26,234 research outputs found

    Ending Child Marriage in a Generation: What Research is Needed?

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    In recent years, the obstacles that child marriage poses to development and to the achievement of the Millennium Development Goals have been widely recognized. Varied responses to the problem have been devised. The number of programs testing different approaches to ending child marriage has grown, and many have been evaluated. We are starting to get a sense of what works and the general areas in which investing in research could make a difference.The purpose of this paper is to identify gaps in the research on child marriage in which additional investment could catalyze change. Much remains to understand about child marriage and how to influence it. By mapping out current knowledge of child marriage and the programs designed to address it, and by highlighting questions to which we do not yet know the answers, the paper is intended to generate discussion in the field and clarify what we need to know to bring an end to this deeply harmful practice.The paper also moves us closer to the development of a shared theory of change for this field: given that many organizations are now working in this area, how can their programs and related research be understood -- aligned -- in such a way that their work feeds into a single theory of change?The research gaps on their own should not drive investments in child marriage. A worthy research mandate must also be driven by programmatic and advocacy needs. The recommended areas for research are not meant to provide a definitive menu, but rather to describe the general contours of what we know and what we need to understand better

    Dwarf Galaxies with Optical Signatures of Active Massive Black Holes

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    We present a sample of 151 dwarf galaxies (10^8.5 < M_stellar < 10^9.5 Msun) that exhibit optical spectroscopic signatures of accreting massive black holes (BHs), increasing the number of known active galaxies in this stellar mass range by more than an order of magnitude. Utilizing data from the Sloan Digital Sky Survey Data Release 8 and stellar masses from the NASA-Sloan Atlas, we have systematically searched for active BHs in ~25,000 emission-line galaxies with stellar masses comparable to the Magellanic Clouds and redshifts z<0.055. Using the narrow-line [OIII]/H-beta versus [NII]/H-alpha diagnostic diagram, we find photoionization signatures of BH accretion in 136 galaxies, a small fraction of which also exhibit broad H-alpha emission. For these broad-line AGN candidates, we estimate BH masses using standard virial techniques and find a range of 10^5 < M_BH < 10^6 Msun and a median of M_BH ~ 2 x 10^5 Msun. We also detect broad H-alpha in 15 galaxies that have narrow-line ratios consistent with star-forming galaxies. Follow-up observations are required to determine if these are true type 1 AGN or if the broad H-alpha is from stellar processes. The median absolute magnitude of the host galaxies in our active sample is Mg = -18.1 mag, which is ~1-2 magnitudes fainter than previous samples of AGN hosts with low-mass BHs. This work constrains the smallest galaxies that can form a massive BH, with implications for BH feedback in low-mass galaxies and the origin of the first supermassive BH seeds.Comment: 26 pages, 15 figures, 6 tables. Accepted for publication in The Astrophysical Journa

    Active Galaxies and the Study of Black Hole Demographics

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    We discuss the critical importance of black hole mass indicators based on scaling relations in active galaxies. We highlight outstanding uncertainties in these methods and potential paths to substantial progress in the next decade.Comment: 4 pages, 1 figure, Invited review to appear in PAS

    Offset Active Galactic Nuclei as Tracers of Galaxy Mergers and Supermassive Black Hole Growth

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    Offset active galactic nuclei (AGNs) are AGNs that are in ongoing galaxy mergers, which produce kinematic offsets in the AGNs relative to their host galaxies. Offset AGNs are also close relatives of dual AGNs. We conduct a systematic search for offset AGNs in the Sloan Digital Sky Survey, by selecting AGN emission lines that exhibit statistically significant line-of-sight velocity offsets relative to systemic. From a parent sample of 18314 Type 2 AGNs at z<0.21, we identify 351 offset AGN candidates with velocity offsets of 50 km/s < |v| < 410 km/s. When we account for projection effects in the observed velocities, we estimate that 4% - 8% of AGNs are offset AGNs. We designed our selection criteria to bypass velocity offsets produced by rotating gas disks, AGN outflows, and gravitational recoil of supermassive black holes, but follow-up observations are still required to confirm our candidates as offset AGNs. We find that the fraction of AGNs that are offset candidates increases with AGN bolometric luminosity, from 0.7% to 6% over the luminosity range 43 < log(L_bol) [erg/s] < 46. If these candidates are shown to be bona fide offset AGNs, then this would be direct observational evidence that galaxy mergers preferentially trigger high-luminosity AGNs. Finally, we find that the fraction of AGNs that are offset AGN candidates increases from 1.9% at z=0.1 to 32% at z=0.7, in step with the growth in the galaxy merger fraction over the same redshift range.Comment: 14 pages, 14 figures, accepted for publication in Ap

    Oyster Reef Restoration Project for the City of Dover, Grizzle

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    This project was conducted as a contract between the City of Dover and the University of New Hampshire, with additional funding supplied by the New Hampshire Estuaries Project. The overall goal was to restore as much bottom area as possible (with available funds) of formerly productive oyster bottom in two areas, the Bellamy River and Pomeroy Cove (Piscataqua River). The restored areas were intended as a contribution to the long-term NHEP goal of restoring 20 acres of oyster bottom by 2010 (Trowbridge 2003). Five objectives were addressed: (1) site surveys, map production, and final restoration protocol development; (2) remote setting of oyster larvae; (3) bottom seeding with spat; (4) assessment of restoration success; and (5) education. Site surveys found substantial amounts of shell bottom (but only two live oysters) along a 1.2 km stretch of the Bellamy, and no oyster bottom off Pomeroy Cove. Hence, restoration efforts were designed only for the Bellamy. Spat seeding involving deposition onto the existing bottom (i.e. no bottom improvement via placement of additional hard substrate or other methods) of spat (young oysters) attached to shell substrate produced by remote setting was chosen as the primary reef restoration method. Larvae from native Great Bay oysters were set in tanks at UNH\u27s Jackson Estuarine Laboratory (JEL) in July 2005, and held on a nursery raft at JEL until reef construction in November 2005. Approximately 300,000 spat-on-shell were used to construct 12 mini reefs (total surface area ~0.1 acre) within a 1.5-acre overall restoration area. On 26 July 2006 (9 months post-construction), 32,000 live oysters remained on the mini-reefs and no live oysters were found in adjacent natural reef areas. When considering only the 0.1 acre area covered by the mini-reefs, live oysters occurred at 64/m2, which is similar to oyster densities in other areas in Great Bay. When considering the entire 1.5 acre restoration area, live oysters were at ~4/m2. The entire 1.5-acre area was considered restored in the short-term. Longer-term restoration success will be dependent upon successful natural recruitment to the mini reefs as well as the adjacent bottom areas. Diver observations in July 2006 indicated that very little oyster shell (other than what was put out with the spat in November 2005) remained in the restoration area. This suggests that longer-term restoration success may require placement of additional shell onto the bottom. Longer-term success will be assessed by future sampling as funds become available
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