Spatially Correlated Cluster Populations in the Outer Disk of NGC 3184

We use deep (~27.5 mag V-band point-source limiting magnitude) V- and U-band LBT imaging to study the outer disk (beyond the optical radius R_25) of the non-interacting, face-on spiral galaxy NGC 3184 (D = 11.1 Mpc; R_25 = 11.1 kpc) and find that this outer disk contains >1000 objects (or marginally-resolved 'knots') resembling star clusters with masses ~10^2 - 10^4 M_sun and ages up to ~1 Gyr. We find statistically significant numbers of these cluster-like knots extending to ~1.4 R_25, with the redder knots outnumbering bluer at the largest radii. We measure clustering among knots and find significant correlation to galactocentric radii of 1.5 R_25 for knot separations <1 kpc. The effective integrated surface brightness of this outer disk cluster population ranges from 30 - 32 mag arcsec^-2 in V. We compare the HI extent to that of the correlated knots and find that the clusters extend at least to the damped Lyman-alpha threshold of HI column density (2e20 cm^-2; 1.62 R_25). The blue knots are correlated with HI spiral structure to 1.5 R_25, while the red knots may be correlated with the outer fringes of the HI disk to 1.7 R_25. These results suggest that outer disks are well-populated, common, and long-lasting features of many nearby disk galaxies.Comment: Accepted for publication in The Astrophysical Journal. 12 pages, 10 figure

Towards an Understanding of Changing-Look Quasars: An Archival Spectroscopic Search in SDSS

The uncertain origin of the recently-discovered `changing-looking' quasar phenomenon -- in which a luminous quasar dims significantly to a quiescent state in repeat spectroscopy over ~10 year timescales -- may present unexpected challenges to our understanding of quasar accretion. To better understand this phenomenon, we take a first step to building a sample of changing-look quasars with a systematic but simple archival search for these objects in the Sloan Digital Sky Survey Data Release 12. By leveraging the >10 year baselines for objects with repeat spectroscopy, we uncover two new changing-look quasars, and a third discovered previously. Decomposition of the multi-epoch spectra and analysis of the broad emission lines suggest that the quasar accretion disk emission dims due to rapidly decreasing accretion rates (by factors of >2.5), while disfavoring changes in intrinsic dust extinction for the two objects where these analyses are possible. Broad emission line energetics also support intrinsic dimming of quasar emission as the origin for this phenomenon rather than transient tidal disruption events or supernovae. Although our search criteria included quasars at all redshifts and transitions from either quasar-like to galaxy-like states or the reverse, all of the clear cases of changing-look quasars discovered were at relatively low-redshift (z ~ 0.2 - 0.3) and only exhibit quasar-like to galaxy-like transitions.Comment: 15 pages, 8 figures. Updated to accepted versio

Noticias de Bahía Academia

El Vivero de la ECCD. Las Amenazadas Tortugas de Cerro Paloma, Isabel. El Daño de los Chivos al Volcán Alcedo. Las Colecciones del Museo de la ECCD. Chivos en Pinta, Otra Vez? Existe un Guadalupe River en Galápagos? Avistamiento de un Tirano del Este. Tomar Palabras del Pasado. ¡Es Scalesia Atractyloides! El Beagle, Bote de Investigación de la ECCD. Alcedo al Día. Exposición de Arte a Beneficio de Alcedo. Nueva Construcción. Actividad Geológica? Ciencia de Alta Tecnología. Mas Noticias Sobre Pinta. Primer Registro de la Garza Verde (Butorides Viriscens) en las Islas Galápagos. Un Vuelo sobre los Volcanes del Norte de Isabela

A direct measurement of the baryonic mass function of galaxies & implications for the galactic baryon fraction

We use both an HI-selected and an optically-selected galaxy sample to directly measure the abundance of galaxies as a function of their "baryonic" mass (stars + atomic gas). Stellar masses are calculated based on optical data from the Sloan Digital Sky Survey (SDSS) and atomic gas masses are calculated using atomic hydrogen (HI) emission line data from the Arecibo Legacy Fast ALFA (ALFALFA) survey. By using the technique of abundance matching, we combine the measured baryonic function (BMF) of galaxies with the dark matter halo mass function in a LCDM universe, in order to determine the galactic baryon fraction as a function of host halo mass. We find that the baryon fraction of low-mass halos is much smaller than the cosmic value, even when atomic gas is taken into account. We find that the galactic baryon deficit increases monotonically with decreasing halo mass, in contrast with previous studies which suggested an approximately constant baryon fraction at the low-mass end. We argue that the observed baryon fractions of low mass halos cannot be explained by reionization heating alone, and that additional feedback mechanisms (e.g. supernova blowout) must be invoked. However, the outflow rates needed to reproduce our result are not easily accommodated in the standard picture of galaxy formation in a LCDM universe.Comment: Accepted to ApJ. 45 pages (aastex), 19 figures; added references and updated fig.18 for version

News from Academy Bay

It is Scalesia atractyloides! The Marine Biology Laboratory Renaissance. The CDRS Research Vessel Beagle. Alcedo Update. Benefit Art Show Held on Santa Cruz. New Construction. Geological Activity? High Technology Science. More Pinta News. First Record of the Green Heron (Butorides viriscens) in the Galápagos Islands. Galápagos Explorer Goes Aground. A Flight Over Isabela's Northern Volcanoes

A missing high-spin molecule in the family of cyano-bridged heptanuclear heterometal complexes, [(LCuII)6FeIII(CN)6]3+, and its CoIII and CrIII analogues, accompanied in the crystal by a novel octameric water cluster

Three isostructural cyano-bridged heptanuclear complexes, [{CuII(saldmen)(H2O)}6{MIII(CN)6}](ClO4)3$\cdotp$8H2O (M = FeIII 2; CoIII, 3; CrIII 4), have been obtained by reacting the binuclear copper(II) complex, [Cu2(saldmen)2(mu-H2O)(H2O)2](ClO4)2$\cdotp$2H2O 1, with K3[Co(CN)6], K4[Fe(CN)6], and, respectively, K3[Cr(CN)6] (Hsaldmen is the Schiff base resulted from the condensation of salicylaldehyde with N,N-dimethylethylenediamine). A unique octameric water cluster, with bicyclo[2,2,2]octane-like structure, is sandwiched between the heptanuclear cations in 2, 3 and 4. The cryomagnetic investigations of compounds 2 and 4 reveal ferromagnetic couplings of the central FeIII or CrIII ions with the CuII ions (JCuFe = +0.87 cm-1, JCuCr = +30.4 cm-1). The intramolecular Cu-Cu exchange interaction in 3, across the diamagnetic cobalt(III) ion, is -0.3 cm-1. The solid-state1H-NMR spectra of compounds 2 and 3 have been investigated

Properties of Dark Matter Haloes and their Correlations: the Lesson from Principal Component Analysis

We study the correlations between the structural parameters of dark matter haloes using Principal Component Analysis (PCA). We consider a set of eight parameters, six of which are commonly used to characterize dark matter halo properties: mass, concentration, spin, shape, overdensity, and the angle ($\Phi_L$) between the major axis and the angular momentum vector. Two additional parameters (\x_{off} and $\rho_{rms}$) are used to describe the degree of `relaxedness' of the halo. We find that we can account for much of the variance of these properties with halo mass and concentration, on the one hand, and halo relaxedness on the other. Nonetheless, three principle components are usually required to account for most of the variance. We argue that halo mass is not as dominant as expected, which is a challenge for halo occupation models and semi-analytic models that assume that mass determines other halo (and galaxy) properties. In addition, we find that the angle $\Phi_L$ is not significantly correlated with other halo parameters, which may present a difficulty for models in which galaxy disks are oriented in haloes in a particular way. Finally, at fixed mass, we find that a halo's environment (quantified by the large-scale overdensity) is relatively unimportant.Comment: 14 pages, 8 figures; minor revisions; MNRAS, in pres

Measuring the kinetic power of AGN in the radio mode

(Abridged) We have studied the relationship among nuclear radio and X-ray power, Bondi rate and the kinetic luminosity of sub-Eddington active galactic nuclear (AGN) jets. Besides the recently discovered correlation between jet kinetic and Bondi power, we show that a clear correlation exists also between Eddington-scaled kinetic power and bolometric luminosity, given by: Log(L_kin/L_Edd)=0.49*Log(L_bol/L_Edd)-0.78. The measured slope suggests that these objects are in a radiatively inefficient accretion mode, and has been used to put stringent constraints on the properties of the accretion flow. We found no statistically significant correlations between Bondi power and bolometric AGN luminosity, apart from that induced by their common dependence on L_kin. Analyzing the relation between kinetic power and radio core luminosity, we are then able to determine, statistically, both the probability distribution of the mean jets Lorentz factor, peaking at \Gamma~7, and the intrinsic relation between kinetic and radio core luminosity, that we estimate as: Log(L_kin)=0.81*Log(L_R)+11.9, in good agreement with theoretical predictions of synchrotron jet models. With the aid of these findings, quantitative assessments of kinetic feedback from supermassive black holes in the radio mode will be possible based on accurate determinations of the central engine properties alone. As an example, Sgr A* may follow the correlations of radio mode AGN, based on its observed radiative output and on estimates of the accretion rate both at the Bondi radius and in the inner flow. If this is the case, the SMBH in the Galactic center is the source of ~ 5 times 10^38 ergs/s of mechanical power, equivalent to about 1.5 supernovae every 10^5 years.Comment: 13 pages, 6 figures. Accepted for publication in MNRA

The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14 happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov 2017 (this is the "post-print" and "post-proofs" version; minor corrections only from v1, and most of errors found in proofs corrected