the background galaxy, we detect Mg II and Fe II absorption lines at impact parameter rho=27 kpc that are blueshifted from systemic in the sense of the foreground galaxy's rotation. The strongest absorber EW(2796) = 0.90 A has an estimated column density (N_H>10^19 cm-2) and line-of-sight velocity dispersion (sigma=17 km/s) that are consistent with the observed properties of extended H I disks in the local universe. Our analysis of the rotation curve also suggests that this r=30 kpc gaseous disk is warped with respect to the stellar disk. In addition, we detect two weak Mg II absorbers in the halo with small velocity dispersions (sigma<10 km/s). While the exact geometry is unclear, one component is consistent with an extraplanar gas cloud near the disk-halo interface that is co-rotating with the disk, and the other is consistent with a tidal feature similar to the Magellanic Stream. We can place lower limits on the cloud sizes (l>0.4 kpc) for these absorbers given the extended nature of the background source. We discuss the implications of these results for models of the geometry and kinematics of gas in the circumgalactic medium.Comment: 14 pages, 6 figures, submitted to ApJ, comments welcom

Unobscured Type 2 AGNs

Type 2 AGNs with intrinsically weak broad emission lines (BELs) would be exceptions to the unified model. After examining a number of proposed candidates critically, we find that the sample is contaminated significantly by objects with BELs of strengths indicating that they actually contain intermediate-type AGNs, plus a few Compton-thick sources as revealed by extremely low ratios of X-ray to nuclear IR luminosities. We develop quantitative metrics that show two (NGC 3147 and NGC 4594) of the remaining candidates to have BELs 2-3 orders of magnitude weaker than those of typical type-1 AGNs. Several more galaxies remain as candidates to have anomalously weak BELs, but this status cannot be confirmed with the existing information. Although the parent sample is poorly defined, the two confirmed objects are well under 1% of its total number of members, showing that the absence of a BEL is possible, but very uncommon in AGN. We evaluate these two objects in detail using multi-wavelength measurements. They have little X-ray extinction with N_H < 10^21 cm^{-2}. Their IR spectra show strong silicate emission (NGC 4594) or weak aromatic features on a generally power law continuum with a suggestion of silicates in emission (NGC 3147). No polarized BEL is detected in NGC 3147. These results indicate that the two unobscured type-2 objects have circumnuclear tori that are approximately face-on. Combined with their X-ray and optical/UV properties, this behavior implies that we have an unobscured view of the nuclei and thus that they have intrinsically weak BELs. We compare their properties with those of the other less-extreme candidates. We then compare the distributions of bolometric luminosities and accretion rates of these objects with theoretical models that predict weak BELs.Comment: Accepted for publication in ApJ, 17 pages, 13 figure

Lime stabilisation for earthworks: a UK perspective

Lime stabilisation is a versatile technique applied during earthworks operations. Modern soil recycling units are much more efficient at pulverising fill material and intermixing the added binder/water than machinery available 20 years ago. While supplier innovation adds flexibility to the site working method, specifications have not been sufficiently updated to permit optimal application. This review paper details the physico-chemical changes instigated through the lime-clay soil reaction, updating previous reviews. It aims to assist scientific debate, current practitioners and future specification changes. For example, the application of the minimum 24 h mellowing periods (mandatory to UK specifications) with high reactivity, quicklime powders is concluded to cause increased air voids in the compacted fill. Increased air voids are associated with reduced long-term strength and potential volume change from water ingress, which is of particular concern for sulfate swelling. Shorter mellowing periods and/or use of hydrated lime may lesson this issue; however, a 'one size fits all' approach is discouraged in preference to site-specific methodologies refined to suit the fill material and project requirements. The discussion also summarises working methods which may lower the risk of sulfate swell and defines areas requiring further practical research

Highly Polarized Optically-Selected BL Lacertae Objects

Observations of candidate BL Lacertae objects spectroscopically selected from the Sloan Digital Sky Survey (SDSS) reveal a large fraction with high polarization (P > 3%). This result confirms that synchrotron radiation makes an important contribution to the observed optical continuum for most objects in the sample. The SDSS sample can be divided into separate categories, with objects of undetermined redshift generally having the highest optical polarization. Polarization as high as 23% and the lack of spectral features suggests that the synchrotron continuum completely dominates the spectra of these sources. The mean polarization levels observed for objects having measured redshifts is much lower, with the maximum observed polarization for this group being ~10%. The lower polarizations of these objects are reminiscent of the less spectacular polarization levels shown by BL Lac objects discovered in X-ray surveys. We find no SDSS BL Lac candidates at z > 1 with P > 3%, calling their classification as BL Lac objects into question. In addition, the existence of radio-quiet BL Lac objects is not verified since none of 10 potentially radio-weak BL Lac candidates observed are highly polarized. Regardless of whether the high-redshift and radio-weak objects are included in this optical sample, the overall levels of polarization observed are intermediate between those seen for X-ray and radio-selected BL Lac objects.Comment: 9 pages, 3 figures, 2 table

Structural Studies of West Nile Virus in Complex with Neutralizing Antibodies.

West Nile virus (WNV) is a positive strand RNA virus in the family Flaviviridae, which includes members such as dengue, Japanese encephalitis, tick-borne encephalitis, yellow fever and Hepatitis C. As with other members of the genus, it is arthropod transmitted and has recently established itself as an endemic virus in the United States. Although most infections are asymptomatic, clinical manifestations of WNV include encephalitis and death. We have been interested in investigating the nature of the immune response with particular emphasis on the role of antibodies in reducing the level of infection. We have used a combination of techniques, but primarily structure, as a tool to probe the nature of antibody-mediated virus neutralization. Our results suggest that neutralization of virus particles is more complex than originally envisioned, with multiple mechanisms utilized. Using a combination of X-ray crystallography and cryo-electron microscopy, several virus-antibody complexes have been determined at pseudo-atomic resolution. These studies suggest the following: 1) flavivirus particles exhibit dynamic motions or breathing that transiently expose cryptic epitopes; 2) although there are 180 potential binding sites for each monoclonal antibody the quasi-equivalent nature of the virion usually permits only a subset of sites to be utilized; 3) the availability of these sites, the epitope itself, and the avidity of antibody directly influence the mechanism of neutralization; and 4) particles thought to be incapable of infecting cells, so-called immature viruses, may play a critical role in immune surveillance and reactivity. The structure of the flavivirus virion and complexes of monoclonal antibodies will be presented along with data to support mechanisms antibody-mediated flavivirus neutralizatio

Human adipose derived stromal/stem cells (hASCs) protect against STZ-induced hyperglycemia; analysis of hASC-derived paracrine effectors

Adipose-derived stromal/stem cells (ASCs) ameliorate hyperglycemia in rodent models of islet transplantation and autoimmune diabetes, yet the precise human ASC (hASC)-derived factors responsible for these effects remain largely unexplored. Here, we show that systemic administration of hASCs improved glucose tolerance, preserved β cell mass, and increased β cell proliferation in streptozotocin-treated nonobese diabetic/severe combined immunodeficient mice. Coculture experiments combining mouse or human islets with hASCs demonstrated that islet viability and function were improved by hASCs following prolonged culture or treatment with proinflammatory cytokines. Analysis of hASC-derived factors revealed vascular endothelial growth factor and tissue inhibitor of metalloproteinase 1 (TIMP-1) to be highly abundant factors secreted by hASCs. Notably, TIMP-1 secretion increased in the presence of islet stress from cytokine treatment, while TIMP-1 blockade was able to abrogate in vitro prosurvival effects of hASCs. Following systemic administration by tail vein injection, hASCs were detected in the pancreas and human TIMP-1 was increased in the serum of injected mice, while recombinant TIMP-1 increased viability in INS-1 cells treated with interleukin-1beta, interferon-gamma, and tumor necrosis factor alpha. In aggregate, our data support a model whereby factors secreted by hASCs, such as TIMP-1, are able to mitigate against β cell death in rodent and in vitro models of type 1 diabetes through a combination of local paracrine as well as systemic effects

The Space Density of Intermediate-redshift, Extremely Compact, Massive Starburst Galaxies

© 2022. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the Creative Commons Attribution License, to view a copy of the license, see: https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/We present a measurement of the intrinsic space density of intermediate-redshift (z ∼ 0.5), massive (M * ∼ 1011 M ⊙), compact (R e ∼ 100 pc) starburst (ΣSFR ∼ 1000 M ⊙ yr−1 kpc−1) galaxies with tidal features indicative of them having undergone recent major mergers. A subset of them host kiloparsec-scale, > 1000 km s−1 outflows and have little indication of AGN activity, suggesting that extreme star formation can be a primary driver of large-scale feedback. The aim for this paper is to calculate their space density so we can place them in a better cosmological context. We do this by empirically modeling the stellar populations of massive, compact starburst galaxies. We determine the average timescale on which galaxies that have recently undergone an extreme nuclear starburst would be targeted and included in our spectroscopically selected sample. We find that massive, compact starburst galaxies targeted by our criteria would be selectable for ∼148−24+27 Myr and have an intrinsic space density nCS∼(1.1−0.3+0.5)×10−6Mpc−3 . This space density is broadly consistent with our z ∼ 0.5 compact starbursts being the most extremely compact and star-forming low-redshift analogs of the compact star-forming galaxies in the early universe, as well as them being the progenitors to a fraction of intermediate-redshift, post-starburst, and compact quiescent galaxies.Peer reviewe

Kinematics, Structure, and Mass Outflow Rates of Extreme Starburst Galactic Outflows

We present results on the properties of extreme gas outflows in massive ($\rm M_* \sim$10$^{11} \ \rm M_{\odot}$), compact, starburst ($\rm SFR \sim$$200 \, \rm M_{\odot} \ yr^{-1}$) galaxies at z = $0.4-0.7$ with very high star formation surface densities ($\rm \Sigma_{SFR} \sim$$2000 \,\rm M_{\odot} \ yr^{-1} \ kpc^{-2}$). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies we identify outflows with maximum velocities of$820 - 2860 \kmps. High-resolution spectroscopy allows us to measure precise column densities and covering fractions as a function of outflow velocity and characterize the kinematics and structure of the cool gas outflow phase (T \sim$10$^4 K). We find substantial variation in the absorption profiles, which likely reflects the complex morphology of inhomogeneously-distributed, clumpy gas and the intricacy of the turbulent mixing layers between the cold and hot outflow phases. There is not a straightforward correlation between the bursts in the galaxies' star formation histories and their wind absorption line profiles, as might naively be expected for starburst-driven winds. The lack of strong \mgii \ absorption at the systemic velocity is likely an orientation effect, where the observations are down the axis of a blowout. We infer high mass outflow rates of \rm \sim$50$-$2200$\rm M_{\odot} \, yr^{-1}$, assuming a fiducial outflow size of 5 kpc, and mass loading factors of$\eta\sim$5 for most of the sample.$\eta\sim$20 for two galaxies. While these values have high uncertainties, they suggest that starburst galaxies are capable of ejecting very large amounts of cool gas that will substantially impact their future evolution.Comment: Accepted for publication in The Astrophysical Journa

Ionized Gas Extended Over 40 kpc in an Odd Radio Circle Host Galaxy

A new class of extragalactic astronomical sources discovered in 2021, named Odd Radio Circles (ORCs, Norris et al. 2021), are large rings of faint, diffuse radio continuum emission spanning ~1 arcminute on the sky. Galaxies at the centers of several ORCs have photometric redshifts of z~0.3-0.6, implying physical scales of several 100 kiloparsecs in diameter for the radio emission, the origin of which is unknown. Here we report spectroscopic data on an ORC including strong [OII] emission tracing ionized gas in the central galaxy of ORC4 at z=0.4512. The physical extent of the [OII] emission is ~40 kpc in diameter, larger than expected for a typical early-type galaxy (Pandya et al, 2017) but an order of magnitude smaller than the large-scale radio continuum emission. We detect a ~200 km/s velocity gradient across the [OII] nebula, as well as a high velocity dispersion of ~180 km/s. The [OII] equivalent width (EW, ~50 Ang) is extremely high for a quiescent galaxy. The morphology, kinematics, and strength of the [OII] emission are consistent with the infall of shock ionized gas near the galaxy, following a larger-scale, outward moving shock driven by a galactic wind. Both the extended optical and radio emission, while observed on very different scales, may therefore result from the same dramatic event.Comment: 7 figures, accepted to Natur