Science.gov

Sample records for disturbed galaxies evidence

  1. Kinematic Disturbances in Rotation Curves among 89 Virgo Galaxies

    NASA Astrophysics Data System (ADS)

    Rubin, V. C.; Waterman, A. H.; Kenney, J. D. P.

    1999-05-01

    For 89 (mostly) spirals in the Virgo cluster, we have obtained optical long-slit spectra of the ionized gas. We find: (1) 50% of the Virgo galaxies we observed have regular rotation patterns; 50% exhibit kinematic disturbances ranging from mild to major. Velocity complexities are consistent with those resulting from tidal encounters or accretion. Since kinematic disturbances will to fade within ~ 1Gyr, many Virgo galaxies have experienced several significant kinematic disturbances during their lifetimes. (2) There is no strong correlation of rotation curve complexity with Hubble type, galaxy luminosity, local galaxy density, or HI deficiency. (3) There is a remarkable difference in the distribution of galaxy systemic velocity for galaxies in the two classes. Galaxies with regular rotation patterns show a flat distribution with velocities ranging from V = -300 km/sec to V = +2500 km/sec; galaxies with disturbed kinematics have a Gaussian distribution which peaks at V = +1172+/-100 km/sec, near the cluster mean velocity. This distribution is virtually identical to the distribution of systemic velocities for elliptical galaxies in Virgo. However, disturbed spirals are less centrally concentrated than the ellipticals and those near the periphery are more likely to have the mean cluster velocity. We suggest that spirals with disturbed kinematics are preferentially on radial orbits, which bring them to the denser core, where tidal interactions are strong and/or more common. However, because they spend most of their time near apocenter, we observe them near the periphery of the cluster. Some may be falling into the core for the first time. For a non-virialized cluster like Virgo, galaxies may encounter either local (nearby galaxies) or global (cluster related) interactions. These interactions may alter the galaxy morphology, and may play a role in driving the Virgo cluster toward dynamical equilibrium.

  2. Kinematic Disturbances in Optical Rotation Curves among 89 Virgo Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Rubin, Vera C.; Waterman, Andrew H.; Kenney, Jeffrey D. P.

    1999-07-01

    For 89 galaxies, mostly spirals, in the Virgo Cluster region, we have obtained optical long-slit major-axis spectra of the ionized gas. We find the following: (1) One-half of the Virgo galaxies we observed have regular rotation patterns, while the other half exhibit kinematic disturbances ranging from mild to major. Velocity complexities are generally consistent with those resulting from tidal encounters or accretion events. Since kinematic disturbances are expected to fade within ~10^9 yr, many Virgo galaxies have experienced several significant kinematic disturbances during their lifetimes. (2) There is no strong correlation of rotation curve complexity with Hubble type, with galaxy luminosity, with local galaxy density, or with H I deficiency. (3) A few Virgo galaxies have ionized gas of limited extent, with velocities exceptionally low for their luminosities. In these galaxies the gas must be not rotationally supported. (4) There is a remarkable difference in the distribution of galaxy systemic velocity for galaxies with regular rotation curves and galaxies with disturbed rotation curves. Galaxies with regular rotation patterns show a flat distribution with velocities ranging from V_0=-300 km s^-1 to V_0=+2500 km s^-1 galaxies with disturbed kinematics have a Gaussian distribution that peaks at V_0=+1172+/-100 km s^-1, close to the cluster mean velocity. This latter distribution is virtually identical to the distribution of systemic velocity for elliptical galaxies in Virgo. However, disturbed galaxies are less concentrated to the cluster core than are the ellipticals; those near the periphery have velocities closer to the mean cluster velocity. Thus, spirals with disturbed kinematics are preferentially on radial orbits, which bring them to the denser core, where tidal interactions are strong and/or more common. Because they spend much time near apocenter, we observe them near the cluster periphery. Some may be falling into the core for the first time. These

  3. ENHANCED NITROGEN IN MORPHOLOGICALLY DISTURBED BLUE COMPACT GALAXIES AT 0.20 < z < 0.35: PROBING GALAXY MERGING FEATURES

    SciTech Connect

    Chung, Jiwon; Rey, Soo-Chang; Yeom, Bum-Suk; Yi, Wonhyeong; Sung, Eon-Chang; Kyeong, Jaemann; Humphrey, Andrew E-mail: screy@cnu.ac.kr

    2013-04-10

    We present a study of correlations between the elemental abundances and galaxy morphologies of 91 blue compact galaxies (BCGs) at z = 0.20-0.35 with Sloan Digital Sky Survey (SDSS) DR7 data. We classify the morphologies of the galaxies as either ''disturbed'' or ''undisturbed'' by visual inspection of the SDSS images, and using the Gini coefficient and M{sub 20}. We derive oxygen and nitrogen abundances using the T{sub e} method. We find that a substantial fraction of BCGs with disturbed morphologies, indicative of merger remnants, show relatively high N/O and low O/H abundance ratios. The majority of the disturbed BCGs exhibit higher N/O values at a given O/H value compared to the morphologically undisturbed galaxies, implying more efficient nitrogen enrichment in disturbed BCGs. We detect Wolf-Rayet (WR) features in only a handful of the disturbed BCGs, which appears to contradict the idea that WR stars are responsible for high nitrogen abundance. Combining these results with Galaxy Evolution Explorer GR6 ultraviolet (UV) data, we find that the majority of the disturbed BCGs show systematically lower values of the H{alpha} to near-UV star formation rate ratio. The equivalent width of the H{beta} emission line is also systematically lower in the disturbed BCGs. Based on these results, we infer that disturbed BCGs have undergone star formation over relatively longer timescales, resulting in a more continuous enrichment of nitrogen. We suggest that this correlation between morphology and chemical abundances in BCGs is due to a difference in their recent star formation histories.

  4. Sleep disturbances as an evidence-based suicide risk factor.

    PubMed

    Bernert, Rebecca A; Kim, Joanne S; Iwata, Naomi G; Perlis, Michael L

    2015-03-01

    Increasing research indicates that sleep disturbances may confer increased risk for suicidal behaviors, including suicidal ideation, suicide attempts, and death by suicide. Despite increased investigation, a number of methodological problems present important limitations to the validity and generalizability of findings in this area, which warrant additional focus. To evaluate and delineate sleep disturbances as an evidence-based suicide risk factor, a systematic review of the extant literature was conducted with methodological considerations as a central focus. The following methodologic criteria were required for inclusion: the report (1) evaluated an index of sleep disturbance; (2) examined an outcome measure for suicidal behavior; (3) adjusted for presence of a depression diagnosis or depression severity, as a covariate; and (4) represented an original investigation as opposed to a chart review. Reports meeting inclusion criteria were further classified and reviewed according to: study design and timeframe; sample type and size; sleep disturbance, suicide risk, and depression covariate assessment measure(s); and presence of positive versus negative findings. Based on keyword search, the following search engines were used: PubMed and PsycINFO. Search criteria generated N = 82 articles representing original investigations focused on sleep disturbances and suicide outcomes. Of these, N = 18 met inclusion criteria for review based on systematic analysis. Of the reports identified, N = 18 evaluated insomnia or poor sleep quality symptoms, whereas N = 8 assessed nightmares in association with suicide risk. Despite considerable differences in study designs, samples, and assessment techniques, the comparison of such reports indicates preliminary, converging evidence for sleep disturbances as an empirical risk factor for suicidal behaviors, while highlighting important, future directions for increased investigation. PMID:25698339

  5. Non-parametric analysis of the rest-frame UV sizes and morphological disturbance amongst L* galaxies at 4 < z < 8

    NASA Astrophysics Data System (ADS)

    Curtis-Lake, E.; McLure, R. J.; Dunlop, J. S.; Rogers, A. B.; Targett, T.; Dekel, A.; Ellis, R. S.; Faber, S. M.; Ferguson, H. C.; Grogin, N. A.; Kocevski, D. D.; Koekemoer, A. M.; Lai, K.; Mármol-Queraltó, E.; Robertson, B. E.

    2016-03-01

    We present the results of a study investigating the sizes and morphologies of redshift 4 < z < 8 galaxies in the CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) GOODS-S (Great Observatories Origins Deep Survey southern field), HUDF (Hubble Ultra-Deep Field) and HUDF parallel fields. Based on non-parametric measurements and incorporating a careful treatment of measurement biases, we quantify the typical size of galaxies at each redshift as the peak of the lognormal size distribution, rather than the arithmetic mean size. Parametrizing the evolution of galaxy half-light radius as r50 ∝ (1 + z)n, we find n = -0.20 ± 0.26 at bright UV-luminosities (0.3L*(z = 3) < L < L*) and n = -0.47 ± 0.62 at faint luminosities (0.12L* < L < 0.3L*). Furthermore, simulations based on artificially redshifting our z ˜ 4 galaxy sample show that we cannot reject the null hypothesis of no size evolution. We show that this result is caused by a combination of the size-dependent completeness of high-redshift galaxy samples and the underestimation of the sizes of the largest galaxies at a given epoch. To explore the evolution of galaxy morphology we first compare asymmetry measurements to those from a large sample of simulated single Sérsic profiles, in order to robustly categorize galaxies as either `smooth' or `disturbed'. Comparing the disturbed fraction amongst bright (M1500 ≤ -20) galaxies at each redshift to that obtained by artificially redshifting our z ˜ 4 galaxy sample, while carefully matching the size and UV-luminosity distributions, we find no clear evidence for evolution in galaxy morphology over the redshift interval 4 < z < 8. Therefore, based on our results, a bright (M1500 ≤ -20) galaxy at z ˜ 6 is no more likely to be measured as `disturbed' than a comparable galaxy at z ˜ 4, given the current observational constraints.

  6. How are quasars fueled? Simulating interstellar gas in tidally disturbed galaxies

    NASA Technical Reports Server (NTRS)

    Byrd, Gene G.

    1986-01-01

    Whether gravitational tides from companions trigger global instabilities in spiral galaxy disks and thus rapid flows of gas into the nucleus to fuel activity is investigated. An n-body computer program is used to simulate the disk of the spiral galaxy within a much more stable, high-velocity dispersion spherical halo. Under sufficient perturbation, the disk undergoes violent distortions due to the disturber and its self-gravitation. The tidal action of companions was simulated and the tidal strengths at which the instabilities appear to match those of the observed companions of Seyferts and quasars was shown. With the additional modifications planned, the gas flow will be more realistically simulated to compare with observations (e.g., colors, velocity fields) of active galaxies.

  7. Galaxy Zoo: Evidence for rapid, recent quenching within a population of AGN host galaxies

    NASA Astrophysics Data System (ADS)

    Smethurst, R. J.; Lintott, C. J.; Simmons, B. D.; Schawinski, K.; Bamford, S. P.; Cardamone, C. N.; Kruk, S. J.; Masters, K. L.; Urry, C. M.; Willett, K. W.; Wong, O. I.

    2016-09-01

    We present a population study of the star formation history of 1244 Type 2 AGN host galaxies, compared to 6107 inactive galaxies. A Bayesian method is used to determine individual galaxy star formation histories, which are then collated to visualise the distribution for quenching and quenched galaxies within each population. We find evidence for some of the Type 2 AGN host galaxies having undergone a rapid drop in their star formation rate within the last 2 Gyr. AGN feedback is therefore important at least for this population of galaxies. This result is not seen for the quenching and quenched inactive galaxies whose star formation histories are dominated by the effects of downsizing at earlier epochs, a secondary effect for the AGN host galaxies. We show that histories of rapid quenching cannot account fully for the quenching of all the star formation in a galaxy's lifetime across the population of quenched AGN host galaxies, and that histories of slower quenching, attributed to secular (non-violent) evolution, are also key in their evolution. This is in agreement with recent results showing both merger-driven and non-merger processes are contributing to the co-evolution of galaxies and supermassive black holes. The availability of gas in the reservoirs of a galaxy, and its ability to be replenished, appear to be the key drivers behind this co-evolution.

  8. Young tidal dwarf galaxies around the gas-rich disturbed lenticular NGC 5291

    NASA Astrophysics Data System (ADS)

    Duc, P.-A.; Mirabel, I. F.

    1998-05-01

    NGC 5291 is an early type galaxy at the edge of the cluster Abell 3574 which drew the attention because of the unusual high amount of atomic gas ( ~ 5 x 10(10) {M_{\\odot}}) found associated to it. The HI is distributed along a huge and fragmented ring, possibly formed after a tidal interaction with a companion galaxy. We present multi-slit optical spectroscopic observations and optical/near-infrared images of the system. We show that NGC 5291 is a LINER galaxy exhibiting several remnants of previous merging events, in particular a curved dust lane and a counter-rotation of the gas with respect to the stars. The atomic hydrogen has undoubtly an external origin and was probably accreted by the galaxy from a gas-rich object in the cluster. It is unlikely that the HI comes from the closest companion of NGC 5291, the so-called ``Seashell'' galaxy, which appears to be a fly-by object at a velocity greater than 400 km s(-1) . We have analyzed the properties of 11 optical counterparts to the clumps observed in the HI ring. The brightest knots show strong similarities with classical blue compact dwarf galaxies. They are dominated by active star forming regions; their most recent starburst is younger than 5 Myr; we did not find evidences for the presence of an old underlying stellar population. NGC 5291 appears to be a maternity of extremely young objects most probably forming their first generation of stars. Born in pre-enriched gas clouds, these recycled galaxies have an oxygen abundance which is higher than BCDGs ({Z_{\\odot}}/3 on average) and which departs from the luminosity-metallicity relation observed for typical dwarf and giant galaxies. We propose this property as a tool to identify tidal dwarf galaxies (TDGs) among the dwarf galaxy population. Several TDGs in NGC 5291 exhibit strong velocity gradients in their ionized gas and may already be dynamically independent galaxies. Based on observations collected at the European Southern Observatory, La Silla, Chile

  9. Kinematic evidence of satellite galaxy populations in the potential wells of first-ranked cluster galaxies

    SciTech Connect

    Cowie, L.L.; Hu, E.M.

    1986-06-01

    The velocities of 38 centrally positioned galaxies (r much less than 100 kpc) were measured relative to the velocity of the first-ranked galaxy in 14 rich clusters. Analysis of the velocity distribution function of this sample and of previous data shows that the population cannot be fit by a single Gaussian. An adequate fit is obtained if 60 percent of the objects lie in a Gaussian with sigma = 250 km/s and the remainder in a population with sigma = 1400 km/s. All previous data sets are individually consistent with this conclusion. This suggests that there is a bound population of galaxies in the potential well of the central galaxy in addition to the normal population of the cluster core. This is taken as supporting evidence for the galactic cannibalism model of cD galaxy formation. 14 references.

  10. Kinematic evidence of satellite galaxy populations in the potential wells of first-ranked cluster galaxies

    NASA Technical Reports Server (NTRS)

    Cowie, L. L.; Hu, E. M.

    1986-01-01

    The velocities of 38 centrally positioned galaxies (r much less than 100 kpc) were measured relative to the velocity of the first-ranked galaxy in 14 rich clusters. Analysis of the velocity distribution function of this sample and of previous data shows that the population cannot be fit by a single Gaussian. An adequate fit is obtained if 60 percent of the objects lie in a Gaussian with sigma = 250 km/s and the remainder in a population with sigma = 1400 km/s. All previous data sets are individually consistent with this conclusion. This suggests that there is a bound population of galaxies in the potential well of the central galaxy in addition to the normal population of the cluster core. This is taken as supporting evidence for the galactic cannibalism model of cD galaxy formation.

  11. The dark side of galaxy colour: evidence from new SDSS measurements of galaxy clustering and lensing

    SciTech Connect

    Hearin, Andrew P.; Watson, Douglas F.; Becker, Matthew R.; Reyes, Reinabelle; Berlind, Andreas A.; Zentner, Andrew R.

    2014-08-12

    The age matching model has recently been shown to predict correctly the luminosity L and g-r color of galaxies residing within dark matter halos. The central tenet of the model is intuitive: older halos tend to host galaxies with older stellar populations. In this paper, we demonstrate that age matching also correctly predicts the g-r color trends exhibited in a wide variety of statistics of the galaxy distribution for stellar mass M* threshold samples. In particular, we present new measurements of the galaxy two-point correlation function and the galaxy-galaxy lensing signal as a function of M* and g-r color from the Sloan Digital Sky Survey, and show that age matching exhibits remarkable agreement with these and other statistics of low-redshift galaxies. In so doing, we also demonstrate good agreement between the galaxy-galaxy lensing observed by SDSS and the signal predicted by abundance matching, a new success of this model. We describe how age matching is a specific example of a larger class of Conditional Abundance Matching models (CAM), a theoretical framework we introduce here for the first time. CAM provides a general formalism to study correlations at fixed mass between any galaxy property and any halo property. The striking success of our simple implementation of CAM provides compelling evidence that this technique has the potential to describe the same set of data as alternative models, but with a dramatic reduction in the required number of parameters. CAM achieves this reduction by exploiting the capability of contemporary N-body simulations to determine dark matter halo properties other than mass alone, which distinguishes our model from conventional approaches to the galaxy-halo connection.

  12. Extensive gaseous haloes surrounding giant elliptical galaxies - Evidence from depolarization in radio galaxies

    NASA Astrophysics Data System (ADS)

    Strom, R. G.; Jaegers, W. J.

    1988-04-01

    Radio polarization measurements have been used to investigate large scale gaseous components associated with some thirteen double radio sources. At 49 cm a significant proportion of the bridge emission, roughly centered on the parent galaxy, is invariably found to be unpolarized. The authors present evidence that this lack of polarization at long wavelengths is the result of differential Faraday rotation in a large scale halo associated with the central (usually elliptical) galaxy. The haloes, which extend beyond 100 kpc, appear to be the outer envelopes of hot gas such as that observed in the form of extended X-ray emission associated with a number of nearby early-type galaxies.

  13. Galaxy pairs in deep HST images: Evidence for evolution in the galaxy merger rate

    NASA Technical Reports Server (NTRS)

    Burkey, Jordan M.; Keel, William C.; Windhorst, Rogier A.; Franklin, Barbara E.

    1994-01-01

    We use four deep serendipitous fields observed with the Hubble Space Telescope (HST) Wide-Field Camera to constrain the rate of galaxy merging between the current epoch and z approximately equals 0.7. Since most mergers occur between members of bound pairs, the merger rate is given to a good approximation by (half) the rate of disappearance of galaxies in pairs. An objective criterion for pair membership shows that 34% +/- 9% of our HST galaxies with I = 18-22 belong to pairs, compared to 7% locally. This means that about 13% of the galaxy population has disappeared due to merging in the cosmic epoch corresponding to this magnitude interval (or 0.1 approximately less than z approximately less than 0.7). Our pair fraction is a lower limit: correction for pair members falling below our detection threshold might raise the fraction to approximately 50%. Since we address only two-galaxy merging, these values do not include physical systems of higher multiplicity. Incorporating I-band field-galaxy redshift distributions, the pair fraction grows with redshift as alpha(1 + z)(exp 3.5 +/- 0.5) and the merger rate as (1 + z)(exp 2.5 +/- 0.5). This may have significant implications for the interpretation of galaxy counts (disappearance of faint blue galaxies), the cosmological evolution of faint radio sources and quasars (which evolve approximately as (1 + z)(exp 3), the similarity in the power law is necessary but not sufficient evidence for a causal relation), statistics of QSO companions, the galaxy content in distant clusters, and the merging history of a 'typical' galaxy.

  14. CO in Hickson compact group galaxies with enhanced warm H2 emission: Evidence for galaxy evolution?

    NASA Astrophysics Data System (ADS)

    Lisenfeld, U.; Appleton, P. N.; Cluver, M. E.; Guillard, P.; Alatalo, K.; Ogle, P.

    2014-10-01

    Context. Galaxies in Hickson Compact Groups (HCGs) are believed to experience morphological transformations from blue, star-forming galaxies to red, early-type galaxies. Galaxies with a high ratio between the luminosities of the warm H2 to the 7.7 μm PAH emission (so-called Molecular Hydrogen Emission Galaxies, MOHEGs) are predominantly in an intermediate phase, the green valley. Their enhanced H2 emission suggests that the molecular gas is affected in the transition. Aims: We study the properties of the molecular gas traced by CO in galaxies in HCGs with measured warm H2 emission in order to look for evidence of the perturbations affecting the warm H2 in the kinematics, morphology and mass of the molecular gas. Methods: We observed the CO(1-0) emission of 20 galaxies in HCGs and complemented our sample with 11 CO(1-0) spectra from the literature. Most of the galaxies have measured warm H2 emission, and 14 of them are classified as MOHEGs. We mapped some of these galaxies in order to search for extra-galactic CO emission. We analyzed the molecular gas mass derived from CO(1-0), MH2, and its kinematics, and then compared it to the mass of the warm molecular gas, the stellar mass and star formation rate (SFR). Results: Our results are the following. (i) The mass ratio between the CO-derived and the warm H2 molecular gas is in the same range as found for field galaxies. (ii) Some of the galaxies, mostly MOHEGs, have very broad CO linewidths of up to 1000 km s-1 in the central pointing. The line shapes are irregular and show various components. (iii) In the mapped objects we found asymmetric distributions of the cold molecular gas. (iv) The star formation efficiency (=SFR/MH2) of galaxies in HCGs is very similar to isolated galaxies. No significant difference between MOHEGs and non-MOHEGs or between early-type and spiral galaxies has been found. In a few objects the SFE is significantly lower, indicating the presence of molecular gas that is not actively forming stars

  15. Evidence for Tides and Interactions in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Conselice, C. J.; Gallagher, J. S.

    1997-12-01

    We present preliminary results of a search for tidally distorted, or interacting galaxies in the galaxy clusters: Abell 2199, AWM 5, AWM 3, the Coma and Perseus clusters. This is part of a large study to determine the nature of small-scale structure in galaxy clusters of various morphologies. Our B and R band observations were made with the CCD imager on the WIYN 3.5-m telescope, and typically have an angular resolution of 1 arcsec or better. We are able to classify all of the observed structures into seven different types. These include: Galaxy Interactions, Multiple Galaxies, Tailed Galaxies, Dwarf Galaxy Groups, Galaxy Aggregates, Distorted Galaxies, and Line Galaxies. We present examples of objects in these categories and conclude that interactions that perturb individual galaxies are common in clusters of galaxies, despite the high relative random velocities between cluster members.

  16. Modeling mountain pine beetle disturbance in Glacier National Park using multiple lines of evidence

    USGS Publications Warehouse

    Assal, Timothy; Sibold, Jason

    2013-01-01

    Temperate forest ecosystems are subject to various disturbances which contribute to ecological legacies that can have profound effects on the structure of the ecosystem. Impacts of disturbance can vary widely in extent, duration and severity over space and time. Given that global climate change is expected to increase rates of forest disturbance, an understanding of these events are critical in the interpretation of contemporary forest patterns and those of the near future. We seek to understand the impact of the 1970s mountain pine beetle outbreak on the landscape of Glacier National Park and investigate any connection between this event and subsequent decades of extensive wildfire. The lack of spatially explicit data on the mountain pine beetle disturbance represents a major data gap and inhibits our ability to test for correlations between outbreak severity and fire severity. To overcome this challenge, we utilized multiple lines of evidence to model forest canopy mortality as a proxy for outbreak severity. We used historical aerial and landscape photos, reports, aerial survey data, a six year collection of Landsat imagery and abiotic data in combination with regression analysis. The use of remotely sensed data is critical in large areas where subsequent disturbance (fire) has erased some of the evidence from the landscape. Results indicate that this method is successful in capturing the spatial heterogeneity of the outbreak in a topographically complex landscape. Furthermore, this study provides an example on the use of existing data to reduce levels of uncertainty associated with an historic disturbance.

  17. Evidence of bar-induced secular evolution in the inner regions of stellar discs in galaxies: what shapes disc galaxies?

    NASA Astrophysics Data System (ADS)

    Kim, Taehyun; Gadotti, Dimitri A.; Athanassoula, E.; Bosma, Albert; Sheth, Kartik; Lee, Myung Gyoon

    2016-11-01

    We present evidence of bar-induced secular evolution in galactic discs using 3.6 μm images of nearby galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G). We find that among massive galaxies (M*/M⊙ > 1010), longer bars tend to reside in inner discs having a flatter radial profile. Such galaxies show a light deficit in the disc surrounding the bar, within the bar radius and often show a Θ-shaped morphology. We quantify this deficit and find that among all galaxies explored in this study (with 109 < M*/M⊙ < 1011), galaxies with a stronger bar (i.e. longer and/or with a higher Bar/T) show a more pronounced deficit. We also examine simulation snapshots to confirm and extend results by Athanassoula and Misiriotis, showing that as bars evolve they become longer, while the light deficit in the disc becomes more pronounced. Theoretical studies have predicted that, as a barred galaxy evolves, the bar captures disc stars in its immediate neighbourhood so as to make the bar longer, stronger and thinner. Hence, we claim that the light deficit in the inner disc is produced by bars, which thus take part in shaping the mass distribution of their host galaxies.

  18. Evidence for Tidal Interactions and Mergers as the Origin of Galaxy Morphology Evolution in Compact Groups

    NASA Astrophysics Data System (ADS)

    Coziol, R.; Plauchu-Frayn, I.

    2007-06-01

    We present the results of a morphological study based on NIR images of 25 galaxies, with different levels of nuclear activity (star formation or AGN), in eight compact groups (CGs) of galaxies. We independently perform two different analyses: a study of the deviations of the isophotal levels from pure ellipses and a study of morphological asymmetries. The results yielded by the two analyses are highly consistent. For the first time, it is possible to show that deviations from pure ellipses are produced by inhomogeneous stellar mass distributions related to galaxy interactions and mergers. We find evidence of mass asymmetries in 74% of the galaxies in our sample. In 59% of these cases, the asymmetries come in pairs and are consistent with tidal effects produced by the proximity of companion galaxies. The symmetric galaxies are generally small in size or mass and inactive, and have an early-type morphology. They may have already lost their gas and least-attached envelope of stars to their more massive companions. In 20% of the galaxies we find evidence for cannibalism: a big galaxy swallowing a smaller companion. In 36% of the early-type galaxies the color gradient is positive (blue nucleus) or flat. Summing up these results, as much as 52% of the galaxies in our sample could show evidence of an ongoing or past merger. Our observations also suggest that galaxies in CGs merge more frequently under ``dry'' conditions (that is, once they have lost most of their gas). The high frequency of interacting and merging galaxies observed in our study is consistent with the bias of our sample toward CGs of type B, which represent the most active phase in the evolution of the groups. In these groups we also find a strong correlation between asymmetries and nuclear activity in early-type galaxies. This correlation allows us to identify tidal interactions and mergers as the cause of galaxy morphology transformation in CGs.

  19. Galaxies

    SciTech Connect

    Not Available

    1981-01-01

    Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented.

  20. Morphologically Disturbed Massive Galaxies: Nature and Evolution During 0.6 < z < 2.5 in the CANDELS UDS and GOODS-S Fields

    NASA Astrophysics Data System (ADS)

    Cook, Joshua S.; McIntosh, Daniel H.; Rizer, Zachary; Kartaltepe, Jeyhan S.; Koekemoer, Anton M.; Lotz, Jennifer; Conselice, Christopher; Hopkins, Philip F.; Wuyts, Stijn; Peth, Michael; Barro, Guillermo; Candels Collaboration

    2015-01-01

    Merging is predicted to be an important process in the early and turbulent assembly of massive galaxies. These violent encounters heavily impact galaxy morphology and structure. As such, the evolution of morphologically disturbed systems may help constrain the relative importance of merging, the answer to which is largely debated especially at higher redshifts. Disagreements between studies however, may be attributed to the various methods used to identify merging galaxies such as visual or quantitative classifications based on different rest-frame wavelengths. Using a new comprehensive catalog of visual rest-frame optical classifications based on HST/WFC3+ACS imaging from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS), we compare the nature and evolution of merging and highly disturbed galaxy subsamples within the UDS and GOODS-S fields. We limit our sample for completeness to high-mass objects (Mstar > 1e10 Msun) with redshifts between 0.6 < z < 2.5. Most disturbed galaxies are star-forming and two-thirds have masses under 3e10 Msun. We note that one-third appear to be neither interacting nor merging, rather they are isolated and visually disk-like. Under the assumption that many disturbed or unusual morphologies are related to merging, we compare visually-selected subsamples to merger selections based on two popular quantitative methods (Gini-M20 and CAS). We find that all selections produce similar fractions across our redshift range, but the individual galaxies making up the respective fractions are often different. This may indicate that different classification methods are preferentially selecting objects undergoing either different processes such as major merging, minor merging and violent disk instabilities, or different stages of the same process.

  1. Evidence for Evolution in the Galaxy Merger Rate

    NASA Astrophysics Data System (ADS)

    Franklin, Barbara E.; Windhorst, Rogier A.; Burkey, Jordan M.; Keel, William C.

    1993-12-01

    We use a set of four deep Cycle 1+2 fields with the HST Wide-Field Camera to constrain the rate of galaxy merging between the current epoch and approximately z=0.7. These fields were selected around weak radio sources not in rich or poor clusters so as to not bias these studies. Since most mergers occur between members of bound pairs, the merger rate is given by (half) the rate of disappearance of galaxy pairs. Using an objective criterion for pair membership, we find that more than 34% of galaxies in the magnitude range I=18-22 mag belong to pairs, while careful study of nearby comparison samples shows that only 7% of local galaxies belong to pairs. Hence, about 13% of the galaxy population has disappeared to merging in the cosmic epoch corresponding to this magnitude interval (or 0.1<= z<=0.7). This pair fraction is a lower limit, since correction for pairs in which one member falls below our detection threshold would raise the fraction of pair members with I=18---22 mag to about 50%. (we do not include physical system of higher multiplicity in these values). Hence, the number of galaxy pairs has dropped significantly between z ~ 0.7 and the current epoch. When using the best available I-band field galaxy redshift distributions, the HST pair-fraction grows with redshift as ~ (1+z)(3.0-3.5) , quite consistent with the expected evolution in the merger-rate from the decrease in comoving volume (~ (1+z)(3) ). This result has very significant implications for the interpretation of the ground-based galaxy counts (it explains the disappearance of faint blue galaxies), the cosmological evolution of faint radio sources and quasars (explains why these should indeed evolve as ~ (1+z)(3) ), the statistics of QSO companions, the galaxy content in distant clusters, and the merging history of a ``typical" galaxy. This work was supported by STScI grants GO-2405.*-87A and GO-3545.*-91A (to WCK and RAW) and in part through EPSCoR grant EHR-9108761 (to WCK).

  2. GALAXY SPIN ALIGNMENT IN FILAMENTS AND SHEETS: OBSERVATIONAL EVIDENCE

    SciTech Connect

    Tempel, Elmo; Libeskind, Noam I. E-mail: nlibeskind@aip.de

    2013-10-01

    The properties of galaxies are known to be affected by their environment. One important question is how their angular momentum reflects the surrounding cosmic web. We use the Sloan Digital Sky Survey to investigate the spin axes of spiral and elliptical galaxies relative to their surrounding filament/sheet orientations. To detect filaments, a marked point process with interactions (the {sup B}isous model{sup )} is used. Sheets are found by detecting 'flattened' filaments. The minor axes of ellipticals are found to be preferentially perpendicular to hosting filaments. A weak correlation is found with sheets. These findings are consistent with the notion that elliptical galaxies formed via mergers, which predominantly occurred along the filaments. The spin axis of spiral galaxies is found to align with the host filament, with no correlation between spiral spin and sheet normal. When examined as a function of distance from the filament axis, a much stronger correlation is found in the outer parts, suggesting that the alignment is driven by the laminar infall of gas from sheets to filaments. When compared with numerical simulations, our results suggest that the connection between dark matter halo and galaxy spin is not straightforward. Our results provide an important input to the understanding of how galaxies acquire their angular momentum.

  3. CONNECTIONS BETWEEN GALAXY MERGERS AND STARBURST: EVIDENCE FROM THE LOCAL UNIVERSE

    SciTech Connect

    Luo, Wentao; Yang, Xiaohu; Zhang, Youcai E-mail: xyang@sjtu.edu.cn

    2014-07-01

    Major mergers and interactions between gas-rich galaxies with comparable masses are thought to be the main triggers of starburst. In this work, we study, for a large stellar mass range, the interaction rate of the starburst galaxies in the local universe. We focus independently on central and satellite star forming galaxies extracted from the Sloan Digital Sky Survey. Here the starburst galaxies are selected in the star formation rate (SFR) stellar mass plane with SFRs five times larger than the median value found for ''star forming'' galaxies of the same stellar mass. Through visual inspection of their images together with close companions determined using spectroscopic redshifts, we find that ∼50% of the ''starburst'' populations show evident merger features, i.e., tidal tails, bridges between galaxies, double cores, and close companions. In contrast, in the control sample we selected from the normal star forming galaxies, only ∼19% of galaxies are associated with evident mergers. The interaction rates may increase by ∼5% for the starburst sample and 2% for the control sample if close companions determined using photometric redshifts are considered. The contrast of the merger rate between the two samples strengthens the hypothesis that mergers and interactions are indeed the main causes of starburst.

  4. Galaxy NGC5474

    NASA Technical Reports Server (NTRS)

    2003-01-01

    NASA's Galaxy Evolution Explorer took this ultraviolet color image of the galaxy NGC5474 on June 7, 2003. NGC5474 is located 20 million light-years from Earth and is within a group of galaxies dominated by the Messier 101 galaxy. Star formation in this galaxy shows some evidence of a disturbed spiral pattern, which may have been induced by tidal interactions with Messier 101.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  5. Evidence for Multiple Mergers among Ultraluminous Infrared Galaxies: Remnants of Compact Groups?

    PubMed

    Borne; Bushouse; Lucas; Colina

    2000-02-01

    In a large sample of ultraluminous infrared galaxies (ULIRGs) imaged with the Hubble Space Telescope, we have identified a significant subsample that shows evidence for multiple mergers. The evidence is seen among two classes of ULIRGs: (1) those with multiple remnant nuclei in their core, sometimes accompanied by a complex system of tidal tails, and (2) those that are in fact dense groupings of interacting (soon-to-merge) galaxies. We conservatively estimate that, in the redshift range 0.05galaxies (see Hickson). An evolutionary progression is consistent with the results: from compact groups to pairs to ULIRGs to elliptical galaxies. The last step follows the blowout of gas and dust from the ULIRG. PMID:10622759

  6. Submillimeter Galaxies at z ~ 2: Evidence for Major Mergers and Constraints on Lifetimes, IMF, and CO-H2 Conversion Factor

    NASA Astrophysics Data System (ADS)

    Tacconi, L. J.; Genzel, R.; Smail, I.; Neri, R.; Chapman, S. C.; Ivison, R. J.; Blain, A.; Cox, P.; Omont, A.; Bertoldi, F.; Greve, T.; Förster Schreiber, N. M.; Genel, S.; Lutz, D.; Swinbank, A. M.; Shapley, A. E.; Erb, D. K.; Cimatti, A.; Daddi, E.; Baker, A. J.

    2008-06-01

    We report subarcsecond resolution IRAM PdBI millimeter CO interferometry of four z ~ 2 submillimeter galaxies (SMGs), and sensitive CO(3-2) flux limits toward three z ~ 2 UV/optically selected star-forming galaxies. The new data reveal for the first time spatially resolved CO gas kinematics in the observed SMGs. Two of the SMGs show double or multiple morphologies, with complex, disturbed gas motions. The other two SMGs exhibit CO velocity gradients of ~500 km s-1 across <=0.2'' (1.6 kpc) diameter regions, suggesting that the star-forming gas is in compact, rotating disks. Our data provide compelling evidence that these SMGs represent extreme, short-lived "maximum" star-forming events in highly dissipative mergers of gas-rich galaxies. The resulting high-mass surface and volume densities of SMGs are similar to those of compact quiescent galaxies in the same redshift range and much higher than those in local spheroids. From the ratio of the comoving volume densities of SMGs and quiescent galaxies in the same mass and redshift ranges, and from the comparison of gas exhaustion timescales and stellar ages, we estimate that the SMG phase duration is about 100 Myr. Our analysis of SMGs and optically/UV selected high-redshift star-forming galaxies supports a "universal" Chabrier IMF as being valid over the star-forming history of these galaxies. We find that the 12CO luminosity to total gas mass conversion factors at z ~ 2-3 are probably similar to those assumed at z ~ 0. The implied gas fractions in our sample galaxies range from 20% to 50%. Based on observations obtained at the IRAM Plateau de Bure Interferometer (PdBI). IRAM is funded by the Centre National de la Recherché Scientifique (France), the Max-Planck Gesellschaft (Germany), and the Instituto Geografico Nacional (Spain).

  7. A coincidence of disturbed morphology and blue UV colour: minor-merger-driven star formation in early-type galaxies at z˜ 0.6

    NASA Astrophysics Data System (ADS)

    Kaviraj, Sugata; Tan, Kok-Meng; Ellis, Richard S.; Silk, Joseph

    2011-03-01

    We exploit multiwavelength photometry of early-type galaxies (ETGs) in the Cosmological Evolution Survey (COSMOS) to demonstrate that the low-level star formation activity in the ETG population at intermediate redshift is likely to be driven by minor mergers. Splitting the ETGs into galaxies that show disturbed morphologies indicative of recent merging and those that appear relaxed, we find that ˜32 per cent of the ETG population appears to be morphologically disturbed. While the relaxed objects are almost entirely contained within the UV red sequence, their morphologically disturbed counterparts dominate the scatter to blue UV colours, regardless of luminosity. Empirically and theoretically determined major-merger rates in the redshift range z < 1 are several times too low to account for the fraction of disturbed ETGs in our sample, suggesting that minor mergers represent the principal mechanism driving the observed star formation activity in our sample. The young stellar components forming in these events have ages between 0.03 and 0.3 Myr and typically contribute ≤ 10 per cent of the stellar mass of the remnant. Together with recent work which demonstrates that the structural evolution of nearby ETGs is consistent with one or more minor mergers, our results indicate that the overall evolution of massive ETGs may be heavily influenced by minor merging at late epochs and highlights the need to systematically study this process in future observational surveys.

  8. Late Holocene paleoecology of Andros Island, Bahamas: Evidence of climate change and human disturbance

    SciTech Connect

    Kjellmark, E.W.

    1995-09-01

    Pollen and charcoal data from a transect of three sediment cores taken from deep, water-filled karst sinkholes on Andros Island, Bahamas have yielded a detailed record of late Holocene climate change and human disturbance. The pollen record reveals that a long-term, late Holocene dry period in the Caribbean, which extended from 3000 to 1500 years bp had a variable effect on the vegetation of Andros depending on its proximity to the water table. A site at 10 m elevation above the water table shows evidence of major changes in vegetation, while a low-lying site shows little effect. Both the charcoal and pollen records reveal possible evidence of human disturbance beginning after the dry period ends. A site 1 km from the east coast of Andros shows a peak in charcoal content in sediments that are 900-1000 years old. This post-dates human colonization of the Bahamas, which occurred 1000-1200 years bp and may be evidence of increased burning brought about by humans. A site 7 km inland shows a large peak in charcoal content and a distinct shift in the pollen spectrum from tropical hardwoods pollen to pinewoods pollen in sediments that are 700-800 years old. Charcoal content is low at this site in 450-500 year old sediments, then peaks again in 200-250 year old sediments. This may reflect the removal of humans from the Bahamas shortly after the arrival of Columbus, followed by re-colonization 250 years later. Although the changes in charcoal and pollen over the past 1000 years could have been climatically induced, the timing of the changes correlates closely with known events in the human history of the Bahamas.

  9. Evidence of an Emerging Disturbance of Earthen Levees Causing Disastrous Floods in Italy

    NASA Astrophysics Data System (ADS)

    Orlandini, S.; Moretti, G.; Albertson, J. D.

    2015-12-01

    A levee failure occurred along the Secchia River, Northern Italy, on January 19, 2014, resulting in flood damage in excess of $500 Million (Figure). In response to this failure, immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring Panaro River, where rapid mitigation efforts were successful in averting a full levee failure. The paired breach events that occurred along the Secchia and Panaro Rivers provided an excellent window on an emerging disturbance of levees and related failure mechanism. In the Secchia River, by combining the information content of photographs taken from helicopters in the early stage of breach development and 10-cm resolution aerial photographs taken in 2010 and 2012, animal burrows were found to exist in the precise levee location where the breach originated. In the Panaro River, internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top. Evidence collected suggested that it is quite likely that the levee failure of the Secchia River was of a similar mechanism as the observed failure of the Panaro River. Detailed numerical modeling of rainfall, river flow, and variably saturated flow occurring in disturbed levees in response to complex hydroclimatic forcing indicated that the levee failure of the Secchia River may have been triggered by direct river inflow into the den system or collapse of a hypothetical den separated by a 1-m earthen wall from the levee riverside, which saturated during the hydroclimatic event. It is important to bring these processes to the attention of hydrologists and geotechnical engineers as well as to trigger an interdisciplinary discussion on habitat fragmentation and wildlife shifts due to development and climate pressures. These disturbances come together with changes in extreme events to inform the broader concern of risk analysis due to floods.

  10. Multiple Core Galaxies

    NASA Technical Reports Server (NTRS)

    Miller, R.H.; Morrison, David (Technical Monitor)

    1994-01-01

    Nuclei of galaxies often show complicated density structures and perplexing kinematic signatures. In the past we have reported numerical experiments indicating a natural tendency for galaxies to show nuclei offset with respect to nearby isophotes and for the nucleus to have a radial velocity different from the galaxy's systemic velocity. Other experiments show normal mode oscillations in galaxies with large amplitudes. These oscillations do not damp appreciably over a Hubble time. The common thread running through all these is that galaxies often show evidence of ringing, bouncing, or sloshing around in unexpected ways, even though they have not been disturbed by any external event. Recent observational evidence shows yet another phenomenon indicating the dynamical complexity of central regions of galaxies: multiple cores (M31, Markarian 315 and 463 for example). These systems can hardly be static. We noted long-lived multiple core systems in galaxies in numerical experiments some years ago, and we have more recently followed up with a series of experiments on multiple core galaxies, starting with two cores. The relevant parameters are the energy in the orbiting clumps, their relative.masses, the (local) strength of the potential well representing the parent galaxy, and the number of cores. We have studied the dependence of the merger rates and the nature of the final merger product on these parameters. Individual cores survive much longer in stronger background potentials. Cores can survive for a substantial fraction of a Hubble time if they travel on reasonable orbits.

  11. JELLYFISH: EVIDENCE OF EXTREME RAM-PRESSURE STRIPPING IN MASSIVE GALAXY CLUSTERS

    SciTech Connect

    Ebeling, H.; Stephenson, L. N.; Edge, A. C.

    2014-02-01

    Ram-pressure stripping by the gaseous intracluster medium has been proposed as the dominant physical mechanism driving the rapid evolution of galaxies in dense environments. Detailed studies of this process have, however, largely been limited to relatively modest examples affecting only the outermost gas layers of galaxies in nearby and/or low-mass galaxy clusters. We here present results from our search for extreme cases of gas-galaxy interactions in much more massive, X-ray selected clusters at z > 0.3. Using Hubble Space Telescope snapshots in the F606W and F814W passbands, we have discovered dramatic evidence of ram-pressure stripping in which copious amounts of gas are first shock compressed and then removed from galaxies falling into the cluster. Vigorous starbursts triggered by this process across the galaxy-gas interface and in the debris trail cause these galaxies to temporarily become some of the brightest cluster members in the F606W passband, capable of outshining even the Brightest Cluster Galaxy. Based on the spatial distribution and orientation of systems viewed nearly edge-on in our survey, we speculate that infall at large impact parameter gives rise to particularly long-lasting stripping events. Our sample of six spectacular examples identified in clusters from the Massive Cluster Survey, all featuring M {sub F606W} < –21 mag, doubles the number of such systems presently known at z > 0.2 and facilitates detailed quantitative studies of the most violent galaxy evolution in clusters.

  12. EVIDENCE FOR WIDESPREAD ACTIVE GALACTIC NUCLEUS ACTIVITY AMONG MASSIVE QUIESCENT GALAXIES AT z {approx} 2

    SciTech Connect

    Olsen, Karen P.; Rasmussen, Jesper; Toft, Sune; Zirm, Andrew W.

    2013-02-10

    We quantify the presence of active galactic nuclei (AGNs) in a mass-complete (M {sub *} > 5 Multiplication-Sign 10{sup 10} M {sub Sun }) sample of 123 star-forming and quiescent galaxies at 1.5 {<=} z {<=} 2.5, using X-ray data from the 4 Ms Chandra Deep Field-South (CDF-S) survey. 41% {+-} 7% of the galaxies are detected directly in X-rays, 22% {+-} 5% with rest-frame 0.5-8 keV luminosities consistent with hosting luminous AGNs (L {sub 0.5-8keV} > 3 Multiplication-Sign 10{sup 42} erg s{sup -1}). The latter fraction is similar for star-forming and quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that perhaps luminous AGNs are triggered by external effects such as mergers. We detect significant mean X-ray signals in stacked images for both the individually non-detected star-forming and quiescent galaxies, with spectra consistent with star formation only and/or a low-luminosity AGN in both cases. Comparing star formation rates inferred from the 2-10 keV luminosities to those from rest-frame IR+UV emission, we find evidence for an X-ray excess indicative of low-luminosity AGNs. Among the quiescent galaxies, the excess suggests that as many as 70%-100% of these contain low- or high-luminosity AGNs, while the corresponding fraction is lower among star-forming galaxies (43%-65%). Our discovery of the ubiquity of AGNs in massive, quiescent z {approx} 2 galaxies provides observational support for the importance of AGNs in impeding star formation during galaxy evolution.

  13. Jellyfish: Evidence of Extreme Ram-pressure Stripping in Massive Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Ebeling, H.; Stephenson, L. N.; Edge, A. C.

    2014-02-01

    Ram-pressure stripping by the gaseous intracluster medium has been proposed as the dominant physical mechanism driving the rapid evolution of galaxies in dense environments. Detailed studies of this process have, however, largely been limited to relatively modest examples affecting only the outermost gas layers of galaxies in nearby and/or low-mass galaxy clusters. We here present results from our search for extreme cases of gas-galaxy interactions in much more massive, X-ray selected clusters at z > 0.3. Using Hubble Space Telescope snapshots in the F606W and F814W passbands, we have discovered dramatic evidence of ram-pressure stripping in which copious amounts of gas are first shock compressed and then removed from galaxies falling into the cluster. Vigorous starbursts triggered by this process across the galaxy-gas interface and in the debris trail cause these galaxies to temporarily become some of the brightest cluster members in the F606W passband, capable of outshining even the Brightest Cluster Galaxy. Based on the spatial distribution and orientation of systems viewed nearly edge-on in our survey, we speculate that infall at large impact parameter gives rise to particularly long-lasting stripping events. Our sample of six spectacular examples identified in clusters from the Massive Cluster Survey, all featuring M F606W < -21 mag, doubles the number of such systems presently known at z > 0.2 and facilitates detailed quantitative studies of the most violent galaxy evolution in clusters. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-10491, -10875, -12166, and -12884.

  14. XMM-Newton and Chandra Observations of the Galaxy Group NGC 5044. 1; Evidence for Limited Multiphase Hot Gas

    NASA Technical Reports Server (NTRS)

    Buote, David A.; Lewis, Aaron D.; Brighenti, Fabrizio; Mathews, William G.

    2003-01-01

    Using new XMM and Chandra observations, we present an analysis of the temperature structure of the hot gas within a radius of 100 kpc of the bright nearby galaxy group NGC 5044. A spectral deprojection analysis of data extracted from circular annuli reveals that a two-temperature model (2T) of the hot gas is favored over single-phase or cooling flow (M = 4.5 +/- 0.2 solar mass/yr) models within the central approx.30 kpc. Alternatively, the data can be fitted equally well if the temperature within each spherical shell varies continuously from approx.T(sub h) to T(sub c) approx. T(sub h)/2, but no lower. The high spatial resolution of the Chandra data allows us to determine that the temperature excursion T(sub h) approaches T(sub c) required in each shell exceeds the temperature range between the boundaries of the same shell in the best-fitting single-phase model. This is strong evidence for a multiphase gas having a limited temperature range. We do not find any evidence that azimuthal temperature variations within each annulus on the sky can account for the range in temperatures within each shell. We provide a detailed investigation of the systematic errors on the derived spectral models considering the effects of calibration, plasma codes, bandwidth, variable NH, and background rate. We find that the RGS gratings and the EPIC and ACIS CCDs give fully consistent results when the same models are fitted over the same energy ranges for each instrument. The cooler component of the 2T model has a temperature (T(sub c) approx. 0.7 keV) similar to the kinetic temperature of the stars. The hot phase has a temperature (T(sub h) approx. 1.4 keV) characteristic of the virial temperature of the solar mass halo expected in the NGC 5044 group. However, in view of the morphological disturbances and X-ray holes visible in the Chandra image within R approx. equals 10 kpc, bubbles of gas heated to approx.T(sub h) in this region may be formed by intermittent AGN feedback. Some

  15. X-ray evidence of an obscured nucleus in the type 2 Seyfert galaxy Mkn3

    NASA Astrophysics Data System (ADS)

    Awaki, H.; Koyama, K.; Kunieda, H.; Tawara, Y.

    1990-08-01

    Seyfert galaxies are classified as type 1 or 2 according to the presence or absence of broad emission lines in the optical spectrum. The high velocities indicated by the broad lines in Seyfert 1 galaxies are taken to be good evidence of a compact, massive object, as are the strong and variable hard X-ray sources that are also generally observed in these objects. In contrast, Seyfert 2 galaxies possess neither of these characteristics, so the theory that they too have an accreting massive blackhole is less compelling. Since the discovery by spectropolarimetry of a 'hidden' Seyfert 1 nucleus in the prototypical Seyfert 2, NGC1068, the long-standing hope that the two classes may be unified has been revived. Here from observations by the Ginga satellite that another Seyfert 2, Mkn3, has the X-ray spectral signature of a hidden type 1 nucleus.

  16. Indirect Evidence for Escaping Lyman Continuum Photons in Local Lyman Break Galaxy Analogs

    NASA Astrophysics Data System (ADS)

    Alexandroff, Rachael; Heckman, Timothy M.; Borthakur, Sanchayeeta; Overzier, Roderik

    2015-01-01

    A population of early star-forming galaxies is the leading candidate for the re-ionization of the universe. It is still unclear, however, what conditions and physical processes would enable a significant fraction of the ionizing photons to escape from these gas-rich galaxies. In addition, studies of high redshift galaxies have yet to uncover a large sample of galaxies with the required high escape fraction of ionizing photons.We have uncovered a sample of local analogs to high-redshift, star-forming Lyman Break Galaxies (LBGs) called Lyman Break Analogs (LBAs) by matching the Sloan Digital Sky Survey (SDSS) and Galaxy Evolution Explorer (GALEX) catalogs. These galaxies are remarkably similar to LBGs in their properties-- morphology, size, UV luminosity, SFR, mass, velocity dispersion, metallicity and dust content. We obtained HST COS far-UV spectroscopy plus ancillary multi-waveband data of a sample of 22 LBAs to look for indirect evidence of escaping ionizing radiation (leakiness).We measure three parameters: (1) the residual intensity in the cores of saturated interstellar low-ionization absorption-lines, which indicates incomplete covering by that gas in the galaxy. (2) The relative amount of blue-shifted Lyman alpha line emission, which can indicate the existence of holes in the neutral hydrogen on the front-side of the galaxy outflow, and (3) the relative weakness of the [SII] optical emission lines that trace matter-bounded HII regions. We find all three diagnostics agree well with one another. Finally, we find the strongest correlation between these leakiness indicators and both the compactness of the galactic star-forming region (size and star formation rate/area) and the speed of the galactic outflow. This suggests that extreme feedback- a high intensity of ionizing radiation and strong pressure from both radiation and a hot galactic wind- combines to create significant holes in the neutral gas. These results not only shed new light on the physical

  17. The Calvin 28 cryptoexplosive disturbance, Cass County, Michigan: Evidence for impact origin

    NASA Technical Reports Server (NTRS)

    Milstein, Randall L.

    1988-01-01

    The Calvin 28 cryptoexplosive disturbance is an isolated, nearly circular subsurface structure of Late Ordovician age in southwestern Michigan. The structure is defined by 107 wells, is about 7.24 km in diameter and consists of a central dome, an annular depression and an encircling anticlinal rim. Seismic and geophysical well log data confirm that an intricate system of faults and structural derangement exists within the structure. Deformation decreases with depth and distance from the structure. U.S.G.S. topographic maps and aerial imagery show the structure is reflected as a subtle surface topographic rise controlling local drainage. Igneous or diapiric intrusion and solution collapse are rejected as possible origins for Calvin 28 on the basis of stratigraphic, structural and geophysical evidence. A volcanic origin is inconsistent with calculated energy requirements and an absence of igneous material. Although shock-metamorphic features are unidentified, microbreccias occur in deep wells that penetrate the structure. Morphology and structural parameters support an impact origin.

  18. Evidence of bacterioplankton community adaptation in response to long-term mariculture disturbance

    PubMed Central

    Xiong, Jinbo; Chen, Heping; Hu, Changju; Ye, Xiansen; Kong, Dingjiang; Zhang, Demin

    2015-01-01

    Understanding the underlying mechanisms that shape the temporal dynamics of a microbial community has important implications for predicting the trajectory of an ecosystem’s response to anthropogenic disturbances. Here, we evaluated the seasonal dynamics of bacterioplankton community composition (BCC) following more than three decades of mariculture disturbance in Xiangshan Bay. Clear seasonal succession and site (fish farm and control site) separation of the BCC were observed, which were primarily shaped by temperature, dissolved oxygen and sampling time. However, the sensitive bacterial families consistently changed in relative abundance in response to mariculture disturbance, regardless of the season. Temporal changes in the BCC followed the time-decay for similarity relationship at both sites. Notably, mariculture disturbance significantly (P < 0.001) flattened the temporal turnover but intensified bacterial species-to-species interactions. The decrease in bacterial temporal turnover under long-term mariculture disturbance was coupled with a consistent increase in the percentage of deterministic processes that constrained bacterial assembly based on a null model analysis. The results demonstrate that the BCC is sensitive to mariculture disturbance; however, a bacterioplankton community could adapt to a long-term disturbance via attenuating temporal turnover and intensifying species-species interactions. These findings expand our current understanding of microbial assembly in response to long-term anthropogenic disturbances. PMID:26471739

  19. Direct observational evidence for a large transient galaxy population in groups at 0.85 < z < 1

    NASA Astrophysics Data System (ADS)

    Balogh, Michael L.; McGee, Sean L.; Wilman, David J.; Finoguenov, Alexis; Parker, Laura C.; Connelly, Jennifer L.; Mulchaey, John S.; Bower, Richard G.; Tanaka, Masayuki; Giodini, Stefania

    2011-04-01

    blue cloud to the red sequence, with a star formation rate that declines with an exponential time-scale 0.6 < τ < 2 Gyr. Such galaxies may not be exclusive to the group environment, as we find examples also amongst the non-members. However, their prominence among the group galaxy population, and the marked lack of blue, star-forming galaxies, provides evidence that the group environment either directly reduces star formation in member galaxies or at least prevents its rejuvenation during the normal cycle of galaxy evolution.

  20. Indirect Evidence for Escaping Ionizing Photons in Local Lyman Break Galaxy Analogs

    NASA Astrophysics Data System (ADS)

    Alexandroff, Rachael M.; Heckman, Timothy M.; Borthakur, Sanchayeeta; Overzier, Roderik; Leitherer, Claus

    2015-09-01

    A population of early star-forming galaxies is the leading candidate for the re-ionization of the universe. It is still unclear, however, what conditions and physical processes would enable a significant fraction of the ionizing (Lyman continuum) photons to escape from these gas-rich galaxies. In this paper we present the results of the analysis of Hubble Space Telescope Cosmic Origins Spectrograph far-UV (FUV) spectroscopy plus ancillary multi-waveband data of a sample of 22 low-redshift galaxies that are good analogs to typical star-forming galaxies at high redshift. We measure three parameters that provide indirect evidence of the escape of ionizing radiation (leakiness): (1) the residual intensity in the cores of saturated interstellar low-ionization absorption lines, which indicates incomplete covering by that gas in the galaxy; (2) the relative amount of blueshifted Lyα line emission, which can indicate the existence of holes in the neutral hydrogen on the front-side of the galaxy outflow, and (3) the relative weakness of the [S ii] optical emission lines that trace matter-bounded H ii regions. We show that our residual intensity measures are only negligibly affected by infilling from resonance emission lines. We find all three diagnostics agree well with one another. We use these diagnostics to rank-order our sample in terms of likely leakiness, noting that a direct measure of escaping Lyman continuum has recently been made for one of the leakiest members of our sample. We then examine the correlations between our ranking and other proposed diagnostics of leakiness. We find a good correlation with the equivalent width of the Lyα emission line, but no significant correlations with either the flux ratio of the [O iii]/[O ii] emission lines or the ratio of star-formation rates derived from the (dust-corrected) FUV and Hα luminosities. Turning to galaxy properties, we find the strongest correlations with leakiness are with the compactness of the star

  1. Evidence for dwarf stars at D of about 100 kiloparsecs near the Sextans dwarf spheroidal galaxy

    NASA Astrophysics Data System (ADS)

    Gould, Andrew; Guhathakurta, Puragra; Richstone, Douglas; Flynn, Chris

    1992-04-01

    A method is presented for detecting individual, metal-poor, dwarf stars at distances less than about 150 kpc - a method specifically designed to filter out stars from among the much more numerous faint background field galaxies on the basis of broad-band colors. This technique is applied to two fields at high Galactic latitude, for which there are deep CCD data in four bands ranging from 3600 to 9000 A. The field in Sextans probably contains more than about five dwarf stars with BJ not greater than 25.5. These are consistent with being at a common distance about 100 kpc and lie about 1.7 deg from the newly discovered dwarf galaxy in Sextans whose distance is about 85 +/- 10 kpc. The stars lie near the major axis of the galaxy and are near or beyond the tidal radius. The second field, toward the south Galactic pole, may contain up to about five extra-Galactic stars, but these show no evidence for being at a common distance. Possible applications of this type technique are discussed, and it is shown that even very low surface brightness star clusters or dwarf galaxies may be detected at distances less than about 1 Mpc.

  2. Evidence for dwarf stars at D of about 100 kiloparsecs near the Sextans dwarf spheroidal galaxy

    NASA Technical Reports Server (NTRS)

    Gould, Andrew; Guhathakurta, Puragra; Richstone, Douglas; Flynn, Chris

    1992-01-01

    A method is presented for detecting individual, metal-poor, dwarf stars at distances less than about 150 kpc - a method specifically designed to filter out stars from among the much more numerous faint background field galaxies on the basis of broad-band colors. This technique is applied to two fields at high Galactic latitude, for which there are deep CCD data in four bands ranging from 3600 to 9000 A. The field in Sextans probably contains more than about five dwarf stars with BJ not greater than 25.5. These are consistent with being at a common distance about 100 kpc and lie about 1.7 deg from the newly discovered dwarf galaxy in Sextans whose distance is about 85 +/- 10 kpc. The stars lie near the major axis of the galaxy and are near or beyond the tidal radius. The second field, toward the south Galactic pole, may contain up to about five extra-Galactic stars, but these show no evidence for being at a common distance. Possible applications of this type technique are discussed, and it is shown that even very low surface brightness star clusters or dwarf galaxies may be detected at distances less than about 1 Mpc.

  3. Near-infrared line-strengths in elliptical galaxies: evidence for initial mass function variations?

    NASA Astrophysics Data System (ADS)

    Cenarro, A. J.; Gorgas, J.; Vazdekis, A.; Cardiel, N.; Peletier, R. F.

    2003-02-01

    We present new relations between recently defined line-strength indices in the near-infrared (CaT*, CaT, PaT, MgI and sTiO) and central velocity dispersion (σ0) for a sample of 35 early-type galaxies, showing evidence for significant anti-correlations between CaII triplet indices (CaT* and CaT) and log σ0. These relations are interpreted in the light of our recent evolutionary synthesis model predictions, suggesting the existence of important Ca underabundances with respect to Fe and/or an increase of the dwarf to giant stars ratio along the mass sequence of elliptical galaxies.

  4. Continuum models for gas in disturbed galaxies. III. Bifurcations and chaos in a deterministic model for bursts of star formation

    SciTech Connect

    Struck-Marcell, C.; Scalo, J.M.

    1987-05-01

    A study of the nonlinear behavior of model equations describing the Oort model for interstellar cloud evolution and star formation is presented. One-zone cloud fluid equations for the Oort model are given, and it is shown how, as the time-delay parameter T(d) is increased, the system bifurcates to limit-cycle behavior accompanied by star formation bursts and, with further increase in T(d), suffers further bifurcations leading to chaotic behavior. A linear stability analysis, including time delay, is used to demonstrate that the behavior of the Oort model does not depend sensitively on the other parameters involved. It is also shown that the onset of bifurcation to a limit cycle can be predicted analytically. The major predictions of the calculations are compared with available relevant observations of star formation activity in galaxies, especially tidally interacting galaxies. 112 references.

  5. Kinematical evidence for secular evolution in Spitzer Survey of Stellar Structure in Galaxies (S4G) spirals

    NASA Astrophysics Data System (ADS)

    Erroz-Ferrer, Santiago; Knapen, Johan H.; Font, Joan; Beckman, John E.

    2015-03-01

    We present a study of the kinematics of a sample of isolated spiral galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G). We use Hα Fabry-Perot data from the GHαFaS instrument at the William Herschel Telescope (WHT) in La Palma, complemented with images at 3.6 microns, in the R band and in the Hα filter. The resulting data cubes and velocity field maps allow a complete study of the kinematics of a galaxy, including in-depth investigations of the rotation curve, velocity moment maps, velocity residual maps, gradient maps and position-velocity (PV) diagrams. We find clear evidence of the secular evolution processes going on in these galaxies, such as asymmetries in the velocity field in the bar zone, and non-circular motions, probably in response to the potential of the structural components of the galaxies, or to past or present interactions.

  6. HUBBLE REVEALS 'BACKWARDS' SPIRAL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have found a spiral galaxy that may be spinning to the beat of a different cosmic drummer. To the surprise of astronomers, the galaxy, called NGC 4622, appears to be rotating in the opposite direction to what they expected. Pictures by NASA's Hubble Space Telescope helped astronomers determine that the galaxy may be spinning clockwise by showing which side of the galaxy is closer to Earth. A Hubble telescope photo of the oddball galaxy is this month's Hubble Heritage offering. The image shows NGC 4622 and its outer pair of winding arms full of new stars [shown in blue]. Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. To add to the conundrum, NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction it is rotating. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise. NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. What caused this galaxy to behave differently from most galaxies? Astronomers suspect that NGC 4622 interacted with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a small companion galaxy. The galaxy's core provides new evidence for a merger between NGC 4622 and a smaller galaxy. This information could be the key to understanding the unusual leading arms. Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way Galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 resides 111 million light-years away in the constellation Centaurus. The pictures were taken in May 2001 with Hubble

  7. X-RAY ISOPHOTES IN A RAPIDLY ROTATING ELLIPTICAL GALAXY: EVIDENCE OF INFLOWING GAS

    SciTech Connect

    Brighenti, Fabrizio; Mathews, William G.

    2009-11-10

    We describe two-dimensional gasdynamical computations of the X-ray emitting gas in the rotating elliptical galaxy NGC 4649 that indicate an inflow of approx1 M{sub sun} yr{sup -1} at every radius. Such a large instantaneous inflow cannot have persisted over a Hubble time. The central constant-entropy temperature peak recently observed in the innermost 150 pc is explained by compressive heating as gas flows toward the central massive black hole. Since the cooling time of this gas is only a few million years, NGC 4649 provides the most acutely concentrated known example of the cooling flow problem in which the time-integrated apparent mass that has flowed into the galactic core exceeds the total mass observed there. This paradox can be resolved by intermittent outflows of energy or mass driven by accretion energy released near the black hole. Inflowing gas is also required at intermediate kpc radii to explain the ellipticity of X-ray isophotes due to spin-up by mass ejected by stars that rotate with the galaxy and to explain local density and temperature profiles. We provide evidence that many luminous elliptical galaxies undergo similar inflow spin-up. A small turbulent viscosity is required in NGC 4649 to avoid forming large X-ray luminous disks that are not observed, but the turbulent pressure is small and does not interfere with mass determinations that assume hydrostatic equilibrium.

  8. NO EVIDENCE FOR CLASSICAL CEPHEIDS AND A NEW DWARF GALAXY BEHIND THE GALACTIC DISK

    SciTech Connect

    Pietrukowicz, P.; Udalski, A.; Szymański, M. K.; Soszyński, I.; Pietrzyński, G.; Wyrzykowski, Ł.; Poleski, R.; Ulaczyk, K.; Skowron, J.; Mróz, P.; Pawlak, M.; Kozłowski, S.

    2015-11-10

    Based on data from the ongoing OGLE Galaxy Variability Survey (OGLE GVS), we have verified observed properties of stars detected by the near-infrared VVV survey in a direction near the Galactic plane at longitude l ≈ −27° and recently tentatively classified as classical Cepheids belonging to, hence claimed, a dwarf galaxy at a distance of about 90 kpc from the Galactic Center. Three of four stars are detected in the OGLE GVS I-band images. We show that two of the objects are not variable at all, and the third one with a period of 5.695 days and a nearly sinusoidal light curve of an amplitude of 0.5 mag cannot be a classical Cepheid and is very likely a spotted object. These results together with a very unusual shape of the K{sub s}-band light curve of the fourth star indicate that it is very likely that none of them is a Cepheid and, thus there is no evidence for a background dwarf galaxy. Our observations show that great care must be taken when classifying objects by their low-amplitude close-to-sinusoidal near-infrared light curves, especially with a small number of measurements. We also provide a sample of high-amplitude spotted stars with periods of a few days that can mimic pulsations and even eclipses.

  9. Evidence for a change in the dominant satellite galaxy quenching mechanism at z = 1

    NASA Astrophysics Data System (ADS)

    Balogh, Michael L.; McGee, Sean L.; Mok, Angus; Muzzin, Adam; van der Burg, Remco F. J.; Bower, Richard G.; Finoguenov, Alexis; Hoekstra, Henk; Lidman, Chris; Mulchaey, John S.; Noble, Allison; Parker, Laura C.; Tanaka, Masayuki; Wilman, David J.; Webb, Tracy; Wilson, Gillian; Yee, Howard K. C.

    2016-03-01

    We present an analysis of galaxies in groups and clusters at 0.8 < z < 1.2, from the GCLASS and GEEC2 spectroscopic surveys. We compute a `conversion fraction' fconvert that represents the fraction of galaxies that were prematurely quenched by their environment. For massive galaxies, Mstar > 1010.3 M⊙, we find fconvert ˜ 0.4 in the groups and ˜0.6 in the clusters, similar to comparable measurements at z = 0. This means the time between first accretion into a more massive halo and final star formation quenching is tp ˜ 2 Gyr. This is substantially longer than the estimated time required for a galaxy's star formation rate to become zero once it starts to decline, suggesting there is a long delay time during which little differential evolution occurs. In contrast with local observations we find evidence that this delay time-scale may depend on stellar mass, with tp approaching tHubble for Mstar ˜ 109.5 M⊙. The result suggests that the delay time must not only be much shorter than it is today, but may also depend on stellar mass in a way that is not consistent with a simple evolution in proportion to the dynamical time. Instead, we find the data are well-matched by a model in which the decline in star formation is due to `overconsumption', the exhaustion of a gas reservoir through star formation and expulsion via modest outflows in the absence of cosmological accretion. Dynamical gas removal processes, which are likely dominant in quenching newly accreted satellites today, may play only a secondary role at z = 1.

  10. THE FERMI BUBBLES. I. POSSIBLE EVIDENCE FOR RECENT AGN JET ACTIVITY IN THE GALAXY

    SciTech Connect

    Guo Fulai; Mathews, William G.

    2012-09-10

    The Fermi Gamma-ray Space Telescope reveals two large gamma-ray bubbles in the Galaxy, which extend about 50 Degree-Sign ({approx}10 kpc) above and below the Galactic center (GC) and are symmetric about the Galactic plane. Using axisymmetric hydrodynamic simulations with a self-consistent treatment of the dynamical cosmic ray (CR)-gas interaction, we show that the bubbles can be created with a recent active galactic nucleus (AGN) jet activity about 1-3 Myr ago, which was active for a duration of {approx}0.1-0.5 Myr. The bipolar jets were ejected into the Galactic halo along the rotation axis of the Galaxy. Near the GC, the jets must be moderately light with a typical density contrast 0.001 {approx}< {eta} {approx}< 0.1 relative to the ambient hot gas. The jets are energetically dominated by kinetic energy, and overpressured with either CR or thermal pressure which induces lateral jet expansion, creating fat CR bubbles as observed. The sharp edges of the bubbles imply that CR diffusion across the bubble surface is strongly suppressed. The jet activity induces a strong shock, which heats and compresses the ambient gas in the Galactic halo, potentially explaining the ROSAT X-ray shell features surrounding the bubbles. The Fermi bubbles provide plausible evidence for a recent powerful AGN jet activity in our Galaxy, providing new insights into the origin of the halo CR population and the channel through which massive black holes in disk galaxies release feedback energy during their growth.

  11. Does a localized plasma disturbance in the ionosphere evolve to electrostatic equilibrium? Evidence to the contrary

    NASA Astrophysics Data System (ADS)

    Cosgrove, Russell B.

    2016-01-01

    Electrostatic equilibrium must be achieved through electromagnetic evolution. From an initial state with nonzero neutral wind localized along the geomagnetic field, and with all other plasma and electromagnetic perturbations initially zero, evolution progresses from plasma velocity to electric field to magnetic field, where the last step can launch an Alfvén wave that transmits the electromagnetic disturbance along geomagnetic field lines. Without the Alfvén wave the disturbance does not map along geomagnetic field lines, and there is no semblance of electrostatic equilibrium. This paradigm is essentially the traditional magnetosphere/ionosphere coupling paradigm, except addressed to smaller-scale, local ionospheric phenomena. However, Alfvén waves have not been thoroughly studied in the context of the partially ionized, collisional ionospheric plasma, and so the full effects predicted by this modeling paradigm are not known. In this work we adopt the two-fluid equations and investigate whether the ionosphere supports Alfvén-type waves that can transmit disturbances along geomagnetic field lines and perform a wave analysis of the "lumped circuit" parameters normally used to characterize the ionosphere under electrostatic equilibrium. We find that under the wave analysis (1) the Pedersen conductivity is severely modified and has a negative real part at short wavelengths; (2) the mapping distance for electric fields is significantly modified, and there is a nonnegligible wavelength along the geomagnetic field; and (3) the load admittance seen by a localized dynamo is strongly reactive, causing a phase offset between electric field and current, as compared with that when the load is electrostatic.

  12. PEARS Emission Line Galaxies

    NASA Technical Reports Server (NTRS)

    Pirzkal, Nor; Rothberg, Barry; Ly, Chun; Rhoads, James E.; Malhotra, Sangeeta; Grogin, Norman A.; Dahlen, Tomas; Meurer, Gerhardt R.; Walsh, Jeremy; Hathi, Nimish P.; Cohen, Seth; Belini, Andrea; Holwerda, Benne W.; Straughn, Amber; Mechtley, Matthew

    2012-01-01

    We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitless grism spectroscopic data obtained vl'ith the Advanced Camera for Surveys on HST. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random surveY of galaxies, as well as the availability of a wide variety of ancillary observations to support the spectroscopic results. Using the PEARS data we are able to identify star forming galaxies within the redshift volume 0 < z < 1.5. Star forming regions in the PEARS survey are pinpointed independently of the host galaxy. This method allOW8 us to detect the presence of multiple emission line regions (ELRs) within a single galaxy. 1162 [OII], [OIII] and/or H-alpha emission lines have been identified in the PEARS sample of approx 906 galaxies down to a limiting flux of approx 10 - 18 erg/s/sq cm . The ELRs have also been compared to the properties of the host galaxy, including morphology, luminosity, and mass. From this analysis we find three key results: 1) The computed line luminosities show evidence of a flattening in the luminosity function with increasing redshift; 2) The star forming systems show evidence of disturbed morphologies, with star formation occurring predominantly within one effective (half-light) radius. However, the morphologies show no correlation with host stellar mass; and 3) The number density of star forming galaxies with M(*) >= 10(exp 9) Solar M decreases by an order of magnitude at z<=0.5 relative to the number at 0.5 < z < 0.9 in support of the argument for galaxy downsizing.

  13. Post-fire Gully Rejuvenation - Evidence of Process Thresholds Controlled by Vegetation Disturbance

    NASA Astrophysics Data System (ADS)

    Hyde, K.; Woods, S.

    2011-12-01

    High intensity rainfall may trigger gully rejuvenation on hillslopes recently disturbed by wildfire, leading to debris-laden flows which generally contribute the majority of sediment transported in post-fire erosion events. We investigated the extent to which the occurrence of gully rejuvenation can be predicted based upon burn severity, rainfall data and basin morphometric variables. Field surveys were conducted at six Northern Rockies sites to identify occurrence of gully rejuvenation in first order catchments and to map and characterize the location of gully heads. NEXRAD and rain gage data analysis coupled with field observations characterized rainfall intensity and extent. Building on previous work we quantified burn severity using the Vegetation Disturbance Index (VDI), a continuous metric based upon Burned Area Reflectance Classification (BARC) maps derived from satellite imagery using the dNBR algorithm. GIS analysis combined the VDI with morphometric factors expected to influence hillslope stability. Gully heads marked abrupt transition in channel form. Above gully heads, channels were shallow and U-shaped with gentle transition to the hillslope and fine root hairs intact. Angular edges marked deep gully head incisions which down-cut channel floors from 0.2-0.3 to 1.0 meter or more. Any remaining roots were coarse and the hillslope transition was sharp. Gully heads were located at variable distances below the master rill head of the catchment hollow. Distances were obviously greater where live canopy remained upslope. Gully head morphology strongly suggests flow force transition and exceedance of an erosion process threshold. The variable distance of the gully head below the hollow suggest upslope controls influencing initiation point, possibly degree and spatial pattern of burn severity. Binary logistic regression revealed stronger correlation between gully rejuvenation and VDI than morphometric variables. The statistical strength using the continuous

  14. Evidence against small dam removal as an ecological disturbance: Benthic macroinvertebrate and channel responses to dam removals in Oregon, USA

    NASA Astrophysics Data System (ADS)

    Tullos, D. D.

    2012-12-01

    A dominant concern for environmental managers is often the biological consequences of the physical disturbance generated by sediment pulses, such as those associated with dam removal or sediment flushing from existing dams. However, limited field data exists against which concerns regarding planned removals can be evaluated. This study documents an investigation of biophysical interactions related to sediment pulses from dam removals, with emphasis on a) the spatial extent and magnitude of disturbance to channel habitat and benthic macroinvertebrate community, and b) the rate and spatial patterns of channel and invertebrate community recovery over time. We analyzed field observations, collected in an upstream-downstream BACI study design, from three dam removals of varying size and channel substrate: Brownsville Dam, Calapooia River (height = 2.5 m, D50 = 59 m), Chiloquin Dam, Sprague River (height = 3.4 m, D50 = 0.15 mm), and Savage Rapids Dam, Rogue River (height = 12 m, D50 = 8 m). At each site, we investigated how elements of the physical channel related to disturbance (grain size and variability, bed stability, bed complexity) and benthic macroinvertebrate community (species richness, functional traits) changed over space and time. We projected that hypothesized changes in the physical channel (reduction in bed complexity, site-specific changes in bed mobility, site-specific grain size changes) following the sediment pulse would lead to reduction in species richness and a transition to functional traits (short lived, rapid reproduction, tolerant of mobile beds) affiliated with sediment disturbance. However, results indicate that our hypothesized channel changes were not consistently validated across the sites. Further, we found little evidence of substantial impact of the sediment pulse on the invertebrate communities, though some variability in functional traits may be attributable to dam removal at Savage Rapids. More specifically, we found that: a) Channel

  15. Evidence that high-sucrose diet reduces dentin formation and disturbs mineralization in rat molars.

    PubMed

    Hietala, E L; Larmas, M

    1995-12-01

    In addition to its caries-promoting effect, a high-sucrose diet reduces the apposition of mineralized dentin in young rats. This study was undertaken to test whether it has a similar effect on the width of the as-yet-uncalcified matrix, predentin. Female Wistar rats were weaned at the age of 3 weeks and fed for 7 weeks with either a high-sucrose diet, a non-cariogenic raw potato starch diet, or a non-cariogenic commercial powdered rat food (for reference). The sucrose diet induced the greatest number of caries lesions. Dentin formation was smaller and the predentin zone wider in rats fed a sucrose diet when compared with rats fed the reference diet. In rats fed a starch diet, dentin formation was smaller than in rats fed a reference diet, but no alterations in the areas of caries lesions or predentin width were observed. Widening of the predentin zone in rats fed a high-sucrose diet may reflect changes in odontoblast function, such as reduced matrix synthesis and possibly disturbed mineralization. Dentinal caries progression may thus be modulated by odontoblast function, not as much by matrix formation but rather by mineralization.

  16. Deep Fabry-Perot imaging of NGC 6240: Kinematic evidence for merging galaxies

    NASA Technical Reports Server (NTRS)

    Hawthorn, J. Bland; Wilson, A. S.; Tully, R. B.

    1990-01-01

    The authors have observed the superluminous, infrared galaxy NGC 6240 (z = 0.025) at H alpha with the Hawaii Imaging Fabry-Perot Interferometer (HIFI - Bland and Tully 1989). During the past decade, observational evidence from all wavebands indicates that the unusual appearance of NGC 6240 has resulted from a collision between two gas-rich systems, a view which is supported by our spectrophotometric data. However, the origin of the enormous infrared luminosity (4 times 10(exp 11) solar luminosity) detected by the Infrared Astronomy Satellite (IRAS) remains highly controversial, where opinions differ on the relative roles of large-scale shocks, massive star formation or a buried 'active' nucleus. These mechanisms are discussed in the light of the author's Fabry-Perot observations.

  17. Fast Molecular Outflows in Luminous Galaxy Mergers: Evidence for Quasar Feedback from Herschel

    NASA Technical Reports Server (NTRS)

    Veilleux, S.; Melendez, M.; Sturm, E.; Garcia-Carpio, J.; Fischer, J.; Gonzalez-Alfonso, E.; Contursi, A.; Lutz, D.; Poglitsch, A.; Davies, R.; Genzel, R.; Tacconi, L.; deJong, J. A.; Sternberg, A.; Netzer, H.; Hailey-Dunsheath, S.; Verma, A.; Rupke, D. S. N.; Maiolino, R.; Teng, S. H.; Polisensky, E.

    2013-01-01

    We report the results from a systematic search for molecular (OH 119 micron) outflows with Herschel/PACS in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7 micron silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than-50 km/s, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (approx. 145 deg.) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km/s is seen in only four objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of approx. -1000 km/s are measured in several objects, but median outflow velocities are typically approx.-200 km/s-1. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large active galactic nucleus (AGN) fractions and luminosities [log (L(sub AGN)/L(sub solar)) => 11.8 +/- 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. However, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.

  18. FAST MOLECULAR OUTFLOWS IN LUMINOUS GALAXY MERGERS: EVIDENCE FOR QUASAR FEEDBACK FROM HERSCHEL

    SciTech Connect

    Veilleux, S.; Meléndez, M.; Sturm, E.; Gracia-Carpio, J.; Contursi, A.; Lutz, D.; Poglitsch, A.; Davies, R.; Genzel, R.; Tacconi, L.; De Jong, J. A.; Fischer, J.; González-Alfonso, E.; Sternberg, A.; Netzer, H.; Hailey-Dunsheath, S.; Verma, A.; Rupke, D. S. N.; Maiolino, R.; Teng, S. H. E-mail: marcio@astro.umd.edu; and others

    2013-10-10

    We report the results from a systematic search for molecular (OH 119 μm) outflows with Herschel/PACS in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7 μm silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than –50 km s{sup –1}, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (∼145°) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km s{sup –1}, is seen in only four objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of ∼–1000 km s{sup –1} are measured in several objects, but median outflow velocities are typically ∼–200 km s{sup –1}. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large active galactic nucleus (AGN) fractions and luminosities [log (L{sub AGN}/L{sub ☉}) ≥ 11.8 ± 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. However, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.

  19. Evidence for Merging or Disruption of Red Galaxies from the Evolution of Their Clustering

    SciTech Connect

    White, Martin; White, Martin; Zheng, Zheng; Brown, Michael J. I.; Dey, Arjun; Jannuzi, Buell T.

    2006-11-29

    The formation and evolution of massive red galaxies form a crucial test of theories of galaxy formation based on hierarchical assembly. In this Letter we use observations of the clustering of luminous red galaxies from the Boötes field and N-body simulations to argue that about of the most luminous satellite galaxies appear to undergo merging or disruption within massive halos between and 0.5.

  20. Evidence for powerful AGN winds at high redshift: dynamics of galactic outflows in radio galaxies during the ``Quasar Era''

    NASA Astrophysics Data System (ADS)

    Nesvadba, N. P. H.; Lehnert, M. D.; De Breuck, C.; Gilbert, A. M.; van Breugel, W.

    2008-11-01

    AGN feedback now appears as an attractive mechanism to resolve some of the outstanding problems with the “standard” cosmological models, in particular those related to massive galaxies. At low redshift, evidence is growing that gas cooling and star formation may be efficiently suppressed by mechanical energy input from radio sources. To directly constrain how this may influence the formation of massive galaxies near the peak in the redshift distribution of powerful quasars, z˜ 2, we present an analysis of the emission-line kinematics of 3 powerful radio galaxies at z˜ 2-3 (HzRGs) based on rest-frame optical integral-field spectroscopy obtained with SINFONI on the VLT. The host galaxies of powerful radio-loud AGN are among the most massive galaxies, and thus AGN feedback may have a particularly clear signature in these galaxies. We find evidence for bipolar outflows in all HzRGs, with kinetic energies that are equivalent to 0.2% of the rest-mass of the supermassive black hole. Observed total velocity offsets in the outflows are ~800-1000 km s-1 between the blueshifted and redshifted line emission, and FWHMs ~ 1000 km s-1 suggest strong turbulence. Line ratios allow to measure electron temperatures, ~104 K from [OIII]λλλ4363, 4959, 5007 at z˜ 2, electron densities (~500 cm-3) and extinction (A_V˜ 1-4 mag). Ionized gas masses estimated from the Hα luminosity are of order 1010~M⊙, similar to the molecular gas content of HzRGs, underlining that these outflows may indicate a significant phase in the evolution of the host galaxy. The total energy release of ~1060 erg during a dynamical time of ~107 yrs corresponds to about the binding energy of a massive galaxy, similar to the prescriptions adopted in galaxy evolution models. Geometry, timescales and energy injection rates of order 10% of the kinetic energy flux of the jet suggest that the outflows are most likely driven by the radio source. The global energy density release of ~1057 erg s-1 Mpc-3 may also

  1. Populations of High-Luminosity Density-Bounded HII Regions in Spiral Galaxies? Evidence and Implications

    NASA Technical Reports Server (NTRS)

    Beckman, J. E.; Rozas, M.; Zurita, A.; Watson, R. A.; Knapen, J. H.

    2000-01-01

    In this paper we present evidence that the H II regions of high luminosity in disk galaxies may be density bounded, so that a significant fraction of the ionizing photons emitted by their exciting OB stars escape from the regions. The key piece of evidence is the presence, in the Ha luminosity functions (LFs) of the populations of H iI regions, of glitches, local sharp peaks at an apparently invariant luminosity, defined as the Stromgren luminosity Lstr), LH(sub alpha) = Lstr = 10(sup 38.6) (+/- 10(sup 0.1)) erg/ s (no other peaks are found in any of the LFs) accompanying a steepening of slope for LH(sub alpha) greater than Lstr This behavior is readily explicable via a physical model whose basic premises are: (a) the transition at LH(sub alpha) = Lstr marks a change from essentially ionization bounding at low luminosities to density bounding at higher values, (b) for this to occur the law relating stellar mass in massive star-forming clouds to the mass of the placental cloud must be such that the ionizing photon flux produced within the cloud is a function which rises more steeply than the mass of the cloud. Supporting evidence for the hypothesis of this transition is also presented: measurements of the central surface brightnesses of H II regions for LH(sub alpha) less than Lstr are proportional to L(sup 1/3, sub H(sub alpha)), expected for ionization bounding, but show a sharp trend to a steeper dependence for LH(sub alpha) greater than Lstr, and the observed relation between the internal turbulence velocity parameter, sigma, and the luminosity, L, at high luminosities, can be well explained if these regions are density bounded. If confirmed, the density-bounding hypothesis would have a number of interesting implications. It would imply that the density-bounded regions were the main sources of the photons which ionize the diffuse gas in disk galaxies. Our estimates, based on the hypothesis, indicate that these regions emit sufficient Lyman continuum not only to

  2. Evidence for a Wide Range of Ultraviolet Obscuration in z ~ 2 Dusty Galaxies from the GOODS-Herschel Survey

    NASA Astrophysics Data System (ADS)

    Penner, Kyle; Dickinson, Mark; Pope, Alexandra; Dey, Arjun; Magnelli, Benjamin; Pannella, Maurilio; Altieri, Bruno; Aussel, Herve; Buat, Veronique; Bussmann, Shane; Charmandaris, Vassilis; Coia, Daniela; Daddi, Emanuele; Dannerbauer, Helmut; Elbaz, David; Hwang, Ho Seong; Kartaltepe, Jeyhan; Lin, Lihwai; Magdis, Georgios; Morrison, Glenn; Popesso, Paola; Scott, Douglas; Valtchanov, Ivan

    2012-11-01

    Dusty galaxies at z ~ 2 span a wide range of relative brightness between rest-frame mid-infrared (8 μm) and ultraviolet wavelengths. We attempt to determine the physical mechanism responsible for this diversity. Dust-obscured galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios >~ 1000, might be abnormally bright in the mid-IR, perhaps due to prominent emission from active galactic nuclei and/or polycyclic aromatic hydrocarbons, or abnormally faint in the UV. We use far-infrared data from the GOODS-Herschel survey to show that most DOGs with 1012 L ⊙ <~ L IR <~ 1013 L ⊙ are not abnormally bright in the mid-IR when compared to other dusty galaxies with similar IR (8-1000 μm) luminosities. We observe a relation between the median IR to UV luminosity ratios and the median UV continuum power-law indices for these galaxies, and we find that only 24% have specific star formation rates that indicate the dominance of compact star-forming regions. This circumstantial evidence supports the idea that the UV- and IR-emitting regions in these galaxies are spatially coincident, which implies a connection between the abnormal UV faintness of DOGs and dust obscuration. We conclude that the range in rest-frame mid-IR to UV flux density ratios spanned by dusty galaxies at z ~ 2 is due to differing amounts of UV obscuration. Of galaxies with these IR luminosities, DOGs are the most obscured. We attribute differences in UV obscuration to either (1) differences in the degree of alignment between the spatial distributions of dust and massive stars or (2) differences in the total dust content. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  3. EVIDENCE FOR A WIDE RANGE OF ULTRAVIOLET OBSCURATION IN z {approx} 2 DUSTY GALAXIES FROM THE GOODS-HERSCHEL SURVEY

    SciTech Connect

    Penner, Kyle; Dickinson, Mark; Dey, Arjun; Kartaltepe, Jeyhan; Pope, Alexandra; Magnelli, Benjamin; Pannella, Maurilio; Aussel, Herve; Daddi, Emanuele; Elbaz, David; Buat, Veronique; Bussmann, Shane; Hwang, Ho Seong; Charmandaris, Vassilis; Dannerbauer, Helmut; Lin Lihwai; Magdis, Georgios; Morrison, Glenn; and others

    2012-11-01

    Dusty galaxies at z {approx} 2 span a wide range of relative brightness between rest-frame mid-infrared (8 {mu}m) and ultraviolet wavelengths. We attempt to determine the physical mechanism responsible for this diversity. Dust-obscured galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios {approx}> 1000, might be abnormally bright in the mid-IR, perhaps due to prominent emission from active galactic nuclei and/or polycyclic aromatic hydrocarbons, or abnormally faint in the UV. We use far-infrared data from the GOODS-Herschel survey to show that most DOGs with 10{sup 12} L {sub Sun} {approx}< L {sub IR} {approx}< 10{sup 13} L {sub Sun} are not abnormally bright in the mid-IR when compared to other dusty galaxies with similar IR (8-1000 {mu}m) luminosities. We observe a relation between the median IR to UV luminosity ratios and the median UV continuum power-law indices for these galaxies, and we find that only 24% have specific star formation rates that indicate the dominance of compact star-forming regions. This circumstantial evidence supports the idea that the UV- and IR-emitting regions in these galaxies are spatially coincident, which implies a connection between the abnormal UV faintness of DOGs and dust obscuration. We conclude that the range in rest-frame mid-IR to UV flux density ratios spanned by dusty galaxies at z {approx} 2 is due to differing amounts of UV obscuration. Of galaxies with these IR luminosities, DOGs are the most obscured. We attribute differences in UV obscuration to either (1) differences in the degree of alignment between the spatial distributions of dust and massive stars or (2) differences in the total dust content.

  4. MAGIICAT IV. Kinematics of the Circumgalactic Medium and Evidence for Quiescent Evolution Around Red Galaxies

    NASA Astrophysics Data System (ADS)

    Nielsen, Nikole M.; Churchill, Christopher W.; Kacprzak, Glenn G.; Murphy, Michael T.; Evans, Jessica L.

    2016-02-01

    The equivalent widths of {{Mg}} {{II}} absorption in the circumgalactic medium (CGM) trace the global star formation rate up to z < 6, are larger for star-forming galaxies than passively evolving galaxies, and decrease with increasing distance from the galaxy. We delve further into the physics involved by investigating gas kinematics and cloud column density distributions as a function of galaxy color, redshift, and projected distance from the galaxy (normalized by galaxy virial radius, D/Rvir). For 39 isolated galaxies at 0.3 < zgal < 1.0, we have detected {{Mg}} {{II}} absorption in high-resolution (Δv ≃ 6.6 km s-1) spectra of background quasars within a projected distance of 7 < D < 190 kpc. We characterize the absorption velocity spread using pixel-velocity two-point correlation functions. Velocity dispersions and cloud column densities for blue galaxies do not differ with redshift nor with D/Rvir. This suggests that outflows continually replenish the CGM of blue galaxies with high velocity dispersion, large column density gas out to large distances. Conversely, absorption hosted by red galaxies evolves with redshift where the velocity dispersions (column densities) are smaller (larger) at zgal < 0.656. After taking into account larger possible velocities in more massive galaxies, we find that there is no difference in the velocity dispersions or column densities for absorption hosted by red galaxies with D/Rvir. Thus, a lack of outflows in red galaxies causes the CGM to become more quiescent over time, with lower velocity dispersions and larger column densities toward lower zgal. The quenching of star formation appears to affect the CGM out to D/Rvir = 0.75.

  5. EVIDENCE FOR (AND AGAINST) PROGENITOR BIAS IN THE SIZE GROWTH OF COMPACT RED GALAXIES

    SciTech Connect

    Keating, Stephanie K.; Abraham, Roberto G.; Schiavon, Ricardo; Graves, Genevieve; Damjanov, Ivana; Yan, Renbin; Newman, Jeffrey; Simard, Luc

    2015-01-01

    Most massive, passive galaxies are compact at high redshifts, but similarly compact massive galaxies are rare in the local universe. The most common interpretation of this phenomenon is that massive galaxies have grown in size by a factor of about five since redshift z = 2. An alternative explanation is that recently quenched massive galaxies are larger (a {sup p}rogenitor bias{sup )}. In this paper, we explore the importance of progenitor bias by looking for systematic differences in the stellar populations of compact early-type galaxies in the DEEP2 survey as a function of size. Our analysis is based on applying the statistical technique of bootstrap resampling to constrain differences in the median ages of our samples and to begin to characterize the distribution of stellar populations in our co-added spectra. The light-weighted ages of compact early-type galaxies at redshifts 0.5 < z < 1.4 are compared to those of a control sample of larger galaxies at similar redshifts. We find that massive compact early-type galaxies selected on the basis of red color and high bulge-to-total ratio are younger than similarly selected larger galaxies, suggesting that size growth in these objects is not driven mainly by progenitor bias, and that individual galaxies grow as their stellar populations age. However, compact early-type galaxies selected on the basis of image smoothness and high bulge-to-total ratio are older than a control sample of larger galaxies. Progenitor bias will play a significant role in defining the apparent size changes of early-type galaxies if they are selected on the basis of the smoothness of their light distributions.

  6. The Lyα-LyC Connection: Evidence for an Enhanced Contribution of UV-faint Galaxies to Cosmic Reionization

    NASA Astrophysics Data System (ADS)

    Dijkstra, Mark; Gronke, Max; Venkatesan, Aparna

    2016-09-01

    The escape of ionizing Lyman continuum (LyC) photons requires the existence of low-N H i sightlines, which also promote escape of Lyα. We use a suite of 2500 Lyα Monte-Carlo radiative transfer simulations through models of dusty, clumpy interstellar (“multiphase”) media from Gronke & Dijkstra, and compare the escape fractions of Lyα ({f}{{esc}}{{Ly}α }) and LyC radiation ({f}{{esc}}{{ion}}). We find that {f}{{esc}}{{ion}} and {f}{{esc}}{{Ly}α } are correlated: galaxies with a low {f}{{esc}}{{Ly}α } consistently have a low {f}{{esc}}{{ion}}, while galaxies with a high {f}{{esc}}{{Ly}α } exhibit a large dispersion in {f}{{esc}}{{ion}}. We argue that there is increasing observational evidence that Lyα escapes more easily from UV-faint galaxies. The correlation between {f}{{esc}}{{ion}} and {f}{{esc}}{{Ly}α } then implies that UV-faint galaxies contribute more to the ionizing background than implied by the faint-end slope of the UV luminosity function. In multiphase gases, the ionizing escape fraction is most strongly affected by the cloud covering factor, f cl, which implies that {f}{{esc}}{{ion}} is closely connected to the observed Lyα spectral line shape. Specifically, LyC-emitting galaxies typically having narrower, more symmetric line profiles. This prediction is qualitatively similar to that for “shell models.”

  7. THE MOLECULAR GAS CONTENT OF z = 3 LYMAN BREAK GALAXIES: EVIDENCE OF A NON-EVOLVING GAS FRACTION IN MAIN-SEQUENCE GALAXIES AT z > 2

    SciTech Connect

    Magdis, Georgios E.; Rigopoulou, D.; Daddi, E.; Sargent, M.; Elbaz, D.; Gobat, R.; Tan, Q.; Aussel, H.; Feruglio, C.; Charmandaris, V.; Dickinson, M.; Reddy, N.

    2012-10-10

    We present observations of the CO[J = 3 {yields} 2] emission toward two massive and infrared luminous Lyman break galaxies (LBGs) at z = 3.21 and z = 2.92, using the IRAM Plateau de Bure Interferometer, placing first constraints on the molecular gas masses (M{sub gas}) of non-lensed LBGs. Their overall properties are consistent with those of typical (main-sequence) galaxies at their redshifts, with specific star formation rates {approx}1.6 and {approx}2.2 Gyr{sup -1}, despite their large infrared luminosities (L{sub IR} Almost-Equal-To (2-3) Multiplication-Sign 10{sup 12} L{sub Sun }) derived from Herschel. With one plausible CO detection (spurious detection probability of 10{sup -3}) and one upper limit, we investigate the evolution of the molecular gas-to-stellar mass ratio (M{sub gas}/M{sub *}) with redshift. Our data suggest that the steep evolution of M{sub gas}/M{sub *} of normal galaxies up to z {approx} 2 is followed by a flattening at higher redshifts, providing supporting evidence for the existence of a plateau in the evolution of the specific star formation rate at z > 2.5.

  8. Galaxy Zoo: evidence for diverse star formation histories through the green valley

    NASA Astrophysics Data System (ADS)

    Smethurst, R. J.; Lintott, C. J.; Simmons, B. D.; Schawinski, K.; Marshall, P. J.; Bamford, S.; Fortson, L.; Kaviraj, S.; Masters, K. L.; Melvin, T.; Nichol, R. C.; Skibba, R. A.; Willett, K. W.

    2015-06-01

    Does galaxy evolution proceed through the green valley via multiple pathways or as a single population? Motivated by recent results highlighting radically different evolutionary pathways between early- and late-type galaxies, we present results from a simple Bayesian approach to this problem wherein we model the star formation history (SFH) of a galaxy with two parameters, [t, τ] and compare the predicted and observed optical and near-ultraviolet colours. We use a novel method to investigate the morphological differences between the most probable SFHs for both disc-like and smooth-like populations of galaxies, by using a sample of 126 316 galaxies (0.01 < z < 0.25) with probabilistic estimates of morphology from Galaxy Zoo. We find a clear difference between the quenching time-scales preferred by smooth- and disc-like galaxies, with three possible routes through the green valley dominated by smooth- (rapid time-scales, attributed to major mergers), intermediate- (intermediate time-scales, attributed to minor mergers and galaxy interactions) and disc-like (slow time-scales, attributed to secular evolution) galaxies. We hypothesize that morphological changes occur in systems which have undergone quenching with an exponential time-scale τ < 1.5 Gyr, in order for the evolution of galaxies in the green valley to match the ratio of smooth to disc galaxies observed in the red sequence. These rapid time-scales are instrumental in the formation of the red sequence at earlier times; however, we find that galaxies currently passing through the green valley typically do so at intermediate time-scales.†

  9. Decreased Frequency of Strong Bars in S0 Galaxies: Evidence for Secular Evolution?

    NASA Astrophysics Data System (ADS)

    Buta, R.; Laurikainen, E.; Salo, H.; Knapen, J. H.

    2010-09-01

    Using data from the Near-Infrared S0 Survey of nearby, early-type galaxies, we examine the distribution of bar strengths in S0 galaxies as compared to S0/a and Sa galaxies, and as compared to previously published bar strength data for Ohio State University Bright Spiral Galaxy Survey spiral galaxies. Bar strengths based on the gravitational torque method are derived from 2.2 μm Ks -band images for a statistical sample of 138 (98 S0, 40 S0/a,Sa) galaxies having a mean total blue magnitude lang BT rang <= 12.5 and generally inclined less than 65°. We find that S0 galaxies have weaker bars on average than spiral galaxies in general, even compared to their closest spiral counterparts, S0/a and Sa galaxies. The differences are significant and cannot be entirely due to uncertainties in the assumed vertical scale heights or in the assumption of constant mass-to-light ratios. Part of the difference is likely simply due to the dilution of the bar torques by the higher mass bulges seen in S0s. If spiral galaxies accrete external gas, as advocated by Bournaud & Combes, then the fewer strong bars found among S0s imply a lack of gas accretion according to this theory. If S0s are stripped former spirals, or else are evolved from former spirals due to internal secular dynamical processes which deplete the gas as well as grow the bulges, then the weaker bars and the prevalence of lenses in S0 galaxies could further indicate that bar evolution continues to proceed during and even after gas depletion.

  10. Growing Galaxies Gently

    NASA Astrophysics Data System (ADS)

    2010-10-01

    of the flow of pristine gas from the surrounding space and the associated formation of new stars. They were very careful to make sure that their specimen galaxies had not been disturbed by interactions with other galaxies. The selected galaxies were very regular, smoothly rotating discs, similar to the Milky Way, and they were seen about two billion years after the Big Bang (at a redshift of around three). In galaxies in the modern Universe the heavy elements [1] are more abundant close to the centre. But when Cresci's team mapped their selected distant galaxies with the SINFONI spectrograph on the VLT [2] they were excited to see that in all three cases there was a patch of the galaxy, close to the centre, with fewer heavy elements, but hosting vigorously forming stars, suggesting that the material to fuel the star formation was coming from the surrounding pristine gas that is low in heavy elements. This was the smoking gun that provided the best evidence yet of young galaxies accreting primitive gas and using it to form new generations of stars. As Cresci concludes: "This study has only been possible because of the outstanding performance of the SINFONI instrument on the VLT. It has opened a new window for studying the chemical properties of very distant galaxies. SINFONI provides information not only in two spatial dimensions, but also in a third, spectral dimension, which allows us to see the internal motions inside galaxies and study the chemical composition of the interstellar gas." Notes [1] The gas filling the early Universe was almost all hydrogen and helium. The first generations of stars processed this primitive material to create heavier elements such as oxygen, nitrogen and carbon by nuclear fusion. When this material was subsequently spewed back into space by intense particle winds from massive young stars and supernova explosions the amounts of heavy elements in the galaxy gradually increased. Astronomers refer to elements other than hydrogen and

  11. X-ray evidence for ultra-fast outflows in Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Tombesi, Francesco; Braito, Valentina; Reeves, James; Cappi, Massimo; Dadina, Mauro

    2012-07-01

    X-ray evidence for massive, highly ionized, ultra-fast outflows (UFOs) has been recently reported in a number of AGNs through the detection of blue-shifted Fe XXV/XXVI absorption lines. We present the results of a comprehensive spectral analysis of a large sample of 42 local Seyferts observed with XMM-Newton. Similar results are also obtained from a Suzaku analysis of 5 radio galaxies. We find that UFOs are common phenomena, being present in >40% of the sources. Their outflow velocity distribution is in the range ˜0.03--0.3c, with mean value of ˜0.14c. The ionization parameter is very high, in the range logξ˜3--6 erg~s^{-1}~cm, and the associated column densities are also large, in the range ˜10^{22}--10^{24} cm^{-2}. Their location is constrained at ˜0.0003--0.03pc (˜10^2--10^4 r_s) from the central black hole, consistent with what is expected for accretion disk winds/outflows. The mass outflow rates are in the interval ˜0.01--1M_{⊙}~yr^{-1}. The associated mechanical power is also high, in the range ˜10^{43}--10^{45} erg/s, which indicates that UFOs are capable to provide a significant contribution to the AGN cosmological feedback.

  12. Preliminary Evidence of an Association Between a Functional IL6 Polymorphism and Fatigue and Sleep Disturbance in Oncology Patients and Their Family Caregivers

    PubMed Central

    Miaskowski, Christine; Dodd, Marylin; Lee, Kathryn; West, Claudia; Paul, Steven M.; Cooper, Bruce A.; Wara, William; Swift, Patrick S.; Dunn, Laura B.; Aouizerat, Bradley E.

    2010-01-01

    Context Fatigue and sleep disturbance are common problems in oncology patients and their family caregivers (FCs). However, little is known about factors that contribute to inter-individual variability in these symptoms or to their underlying biologic mechanisms. Objectives An evaluation was done on whether genetic variation in a prominent pro-inflammatory cytokine, interleukin 6 (IL6 c.-6101A>T (rs4719714)) was associated with mean ratings of evening fatigue, morning fatigue, and sleep disturbance, as well as with the trajectories of these symptoms. Methods Over six months, participants completed standardized measures of fatigue and sleep disturbance. Linear regression was used to assess the effect of the IL6 genotype and other covariates on mean fatigue and sleep disturbance scores. Hierarchical linear modeling was used to determine the effect of IL6 genotype on symptom trajectories. Common allele homozygotes reported higher levels of evening fatigue (P=0.003), morning fatigue (P=0.09), and sleep disturbance (P=0.003) than minor allele carriers. Predictors of baseline level and trajectories of evening fatigue included age, gender, and genotype (intercepts) and baseline level of evening fatigue (slope), respectively. Predictors of baseline level and trajectories of morning fatigue included age and genotype (intercept) and age and baseline level of morning fatigue (slope). Predictors of baseline level and trajectories of sleep disturbance included age and genotype (intercept) and baseline level of sleep disturbance (slope). Conclusions Findings provide preliminary evidence of a genetic association between a functional promoter polymorphism in the IL6 gene and severity of evening fatigue, morning fatigue, and sleep disturbance in oncology patients and their FCs. PMID:20570482

  13. Stellar mass function of cluster galaxies at z ~ 1.5: evidence for reduced quenching efficiency at high redshift

    NASA Astrophysics Data System (ADS)

    Nantais, Julie B.; van der Burg, Remco F. J.; Lidman, Chris; Demarco, Ricardo; Noble, Allison; Wilson, Gillian; Muzzin, Adam; Foltz, Ryan; DeGroot, Andrew; Cooper, Michael C.

    2016-08-01

    We present the stellar mass functions (SMFs) of passive and star-forming galaxies with a limiting mass of 1010.1M⊙ in four spectroscopically confirmed Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) galaxy clusters at 1.37 galaxies to a field sample derived from a similar Ks-band-selected catalog in the UltraVISTA/COSMOS field. The SMFs resemble those of the field, but with signs of environmental quenching. We find that 30 ± 20% of galaxies that would normally be forming stars in the field are quenched in the clusters. The environmental quenching efficiency shows little dependence on projected cluster-centric distance out to ~4 Mpc, providing tentative evidence of pre-processing and/or galactic conformity in this redshift range. We also compile the available data on environmental quenching efficiencies from the literature, and find that the quenching efficiency in clusters and in groups appears to decline with increasing redshift in a manner consistent with previous results and expectations based on halo mass growth.

  14. Morphological Transformation from Galaxy Harassment

    NASA Astrophysics Data System (ADS)

    Moore, Ben; Lake, George; Katz, Neal

    1998-03-01

    Galaxy morphologies in clusters have undergone a remarkable transition over the past several billion yr. Distant clusters at z ~ 0.4 are filled with small spiral galaxies, many of which are disturbed and show evidence of multiple bursts of star formation. This population is absent from nearby clusters, where spheroidals comprise the faint end of the luminosity function. Our numerical simulations follow the evolution of disk galaxies in a rich cluster resulting from encounters with brighter galaxies and the cluster's tidal field, or ``galaxy harassment.'' After a bursting transient phase, they undergo a complete morphological transformation from ``disks'' to ``spheroidals.'' We examine the remnants and find support for our theory in detailed comparisons of the photometry and kinematics of the spheroidal galaxies in clusters. Our model naturally accounts for the intermediate-age stellar population seen in these spheroidals, as well as for the trend in the dwarf-to-giant ratio with cluster richness. The final shapes are typically prolate and are flattened primarily by velocity anisotropy. Their mass-to-light ratios are in the range 3-8, in good agreement with observations.

  15. DYNAMICAL VERSUS STELLAR MASSES IN COMPACT EARLY-TYPE GALAXIES: FURTHER EVIDENCE FOR SYSTEMATIC VARIATION IN THE STELLAR INITIAL MASS FUNCTION

    SciTech Connect

    Conroy, Charlie; Dutton, Aaron A.; Graves, Genevieve J.; Mendel, J. Trevor; Van Dokkum, Pieter G.

    2013-10-20

    Several independent lines of evidence suggest that the stellar initial mass function (IMF) in early-type galaxies becomes increasingly 'bottom-heavy' with increasing galaxy mass and/or velocity dispersion, σ. Here we consider evidence for IMF variation in a sample of relatively compact early-type galaxies drawn from the Sloan Digital Sky Survey. These galaxies are of sufficiently high stellar density that a dark halo likely makes a minor contribution to the total dynamical mass, M {sub dyn}, within one effective radius. We fit our detailed stellar population synthesis models to the stacked absorption line spectra of these galaxies in bins of σ and find evidence from IMF-sensitive spectral features for a bottom-heavy IMF at high σ. We also apply simple 'mass-follows-light' dynamical models to the same data and find that M {sub dyn} is significantly higher than what would be expected if these galaxies were stellar dominated and had a universal Milky Way IMF. Adopting M {sub dyn} ≈ M {sub *} therefore implies that the IMF is 'heavier' at high σ. Most importantly, the quantitative amount of inferred IMF variation is very similar between the two techniques, agreeing to within ∼< 0.1 dex in mass. The agreement between two independent techniques, when applied to the same data, provides compelling evidence for systematic variation in the IMF as a function of early-type galaxy velocity dispersion. Any alternative explanations must reproduce both the results from dynamical and stellar population-based techniques.

  16. The inner regions of the spiral galaxy NGC 3310 - Evidence for galactic cannibalism

    NASA Astrophysics Data System (ADS)

    Balick, B.; Heckman, T.

    1981-03-01

    High resolution optical and radio images of the inner regions of NGC 3310 are presented. Subtle but important differences exist in the distributions of the stellar continuum on the one hand and the ionized gas and high energy particles on the other. These data and others suggest that a galaxy-galaxy collision has lead to a major disruption in the inner regions which has not yet fully relaxed even at radii of 0.5-1 kpc where the relaxation time scales are only 10 to the power 7.8 yr. An encounter in which an Irr 1 galaxy is being cannibalized by NGC 3110 provides a scenario for the recent history of the galaxy which is in accord with published observations.

  17. Evidence for the Rapid Formation of Low-mass Early-type Galaxies in Dense Environments

    NASA Astrophysics Data System (ADS)

    Liu, Yiqing; Peng, Eric W.; Blakeslee, John; Côté, Patrick; Ferrarese, Laura; Jordán, Andrés; Puzia, Thomas H.; Toloba, Elisa; Zhang, Hong-Xin

    2016-02-01

    We explore the environmental dependence of star formation timescales in low-mass galaxies using the [α/Fe] abundance ratio as an evolutionary clock. We present integrated [α/Fe] measurements for 11 low-mass ({M}\\star ˜ {10}9 {M}⊙ ) early-type galaxies (ETGs) with a large range of cluster-centric distance in the Virgo Cluster. We find a gradient in [α/Fe], where the galaxies closest to the cluster center (the cD galaxy, M87) have the highest values. This trend is driven by galaxies within a projected radius of 0.4 Mpc (0.26 times the virial radius of Virgo A), all of which have super-solar [α/Fe]. Galaxies in this mass range exhibit a large scatter in the [α/Fe]-σ diagram, and do not obviously lie on an extension of the relation defined by massive ETGs. In addition, we find a correlation between [α/Fe] and globular cluster specific frequency (SN), suggesting that low-mass ETGs that formed their stars over a short period of time were also efficient at forming massive star clusters. The innermost low-mass ETGs in our sample have [α/Fe] values comparable to that of M87, implying that environment is the controlling factor for star formation timescales in dense regions. These low-mass galaxies could be the surviving counterparts of the objects that have already been accreted into the halo of M87, and may be the link between present-day low-mass galaxies and the old, metal-poor, high-[α/Fe], high-SN stellar populations seen in the outer halos of massive ETGs.

  18. New observations of z ∼ 7 galaxies: evidence for a patchy reionization

    SciTech Connect

    Pentericci, L.; Fontana, A.; Castellano, M.; Grazian, A.; Galametz, A.; Giallongo, E.; Paris, D.; Santini, P.; Vanzella, E.; Treu, T.; Mesinger, A.; Dijkstra, M.; Bradač, M.; Conselice, C.; Cristiani, S.; Dunlop, J.; McLure, R.; Giavalisco, M.; Koekemoer, A.; Maiolino, R.

    2014-10-01

    We present new results from our search for z ∼ 7 galaxies from deep spectroscopic observations of candidate z dropouts in the CANDELS fields. Despite the extremely low flux limits achieved by our sensitive observations, only two galaxies have robust redshift identifications, one from its Lyα emission line at z = 6.65, the other from its Lyman break, i.e., the continuum discontinuity at the Lyα wavelength consistent with a redshift of 6.42 but with no emission line. In addition, for 23 galaxies we present deep limits in the Lyα equivalent width derived from the nondetections in ultradeep observations. Using this new data as well as previous samples, we assemble a total of 68 candidate z ∼ 7 galaxies with deep spectroscopic observations, of which 12 have a line detection. With this much enlarged sample we can place solid constraints on the declining fraction of Lyα emission in z ∼ 7 Lyman-break galaxies compared to z ∼ 6, both for bright and faint galaxies. Applying a simple analytical model, we show that the present data favor a patchy reionization process rather than a smooth one.

  19. Observational evidence of a slow downfall of star formation efficiency in massive galaxies during the past 10 Gyr

    NASA Astrophysics Data System (ADS)

    Schreiber, C.; Elbaz, D.; Pannella, M.; Ciesla, L.; Wang, T.; Koekemoer, A.; Rafelski, M.; Daddi, E.

    2016-05-01

    We study the causes of the reported mass-dependence in the slope of the SFR-M∗ relation, the so-called main sequence of star-forming galaxies, and discuss its implication on the physical processes that shaped the star formation history of massive galaxies over cosmic time. We made use of the near-infrared high-resolution imaging from the Hubble Space Telescope in the CANDELS fields to perform a careful bulge-to-disk decomposition of distant galaxies and measure for the first time the slope of the SFR-Mdisk relation at z = 1. We find that this relation very closely follows the shape of the nominal SFR-M∗ correlation, still with a pronounced flattening at the high-mass end. This clearly excludes, at least at z = 1, the progressive growth of quiescent stellar bulges in star-forming galaxies as the main driver for the change of slope of the main sequence. Then, by stacking the Herschel data available in the CANDELS field, we estimated the gas mass (Mgas = MH i + MH2) and the star formation efficiency (SFE ≡ SFR/Mgas) at different positions on the SFR-M∗ relation. We find that the relatively low SFRs observed in massive galaxies (M∗> 5 × 1010 M⊙) are not caused by a reduced gas content, but by a star formation efficiency that is lower by up to a factor of 3 than in galaxies with lower stellar mass. The trend at the lowest masses is probably linked to the dominance of atomic over molecular gas. We argue that this stellar-mass-dependent SFE can explain the varying slope of the main sequence since z = 1.5, hence over 70% of the Hubble time. The drop in SFE occurs at lower masses in the local Universe (M∗> 2 × 1010 M⊙) and is not present at z = 2. Altogether, this provides evidence for a slow decrease in star formation efficiency in massive main sequence galaxies. The resulting loss of star formation is found to be rising starting from z = 2 to reach a level similar to the mass growth of the quiescent population by z = 1. We finally discuss the possible

  20. Star-forming galaxies in low-redshift clusters: comparison of integrated properties of cluster and field galaxies

    NASA Astrophysics Data System (ADS)

    Bretherton, C. F.; James, P. A.; Moss, C.; Whittle, M.

    2010-12-01

    Aims: We investigate the effect of the cluster environment on the star formation properties of galaxies in 8 nearby Abell clusters. Methods: Star formation properties are determined for individual galaxies using the equivalent width of Hα+[Nii] line emission from narrow-band imaging. Equivalent width distributions are derived for each galaxy type in each of 3 environments - cluster, supercluster (outside the cluster virial radius) and field. The effects of morphological disturbance on star formation are also investigated. Results: We identify a population of early-type disk galaxies in the cluster population with enhanced star formation compared to their field counterparts. The enhanced cluster galaxies frequently show evidence of disturbance, and the disturbed galaxies show marginal evidence for a higher velocity dispersion, possibly indicative of an infalling population. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias; and with the Jacobus Kapteyn Telescope, which was operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  1. Evidence for indirect effects of pain catastrophizing on clinical pain among myofascial temporomandibular disorder participants: the mediating role of sleep disturbance.

    PubMed

    Buenaver, Luis F; Quartana, Phillip J; Grace, Edward G; Sarlani, Eleni; Simango, Mpepera; Edwards, Robert R; Haythornthwaite, Jennifer A; Smith, Michael T

    2012-06-01

    Sleep disturbance and pain catastrophizing are important mediators of the chronic pain experience. To date, these factors have not been considered concurrently despite compelling theoretical rationale to do so. In the present study, we examined whether pain catastrophizing not only has direct effects on clinical pain and pain-related interference, but also indirect effects through its association with sleep disturbance. We evaluated this hypothesis using a cohort (n=214) of myofascial temporomandibular disorder participants using a statistical bootstrapping technique recommended for tests of indirect effects. Results suggested that pain catastrophizing was associated with greater sleep disturbance, and that a significant portion of variance in clinical pain severity and pain-related interference attributable to pain catastrophizing was mediated by sleep disturbance. Supplementary analyses revealed that the rumination component of catastrophizing seemed to be indirectly related to clinical outcomes through sleep disturbance. No evidence for indirect effects was observed for helplessness and magnification components. These results suggest that rumination about pain may contribute to clinical pain indirectly through alterations in sleep. Prospective studies are needed to examine lagged associations between these constructs. These findings have important theoretical and clinical implications. Critically, interventions that reduce pain catastrophizing may concurrently improve sleep and clinical pain. PMID:22417656

  2. Tidal Interactions at the Edge of the Local Group: New Evidence for Tidal Features in the Antlia Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Penny, Samantha J.; Pimbblet, Kevin A.; Conselice, Christopher J.; Brown, Michael J. I.; Grützbauch, Ruth; Floyd, David J. E.

    2012-10-01

    Using deep B-band imaging down to ~μ B = 26 mag arcsec-2, we present evidence for tidal tails in the Antlia Dwarf galaxy, one of the most distant members of the Local Group. This elongation is in the direction of Antlia's nearest neighbor, the Magellanic-type NGC 3109. The tail is offset by <10° from a vector linking the centers of the two galaxies, indicative of interactions between the pair. Combined with the warped disk previously identified in NGC 3109, Antlia and NGC 3109 must be at a small separation for tidal features to be present in Antlia. We calculate that Antlia cannot be completely disrupted by NGC 3109 in a single interaction unless its orbit pericenter is <6 kpc; however, multiple interactions could significantly alter its morphology. Therefore despite being located right at the edge of the Local Group, environmental effects are playing an important role in Antlia's evolution.

  3. TIDAL INTERACTIONS AT THE EDGE OF THE LOCAL GROUP: NEW EVIDENCE FOR TIDAL FEATURES IN THE ANTLIA DWARF GALAXY

    SciTech Connect

    Penny, Samantha J.; Pimbblet, Kevin A.; Brown, Michael J. I.; Floyd, David J. E.; Conselice, Christopher J.; Gruetzbauch, Ruth

    2012-10-20

    Using deep B-band imaging down to {approx}{mu}{sub B} = 26 mag arcsec{sup -2}, we present evidence for tidal tails in the Antlia Dwarf galaxy, one of the most distant members of the Local Group. This elongation is in the direction of Antlia's nearest neighbor, the Magellanic-type NGC 3109. The tail is offset by <10 Degree-Sign from a vector linking the centers of the two galaxies, indicative of interactions between the pair. Combined with the warped disk previously identified in NGC 3109, Antlia and NGC 3109 must be at a small separation for tidal features to be present in Antlia. We calculate that Antlia cannot be completely disrupted by NGC 3109 in a single interaction unless its orbit pericenter is <6 kpc; however, multiple interactions could significantly alter its morphology. Therefore despite being located right at the edge of the Local Group, environmental effects are playing an important role in Antlia's evolution.

  4. EVIDENCE FOR LOW EXTINCTION IN ACTIVELY STAR-FORMING GALAXIES AT z > 6.5

    SciTech Connect

    Walter, F.; Decarli, R.; Carilli, C.; Riechers, D.; Bertoldi, F.; Weiss, A.; Cox, P.; Neri, R.; Maiolino, R.; Ouchi, M.; Egami, E.

    2012-06-20

    We present a search for the [C II] 158 {mu}m fine structure line (a main cooling line of the interstellar medium) and the underlying far-infrared (FIR) continuum in three high-redshift (6.6 < z < 8.2) star-forming galaxies using the IRAM Plateau de Bure Interferometer. We targeted two Ly{alpha}-selected galaxies (Ly{alpha} emitters, LAEs) with moderate UV-based star formation rates (SFRs {approx} 20 M{sub Sun} yr{sup -1}; Himiko at z = 6.6 and IOK-1 at z = 7.0) and a gamma-ray burst (GRB) host galaxy (GRB 090423 at z {approx} 8.2). Based on our 3{sigma} rest-frame FIR continuum limits, previous (rest-frame) UV continuum measurements and spectral energy distribution (SED) fitting, we rule out SED shapes similar to highly obscured galaxies (e.g., Arp 220, M 82) and less extreme dust-rich nearby spiral galaxies (e.g., M 51) for the LAEs. Conservatively assuming an SED shape typical of local spiral galaxies we derive upper limits for the FIR-based star formation rates (SFRs) of {approx}70 M{sub Sun} yr{sup -1}, {approx}50 M{sub Sun} yr{sup -1}, and {approx}40 M{sub Sun} yr{sup -1} for Himiko, IOK-1, and GRB 090423, respectively. For the LAEs these limits are only a factor {approx}3 higher than the published UV-based SFRs (uncorrected for extinction). This indicates that the dust obscuration in the z > 6 LAEs studied here is lower by a factor of a few than what has recently been found in some LAEs at lower redshift (2 < z < 3.5) with similar UV-based SFRs. A low obscuration in our z > 6 LAE sample is consistent with recent rest-frame UV studies of z {approx} 7 Lyman break galaxies.

  5. Structural Properties and Evidence for Interactions in a Sample of Luminous Blue Compact Galaxies

    NASA Astrophysics Data System (ADS)

    Newton, Cassidy L.; Fanelli, M.; Marcum, P.

    2010-01-01

    Understanding the life cycles of galaxies over cosmic time is a primary effort in modern astrophysics. Here we explore the nature of luminous blue compact galaxies (LBCGs), a class of galaxy in the local (z < 0.05) universe exhibiting blue optical colors [(B-V) < 0.5], high luminosity (MB < -19), one or more high surface brightness regions, and moderate to high star formation rates [> 5 M(sun) per year]. LBCGs appear to be similar in their global properties to the early evolutionary phases of most galaxies, but are more amenable to detailed analysis due to their low redshifts. We describe an ultraviolet and optical investigation of a sample of 50 LBCGs using UBVR & Hα imagery obtained at McDonald Observatory, ultraviolet photometry from GALEX, and correlative data from IRAS, 2MASS, and SDSS. Using these data, we explore the evolutionary state of LBCGs. In particular, we determine the radial and azimuthal light distributions, explore the spatial extent of ionized gas (e.g., centrally- concentrated versus spatially diffuse), compare multiwavelength measures of the high-mass star formation rate, and quantify the interaction strength using a variety of merger diagnostics. Although selected independent of their environment, most systems display either a close companion or the signature of an interaction such as tails, bridges, and possible polar rings. Interpretation of the assembly history of LBCGs provides insight on massive galaxy evolution at earlier epochs.

  6. AN OSIRIS STUDY OF THE GAS KINEMATICS IN A SAMPLE OF UV-SELECTED GALAXIES: EVIDENCE OF 'HOT AND BOTHERED' STARBURSTS IN THE LOCAL UNIVERSE

    SciTech Connect

    Basu-Zych, Antara R.; Schiminovich, David; O'Dowd, Matt; Goncalves, Thiago S.; Martin, Chris; Wyder, Ted; Overzier, Roderik; Law, David R.; Heckman, Tim E-mail: ds@astro.columbia.edu E-mail: tsg@astro.caltech.edu E-mail: wyder@srl.caltech.edu E-mail: heckman@pha.jhu.edu

    2009-07-10

    We present data from Integral Field Spectroscopy for three supercompact UV-Luminous Galaxies (ScUVLGs). As nearby (z {approx} 0.2) compact (R {sub 50} {approx} 1-2 kpc) bright Paschen-{alpha} sources, with unusually high star formation rates (SFR = 3-100 M {sub sun} yr{sup -1}), ScUVLGs are an ideal population for studying detailed kinematics and dynamics in actively star-forming galaxies. In addition, ScUVLGs appear to be excellent analogs to high-redshift Lyman Break Galaxies (LBGs), and our results may offer additional insight into the dynamics of LBGs. Previous work by our team has shown that the morphologies of these galaxies exhibit tidal features and companions, and in this study we find that the dynamics of ScUVLGs are dominated by disturbed kinematics of the emission line gas-suggesting that these galaxies have undergone recent feedback, interactions, or mergers. While two of the three galaxies do display rotation, v/{sigma}<1-suggesting dispersion-dominated kinematics rather than smooth rotation. We also simulate how these observations would appear at z {approx} 2. Lower resolution and loss of low surface brightness features cause some apparent discrepancies between the low-z (observed) and high-z (simulated) interpretations and quantitatively gives different values for v/{sigma}, yet simulations of these low-z analogs manage to detect the brightest regions well and resemble actual high-z observations of LBGs.

  7. Evidence of boosted 13CO/12CO ratio in early-type galaxies in dense environments

    NASA Astrophysics Data System (ADS)

    Alatalo, Katherine; Crocker, Alison F.; Aalto, Susanne; Davis, Timothy A.; Nyland, Kristina; Bureau, Martin; Duc, Pierre-Alain; Krajnović, Davor; Young, Lisa M.

    2015-07-01

    We present observations of 13CO(1-0) in 17 Combined Array for Research in Millimeter Astronomy ATLAS3D early-type galaxies (ETGs), obtained simultaneously with 12CO(1-0) observations. The 13CO in six ETGs is sufficiently bright to create images. In these six sources, we do not detect any significant radial gradient in the 13CO/12CO ratio between the nucleus and the outlying molecular gas. Using the 12CO channel maps as 3D masks to stack the 13CO emission, we are able to detect 15/17 galaxies to >3σ (and 12/17 to at least 5σ) significance in a spatially integrated manner. Overall, ETGs show a wide distribution of 13CO/12CO ratios, but Virgo cluster and group galaxies preferentially show a 13CO/12CO ratio about two times larger than field galaxies, although this could also be due to a mass dependence, or the CO spatial extent (RCO/Re). ETGs whose gas has a morphologically settled appearance also show boosted 13CO/12CO ratios. We hypothesize that this variation could be caused by (i) the extra enrichment of gas from molecular reprocessing occurring in low-mass stars (boosting the abundance of 13C to 12C in the absence of external gas accretion), (ii) much higher pressure being exerted on the mid-plane gas (by the intracluster medium) in the cluster environment than in isolated galaxies, or (iii) all but the densest molecular gas clumps being stripped as the galaxies fall into the cluster. Further observations of 13CO in dense environments, particularly of spirals, as well as studies of other isotopologues, should be able to distinguish between these hypotheses.

  8. Evidence for Three Subpopulations of Globular Clusters in the Early-Type Poststarburst Shell Galaxy AM 0139-655

    NASA Astrophysics Data System (ADS)

    Maybhate, Aparna; Goudfrooij, Paul; Schweizer, François; Puzia, Thomas; Carter, David

    2007-11-01

    We present deep Hubble Space Telescope ACS images of the poststarburst shell galaxy AM 0139-655. We find evidence for the presence of three distinct globular cluster (GC) subpopulations associated with this galaxy: a centrally concentrated young population (~0.4 Gyr), an intermediate-age population (~1 Gyr), and an old, metal-poor population similar to that seen around normal galaxies. The g - I color distribution of the clusters is bimodal, with peaks at 0.85 and 1.35. The redder peak at g - I = 1.35 is consistent with the predicted color for an old, metal-poor population. The clusters associated with the peak at g - I = 0.85 are centrally concentrated and interpreted as a younger and more metal-rich population. We suggest that these clusters have an age of ~0.4 Gyr and solar metallicity based on a comparison with population synthesis models. The luminosity function of these "blue" clusters is well represented by a power law, phi(L) dL ~ L-1.8 dL. Interestingly, the brightest shell associated with the galaxy harbors some of the youngest clusters observed. This seems to indicate that the same merger event was responsible for the formation of both the shells and the young clusters. The red part of the color distribution contains several very bright clusters, which are not expected for an old, metal-poor population. Furthermore, the luminosity function of the "red" GCs cannot be fit well by either a single Gaussian or a single power law. A composite (Gaussian + power law) fit to the luminosity function of the red clusters yields both a low rms and very plausible properties for an old population (with a Gaussian distribution), plus an intermediate-age population (with a power-law distribution) of GCs. Hence, we suggest that the red clusters in AM 0139-655 consist of two distinct GC subpopulations, one being an old, metal-poor population as seen in normal galaxies and one having formed during a recent dissipative galaxy merger (likely the same event that formed the ~0

  9. DISTANT CLUSTER OF GALAXIES [left

    NASA Technical Reports Server (NTRS)

    2002-01-01

    One of the deepest images to date of the universe, taken with NASA's Hubble Space Telescope (HST), reveals thousands of faint galaxies at the detection limit of present day telescopes. Peering across a large volume of the observable cosmos, Hubble resolves thousands of galaxies from five to twelve billion light-years away. The light from these remote objects has taken billions of years to cross the expanding universe, making these distant galaxies fossil evidence' of events that happened when the universe was one-third its present age. A fraction of the galaxies in this image belong to a cluster located nine billion light-years away. Though the field of view (at the cluster's distance) is only two million light-years across, it contains a multitude of fragmentary objects. (By comparison, the two million light-years between our Milky Way galaxy and its nearest large companion galaxy, in the constellation Andromeda, is essentially empty space!) Very few of the cluster's members are recognizable as normal spiral galaxies (like our Milky Way), although some elongated members might be edge-on disks. Among this zoo of odd galaxies are ``tadpole-like'' objects, disturbed and apparently merging systems dubbed 'train-wrecks,' and a multitude of faint, tiny shards and fragments, dwarf galaxies or possibly an unknown population of objects. However, the cluster also contains red galaxies that resemble mature examples of today's elliptical galaxies. Their red color comes from older stars that must have formed shortly after the Big Bang. The image is the full field view of the Wide Field and Planetary Camera-2. The picture was taken in intervals between May 11 and June 15, 1994 and required an 18-hour long exposure, over 32 orbits of HST, to reveal objects down to 29th magnitude. [bottom right] A close up view of the peculiar radio galaxy 3C324 used to locate the cluster. The galaxy is nine billion light-years away as measured by its spectral redshift (z=1.2), and located in the

  10. Star Formation and Gas Accretion in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Yim, Kijeong; van der Hulst, J. M.

    2016-08-01

    In order to quantify the relationship between gas accretion and star formation, we analyse a sample of 29 nearby galaxies from the WHISP survey which contains galaxies with and without evidence for recent gas accretion. We compare combined radial profiles of FUV (GALEX) and IR 24 μm (Spitzer) characterizing distributions of recent star formation with radial profiles of CO (IRAM, BIMA, or CARMA) and H I (WSRT) tracing molecular and atomic gas contents to examine star formation efficiencies in symmetric (quiescent), asymmetric (accreting), and interacting (tidally disturbed) galaxies. In addition, we investigate the relationship between star formation rate and H I in the outer discs for the three groups of galaxies. We confirm the general relationship between gas surface density and star formation surface density, but do not find a significant difference between the three groups of galaxies.

  11. Human disturbance threats the red-listed macrolichen Seirophora villosa (Ach.) Frödén in coastal Juniperus habitats: evidence from western peninsular Italy.

    PubMed

    Benesperi, Renato; Lastrucci, Lorenzo; Nascimbene, Juri

    2013-10-01

    In Europe, coastal dune systems with Juniperus spp. (Natura 2000 habitat code 2250) are a priority habitat for conservation according to the Natura 2000 policies. Currently, anthropogenic pressure is threatening the biodiversity of this habitat. While the impact of human pressure on animals and vascular plants is already documented, information is still scanty for other organisms such as epiphytic lichens. The main aim of this study is to test the effect of human disturbance on the occurrence and abundance of the red-listed macrolichen Seirophora villosa. We also tested the effect of human disturbance on the whole community of epiphytic lichens in terms of species richness and composition. The study was performed along the coast of Tuscany by comparing both disturbed and undisturbed Juniperus stands according to a stratified random sampling design. Our results provided evidence that in coastal systems the long-term conservation of the red-listed macrolichen S. villosa and its characteristic community composed by several Mediterranean species of conservation concern depends on the maintenance of undisturbed Juniperus habitats. Results also support the possibility of using S. villosa as an indicator species of habitat conservation importance and habitat integrity since its occurrence is predicted on nestedness in term of species composition, assemblages of species poor disturbed stands being subsets of those of richer undisturbed stands.

  12. Human Disturbance Threats the Red-Listed Macrolichen Seirophora villosa (Ach.) Frödén in Coastal Juniperus Habitats: Evidence From Western Peninsular Italy

    NASA Astrophysics Data System (ADS)

    Benesperi, Renato; Lastrucci, Lorenzo; Nascimbene, Juri

    2013-10-01

    In Europe, coastal dune systems with Juniperus spp. (Natura 2000 habitat code 2250) are a priority habitat for conservation according to the Natura 2000 policies. Currently, anthropogenic pressure is threatening the biodiversity of this habitat. While the impact of human pressure on animals and vascular plants is already documented, information is still scanty for other organisms such as epiphytic lichens. The main aim of this study is to test the effect of human disturbance on the occurrence and abundance of the red-listed macrolichen Seirophora villosa. We also tested the effect of human disturbance on the whole community of epiphytic lichens in terms of species richness and composition. The study was performed along the coast of Tuscany by comparing both disturbed and undisturbed Juniperus stands according to a stratified random sampling design. Our results provided evidence that in coastal systems the long-term conservation of the red-listed macrolichen S. villosa and its characteristic community composed by several Mediterranean species of conservation concern depends on the maintenance of undisturbed Juniperus habitats. Results also support the possibility of using S. villosa as an indicator species of habitat conservation importance and habitat integrity since its occurrence is predicted on nestedness in term of species composition, assemblages of species poor disturbed stands being subsets of those of richer undisturbed stands.

  13. Evidence of nuclear disks in starburst galaxies from their radial distribution of supernovae

    NASA Astrophysics Data System (ADS)

    Herrero-Illana, R.; Pérez-Torres, M. Á.; Alberdi, A.

    2012-04-01

    Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ~100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M 82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.''1) radio observations published in the literature (for M 82 and Arp 220), or obtained by ourselves from the European VLBI Network (Arp 299-A). Our main goal was to characterize the nuclear starbursts in those galaxies and thus test scenarios that propose that nuclear disks of sizes ~100 pc form in the central regions of starburst galaxies. We obtained the radial distribution of supernovae (SNe) in the nuclear starbursts of M 82, Arp 299-A, and Arp 220, and derived scale-length values for the putative nuclear disks powering the bursts in those central regions. The scale lengths for the (exponential) disks range from ~20-30 pc for Arp 299-A and Arp 220, up to ~140 pc for M 82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. Our results support scenarios where a nuclear disk of size ~100 pc is formed in (U)LIRGs, and sustained by gas pressure, in which case the accretion onto the black hole could be lowered by supernova feedback. Appendices are available in electronic form at http://www.aanda.org

  14. Quantitative determination of microbial activity and community nutritional status in estuarine sediments: evidence for a disturbance artifact

    NASA Technical Reports Server (NTRS)

    Findlay, R. H.; Pollard, P. C.; Moriarty, D. J.; White, D. C.

    1985-01-01

    In estuarine sediments with a high degree of vertical heterogeneity in reduced substrate and terminal electron acceptor concentrations, the method of exposure of the microbiota to labeled substrates can introduce a "disturbance artifact" into measures of metabolic activity. The detection of this artifact is based on quantitative measurement of the relative rates of incorporation of [14C]acetate into phospholipid fatty acids (PLFA) and endogenous storage lipid, poly-beta-hydroxyalkanoate (PHA). Previous studies have shown that PLFA synthesis measures cellular growth and that PHA synthesis measures carbon accumulation (unbalanced growth). The "disturbance artifact" of exposure to [14C]acetate was demonstrated by comparing injection of a core with the usual or pore-water replacement or slurry techniques. Only injection of labeled substrate allowed detection of preassay disturbance of the sediment with a garden rake. The raking increased PLFA synthesis with little effect to differences in concentration or distribution of [14C]acetate in the 10-min incubation. Bioturbation induced by sand dollar feeding in estuarine sediment could be detected in an increased PLFA/PHA ratio which was due to decreased PHA synthesis if the addition of labeled substrate was by the injection technique. Addition of labeled precursors to sediment by slurry or pore-water replacement induces greater disturbance artifacts than injection techniques.

  15. SEARCHING FOR COOLING SIGNATURES IN STRONG LENSING GALAXY CLUSTERS: EVIDENCE AGAINST BARYONS SHAPING THE MATTER DISTRIBUTION IN CLUSTER CORES

    SciTech Connect

    Blanchard, Peter K.; Bayliss, Matthew B.; McDonald, Michael; Dahle, Hakon; Gladders, Michael D.; Sharon, Keren; Mushotzky, Richard

    2013-07-20

    The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the baryonic condensation of the intracluster medium (ICM) due to cooling may drag dark matter to the cores and thus steepen the profile. In this work, we search for evidence of ongoing ICM cooling in the first large, well-defined sample of SL selected galaxy clusters in the range 0.1 < z < 0.6. Based on known correlations between the ICM cooling rate and both optical emission line luminosity and star formation, we measure, for a sample of 89 SL clusters, the fraction of clusters that have [O II]{lambda}{lambda}3727 emission in their brightest cluster galaxy (BCG). We find that the fraction of line-emitting BCGs is constant as a function of redshift for z > 0.2 and shows no statistically significant deviation from the total cluster population. Specific star formation rates, as traced by the strength of the 4000 A break, D{sub 4000}, are also consistent with the general cluster population. Finally, we use optical imaging of the SL clusters to measure the angular separation, R{sub arc}, between the arc and the center of mass of each lensing cluster in our sample and test for evidence of changing [O II] emission and D{sub 4000} as a function of R{sub arc}, a proxy observable for SL cross-sections. D{sub 4000} is constant with all values of R{sub arc}, and the [O II] emission fractions show no dependence on R{sub arc} for R{sub arc} > 10'' and only very marginal evidence of increased weak [O II] emission for systems with R{sub arc} < 10''. These results argue against the ability of baryonic cooling associated with cool core activity in the cores of galaxy clusters to strongly modify the underlying dark matter potential, leading to an increase in SL cross-sections.

  16. When the Milky Way turned off the lights: APOGEE provides evidence of star formation quenching in our Galaxy

    NASA Astrophysics Data System (ADS)

    Haywood, M.; Lehnert, M. D.; Di Matteo, P.; Snaith, O.; Schultheis, M.; Katz, D.; Gómez, A.

    2016-05-01

    Quenching, the cessation of star formation, is one of the most significant events in the life cycle of galaxies. While quenching is generally thought to be linked to their central regions, the mechanism responsible for it is not known and may not even be unique. We show here the first evidence that the Milky Way experienced a generalised quenching of its star formation at the end of its thick-disk formation ~9 Gyr ago. The fossil record imprinted on the elemental abundances of stars studied in the solar vicinity and as part of the APOGEE survey (APOGEE is part of the Sloan Digital Sky Survey III) reveals indeed that in less than ~2 Gyr (from 10 to 8 Gyr ago) the star formation rate in our Galaxy dropped by an order of magnitude. Because of the tight correlation that exists between age and α abundance, the general cessation of the star formation activity reflects in the dearth of stars along the inner-disk sequence in the [Fe/H]-[α/Fe] plane. Before this phase, which lasted about 1.5 Gyr, the Milky Way was actively forming stars. Afterwards, the star formation resumed at a much lower level to form the thin disk. These events observed in our Galaxy are very well matched by the latest observation of MW-type progenitors at high redshifts. In late-type galaxies, the quenching mechanism is believed to be related to a long and secular exhaustion of gas. Our results show that in the Milky Way, the shut-down occurred on a much shorter timescale, while the chemical continuity between the stellar populations formed before and after the quenching indicates that it is not the exhaustion of the gas that was responsible for the cessation of the star formation. While quenching is generally associated with spheroids in the literature, our results show that it also occurs in galaxies like the Milky Way, where the classical bulge is thought to be small or non-existent, possibly when they are undergoing a morphological transition from thick to thin disks. Given the demographics of

  17. X-ray AGN in the XMM-LSS galaxy clusters: no evidence of AGN suppression

    NASA Astrophysics Data System (ADS)

    Koulouridis, E.; Plionis, M.; Melnyk, O.; Elyiv, A.; Georgantopoulos, I.; Clerc, N.; Surdej, J.; Chiappetti, L.; Pierre, M.

    2014-07-01

    We present a study of the overdensity of X-ray-selected active galactic nuclei (AGN) in 33 galaxy clusters in the XMM-LSS field (The XMM-Newton Large Scale Structure Survey), up to redshift z = 1.05 and further divided into a lower (0.14 ≤ z ≤ 0.35) and a higher redshift (0.43 ≤ z ≤ 1.05) subsample. Previous studies have shown that the presence of X-ray-selected AGN in rich galaxy clusters is suppressed, since their number is significantly lower than what is expected from the high galaxy overdensities in the area. In the current study we have investigated the occurrence of X-ray-selected AGN in low (⟨ Lx,bol ⟩ = 2.7 × 1043 erg/s) and moderate (⟨ Lx,bol ⟩ = 2.4 × 1044 erg/s) X-ray luminosity galaxy clusters in an attempt to trace back the relation between high-density environments and nuclear activity. Owing to the wide contiguous XMM-LSS survey area, we were able to extend the study to the cluster outskirts. We therefore determined the projected overdensity of X-ray point-like sources around each cluster out to 6r500 radius, within δr500 = 1 annulus, with respect to the field expectations based on the X-ray source log N - log S of the XMM-LSS field. To provide robust statistical results we also conducted a consistent stacking analysis separately for the two z ranges. We investigated whether the observed X-ray overdensities are to be expected thanks to the obvious enhancement of galaxy numbers in the cluster environment by also estimating the corresponding optical galaxy overdensities, and we assessed the possible enhancement or suppression of AGN activity in clusters. We find a positive X-ray projected overdensity in both redshift ranges at the first radial bins, which however has the same amplitude as that of optical galaxies. Therefore, no suppression (or enhancement) of X-ray AGN activity with respect to the field is found, in sharp contrast to previous results based on rich galaxy clusters, implying that the mechanisms responsible for the

  18. Evidence of Nuclear Disks from the Radial Distribution of CCSNe in Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Herrero-Illana, Rubén; Pérez-Torres, Miguel Ángel; Alberdi, Antxon

    Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ˜ 100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.'1) radio observations. We derived scale-length values for the putative nuclear disks, which range from ˜ 20-30 pc for Arp 299-A and Arp 220, up to ˜ 140 pc for M82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. This study is detailed in Herrero-Illana, Perez-Torres, and Alberdi [11].

  19. An evidence for prompt electric field disturbance driven by changes in the solar wind density under northward IMF Bz condition

    NASA Astrophysics Data System (ADS)

    Rout, Diptiranjan; Chakrabarty, D.; Sekar, R.; Reeves, G. D.; Ruohoniemi, J. M.; Pant, Tarun K.; Veenadhari, B.; Shiokawa, K.

    2016-05-01

    Before the onset of a geomagnetic storm on 22 January 2012 (Ap = 24), an enhancement in solar wind number density from 10/cm3 to 22/cm3 during 0440-0510 UT under northward interplanetary magnetic field (IMF Bz) condition is shown to have enhanced the high-latitude ionospheric convection and also caused variations in the geomagnetic field globally. Conspicuous changes in ΔX are observed not only at longitudinally separated low-latitude stations over Indian (prenoon), South American (midnight), Japanese (afternoon), Pacific (afternoon) and African (morning) sectors but also at latitudinally separated stations located over high and middle latitudes. The latitudinal variation of the amplitude of the ΔX during 0440-0510 UT is shown to be consistent with the characteristics of prompt penetration electric field disturbances. Most importantly, the density pulse event caused enhancements in the equatorial electrojet strength and the peak height of the F layer (hmF2) over the Indian dip equatorial sector. Further, the concomitant enhancements in electrojet current and F layer movement over the dip equator observed during this space weather event suggest a common driver of prompt electric field disturbance at this time. Such simultaneous variations are found to be absent during magnetically quiet days. In absence of significant change in solar wind velocity and magnetospheric substorm activity, these observations point toward perceptible prompt electric field disturbance over the dip equator driven by the overcompression of the magnetosphere by solar wind density enhancement.

  20. Radio emission at the centre of the galaxy cluster Abell 3560: evidence for core sloshing?

    NASA Astrophysics Data System (ADS)

    Venturi, T.; Rossetti, M.; Bardelli, S.; Giacintucci, S.; Dallacasa, D.; Cornacchia, M.; Kantharia, N. G.

    2013-10-01

    Context. We study the interplay between the radio emission associated with the dominant galaxy in clusters and the properties of the surrounding intracluster medium on the basis of its X-ray emission. Aims: Previous radio observations of the galaxy cluster A 3560, located in the Shapley Concentration core, revealed complex radio emission associated with the brightest cluster member. To understand the origin of this radio emission we performed a detailed multiwavelength study with high-quality proprietary data in the radio and X-ray bands and by means of optical data available in the literature. Methods: We observed the cluster with the Giant Metrewave Radio Telescope, the Very Large Array, and the Australia Telescope Compact array at 240 and 610 MHz, 1.28, 1.4, 2.3, 4.8, and 8.4 GHz, and performed a detailed morphological and spectral study of the radio emission associated with the brightest cluster galaxy (BCG). Furthermore, we observed the cluster with the XMM-Newton and Chandra observatories to derive the properties of the intracluster gas. Finally, we made use of literature data to obtain the bidimensional distribution of the galaxies in the cluster. Results: The radio emission, associated with the north-eastern nucleus of the dumb-bell BCG, is the result of two components: an active radio galaxy, with jets and lobes, plus aged diffuse emission, which is not refurbished with new electrons at present. Our Chandra data show that the radio active nucleus of the BCG has extended X-ray emission, which we classify as a low-luminosity corona. A residual image of the XMM-Newton brightness distribution shows a spiral-like feature, which we interpret as the signature of gas sloshing. A sub-group is clearly visible in the surface brightness residual map, and this is also supported by the XMM-Newton temperature analysis. The optical bidimensional analysis shows substructure in A 3560. A galaxy clump was detected at the location of the X-ray sub-group, and another group is

  1. Evidence for a ~300 Megaparsec Scale Under-density in the Local Galaxy Distribution

    NASA Astrophysics Data System (ADS)

    Keenan, R. C.; Barger, A. J.; Cowie, L. L.

    2013-09-01

    Galaxy counts and recent measurements of the luminosity density in the near-infrared have indicated the possibility that the local universe may be under-dense on scales of several hundred megaparsecs. The presence of a large-scale under-density in the local universe could introduce significant biases into the interpretation of cosmological observables, and, in particular, into the inferred effects of dark energy on the expansion rate. Here we measure the K-band luminosity density as a function of redshift to test for such a local under-density. For our primary sample in this study, we select galaxies from the UKIDSS Large Area Survey and use spectroscopy from the Sloan Digital Sky Survey (SDSS), the Two-degree Field Galaxy Redshift Survey, the Galaxy And Mass Assembly Survey (GAMA), and other redshift surveys to generate a K-selected catalog of ~35, 000 galaxies that is ~95% spectroscopically complete at K AB < 16.3 (K AB < 17 in the GAMA fields). To complement this sample at low redshifts, we also analyze a K-selected sample from the 2M++ catalog, which combines Two Micron All Sky Survey (2MASS) photometry with redshifts from the 2MASS redshift survey, the Six-degree Field Galaxy Redshift Survey, and the SDSS. The combination of these samples allows for a detailed measurement of the K-band luminosity density as a function of distance over the redshift range 0.01 < z < 0.2 (radial distances D ~ 50-800 h_{70}^{-1} Mpc). We find that the overall shape of the z = 0 rest-frame K-band luminosity function (M*-5log (h 70) = -22.15 ± 0.04 and α = -1.02 ± 0.03) appears to be relatively constant as a function of environment and distance from us. We find a local (z < 0.07, D < 300 h_{70}^{-1} Mpc) luminosity density that is in good agreement with previous studies. Beyond z ~ 0.07, we detect a rising luminosity density that reaches a value of roughly ~1.5 times higher than that measured locally at z > 0.1. This suggests that the stellar mass density as a function of

  2. EVIDENCE FOR A ∼300 MEGAPARSEC SCALE UNDER-DENSITY IN THE LOCAL GALAXY DISTRIBUTION

    SciTech Connect

    Keenan, R. C.; Barger, A. J.; Cowie, L. L.

    2013-09-20

    Galaxy counts and recent measurements of the luminosity density in the near-infrared have indicated the possibility that the local universe may be under-dense on scales of several hundred megaparsecs. The presence of a large-scale under-density in the local universe could introduce significant biases into the interpretation of cosmological observables, and, in particular, into the inferred effects of dark energy on the expansion rate. Here we measure the K-band luminosity density as a function of redshift to test for such a local under-density. For our primary sample in this study, we select galaxies from the UKIDSS Large Area Survey and use spectroscopy from the Sloan Digital Sky Survey (SDSS), the Two-degree Field Galaxy Redshift Survey, the Galaxy And Mass Assembly Survey (GAMA), and other redshift surveys to generate a K-selected catalog of ∼35, 000 galaxies that is ∼95% spectroscopically complete at K{sub AB} < 16.3 (K{sub AB} < 17 in the GAMA fields). To complement this sample at low redshifts, we also analyze a K-selected sample from the 2M++ catalog, which combines Two Micron All Sky Survey (2MASS) photometry with redshifts from the 2MASS redshift survey, the Six-degree Field Galaxy Redshift Survey, and the SDSS. The combination of these samples allows for a detailed measurement of the K-band luminosity density as a function of distance over the redshift range 0.01 < z < 0.2 (radial distances D ∼ 50-800 h{sub 70}{sup -1} Mpc). We find that the overall shape of the z = 0 rest-frame K-band luminosity function (M*-5log (h{sub 70}) = –22.15 ± 0.04 and α = –1.02 ± 0.03) appears to be relatively constant as a function of environment and distance from us. We find a local (z < 0.07, D < 300 h{sub 70}{sup -1} Mpc) luminosity density that is in good agreement with previous studies. Beyond z ∼ 0.07, we detect a rising luminosity density that reaches a value of roughly ∼1.5 times higher than that measured locally at z > 0.1. This suggests that the

  3. EVIDENCE FOR AN INTERACTION IN THE NEAREST STARBURSTING DWARF IRREGULAR GALAXY IC 10

    SciTech Connect

    Nidever, David L.; Slater, Colin T.; Bell, Eric F.; Ashley, Trisha; Simpson, Caroline E.; Ott, Jürgen; Johnson, Megan; Stanimirović, Snežana; Putman, Mary; Majewski, Steven R.; Jütte, Eva; Oosterloo, Tom A.; Burton, W. Butler

    2013-12-20

    Using deep 21 cm H I data from the Green Bank Telescope we have detected an ≳18.3 kpc long gaseous extension associated with the starbursting dwarf galaxy IC 10. The newly found feature stretches 1.°3 to the northwest and has a large radial velocity gradient reaching to ∼65 km s{sup –1} lower than the IC 10 systemic velocity. A region of higher column density at the end of the extension that possesses a coherent velocity gradient (∼10 km s{sup –1} across ∼26') transverse to the extension suggests rotation and may be a satellite galaxy of IC 10. The H I mass of IC 10 is 9.5 × 10{sup 7} (d/805 kpc){sup 2} M {sub ☉} and the mass of the new extension is 7.1 × 10{sup 5} (d/805 kpc){sup 2} M {sub ☉}. An IC 10-M31 orbit using known radial velocity and proper motion values for IC 10 show that the H I extension is inconsistent with the trailing portion of the orbit so that an M31-tidal or ram pressure origin seems unlikely. We argue that the most plausible explanation for the new feature is that it is the result of a recent interaction (and possible late merger) with another dwarf galaxy. This interaction could not only have triggered the origin of the recent starburst in IC 10, but could also explain the existence of previously found counter-rotating H I gas in the periphery of the IC 10 which was interpreted as originating from primordial gas infall.

  4. Evidence of a Supermassive Black Hole in the Galaxy NGC 1023 From The Nuclear Stellar Dynamics

    NASA Technical Reports Server (NTRS)

    Bower, G. A.; Green, R. F.; Bender, R.; Gebhardt, K.; Lauer, T. R.; Magorrian, J.; Richstone, D. O.; Danks, A.; Gull, T.; Hutchings, J.

    2000-01-01

    We analyze the nuclear stellar dynamics of the SBO galaxy NGC 1023, utilizing observational data both from the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope and from the ground. The stellar kinematics measured from these long-slit spectra show rapid rotation (V equals approx. 70 km/s at a distance of O.1 deg = 4.9 pc from the nucleus) and increasing velocity dispersion toward the nucleus (where sigma = 295 +/- 30 km/s). We model the observed stellar kinematics assuming an axisymmetric mass distribution with both two and three integrals of motion. Both modeling techniques point to the presence of a central dark compact mass (which presumably is a supermassive black hole) with confidence > 99%. The isotropic two-integral models yield a best-fitting black hole mass of (6.0 +/- 0.4) x 10(exp 7) solar masses and mass-to-light ratio (M/L(sub v)) of 5.38 +/- 0.08, and the goodness-of-fit (CHI(exp 2)) is insensitive to reasonable values for the galaxy's inclination. The three-integral models, which non-parametrically fit the observed line-of-sight velocity distribution as a function of position in the galaxy, suggest a black hole mass of (3.9 +/- 0.4) x 10(exp 7) solar masses and M/L(sub v) of 5.56 +/- 0.02 (internal errors), and the edge-on models are vastly superior fits over models at other inclinations. The internal dynamics in NGC 1023 as suggested by our best-fit three-integral model shows that the velocity distribution function at the nucleus is tangentially anisotropic, suggesting the presence of a nuclear stellar disk. The nuclear line of sight velocity distribution has enhanced wings at velocities >= 600 km/s from systemic, suggesting that perhaps we have detected a group of stars very close to the central dark mass.

  5. INTEGRAL-FIELD STELLAR AND IONIZED GAS KINEMATICS OF PECULIAR VIRGO CLUSTER SPIRAL GALAXIES

    SciTech Connect

    Cortés, Juan R.; Hardy, Eduardo; Kenney, Jeffrey D. P. E-mail: ehardy@nrao.cl

    2015-01-01

    We present the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies observed with the DensePak Integral Field Unit at the WIYN 3.5 m telescope in order to look for kinematic evidence that these galaxies have experienced gravitational interactions or gas stripping. Two-dimensional maps of the stellar velocity V, stellar velocity dispersion σ, and the ionized gas velocity (Hβ and/or [O III]) are presented for the galaxies in the sample. The stellar rotation curves and velocity dispersion profiles are determined for 13 galaxies, and the ionized gas rotation curves are determined for 6 galaxies. Misalignments between the optical and kinematical major axes are found in several galaxies. While in some cases this is due to a bar, in other cases it seems to be associated with gravitational interaction or ongoing ram pressure stripping. Non-circular gas motions are found in nine galaxies, with various causes including bars, nuclear outflows, or gravitational disturbances. Several galaxies have signatures of kinematically distinct stellar components, which are likely signatures of accretion or mergers. For all of our galaxies, we compute the angular momentum parameter λ {sub R}. An evaluation of the galaxies in the λ {sub R} ellipticity plane shows that all but two of the galaxies have significant support from random stellar motions, and have likely experienced gravitational interactions. This includes some galaxies with very small bulges and truncated/compact Hα morphologies, indicating that such galaxies cannot be fully explained by simple ram pressure stripping, but must have had significant gravitational encounters. Most of the sample galaxies show evidence for ICM-ISM stripping as well as gravitational interactions, indicating that the evolution of a significant fraction of cluster galaxies is likely strongly impacted by both effects.

  6. Evidence for Black Hole Growth in Local Analogs to Lyman Break Galaxies

    NASA Technical Reports Server (NTRS)

    Jia, Jianjun; Ptak, Andrew; Heckman, Timothy M.; Overzier, Roderik A.; Hornschemeier, Ann; LaMassa, Stephanie M.

    2011-01-01

    We have used XMM-Newton to observe six Lyman break analogs (LBAs): members of the rare population of local galaxies that have properties that are very similar to distant Lyman break galaxies. Our six targets were specifically selected because they have optical emission-line properties that are intermediate between starbursts and Type 2 (obscured) active galactic nuclei (AGNs). Our new X-ray data provide an important diagnostic of the presence of an AGN. We find X-ray luminosities of order 10(sup 42) erg per second and ratios of X-ray to far-IR lummositles that are higher than values in pure starburst galaxies by factors ranging from approximately 3 to 30. This strongly suggests the presence of an AGN in at least some of the galaxies. The ratios of the luminosities of the hard (2-10 keV) X-ray to [O III] emission line are low by about an order of magnitude compared with Type 1 AGN, but are consistent with the broad range seen in Type 2 AGN. Either the AGN hard X-rays are significantly obscured or the [O III] emission is dominated by the starburst. We searched for an iron emission line at approximately 6.4 ke V, which is a key feature of obscured AGNs, but only detected emission at the approximately 2sigma level. Finally, we find that the ratios of the mid-infrared (24 micrometer) continuum to [O III]lambda 5007 luminosities in these LBAs are higher than the values for Type 2 AGN by an average of 0.8 dex. Combining all these clues, we conclude that an AGN is likely to be present, but that the bolometric luminosity is produced primarily by an intense starburst. If these black holes are radiating at the Eddington limit, their masses would lie in the range of 10(sup 5) - 10(sup 6) solar mass. These objects may offer ideal local laboratories to investigate the processes by which black holes grew in the early universe.

  7. Local dark energy: HST evidence from the vicinity of the M81/M82 galaxy group

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.; Karachentsev, I. D.; Kashibadze, O. G.; Makarov, D. I.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.

    2007-10-01

    The Hubble Space Telescope observations of the nearby galaxy group M81/M82 and its vicinity indicate that the dynamics of the expansion outflow around the group is dominated by the antigravity of the dark energy background. The local density of dark energy in the area is estimated to be near the global dark energy density or perhaps exactly equal to it. This conclusion agrees well with our previous results for the Local Group vicinity and the vicinity of the Cen A/M83 group.

  8. Evidence of coronal flaring in narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Gallo, L. C.

    High-energy (E>2 keV) continuum flaring is detected in two narrow-line Seyfert 1 galaxies (I Zw 1 and NAB 0205+024), consistent with occurring in a hot corona distinct from the accretion disc. The flare in I Zw 1 is accompanied by an increase in the amount of gravitationally redshifted reflected emission coming from the accretion disc. This indicates that the high-energy continuum component is compact and located close to the black hole, and could possibly be the base of an aborted jet.

  9. THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT

    SciTech Connect

    Geha, Marla; Brown, Thomas M.; Tumlinson, Jason; Kalirai, Jason S.; Avila, Roberto J.; Ferguson, Henry C.; Simon, Joshua D.; Kirby, Evan N.; VandenBerg, Don A.; Munoz, Ricardo R.; Guhathakurta, Puragra E-mail: tbrown@stsci.edu

    2013-07-01

    We present constraints on the stellar initial mass function (IMF) in two ultra-faint dwarf (UFD) galaxies, Hercules and Leo IV, based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. The Hercules and Leo IV galaxies are extremely low luminosity (M{sub V} = -6.2, -5.5), metal-poor (([Fe/H]) = -2.4, -2.5) systems that have old stellar populations (>11 Gyr). Because they have long relaxation times, we can directly measure the low-mass stellar IMF by counting stars below the main-sequence turnoff without correcting for dynamical evolution. Over the stellar mass range probed by our data, 0.52-0.77 M{sub Sun }, the IMF is best fit by a power-law slope of {alpha}= 1.2{sub -0.5}{sup +0.4} for Hercules and {alpha} = 1.3 {+-} 0.8 for Leo IV. For Hercules, the IMF slope is more shallow than a Salpeter ({alpha} = 2.35) IMF at the 5.8{sigma} level, and a Kroupa ({alpha} = 2.3 above 0.5 M{sub Sun }) IMF slope at 5.4{sigma} level. We simultaneously fit for the binary fraction, f{sub binary}, finding f{sub binary}= 0.47{sup +0.16}{sub -0.14} for Hercules, and 0.47{sup +0.37}{sub -0.17} for Leo IV. The UFD binary fractions are consistent with that inferred for Milky Way stars in the same mass range, despite very different metallicities. In contrast, the IMF slopes in the UFDs are shallower than other galactic environments. In the mass range 0.5-0.8 M{sub Sun }, we see a trend across the handful of galaxies with directly measured IMFs such that the power-law slopes become shallower (more bottom-light) with decreasing galactic velocity dispersion and metallicity. This trend is qualitatively consistent with results in elliptical galaxies inferred via indirect methods and is direct evidence for IMF variations with galactic environment.

  10. Strong Evidence for the Density-wave Theory of Spiral Structure in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Pour-Imani, Hamed; Kennefick, Daniel; Kennefick, Julia; Davis, Benjamin L.; Shields, Douglas W.; Shameer Abdeen, Mohamed

    2016-08-01

    The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxy’s image. The reason is that stars are born in the density wave but move out of it as they age. They move ahead of the density wave inside the co-rotation radius, and fall behind outside of it, resulting in a tighter pitch angle at wavelengths that image stars (optical and near-infrared) than those that are associated with star formation (far-infrared and ultraviolet). In this study we combined large sample size with wide range of wavelengths, from the ultraviolet to the infrared to investigate this issue. For each galaxy we used an optical wavelength image (B-band: 445 nm) and images from the Spitzer Space Telescope at two infrared wavelengths (infrared: 3.6 and 8.0 μm) and we measured the pitch angle with the 2DFFT and Spirality codes. We find that the B-band and 3.6 μm images have smaller pitch angles than the infrared 8.0 μm image in all cases, in agreement with the prediction of density-wave theory. We also used images in the ultraviolet from Galaxy Evolution Explorer, whose pitch angles agreed with the measurements made at 8 μm.

  11. The IMACS Cluster Building Survey. V. Further Evidence for Starburst Recycling from Quantitative Galaxy Morphologies

    NASA Astrophysics Data System (ADS)

    Abramson, Louis E.; Dressler, Alan; Gladders, Michael D.; Oemler, Augustus, Jr.; Poggianti, Bianca M.; Monson, Andrew; Persson, Eric; Vulcani, Benedetta

    2013-11-01

    Using J- and K s-band imaging obtained as part of the IMACS Cluster Building Survey (ICBS), we measure Sérsic indices for 2160 field and cluster galaxies at 0.31 < z < 0.54. Using both mass- and magnitude-limited samples, we compare the distributions for spectroscopically determined passive, continuously star-forming, starburst, and post-starburst systems and show that previously established spatial and statistical connections between these types extend to their gross morphologies. Outside of cluster cores, we find close structural ties between starburst and continuously star-forming, as well as post-starburst and passive types, but not between starbursts and post-starbursts. These results independently support two conclusions presented in Paper II of this series: (1) most starbursts are the product of a non-disruptive triggering mechanism that is insensitive to global environment, such as minor mergers; (2) starbursts and post-starbursts generally represent transient phases in the lives of "normal" star-forming and quiescent galaxies, respectively, originating from and returning to these systems in closed "recycling" loops. In this picture, spectroscopically identified post-starbursts constitute a minority of all recently terminated starbursts, largely ruling out the typical starburst as a quenching event in all but the densest environments. Data were obtained using the 6.5 m Magellan Telescopes at Las Campanas Observatory, Chile.

  12. THE IMACS CLUSTER BUILDING SURVEY. V. FURTHER EVIDENCE FOR STARBURST RECYCLING FROM QUANTITATIVE GALAXY MORPHOLOGIES

    SciTech Connect

    Abramson, Louis E.; Gladders, Michael D.; Dressler, Alan; Oemler, Augustus Jr.; Monson, Andrew; Persson, Eric; Poggianti, Bianca M.; Vulcani, Benedetta

    2013-11-10

    Using J- and K{sub s}-band imaging obtained as part of the IMACS Cluster Building Survey (ICBS), we measure Sérsic indices for 2160 field and cluster galaxies at 0.31 < z < 0.54. Using both mass- and magnitude-limited samples, we compare the distributions for spectroscopically determined passive, continuously star-forming, starburst, and post-starburst systems and show that previously established spatial and statistical connections between these types extend to their gross morphologies. Outside of cluster cores, we find close structural ties between starburst and continuously star-forming, as well as post-starburst and passive types, but not between starbursts and post-starbursts. These results independently support two conclusions presented in Paper II of this series: (1) most starbursts are the product of a non-disruptive triggering mechanism that is insensitive to global environment, such as minor mergers; (2) starbursts and post-starbursts generally represent transient phases in the lives of 'normal' star-forming and quiescent galaxies, respectively, originating from and returning to these systems in closed 'recycling' loops. In this picture, spectroscopically identified post-starbursts constitute a minority of all recently terminated starbursts, largely ruling out the typical starburst as a quenching event in all but the densest environments.

  13. Evidence That Hydra I is a Tidally Disrupting Milky Way Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Hargis, Jonathan R.; Kimmig, Brian; Willman, Beth; Caldwell, Nelson; Walker, Matthew G.; Strader, Jay; Sand, David J.; Grillmair, Carl J.; Yoon, Joo Heon

    2016-02-01

    The Eastern Banded Structure (EBS) and Hydra I halo overdensities are very nearby (d ∼ 10 kpc) objects discovered in Sloan Digital Sky Survey (SDSS) data. Previous studies of the region have shown that EBS and Hydra I are spatially coincident, cold structures at the same distance, suggesting that Hydra I may be the EBS's progenitor. We combine new wide-field Dark Energy Camera (DECam) imaging and MMT/Hectochelle spectroscopic observations of Hydra I with SDSS archival spectroscopic observations to quantify Hydra I's present-day chemodynamical properties, and to infer whether it originated as a star cluster or dwarf galaxy. While previous work using shallow SDSS imaging assumed a standard old, metal-poor stellar population, our deeper DECam imaging reveals that Hydra I has a thin, well-defined main sequence turnoff of intermediate age (∼5–6 Gyr) and metallicity ([Fe/H] = ‑0.9 dex). We measure statistically significant spreads in both the iron and alpha-element abundances of {σ }[{Fe/{{H}}]}=0.13+/- 0.02 dex and {σ }[α /{{Fe}]}=0.09+/- 0.03 dex, respectively, and place upper limits on both the rotation and its proper motion. Hydra I's intermediate age and [Fe/H]—as well as its low [α/Fe], apparent [Fe/H] spread, and present-day low luminosity—suggest that its progenitor was a dwarf galaxy, which has subsequently lost more than 99.99% of its stellar mass.

  14. Evidence for photometric contamination in key observations of Cepheids in the benchmark galaxy IC 1613

    NASA Astrophysics Data System (ADS)

    Majaess, D.; Turner, D. G.; Gieren, W.; Ngeow, C.

    2014-12-01

    This study helps increase awareness of the pernicious effects of photometric contamination (crowding/blending), since it can propagate an undesirable systematic offset into the cosmic distance scale. The latest Galactic Cepheid Wesenheit (VIc) and Spitzer calibrations were employed to establish distances for classical Cepheids in IC 1613 and NGC 6822, thus enabling the impact of photometric contamination to be assessed in concert with metallicity. Distances (WVIc, [3.6]) for Cepheids in IC 1613 exhibit a galactocentric dependence, whereby Cepheids near the core appear (spuriously) too bright (rg< 2'). That effect is attributed to photometric contamination from neighboring (unresolved) stars, since the stellar density and surface brightness may increase with decreasing galactocentric distance. The impact is relatively indiscernible for a comparison sample of Cepheids occupying NGC 6822, a result that is partly attributable to that sample being nearer than the metal-poor galaxy IC 1613. WVIc and [3.6] distances for relatively uncontaminated Cepheids in each galaxy are comparable, thus confirming that period-magnitude relations (Leavitt Law) in those bands are relatively insensitive to metallicity (Δ [ Fe/H ] ≃ 1).

  15. SPECTROPOLARIMETRIC EVIDENCE FOR RADIATIVELY INEFFICIENT ACCRETION IN AN OPTICALLY DULL ACTIVE GALAXY

    SciTech Connect

    Trump, Jonathan R.; Murayama, Takashi; Taniguchi, Yoshi; Impey, Christopher D.; Stocke, John T.; Civano, Francesca; Elvis, Martin; Kelly, Brandon C.; Jahnke, Knud; Koekemoer, Anton M.

    2011-05-01

    We present Subaru/FOCAS spectropolarimetry of two active galaxies in the Cosmic Evolution Survey. These objects were selected to be optically dull, with the bright X-ray emission of an active galactic nucleus (AGN) but missing optical emission lines in our previous spectroscopy. Our new observations show that one target has very weak emission lines consistent with an optically dull AGN, while the other object has strong emission lines typical of a host-diluted Type 2 Seyfert galaxy. In neither source do we observe polarized emission lines, with 3{sigma} upper limits of P{sub BLR} {approx}< 2%. This means that the missing broad emission lines (and weaker narrow emission lines) are not due to simple anisotropic obscuration, e.g., by the canonical AGN torus. The weak-lined optically dull AGN exhibits a blue polarized continuum with P = 0.78% {+-} 0.07% at 4400 A < {lambda}{sub rest} < 7200 A (P = 1.37% {+-} 0.16% at 4400 A < {lambda}{sub rest} < 5050 A). The wavelength dependence of this polarized flux is similar to that of an unobscured AGN continuum and represents the intrinsic AGN emission, either as synchrotron emission or the outer part of an accretion disk reflected by a clumpy dust scatterer. Because this intrinsic AGN emission lacks emission lines, this source is likely to have a radiatively inefficient accretion flow.

  16. EVIDENCE FOR THREE ACCRETING BLACK HOLES IN A GALAXY AT z {approx} 1.35: A SNAPSHOT OF RECENTLY FORMED BLACK HOLE SEEDS?

    SciTech Connect

    Schawinski, Kevin; Urry, Meg; Treister, Ezequiel; Simmons, Brooke; Natarajan, Priyamvada; Glikman, Eilat

    2011-12-20

    One of the key open questions in cosmology today pertains to understanding when, where, and how supermassive black holes form. While it is clear that mergers likely play a significant role in the growth cycles of black holes, the issue of how supermassive black holes form, and how galaxies grow around them, still needs to be addressed. Here, we present Hubble Space Telescope Wide Field Camera 3/IR grism observations of a clumpy galaxy at z = 1.35, with evidence for 10{sup 6}-10{sup 7} M{sub Sun} rapidly growing black holes in separate sub-components of the host galaxy. These black holes could have been brought into close proximity as a consequence of a rare multiple galaxy merger or they could have formed in situ. Such holes would eventually merge into a central black hole as the stellar clumps/components presumably coalesce to form a galaxy bulge. If we are witnessing the in situ formation of multiple black holes, their properties can inform seed formation models and raise the possibility that massive black holes can continue to emerge in star-forming galaxies as late as z = 1.35 (4.8 Gyr after the big bang).

  17. CO(J = 1→0) in z > 2 Quasar Host Galaxies: No Evidence for Extended Molecular Gas Reservoirs

    NASA Astrophysics Data System (ADS)

    Riechers, Dominik A.; Carilli, Christopher L.; Maddalena, Ronald J.; Hodge, Jacqueline; Harris, Andrew I.; Baker, Andrew J.; Walter, Fabian; Wagg, Jeff; Vanden Bout, Paul A.; Weiß, Axel; Sharon, Chelsea E.

    2011-09-01

    We report the detection of CO(J = 1→0) emission in the strongly lensed high-redshift quasars IRAS F10214+4724 (z = 2.286), the Cloverleaf (z = 2.558), RX J0911+0551 (z = 2.796), SMM J04135+10277 (z = 2.846), and MG 0751+2716 (z = 3.200), using the Expanded Very Large Array and the Green Bank Telescope. We report lensing-corrected CO(J = 1→0) line luminosities of L'CO = (0.34-18.4) × 1010 K km s-1 pc2 and total molecular gas masses of M(H2) = (0.27-14.7) × 1010 M sun for the sources in our sample. Based on CO line ratios relative to previously reported observations in J >= 3 rotational transitions and line excitation modeling, we find that the CO(J = 1→0) line strengths in our targets are consistent with single, highly excited gas components with constant brightness temperature up to mid-J levels. We thus do not find any evidence for luminous-extended, low-excitation, low surface brightness molecular gas components. These properties are comparable to those found in z > 4 quasars with existing CO(J = 1→0) observations. These findings stand in contrast to recent CO(J = 1→0) observations of z ~= 2-4 submillimeter galaxies (SMGs), which have lower CO excitation and show evidence for multiple excitation components, including some low-excitation gas. These findings are consistent with the picture that gas-rich quasars and SMGs represent different stages in the early evolution of massive galaxies.

  18. CO(J = 1{yields}0) IN z > 2 QUASAR HOST GALAXIES: NO EVIDENCE FOR EXTENDED MOLECULAR GAS RESERVOIRS

    SciTech Connect

    Riechers, Dominik A.; Carilli, Christopher L.; Maddalena, Ronald J.; Hodge, Jacqueline; Walter, Fabian; Harris, Andrew I.; Baker, Andrew J.; Sharon, Chelsea E.; Wagg, Jeff; Vanden Bout, Paul A.; Weiss, Axel

    2011-09-20

    We report the detection of CO(J = 1{yields}0) emission in the strongly lensed high-redshift quasars IRAS F10214+4724 (z = 2.286), the Cloverleaf (z = 2.558), RX J0911+0551 (z = 2.796), SMM J04135+10277 (z = 2.846), and MG 0751+2716 (z = 3.200), using the Expanded Very Large Array and the Green Bank Telescope. We report lensing-corrected CO(J = 1{yields}0) line luminosities of L'{sub CO} = (0.34-18.4) x 10{sup 10} K km s{sup -1} pc{sup 2} and total molecular gas masses of M(H{sub 2}) = (0.27-14.7) x 10{sup 10} M{sub sun} for the sources in our sample. Based on CO line ratios relative to previously reported observations in J {>=} 3 rotational transitions and line excitation modeling, we find that the CO(J = 1{yields}0) line strengths in our targets are consistent with single, highly excited gas components with constant brightness temperature up to mid-J levels. We thus do not find any evidence for luminous-extended, low-excitation, low surface brightness molecular gas components. These properties are comparable to those found in z > 4 quasars with existing CO(J = 1{yields}0) observations. These findings stand in contrast to recent CO(J = 1{yields}0) observations of z {approx_equal} 2-4 submillimeter galaxies (SMGs), which have lower CO excitation and show evidence for multiple excitation components, including some low-excitation gas. These findings are consistent with the picture that gas-rich quasars and SMGs represent different stages in the early evolution of massive galaxies.

  19. Evidence for a uniformly small isotope effect of nitrogen leaching loss: results from disturbed ecosystems in seasonally dry climates.

    PubMed

    Mnich, Meagan E; Houlton, Benjamin Z

    2016-06-01

    Nitrogen (N) losses constrain rates of plant carbon dioxide (CO2) uptake and storage in many ecosystems globally. N isotope models have been used to infer that ~30 % of terrestrial N losses occur via microbial denitrification; however, this approach assumes a small isotope effect associated with N leaching losses. Past work across tropical/sub-tropical forest sites has confirmed this expectation; however, the stable N isotope ratio (δ(15)N) of ecosystem leaching has yet to be systematically evaluated in seasonally dry climates or across major ecosystem disturbances. We here present new measurements of the δ(15)N of total dissolved N (TDN) in small streams, bulk deposition, and soil pools across eight watershed sites in California, including grassland, chaparral, and coastal redwood forest ecosystems, with and without fire, grazing, and forest harvesting. Regardless of the dominant vegetation type or disturbance regime, average δ(15)N of TDN in stream water differed only slightly (<~1 ‰) from that of bulk soil δ(15)N, revealing a uniformly small isotope effect associated with N leaching losses even under non-steady state conditions. Rather, lower input δ(15)N compared to TDN δ(15)N in streams pointed to fractionations via gaseous loss pathways as the dominant mechanism behind soil δ(15)N enrichment. We conclude that N leaching does not impart a major isotope effect across a broad range of ecosystems and conditions examined, thereby advancing the N gas-loss hypothesis as the principal explanation for variation in bulk soil δ(15)N. PMID:26343040

  20. Evidence in support of the role of disturbance vegetation for women’s health and childcare in Western Africa

    PubMed Central

    2014-01-01

    Background In savannah-dominated Bénin, West Africa, and forest-dominated Gabon, Central Africa, plants are a major source of healthcare for women and children. Due to this high demand and the reliance on wild populations as sources for medicinal plants, overharvesting of African medicinal plants is a common concern. Few studies in Western Africa, however, have assessed variations in harvest patterns across different ecological zones and within local communities. Methods We investigated which vegetation types women accessed to harvest medicinal plants by conducting 163 questionnaires with market vendors and women from urban and rural communities. We made botanical vouchers of cited species and collected information on their vegetation type and cultivation status. Results Secondary vegetation was a crucial asset; over 80% of the 335 Beninese and 272 Gabonese plant species came from disturbance vegetation and home gardens. In Bénin, access to trade channels allowed female market vendors to use more vulnerable species than rural and urban women who harvested for personal use. In Gabon, no relationship was found between vulnerable plant use and informant type. Conclusions This study highlights the underemphasized point that secondary vegetation is an asset for women and children’s health in both savanna-dominated and forest-dominated landscapes. The use of disturbance vegetation demonstrates women’s resilience in meeting healthcare needs in the limited amount of space that is available to them. Species of conservation concern included forest species and savanna trees sold at markets in Bénin, especially Xylopia aethiopica, Khaya senegalensis, and Monodora myristica, and the timber trees with medicinal values in Gabon, such as Baillonella toxisperma. PMID:24885805

  1. Evidence for a uniformly small isotope effect of nitrogen leaching loss: results from disturbed ecosystems in seasonally dry climates.

    PubMed

    Mnich, Meagan E; Houlton, Benjamin Z

    2016-06-01

    Nitrogen (N) losses constrain rates of plant carbon dioxide (CO2) uptake and storage in many ecosystems globally. N isotope models have been used to infer that ~30 % of terrestrial N losses occur via microbial denitrification; however, this approach assumes a small isotope effect associated with N leaching losses. Past work across tropical/sub-tropical forest sites has confirmed this expectation; however, the stable N isotope ratio (δ(15)N) of ecosystem leaching has yet to be systematically evaluated in seasonally dry climates or across major ecosystem disturbances. We here present new measurements of the δ(15)N of total dissolved N (TDN) in small streams, bulk deposition, and soil pools across eight watershed sites in California, including grassland, chaparral, and coastal redwood forest ecosystems, with and without fire, grazing, and forest harvesting. Regardless of the dominant vegetation type or disturbance regime, average δ(15)N of TDN in stream water differed only slightly (<~1 ‰) from that of bulk soil δ(15)N, revealing a uniformly small isotope effect associated with N leaching losses even under non-steady state conditions. Rather, lower input δ(15)N compared to TDN δ(15)N in streams pointed to fractionations via gaseous loss pathways as the dominant mechanism behind soil δ(15)N enrichment. We conclude that N leaching does not impart a major isotope effect across a broad range of ecosystems and conditions examined, thereby advancing the N gas-loss hypothesis as the principal explanation for variation in bulk soil δ(15)N.

  2. Extreme Gas Kinematics in the z=2.2 Powerful Radio Galaxy MRC1138-262: Evidence for Efficient AGN Feedback in the Early Universe?

    SciTech Connect

    Nesvadba, N H; Lehnert, M D; Eisenhauer, F; Gilbert, A M; Tecza, M; Abuter, R

    2007-06-26

    To explain the properties of the most massive low-redshift galaxies and the shape of their mass function, recent models of galaxy evolution include strong AGN feedback to complement starburst-driven feedback in massive galaxies. Using the near-infrared integral-field spectrograph SPIFFI on the VLT, we searched for direct evidence for such a feedback in the optical emission line gas around the z = 2.16 powerful radio galaxy MRC1138-262, likely a massive galaxy in formation. The kpc-scale kinematics, with FWHMs and relative velocities {approx}< 2400 km s{sup -1} and nearly spherical spatial distribution, do not resemble large-scale gravitational motion or starburst-driven winds. Order-of-magnitude timescale and energy arguments favor the AGN as the only plausible candidate to accelerate the gas, with a total energy injection of {approx} few x 10{sup 60} ergs or more, necessary to power the outflow, and relatively efficient coupling between radio jet and ISM. Observed outflow properties are in gross agreement with the models, and suggest that AGN winds might have a similar, or perhaps larger, cosmological significance than starburst-driven winds, if MRC1138-262 is indeed archetypal. Moreover, the outflow has the potential to remove significant gas fractions ({approx}< 50%) from a > L* galaxy within a few 10 to 100 Myrs, fast enough to preserve the observed [{alpha}/Fe] overabundance in massive galaxies at low redshift. Using simple arguments, it appears that feedback like that observed in MRC1138-262 may have sufficient energy to inhibit material from infalling into the dark matter halo and thus regulate galaxy growth as required in some recent models of hierarchical structure formation.

  3. Simulating the toothbrush: evidence for a triple merger of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Brüggen, M.; van Weeren, R. J.; Röttgering, H. J. A.

    2012-09-01

    The newly discovered galaxy cluster 1RXS J0603.3+4214 hosts a 1.9 Mpc long, bright radio relic with a peculiar linear morphology. Using hydrodynamical N-body adaptive mesh refinement simulations of the merger between three initially hydrostatic clusters in an idealized set-up, we are able to reconstruct the morphology of the radio relic. Based on our simulation, we can constrain the merger geometry, predict lensing mass measurements and X-ray observations. Comparing such models to X-ray, redshift and lensing data will validate the geometry of this complex merger which helps in constraining the parameters for shock acceleration of electrons that produces the radio relic.

  4. EVIDENCE FOR A CLUMPY, ROTATING GAS DISK IN A SUBMILLIMETER GALAXY AT z = 4

    SciTech Connect

    Hodge, J. A.; Walter, F.; Carilli, C. L.; De Blok, W. J. G.; Riechers, D.; Daddi, E.

    2012-11-20

    We present Karl G. Jansky Very Large Array observations of the CO(2-1) emission in the z = 4.05 submillimeter galaxy (SMG) GN20. These high-resolution data allow us to image the molecular gas at 1.3 kpc resolution just 1.6 Gyr after the big bang. The data reveal a clumpy, extended gas reservoir, 14 {+-} 4 kpc in diameter, in unprecedented detail. A dynamical analysis shows that the data are consistent with a rotating disk of total dynamical mass 5.4 {+-} 2.4 Multiplication-Sign 10{sup 11} M {sub Sun }. We use this dynamical mass estimate to constrain the CO-to-H{sub 2} mass conversion factor ({alpha}{sub CO}), finding {alpha}{sub CO} = 1.1 {+-} 0.6 M {sub Sun }(K km s{sup -1} pc{sup 2}){sup -1}. We identify five distinct molecular gas clumps in the disk of GN20 with masses a few percent of the total gas mass, brightness temperatures of 16-31K, and surface densities of >3200-4500 Multiplication-Sign ({alpha}{sub CO}/0.8) M {sub Sun} pc{sup -2}. Virial mass estimates indicate they could be self-gravitating, and we constrain their CO-to-H{sub 2} mass conversion factor to be <0.2-0.7 M {sub Sun }(K km s{sup -1} pc{sup 2}){sup -1}. A multiwavelength comparison demonstrates that the molecular gas is concentrated in a region of the galaxy that is heavily obscured in the rest-frame UV/optical. We investigate the spatially resolved gas excitation and find that the CO(6-5)/CO(2-1) ratio is constant with radius, consistent with star formation occurring over a large portion of the disk. We discuss the implications of our results in the context of different fueling scenarios for SMGs.

  5. Segregation properties of galaxies

    SciTech Connect

    Santiago, B.X.; Da Costa, L.N. )

    1990-10-01

    Using the recently completed Southern Sky Redshift Survey, in conjunction with measurements of the central surface brightness, the existence of segregation in the way galaxies of different morphology and surface brightness are distributed in space is investigated. Results indicate that there is some evidence that low surface brightness galaxies are more randomly distributed than brighter ones and that this effect is independent of the well-known tendency of early-type galaxies to cluster more strongly than spirals. Presuming that the observed clustering was established at the epoch of galaxy formation, it may provide circumstantial evidence for biased galaxy formation. 24 refs.

  6. Violent galaxy evolution in the Frontier Fields clusters

    NASA Astrophysics Data System (ADS)

    Ebeling, Harald; McPartland, Conor; Blumenthal, Kelly; Roediger, Elke

    2015-08-01

    In a recent study we used customized morphological selection criteria to identify potential ram-pressure stripping events in shallow HST images of MACS clusters at z=0.3-0.7 and found tantalising evidence of such violent evolution (a) being at least partly triggered by galaxy mergers and (b) causing extensive star formation and thus brightening of the affected galaxies. Due to the limited depth of the HST data used, our project focused (by design and necessity) on the brightest galaxies. We here present results of a similar survey for “jellyfish” galaxies conducted using the much deeper, multi-passband imaging data of the Frontier Fields clusters that allow us to probe much farther into the luminosity function of ram-pressure stripping in some of the most massive and most dynamically disturbed clusters known.

  7. Sleep deprivation disturbed regional brain activity in healthy subjects: evidence from a functional magnetic resonance-imaging study

    PubMed Central

    Wang, Li; Chen, Yin; Yao, Ying; Pan, Yu; Sun, Yi

    2016-01-01

    Objective The aim of this study was to use amplitude of low-frequency fluctuation (ALFF) to explore regional brain activities in healthy subjects after sleep deprivation (SD). Materials and methods A total of 16 healthy subjects (eight females, eight males) underwent the session twice: once was after normal sleep (NS), and the other was after SD. ALFF was used to assess local brain features. The mean ALFF-signal values of the different brain areas were evaluated to investigate relationships with clinical features and were analyzed with a receiver-operating characteristic curve. Results Compared with NS subjects, SD subjects showed a lower response-accuracy rate, longer response time, and higher lapse rate. Compared with NS subjects, SD subjects showed higher ALFF area in the right cuneus and lower ALFF area in the right lentiform nucleus, right claustrum, left dorsolateral prefrontal cortex, and left inferior parietal cortex. ALFF differences in regional brain areas showed high sensitivity and specificity. In the SD group, mean ALFF of the right claustrum showed a significant positive correlation with accuracy rate (r=0.687, P=0.013) and a negative correlation with lapse rate (r=−0.706, P=0.01). Mean ALFF of the dorsolateral prefrontal cortex showed a significant positive correlation with response time (r=0.675, P=0.016). Conclusion SD disturbed the regional brain activity of the default-mode network, its anticorrelated “task-positive” network, and the advanced cognitive function brain areas. PMID:27110113

  8. SDSS-IV MaNGA: faint quenched galaxies - I. Sample selection and evidence for environmental quenching

    NASA Astrophysics Data System (ADS)

    Penny, Samantha J.; Masters, Karen L.; Weijmans, Anne-Marie; Westfall, Kyle B.; Bershady, Matthew A.; Bundy, Kevin; Drory, Niv; Falcón-Barroso, Jesús; Law, David; Nichol, Robert C.; Thomas, Daniel; Bizyaev, Dmitry; Brownstein, Joel R.; Freischlad, Gordon; Gaulme, Patrick; Grabowski, Katie; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Roman-Lopes, Alexandre; Pan, Kaike; Simmons, Audrey; Wake, David A.

    2016-11-01

    Using kinematic maps from the Sloan Digital Sky Survey (SDSS) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, we reveal that the majority of low-mass quenched galaxies exhibit coherent rotation in their stellar kinematics. Our sample includes all 39 quenched low-mass galaxies observed in the first year of MaNGA. The galaxies are selected with Mr > -19.1, stellar masses 109 M⊙ < M* < 5 × 109 M⊙, EWHα < 2 Å, and all have red colours (u - r) > 1.9. They lie on the size-magnitude and σ-luminosity relations for previously studied dwarf galaxies. Just six (15 ± 5.7 per cent) are found to have rotation speeds ve, rot < 15 km s-1 at ˜1 Re, and may be dominated by pressure support at all radii. Two galaxies in our sample have kinematically distinct cores in their stellar component, likely the result of accretion. Six contain ionized gas despite not hosting ongoing star formation, and this gas is typically kinematically misaligned from their stellar component. This is the first large-scale Integral Field Unit (IFU) study of low-mass galaxies selected without bias against low-density environments. Nevertheless, we find the majority of these galaxies are within ˜1.5 Mpc of a bright neighbour (MK < -23; or M* > 5 × 1010 M⊙), supporting the hypothesis that galaxy-galaxy or galaxy-group interactions quench star formation in low-mass galaxies. The local bright galaxy density for our sample is ρproj = 8.2 ± 2.0 Mpc-2, compared to ρproj = 2.1 ± 0.4 Mpc-2 for a star-forming comparison sample, confirming that the quenched low-mass galaxies are preferentially found in higher density environments.

  9. SDSS-IV MaNGA: Faint quenched galaxies I- Sample selection and evidence for environmental quenching

    NASA Astrophysics Data System (ADS)

    Penny, Samantha J.; Masters, Karen L.; Weijmans, Anne-Marie; Westfall, Kyle B.; Bershady, Matthew A.; Bundy, Kevin; Drory, Niv; Falcón-Barroso, Jesús; Law, David; Nichol, Robert C.; Thomas, Daniel; Bizyaev, Dmitry; Brownstein, Joel R.; Freischlad, Gordon; Gaulme, Patrick; Grabowski, Katie; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Roman-Lopes, Alexandre; Pan, Kaike; Simmons, Audrey; Wake, David A.

    2016-08-01

    Using kinematic maps from the Sloan Digital Sky Survey (SDSS) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, we reveal that the majority of low-mass quenched galaxies exhibit coherent rotation in their stellar kinematics. Our sample includes all 39 quenched low-mass galaxies observed in the first year of MaNGA. The galaxies are selected with Mr > -19.1, stellar masses 109 M⊙ < M⋆ < 5 × 109 M⊙, EWHα < 2 Å, and all have red colours (u - r) > 1.9. They lie on the size-magnitude and σ-luminosity relations for previously studied dwarf galaxies. Just six (15 ± 5.7 per cent) are found to have rotation speeds ve, rot < 15 km s-1 at ˜1 Re, and may be dominated by pressure support at all radii. Two galaxies in our sample have kinematically distinct cores in their stellar component, likely the result of accretion. Six contain ionised gas despite not hosting ongoing star formation, and this gas is typically kinematically misaligned from their stellar component. This is the first large-scale Integral Field Unit (IFU) study of low mass galaxies selected without bias against low-density environments. Nevertheless, we find the majority of these galaxies are within ˜1.5 Mpc of a bright neighbour (MK < -23; or M⋆ > 5 × 1010 M⊙), supporting the hypothesis that galaxy-galaxy or galaxy-group interactions quench star formation in low-mass galaxies. The local bright galaxy density for our sample is ρproj = 8.2 ± 2.0 Mpc-2, compared to ρproj = 2.1 ± 0.4 Mpc-2 for a star forming comparison sample, confirming that the quenched low mass galaxies are preferentially found in higher density environments.

  10. EVIDENCE OF QUASI-LINEAR SUPER-STRUCTURES IN THE COSMIC MICROWAVE BACKGROUND AND GALAXY DISTRIBUTION

    SciTech Connect

    Inoue, Kaiki Taro; Sakai, Nobuyuki; Tomita, Kenji

    2010-11-20

    Recent measurements of hot and cold spots on the cosmic microwave background (CMB) sky suggest the presence of super-structures on (>100 h {sup -1} Mpc) scales. We develop a new formalism to estimate the expected amplitude of temperature fluctuations due to the integrated Sachs-Wolfe (ISW) effect from prominent quasi-linear structures. Applying the developed tools to the observed ISW signals from voids and clusters in catalogs of galaxies at redshifts z < 1, we find that they indeed imply a presence of quasi-linear super-structures with a comoving radius of 100 {approx} 300 h {sup -1} Mpc and a density contrast |{delta}| {approx} O(0.1). We also find that the observed ISW signals are at odds with the concordant {Lambda} cold dark matter model that predicts Gaussian primordial perturbations at {approx}>3{sigma} level. We confirm that the mean temperature around the CMB cold spot in the southern Galactic hemisphere filtered by a compensating top-hat filter deviates from the mean value at {approx}3{sigma} level, implying that a quasi-linear supervoid or an underdensity region surrounded by a massive wall may reside at low redshifts z < 0.3 and the actual angular size (16{sup 0}-17{sup 0}) may be larger than the apparent size (4{sup 0}-10{sup 0}) discussed in literature. Possible solutions are briefly discussed.

  11. Evidence for Unresolved γ-Ray Point Sources in the Inner Galaxy.

    PubMed

    Lee, Samuel K; Lisanti, Mariangela; Safdi, Benjamin R; Slatyer, Tracy R; Xue, Wei

    2016-02-01

    We present a new method to characterize unresolved point sources (PSs) generalizing traditional template fits to account for non-Poissonian photon statistics. We apply this method to Fermi Large Area Telescope γ-ray data to characterize PS populations at high latitudes and in the Inner Galaxy. We find that PSs (resolved and unresolved) account for ∼50% of the total extragalactic γ-ray background in the energy range ∼1.9 to 11.9 GeV. Within 10° of the Galactic Center with |b|≥2°, we find that ∼5%-10% of the flux can be accounted for by a population of unresolved PSs distributed consistently with the observed ∼GeV γ-ray excess in this region. The excess is fully absorbed by such a population, in preference to dark-matter annihilation. The inferred source population is dominated by near-threshold sources, which may be detectable in future searches. PMID:26894697

  12. Evidence for an Additional Heat Source in the Warm Ionized Medium of Galaxies.

    PubMed

    Reynolds; Haffner; Tufte

    1999-11-01

    Spatial variations of the [S ii]/Halpha and [N ii]/Halpha line intensity ratios observed in the gaseous halo of the Milky Way and other galaxies are inconsistent with pure photoionization models. They appear to require a supplemental heating mechanism that increases the electron temperature at low densities, ne. This would imply that in addition to photoionization, which has a heating rate per unit volume proportional to n2e, there is another source of heat with a rate per unit volume proportional to a lower power of ne. One possible mechanism is the dissipation of interstellar plasma turbulence, which, according to Minter & Spangler, heats the ionized interstellar medium in the Milky Way at a rate of approximately 1x10-25ne ergs cm-3 s-1. If such a source were present, it would dominate over photoionization heating in regions where ne less, similar0.1 cm-3, producing the observed increases in the [S ii]/Halpha and [N ii]/Halpha intensity ratios at large distances from the galactic midplane as well as accounting for the constancy of [S ii]/[N ii], which is not explained by pure photoionization. Other supplemental heating sources, such as magnetic reconnection, cosmic rays, or photoelectric emission from small grains, could also account for these observations, provided they supply approximately 10-5 ergs s-1 per square centimeter of the Galactic disk to the warm ionized medium.

  13. On VI Observations of Galaxy Clusters: Evidence for Modest Cooling Flows

    NASA Astrophysics Data System (ADS)

    Bregman, Joel N.; Fabian, A. C.; Miller, Eric D.; Irwin, Jimmy A.

    2006-05-01

    A prediction of the galaxy-cluster cooling flow model is that as gas cools from the ambient cluster temperature, emission lines are produced in gas at subsequently decreasing temperatures. Gas passing through 105.5 K emits in the lines of O VI λλ1032, 1035, and here we report a FUSE study of these lines in three cooling flow clusters, Abell 426, Abell 1795, and AWM 7. No emission was detected from AWM 7, but O VI is detected from the centers of Abell 426 and Abell 1795, and possibly to the south of the center in Abell 1795, where X-ray and optical emission line filaments lie. In Abell 426 these line luminosities imply a cooling rate of 32+/-6 Msolar yr-1 within the central r=6.2 kpc region, while for Abell 1795 the central cooling rate is 26+/-7 Msolar yr-1 (within r=22 kpc), and about 42+/-9 Msolar yr-1 including the southern pointing. Including other studies, three of six clusters have O VI emission, and they also have star formation as well as emission lines from 104 K gas. These observations are generally consistent with the cooling flow model, but at a rate closer to 30 Msolar yr-1 than to the originally suggested values of 102-10 3 Msolar yr-1.

  14. Evidence for a non-universal stellar initial mass function in low-redshift high-density early-type galaxies

    NASA Astrophysics Data System (ADS)

    Dutton, Aaron A.; Mendel, J. Trevor; Simard, Luc

    2012-05-01

    We determine an absolute calibration of stellar mass-to-light ratios for the densest ≃3 per cent of early-type galaxies in the local Universe (redshift z≃ 0.08) from Sloan Digital Sky Survey (SDSS) Data Release 7. This sample of ˜4000 galaxies has, assuming a Chabrier initial mass function (IMF), effective stellar surface densities Σe > 2500 M⊙ pc-2, stellar population synthesis (SPS) stellar masses log10(MSPS/M⊙) < 10.8 and aperture velocity dispersions of ? (68 per cent range). In contrast to typical early-type galaxies, we show that these dense early-type galaxies follow the virial Fundamental Plane, which suggests that mass follows light. With the additional assumption that any dark matter does not follow the light, the dynamical masses of dense galaxies provide a direct measurement of stellar masses. Our dynamical masses (Mdyn), obtained from the spherical Jeans equations, are only weakly sensitive to the choice of anisotropy (β) due to the relatively large aperture of the SDSS fibre for these galaxies: Rap≃ 1.5Re. Assuming isotropic orbits (β= 0), we find a median log10(Mdyn/MSPS) = 0.233 ± 0.003, consistent with a Salpeter IMF, while more bottom-heavy IMFs and standard Milky Way IMFs are strongly disfavoured. Our results are consistent with, but do not require, a dependence of the IMF on dynamical mass or velocity dispersion. We find evidence for a colour dependence to the IMF such that redder galaxies have heavier IMFs with Mdyn/MSPS∝ (g-r)1.13 ± 0.09. This may reflect a more fundamental dependence of the IMF on the age or metallicity of a stellar population, or the density at which the stars formed.

  15. The Lyα–LyC Connection: Evidence for an Enhanced Contribution of UV-faint Galaxies to Cosmic Deionization

    NASA Astrophysics Data System (ADS)

    Dijkstra, Mark; Gronke, Max; Venkatesan, Aparna

    2016-09-01

    The escape of ionizing Lyman continuum (LyC) photons requires the existence of low-N H i sightlines, which also promote escape of Lyα. We use a suite of 2500 Lyα Monte-Carlo radiative transfer simulations through models of dusty, clumpy interstellar (“multiphase”) media from Gronke & Dijkstra, and compare the escape fractions of Lyα ({f}{{esc}}{{Ly}α }) and LyC radiation ({f}{{esc}}{{ion}}). We find that {f}{{esc}}{{ion}} and {f}{{esc}}{{Ly}α } are correlated: galaxies with a low {f}{{esc}}{{Ly}α } consistently have a low {f}{{esc}}{{ion}}, while galaxies with a high {f}{{esc}}{{Ly}α } exhibit a large dispersion in {f}{{esc}}{{ion}}. We argue that there is increasing observational evidence that Lyα escapes more easily from UV-faint galaxies. The correlation between {f}{{esc}}{{ion}} and {f}{{esc}}{{Ly}α } then implies that UV-faint galaxies contribute more to the ionizing background than implied by the faint-end slope of the UV luminosity function. In multiphase gases, the ionizing escape fraction is most strongly affected by the cloud covering factor, f cl, which implies that {f}{{esc}}{{ion}} is closely connected to the observed Lyα spectral line shape. Specifically, LyC-emitting galaxies typically having narrower, more symmetric line profiles. This prediction is qualitatively similar to that for “shell models.”

  16. Jellyfish Galaxy Candidates at Low Redshift

    NASA Astrophysics Data System (ADS)

    Poggianti, B. M.; Fasano, G.; Omizzolo, A.; Gullieuszik, M.; Bettoni, D.; Moretti, A.; Paccagnella, A.; Jaffé, Y. L.; Vulcani, B.; Fritz, J.; Couch, W.; D'Onofrio, M.

    2016-03-01

    Galaxies that are being stripped of their gas can sometimes be recognized from their optical appearance. Extreme examples of stripped galaxies are the so-called “jellyfish galaxies” that exhibit tentacles of debris material with a characteristic jellyfish morphology. We have conducted the first systematic search for galaxies that are being stripped of their gas at low-z (z = 0.04-0.07) in different environments, selecting galaxies with varying degrees of morphological evidence for stripping. We have visually inspected B- and V-band images and identified 344 candidates in 71 galaxy clusters of the OMEGAWINGS+WINGS sample and 75 candidates in groups and lower mass structures in the PM2GC sample. We present the atlas of stripping candidates and a first analysis of their environment and their basic properties, such as morphologies, star formation rates and galaxy stellar masses. Candidates are found in all clusters and at all clustercentric radii, and their number does not correlate with the cluster velocity dispersion σ or X-ray luminosity LX. Interestingly, convincing cases of candidates are also found in groups and lower mass halos (1011-1014M⊙), although the physical mechanism at work needs to be securely identified. All the candidates are disky, have stellar masses ranging from log M/M⊙ < 9 to > 11.5 and the majority of them form stars at a rate that is on average a factor of 2 higher (2.5σ) compared to non-stripped galaxies of similar mass. The few post-starburst and passive candidates have weak stripping evidence. We conclude that disturbed morphologies suggestive of stripping phenomena are ubiquitous in clusters and could be present even in groups and low mass halos. Further studies will reveal the physics of the gas stripping and clarify the mechanisms at work.

  17. Physical Exercise for the Treatment of Neuropsychiatric Disturbances in Alzheimer's Dementia: Possible Mechanisms, Current Evidence and Future Directions.

    PubMed

    Matura, Silke; Carvalho, André F; Alves, Gilberto S; Pantel, Johannes

    2016-01-01

    Behavioral and psychological symptoms of dementia (BPSD), also known as neuropsychiatric or non-cognitive symptoms are common and often distressing features of Alzheimer's Dementia. BPSD significantly increase patient suffering, early institutionalization and caregiver's burden. The clinical management of BPSD is dominated by a pharmacological approach, although these medications often come with serious adverse side-effects. There are only few nonpharmacological treatment strategies for BPSD. A substantial amount of intervention studies that have investigated non-pharmacological treatment options for BPSD have focused on physical exercise. Although these studies are very heterogeneous in terms of type and severity of dementia, as well as type and duration of the exercise intervention, the overall picture shows a positive effect of physical exercise in alleviating BPSD. There is evidence that numerous mechanisms contribute to the positive effect of physical exercise on BPSD. No attempt has been undertaken so far to give an overview of the existing knowledge regarding these mechanisms. Therefore, the current review aims to integrate the existing evidence on psychological and neurobiological mechanisms that contribute to the beneficial effects of physical exercise in ameliorating BPSD in Alzheimer's dementia. A discussion of psychological mechanisms such as improved sleep and stress reduction will be followed by a discussion of neurobiological mechanisms including the exercise induced change in neurotransmitter concentrations, increased synthesis of neurotrophins and immune activation. The review closes with recommendations for future research to overcome the shortcomings of existing studies and broaden the current knowledge on the positive effects of physical exercise on BPSD.

  18. Evidence for a Massive, Extended Circumgalactic Medium Around the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Lehner, Nicolas; Howk, J. Christopher; Wakker, Bart P.

    2015-05-01

    We demonstrate the presence of an extended and massive circumgalactic medium (CGM) around Messier 31 using archival HST Cosmic Origins Spectrograph ultraviolet spectroscopy of 18 QSOs projected within two virial radii of M31 ({{R}vir}=300 kpc). We detect absorption from Si iii at -300≲ {{v}LSR}≲ -150 km s-1 toward all three sightlines at R≲ 0.2{{R}vir}, 3 of 4 sightlines at 0.8≲ R/{{R}vir}≲ 1.1, and possibly 1 of 11 at 1.1\\lt R/{{R}vir}≲ 1.8. We present several arguments that the gas at these velocities observed in these directions originates from the M31 CGM rather than the Local Group or Milky Way CGM or Magellanic Stream. We show that the dwarf galaxies located in the CGM of M31 have very similar velocities over similar projected distances from M31. We find a non-trivial relationship only at these velocities between the column densities (N) of all the ions and R, whereby N decreases with increasing R. At R\\lt 0.8{{R}vir}, the covering fraction is close to unity for Si iii and C iv ({{f}c}˜ 60%-97% at the 90% confidence level), but drops to {{f}c}≲ 10%-20% at R≳ {{R}vir}. We show that the M31 CGM gas is bound, multiphase, predominantly ionized, and is more highly ionized gas at larger R. We estimate using Si ii, Si iii, and Si iv, a CGM metal mass of ≳ 2× {{10}6} M⊙ and gas mass of ≳ 3× {{10}9}({{Z}⊙ }/Z) M⊙ within 0.2{{R}vir}, and possibly a factor of ˜10 larger within {{R}vir}, implying substantial metal and gas masses in the CGM of M31. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract No. NAS5-26555.

  19. Galaxy pairs in the Sloan Digital Sky Survey - III. Evidence of induced star formation from optical colours

    NASA Astrophysics Data System (ADS)

    Patton, David R.; Ellison, Sara L.; Simard, Luc; McConnachie, Alan W.; Mendel, J. Trevor

    2011-03-01

    We have assembled a large, high-quality catalogue of galaxy colours from the Sloan Digital Sky Survey Data Release 7 and have identified 21 347 galaxies in pairs spanning a range of projected separations (rp < 80 h-170 kpc), relative velocities (Δv < 10 000 km s-1, which includes projected pairs that are essential for quality control) and stellar mass ratios (from 1:10 to 10:1). We find that the red fraction of galaxies in pairs is higher than that of a control sample matched in stellar mass and redshift, and demonstrate that this difference is likely due to the fact that galaxy pairs reside in higher density environments than non-paired galaxies. We detect clear signs of interaction-induced star formation within the blue galaxies in pairs, as evidenced by a higher fraction of extremely blue galaxies, along with blueward offsets between the colours of paired versus control galaxies. These signs are strongest in close pairs (rp < 30 h-170 kpc and Δv < 200 km s-1), diminish for more widely separated pairs (rp > 60 h-170 kpc and Δv < 200 km s-1) and disappear for close projected pairs (rp < 30 h-170 kpc and Δv > 3000 km s-1). These effects are also stronger in central (fibre) colours than in global colours and are found primarily in low- to medium-density environments. Conversely, no such trends are seen in red galaxies, apart from a small reddening at small separations, which may result from residual errors with photometry in crowded fields. When interpreted in conjunction with a simple model of induced starbursts, these results are consistent with a scenario in which close pericentre passages trigger induced star formation in the centres of galaxies which are sufficiently gas rich, after which time the galaxies gradually redden as they separate and their starbursts age.

  20. X-radiation from clusters of galaxies: Spectral evidence for a hot evolved gas

    NASA Technical Reports Server (NTRS)

    Serlemitsos, P. J.; Smith, B. W.; Boldt, E. A.; Holt, S. S.; Swank, J. H.

    1976-01-01

    OSO-8 observations of the X-ray flux in the range 2-60 keV from the Virgo, Perseus, and Coma Clusters provide strong evidence for the thermal origin of the radiation, including iron line emission. The data are adequately described by emission from an isothermal plasma with an iron abundance in near agreement with cosmic levels. A power law description is generally less acceptable and is ruled out in the case of Perseus. Implications on the origin of the cluster gas are discussed.

  1. X-radiation from clusters of galaxies - Spectral evidence for a hot evolved gas

    NASA Technical Reports Server (NTRS)

    Serlemitsos, P. J.; Smith, B. W.; Boldt, E. A.; Holt, S. S.; Swank, J. H.

    1977-01-01

    OSO-8 observations of the X-ray flux in the range between 2 and 60 keV from the Virgo, Perseus, and Coma clusters provide strong evidence for the thermal origin of the radiation, including iron-line emission. The data are adequately described by emission from an isothermal plasma with an iron abundance in near agreement with cosmic levels. A power-law description is generally less acceptable and is ruled out in the case of Perseus. Implications of the origin of the cluster gas are discussed.

  2. LONG GRBs ARE METALLICITY-BIASED TRACERS OF STAR FORMATION: EVIDENCE FROM HOST GALAXIES AND REDSHIFT DISTRIBUTION

    SciTech Connect

    Wang, F. Y.; Dai, Z. G. E-mail: dzg@nju.edu.cn

    2014-07-01

    We investigate the mass distribution of long gamma-ray burst (GRB) host galaxies and the redshift distribution of long GRBs by considering that long GRBs occur in low-metallicity environments. We calculate the upper limit on the stellar mass of a galaxy which can produce long GRBs by utilizing the mass-metallicity (M-Z) relation of galaxies. After comparing with the observed GRB host galaxies masses, we find that the observed GRB host galaxy masses can fit the predicted masses well if GRBs occur in low-metallicity 12 + log (O/H){sub KK04} < 8.7. GRB host galaxies have low metallicity, low mass, and high star formation rate compared with galaxies of seventh data release of the Sloan Digital Sky Survey. We also study the cumulative redshift distribution of the latest Swift long GRBs by adding dark GRBs and 10 new GRBs redshifts from the TOUGH survey. The observed discrepancy between the GRB rate and the star formation history can be reconciled by considering that GRBs tend to occur in low-metallicity galaxies with 12 + log (O/H){sub KK04} < 8.7. We conclude that the metallicity cutoff that can produce long GRBs is about 12 + log (O/H){sub KK04} < 8.7 from the host mass distribution and redshift distribution.

  3. Evidence for altered monoamine activity and emotional and cognitive disturbance in marmoset monkeys exposed to early life stress.

    PubMed

    Pryce, Christopher R; Dettling, Andrea; Spengler, Marianne; Spaete, Corinne; Feldon, Joram

    2004-12-01

    In common marmoset monkeys (Callithrix jacchus, order Primates), infants aged 2-28 days were deprived of parental care for 30-120 min/day in order to investigate the long-term effects of this neglect-stress model on affect and cognition in a primate species. Basal morning levels of urinary cortisol across the first year of life were unaffected in early deprived marmosets relative to their sibling controls. Basal morning levels of urinary dopamine were chronically increased. This peripheral increase in dopamine activity could represent a marker for central dopamine hyperactivity. Certainly, subadult early deprived marmosets exhibited performance deficits in two dopamine-regulated neuropsychological tasks. They demonstrated: (1) impaired behavioral inhibition in an object reaching with detour task, exhibiting significantly more nonreinforced forward reaches to a reward visible inside a cube that could only be retrieved through an opening to the side of the cube; and (2) impaired reversal learning in a two-way discrimination task based on visual icons presented on a touch-sensitive computer screen. These findings provide further evidence for the relevance of this novel primate model of parent-infant neglect to the environmental causes and mechanisms of human developmental psychopathology.

  4. Evidence for wide-spread active galactic nucleus-driven outflows in the most massive z ∼ 1-2 star-forming galaxies

    SciTech Connect

    Genzel, R.; Förster Schreiber, N. M.; Rosario, D.; Lang, P.; Lutz, D.; Wisnioski, E.; Wuyts, E.; Wuyts, S.; Bandara, K.; Bender, R.; Berta, S.; Kurk, J.; Mendel, J. T.; Tacconi, L. J.; Wilman, D.; Beifiori, A.; Burkert, A.; Buschkamp, P.; Chan, J.; Brammer, G. E-mail: genzel@mpe.mpg.de; and others

    2014-11-20

    In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M {sub *}/M {sub ☉}) ≥ 10.9) z ∼ 1-3 star-forming galaxies by increasing the sample size by a factor of six (to 44 galaxies above log(M {sub *}/M {sub ☉}) ≥ 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS{sup 3D}spectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Hα, [N II], and [S II] lines ∼450-5300 km s{sup –1}), with large [N II]/Hα ratios, above log(M {sub *}/M {sub ☉}) ∼ 10.9, with about two-thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z ∼ 1 and ∼2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGNs), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation.

  5. Galaxy M82

    NASA Technical Reports Server (NTRS)

    1999-01-01

    A colorful image showing violent star formation triggered when two galaxies bumped into each other has been captured by NASA's Hubble Space Telescope.

    In the image, the starburst galaxy M82 has a disturbed appearance caused by violent activity after an ancient encounter with its large galactic neighbor, M81. The image, taken by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif., is online at http://www.jpl.nasa.gov/pictures/wfpc .

    The huge lanes of dust that crisscross M82's disk are another telltale sign of the flurry of star formation. Below the center and to the right, a strong galactic wind is spewing knotty filaments of hydrogen and nitrogen gas. More than 100 super star clusters -- very bright, compact groupings of about 100,000 stars -- appear as white dots sprinkled throughout the galaxy's central area. The dark area just above center is a huge dust cloud.

    A collaboration of European and American scientists used these clusters to date the interaction between M82 and M81 to about 600 million years ago, when a region called M82 B (the bright area just below and to the left of the central dust cloud) exploded with new stars. Scientists have found that this ancient starburst was triggered by the encounter with M81. The results are published in the February 2001 issue of the Astronomical Journal.

    This discovery provides evidence linking the birth of super star clusters to violent interaction between galaxies. These clusters also provide insight into the rough-and-tumble universe of long ago, when galaxies bumped into each other more frequently.

    M82 is located 12 million light-years from Earth in the constellation Ursa Major. The picture was taken Sept. 15, 1997. The natural-color composite was constructed from three exposures taken with blue, green and red filters.

    The Space Telescope Science Institute, Baltimore, Md., manages space operations for the Hubble Space Telescope

  6. Evidence for major mergers of galaxies at 2 ≲ z < 4 in the VVDS and VUDS surveys

    NASA Astrophysics Data System (ADS)

    Tasca, L. A. M.; Le Fèvre, O.; López-Sanjuan, C.; Wang, P.-W.; Cassata, P.; Garilli, B.; Ilbert, O.; Le Brun, V.; Lemaux, B. C.; Maccagni, D.; Tresse, L.; Bardelli, S.; Contini, T.; Charlot, S.; Cucciati, O.; Fontana, A.; Giavalisco, M.; Kneib, J.-P.; Salvato, M.; Taniguchi, Y.; Vergani, D.; Zamorani, G.; Zucca, E.

    2014-05-01

    Context. The mass assembly of galaxies can proceed through different physical processes. Here we report on the spectroscopic identification of close physical pairs of galaxies at redshifts 2 ≲ z< 4 and discuss the impact of major mergers in building galaxies at these early cosmological times. Aims: We aim to identify and characterize close physical pairs of galaxies destined to merge and use their properties to infer the contribution of merging processes to the early mass assembly of galaxies. Methods: We searched for galaxy pairs with a transverse separation rp ≤ 25h-1 kpc and a velocity difference Δv ≤ 500 km s-1 using early data from the VIMOS Ultra Deep Survey (VUDS) that comprise a sample of 1111 galaxies with spectroscopic redshifts measurements at redshifts 1.8 ≤ z ≤ 4 in the COSMOS, ECDFS, and VVDS-02h fields, combined with VVDS data. We analysed their spectra and associated visible and near-infrared photometry to assess the main properties of merging galaxies that have an average stellar mass M⋆ = 2.3 × 1010 M⊙ at these redshifts. Results: Using the 12 physical pairs found in our sample we obtain a first robust measurement of the major merger fraction at these redshifts, fMM = 19.4-6+9%. These pairs are expected to merge within 1 Gyr on average each producing a more massive galaxy by the time the cosmic star formation peaks at z ~ 1 - 2. Using the pairs' merging time scales, we derive a merging rate of RMM = 0.17-0.05+0.08 Gyr-1. From the average mass ratio between galaxies in the pairs, the stellar mass of the resulting galaxy after merging will be ~60% higher than the most massive galaxy in the pair before merging. We conclude that major merging of galaxy pairs is on-going at 2 ≲ z< 4 and is significantly contributing to the major mass assembly phase of galaxies at this early epoch. Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under Large Programmes 070.A-9007, 177.A-0837, and 185.A

  7. Galaxy evolution. Evidence for mature bulges and an inside-out quenching phase 3 billion years after the Big Bang.

    PubMed

    Tacchella, S; Carollo, C M; Renzini, A; Förster Schreiber, N M; Lang, P; Wuyts, S; Cresci, G; Dekel, A; Genzel, R; Lilly, S J; Mancini, C; Newman, S; Onodera, M; Shapley, A; Tacconi, L; Woo, J; Zamorani, G

    2015-04-17

    Most present-day galaxies with stellar masses ≥10(11) solar masses show no ongoing star formation and are dense spheroids. Ten billion years ago, similarly massive galaxies were typically forming stars at rates of hundreds solar masses per year. It is debated how star formation ceased, on which time scales, and how this "quenching" relates to the emergence of dense spheroids. We measured stellar mass and star-formation rate surface density distributions in star-forming galaxies at redshift 2.2 with ~1-kiloparsec resolution. We find that, in the most massive galaxies, star formation is quenched from the inside out, on time scales less than 1 billion years in the inner regions, up to a few billion years in the outer disks. These galaxies sustain high star-formation activity at large radii, while hosting fully grown and already quenched bulges in their cores. PMID:25883353

  8. Galaxy evolution. Evidence for mature bulges and an inside-out quenching phase 3 billion years after the Big Bang.

    PubMed

    Tacchella, S; Carollo, C M; Renzini, A; Förster Schreiber, N M; Lang, P; Wuyts, S; Cresci, G; Dekel, A; Genzel, R; Lilly, S J; Mancini, C; Newman, S; Onodera, M; Shapley, A; Tacconi, L; Woo, J; Zamorani, G

    2015-04-17

    Most present-day galaxies with stellar masses ≥10(11) solar masses show no ongoing star formation and are dense spheroids. Ten billion years ago, similarly massive galaxies were typically forming stars at rates of hundreds solar masses per year. It is debated how star formation ceased, on which time scales, and how this "quenching" relates to the emergence of dense spheroids. We measured stellar mass and star-formation rate surface density distributions in star-forming galaxies at redshift 2.2 with ~1-kiloparsec resolution. We find that, in the most massive galaxies, star formation is quenched from the inside out, on time scales less than 1 billion years in the inner regions, up to a few billion years in the outer disks. These galaxies sustain high star-formation activity at large radii, while hosting fully grown and already quenched bulges in their cores.

  9. AGN feedback in groups of galaxies: a joint X-ray/low-frequency radio study

    NASA Astrophysics Data System (ADS)

    Giacintucci, S.; O'Sullivan, E.; Vrtilek, J. M.; Raychaudhury, S.; David, L. P.; Venturi, T.; Athreya, R.; Gitti, M.

    2010-07-01

    We present an ongoing, low-frequency radio/X-ray study of 18 nearby galaxy groups, chosen for the evidence, either in the X-ray or radio images, of AGN/intragroup gas interaction. We have obtained radio observations at 235 MHz and 610 MHz with the Giant Metrewave Radio Telescope (GMRT) for all the groups, and 327 MHz and 150 MHz for a few. We present results of the recent Chandra/GMRT study of the interesting case of AWM 4, a relaxed poor cluster of galaxies with no evidence of a large cool core and no X-ray cavities associated with the central radio galaxy. Our analysis shows how joining low-frequency radio data (to track the history of AGN outbursts) with X-ray data (to determine the state of the hot gas, its disturbances, heating and cooling) can provide a unique insight into the nature of the feedback mechanism in galaxy groups.

  10. The "toothbrush-relic": evidence for a coherent linear 2-Mpc scale shock wave in a massive merging galaxy cluster?

    NASA Astrophysics Data System (ADS)

    van Weeren, R. J.; Röttgering, H. J. A.; Intema, H. T.; Rudnick, L.; Brüggen, M.; Hoeft, M.; Oonk, J. B. R.

    2012-10-01

    Some merging galaxy clusters host diffuse extended radio emission, so-called radio halos and relics, unrelated to individual galaxies. The origin of these halos and relics is still debated, although there is compelling evidence now that they are related to cluster merger events. Here we present detailed Westerbork Synthesis Radio Telescope (WSRT) and Giant Metrewave Radio Telescope (GMRT) radio observations between 147 MHz and 4.9 GHz of a new radio-selected galaxy cluster 1RXS J0603.3+4214, for which we find a redshift of 0.225. The cluster is detected as an extended X-ray source in the ROSAT All Sky Survey with an X-ray luminosity of LX, 0.1-2.4 keV ~ 1 × 1045 erg s-1. The cluster hosts a large bright 1.9 Mpc radio relic, an elongated ~2 Mpc radio halo, and two fainter smaller radio relics. The large radio relic has a peculiar linear morphology. For this relic we observe a clear spectral index gradient from the front of the relic towards the back, in the direction towards the cluster center. Parts of this relic are highly polarized with a polarization fraction of up to 60%. We performed rotation measure (RM) synthesis between 1.2 and 1.7 GHz. The results suggest that for the west part of the large relic some of the Faraday rotation is caused by the intracluster medium and not only due to galactic foregrounds. We also carried out a detailed spectral analysis of this radio relic and created radio color-color diagrams. We find (i) an injection spectral index of -0.6 to -0.7; (ii) steepening spectral index and increasing spectral curvature in the post-shock region; and (iii) an overall power-law spectrum between 74 MHz and 4.9 GHz with α = -1.10 ± 0.02. Mixing of emission in the beam from regions with different spectral ages is probably the dominant factor that determines the shape of the radio spectra. Changes in the magnetic field, total electron content, or adiabatic gains/losses do not play a major role. A model in which particles are (re)accelerated in a

  11. Understanding the physical processes driving galaxy evolution in clusters : a case study of two z~0.5 galaxy clusters

    NASA Astrophysics Data System (ADS)

    Moran, Sean M.

    for Cl 0024 early types. Near the Virial radius of Cl 0024, we observe a number of compact, intermediate-mass ellipticals undergoing a burst of star formation or weak AGN activity, indicated by strong [O II] emission; their locations may mark the minimum radius at which merging is effective in each cluster.While E+S0 galaxies do prove to be sensitive indicators of environmental interaction, it is the spiral galaxies that, of course, host the bulk of star formation within and around these clusters. We therefore probe for kinematic disturbances in spiral disks by measuring resolved rotation curves from optical emission lines, and constructing the Tully-Fisher relation for spirals across Cl 0024 and MS 0451. We find that the cluster Tully-Fisher relation exhibits significantly higher scatter than the field relation. In probing for the origin of this difference, we find that the central mass densities of star-forming spirals exhibit a sharp break near the cluster Virial radius, with spirals in the cluster outskirts exhibiting significantly lower densities. We argue that these results considered together demonstrate that cluster spirals are kinematically disturbed by their environment, likely due to galaxy-galaxy interactions (harassment).We then discuss our most powerful method of tracking galaxy evolution across Cl 0024 and MS 0451: identifying and studying "transition galaxies"-galaxies whose stellar populations or dynamical states indicate a recent or ongoing change in morphology or star formation rate. Such galaxies are often revealed by star formation histories that seem to be at odds with the galaxy morphologies: for example, spiral galaxies with no signs of star formation, or elliptical galaxies that do show signs of star formation.We identify and study one such class of objects, the "passive spirals" in Cl 0024. These objects exhibit no emission lines in their spectra, suggesting a lack of star formation, yet are surprisingly detected in the UV, revealing the

  12. EVIDENCE FOR A CONSTANT IMF IN EARLY-TYPE GALAXIES BASED ON THEIR X-RAY BINARY POPULATIONS

    NASA Astrophysics Data System (ADS)

    Zepf, Stephen E.; Maccarone, T. J.; Kundu, A.; Gonzalez, A. H.; Lehmer, B.; Maraston, C.

    2014-01-01

    A number of recent studies have proposed that the stellar initial mass function (IMF) of early type galaxies varies systematically as a function of galaxy mass, with higher mass galaxies having steeper IMFs. These steeper IMFs have more low-mass stars relative to the number of high mass stars, and therefore naturally result in proportionally fewer neutron stars and black holes. In this paper, we specifically predict the variation in the number of black holes and neutron stars in early type galaxies based on the IMF variation required to reproduce the observed mass-to-light ratio trends with galaxy mass. We then test whether such variations are observed by studying the field low-mass X-ray binary populations (LMXBs) of nearby early-type galaxies. These binaries are field neutron stars or black holes accreting from a low-mass donor star. We specifically compare the number of field LMXBs per K-band light in a well-studied sample of elliptical galaxies, and use this result to distinguish between an invariant IMF and one that is Kroupa/Chabrier-like at low masses and steeper at high masses. We discuss how these observations constrain the possible forms of the IMF variations and how future Chandra observations can enable sharper tests of the IMF.

  13. Prevalence of galaxy-galaxy interactions in AGN hosts

    NASA Astrophysics Data System (ADS)

    Lim, Jeremy; Kuo, Cheng-Yu; Tang, Ya-Wen; Greene, Jenny; Ho, Paul T. P.

    2004-11-01

    Studies in optical starlight have failed to reach a consensus on the importance of either galaxy interactions, bars, or nuclear spirals in triggering luminous active galactic nuclei (AGNs). Here, we present the first systematic imaging study of Seyfert (disk) galaxies in the 21-cm line of neutral atomic hydrogen (HI) gas. HI is the most sensitive and enduring tracer of galaxy interactions, and can reveal tidal features not otherwise visible in optical starlight. Our sample comprises all twenty-eight galaxies in the Véron-Cetty & Véron (1998) catalog with nuclear magnitudes -19 ≥ MB > -23 (including Seyfert, LINER, and HII galaxies) at 0.015 ≤ z ≤ 0.017 in the northern hemisphere, and a matched control sample of twenty-seven inactive galaxies at z≈0.008. We have detected nearly all the galaxies observed, and find a much higher incidence of tidal interactions -- usually not seen in optical starlight -- among the Seyfert galaxies by comparison with the matched control sample. Those Seyferts with uncertain or no clear tidal features show disturbed HI morphologies and/or kinematics, as well as HI companion galaxies, more frequently than the control sample. Our study suggests that the undisturbed optical appearence of active galaxies may be deceptive, and imply that galaxy-galaxy interactions trigger a significant fraction luminous AGNs at low redshifts. The majority of the Seyfert galaxies in our sample appear to be at a relatively early stage of an encounter rather than late in a merger.

  14. Evidence for a constant initial mass function in early-type galaxies based on their X-ray binary populations

    SciTech Connect

    Peacock, Mark B.; Zepf, Stephen E.; Maccarone, Thomas J.; Kundu, Arunav; Gonzalez, Anthony H.; Lehmer, Bret D.; Maraston, Claudia

    2014-04-01

    A number of recent studies have proposed that the stellar initial mass function (IMF) of early type galaxies varies systematically as a function of galaxy mass, with higher mass galaxies having bottom-heavy IMFs. These bottom-heavy IMFs have more low-mass stars relative to the number of high mass stars, and therefore naturally result in proportionally fewer neutron stars (NSs) and black holes (BHs). In this paper, we specifically predict the variation in the number of BHs and NSs based on the power-law IMF variation required to reproduce the observed mass-to-light ratio trends with galaxy mass. We then test whether such variations are observed by studying the field low-mass X-ray binary (LMXB) populations of nearby early-type galaxies. In these binaries, an NS or BH accretes matter from a low-mass donor star. Their number is therefore expected to scale with the number of BHs and NSs present in a galaxy. We find that the number of LMXBs per K-band light is similar among the galaxies in our sample. These data therefore demonstrate the uniformity of the slope of the IMF from massive stars down to those now dominating the K-band light and are consistent with an invariant IMF. Our results are inconsistent with an IMF which varies from a Kroupa/Chabrier like IMF for low-mass galaxies to a steep power-law IMF (with slope x = 2.8) for high mass galaxies. We discuss how these observations constrain the possible forms of the IMF variations and how future Chandra observations can enable sharper tests of the IMF.

  15. The Unexpected Past of a Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    1996-08-01

    in this way effectively `eats' the smaller one. Thus the Milky Way may contain the remains of many smaller galaxies it has met and consumed in the past. A natural consequence of this theory is that the Milky Way halo may at least partially consist of stars which originally belonged to these smaller galaxies. However, it is also possible that some of the halo stars formed during the early collapse of the gas cloud from which the Milky Way formed. Like the Milky Way, the two nearest, large spiral galaxies (the Andromeda nebula and M33 in the neighbouring Triangulum constellation) are also surrounded by halos of old stars. Contrarily, investigations of the smaller galaxies in the Local Group have until now not shown that they possess such halos. These dwarf galaxies greatly outnumber the large spiral galaxies - to date about two dozen are known - and they are considered to be the last survivors of the earlier cannibalism phase. The nearest are the well-known Magellanic Clouds, about 170,000 (Large Cloud) and 250,000 light years distant (Small Cloud). They can be seen with the unaided eye from the Southern hemisphere. Recent studies indicate that they orbit the Milky Way and that they may eventually fall prey to our galaxy in a future round of cannibalism. So far, no evidence has been found of an old halo around the Magellanic Clouds. This does not necessarily imply that all dwarf galaxies must likewise lack halos: it is also possible that the halos of the Magellanic Clouds were stripped away when they came too close to the Milky Way sometime in the past. The isolated WLM dwarf galaxy Down in the southern sky, in the constellation of Cetus (the Whale or the Sea Monster), lies a relative faint and distant, small galaxy which astronomers normally refer to as the WLM dwarf galaxy . It was first seen in 1909 by the famous astrophotographer Max Wolf on photographic plates obtained at the Heidelberg Observatory (Germany), but it was only in 1926 that its true nature was

  16. Sleep Disturbances in Mood Disorders.

    PubMed

    Rumble, Meredith E; White, Kaitlin Hanley; Benca, Ruth M

    2015-12-01

    The article provides an overview of common and differentiating self-reported and objective sleep disturbances seen in mood-disordered populations. The importance of considering sleep disturbances in the context of mood disorders is emphasized, because a large body of evidence supports the notion that sleep disturbances are a risk factor for onset, exacerbation, and relapse of mood disorders. In addition, potential mechanisms for sleep disturbance in depression, other primary sleep disorders that often occur with mood disorders, effects of antidepressant and mood-stabilizing drugs on sleep, and the adjunctive effect of treating sleep in patients with mood disorders are discussed.

  17. Differences between CO- and calcium triplet-derived velocity dispersions in spiral galaxies: evidence for central star formation?

    NASA Astrophysics Data System (ADS)

    Riffel, Rogemar A.; Ho, Luis C.; Mason, Rachel; Rodríguez-Ardila, Alberto; Martins, Lucimara; Riffel, Rogério; Diaz, Ruben; Colina, Luis; Alonso-Herrero, Almudena; Flohic, Helene; Gonzalez Martin, Omaira; Lira, Paulina; McDermid, Richard; Ramos Almeida, Cristina; Schiavon, Ricardo; Thanjavur, Karun; Ruschel-Dutra, Daniel; Winge, Claudia; Perlman, Eric

    2015-01-01

    We examine the stellar velocity dispersions (σ) of a sample of 48 galaxies, 35 of which are spirals, from the Palomar nearby galaxy survey. It is known that for ultra-luminous infrared galaxies (ULIRGs) and merger remnants, the σ derived from the near-infrared CO band heads is smaller than that measured from optical lines, while no discrepancy between these measurements is found for early-type galaxies. No such studies are available for spiral galaxies - the subject of this paper. We used cross-dispersed spectroscopic data obtained with the Gemini Near-Infrared Spectrograph, with spectral coverage from 0.85 to 2.5 μm, to obtain σ measurements from the 2.29 μm CO band heads (σCO) and the 0.85 μm calcium triplet (σCaT). For the spiral galaxies in the sample, we found that σCO is smaller than σCaT, with a mean fractional difference of 14.3 per cent. The best fit to the data is given by σopt = (46.0 ± 18.1) + (0.85 ± 0.12)σCO. This `σ-discrepancy' may be related to the presence of warm dust, as suggested by a slight correlation between the discrepancy and the infrared luminosity. This is consistent with studies that have found no σ-discrepancy in dust-poor early-type galaxies, and a much larger discrepancy in dusty merger remnants and ULIRGs. That σCO is lower than σopt may also indicate the presence of a dynamically cold stellar population component. This would agree with the spatial correspondence between low-σCO and young/intermediate-age stellar populations that has been observed in spatially resolved spectroscopy of a handful of galaxies.

  18. Evidence of low-latitude daytime large-scale traveling ionospheric disturbances observed by high-frequency multistatic backscatter sounding system during a geomagnetically quiet period

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Zhao, Zhengyu; Yang, Guobin; Chen, Gang; Hu, Yaogai; Zhang, Yuannong

    2012-06-01

    Observations from the high-frequency multistatic backscatter sounding radars on a geomagnetically quiet day (minimum Dst = -14 nT) captured the anti-equatorward propagation of daytime large-scale traveling ionospheric disturbance (LSTID) at the low-latitude regions. The observed LSTID was characterized approximately by a meridional propagation speed of 347 ± 78 m/s and azimuthal angle of -4.7 ± 27.6° (counterclockwise from north), with a period of 76 min and a wavelength of 1583 ± 354 km by means of maximum entropy cross-spectral analysis. Vertical phase velocity was also evaluated to be <˜42 m/s through the Doppler measurements. These results provide evidence that the low-latitude ionosphere can undergo large-scale perturbations even under geomagnetically quiet conditions. We suggest that this observed LSTID could be due to the secondary gravity waves from thermospheric body forces created from the dissipation of primary gravity waves from deep tropospheric convection.

  19. Evidence for the Presence of a Warping of the Ionizing Gas I-Ayer Derived from H166a Emission Observations in the Outer Galaxy

    NASA Astrophysics Data System (ADS)

    Azcarate, I. N.; Cersosimo, J. C.; Colomb, F. R.

    1990-12-01

    RESUMEN Se presentan resultados de un relevamiento de Ia emisi6n de la ifnea H 1 66a en el rango de longitudes galacticas 2700 < 1 <3000 y para tres latitudes galacticas b = 0.00, b = l0.50. De los mismos, resulta que hay evidencia de un alabeo de Ia capa de gas jonizado en el plano galactico, en las partes exteriores de Ia Galaxia. ABSTRACT Results from an H166a emission survey in the Galactic longitude range 2700 < 1 <3000 and for three Galactic latitudes (b = 0.00, b = 0.50), are presented. From these results, there is evidence for the presence of a warping of the ionized gas layer in the galactic plane, in the outer Galaxy. K words: GALAXY-SThUCTURE - RADIO HNES-

  20. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  1. EVIDENCE THAT GAMMA-RAY BURST 130702A EXPLODED IN A DWARF SATELLITE OF A MASSIVE GALAXY

    SciTech Connect

    Kelly, Patrick L.; Filippenko, Alexei V.; Fox, Ori D.; Zheng Weikang; Clubb, Kelsey I.

    2013-09-20

    GRB 130702A is a nearby long-duration gamma-ray burst (LGRB) discovered by the Fermi satellite whose associated afterglow was detected by the Palomar Transient Factory. Subsequent photometric and spectroscopic monitoring has identified a coincident broad-lined Type Ic supernova (SN), and nebular emission detected near the explosion site is consistent with a redshift of z = 0.145. The SN-GRB exploded at an offset of {approx}7.''6 from the center of an inclined r = 18.1 mag red disk-dominated galaxy, and {approx}0.''6 from the center of a much fainter r = 23 mag object. We obtained Keck-II DEIMOS spectra of the two objects and find a 2{sigma} upper limit on their line-of-sight velocity offset of {approx}<60 km s{sup -1}. If we calculate the inclination angle of the massive red galaxy from its axis ratio and assume that its light is dominated by a very thin disk, the explosion would have a {approx}60 kpc central offset, or {approx}9 times the galaxy's half-light radius. A significant bulge or a thicker disk would imply a higher inclination angle and greater central offset. The substantial offset suggests that the faint source is a separate dwarf galaxy. The star-formation rate of the dwarf galaxy is {approx}0.05 M{sub Sun} yr{sup -1}, and we place an upper limit on its oxygen abundance of 12 + log(O/H) < 8.16 dex. The identification of an LGRB in a dwarf satellite of a massive, metal-rich primary galaxy suggests that recent detections of LGRBs spatially coincident with metal-rich galaxies may be, in some cases, superpositions.

  2. Evidence of suppression of star formation by quasar-driven winds in gas-rich host galaxies at z < 1?

    NASA Astrophysics Data System (ADS)

    Wylezalek, Dominika; Zakamska, Nadia L.

    2016-10-01

    Feedback from active galactic nuclei (AGN) is widely considered to be the main driver in regulating the growth of massive galaxies through heating or driving gas out of the galaxy, preventing further increase in stellar mass. Observational proof for this scenario has, however, been scarce. We have assembled a sample of 132 radio-quiet type-2 and red AGN at 0.1 < z < 1. We measure the kinematics of the AGN-ionized gas, the host galaxies' stellar masses and star formation rates (SFRs) and investigate the relationships between AGN luminosities, specific star formation rates (sSFRs) and outflow strengths W90 - the 90 per cent velocity width of the [O III]λ5007Å line power and a proxy for the AGN-driven outflow speed. Outflow strength is independent of sSFR for AGN selected on their mid-IR luminosity, in agreement with previous work demonstrating that star formation is not sufficient to produce the observed ionized gas outflows which have to be powered by AGN activity. More importantly, we find a negative correlation between W90 and sSFR in the AGN hosts with the highest SFRs, i.e. with the highest gas content, where presumably the coupling of the AGN-driven wind to the gas is strongest. This implies that AGN with strong outflow signatures are hosted in galaxies that are more `quenched' than galaxies with weaker outflow signatures. Despite the galaxies' high SFRs, we demonstrate that the outflows are not star formation driven but indeed due to AGN powering. This observation is consistent with the AGN having a net suppression, `negative' impact, through feedback on the galaxies' star formation history.

  3. Evidence that Gamma-Ray Burst 130702A Exploded in a Dwarf Satellite of a Massive Galaxy

    NASA Astrophysics Data System (ADS)

    Kelly, Patrick L.; Filippenko, Alexei V.; Fox, Ori D.; Zheng, Weikang; Clubb, Kelsey I.

    2013-09-01

    GRB 130702A is a nearby long-duration gamma-ray burst (LGRB) discovered by the Fermi satellite whose associated afterglow was detected by the Palomar Transient Factory. Subsequent photometric and spectroscopic monitoring has identified a coincident broad-lined Type Ic supernova (SN), and nebular emission detected near the explosion site is consistent with a redshift of z = 0.145. The SN-GRB exploded at an offset of ~7.''6 from the center of an inclined r = 18.1 mag red disk-dominated galaxy, and ~0.''6 from the center of a much fainter r = 23 mag object. We obtained Keck-II DEIMOS spectra of the two objects and find a 2σ upper limit on their line-of-sight velocity offset of lsim60 km s-1. If we calculate the inclination angle of the massive red galaxy from its axis ratio and assume that its light is dominated by a very thin disk, the explosion would have a ~60 kpc central offset, or ~9 times the galaxy's half-light radius. A significant bulge or a thicker disk would imply a higher inclination angle and greater central offset. The substantial offset suggests that the faint source is a separate dwarf galaxy. The star-formation rate of the dwarf galaxy is ~0.05 M ⊙ yr-1, and we place an upper limit on its oxygen abundance of 12 + log(O/H) < 8.16 dex. The identification of an LGRB in a dwarf satellite of a massive, metal-rich primary galaxy suggests that recent detections of LGRBs spatially coincident with metal-rich galaxies may be, in some cases, superpositions.

  4. EVIDENCE FOR INTERMEDIATE-AGE STELLAR POPULATIONS IN EARLY-TYPE GALAXIES FROM K-BAND SPECTROSCOPY

    SciTech Connect

    Marmol-Queralto, E.; Cardiel, N.; Gorgas, J.; Sanchez-Blazquez, P.; Cenarro, A. J.; Vazdekis, A.; Kuntschner, H.; Silva, D. R.

    2009-11-10

    The study of stellar populations in early-type galaxies in different environments is a powerful tool for constraining their star formation histories. This study has been traditionally restricted to the optical range, where dwarfs around the turn-off and stars at the base of the red giant branch dominate the integrated light at all ages. The near-infrared spectral range is especially interesting since in the presence of an intermediate-age population, asymptotic giant branch stars are the main contributors. In this Letter, we measure the near-infrared indices Na I and D {sub CO} for a sample of 12 early-type galaxies in low-density environments and compare them with the Fornax galaxy sample presented by Silva et al.. The analysis of these indices in combination with Lick/IDS indices in the optical range reveals that (1) the Na I index is a metallicity indicator as good as C4668 in the optical range, and (2) D {sub CO} is a tracer of intermediate-age stellar populations. We find that low-mass galaxies in low-density environments show higher Na I and D {sub CO} than those located in the Fornax cluster, which points toward a late stage of star formation for the galaxies in less dense environments, in agreement with results from other studies using independent methods.

  5. The galaxy population of Abell 1367: the stellar mass-metallicity relation

    NASA Astrophysics Data System (ADS)

    Mouhcine, M.; Kriwattanawong, W.; James, P. A.

    2011-04-01

    Using wide baseline broad-band photometry, we analyse the stellar population properties of a sample of 72 galaxies, spanning a wide range of stellar masses and morphological types, in the nearby spiral-rich and dynamically young galaxy cluster Abell 1367. The sample galaxies are distributed from the cluster centre out to approximately half the cluster Abell radius. The optical/near-infrared colours are compared with simple stellar population synthesis models from which the luminosity-weighted stellar population ages and metallicities are determined. The locus of the colours of elliptical galaxies traces a sequence of varying metallicity at a narrow range of luminosity-weighted stellar ages. Lenticular galaxies in the red sequence, however, exhibit a substantial spread of luminosity-weighted stellar metallicities and ages. For red-sequence lenticular galaxies and blue cloud galaxies, low-mass galaxies tend to be on average dominated by stellar populations of younger luminosity-weighted ages. Sample galaxies exhibit a strong correlation between integrated stellar mass and luminosity-weighted stellar metallicity. Galaxies with signs of morphological disturbance and ongoing star formation activity, tend to be underabundant with respect to passive galaxies in the red sequence of comparable stellar masses. We argue that this could be due to tidally driven gas flows towards the star-forming regions, carrying less enriched gas and diluting the pre-existing gas to produce younger stellar populations with lower metallicities than would be obtained prior to the interaction. Finally, we find no statistically significant evidence for changes in the luminosity-weighted ages and metallicities for either red-sequence or blue-cloud galaxies, at fixed stellar mass, with location within the cluster. We dedicate this work to the memory of our friend and colleague C. Moss who died suddenly recently.

  6. Evidence for particle re-acceleration in the radio relic in the galaxy cluster PLCKG287.0+32.9

    SciTech Connect

    Bonafede, A.; Brüggen, M.; Intema, H. T.; Girardi, M.; Nonino, M.; Kantharia, N.; Van Weeren, R. J.; Röttgering, H. J. A.

    2014-04-10

    Radio relics are diffuse radio sources observed in galaxy clusters, probably produced by shock acceleration during cluster-cluster mergers. Their large size, of the order of 1 Mpc, indicates that the emitting electrons need to be (re)accelerated locally. The usually invoked diffusive shock acceleration models have been challenged by recent observations and theory. We report the discovery of complex radio emission in the Galaxy cluster PLCKG287.0+32.9, which hosts two relics, a radio halo, and several radio filamentary emission. Optical observations suggest that the cluster is elongated, likely along an intergalactic filament, and displays a significant amount of substructure. The peculiar features of this radio relic are that (1) it appears to be connected to the lobes of a radio galaxy and (2) the radio spectrum steepens on either side of the radio relic. We discuss the origins of these features in the context of particle re-acceleration.

  7. Galaxy interactions and star formation: Results of a survey of global H-alpha emission in spiral galaxies in 8 clusters

    NASA Technical Reports Server (NTRS)

    Moss, C.

    1990-01-01

    Kennicutt and Kent (1983) have shown that the global H alpha emission from a spiral galaxy is an indicator of the formation rate of massive stars. Moss, Whittle and Irwin (1988) have surveyed two clusters (Abell 347 and 1367) for galaxies with H alpha emission using a high dispersion objective prism technique. The purpose of the survey is to investigate environmental effects on star formation in spiral galaxies, and in particular to ascertain whether star formation is enhanced in cluster spirals. Approximately 20 percent of CGCG galaxies were detected in emission. Two plates of excellent quality were obtained for each of the two clusters, and galaxies were only identified to have emission if this was detected on both plates of a plate pair. In this way, plate flaws and other spurious identifications of emission could be rejected, and weak emission confirmed. The results of this survey have been discussed by Moss (1987). The detected galaxies are of types SO-a and later. The frequency with which galaxies are detected in emission increases towards later morphological type as expected (cf. Kennicutt and Kent 1983). There is no evidence of any dependence of the frequency of detected emission on the absolute magnitude of the galaxy (cf. Moss and Whittle 1990), but there is a strong correlation between a disturbed morphological appearance of the galaxy and the detection of emission. Furthermore it is found that the emission is more centrally concentrated in those galaxies which show a disturbed morphology. It may be noted that the objective prism plate gives a spectrum of a 400 A region around rest wavelength H alpha, but superposed on this is the H alpha emission from the galaxy which, because the light is essentially monochromatic, results in a true two-dimensional image of the H alpha distribution. The visual appearance of the emission on the prism plates was classified according to its diffuseness on a 5 point scale (very diffuse, diffuse, intermediate, compact, and

  8. Evidence for Wide-spread Active Galactic Nucleus-driven Outflows in the Most Massive z ~ 1-2 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Genzel, R.; Förster Schreiber, N. M.; Rosario, D.; Lang, P.; Lutz, D.; Wisnioski, E.; Wuyts, E.; Wuyts, S.; Bandara, K.; Bender, R.; Berta, S.; Kurk, J.; Mendel, J. T.; Tacconi, L. J.; Wilman, D.; Beifiori, A.; Brammer, G.; Burkert, A.; Buschkamp, P.; Chan, J.; Carollo, C. M.; Davies, R.; Eisenhauer, F.; Fabricius, M.; Fossati, M.; Kriek, M.; Kulkarni, S.; Lilly, S. J.; Mancini, C.; Momcheva, I.; Naab, T.; Nelson, E. J.; Renzini, A.; Saglia, R.; Sharples, R. M.; Sternberg, A.; Tacchella, S.; van Dokkum, P.

    2014-11-01

    In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M */M ⊙) >= 10.9) z ~ 1-3 star-forming galaxies by increasing the sample size by a factor of six (to 44 galaxies above log(M */M ⊙) >= 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS3Dspectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Hα, [N II], and [S II] lines ~450-5300 km s-1), with large [N II]/Hα ratios, above log(M */M ⊙) ~ 10.9, with about two-thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z ~ 1 and ~2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGNs), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation. Based on observations obtained at the Very Large Telescope (VLT) of the European Southern Observatory (ESO), Paranal, Chile (ESO program IDs 073.B-9018, 074.A-9011, 075.A-0466, 076.A-0527, 078.A-0660, 079.A-0341, 080.A-0330, 080.A-0339, 080.A-0635, 081.A-0672, 082.A-0396, 183.A-0781, 087.A-0081, 088.A-0202, 088.A-0209, 091.A-0126, 092.A-0082, 092.A-0091, 093.A-0079). Also based on observations at the Large Binocular Telescope (LBT) on Mt. Graham in Arizona.

  9. OPTICAL LINE EMISSION IN BRIGHTEST CLUSTER GALAXIES AT 0 < z < 0.6: EVIDENCE FOR A LACK OF STRONG COOL CORES 3.5 Gyr AGO?

    SciTech Connect

    McDonald, Michael

    2011-12-15

    In recent years the number of known galaxy clusters beyond z {approx}> 0.2 has increased drastically with the release of multiple catalogs containing >30,000 optically detected galaxy clusters over the range 0 < z < 0.6. Combining these catalogs with the availability of optical spectroscopy of the brightest cluster galaxy (BCG) from the Sloan Digital Sky Survey allows for the evolution of optical emission-line nebulae in cluster cores to be quantified. For the first time, the continuous evolution of optical line emission in BCGs over the range 0 < z < 0.6 is determined. A minimum in the fraction of BCGs with optical line emission is found at z {approx} 0.3, suggesting that complex, filamentary emission in systems such as Perseus A is a recent phenomenon. Evidence for an upturn in the number of strongly emitting systems is reported beyond z > 0.3, hinting at an earlier epoch of strong cooling. We compare the evolution of emission-line nebulae to the X-ray-derived cool core (CC) fraction from the literature over the same redshift range and find overall agreement, with the exception that an upturn in the strong CC fraction is not observed at z > 0.3. The overall agreement between the evolution of CCs and optical line emission at low redshift suggests that emission-line surveys of galaxy clusters may provide an efficient method of indirectly probing the evolution of CCs and thus provide insights into the balance of heating and cooling processes at early cosmic times.

  10. Backwards Spiral Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Astronomers using NASA's Hubble Space Telescope have found a spiral galaxy that may rotate in the opposite direction from what was expected.

    A picture of the oddball galaxy is available at http://heritage.stsci.edu or http://oposite.stsci.edu/pubinfo/pr/2002/03 or http://www.jpl.nasa.gov/images/wfpc . It was taken in May 2001 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    The picture showed which side of galaxy NGC 4622 is closer to Earth; that information helped astronomers determine that the galaxy may be spinning clockwise. The image shows NGC 4622 and its outer pair of winding arms full of new stars, shown in blue.

    Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise.

    NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. Astronomers suspect this oddity was caused by the interaction of NGC 4622 with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a smaller companion galaxy.

    Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 lies 111 million light-years away in the direction of the constellation Centaurus.

    The science team, consisting of Drs. Ron Buta and Gene Byrd from the University of Alabama, Tuscaloosa, and Tarsh Freeman of Bevill State

  11. Evidence for the inside-out growth of the stellar mass distribution in galaxy clusters since z ~ 1

    NASA Astrophysics Data System (ADS)

    van der Burg, Remco F. J.; Hoekstra, Henk; Muzzin, Adam; Sifón, Cristóbal; Balogh, Michael L.; McGee, Sean L.

    2015-05-01

    We study the radial number density and stellar mass density distributions of satellite galaxies in a sample of 60 massive clusters at 0.04 galaxies, we use deep ugri-band imaging to estimate photometric redshifts and stellar masses, and then statistically subtract fore- and background sources using data from the COSMOS survey. We measure the galaxy number density and stellar mass density distributions in logarithmically spaced bins over 2 orders of magnitude in radial distance from the BCGs. For projected distances in the range 0.1 galaxies of about 1011M⊙ per cluster, compared to these NFW profiles. We do obtain good fits to generalised NFW profiles with free inner slopes and to Einasto profiles. To examine how clusters assemble their stellar mass component over cosmic time, we compare this local sample to the GCLASS cluster sample at z ~ 1, which represents the approximate progenitor sample of the low-z clusters. This allows for a direct comparison, which suggests that the central parts (R< 0.4 Mpc) of the stellar mass distributions of satellites in local galaxy clusters are already in place at z ~ 1, and contain sufficient excess material for further BCG growth. Evolving towards z = 0, clusters appear to assemble their stellar mass primarily onto the outskirts, making them grow in an inside-out fashion. Appendix A is available in electronic form at http://www.aanda.org

  12. Radial Trends in IMF-sensitive Absorption Features in Two Early-type Galaxies: Evidence for Abundance-driven Gradients

    NASA Astrophysics Data System (ADS)

    McConnell, Nicholas J.; Lu, Jessica R.; Mann, Andrew W.

    2016-04-01

    Samples of early-type galaxies show a correlation between stellar velocity dispersion and the stellar initial mass function (IMF) as inferred from gravity-sensitive absorption lines in the galaxies’ central regions. To search for spatial variations in the IMF, we have observed two early-type galaxies with Keck/LRIS and measured radial gradients in the strengths of absorption features from 4000-5500 Å and 8000-10000 Å. We present spatially resolved measurements of the dwarf-sensitive spectral indices {Na} {{I}} (8190 Å) and Wing-Ford {{FeH}} (9915 Å), as well as indices for species of H, C2, CN, Mg, Ca, {{TiO}}, and Fe. Our measurements show a metallicity gradient in both objects, and Mg/Fe consistent with a shallow gradient in α-enhancement, matching widely observed trends for massive early-type galaxies. The {Na} {{I}} index and the CN1 index at 4160 Å exhibit significantly steeper gradients, with a break at r˜ 0.1 {r}{{eff}} (r˜ 300 pc). Inside this radius, {Na} {{I}} strength increases sharply toward the galaxy center, consistent with a rapid central rise in [Na/Fe]. In contrast, the ratio of the {{FeH}} to Fe index strength decreases toward the galaxy center. This behavior cannot be reproduced by a steepening IMF inside of 0.1 {r}{{eff}} if the IMF is a single power law. While gradients in the mass function above ˜ 0.4 {M}⊙ may occur, exceptional care is required to disentangle these IMF variations from the extreme variations in individual element abundances near the galaxies’ centers.

  13. Increased tolerance to humans among disturbed wildlife.

    PubMed

    Samia, Diogo S M; Nakagawa, Shinichi; Nomura, Fausto; Rangel, Thiago F; Blumstein, Daniel T

    2015-01-01

    Human disturbance drives the decline of many species, both directly and indirectly. Nonetheless, some species do particularly well around humans. One mechanism that may explain coexistence is the degree to which a species tolerates human disturbance. Here we provide a comprehensive meta-analysis of birds, mammals and lizards to investigate species tolerance of human disturbance and explore the drivers of this tolerance in birds. We find that, overall, disturbed populations of the three major taxa are more tolerant of human disturbance than less disturbed populations. The best predictors of the direction and magnitude of bird tolerance of human disturbance are the type of disturbed area (urbanized birds are more tolerant than rural or suburban populations) and body mass (large birds are more tolerant than small birds). By identifying specific features associated with tolerance, these results guide evidence-based conservation strategies to predict and manage the impacts of increasing human disturbance on birds. PMID:26568451

  14. Increased tolerance to humans among disturbed wildlife

    PubMed Central

    Samia, Diogo S. M.; Nakagawa, Shinichi; Nomura, Fausto; Rangel, Thiago F.; Blumstein, Daniel T.

    2015-01-01

    Human disturbance drives the decline of many species, both directly and indirectly. Nonetheless, some species do particularly well around humans. One mechanism that may explain coexistence is the degree to which a species tolerates human disturbance. Here we provide a comprehensive meta-analysis of birds, mammals and lizards to investigate species tolerance of human disturbance and explore the drivers of this tolerance in birds. We find that, overall, disturbed populations of the three major taxa are more tolerant of human disturbance than less disturbed populations. The best predictors of the direction and magnitude of bird tolerance of human disturbance are the type of disturbed area (urbanized birds are more tolerant than rural or suburban populations) and body mass (large birds are more tolerant than small birds). By identifying specific features associated with tolerance, these results guide evidence-based conservation strategies to predict and manage the impacts of increasing human disturbance on birds. PMID:26568451

  15. Increased tolerance to humans among disturbed wildlife.

    PubMed

    Samia, Diogo S M; Nakagawa, Shinichi; Nomura, Fausto; Rangel, Thiago F; Blumstein, Daniel T

    2015-01-01

    Human disturbance drives the decline of many species, both directly and indirectly. Nonetheless, some species do particularly well around humans. One mechanism that may explain coexistence is the degree to which a species tolerates human disturbance. Here we provide a comprehensive meta-analysis of birds, mammals and lizards to investigate species tolerance of human disturbance and explore the drivers of this tolerance in birds. We find that, overall, disturbed populations of the three major taxa are more tolerant of human disturbance than less disturbed populations. The best predictors of the direction and magnitude of bird tolerance of human disturbance are the type of disturbed area (urbanized birds are more tolerant than rural or suburban populations) and body mass (large birds are more tolerant than small birds). By identifying specific features associated with tolerance, these results guide evidence-based conservation strategies to predict and manage the impacts of increasing human disturbance on birds.

  16. Geometrical evidence for dark matter: X-ray constraints on the mass of the elliptical galaxy NGC 720

    NASA Technical Reports Server (NTRS)

    Buote, David A.; Canizares, Claude R.

    1994-01-01

    We describe (1) a new test for dark matter and alternate theories of gravitation based on the relative geometries of the X-ray and optical surface brightness distributions and an assumed form for the potential, of the optical light, (2) a technique to measure the shapes of the total gravitating matter and dark matter of an ellipsoidal system which is insensitive to the precise value of the temperature of the gas and to modest temperature gradients, and (3) a new method to determine the ratio of dark mass to stellar mass that is dependent on the functional forms for the visible star, gas and dark matter distributions, but independent of the distance to the galaxy or the gas temperature. We apply these techniques to X-ray data from the ROSAT Position Sensitive Proportional Counter (PSPC) of the optically flattened elliptical galaxy NGC 720; the optical isophotes have ellipticity epsilon approximately 0.40 extending out to approximately 120 sec. The X-ray isophotes are significantly elongated, epsilon = 0.20-0.30 for semimajor axis a approximately 100 sec. The major axes of the optical and X-ray isophotes are misaligned by approximately 30 deg +/- 15 deg. Spectral analysis of the X-ray data reveals no evidence of temperature gradients or anisotropies and demonstrates that a single-temperature plasma (T approximately 0.6 keV) having subsolar heavy element abundances and a two-temperature model having solar abundances describe the spectrum equally well. Considering only the relative geometries of the X-ray and optical surface brightness distributions and an assumed functional form for the potential of the optical light, we conclude that matter distributed like the optical light cannot produce the observed ellipticities of the X-ray isophotes, independent of the gas pressure, the gas temperature, and the value of the stellar mass; this comparison assumes a state of quasi-hydrostatic equilibrium so that the three-dimensional surfaces of the gas emissivity trace the three

  17. ALFALFA Hα Reveals How Galaxies Use their HI Fuel

    NASA Astrophysics Data System (ADS)

    Jaskot, Anne; Oey, Sally; Salzer, John; Van Sistine, Angela; Bell, Eric; Haynes, Martha

    2015-08-01

    Atomic hydrogen traces the raw material from which molecular clouds and stars form. With the ALFALFA Hα survey, a statistically complete subset of the ALFALFA survey, we examine the processes that affect galaxies’ abilities to access and consume their HI gas. On galaxy-wide scales, HI gas fractions correlate only weakly with instantaneous specific star formation rates (sSFRs) but tightly with galaxy color. We show that a connection between dust and HI content, arising from the fundamental mass-metallicity-HI relation, leads to this tight color correlation. We find that disk galaxies follow a relation between stellar surface density and HI depletion time, consistent with a scenario in which higher mid-plane pressure leads to more efficient molecular cloud formation from HI. In contrast, spheroids show no such trend. Starbursts, identified by Hα equivalent width, do not show enhanced HI gas fractions relative to similar mass non-starburst galaxies. The starbursts’ shorter HI depletion times indicate more efficient consumption of HI, and galaxy interactions drive this enhanced star formation efficiency in several starbursts. Interestingly, the most disturbed starbursts show greater enhancements in HI gas fraction, which may indicate an excess of HI at early merger stages. At low galaxy stellar masses, the triggering mechanism for starbursts is less clear; the high scatter in efficiency and sSFR among low-mass galaxies may result from periodic bursts. We find no evidence for depleted HI reservoirs in starbursts, which suggests that galaxies may maintain sufficient HI to fuel multiple starburst episodes.

  18. Evidences that human disturbance simplify the ant fauna associated a Stachytarpheta glabra Cham. (Verbenaceae) compromising the benefits of ant-plant mutualism.

    PubMed

    Barbosa, B C; Fagundes, R; Silva, L F; Tofoli, J F V; Santos, A M; Imai, B Y P; Gomes, G G; Hermidorff, M M; Ribeiro, S P

    2015-01-01

    Interaction among species, like ants and plants through extrafloral nectaries (EFNs), are important components of ecological communities' evolution. However, the effect of human disturbance on such specific interactions and its ecological consequences is poorly understood. This study evaluated the outcomes of mutualism between ants and the EFN-bearing plant Stachytarpheta glabra under anthropogenic disturbance. We compared the arthropod fauna composition between two groups of twenty plant individuals, one in an area disturbed by human activities and one in a preserved area. We also check the plant investment in herbivory defense and the consequential leaf damage by herbivore. Our results indicate that such disturbances cause simplification of the associated fauna and lack of proper ant mutualist. This led to four times more herbivory on plants of disturbed areas, despite the equal amount of EFN and ant visitors and low abundance of herbivores. The high pressure of herbivory may difficult the re-establishment of S. glabra, an important pioneer species in ferruginous fields, therefore it may affect resilience of this fragile ecological community. PMID:25945621

  19. The effects of landscape-level disturbance on the composition of Minnesota caddisfly (Insecta: Trichoptera) trophic functional groups: evidence for ecosystem homogenization.

    PubMed

    Houghton, David C

    2007-12-01

    Over 300,000 caddisfly specimens representing 249 species were collected from nearly 250 sites throughout Minnesota during 2000 and 2001 to determine the effects of human disturbance on the composition of caddisfly trophic functional groups at the landscape level. Canonical correspondence analysis determined that stream width was the most important variable influencing functional group composition in regions of the state with relatively low disturbance, and that differences in the caddisfly fauna between sizes of streams generally followed trends predicted by the river continuum concept. In regions of the state with moderate disturbance, both stream width and the percentage of disturbed habitat upstream of a site were important variables influencing functional group composition. In highly disturbed regions, no variables corresponded to changes in the composition of caddisfly functional groups. Instead, ecosystems were homogeneous: fine-particle filtering collectors dominated in all sizes of streams. The observed aquatic ecosystem homogenization is attributed mostly to input of fine-particle organic and inorganic sediment from extensive agriculture.

  20. Fantastic Four Galaxies with Planet (Artist Concept)

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This artist's concept shows what the night sky might look like from a hypothetical planet around a star tossed out of an ongoing four-way collision between big galaxies (yellow blobs). NASA's Spitzer Space Telescope spotted this 'quadruple merger' of galaxies within a larger cluster of galaxies located nearly 5 billion light-years away.

    Though the galaxies appear intact, gravitational disturbances have caused them to stretch and twist, flinging billions of stars into space -- nearly three times as many stars as are in our Milky Way galaxy. The tossed stars are visible in the large plume emanating from the central, largest galaxy. If any of these stars have planets, their night skies would be filled with the monstrous merger, along with other galaxies in the cluster (smaller, bluish blobs).

    This cosmic smash-up is the largest known merger between galaxies of a similar size. While three of the galaxies are about the size of our Milky Way galaxy, the fourth (center of image) is three times as big. All four of the galaxies, as well as most other galaxies in the huge cluster, are blob-shaped ellipticals instead of spirals like the Milky Way.

    Ultimately, in about one hundred million years or so, the four galaxies E will unite into one. About half of the stars kicked out during the merger will fall back and join the new galaxy, making it one of the biggest galaxies in the universe.

  1. THE EVOLUTION OF THE STELLAR MASS FUNCTION OF GALAXIES FROM z = 4.0 AND THE FIRST COMPREHENSIVE ANALYSIS OF ITS UNCERTAINTIES: EVIDENCE FOR MASS-DEPENDENT EVOLUTION

    SciTech Connect

    Marchesini, Danilo; Van Dokkum, Pieter G.; Foerster Schreiber, Natascha M.; Franx, Marijn; Labbe, Ivo; Wuyts, Stijn

    2009-08-20

    We present the evolution of the stellar mass function (SMF) of galaxies from z = 4.0 to z = 1.3 measured from a sample constructed from the deep near-infrared Multi-wavelength Survey by Yale-Chile, the Faint Infrared Extragalactic Survey, and the Great Observatories Origins Deep Survey-Chandra Deep Field South surveys, all having very high-quality optical to mid-infrared data. This sample, unique in that it combines data from surveys with a large range of depths and areas in a self-consistent way, allowed us to (1) minimize the uncertainty due to cosmic variance and empirically quantify its contribution to the total error budget; (2) simultaneously probe the high-mass end and the low-mass end (down to {approx}0.05 times the characteristic stellar mass) of the SMF with good statistics; and (3) empirically derive the redshift-dependent completeness limits in stellar mass. We provide, for the first time, a comprehensive analysis of random and systematic uncertainties affecting the derived SMFs, including the effect of metallicity, extinction law, stellar population synthesis model, and initial mass function. We find that the mass density evolves by a factor of {approx}17{sup +7}{sub -10} since z = 4.0, mostly driven by a change in the normalization {phi}*. If only random errors are taken into account, we find evidence for mass-dependent evolution, with the low-mass end evolving more rapidly than the high-mass end. However, we show that this result is no longer robust when systematic uncertainties due to the SED-modeling assumptions are taken into account. Another significant uncertainty is the contribution to the overall stellar mass density of galaxies below our mass limit; future studies with WFC3 will provide better constraints on the SMF at masses below 10{sup 10} M{sub sun} at z>2. Taking our results at face value, we find that they are in conflict with semianalytic models of galaxy formation. The models predict SMFs that are in general too steep, with too many

  2. [Sleep disturbance in Parkinson's disease].

    PubMed

    Nomura, Takashi; Inoue, Yuichi; Nakashima, Kenji

    2014-01-01

    Many patients with Parkinson's disease (PD) complain about sleep disturbances. These symptoms originate from motor symptoms, nocturnal problems, psychiatric symptoms, and other sleep disorders including Excessive daytime sleepiness (EDS), REM sleep behavior disorder (RBD), Restless legs syndrome (RLS), and Sleep apnea syndrome (SAS). Especially, RBD is paid attention to prodromal symptoms of PD. Also, one third of patients with PD have RBD symptoms. Moreover, RBD is one of aggravating factors of motor symptoms, autonomic dysfunctions, and dementia. Now, the evidence based medicine for sleep disturbances is lack in patients with PD. We need to evaluate various causes of sleep disturbances in detail and deal with individuals.

  3. Near Infrared Observations of a Redshift 5.34 Galaxy: Further Evidence for Significant Dust Absorption in the Early Universe

    NASA Technical Reports Server (NTRS)

    Armus, L.; Matthews, K.; Neugebauer, G.; Soifer, B. T.

    1998-01-01

    In the last several years, the combination of new wavelength dropout discovery techniques coupled with the incredible power of deep imaging of the Hubble Space Telescope and the spectroscopic capabilities of a new generation of large ground-based telescopes, has lead to an astonishing blossoming of the study of galaxies at redshifts of z=2-4, when the Universe was less than 10-20% of its current age.

  4. The red and blue galaxy populations in the GOODS field: evidence for an excess of red dwarfs

    NASA Astrophysics Data System (ADS)

    Salimbeni, S.; Giallongo, E.; Menci, N.; Castellano, M.; Fontana, A.; Grazian, A.; Pentericci, L.; Trevese, D.; Cristiani, S.; Nonino, M.; Vanzella, E.

    2008-01-01

    Aims: We study the evolution of the galaxy population up to z˜ 3 as a function of its colour properties. In particular, luminosity functions and luminosity densities were derived as a function of redshift for the blue/late and red/early populations. Methods: We use data from the GOODS-MUSIC catalogue, which have typical magnitude limits z850≤ 26 and K_s≤ 23.5 for most of the sample. About 8% of the galaxies have spectroscopic redshifts; the remaining have well calibrated photometric redshifts derived from the extremely wide multi-wavelength coverage in 14 bands (from the U band to the Spitzer 8~ μm band). We have derived a catalogue of galaxies complete in the rest-frame B-band, which has been divided into two subsamples according to their rest-frame U-V colour (or derived specific star formation rate) properties. Results: We confirm a bimodality in the U-V colour and specific star formation rate of the galaxy sample up to z˜ 3. This bimodality is used to compute the luminosity functions of the blue/late and red/early subsamples. The luminosity functions of the blue/late and total samples are well represented by steep Schechter functions evolving in luminosity with increasing redshifts. The volume density of the luminosity functions of the red/early populations decreases with increasing redshift. The shape of the red/early luminosity functions shows an excess of faint red dwarfs with respect to the extrapolation of a flat Schechter function and can be represented by the sum of two Schechter functions. Our model for galaxy formation in the hierarchical clustering scenario, which also includes external feedback due to a diffuse UV background, shows a general broad agreement with the luminosity functions of both populations, the larger discrepancies being present at the faint end for the red population. Hints on the nature of the red dwarf population are given on the basis of their stellar mass and spatial distributions.

  5. Sixth Graders' Co-Construction of Explanations of a Disturbance in an Ecosystem: Exploring Relationships between Grouping, Reflective Scaffolding, and Evidence-Based Explanations

    ERIC Educational Resources Information Center

    Kyza, Eleni A.; Constantinou, Costas P.; Spanoudis, George

    2011-01-01

    We report on a study investigating the relationship between cognitive ability grouping, reflective inquiry scaffolding, and students' collaborative explanations of an ecosystem disturbance which took place when a number of flamingo birds died in a salt lake because of nearby intensive human activities. Twenty-six pairs of students from two intact…

  6. The SINS/zC-SINF survey of z ∼ 2 galaxy kinematics: Evidence for gravitational quenching

    SciTech Connect

    Genzel, R.; Förster Schreiber, N. M.; Lang, P.; Tacconi, L. J.; Wuyts, S.; Bandara, K.; Burkert, A.; Buschkamp, P.; Davies, R.; Eisenhauer, F.; Kurk, J.; Lutz, D.; Tacchella, S.; Carollo, C. M.; Lilly, S. J.; Cresci, G.; Hicks, E. K. S.; Mancini, C.; Naab, T.; Newman, S.; and others

    2014-04-10

    As part of the SINS/zC-SINF surveys of high-z galaxy kinematics, we derive the radial distributions of Hα surface brightness, stellar mass surface density, and dynamical mass at ∼2 kpc resolution in 19 z ∼ 2 star-forming disks with deep SINFONI adaptive optics spectroscopy at the ESO Very Large Telescope. From these data we infer the radial distribution of the Toomre Q-parameter for these main-sequence star-forming galaxies (SFGs), covering almost two decades of stellar mass (10{sup 9.6}-10{sup 11.5} M {sub ☉}). In more than half of our SFGs, the Hα distributions cannot be fit by a centrally peaked distribution, such as an exponential, but are better described by a ring, or the combination of a ring and an exponential. At the same time the kinematic data indicate the presence of a mass distribution more centrally concentrated than a single exponential distribution for 5 of the 19 galaxies. The resulting Q-distributions are centrally peaked for all, and significantly exceed unity there for three-quarters of the SFGs. The occurrence of Hα rings and of large nuclear Q-values appears to be more common for the more massive SFGs. While our sample is small and biased to larger SFGs, and there remain uncertainties and caveats, our observations are consistent with a scenario in which cloud fragmentation and global star formation are secularly suppressed in gas-rich high-z disks from the inside out, as the central stellar mass density of the disks grows.

  7. MULTIPLE GALAXY COLLISIONS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Here is a sampling of 15 ultraluminous infrared galaxies viewed by NASA's Hubble Space Telescope. Hubble's sharp vision reveals more complexity within these galaxies, which astronomers are interpreting as evidence of a multiple-galaxy pileup. These images, taken by the Wide Field and Planetary Camera 2, are part of a three-year study of 123 galaxies within 3 billion light-years of Earth. The study was conducted in 1996, 1997, and 1999. False colors were assigned to these photos to enhance fine details within these coalescing galaxies. Credits: NASA, Kirk Borne (Raytheon and NASA Goddard Space Flight Center, Greenbelt, Md.), Luis Colina (Instituto de Fisica de Cantabria, Spain), and Howard Bushouse and Ray Lucas (Space Telescope Science Institute, Baltimore, Md.)

  8. Colliding and merging galaxies.

    PubMed

    Schweizer, F

    1986-01-17

    Aided by advances in computer technology and observations from space, astronomers have begun to unravel the mysteries of galaxy formation and evolution. Galaxies evolve by interacting with their environment and especially with each other. During brief but often fierce galactic encounters, gravitational forces generate strong tides that survive as telltale signatures for billions of years. Because these so-called collisions dissipate orbital energy, galaxies on bound orbits may eventually merge. Collisions and mergers are responsible for a great variety of phenomena, including the triggering of widespread star formation in galaxies and the fueling of nuclear activity in quasars. Evidence is accumulating that not all galaxies formed shortly after the Big Bang. A sizable fraction of them may have formed later, and many are still experiencing significant dynamical evolution. PMID:17769643

  9. SpARCS Brightest Cluster Galaxies: Evidence for significant star formation down to z~0.7

    NASA Astrophysics Data System (ADS)

    Bonaventura, Nina

    2015-08-01

    We present the first stacked Spitzer/Herschel IR broadband SED of the largest and highest-redshift sample of optically selected Brightest Cluster Galaxies (BCGs), from 1014-Msun clusters in the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS). While semi-analytic models of structure formation predict that star formation ceases at very early times in BCGs, leaving them to passively evolve subsequently, the updated models of Tonini et al. (2012) suggest that star formation persists in BCGs to much lower redshifts than originally predicted. To address this tension between various models and gain a better understanding of the mechanisms guiding BCG stellar mass growth since z~2, we identify their dominant source of IR energy output through a comparison of their SEDs to a variety of model templates in the literature, in multiple redshift bins between z = 0.1 and 1.9. We derive estimates of LIR,TOT , SFR and sSFR , M* , Tdust , and various measures of 'starburstiness' (Chary & Elbaz 2011) from the stacked SEDs.From the observed redshift evolution of the SED emerges a picture of a star-forming BCG down to z~0.1, vigorously producing hundreds of solar masses per year at z>~0.7, with high efficiency at z>~1 and mostly between 1 and 10 solar mass at lower redshifts, with a small subset representing extreme sources and likely marking a period of intense merging activity between z = 0.4 and 0.6. We find a significant AGN contribution to the small 24μm-bright subset of the BCG sample down to z~0.4, mostly coexisting with vigorous star formation and indicative of a relatively ineffective AGN feedback mechanism in BCGs.We conclude that the star formation and AGN activity we observe in BCGs down to lower redshifts than expected is due to their unique environment at the centers of galaxy clusters, where they are continuously subjected to galaxy merger events at mid-to-high redshift, and likely cooling flows and the associated AGN response towards lower redshifts

  10. KECK SPECTROSCOPY OF FAINT 3 < z < 8 LYMAN BREAK GALAXIES: EVIDENCE FOR A DECLINING FRACTION OF EMISSION LINE SOURCES IN THE REDSHIFT RANGE 6 < z < 8

    SciTech Connect

    Schenker, Matthew A.; Ellis, Richard S.; Robertson, Brant E.; Stark, Daniel P.; Dunlop, James S.; McLure, Ross J.; Kneib, Jean-Paul; Richard, Johan

    2012-01-10

    Using deep Keck spectroscopy of Lyman break galaxies selected from infrared imaging data taken with the Wide Field Camera 3 on board the Hubble Space Telescope, we present new evidence for a reversal in the redshift-dependent fraction of star-forming galaxies with detectable Lyman alpha (Ly{alpha}) emission in the redshift range 6.3 < z < 8.8. Our earlier surveys with the DEIMOS spectrograph demonstrated a significant increase with redshift in the fraction of line emitting galaxies over the interval 4 < z < 6, particularly for intrinsically faint systems which dominate the luminosity density. Using the longer wavelength sensitivities of Low Resolution Imaging Spectrometer and NIRSPEC, we have targeted 19 Lyman break galaxies selected using recent WFC3/IR data whose photometric redshifts are in the range 6.3 < z < 8.8 and which span a wide range of intrinsic luminosities. Our spectroscopic exposures typically reach a 5{sigma} sensitivity of <50 A for the rest-frame equivalent width (EW) of Ly{alpha} emission. Despite the high fraction of emitters seen only a few hundred million years later, we find only two convincing and one possible line emitter in our more distant sample. Combining with published data on a further seven sources obtained using FORS2 on the ESO Very Large Telescope, and assuming continuity in the trends found at lower redshift, we discuss the significance of this apparent reversal in the redshift-dependent Ly{alpha} fraction in the context of our range in continuum luminosity. Assuming all the targeted sources are at their photometric redshift and our assumptions about the Ly{alpha} EW distribution are correct, we would expect to find so few emitters in less than 1% of the realizations drawn from our lower redshift samples. Our new results provide further support for the suggestion that, at the redshifts now being probed spectroscopically, we are entering the era where the intergalactic medium is partially neutral. With the arrival of more

  11. Molecular gas, stars, and dust in sub-L* star-forming galaxies at z~2: evidence for universal star formation and nonuniversal dust-to-gas ratio

    NASA Astrophysics Data System (ADS)

    Dessauges-Zavadsky, Miroslava; Schaerer, Daniel; Combes, Francoise; Egami, Eiichi; Swinbank, A. Mark; Richard, Johan; Sklias, Panos; Rawle, Tim D.

    2015-08-01

    Only recently have CO measurements become possible in main sequence star-forming galaxies (SFGs) at z=1-3, but are still biased toward high star formation rates (SFR) and stellar masses (Ms), because of instrumental sensitivity limitations. It is essential to extend these studies toward the more numerous and typical SFGs, characterized by IR luminosities LIRgalaxies from the literature, we revisit and propose new correlations between IR and CO luminosities, molecular gas, stellar and dust masses, specific SFR, molecular gas depletion timescales (tdepl), molecular gas fractions (fgas), dust-to-gas ratios, and redshift. These correlations betray the interplay between gas, dust, and star formation in galaxies.All the LIR, L'CO(1-0) data are best-fitted with a single relation, which spans 5 orders of magnitude in LIR, covers redshifts from z=0 to z=5.3, and samples spirals, main sequence SFGs, and starbursts. This favors a universal star formation. We find an increase of tdepl with Ms, as now revealed by low-Ms SFGs at z>1 and also observed at z=0, which contrasts with the acknowledged constant tdepl and refutes the linearity of the Kennicutt-Schmidt relation between molecular gas and SFR at galactic scales. A steady increase of fgas with redshift is predicted and is observed from z~0 to z~1.5, but is followed by a mild increase toward higher redshifts, which we further confirm with our highest redshift CO measurement in an L* galaxy at z=3.6. We provide the first fgas measure in z>1 SFGs at the low-Ms end 109.4evidence for a nonuniversal

  12. NGC 5291: Implications for the Formation of Dwarf Galaxies

    NASA Technical Reports Server (NTRS)

    Malphrus, Benjamin K.; Simpson, Caroline E.; Gottesman, S. T.; Hawarden, Timothy G.

    1997-01-01

    The possible formation and evolution of dwarf irregular galaxies from material derived from perturbed evolved galaxies is addressed via an H I study of a likely example, the peculiar system NGC 5291. This system, located in the western outskirts of the cluster Abell 3574, contains the lenticular galaxy NGC 5291 which is in close proximity to a disturbed companion and is flanked by an extensive complex of numerous knots extending roughly 4 min north and 4 min south of the galaxy. In an initial optical and radio study, Longmore et al. (1979, MNRAS, 188, 285) showed that these knots have the spectra of vigorous star-forming regions, and suggested that some may in fact be young dwarf irregular galaxies. High resolution 21-cm line observations taken with the VLA are presented here and reveal that the H I distribution associated with this system encompasses not only the entire N-S complex of optical knots, but also forms an incomplete ring or tail that extends approximately 3 min to the west. The H I associated with NGC 5291 itself shows a high velocity range; the Seashell is not detected. The formation mechanism for this unusual system is unclear and two models - a large, low-luminosity ram-swept disk, and a ram-swept interaction-are discussed. The H I in the system contains numerous concentrations, mostly along the N-S arc of the star-forming complexes, which generally coincide with one or more optical knots; the larger H I features contain several x 10(exp 9) solar mass of gas. Each of the knots is compared to a set of criteria designed to determine if these objects are bound against their own internal kinetic energy and are tidally stable relative to the host galaxy. An analysis of the properties of the H I concentrations surrounding the optical star-forming complexes indicates that at least the largest of these is a bound system; it also possesses a stellar component. It is suggested that this object is a genuinely young dwarf irregular galaxy that has evolved from

  13. Ripples in disk galaxies

    NASA Astrophysics Data System (ADS)

    Schweizer, Francois; Seitzer, Patrick

    1988-05-01

    The authors present evidence that ripples ("shells") occur not only in ellipticals, as hitherto believed, but also in disk galaxies of Hubble types S0, S0/Sa, and Sa, and probably even in the Sbc galaxy NGC 3310. This evidence includes the discovery of ripples in the northern disk galaxies NGC 3032, 3619, 4382, 5548 (a Seyfert), and 5739, and in the "diskless S0" NGC 7600. It is argued that these ripples cannot usually have resulted form transient spiral waves or other forced vibrations in the existing disks, but instead consist of extraneous sheet-like matter. The frequent presence of major disk-shaped companions suggests that ripple material may be acquired not only through wholesale mergers, but also through mass transfer from neighbor galaxies.

  14. Early-Type Galaxies in Extremely Isolated Environments: Typical Ellipticals?

    NASA Astrophysics Data System (ADS)

    Marcum, Pamela M.; Aars, Christian E.; Fanelli, Michael N.

    2004-06-01

    We have conducted a BVR imaging survey of nine early-type galaxies previously verified to exist in extremely isolated environments. Our goals are to establish a baseline of morphological and photometric properties for spheroidal systems evolving in extremely low-density environments and to compare these properties with signatures predicted for merged galaxy groups. We find that these isolated systems are underluminous by at least a magnitude compared with objects identified as merged group remnants in other studies. Image processing techniques sensitive to shell features produced no detections, a result in strong contrast to the high frequency of such structures found in other isolated elliptical galaxies. Two objects, KIG 164 and KIG 870, appear to be merger remnants, as indicated by their disturbed morphology, apparent tidal features, and blue colors. KIG 164 exhibits an asymmetric nuclear morphology and a low surface brightness ``bridge'' between it and a possible dwarf satellite. KIG 870 shows both fan-shaped emission at large radii and a possible double nucleus. Two other galaxies, KIG 412 and KIG 792, are also blue, but without any morphological peculiarities, suggesting that these systems are advanced mergers, older than KIG 164 and KIG 870. Two systems appear to be isolated lenticular galaxies with no evidence of a merger history. Based on their red colors, good fit to a R1/4-law light distribution, and the lack of morphological peculiarities, two other galaxies, KIG 557 and KIG 824, are found to be excellent candidates for passively evolving primordial elliptical galaxies formed early in cosmic time. Optical data were obtained with the 2.1 m Otto Struve telescope at McDonald Observatory, which is operated by the University of Texas at Austin.

  15. Life in the Galaxy?

    NASA Astrophysics Data System (ADS)

    Shostak, G. S.

    The arguments for and against the SETI (Search for Extra Terrestrial Intelligence) program are discussed. Based on apparently reasonable assumptions regarding the number of civilizations likely to exist in the Galaxy, it seems that ten million years would be sufficient time for an ambitious group of aliens to colonize the Galaxy; since no concrete evidence of aliens has turned up, the assumptions have to be reconsidered. The views of Sagan, Hart, Drake and a number of other researchers are noted.

  16. Triple Scoop from Galaxy Hunter

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 1Figure 2Figure 3

    Silver Dollar Galaxy: NGC 253 (figure 1) Located 10 million light-years away in the southern constellation Sculptor, the Silver Dollar galaxy, or NGC 253, is one of the brightest spiral galaxies in the night sky. In this edge-on view from NASA's Galaxy Evolution Explorer, the wisps of blue represent relatively dustless areas of the galaxy that are actively forming stars. Areas of the galaxy with a soft golden glow indicate regions where the far-ultraviolet is heavily obscured by dust particles.

    Gravitational Dance: NGC 1512 and NGC 1510 (figure 2) In this image, the wide ultraviolet eyes of NASA's Galaxy Evolution Explorer show spiral galaxy NGC 1512 sitting slightly northwest of elliptical galaxy NGC 1510. The two galaxies are currently separated by a mere 68,000 light-years, leading many astronomers to suspect that a close encounter is currently in progress.

    The overlapping of two tightly wound spiral arm segments makes up the light blue inner ring of NGC 1512. Meanwhile, the galaxy's outer spiral arm is being distorted by strong gravitational interactions with NGC 1510.

    Galaxy Trio: NGC 5566, NGC 5560, and NGC 5569 (figure 3) NASA's Galaxy Evolution Explorer shows a triplet of galaxies in the Virgo cluster: NGC 5560 (top galaxy), NGC 5566 (middle galaxy), and NGC 5569 (bottom galaxy).

    The inner ring in NGC 5566 is formed by two nearly overlapping bright arms, which themselves spring from the ends of a central bar. The bar is not visible in ultraviolet because it consists of older stars or low mass stars that do not emit energy at ultraviolet wavelengths. The outer disk of NGC 5566 appears warped, and the disk of NGC 5560 is clearly disturbed. Unlike its galactic neighbors, the disk of NGC 5569 does not appear to have been distorted by any passing

  17. J0454-0309: evidence of a strong lensing fossil group falling into a poor galaxy cluster

    NASA Astrophysics Data System (ADS)

    Schirmer, M.; Suyu, S.; Schrabback, T.; Hildebrandt, H.; Erben, T.; Halkola, A.

    2010-05-01

    Aims: We have discovered a strong lensing fossil group (J0454) projected near the well-studied cluster MS0451-0305. Using the large amount of available archival data, we compare J0454 to normal groups and clusters. A highly asymmetric image configuration of the strong lens enables us to study the substructure of the system. Methods: We used multicolour Subaru/Suprime-Cam and CFHT/Megaprime imaging, together with Keck spectroscopy to identify member galaxies. A VLT/FORS2 spectrum was taken to determine the redshifts of the brightest elliptical and the lensed arc. Using HST/ACS images, we determined the group's weak lensing signal and modelled the strong lens system. This is the first time that a fossil group is analysed with lensing methods. The X-ray luminosity and temperature were derived from XMM-Newton data. Results: J0454 is located at z = 0.26, with a gap of 2.5 mag between the brightest and second brightest galaxies within half the virial radius. Outside a radius of 1.5 Mpc, we find two filaments extending over 4 Mpc, and within we identify 31 members spectroscopically and 33 via the red sequence with i < 22 mag. They segregate into spirals (σ_v = 590 km s-1) and a central concentration of ellipticals (σ_v = 480 km s-1), establishing a morphology-density relation. Weak lensing and cluster richness relations yield consistent values of r200 = 810-850 kpc and M200 = (0.75-0.90) × 1014 M_⊙. The brightest group galaxy (BGG) is inconsistent with the dynamic centre of J0454. It strongly lenses a galaxy at z = 2.1 ± 0.3, and we model the lens with a pseudo-isothermal elliptical mass distribution. A high external shear, and a discrepancy between the Einstein radius and the weak lensing velocity dispersion requires that the BGG must be offset from J0454's dark halo centre by at least 90-130 kpc. The X-ray halo is offset by 24 ± 16 kpc from the BGG, shows no signs of a cooling flow and can be fit by a single β-model. With LX = (1.4 ± 0.2) × 1043 erg s-1 J0454

  18. Changes of soil prokaryotic communities after clear-cutting in a karst forest: evidences for cutting-based disturbance promoting deterministic processes.

    PubMed

    Zhang, Xiao; Liu, Shirong; Li, Xiangzhen; Wang, Jingxin; Ding, Qiong; Wang, Hui; Tian, Chao; Yao, Minjie; An, Jiaxing; Huang, Yongtao

    2016-03-01

    To understand the temporal responses of soil prokaryotic communities to clear-cutting disturbance, we examined the changes in soil bacterial and archaeal community composition, structure and diversity along a chronosequence of forest successional restoration using high-throughput 16S rRNA gene sequencing. Our results demonstrated that clear-cutting significantly altered soil bacterial community structure, while no significant shifts of soil archaeal communities were observed. The hypothesis that soil bacterial communities would become similar to those of surrounding intact primary forest with natural regeneration was supported by the shifts in the bacterial community composition and structure. Bacterial community diversity patterns induced by clear-cutting were consistent with the intermediate disturbance hypothesis. Dynamics of bacterial communities was mostly driven by soil properties, which collectively explained more than 70% of the variation in bacterial community composition. Community assembly data revealed that clear-cutting promoted the importance of the deterministic processes in shaping bacterial communities, coinciding with the resultant low resource environments. But assembly processes in the secondary forest returned a similar level compared to the intact primary forest. These findings suggest that bacterial community dynamics may be predictable during the natural recovery process.

  19. [Climacteric disturbances. 2. Therapy of climacteric disturbances].

    PubMed

    Döring, G K

    1976-07-01

    After defining the terms climacterium and menopause the causes of climacteric disturbances are explained. During the premenopausal stage disturbances of the cycle are prevailing, caused by an insufficiency of the corpus luteum. Of climacteric disturbances should be spoken only after menopause. They are divided into: vegetative disturbances, troubles of metabolism, cardiovascular dysregulation, psychic deviations, sexual troubles and changes of the skin. The therapy of disturbances during the premenopausal stage mainly consists of the substitution of progesterone or in a cycle-like estrogen-progesterone-therapy. In the premenopausal stage estrogens are the therapy of choice. Among orally efficient estrogens the conjugated estrogen and the estradiol-valerianat are preferred. Side-effects and contraindications are discussed in detail. Among gynecologists there exists no disagreement about the necessity of therapy of serious climacteric disturbances, the opinions about prophylactic estrogen-therapy in women differ. PMID:184019

  20. Interacting binary galaxies. III. Observations of NGC 1587/1588 and NGC 7236/7237

    SciTech Connect

    Borne, K.D.; Hoessel, J.G.

    1988-07-01

    The catalog of isolated galaxy pairs prepared by Karachentsev has been culled for its E-E constituents, and the results are reported. Radial variations of rotation velocity and velocity dispersion are extracted from the spectroscopic data for each of the two galaxies of a given pair. Such observations are described for two Karachentsev pairs, Nos. 99 and 564. The observed disturbances in rotation velocity and luminosity distribution are discussed in terms of the gravitational interaction hypothesis. It is argued that observational evidence of tidal friction in action is evidenced by these findings. One of the highest rotation rates known for an E2 galaxy of average luminosity is found in NGC 1587, the brighter component of K99. Because this rotation is in the same sense as the binary orbital motion, the net angular momentum in this isolated binary system is large, challenging simple tidal torque theories to identify the source of the momentum. 62 references.

  1. Galaxy disruption in a halo of dark matter.

    PubMed

    Forbes, Duncan A; Beasley, Michael A; Bekki, Kenji; Brodie, Jean P; Strader, Jay

    2003-08-29

    The relics of disrupted satellite galaxies have been found around the Milky Way and Andromeda, but direct evidence of a satellite galaxy in the early stages of disruption has remained elusive. We have discovered a dwarf satellite galaxy in the process of being torn apart by gravitational tidal forces as it merges with a larger galaxy's dark matter halo. Our results illustrate the morphological transformation of dwarf galaxies by tidal interaction and the continued buildup of galaxy halos.

  2. EVIDENCE FOR SPATIALLY COMPACT Ly{alpha} EMISSION IN z = 3.1 Ly{alpha}-EMITTING GALAXIES

    SciTech Connect

    Bond, Nicholas A.; Gawiser, Eric; Feldmeier, John J.; Matkovic, Ana; Gronwall, Caryl; Ciardullo, Robin E-mail: gawiser@physics.rutgers.ed E-mail: matkovic@astro.psu.ed E-mail: rbc@astro.psu.ed

    2010-06-20

    We present the results of a high spatial resolution study of the line emission in a sample of z = 3.1 Ly{alpha}-emitting galaxies (LAEs) in the Extended Chandra Deep Field-South. Of the eight objects with coverage in our HST/WFPC2 narrowband imaging, two have clear detections and two are barely detected ({approx}2 {sigma}). The clear detections are within {approx}0.5 kpc of the centroid of the corresponding rest-UV continuum source, suggesting that the line-emitting gas and young stars in LAEs are spatially coincident. The brightest object exhibits extended emission with a half-light radius of {approx}1.5 kpc, but a stack of the remaining LAE surface brightness profiles is consistent with the WFPC2 point-spread function. This suggests that the Ly{alpha} emission in these objects originates from a compact ({approx}<2 kpc) region and cannot be significantly more extended than the far-UV continuum emission ({approx}<1 kpc). Comparing our WFPC2 photometry to previous ground-based measurements of their monochromatic fluxes, we find at 95% (99.7%) confidence that we cannot be missing more than 22% (32%) of the Ly{alpha} emission.

  3. Regional boreal biodiversity peaks at intermediate human disturbance.

    PubMed

    Mayor, S J; Cahill, J F; He, F; Sólymos, P; Boutin, S

    2012-01-01

    The worldwide biodiversity crisis has intensified the need to better understand how biodiversity and human disturbance are related. The 'intermediate disturbance hypothesis' suggests that disturbance regimes generate predictable non-linear patterns in species richness. Evidence often contradicts intermediate disturbance hypothesis at small scales, and is generally lacking at large regional scales. Here, we present the largest extent study of human impacts on boreal plant biodiversity to date. Disturbance extent ranged from 0 to 100% disturbed in vascular plant communities, varying from intact forest to agricultural fields, forestry cut blocks and oil sands. We show for the first time that across a broad region species richness peaked in communities with intermediate anthropogenic disturbance, as predicted by intermediate disturbance hypothesis, even when accounting for many environmental covariates. Intermediate disturbance hypothesis was consistently supported across trees, shrubs, forbs and grasses, with temporary and perpetual disturbances. However, only native species fit this pattern; exotic species richness increased linearly with disturbance.

  4. Pre-clinical studies of toxin-specific Nanobodies: Evidence of in vivo efficacy to prevent fatal disturbances provoked by scorpion envenoming

    SciTech Connect

    Hmila, Issam; Cosyns, Bernard; Tounsi, Hayfa; Roosens, Bram; Caveliers, Vicky; Abderrazek, Rahma Ben; Boubaker, Samir; Muyldermans, Serge; El Ayeb, Mohamed; Bouhaouala-Zahar, Balkiss; Lahoutte, Tony

    2012-10-15

    Scorpions represent a significant threat to humans and animals in various countries throughout the world. Recently, we introduced Nanobodies (Nbs) to combat more efficiently scorpion envenoming and demonstrated the performance of NbAahIF12 and NbAahII10 to neutralize scorpion toxins of Androctonus australis hector venom. A bispecific Nb construct (NbF12-10) comprising these two Nbs is far more protective than the classic Fab′{sub 2} based therapy and is the most efficient antivenom therapy against scorpion sting in preclinical studies. Now we investigate the biodistribution and pharmacokinetics of {sup 99m}Tc labeled Nbs by in vivo imaging in rodents and compared these data with those of the Fab′{sub 2} product (PAS). The pharmacodynamics of the Nbs was investigated in rats by in vivo echocardiography and it is shown that NbF12-10 prevents effectively the hemodynamic disturbances induced by a lethal dose of venom. Moreover, even a late injection of NbF12-10 restores the heart rate and brings the blood pressure to baseline values. Histology confirms that NbF12-10 prevents lung and heart lesions of treated mice after envenoming. In conjunction, in this preclinical study, we provide proof of concept that NbF12-10 prevents effectively the fatal disturbances induced by Androctonus venom, and that the Nanobody based therapeutic has a potential to substitute the classic Fab′{sub 2} based product as immunotherapeutic in scorpion envenoming. Further clinical study using larger cohorts of animals should be considered to confirm the full protecting potential of our NbF12-10. -- Highlights: ► Nanobody therapy prevents the hemodynamic disturbances induced by a lethal dose. ► Late injection of Nanobody restores hemodynamic parameters to baseline values. ► Nanobody therapy prevents lung and heart lesions of treated mice after envenoming. ► Labeled Nanobody and Fab’2 pharmacokinetics curves reach plateau in favour of Nanobody.

  5. An Elegant Galaxy in an Unusual Light

    NASA Astrophysics Data System (ADS)

    2010-09-01

    A new image taken with the powerful HAWK-I camera on ESO's Very Large Telescope at Paranal Observatory in Chile shows the beautiful barred spiral galaxy NGC 1365 in infrared light. NGC 1365 is a member of the Fornax cluster of galaxies, and lies about 60 million light-years from Earth. NGC 1365 is one of the best known and most studied barred spiral galaxies and is sometimes nicknamed the Great Barred Spiral Galaxy because of its strikingly perfect form, with the straight bar and two very prominent outer spiral arms. Closer to the centre there is also a second spiral structure and the whole galaxy is laced with delicate dust lanes. This galaxy is an excellent laboratory for astronomers to study how spiral galaxies form and evolve. The new infrared images from HAWK-I are less affected by the dust that obscures parts of the galaxy than images in visible light (potw1037a) and they reveal very clearly the glow from vast numbers of stars in both the bar and the spiral arms. These data were acquired to help astronomers understand the complex flow of material within the galaxy and how it affects the reservoirs of gas from which new stars can form. The huge bar disturbs the shape of the gravitational field of the galaxy and this leads to regions where gas is compressed and star formation is triggered. Many huge young star clusters trace out the main spiral arms and each contains hundreds or thousands of bright young stars that are less than ten million years old. The galaxy is too remote for single stars to be seen in this image and most of the tiny clumps visible in the picture are really star clusters. Over the whole galaxy, stars are forming at a rate of about three times the mass of our Sun per year. While the bar of the galaxy consists mainly of older stars long past their prime, many new stars are born in stellar nurseries of gas and dust in the inner spiral close to the nucleus. The bar also funnels gas and dust gravitationally into the very centre of the galaxy

  6. Pre-clinical studies of toxin-specific nanobodies: evidence of in vivo efficacy to prevent fatal disturbances provoked by scorpion envenoming.

    PubMed

    Hmila, Issam; Cosyns, Bernard; Tounsi, Hayfa; Roosens, Bram; Caveliers, Vicky; Abderrazek, Rahma Ben; Boubaker, Samir; Muyldermans, Serge; El Ayeb, Mohamed; Bouhaouala-Zahar, Balkiss; Lahoutte, Tony

    2012-10-15

    Scorpions represent a significant threat to humans and animals in various countries throughout the world. Recently, we introduced Nanobodies (Nbs) to combat more efficiently scorpion envenoming and demonstrated the performance of NbAahIF12 and NbAahII10 to neutralize scorpion toxins of Androctonus australis hector venom. A bispecific Nb construct (NbF12-10) comprising these two Nbs is far more protective than the classic Fab'(2) based therapy and is the most efficient antivenom therapy against scorpion sting in preclinical studies. Now we investigate the biodistribution and pharmacokinetics of (99m)Tc labeled Nbs by in vivo imaging in rodents and compared these data with those of the Fab'(2) product (PAS). The pharmacodynamics of the Nbs was investigated in rats by in vivo echocardiography and it is shown that NbF12-10 prevents effectively the hemodynamic disturbances induced by a lethal dose of venom. Moreover, even a late injection of NbF12-10 restores the heart rate and brings the blood pressure to baseline values. Histology confirms that NbF12-10 prevents lung and heart lesions of treated mice after envenoming. In conjunction, in this preclinical study, we provide proof of concept that NbF12-10 prevents effectively the fatal disturbances induced by Androctonus venom, and that the Nanobody based therapeutic has a potential to substitute the classic Fab'(2) based product as immunotherapeutic in scorpion envenoming. Further clinical study using larger cohorts of animals should be considered to confirm the full protecting potential of our NbF12-10.

  7. The DEEP2 Galaxy Redshift Survey: AEGIS observations of a Dual AGNat z = 0.7

    SciTech Connect

    Gerke1, Brian F.; Newman, Jeffrey A.; Lotz, Jennifer; Yan,Renbin; Barmby, P.; Coil, Alison L.; Conselice, Christopher J.; Ivison,R.J.; Lin, Lihw ai; Koo, David C.; Nandra, Kirpal; Salim, Samir; Small,Todd; Weiner, Benjamin J.; Cooper, Michael C.; Davis, Marc; Faber, S.M.; Guhathakurta, Puragra

    2006-10-13

    We present evidence for a dual Active Galactic Nucleus (AGN) within an early-type galaxy at z = 0.709 in the Extended Groth Strip. The galaxy lies on the red sequence, with absolute magnitude M{sub B} = -21.0 ( AB, w , with h = 0 0.7) and rest-frame color U - B = 1.38. Its optical spectrum shows strong, double-peaked [O III] emission lines and weak H{beta} emission, with Seyfert-like line ratios. The two narrow peaks are separate by 630 km s-1 in velocity and arise from two distinct regions, spatially resolved in the DEIMOS spectrum, with a projected physical separation of 1.2 kpc. HST/ACS imaging shows an early-type (E/S0) galaxy with hints of disturbed structure, consistent with the remnant of a dissipationless merger. Multiwavelength photometric information from the AEGIS consortium confirm the identification of a dust-obscured AGN in an early-type galaxy, with detections in X-ray, optical, infrared and radio wavebands. These data are most readily explained as a single galaxy harboring two AGN--the first such system to be observed in an otherwise typical early-type galaxy.

  8. Discovery of new variable radio sources in the nucleus of the nearby galaxy messier 82.

    PubMed

    Kronberg, P P; Sramek, R A

    1985-01-01

    Widespread variability has been discovered in a large population of radio sources close to the nucleus of an active galaxy. The galaxy, Messier 82 (M82), and others similar to it show evidence for enhanced nuclear activity and unusually strong far-infrared emission. The observational data, obtained with the National Radio Astronomy Observatory's Very Large Array in New Mexico over the past 3 years, provide the first direct "look" at a starburst-the phenomenon of sudden, rapid star formation which occurs near the nucleus of a small fraction of galaxies. Nearly all the brightest of about 40 radio sources in M82' s nucleus decreased in intensity over 2.7 years up to October 1983. One source, which in February 1981 was ten times as bright as our Galaxy's most luminous supernova remnant, turned off within only a few months. Most of the other ten strongest sources are declining so rapidly that they will fade into the background within 30 years. Thus, new supernovae are expected to appear in M82' s nucleus every few years. The discovery has revealed the "engine room" of the mysterious activity in M82 and, by implication, similar active galaxies which have disturbed nuclei and which are unusually luminous in the far infrared. An estimate of the rate of energy input by the radio-visible supernovae closely matches the far-infrared luminosities which were recently measured for M82 and other similar galaxies. PMID:17809994

  9. Ultracompact Blue Dwarfs: Galaxy Formation in the Local Universe?

    NASA Astrophysics Data System (ADS)

    Corbin, Michael

    2004-07-01

    Recent observations suggest that very low-mass galaxies in the local universe are still in the process of formation. To investigate this issue we propose to obtain deep ACS HRC images in the U, V and I bands of a sample of 11 "ultracompact" blue dwarf galaxies {UCBDs} identified in the Sloan Digital Sky Survey. These objects are nearby {z < 0.009}, actively star-forming, and have extremely small angular and physical sizes {d < 6" and D < 1 kpc}. They also tend to reside in voids. Our WFPC2 images of the prototype object of this class, POX 186, reveal this tiny object to have a highly disturbed morphlogy indicative of a recent {within 10^8 yr} collision between two small { 100 pc} clumps of stars that could represent the long-sought building blocks predicted by the Press-Schechter model of hierarchical galaxy formation. This collision has also triggered the formation of a "super" star cluster {SSC} at the object's core that may be the progenitor of a globular cluster. POX 186 thus appears to be a very small dwarf galaxy in the process of formation. This exciting discovery strongly motivates HST imaging of a full sample of UCBDs in order to determine if they have morphologies similar to POX 186. HST images are essential for resolving the structure of these objects, including establishing the presence of SSCs. HST also offers the only way to determine their morphologies in the near UV. The spectra of the objects available from the SDSS will also allow us to measure their star formation rates, dust content and metallicities. In addition to potentially providing the first direct evidence of Press-Schechter building blocks, these data could yield insight into the relationship between galaxy and globular cluster formation, and will serve as a test of the recent "downsizing" model of galaxy formation in which the least massive objects are the last to form.

  10. Down-the-barrel and Transverse Observations of the Large Magellanic Cloud: Evidence for a Symmetric Galactic Wind on the Near and Far Sides of the Galaxy

    NASA Astrophysics Data System (ADS)

    Barger, K. A.; Lehner, N.; Howk, J. C.

    2016-02-01

    We compare the properties of gas flows on both the near and far side of the Large Magellanic Cloud (LMC) disk using Hubble Space Telescope UV absorption-line observations toward an active galactic nucleus behind (transverse) and a star within (down-the-barrel) the LMC disk at an impact parameter of 3.2 {kpc}. We find that even in this relatively quiescent region gas flows away from the disk at speeds up to ˜ 100 {km} {{{s}}}-1 in broad and symmetrical absorption in the low and high ions. The symmetric absorption profiles combined with previous surveys showing little evidence that the ejected gas returns to the LMC and provide compelling evidence that the LMC drives a global, large-scale outflow across its disk, which is the likely result of a recent burst of star formation in the LMC. We find that the outflowing gas is multiphase, ionized by both photoionization (Si ii and Si iii) and collisional ionization (Si iv and C iv). We estimate a total mass and outflow rate to be ≳ {10}7 {M}⊙ and ≳ \\quad 0.4 {M}⊙ {{yr}}-1. Since the velocity of this large-scale outflow does not reach the LMC escape velocity, the gas removal is likely aided by either ram-pressure stripping with the Milky Way (MW) halo or tidal interactions with the surrounding galaxies, implying that the environment of LMC-like or dwarf galaxies plays an important role in their ultimate gas starvation. Finally we reassess the mass and plausible origins of the high-velocity complex toward the LMC given its newly determined distance that places it in the lower MW halo and sky-coverage that shows it extends well beyond the LMC disk. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract No. NAS5-26555.

  11. Spectroscopic Study of Star-forming Galaxies in Filaments and the Field at z ~ 0.5: Evidence for Environmental Dependence of Electron Density

    NASA Astrophysics Data System (ADS)

    Darvish, Behnam; Mobasher, Bahram; Sobral, David; Hemmati, Shoubaneh; Nayyeri, Hooshang; Shivaei, Irene

    2015-12-01

    We study the physical properties of a spectroscopic sample of 28 star-forming galaxies in a large filamentary structure in the COSMOS field at z ˜ 0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of 30 field galaxies. We spectroscopically confirm the presence of a large galaxy filament (˜8 Mpc), along which five confirmed X-ray groups exist. We show that within the uncertainties, the ionization parameter, equivalent width (EW), EW versus specific star-formation rate (sSFR) relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that, on average, filament star-forming galaxies are more metal enriched (˜0.1-0.15 dex), possibly owing to the inflow of the already-enriched intrafilamentary gas into filament galaxies. Moreover, we show that electron densities are significantly lower (a factor of ˜17) in filament star-forming systems compared to those in the field, possibly because of a longer star-formation timescale for filament star-forming galaxies. Our results highlight the potential pre-processing role of galaxy filaments and intermediate-density environments on the evolution of galaxies, which has been highly underestimated.

  12. SPECTROSCOPIC STUDY OF STAR-FORMING GALAXIES IN FILAMENTS AND THE FIELD AT z ∼ 0.5: EVIDENCE FOR ENVIRONMENTAL DEPENDENCE OF ELECTRON DENSITY

    SciTech Connect

    Darvish, Behnam; Mobasher, Bahram; Hemmati, Shoubaneh; Shivaei, Irene; Sobral, David; Nayyeri, Hooshang

    2015-12-01

    We study the physical properties of a spectroscopic sample of 28 star-forming galaxies in a large filamentary structure in the COSMOS field at z ∼ 0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of 30 field galaxies. We spectroscopically confirm the presence of a large galaxy filament (∼8 Mpc), along which five confirmed X-ray groups exist. We show that within the uncertainties, the ionization parameter, equivalent width (EW), EW versus specific star-formation rate (sSFR) relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that, on average, filament star-forming galaxies are more metal enriched (∼0.1–0.15 dex), possibly owing to the inflow of the already-enriched intrafilamentary gas into filament galaxies. Moreover, we show that electron densities are significantly lower (a factor of ∼17) in filament star-forming systems compared to those in the field, possibly because of a longer star-formation timescale for filament star-forming galaxies. Our results highlight the potential pre-processing role of galaxy filaments and intermediate-density environments on the evolution of galaxies, which has been highly underestimated.

  13. Spectroscopic Study of Star-forming Galaxies in Filaments and the Field at z~0.5: Evidence for Environmental Dependence of Electron Density

    NASA Astrophysics Data System (ADS)

    Darvish, Behnam; Mobasher, Bahram; Sobral, David; Hemmati, Shoubaneh; Nayyeri, Hooshang; Shivaei, Irene

    2016-01-01

    We study the physical properties of a spectroscopic sample of 28 star-forming galaxies in a large filamentary structure in the COSMOS field at z~0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of 30 field galaxies. We spectroscopically confirm the presence of a large galaxy filament (~ 8 Mpc), along which five confirmed X-ray groups exist. We show that within the uncertainties, the ionization parameter, equivalent width (EW), EW versus specific star-formation rate (sSFR) relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that on average, filament star-forming galaxies are more metal-enriched (~ 0.1-0.15 dex), possibly due to the inflow of the already enriched intrafilamentary gas into filament galaxies. Moreover, we show that electron densities are significantly lower (a factor of ~17) in filament star-forming systems compared to those in the field, possibly because of a longer star-formation timescale for filament star-forming galaxies. Our results highlight the potential pre-processing role of galaxy filaments and intermediate-density environments on the evolution of galaxies, which has been highly underestimated.

  14. Do elliptical galaxies have thick disks?

    NASA Technical Reports Server (NTRS)

    Thomson, R. C.; Wright, A. E.

    1990-01-01

    The authors discuss new evidence which supports the existence of thick disks in elliptical/SO galaxies. Numerical simulations of weak interactions with thick disk systems produce shell structures very similar in appearance to those observed in many shell galaxies. The authors think this model presents a more plausible explanation for the formation of shell structures in elliptical/SO galaxies than does the merger model and, if correct, supports the existence of thick disks in elliptical/SO galaxies.

  15. Gas dynamics in interacting and merging galaxies

    SciTech Connect

    Olson, K.M.

    1990-01-01

    A three dimensional model of the dynamics of gas clouds in interacting galaxies is developed. The gas clouds move under the combined gravitational influence of two galaxies passing close to each other. By performing a multipole expansion of the gravitational field the effects of self-gravity within a galaxy are included. This allows the case to be modeled in which the two galaxies merge. The gas clouds are allowed to interact with one another by colliding. They either coalesce to form a larger cloud or are disrupted, depending on their relative kinetic energy as compared to the total gravitational binding energy of the two-cloud system. Various cases are considered by varying such parameters as impact parameter, inclination of the gaseous disk of a galaxy to the orbital plane of the two, interacting galaxies, relative velocity of the galaxies, the mass ratio of the galaxies, and the presence of gas in the second galaxy. As the strength of the interaction increases the more disturbed the interstellar medium becomes. The clouds collide at an increased rate and with larger velocities so that the fraction of collisions which disrupt the clouds rises as the strength of the interaction increases. Since interacting galaxies are observed to have elevated star formation rates, it is concluded that the star formation induced by the interaction of two galaxies is related to the high velocity, disruptive cloud-cloud collisions.

  16. High-velocity blueshifted Fe II absorption in the dwarf star-forming galaxy PHL 293B: evidence for a wind driven supershell?

    NASA Astrophysics Data System (ADS)

    Terlevich, Roberto; Terlevich, Elena; Bosch, Guillermo; Díaz, Ángeles; Hägele, Guillermo; Cardaci, Mónica; Firpo, Verónica

    2014-12-01

    X-shooter and WHT-ISIS spectra of the star-forming galaxy PHL 293B also known as A2228-00 and SDSS J223036.79-000636.9 are presented in this paper. We find broad (FWHM = 1000 km s-1) and very broad (FWZI = 4000 km s-1) components in the Balmer lines, narrow absorption components in the Balmer series blueshifted by 800 km s-1, previously undetected Fe II multiplet (42) absorptions also blueshifted by 800 km s-1, IR Ca II triplet stellar absorptions consistent with [Fe/H] < -2.0 and no broad components or blueshifted absorptions in the He I lines. Based on historical records, we found no optical variability at the 5σ level of 0.02 mag between 2005 and 2013 and no optical variability at the level of 0.1 mag for the past 24 yr. The lack of variability rules out transient phenomena like luminous blue variables or Type IIn supernovae as the origin of the blueshifted absorptions of H I and Fe II. The evidence points to either a young and dense expanding supershell or a stationary cooling wind, in both cases driven by the young cluster wind.

  17. Evidence for a Circum-Nuclear and Ionised Absorber in the X-ray Obscured Broad Line Radio Galaxy 3C 445

    NASA Technical Reports Server (NTRS)

    Braito, V.; Reeves, J. N.; Sambruna, R. M.; Gofford, J.

    2012-01-01

    Here we present the results of a Suzaku observation of the Broad Line Radio Galaxy 3C 445. We confirm the results obtained with the previous X-ray observations which unveiled the presence of several soft X-ray emission lines and an overall X-ray emission which strongly resembles a typical Seyfert 2 despite of the optical classification as an unobscured AGN. The broad band spectrum allowed us to measure for the first time the amount of reflection (R approximately 0.9) which together with the relatively strong neutral Fe Ka emission line (EW approximately 100 eV) strongly supports a scenario where a Compton-thick mirror is present. The primary X ray continuum is strongly obscured by an absorber with a column density of NH = 2 - 3 x 10(exp 23) per square centimeter. Two possible scenarios are proposed for the absorber: a neutral partial covering or a mildly ionised absorber with an ionisation parameter log xi approximately 1.0 erg centimeter per second. A comparison with the past and more recent X-ray observations of 3C 445 performed with XMM-Newton and Chandra is presented, which provided tentative evidence that the ionised and outflowing absorber varied. We argue that the absorber is probably associated with an equatorial diskwind located within the parsec scale molecular torus.

  18. Disturbances in Body Ownership in Schizophrenia: Evidence from the Rubber Hand Illusion and Case Study of a Spontaneous Out-of-Body Experience

    PubMed Central

    Thakkar, Katharine N.; Nichols, Heathman S.; McIntosh, Lindsey G.; Park, Sohee

    2011-01-01

    Background A weakened sense of self may contribute to psychotic experiences. Body ownership, one component of self-awareness, can be studied with the rubber hand illusion (RHI). Watching a rubber hand being stroked while one's unseen hand is stroked synchronously can lead to a sense of ownership over the rubber hand, a shift in perceived position of the real hand, and a limb-specific drop in stimulated hand temperature. We aimed to assess the RHI in schizophrenia using quantifiable measures: proprioceptive drift and stimulation-dependent changes in hand temperature. Methods The RHI was elicited in 24 schizophrenia patients and 21 matched controls by placing their unseen hand adjacent to a visible rubber hand and brushing real and rubber hands synchronously or asynchronously. Perceived finger location was measured before and after stimulation. Hand temperature was taken before and during stimulation. Subjective strength of the illusion was assessed by a questionnaire. Results Across groups, the RHI was stronger during synchronous stimulation, indicated by self-report and proprioceptive drift. Patients reported a stronger RHI than controls. Self-reported strength of RHI was associated with schizotypy in controls Proprioceptive drift was larger in patients, but only following synchronous stimulation. Further, we observed stimulation-dependent changes in skin temperature. During right hand stimulation, temperature dropped in the stimulated hand and rose in the unstimulated hand. Interestingly, induction of RHI led to an out-of-body experience in one patient, linking body disownership and psychotic experiences. Conclusions The RHI is quantitatively and qualitatively stronger in schizophrenia. These findings suggest that patients have a more flexible body representation and weakened sense of self, and potentially indicate abnormalities in temporo-parietal networks implicated in body ownership. Further, results suggest that these body ownership disturbances might be at

  19. Interacting binary galaxies. IV. Simulations, masses, and spatial orientations for NGC 1587/1588 and NGC 7236/7237

    SciTech Connect

    Borne, K.D.

    1988-07-01

    Successful efforts to match interaction models to all of the available data for two pairs of interacting binary galaxies, Nos. 99 and 564 in the Karachentsev catalog of isolated pairs, are described. The results validate simple Newtonian gravity on the 10 kpc scale. The dynamical orbital status of both K99 and K564 is uniquely determined, and the masses and spatial orientations of the pairs are tightly constrained. Total masses for the pairs are derived which are quite reasonable and yield M/L values near 10. It is concluded that the observed disturbances in rotation velocity and luminosity distribution for these binary galaxies are entirely consistent with the merger hypothesis. Distortions including U-shaped rotation profiles and one-sided luminosity disturbances provide solid observational evidence of tidal friction in action. 18 references.

  20. Asymmetric Galaxies: Nature or Nurture?

    NASA Astrophysics Data System (ADS)

    Wilcots, E. M.

    2010-10-01

    Asymmetry is a common characteristic of many disk galaxies, but we have little understanding of its causes. In this contribution we look at the H I properties of a sample of Magellanic spirals, some of the most lopsided galaxies in the local Universe, and a sample of isolated spirals. In neither case do we see evidence of a link between the presence of a companion and asymmetry; indeed, asymmetry persists even in the absence of a companion or evidence of a recent interaction. These results suggest that once it arises, asymmetry may be a very long-lived characteristic of disk galaxies.

  1. Globular clusters as tracers of the halo assembly of nearby central cluster galaxies

    NASA Astrophysics Data System (ADS)

    Hilker, Michael; Richtler, Tom

    2016-08-01

    The properties of globular cluster systems (GCSs) in the core of the nearby galaxy clusters Fornax and Hydra I are presented. In the Fornax cluster we have gathered the largest radial velocity sample of a GCS system so far, which enables us to identify photometric and kinematic sub-populations around the central galaxy NGC 1399. Moreover, ages, metallicities and [α/Fe] abundances of a sub-sample of 60 bright globular clusters (GCs) with high S/N spectroscopy show a multi-modal distribution in the correlation space of these three parameters, confirming heterogeneous stellar populations in the halo of NGC 1399. In the Hydra I cluster very blue GCs were identified. They are not uniformly distributed around the central galaxies. 3-color photometry including the U-band reveals that some of them are of intermediate age. Their location coincides with a group of dwarf galaxies under disruption. This is evidence of a structurally young stellar halo ``still in formation'', which is also supported by kinematic measurements of the halo light that point to a kinematically disturbed system. The most massive GCs divide into generally more extended ultra-compact dwarf galaxies (UCDs) and genuine compact GCs. In both clusters, the spatial distribution and kinematics of UCDs are different from those of genuine GCs. Assuming that some UCDs represent nuclei of stripped galaxies, the properties of those UCDs can be used to trace the assembly of nucleated dwarf galaxies into the halos of central cluster galaxies. We show via semi-analytical approaches within a cosmological simulation that only the most massive UCDs in Fornax-like clusters can be explained by stripped nuclei, whereas the majority of lower mass UCDs belong to the star cluster family.

  2. Black Holes Are The Rhythm at The Heart of Galaxies

    NASA Astrophysics Data System (ADS)

    2008-11-01

    circulatory systems to keep us alive, black holes give galaxies a vital warm component. They are a careful creation of nature, allowing a galaxy to maintain a fragile equilibrium," Finoguenov said. X-rayChandra X-ray Image This finding helps to explain a decades-long paradox of the existence of large amounts of warm gas around certain galaxies, making them appear bright to the Chandra X-ray telescope. "For decades astronomers were puzzled by the presence of the warm gas around these objects. The gas was expected to cool down and form a lot of stars," said Mateusz Ruszkowski, an assistant professor in the University of Michigan Department of Astronomy. "Now, we see clear and direct evidence that the heating mechanism of black holes is persistent, producing enough heat to significantly suppress star formation. These plasma bubbles are caused by bursts of energy that happen one after another rather than occasionally, and the direct evidence for such periodic behavior is difficult to find." The bubbles form one inside to another, for a sort of Russian doll effect that has not been seen before, Ruszkowski said. One of the bubbles of hot plasma appears to be bursting and its contents spilling out, further contributing to the heating of the interstellar gas. "Disturbed gas in old galaxies is seen in many images that NASA's Chandra observatory obtained, but seeing multiple events is a really impressive evidence for persistent black hole activity," says Christine Jones, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. A paper on the research called "In-depth Chandra study of the AGN feedback in Virgo Elliptical Galaxy M84" has been published in Astrophysical Journal.

  3. Evidence for significant radial increase of the mass-to-light ratio based on phenomenological analysis of eight early-type galaxies

    NASA Astrophysics Data System (ADS)

    Samurović, Srdjan

    2016-01-01

    In this paper we study the sample of eight nearby early-type galaxies for which we have reliable estimates of their total dynamical mass in their interior and exterior parts based on the observed globular clusters. We use a phenomenological approach in the study of the gradient of the mass-to-light ratio of the galaxies in the sample. Since the outermost point for which we have the estimates of the mass-to-light ratios is fixed at 5 effective radii, this provides the opportunity to study the dark matter content of early-type galaxies which is expected to dominate in their outer parts, i.e., beyond ˜ 2-3 effective radii. We find that all the galaxies in our sample show the increase of the cumulative mass-to-light ratio which indicates various amount of additional, dark, component in their mass content. We show that galaxies with higher values of α+β (where α and β are slope parameters) have higher virial masses. We show that two galaxies which are slow rotators (NGC 1407 and NGC 5846) have α+β>1 whereas the remaining 6 galaxies are all fast rotators, and for these objects we found that α+β≤ 1. We also compare our findings with the theoretical expectations coming from numerical simulations.

  4. Black holes in the Milky Way Galaxy

    PubMed Central

    Filippenko, Alexei V.

    1999-01-01

    Extremely strong observational evidence has recently been found for the presence of black holes orbiting a few relatively normal stars in our Milky Way Galaxy and also at the centers of some galaxies. The former generally have masses of 4–16 times the mass of the sun, whereas the latter are “supermassive black holes” with millions to billions of solar masses. The evidence for a supermassive black hole in the center of our galaxy is especially strong. PMID:10468548

  5. Black holes in the milky way galaxy.

    PubMed

    Filippenko, A V

    1999-08-31

    Extremely strong observational evidence has recently been found for the presence of black holes orbiting a few relatively normal stars in our Milky Way Galaxy and also at the centers of some galaxies. The former generally have masses of 4-16 times the mass of the sun, whereas the latter are "supermassive black holes" with millions to billions of solar masses. The evidence for a supermassive black hole in the center of our galaxy is especially strong.

  6. Is There Evidence for a Hubble Bubble? The Nature of SN Ia Colors And Dust in External Galaxies

    SciTech Connect

    Conley, A.; Carlberg, R.G.; Guy, J.; Howell, D.A.; Jha, S.; Riess, A.G.; Sullivan, M.; /Toronto U., Astron. Dept.

    2007-06-06

    We examine recent evidence from the luminosity-redshift relation of Type Ia Supernovae for the {approx} 3 {sigma} detection of a ''Hubble bubble'' -- a departure of the local value of the Hubble constant from its globally averaged value. By comparing the MLCS2k2 fits used in that study to the results from other light-curve fitters applied to the same data, we demonstrate that this is related to the interpretation of SN color excesses (after correction for a light-curve shape-color relation) and the presence of a color gradient across the local sample. If the slope of the linear relation ({beta}) between SN color excess and luminosity is fit empirically, then the bubble disappears. If, on the other hand, the color excess arises purely from Milky-Way like dust, then SN data clearly favors a Hubble bubble. We demonstrate that SN data give {beta} {approx} 2, instead of the {beta} {approx} 4 one would expect from purely Milky-Way-like dust. This suggests that either SN intrinsic colors are more complicated than can be described with a single light-curve shape parameter, or that dust around SN is unusual. Disentangling these possibilities is both a challenge and an opportunity for large-survey SN Ia cosmology.

  7. No evidence for a dependence of the mass-size relation of early-type galaxies on environment in the local universe

    SciTech Connect

    Huertas-Company, M.; Shankar, F.; Mei, S.; Bernardi, M.; Meert, A.; Vikram, V.; Aguerri, J. A. L.

    2013-12-10

    The early-type galaxy (ETG) mass-size relation has largely been studied to understand how these galaxies assembled their mass. One key observational result of the last years is that massive galaxies increased their size by a factor of a few at fixed stellar mass from z ∼ 2. Hierarchical models favor minor mergers as a plausible driver of this size growth. Some of these models predict a significant environmental dependence in the sense that galaxies residing in more massive halos tend to be larger than galaxies in lower mass halos, at fixed stellar mass and redshift. At present, observational results of this environmental dependence are contradictory. In this paper we revisit this issue in the local universe, by investigating how the sizes of massive ETGs depend on a large-scale environment using an updated and accurate sample of ETGs in different environments—field, group, and clusters—from the Sloan Digital Sky Survey DR7. Our analysis does not show any significant environmental dependence of the sizes of central and satellite ETGs at fixed stellar mass at z ∼ 0. The size-mass relation of early-type galaxies at z ∼ 0 seems to be universal, i.e., independent of the mass of the host halo and of the position of the galaxy in that halo (central or satellite). The result is robust to different galaxy selections based on star formation, morphology, or central density. Considering our observational errors and the size of the sample, any size ratio larger than 30%-40% between massive galaxies (log(M {sub *}/M {sub ☉}) > 11) living in clusters and in the field can be ruled out at 3σ level.

  8. The SINS/zC-SINF survey of z ∼ 2 galaxy kinematics: Evidence for powerful active galactic nucleus-driven nuclear outflows in massive star-forming galaxies

    SciTech Connect

    Förster Schreiber, N. M.; Genzel, R.; Kurk, J. D.; Lutz, D.; Tacconi, L. J.; Wuyts, S.; Bandara, K.; Buschkamp, P.; Davies, R.; Eisenhauer, F.; Lang, P.; Newman, S. F.; Burkert, A.; Carollo, C. M.; Lilly, S. J.; Cresci, G.; Daddi, E.; Mainieri, V.; Mancini, C.; and others

    2014-05-20

    We report the detection of ubiquitous powerful nuclear outflows in massive (≥10{sup 11} M {sub ☉}) z ∼ 2 star-forming galaxies (SFGs), which are plausibly driven by an active galactic nucleus (AGN). The sample consists of the eight most massive SFGs from our SINS/zC-SINF survey of galaxy kinematics with the imaging spectrometer SINFONI, six of which have sensitive high-resolution adaptive optics-assisted observations. All of the objects are disks hosting a significant stellar bulge. The spectra in their central regions exhibit a broad component in Hα and forbidden [N II] and [S II] line emission, with typical velocity FWHM ∼ 1500 km s{sup –1}, [N II]/Hα ratio ≈ 0.6, and intrinsic extent of 2-3 kpc. These properties are consistent with warm ionized gas outflows associated with Type 2 AGN, the presence of which is confirmed via independent diagnostics in half the galaxies. The data imply a median ionized gas mass outflow rate of ∼60 M {sub ☉} yr{sup –1} and mass loading of ∼3. At larger radii, a weaker broad component is detected but with lower FWHM ∼485 km s{sup –1} and [N II]/Hα ≈ 0.35, characteristic for star formation-driven outflows as found in the lower-mass SINS/zC-SINF galaxies. The high inferred mass outflow rates and frequent occurrence suggest that the nuclear outflows efficiently expel gas out of the centers of the galaxies with high duty cycles and may thus contribute to the process of star formation quenching in massive galaxies. Larger samples at high masses will be crucial in confirming the importance and energetics of the nuclear outflow phenomenon and its connection to AGN activity and bulge growth.

  9. Diversity-disturbance relationships: frequency and intensity interact.

    PubMed

    Hall, Alex R; Miller, Adam D; Leggett, Helen C; Roxburgh, Stephen H; Buckling, Angus; Shea, Katriona

    2012-10-23

    An influential ecological theory, the intermediate disturbance hypothesis (IDH), predicts that intermediate levels of disturbance will maximize species diversity. Empirical studies, however, have described a wide variety of diversity-disturbance relationships (DDRs). Using experimental populations of microbes, we show that the form of the DDR depends on an interaction between disturbance frequency and intensity. We find that diversity shows a monotonically increasing, unimodal or flat relationship with disturbance, depending on the values of the disturbance aspects considered. These results confirm recent theoretical predictions, and potentially reconcile the conflicting body of empirical evidence on DDRs.

  10. SPATIALLY RESOLVED H{alpha} MAPS AND SIZES OF 57 STRONGLY STAR-FORMING GALAXIES AT z {approx} 1 FROM 3D-HST: EVIDENCE FOR RAPID INSIDE-OUT ASSEMBLY OF DISK GALAXIES

    SciTech Connect

    Nelson, Erica June; Van Dokkum, Pieter G.; Skelton, Rosalind E.; Bezanson, Rachel; Lundgren, Britt; Brammer, Gabriel; Foerster Schreiber, Natascha; Franx, Marijn; Fumagalli, Mattia; Patel, Shannon; Labbe, Ivo; Rix, Hans-Walter; Da Cunha, Elisabete; Schmidt, Kasper B.; Kriek, Mariska; Quadri, Ryan

    2012-03-10

    We investigate the buildup of galaxies at z {approx} 1 using maps of H{alpha} and stellar continuum emission for a sample of 57 galaxies with rest-frame H{alpha} equivalent widths >100 A in the 3D-HST grism survey. We find that the H{alpha} emission broadly follows the rest-frame R-band light but that it is typically somewhat more extended and clumpy. We quantify the spatial distribution with the half-light radius. The median H{alpha} effective radius r{sub e} (H{alpha}) is 4.2 {+-} 0.1 kpc but the sizes span a large range, from compact objects with r{sub e} (H{alpha}) {approx} 1.0 kpc to extended disks with r{sub e} (H{alpha}) {approx} 15 kpc. Comparing H{alpha} sizes to continuum sizes, we find =1.3 {+-} 0.1 for the full sample. That is, star formation, as traced by H{alpha}, typically occurs out to larger radii than the rest-frame R-band stellar continuum; galaxies are growing their radii and building up from the inside out. This effect appears to be somewhat more pronounced for the largest galaxies. Using the measured H{alpha} sizes, we derive star formation rate surface densities, {Sigma}{sub SFR}. We find that {Sigma}{sub SFR} ranges from {approx}0.05 M{sub Sun} yr{sup -1} kpc{sup -2} for the largest galaxies to {approx}5 M{sub Sun} yr{sup -1} kpc{sup -2} for the smallest galaxies, implying a large range in physical conditions in rapidly star-forming z {approx} 1 galaxies. Finally, we infer that all galaxies in the sample have very high gas mass fractions and stellar mass doubling times <500 Myr. Although other explanations are also possible, a straightforward interpretation is that we are simultaneously witnessing the rapid formation of compact bulges and large disks at z {approx} 1.

  11. Edge-on Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    NASA's Hubble Space Telescope has imaged an unusual edge-on galaxy, revealing remarkable details of its warped dusty disc and showing how colliding galaxies trigger the birth of new stars.

    The image, taken by Hubble's Wide Field and Planetary Camera 2 (WFPC2), is online at http://heritage.stsci.edu and http://www.jpl.nasa.gov/images/wfpc. The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. During observations of the galaxy, the camera passed a milestone, taking its 100,000th image since shuttle astronauts installed it in Hubble in 1993.

    The dust and spiral arms of normal spiral galaxies, like our Milky Way, look flat when seen edge- on. The new image of the galaxy ESO 510-G13 shows an unusual twisted disc structure, first seen in ground-based photographs taken at the European Southern Observatory in Chile. ESO 510-G13 lies in the southern constellation Hydra, some 150 million light-years from Earth. Details of the galaxy's structure are visible because interstellar dust clouds that trace its disc are silhouetted from behind by light from the galaxy's bright, smooth central bulge.

    The strong warping of the disc indicates that ESO 510-G13 has recently collided with a nearby galaxy and is in the process of swallowing it. Gravitational forces distort galaxies as their stars, gas, and dust merge over millions of years. When the disturbances die out, ESO 510-G13 will be a single galaxy.

    The galaxy's outer regions, especially on the right side of the image, show dark dust and bright clouds of blue stars. This indicates that hot, young stars are forming in the twisted disc. Astronomers believe star formation may be triggered when galaxies collide and their interstellar clouds are compressed.

    The Hubble Heritage Team used WFPC2 to observe ESO 510-G13 in April 2001. Pictures obtained through blue, green, and red filters were combined to make this color-composite image, which emphasizes the contrast between the dusty

  12. Evidence for a nuclear radio jet and its structure down to ≲100 Schwarzschild radii in the center of the Sombrero galaxy (M 104, NGC 4594)

    SciTech Connect

    Hada, Kazuhiro; Giroletti, Marcello; Giovannini, Gabriele; Doi, Akihiro; Nagai, Hiroshi; Honma, Mareki; Inoue, Makoto

    2013-12-10

    The Sombrero galaxy (M 104, NGC 4594) is associated with one of the nearest low-luminosity active galactic nuclei (AGNs). We investigated the detailed radio structure of the Sombrero nucleus using high-resolution, quasi-simultaneous, multi-frequency, phase-referencing Very Long Baseline Array observations. We obtained high-quality images of this nucleus at seven frequencies, where those at 15, 24, and 43 GHz are the first clear very long baseline interferometry detections. At 43 GHz, the nuclear structure was imaged on a linear scale under 0.01 pc or 100 Schwarzschild radii, revealing a compact, high-brightness-temperature (≳ 3 × 10{sup 9} K) radio core. We discovered the presence of the extended structure emanating from the core on two sides in the northwest and southeast directions. The nuclear radio spectra show a clear spatial gradient, which is similar to that seen in more luminous AGNs with powerful relativistic jets. Moreover, the size and position of the core tend to be frequency dependent. These findings provide evidence that the central engine of the Sombrero is powering radio jets and the jets are overwhelming the emission from the underlying radiatively inefficient accretion flow over the observed frequencies. Based on these radio characteristics, we constrained the following physical parameters for the M 104 jets: (1) the northern side is approaching, whereas the southern one is receding; (2) the jet viewing angle is relatively close to our line-of-sight (≲ 25°); and (3) the intrinsic jet velocity is highly sub-relativistic (≲ 0.2c). The derived pole-on nature of the M 104 jets is consistent with the previous argument that this nucleus contains a true type II AGN, i.e., the broad line region is actually absent or intrinsically weak if the plane of the circumnuclear torus is perpendicular to the jet axis.

  13. Ionized outflows in luminous type 2 AGNs at z < 0.6: no evidence for significant impact on the host galaxies

    NASA Astrophysics Data System (ADS)

    Villar-Martín, M.; Arribas, S.; Emonts, B.; Humphrey, A.; Tadhunter, C.; Bessiere, P.; Cabrera Lavers, A.; Ramos Almeida, C.

    2016-07-01

    We investigate the presence of extended ionized outflows in 18 luminous type 2 AGNs (11 quasars and 7 high-luminosity Seyfert 2s) at 0.3 < z < 0.6 based on VLT-FORS2 spectroscopy. We infer typical lower limits on the radial sizes of the outflows Ro ≳ several × 100 pc and upper limits Ro ≲ 1-2 kpc. Our results are inconsistent with related studies which suggest that large scale (Ro ˜ several-15 kpc) are ubiquitous in QSO2. We study the possible causes of discrepancy and propose that seeing smearing is the cause of the large inferred sizes. The implications in our understanding of the feedback phenomenon are important since the mass Mo (through the density), mass injection skew3dot{M}_o and energy injection dot{E}_o rates of the outflows become highly uncertain. One conclusion seems unavoidable: Mo, skew3dot{M}_o and dot{E}_o are modest or low compared with previous estimations. We obtain typically Mo ≲ (0.4-22) × 106 M⊙ (median 1.1 × 106 M⊙) assuming n = 1000 cm-3. These are ˜102-104 times lower than values reported in the literature. Even under the most favourable assumptions, we obtain \\dot{M}_o ≲ 10 M⊙ yr-1 in general, 100-1000 times lower than claimed in related studies. Although the uncertainties are large, it is probable that these are lower than typical star-forming rates. In conclusion, no evidence is found supporting that typical outflows can affect the interstellar medium of the host galaxies across spatial scales ≳ 1-2 kpc.

  14. The Swift GRB Host Galaxy Legacy Survey. II. Rest-frame Near-IR Luminosity Distribution and Evidence for a Near-solar Metallicity Threshold

    NASA Astrophysics Data System (ADS)

    Perley, D. A.; Tanvir, N. R.; Hjorth, J.; Laskar, T.; Berger, E.; Chary, R.; de Ugarte Postigo, A.; Fynbo, J. P. U.; Krühler, T.; Levan, A. J.; Michałowski, M. J.; Schulze, S.

    2016-01-01

    We present rest-frame near-IR (NIR) luminosities and stellar masses for a large and uniformly selected population of gamma-ray burst (GRB) host galaxies using deep Spitzer Space Telescope imaging of 119 targets from the Swift GRB Host Galaxy Legacy Survey spanning 0.03 < z < 6.3, and we determine the effects of galaxy evolution and chemical enrichment on the mass distribution of the GRB host population across cosmic history. We find a rapid increase in the characteristic NIR host luminosity between z ˜ 0.5 and z ˜ 1.5, but little variation between z ˜ 1.5 and z ˜ 5. Dust-obscured GRBs dominate the massive host population but are only rarely seen associated with low-mass hosts, indicating that massive star-forming galaxies are universally and (to some extent) homogeneously dusty at high redshift while low-mass star-forming galaxies retain little dust in their interstellar medium. Comparing our luminosity distributions with field surveys and measurements of the high-z mass-metallicity relation, our results have good consistency with a model in which the GRB rate per unit star formation is constant in galaxies with gas-phase metallicity below approximately the solar value but heavily suppressed in more metal-rich environments. This model also naturally explains the previously reported “excess” in the GRB rate beyond z ≳ 2 metals stifle GRB production in most galaxies at z < 1.5 but have only minor impact at higher redshifts. The metallicity threshold we infer is much higher than predicted by single-star models and favors a binary progenitor. Our observations also constrain the fraction of cosmic star formation in low-mass galaxies undetectable to Spitzer to be small at z < 4.

  15. Dark Times for the Fluffiest Galaxies

    NASA Astrophysics Data System (ADS)

    Romanowsky, Aaron J.; Beasley, Michael A.; Burkert, Andreas; Abraham, Roberto G.; Brodie, Jean P.; Deich, Aaron; Martin-navarro, Ignacio; Martinez-Delgado, David; Pota, Vincenzo; Rider, Nicole; Sandoval, Michael; Santhanakrishnan, Vakini; Stone, Maria; Van Dokkum, Pieter G.

    2016-06-01

    Ultra-diffuse galaxies (UDGs) were recently recognized as an abundant class of low-surface brightness galaxies with unusually large sizes -- found both in galaxy clusters and in the field. The nature and origins of these galaxies are unclear, with one intriguing possibility that some of them are "failed Milky Ways" with massive halos but a paucity of stars. I will present observations of stars and globular clusters in UDGs that constrain their stellar populations and masses -- including evidence for being ultra-rich in dark matter. I will also show results from simulations of UDG formation through ram-pressure stripping of gas-rich disk galaxies.

  16. Microvariability in Seyfert galaxies

    USGS Publications Warehouse

    Carini, M.T.; Noble, J.C.; Miller, H.R.

    2003-01-01

    We present the results of a search for microvariability in a sample of eight Seyfert galaxies. Microvariability (i.e., variations occurring on timescales of tens of minutes to hours) has been conclusively demonstrated to exist in the class of active galactic nuclei (AGNs) known as blazars. Its existence in other classes of AGNs is far less certain. We present the results of a study of eight Seyfert 1 galaxies, which were intensively monitored in order to determine whether such variations exist in these objects. Only one object, Ark 120, displayed any evidence of microvariations. The implications of these results with respect to current models of the mechanisms responsible for the observed emission in Seyfert galaxies are discussed. We compare our results with those obtained from other studies of microvariability in different classes of AGNs.

  17. Recovery of lotic macroinvertebrate communities from disturbance

    NASA Astrophysics Data System (ADS)

    Wallace, J. Bruce

    1990-09-01

    Ecosystem disturbances produce changes in macrobenthic community structure (abundances, biomass, and production) that persist for a few weeks to many decades. Examples of disturbances with extremely long-term effects on benthic communities include contamination by persistent toxic agents, physical changes in habitats, and altered energy inputs. Stream size, retention, and local geomorphology may ameliorate the influence of disturbances on invertebrates. Disturbances can alter food webs and may select for favorable genotypes (e.g., insecticidal resistance). Introductions of pesticides into lotic ecosystems, which do not result in major physical changes within habitats, illustrate several factors that influence invertebrate recovery time from disturbance. These include: (1) magnitude of original contamination, toxicity, and extent of continued use; (2) spatial scale of the disturbance; (3) persistence of the pesticide; (4) timing of the contamination in relation to the life history stages of the organisms; (5) vagility of populations influenced by pesticides; and (6) position within the drainage network. The ability of macroinvertebrates to recolonize denuded stream habitats may vary greatly depending on regional life histories, dispersal abilities, and position within the stream network (e.g., headwaters vs larger rivers). Although downstream drift is the most frequently cited mechanism of invertebrate recolonization following disturbance in middle- and larger-order streams, evidence is presented that shows aerial recolonization to be potentially important in headwater streams. There is an apparent stochastic element operating for aerial recolonization, depending on the timing of disturbance and flight periods of various taxa. Available evidence indicates that recolonization of invertebrate taxa without an aerial adult stage requires longer periods of time than for those that possess winged, terrestrial adult stages (i.e., most insects). Innovative, manipulative

  18. Ionospheric disturbance dynamo

    SciTech Connect

    Blanc, M.; Richmond, A.D.

    1980-04-01

    A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbanc dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the midlatitude thermosphere, or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E x B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an 'anti-Sq' type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of distrubance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E x B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes.

  19. Dusty Feedback from Massive Black Holes in Two Elliptical Galaxies

    NASA Technical Reports Server (NTRS)

    Temi, P.; Brighenti, F.; Mathews, W. G.; Amblard, A.; Riguccini, L.

    2013-01-01

    Far-infrared dust emission from elliptical galaxies informs us about galaxy mergers, feedback energy outbursts from supermassive black holes and the age of galactic stars. We report on the role of AGN feedback observationally by looking for its signatures in elliptical galaxies at recent epochs in the nearby universe. We present Herschel observations of two elliptical galaxies with strong and spatially extended FIR emission from colder grains 5-10 kpc distant from the galaxy cores. Extended excess cold dust emission is interpreted as evidence of recent feedback-generated AGN energy outbursts in these galaxies, visible only in the FIR, from buoyant gaseous outflows from the galaxy cores.

  20. Internal dynamics of the galaxy cluster Abell 545. The ideal case where to study the simultaneous formation of a galaxy system and its brightest galaxy

    NASA Astrophysics Data System (ADS)

    Barrena, R.; Girardi, M.; Boschin, W.; de Grandi, S.; Eckert, D.; Rossetti, M.

    2011-05-01

    Context. The mechanisms giving rise to diffuse radio emission in galaxy clusters, and in particular their connection with cluster mergers, are still debated. Aims: We seek to explore the internal dynamics of the cluster Abell 545, which has been shown to host a radio halo. Abell 545 is also peculiar for hosting in its center a very bright, red, diffuse intracluster light due to an old, presumably metal-rich stellar population, so bright to be named as "star pile". Methods: Our analysis is mainly based on redshift data for 110 galaxies acquired at the Telescopio Nazionale Galileo. We identify 95 cluster members and analyze the cluster internal dynamics by combining galaxy velocities and positions. We also use both multiband photometric data acquired at the Isaac Newton Telescope and X-ray data from the XMM-Newton Science Archive. Results: We estimate the cluster redshift, ⟨ z ⟩ = 0.1580, a large line-of-sight (LOS) velocity dispersion σV ~ 1200 km s-1, and ICM temperature kTX ~ 8 keV. Our optical and X-ray analyses detect substructures. Optical data reveal three main galaxy clumps (one at the center hosting the peak of X-ray emission; one at NNW, and one at NE); and possibly a fourth clump at South. There is not a dominant galaxy and the four brightest galaxies avoid the cluster core - ≳ 0.4 h70-1 Mpcdistant from the cluster center - and are ≳ 1500 km s-1far from the mean cluster velocity. Two of these brightest galaxies are located in the NNW and NE clumps. The analysis of the X-ray surface brightness distribution provides us evidence of a disturbed dynamical phase: the strong NNW-SSE elongation, a western excess, and a sharp discontinuity in the northern region which is the likely signature of a shock. Located in the star pile region there is the brightest galaxy of the cluster core (CBCG) and a very compact elliptical galaxy, likely a M32-like dwarf. We show that the star pile, which has a previously determined redshift, has a similar redshift to that of

  1. Les galaxies

    NASA Astrophysics Data System (ADS)

    Combes, Francoise

    2016-08-01

    Considerable progress has been made on galaxy formation and evolution in recent years, and new issues. The old Hubble classification according to the tuning fork of spirals, lenticulars and ellipticals, is still useful but has given place to the red sequence, the blue cloud and the green valley, showing a real bimodality of types between star forming galaxies (blue) and quenched ones (red). Large surveys have shown that stellar mass and environment density are the two main factors of the evolution from blue to red sequences. Evolution is followed directly with redshift through a look-back time of more than 12 billion years. The most distant galaxy at z=11. has already a stellar mass of a billion suns. In an apparent anti-hierarchical scenario, the most massive galaxies form stars early on, while essentially dwarf galaxies are actively star-formers now. This downsizing feature also applies to the growth of super-massive black holes at the heart of each bulgy galaxy. The feedback from active nuclei is essential to explain the distribution of mass in galaxies, and in particular to explain why the fraction of baryonic matter is so low, lower by more than a factor 5 than the baryonic fraction of the Universe. New instruments just entering in operation, like MUSE and ALMA, provide a new and rich data flow, which is developed in this series of articles.

  2. Giant radio galaxies and cosmic web

    NASA Astrophysics Data System (ADS)

    Heinämäki, Pekka

    2016-10-01

    Giant radio galaxies create the welldistinguishable class of sources.These sources are characterized with edge-brightened radio lobes withhighly collimated radio jets and large linear sizes which make themthe largest individual structures in the Universe. They are also knownto be hosted by elliptical/disturbed host galaxies and avoid clustersand high galaxy density regions. Because of GRG, large linear sizeslobes extend well beyond the interstellar media and host galaxyhalo the evolution of the radio lobes may depend on interactionwith this environment. Using our method to extract filamentarystructure of the galaxies in our local universe we study whetherradio lobe properties in some giant radio galaxies are determinedon an interaction of this filament ambient.

  3. Galactic surveys: Small galaxies are growing smaller

    NASA Astrophysics Data System (ADS)

    Phillipps, Steve

    2004-12-01

    Galaxies are not always giant collections of billions of stars. Since the 1930s, when Harlow Shapley discovered the first dwarf spheroidal galaxies, technology has allowed the detection of ever fainter galaxies in our immediate neighbourhood. Our galaxy is now known to have a whole retinue of very small satellite galaxies, the lowest luminosity examples of which can hardly outshine one massive star. Some galaxies appear to be getting physically smaller. Evidence for this is found in the streams of stars detected around our galaxy and elsewhere and in galaxies that appear to have had their outer regions truncated. Recent surveys of galaxy clusters have revealed another new class of object, the ultra-compact dwarfs. Though no less luminous than other dwarf galaxies, their physical sizes, of order 20 pc, are far below anything previously seen. They are reminiscent of the nuclei of dE,N type galaxies and may well be descended from them via some destructive processes within galaxy clusters.

  4. Probing the tides in interacting galaxy pairs

    NASA Technical Reports Server (NTRS)

    Borne, Kirk D.

    1990-01-01

    Detailed spectroscopic and imaging observations of colliding elliptical galaxies revealed unmistakable diagnostic signatures of the tidal interactions. It is possible to compare both the distorted luminosity distributions and the disturbed internal rotation profiles with numerical simulations in order to model the strength of the tidal gravitational field acting within a given pair of galaxies. Using the best-fit numerical model, one can then measure directly the mass of a specific interacting binary system. This technique applies to individual pairs and therefore complements the classical methods of measuring the masses of galaxy pairs in well-defined statistical samples. The 'personalized' modeling of galaxy pairs also permits the derivation of each binary's orbit, spatial orientation, and interaction timescale. Similarly, one can probe the tides in less-detailed observations of disturbed galaxies in order to estimate some of the physical parameters for larger samples of interacting galaxy pairs. These parameters are useful inputs to the more universal problems of (1) the galaxy merger rate, (2) the strength and duration of the driving forces behind tidally stimulated phenomena (e.g., starbursts and maybe quasi steller objects), and (3) the identification of long-lived signatures of interaction/merger events.

  5. "Dead quasars" in nearby galaxies?

    PubMed

    Rees, M J

    1990-02-16

    The nuclei of some galaxies undergo violent activity, quasars being the most extreme instances of this phenomenon. Such activity is probably short-lived compared to galactic lifetimes, and was most prevalent when the universe was only about one-fifth of its present age. A massive black hole seems the inevitable end point of such activity, and dead quasars should greatly outnumber active ones. In recent years, studies of stellar motions in the cores of several nearby galaxies indicate the presence of central dark masses which could be black holes. This article discusses how such evidence might be corroborated, and the potential implications for our understanding of active galaxies and black holes.

  6. CONFIRMATION OF ENHANCED DWARF-SENSITIVE ABSORPTION FEATURES IN THE SPECTRA OF MASSIVE ELLIPTICAL GALAXIES: FURTHER EVIDENCE FOR A NON-UNIVERSAL INITIAL MASS FUNCTION

    SciTech Connect

    Van Dokkum, Pieter G.; Conroy, Charlie

    2011-07-01

    We recently found that massive cluster elliptical galaxies have strong Na I {lambda}8183, 8195 and FeH {lambda}9916 Wing-Ford band absorption, indicating the presence of a very large population of stars with masses {approx}< 0.3 M{sub sun}. Here we test this result by comparing the elliptical galaxy spectra to those of luminous globular clusters associated with M31. These globular clusters have similar metallicities, abundance ratios, and ages as massive elliptical galaxies but their low dynamical mass-to-light ratios rule out steep stellar initial mass functions (IMFs). From high-quality Keck spectra we find that the dwarf-sensitive absorption lines in globular clusters are significantly weaker than in elliptical galaxies and consistent with normal IMFs. The differences in the Na I and Wing-Ford indices are 0.027 {+-} 0.007 mag and 0.017 {+-} 0.006 mag, respectively. We directly compare the two classes of objects by subtracting the averaged globular cluster spectrum from the averaged elliptical galaxy spectrum. The difference spectrum is well fit by the difference between a stellar population synthesis model with a bottom-heavy IMF and one with a bottom-light IMF. We speculate that the slope of the IMF may vary with velocity dispersion, although it is not yet clear what physical mechanism would be responsible for such a relation.

  7. EVIDENCE FOR THE UNIVERSALITY OF PROPERTIES OF RED-SEQUENCE GALAXIES IN X-RAY- AND RED-SEQUENCE-SELECTED CLUSTERS AT z ∼ 1

    SciTech Connect

    Foltz, R.; Wilson, G.; DeGroot, A.; Rettura, A.; Van der Burg, R. F. J.; Lidman, C.; Demarco, R.; Nantais, Julie; Yee, H. E-mail: gillian.wilson@ucr.edu E-mail: arettura@astro.caltech.edu E-mail: avmuzzin@ast.cam.ac.uk E-mail: rdemarco@astro-udec.cl E-mail: hyee@astro.utoronto.ca

    2015-10-20

    We study the slope, intercept, and scatter of the color–magnitude and color–mass relations for a sample of 10 infrared red-sequence-selected clusters at z ∼ 1. The quiescent galaxies in these clusters formed the bulk of their stars above z ≳ 3 with an age spread Δt ≳ 1 Gyr. We compare UVJ color–color and spectroscopic-based galaxy selection techniques, and find a 15% difference in the galaxy populations classified as quiescent by these methods. We compare the color–magnitude relations from our red-sequence selected sample with X-ray- and photometric-redshift-selected cluster samples of similar mass and redshift. Within uncertainties, we are unable to detect any difference in the ages and star formation histories of quiescent cluster members in clusters selected by different methods, suggesting that the dominant quenching mechanism is insensitive to cluster baryon partitioning at z ∼ 1.

  8. Evidence for the Universality of Properties of Red-sequence Galaxies in X-Ray- and Red-Sequence-Selected Clusters at z ~ 1

    NASA Astrophysics Data System (ADS)

    Foltz, R.; Rettura, A.; Wilson, G.; van der Burg, R. F. J.; Muzzin, A.; Lidman, C.; Demarco, R.; Nantais, Julie; DeGroot, A.; Yee, H.

    2015-10-01

    We study the slope, intercept, and scatter of the color-magnitude and color-mass relations for a sample of 10 infrared red-sequence-selected clusters at z ˜ 1. The quiescent galaxies in these clusters formed the bulk of their stars above z ≳ 3 with an age spread Δt ≳ 1 Gyr. We compare UVJ color-color and spectroscopic-based galaxy selection techniques, and find a 15% difference in the galaxy populations classified as quiescent by these methods. We compare the color-magnitude relations from our red-sequence selected sample with X-ray- and photometric-redshift-selected cluster samples of similar mass and redshift. Within uncertainties, we are unable to detect any difference in the ages and star formation histories of quiescent cluster members in clusters selected by different methods, suggesting that the dominant quenching mechanism is insensitive to cluster baryon partitioning at z ˜ 1.

  9. Deficiency of "Thin" Stellar Bars in Seyfert Host Galaxies.

    PubMed

    Shlosman; Peletier; Knapen

    2000-06-01

    Using all available major samples of Seyfert galaxies and their corresponding closely matched control samples of nonactive galaxies, we find that the bar ellipticities (or axial ratios) in Seyfert galaxies are systematically different from those in nonactive galaxies. Overall, there is a deficiency of bars with large ellipticities (i.e., "thin" or "strong" bars) in Seyfert galaxies compared to nonactive galaxies. Accompanied with a large dispersion due to small number statistics, this effect is strictly speaking at the 2 sigma level. To obtain this result, the active galaxy samples of near-infrared surface photometry were matched to those of normal galaxies in type, host galaxy ellipticity, absolute magnitude, and, to some extent, redshift. We discuss possible theoretical explanations of this phenomenon within the framework of galactic evolution, and, in particular, of radial gas redistribution in barred galaxies. Our conclusions provide further evidence that Seyfert hosts differ systematically from their nonactive counterparts on scales of a few kiloparsecs.

  10. The X-Ray Luminosity Functions of Field Low-Mass X-Ray Binaries in Early-Type Galaxies: Evidence for a Stellar Age Dependence

    NASA Technical Reports Server (NTRS)

    Lehmer, B. D.; Berkeley, M.; Zezas, A.; Alexander, D. M.; Basu-Zych, A.; Bauer, F. E.; Brandt, W. N.; Fragos, T.; Hornschemeier, A. E.; Kalogera, V.; Ptak, A.; Sivakoff, G. R.; Tzanavaris, P.; Yukita, M.

    2014-01-01

    We present direct constraints on how the formation of low-mass X-ray binary (LMXB) populations in galactic fields depends on stellar age. In this pilot study, we utilize Chandra and Hubble Space Telescope (HST) data to detect and characterize the X-ray point source populations of three nearby early-type galaxies: NGC 3115, 3379, and 3384. The luminosity-weighted stellar ages of our sample span approximately equal to 3-10 Gyr. X-ray binary population synthesis models predict that the field LMXBs associated with younger stellar populations should be more numerous and luminous per unit stellar mass than older populations due to the evolution of LMXB donor star masses. Crucially, the combination of deep Chandra and HST observations allows us to test directly this prediction by identifying and removing counterparts to X-ray point sources that are unrelated to the field LMXB populations, including LMXBs that are formed dynamically in globular clusters, Galactic stars, and background AGN/galaxies. We find that the "young" early-type galaxy NGC 3384 (approximately equals 2-5 Gyr) has an excess of luminous field LMXBs (L(sub x) approximately greater than (5-10) × 10(exp 37) erg s(exp -1)) per unit K-band luminosity (L(sub K); a proxy for stellar mass) than the "old" early-type galaxies NGC 3115 and 3379 (approximately equals 8-10 Gyr), which results in a factor of 2-3 excess of L(sub X)/L(sub K) for NGC 3384. This result is consistent with the X-ray binary population synthesis model predictions; however, our small galaxy sample size does not allow us to draw definitive conclusions on the evolution field LMXBs in general. We discuss how future surveys of larger galaxy samples that combine deep Chandra and HST data could provide a powerful new benchmark for calibrating X-ray binary population synthesis models.

  11. The X-ray luminosity functions of field low-mass X-ray binaries in early-type galaxies: Evidence for a stellar age dependence

    SciTech Connect

    Lehmer, B. D.; Tzanavaris, P.; Yukita, M.; Berkeley, M.; Basu-Zych, A.; Hornschemeier, A. E.; Ptak, A.; Zezas, A.; Alexander, D. M.; Bauer, F. E.; Brandt, W. N.; Fragos, T.; Kalogera, V.; Sivakoff, G. R.

    2014-07-01

    We present direct constraints on how the formation of low-mass X-ray binary (LMXB) populations in galactic fields depends on stellar age. In this pilot study, we utilize Chandra and Hubble Space Telescope (HST) data to detect and characterize the X-ray point source populations of three nearby early-type galaxies: NGC 3115, 3379, and 3384. The luminosity-weighted stellar ages of our sample span ≈3-10 Gyr. X-ray binary population synthesis models predict that the field LMXBs associated with younger stellar populations should be more numerous and luminous per unit stellar mass than older populations due to the evolution of LMXB donor star masses. Crucially, the combination of deep Chandra and HST observations allows us to test directly this prediction by identifying and removing counterparts to X-ray point sources that are unrelated to the field LMXB populations, including LMXBs that are formed dynamically in globular clusters, Galactic stars, and background active galactic nuclei/galaxies. We find that the 'young' early-type galaxy NGC 3384 (≈2-5 Gyr) has an excess of luminous field LMXBs (L {sub X} ≳ (5-10) × 10{sup 37} erg s{sup –1}) per unit K-band luminosity (L{sub K} ; a proxy for stellar mass) than the 'old' early-type galaxies NGC 3115 and 3379 (≈8-10 Gyr), which results in a factor of ≈2-3 excess of L {sub X}/L{sub K} for NGC 3384. This result is consistent with the X-ray binary population synthesis model predictions; however, our small galaxy sample size does not allow us to draw definitive conclusions on the evolution field LMXBs in general. We discuss how future surveys of larger galaxy samples that combine deep Chandra and HST data could provide a powerful new benchmark for calibrating X-ray binary population synthesis models.

  12. Galaxy Zoo: Mergers - Dynamical models of interacting galaxies

    NASA Astrophysics Data System (ADS)

    Holincheck, Anthony J.; Wallin, John F.; Borne, Kirk; Fortson, Lucy; Lintott, Chris; Smith, Arfon M.; Bamford, Steven; Keel, William C.; Parrish, Michael

    2016-06-01

    The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of citizen scientists, we sample 105 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the simulation parameters generated by the project. They are now publicly available in electronic format at http://data.galaxyzoo.org/mergers.html. Though our best-fitting model parameters are not an exact match to previously published models, our method for determining uncertainty measurements will aid future comparisons between models. The dynamical clocks from our models agree with previous results of the time since the onset of star formation from starburst models in interacting systems and suggest that tidally induced star formation is triggered very soon after closest approach.

  13. Sleep Disturbances in Schizophrenia.

    PubMed

    Kamath, Jayesh; Virdi, Sundeep; Winokur, Andrew

    2015-12-01

    Sleep disturbances are prevalent in patients with schizophrenia and play a critical role in the morbidity and mortality associated with the illness. Subjective and objective assessments of sleep in patients with schizophrenia have identified certain consistent findings. Findings related to the sleep structure abnormalities have shown correlations with important clinical aspects of the illness. Disruption of specific neurotransmitter systems and dysregulation of clock genes may play a role in the pathophysiology of schizophrenia-related sleep disturbances. Antipsychotic medications play an important role in the treatment of sleep disturbances in these patients and have an impact on their sleep structure.

  14. U-Th-Pb geochronology of the Massabesic Gneiss and the granite near Milford, South-Central New Hampshire: New evidence for avalonian basement and taconic and alleghenian disturbances in Eastern New England

    USGS Publications Warehouse

    Aleinikoff, J.N.; Zartman, R.E.; Lyons, J.B.

    1979-01-01

    U-Th-Pb systematics for zircon and monazite from Massabesic Gneiss (paragneiss and orthogneiss) and the granite near Milford, New Hampshire, were determined. Zircon morphology suggests that the paragneiss may be volcaniclastic (igneous) in origin, and thus the age data probably record the date (minimum of 646 m.y.) at which the rock was extruded. A two-stage lead-loss model is proposed to explain the present array of data points on a concordia diagram. Orthogneiss ages range only narrowly and are clustered around 475 m.y. Data for the granite of Milford, New Hampshire, are scattered, but may be interpreted in terms of inheritance and modern lead loss, yielding a crystallization age of 275 m.y. This is the only known occurrence of Avalonian-type basement in New Hampshire and as such provides evidence for the location of the paleo-Africa-paleo- North America suture. The geochronology also further documents the occurrence of disturbances during the Ordovician and Permian. ?? 1979 Springer-Verlag.

  15. Disturbance and change in biodiversity

    PubMed Central

    Dornelas, Maria

    2010-01-01

    Understanding how disturbance affects biodiversity is important for both fundamental and applied reasons. Here, I investigate how disturbances with different ecological effects change biodiversity metrics. I define three main types of disturbance effects: D disturbance (shifts in mortality rate), B disturbance (shifts in reproductive rates) and K disturbance (shifts in carrying capacity). Numerous composite disturbances can be defined including any combination of these three types of ecological effects. The consequences of D, B and K disturbances, as well as of composite DBK disturbances are examined by comparing metrics before and after a disturbance, in disturbed and undisturbed communities. I use simulations of neutral communities and examine species richness, total abundance and species abundance distributions. The patterns of change in biodiversity metrics are consistent among different types of disturbance. K disturbance has the most severe effects, followed by D disturbance, and B disturbance has nearly negligible effects. Consequences of composite DBK disturbances are more complex than any of the three types of disturbance, with unimodal relationships along a disturbance gradient arising when D, B and K are negatively correlated. Importantly, regardless of disturbance type, community isolation enhances the negative consequences and hinders the positive effects of disturbances. PMID:20980319

  16. Star formation in dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Dong, Shawfeng

    In this thesis, we examine the star formation history and stellar feedback effects of dwarf galaxies under the influence of extragalactic ultraviolet radiation, as well as the evolution of residual gas within tidally-limited dwarf galaxies and globular clusters. Previous work has indicated that the background UV flux can easily ionize the gas within typical dwarf galaxies, delaying or even preventing cooling and star formation within them. Many dwarf galaxies within the Local Group are, however, observed to contain multiple generations of stars, the oldest of which formed in the early epochs of cosmic evolution, when the background UV flux was intense. In order to address this paradox, we consider the dynamical evolution of gas in dwarf galaxies using a one-dimensional, spherically symmetric, Lagrangian numerical scheme which also computes the effects of radiative transfer and photoionization. We include in the scheme a physically-motivated star formation recipe and consider the effects of feedback. This scheme allows us to follow the history of the gas and of star formation within dwarf galaxies, as influenced by both external and internal UV radiation. Our results indicate that star formation in the severe environment of dwarf galaxies is a difficult and inefficient process. In potentials with total mass less than a few 106 M⊙ , and velocity dispersion less than a few km s-1 , residual gas is efficiently photoionized by cosmic background UV radiation. For intermediate mass systems, such as the dSphs around the Galaxy, star formation can proceed within early cosmic epochs despite the intense background UV flux. Triggering processes such as merger events, collisions, and tidal disturbance can lead to density enhancements, reducing the recombination timescale, allowing gas to cool and star formation to proceed. However, the star formation and gas retention efficiency may vary widely in galaxies with similar dark matter potentials, because they depend on many

  17. AGN Feedback in Galaxy Groups: A Joint GMRT/X-ray Study

    NASA Astrophysics Data System (ADS)

    Giacintucci, S.; Vrtilek, J. M.; O'Sullivan, E.; Raychaudhury, S.; David, L. P.; Venturi, T.; Athreya, R.; Gitti, M.

    2009-12-01

    We present an ongoing study of 18 nearby galaxy groups, chosen for the availability of Chandra and/or XMM-Newton data and evidence for AGN/hot intragroup gas interaction. We have obtained 235 and 610 MHz observations at the GMRT for all the groups, and 327 and 150 MHz for a few. We discuss two interesting cases-NGC 5044 and AWM 4-which exhibit different kinds of AGN/hot gas interaction. With the help of these examples we show how joining low-frequency radio data (to track the history of AGN outbursts through emission from aged electron populations) with X-ray data (to determine the state of hot gas, its disturbances, heating and cooling) can provide a unique insight into the nature of the feedback mechanism in galaxy groups.

  18. New southern galaxies with active nuclei

    SciTech Connect

    Maia, M.A.G.; Da costa, L.N.; Willmer, C.; Pellegrini, P.S.; Rite, C.

    1987-03-01

    A list of AGN candidates, identified from optical spectra taken as part of an ongoing redshift survey of southern galaxies, is presented. The identification, coordinates, morphological type, measured heliocentric radial velocity, and proposed emission type are given for the galaxies showing evidence of nonstellar nuclear activity. Using standard diagnostics, several new Seyferts and low-ionization nuclear-emission regions (LINERs) are identified among the emission-line galaxies observed. 14 references.

  19. Testing galaxy formation models with galaxy stellar mass functions

    NASA Astrophysics Data System (ADS)

    Lim, S. H.; Mo, H. J.; Lan, Ting-Wen; Ménard, Brice

    2016-10-01

    We compare predictions of a number of empirical models and numerical simulations of galaxy formation to the conditional stellar mass functions (CSMF) of galaxies in groups of different masses obtained recently by Lan et al. to test how well different models accommodate the data. The observational data clearly prefer a model in which star formation in low-mass halos changes behavior at a characteristic redshift zc ˜ 2. There is also tentative evidence that this characteristic redshift depends on environment, becoming zc ˜ 4 in regions that eventually evolve into rich clusters of galaxies. The constrained model is used to understand how galaxies form and evolve in dark matter halos, and to make predictions for other statistical properties of the galaxy population, such as the stellar mass functions of galaxies at high z, the star formation and stellar mass assembly histories in dark matter halos. A comparison of our model predictions with those of other empirical models shows that different models can make vastly different predictions, even though all of them are tuned to match the observed stellar mass functions of galaxies.

  20. Further evidence of a global carbon cycle disturbance at the Silurian-Devonian boundary: A study of the δ13C record in the eastern-most Central Appalachian Basin (Ulster County, New York)

    NASA Astrophysics Data System (ADS)

    Jost, A. B.; Gillikin, D. P.; Gröcke, D. R.

    2008-12-01

    The Silurian-Devonian (Pridoli-Lochkovian) boundary has been scrutinized and researched more than any other boundary worldwide, and within the last fifteen years, a large carbon isotope disturbance over the boundary has been noted in Europe, Australia, and parts of North America. In this study, a carbon isotope analysis across the Silurian-Devonian boundary in the upper Rondout/Lower Helderberg carbonate sequences of the eastern-most Appalachian Basin has revealed a +2.6 per mil excursion over the transition (approximately 5 m of material), suggesting that the S-D carbon cycle disturbances measured elsewhere are indeed related. δ13C values for the studied section range from +0.6 per mil to +4.8 per mil. Sampling has revealed some variability limited to and directly below the excursion, with values ranging from +2.4 per mil to +4.8 per mil. Following the excursion, δ13C values level off around +1.3 per mil, before gradually increasing to around +2.8 per mil. Samples were also analyzed for δ18O, but early diagenesis appears to have altered these values. Given the positive δ13C values, and correlation with sections from around the world, the carbon isotopes in these samples are thought to have remained unaffected by diagensis. Additionally, the discovery of the positive excursion (noted at two sites approximately 20 km apart) suggests that the S-D boundary exists within the Upper Thatcher/Lower Ravena members of the Manlius/Coeymans Formations of the Helderberg Group. Regional unconformities and limited biostratigraphic records have allowed the precise location of the boundary to remain debatable; however, the addition of chemostratigraphic evidence supports an Upper Thatcher/Lower Ravena location for the transition. Many studies hypothesize that the excursion is related to heightened surface water productivity following a rapid sea-level regression and increased input of phosphate into ocean waters. Understanding of the S-D event is critical in understanding the

  1. EVIDENCE OF VERY LOW METALLICITY AND HIGH IONIZATION STATE IN A STRONGLY LENSED, STAR-FORMING DWARF GALAXY AT z = 3.417

    SciTech Connect

    Amorín, R.; Grazian, A.; Castellano, M.; Pentericci, L.; Fontana, A.; Sommariva, V.; Merlin, E.; Van der Wel, A.; Maseda, M.

    2014-06-10

    We investigate the gas-phase metallicity and Lyman continuum (LyC) escape fraction of a strongly gravitationally lensed, extreme emission-line galaxy at z = 3.417, J1000+0221S, recently discovered by the CANDELS team. We derive ionization- and metallicity-sensitive emission-line ratios from H+K band Large Binocular Telescope (LBT)/LUCI medium resolution spectroscopy. J1000+0221S shows high ionization conditions, as evidenced by its enhanced [O III]/[O II] and [O III]/Hβ ratios. Strong-line methods based on the available line ratios suggest that J1000+0221S is an extremely metal-poor galaxy, with a metallicity of 12+log (O/H) < 7.44 (Z < 0.05 Z {sub ☉}), placing it among the most metal-poor star-forming galaxies at z ≳ 3 discovered so far. In combination with its low stellar mass (2 × 10{sup 8} M {sub ☉}) and high star formation rate (5 M {sub ☉} yr{sup –1}), the metallicity of J1000+0221S is consistent with the extrapolation of the mass-metallicity relation traced by Lyman-break galaxies at z ≳ 3 to low masses, but it is 0.55 dex lower than predicted by the fundamental metallicity relation at z ≲ 2.5. These observations suggest a rapidly growing galaxy, possibly fed by massive accretion of pristine gas. Additionally, deep LBT/LBC photometry in the UGR bands are used to derive a limit to the LyC escape fraction, thus allowing us to explore for the first time the regime of sub-L* galaxies at z > 3. We find a 1σ upper limit to the escape fraction of 23%, which adds a new observational constraint to recent theoretical models predicting that sub-L* galaxies at high-z have high escape fractions and thus are the responsible for the reionization of the universe.

  2. Cosmic Collisions: Galaxy Mergers and Evolution

    NASA Astrophysics Data System (ADS)

    Trouille, Laura; Willett, Kyle; Masters, Karen; Lintott, Christopher; Whyte, Laura; Lynn, Stuart; Tremonti, Christina A.

    2014-08-01

    Over the years evidence has mounted for a significant mode of galaxy evolution via mergers. This process links gas-rich, spiral galaxies; starbursting galaxies; active galactic nuclei (AGN); post-starburst galaxies; and gas-poor, elliptical galaxies, as objects representing different phases of major galaxy mergers. The post-starburst phase is particularly interesting because nearly every galaxy that evolves from star-forming to quiescent must pass through it. In essence, this phase is a sort of galaxy evolution “bottleneck” that indicates that a galaxy is actively evolving through important physical transitions. In this talk I will present the results from the ‘Galaxy Zoo Quench’ project - using post-starburst galaxies to place observational constraints on the role of mergers and AGN activity in quenching star formation. `Quench’ is the first fully collaborative research project with Zooniverse citizen scientists online; engaging the public in all phases of research, from classification to data analysis and discussion to writing the article and submission to a refereed journal.

  3. Metal-poor, Cool Gas in the Circumgalactic Medium of a z = 2.4 Star-forming Galaxy: Direct Evidence for Cold Accretion?

    NASA Astrophysics Data System (ADS)

    Crighton, Neil H. M.; Hennawi, Joseph F.; Prochaska, J. Xavier

    2013-10-01

    In our current galaxy formation paradigm, high-redshift galaxies are predominantly fueled by accretion of cool, metal-poor gas from the intergalactic medium. Hydrodynamical simulations predict that this material should be observable in absorption against background sightlines within a galaxy's virial radius, as optically thick Lyman limit systems (LLSs) with low metallicities. Here we report the discovery of exactly such a strong metal-poor absorber at an impact parameter R = 58 kpc from a star-forming galaxy at z = 2.44. Besides strong neutral hydrogen (N_{{H}^0}=10^{19.50+/- 0.16}\\, cm^{-2}) we detect neutral deuterium and oxygen, allowing a precise measurement of the metallicity: log10(Z/Z ⊙) = -2.0 ± 0.17, or (7-15) × 10-3 solar. Furthermore, the narrow deuterium linewidth requires a cool temperature <20,000 K. Given the striking similarities between this system and the predictions of simulations, we argue that it represents the direct detection of a high-redshift cold-accretion stream. The low-metallicity gas cloud is a single component of an absorption system exhibiting a complex velocity, ionization, and enrichment structure. Two other components have metallicities >0.1 solar, 10 times larger than the metal-poor component. We conclude that the photoionized circumgalactic medium (CGM) of this galaxy is highly inhomogeneous: the majority of the gas is in a cool, metal-poor and predominantly neutral phase, but the majority of the metals are in a highly ionized phase exhibiting weak neutral hydrogen absorption but strong metal absorption. If such inhomogeneity is common, then high-resolution spectra and detailed ionization modeling are critical to accurately appraise the distribution of metals in the high-redshift CGM. .

  4. HST/COS SPECTRA OF THREE QSOs THAT PROBE THE CIRCUMGALACTIC MEDIUM OF A SINGLE SPIRAL GALAXY: EVIDENCE FOR GAS RECYCLING AND OUTFLOW

    SciTech Connect

    Keeney, Brian A.; Stocke, John T.; Danforth, Charles W.; Shull, J. Michael; Green, James C.; Rosenberg, Jessica L.; Ryan-Weber, Emma V.; Savage, Blair D.

    2013-03-01

    We have used the Cosmic Origins Spectrograph (COS) to obtain far-UV spectra of three closely spaced QSO sight lines that probe the circumgalactic medium (CGM) of an edge-on spiral galaxy, ESO 157-49, at impact parameters of 74 and 93 h {sup -1} {sub 70} kpc near its major axis and 172 h {sup -1} {sub 70} kpc along its minor axis. H I Ly{alpha} absorption is detected at the galaxy redshift in the spectra of all three QSOs, and metal lines of Si III, Si IV, and C IV are detected along the two major-axis sight lines. Photoionization models of these clouds suggest metallicities close to the galaxy metallicity, cloud sizes of {approx}1 kpc, and gas masses of {approx}10{sup 4} M {sub Sun }. Given the high covering factor of these clouds, ESO 157-49 could harbor {approx}2 Multiplication-Sign 10{sup 9} M {sub Sun} of warm CGM gas. We detect no metals in the sight line that probes the galaxy along its minor axis, but gas at the galaxy metallicity would not have detectable metal absorption with ionization conditions similar to the major-axis clouds. The kinematics of the major-axis clouds favor these being portions of a 'galactic fountain' of recycled gas, while two of the three minor-axis clouds are constrained geometrically to be outflowing gas. In addition, one of our QSO sight lines probes a second more distant spiral, ESO 157-50, along its major axis at an impact parameter of 88 h {sup -1} {sub 70} kpc. Strong H I Ly{alpha} and C IV absorption only are detected in the QSO spectrum at the redshift of ESO 157-50.

  5. METAL-POOR, COOL GAS IN THE CIRCUMGALACTIC MEDIUM OF A z = 2.4 STAR-FORMING GALAXY: DIRECT EVIDENCE FOR COLD ACCRETION?

    SciTech Connect

    Crighton, Neil H. M.; Hennawi, Joseph F.; Prochaska, J. Xavier

    2013-10-20

    In our current galaxy formation paradigm, high-redshift galaxies are predominantly fueled by accretion of cool, metal-poor gas from the intergalactic medium. Hydrodynamical simulations predict that this material should be observable in absorption against background sightlines within a galaxy's virial radius, as optically thick Lyman limit systems (LLSs) with low metallicities. Here we report the discovery of exactly such a strong metal-poor absorber at an impact parameter R = 58 kpc from a star-forming galaxy at z = 2.44. Besides strong neutral hydrogen (N{sub H{sup 0}}=10{sup 19.50±0.16} cm{sup -2}) we detect neutral deuterium and oxygen, allowing a precise measurement of the metallicity: log{sub 10}(Z/Z {sub ☉}) = –2.0 ± 0.17, or (7-15) × 10{sup –3} solar. Furthermore, the narrow deuterium linewidth requires a cool temperature <20,000 K. Given the striking similarities between this system and the predictions of simulations, we argue that it represents the direct detection of a high-redshift cold-accretion stream. The low-metallicity gas cloud is a single component of an absorption system exhibiting a complex velocity, ionization, and enrichment structure. Two other components have metallicities >0.1 solar, 10 times larger than the metal-poor component. We conclude that the photoionized circumgalactic medium (CGM) of this galaxy is highly inhomogeneous: the majority of the gas is in a cool, metal-poor and predominantly neutral phase, but the majority of the metals are in a highly ionized phase exhibiting weak neutral hydrogen absorption but strong metal absorption. If such inhomogeneity is common, then high-resolution spectra and detailed ionization modeling are critical to accurately appraise the distribution of metals in the high-redshift CGM.

  6. FIR statistics of paired galaxies

    NASA Technical Reports Server (NTRS)

    Sulentic, Jack W.

    1990-01-01

    Much progress has been made in understanding the effects of interaction on galaxies (see reviews in this volume by Heckman and Kennicutt). Evidence for enhanced emission from galaxies in pairs first emerged in the radio (Sulentic 1976) and optical (Larson and Tinsley 1978) domains. Results in the far infrared (FIR) lagged behind until the advent of the Infrared Astronomy Satellite (IRAS). The last five years have seen numerous FIR studies of optical and IR selected samples of interacting galaxies (e.g., Cutri and McAlary 1985; Joseph and Wright 1985; Kennicutt et al. 1987; Haynes and Herter 1988). Despite all of this work, there are still contradictory ideas about the level and, even, the reality of an FIR enhancement in interacting galaxies. Much of the confusion originates in differences between the galaxy samples that were studied (i.e., optical morphology and redshift coverage). Here, the authors report on a study of the FIR detection properties for a large sample of interacting galaxies and a matching control sample. They focus on the distance independent detection fraction (DF) statistics of the sample. The results prove useful in interpreting the previously published work. A clarification of the phenomenology provides valuable clues about the physics of the FIR enhancement in galaxies.

  7. Uncovering Blue Diffuse Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    James, Bethan; Koposov, Sergey; Stark, Daniel; Belokurov, Vasily; Pettini, Max; Olszewski, Edward W.

    2015-01-01

    Extremely metal-poor galaxies (XMPs) and the star-formation within their chemically pristine environments are fundamental to our understanding of the galaxy formation process at early times. However, traditional emission-line surveys detect only the brightest metal-poor galaxies where star-formation occurs in compact, starbursting environments, and thereby give us only a partial view of the dwarf galaxy population. To avoid such biases, we have developed a new search algorithm based on the morphological, rather then spectral, properties of XMPs and have applied to the Sloan Digital Sky Survey database of images. Using this novel approach, we have discovered ~100 previously undetected, faint blue galaxies, each with isolated HII regions embedded in a diffuse continuum. In this talk I will present the first results from follow-up optical spectroscopy of this sample, which reveals these blue diffuse dwarfs (BDDs) to be young, very metal-poor and actively forming stars despite their intrinsically low luminosities. I will present evidence showing that BDDs appear to bridge the gap between quiescent dwarf irregular (dIrr) galaxies and blue compact galaxies (BCDs) and as such offer an ideal opportunity to assess how star-formation occurs in more `normal' metal-poor systems.

  8. Galaxies in extreme environments: Isolated galaxies versus compact groups

    NASA Astrophysics Data System (ADS)

    Durbala, Adriana

    2009-06-01

    . In spite of long standing theoretical predictions of a major merger of the galaxy members into a giant one, we find evidence that compact groups are in fact long-lived and form by sequential acquisition of galaxies, coalescing via slow dissolution.

  9. Internal kinematics of modelled interacting disc galaxies

    NASA Astrophysics Data System (ADS)

    Kronberger, T.; Kapferer, W.; Schindler, S.; Böhm, A.; Kutdemir, E.; Ziegler, B. L.

    2006-10-01

    We present an investigation of galaxy-galaxy interactions and their effects on the velocity fields of disc galaxies in combined N-body/hydrodynamic simulations, which include cooling, star formation with feedback, and galactic winds. Rotation curves (RCs) of the gas are extracted from these simulations in a way that follows the procedure applied to observations of distant, small, and faint galaxies as closely as possible. We show that galaxy-galaxy mergers and fly-bys disturb the velocity fields significantly and hence the RCs of the interacting galaxies, leading to asymmetries and distortions in the RCs. Typical features of disturbed kinematics are significantly rising or falling profiles in the direction of the companion galaxy and pronounced bumps in the RCs. In addition, tidal tails can leave strong imprints on the rotation curve. All these features are observable for intermediate redshift galaxies, on which we focus our investigations. We use a quantitative measure for the asymmetry of rotation curves to show that the appearance of these distortions strongly depends on the viewing angle. We also find in this way that the velocity fields settle back into relatively undisturbed equilibrium states after unequal mass mergers and fly-bys. About 1 Gyr after the first encounter, the RCs show no severe distortions anymore. These results are consistent with previous theoretical and observational studies. As an illustration of our results, we compare our simulated velocity fields and direct images with rotation curves from VLT/FORS spectroscopy and ACS images of a cluster at z=0.53 and find remarkable similarities.

  10. Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Miller, Christopher J. Miller

    2012-03-01

    There are many examples of clustering in astronomy. Stars in our own galaxy are often seen as being gravitationally bound into tight globular or open clusters. The Solar System's Trojan asteroids cluster at the gravitational Langrangian in front of Jupiter’s orbit. On the largest of scales, we find gravitationally bound clusters of galaxies, the Virgo cluster (in the constellation of Virgo at a distance of ˜50 million light years) being a prime nearby example. The Virgo cluster subtends an angle of nearly 8◦ on the sky and is known to contain over a thousand member galaxies. Galaxy clusters play an important role in our understanding of theUniverse. Clusters exist at peaks in the three-dimensional large-scale matter density field. Their sky (2D) locations are easy to detect in astronomical imaging data and their mean galaxy redshifts (redshift is related to the third spatial dimension: distance) are often better (spectroscopically) and cheaper (photometrically) when compared with the entire galaxy population in large sky surveys. Photometric redshift (z) [Photometric techniques use the broad band filter magnitudes of a galaxy to estimate the redshift. Spectroscopic techniques use the galaxy spectra and emission/absorption line features to measure the redshift] determinations of galaxies within clusters are accurate to better than delta_z = 0.05 [7] and when studied as a cluster population, the central galaxies form a line in color-magnitude space (called the the E/S0 ridgeline and visible in Figure 16.3) that contains galaxies with similar stellar populations [15]. The shape of this E/S0 ridgeline enables astronomers to measure the cluster redshift to within delta_z = 0.01 [23]. The most accurate cluster redshift determinations come from spectroscopy of the member galaxies, where only a fraction of the members need to be spectroscopically observed [25,42] to get an accurate redshift to the whole system. If light traces mass in the Universe, then the locations

  11. Galaxy Cluster Takes It to the Extreme

    NASA Astrophysics Data System (ADS)

    2007-05-01

    Evidence for an awesome upheaval in a massive galaxy cluster was discovered in an image made by NASA's Chandra X-ray Observatory. The origin of a bright arc of ferociously hot gas extending over two million light years requires one of the most energetic events ever detected. The cluster of galaxies is filled with tenuous gas at 170 million degree Celsius that is bound by the mass equivalent of a quadrillion, or 1,000 trillion, suns. The temperature and mass make this cluster a giant among giants. VLA Radio Image of 3C438 VLA Radio Image of 3C438 "The huge feature detected in the cluster, combined with the high temperature, points to an exceptionally dramatic event in the nearby Universe," said Ralph Kraft of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., and leader of a team of astronomers involved in this research. "While we're not sure what caused it, we've narrowed it down to a couple of exciting possibilities." The favored explanation for the bright X-ray arc is that two massive galaxy clusters are undergoing a collision at about 4 million miles per hour. Shock waves generated by the violent encounter of the clusters' hot gas clouds could produce a sharp change in pressure along the boundary where the collision is occurring, giving rise to the observed arc-shaped structure which resembles a titanic weather front. "Although this would be an extreme collision, one of the most powerful ever seen, we think this may be what is going on," said team member Martin Hardcastle, of the University of Hertfordshire, United Kingdom. Images of 3C438 and Surrounding Galaxy Cluster Images of 3C438 and Surrounding Galaxy Cluster A problem with the collision theory is that only one peak in the X-ray emission is seen, whereas two are expected. Longer observations with Chandra and the XMM-Newton X-ray observatories should help determine how serious this problem is for the collision hypothesis. Another possible explanation is that the disturbance was

  12. Hydrological disturbance diminishes predator control in wetlands.

    PubMed

    Dorn, Nathan J; Cook, Mark I

    2015-11-01

    Effects of predators on prey populations can be especially strong in aquatic ecosystems, but disturbances may mediate the strength of predator limitation and even allow outbreaks of some prey populations. In a two-year study we investigated the numerical responses of crayfish (Procambarus fallax) and small fishes (Poeciliidae and Fundulidae) to a brief hydrological disturbance in replicated freshwater wetlands with an experimental drying and large predatory fish reduction. The experiment and an in situ predation assay tested the component of the consumer stress model positing that disturbances release prey from predator limitation. In the disturbed wetlands, abundances of large predatory fish were seasonally reduced, similar to dynamics in the Everglades (southern Florida). Densities of small fish were unaffected by the disturbance, but crayfish densities, which were similar across all wetlands before drying, increased almost threefold in the year after the disturbance. Upon re-flooding, juvenile crayfish survival was inversely related to the abundance of large fish across wetlands, but we found no evidence for enhanced algal food quality. At a larger landscape scale (500 km2 of the Everglades), crayfish densities over eight years were positively correlated with the severity of local dry disturbances (up to 99 days dry) during the preceding dry season. In contrast, densities of small-bodied fishes in the same wetlands were seasonally depressed by dry disturbances. The results from our experimental wetland drought and the observations of crayfish densities in the Everglades represent a large-scale example of prey population release following a hydrological disturbance in a freshwater ecosystem. The conditions producing crayfish pulses in the Everglades appear consistent with the mechanics of the consumer stress model, and we suggest crayfish pulses may influence the number of nesting wading birds in the Everglades.

  13. Hydrological disturbance diminishes predator control in wetlands.

    PubMed

    Dorn, Nathan J; Cook, Mark I

    2015-11-01

    Effects of predators on prey populations can be especially strong in aquatic ecosystems, but disturbances may mediate the strength of predator limitation and even allow outbreaks of some prey populations. In a two-year study we investigated the numerical responses of crayfish (Procambarus fallax) and small fishes (Poeciliidae and Fundulidae) to a brief hydrological disturbance in replicated freshwater wetlands with an experimental drying and large predatory fish reduction. The experiment and an in situ predation assay tested the component of the consumer stress model positing that disturbances release prey from predator limitation. In the disturbed wetlands, abundances of large predatory fish were seasonally reduced, similar to dynamics in the Everglades (southern Florida). Densities of small fish were unaffected by the disturbance, but crayfish densities, which were similar across all wetlands before drying, increased almost threefold in the year after the disturbance. Upon re-flooding, juvenile crayfish survival was inversely related to the abundance of large fish across wetlands, but we found no evidence for enhanced algal food quality. At a larger landscape scale (500 km2 of the Everglades), crayfish densities over eight years were positively correlated with the severity of local dry disturbances (up to 99 days dry) during the preceding dry season. In contrast, densities of small-bodied fishes in the same wetlands were seasonally depressed by dry disturbances. The results from our experimental wetland drought and the observations of crayfish densities in the Everglades represent a large-scale example of prey population release following a hydrological disturbance in a freshwater ecosystem. The conditions producing crayfish pulses in the Everglades appear consistent with the mechanics of the consumer stress model, and we suggest crayfish pulses may influence the number of nesting wading birds in the Everglades. PMID:27070017

  14. Galaxy and Mass Assembly (GAMA): merging galaxies and their properties

    NASA Astrophysics Data System (ADS)

    De Propris, Roberto; Baldry, Ivan K.; Bland-Hawthorn, Joss; Brough, Sarah; Driver, Simon P.; Hopkins, Andrew M.; Kelvin, Lee; Loveday, Jon; Phillipps, Steve; Robotham, Aaron S. G.

    2014-11-01

    We derive the close pair fractions and volume merger rates for galaxies in the Galaxy and Mass Assembly (GAMA) survey with -23 < Mr < -17 (ΩM = 0.27, ΩΛ = 0.73, H0 = 100 km s-1 Mpc-1) at 0.01 < z < 0.22 (look-back time of <2 Gyr). The merger fraction is approximately 1.5 per cent Gyr-1 at all luminosities (assuming 50 per cent of pairs merge) and the volume merger rate is ≈3.5 × 10-4 Mpc-3 Gyr-1. We examine how the merger rate varies by luminosity and morphology. Dry mergers (between red/spheroidal galaxies) are found to be uncommon and to decrease with decreasing luminosity. Fainter mergers are wet, between blue/discy galaxies. Damp mergers (one of each type) follow the average of dry and wet mergers. In the brighter luminosity bin (-23 < Mr < -20), the merger rate evolution is flat, irrespective of colour or morphology, out to z ˜ 0.2. The makeup of the merging population does not appear to change over this redshift range. Galaxy growth by major mergers appears comparatively unimportant and dry mergers are unlikely to be significant in the buildup of the red sequence over the past 2 Gyr. We compare the colour, morphology, environmental density and degree of activity (BPT class, Baldwin, Phillips & Terlevich) of galaxies in pairs to those of more isolated objects in the same volume. Galaxies in close pairs tend to be both redder and slightly more spheroid dominated than the comparison sample. We suggest that this may be due to `harassment' in multiple previous passes prior to the current close interaction. Galaxy pairs do not appear to prefer significantly denser environments. There is no evidence of an enhancement in the AGN fraction in pairs, compared to other galaxies in the same volume.

  15. Disturbance maintains alternative biome states.

    PubMed

    Dantas, Vinícius de L; Hirota, Marina; Oliveira, Rafael S; Pausas, Juli G

    2016-01-01

    Understanding the mechanisms controlling the distribution of biomes remains a challenge. Although tropical biome distribution has traditionally been explained by climate and soil, contrasting vegetation types often occur as mosaics with sharp boundaries under very similar environmental conditions. While evidence suggests that these biomes are alternative states, empirical broad-scale support to this hypothesis is still lacking. Using community-level field data and a novel resource-niche overlap approach, we show that, for a wide range of environmental conditions, fire feedbacks maintain savannas and forests as alternative biome states in both the Neotropics and the Afrotropics. In addition, wooded grasslands and savannas occurred as alternative grassy states in the Afrotropics, depending on the relative importance of fire and herbivory feedbacks. These results are consistent with landscape scale evidence and suggest that disturbance is a general factor driving and maintaining alternative biome states and vegetation mosaics in the tropics.

  16. Street lighting disturbs commuting bats.

    PubMed

    Stone, Emma Louise; Jones, Gareth; Harris, Stephen

    2009-07-14

    Anthropogenic disturbance is a major cause of worldwide declines in biodiversity. Understanding the implications of this disturbance for species and populations is crucial for conservation biologists wishing to mitigate negative effects. Anthropogenic light pollution is an increasing global problem, affecting ecological interactions across a range of taxa and impacting negatively upon critical animal behaviors including foraging, reproduction, and communication (for review see). Almost all bats are nocturnal, making them ideal subjects for testing the effects of light pollution. Previous studies have shown that bat species adapted to foraging in open environments feed on insects attracted to mercury vapor lamps. Here, we use an experimental approach to provide the first evidence of a negative effect of artificial light pollution on the commuting behavior of a threatened bat species. We installed high-pressure sodium lights that mimic the intensity and light spectra of streetlights along commuting routes of lesser horseshoe bats (Rhinolophus hipposideros). Bat activity was reduced dramatically and the onset of commuting behavior was delayed in the presence of lighting, with no evidence of habituation. These results demonstrate that light pollution may have significant negative impacts upon the selection of flight routes by bats. PMID:19540116

  17. Galaxy interactions and the stimulation of nuclear activity

    NASA Technical Reports Server (NTRS)

    Heckman, Timothy M.

    1990-01-01

    The author discusses the idea that interactions between galaxies can lead to enhanced galactic activity. He discusses whether, apart from the observational evidence, there is a strong theoretical or heuristic motivation for investigating galaxy interactions as stimulators of nuclear activity in galaxies. Galactic interactions as mechanisms for triggering nuclear starbursts are covered.

  18. Two confirmed compact elliptical galaxies in the Antlia cluster

    NASA Astrophysics Data System (ADS)

    Smith Castelli, A. V.; Faifer, F. R.; Bassino, L. P.; Romero, G. A.; Cellone, S. A.; Richtler, T.

    We confirm the existence of two compact elliptical (cE) galaxies in the cen- tral region of the Antlia cluster through MAGELLAN-MIKE and GEMINI- GMOS spectra. Only about a dozen galaxies of this rare type are known today up to a distance of 100 Mpc. With this finding, Antlia becomes the nearest galaxy cluster harbouring more than one cE galaxy among its galaxy population. One of these galaxies shows evidence of interaction with one of the giant ellipticals that dominate the central region of the cluster.

  19. Whirlpool Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Scientists are seeing unprecedented detail of the spiral arms and dust clouds in the nearby Whirlpool galaxy, thanks to a new Hubble Space Telescope image, available at http://www.jpl.nasa.gov/pictures/wfpc/wfpc.html. The image uses data collected January 15 and 24, 1995, and July 21, 1999, by Hubble's Wide Field and Planetary Camera 2, designed and built by JPL. Using the image, a research group led by Dr. Nick Scoville of the California Institute of Technology, Pasadena, clearly defined the structure of the galaxy's cold dust clouds and hot hydrogen, and they linked star clusters within the galaxy to their parent dust clouds.

    The Whirlpool galaxy is one of the most photogenic galaxies. This celestial beauty is easily seen and photographed with smaller telescopes and studied extensively from large ground- and space-based observatories. The new composite image shows visible starlight and light from the emission of glowing hydrogen, which is associated with the most luminous young stars in the spiral arms.

    The galaxy is having a close encounter with a nearby companion galaxy, NGC 5195, just off the upper edge of the image. The companion's gravitational pull is triggering star formation in the main galaxy, lit up by numerous clusters of young and energetic stars in brilliant detail. Luminous clusters are highlighted in red by their associated emission from glowing hydrogen gas.

    This image was composed by the Hubble Heritage Team from Hubble archive data and was superimposed onto data taken by Dr. Travis Rector of the National Optical Astronomy Observatory at the .9-meter (35-inch) telescope at the National Science Foundation's Kitt Peak National Observatory, Tucson, Ariz. Scoville's team includes M. Polletta of the University of Geneva, Switzerland; S. Ewald and S. Stolovy of Caltech; and R. Thompson and M. Rieke of the University of Arizona, Tucson.

    The Space Telescope Science Institute, Baltimore, Md., manages space operations for the Hubble Space

  20. SLOSHING COLD FRONTS IN GALAXY GROUPS AND THEIR PERTURBING DISK GALAXIES: AN X-RAY, OPTICAL, AND RADIO CASE STUDY

    SciTech Connect

    Gastaldello, Fabio; Di Gesu, Laura; Ghizzardi, Simona; Rossetti, Mariachiara; Giacintucci, Simona; Girardi, Marisa; Roediger, Elke; Brighenti, Fabrizio; Buote, David A.; Humphrey, Philip J.; Eckert, Dominique; Ettori, Stefano; Mathews, William G.

    2013-06-10

    We present a combined X-ray, optical, and radio analysis of the galaxy group IC 1860 using the currently available Chandra and XMM data, multi-object spectroscopy data from the literature, and Giant Metrewave Radio Telescope (GMRT) data. The Chandra and XMM imaging and spectroscopy reveal two surface brightness discontinuities at 45 and 76 kpc shown to be consistent with a pair of cold fronts. These features are interpreted as due to sloshing of the central gas induced by an off-axis minor merger with a perturber. This scenario is further supported by the presence of a peculiar velocity of the central galaxy IC 1860 and the identification of a possible perturber in the optically disturbed spiral galaxy IC 1859. The identification of the perturber is consistent with the comparison with numerical simulations of sloshing. The GMRT observation at 325 MHz shows faint, extended radio emission contained within the inner cold front, as seen in some galaxy clusters hosting diffuse radio mini-halos. However, unlike mini-halos, no particle reacceleration is needed to explain the extended radio emission, which is consistent with aged radio plasma redistributed by the sloshing. There is a strong analogy between the X-ray and optical phenomenology of the IC 1860 group and that of two other groups, NGC 5044 and NGC 5846, showing cold fronts. The evidence presented in this paper is among the strongest supporting the currently favored model of cold-front formation in relaxed objects and establishes the group scale as a chief environment for studying this phenomenon.

  1. Hidden interaction in SBO galaxies

    NASA Technical Reports Server (NTRS)

    Galletta, G.; Bettoni, D.; Oosterloo, T.; Fasano, G.

    1990-01-01

    Galaxies, like plants, show a large variety of grafts: an individual of some type connects physically with a neighborhood of same or different type. The effects of these interactions between galaxies have a broad range of morphologies depending, among other quantities, on the distance of the closest approach between systems and the relative size of the two galaxies. A sketch of the possible situations is shown in tabular form. This botanical classification is just indicative, because the effects of interactions can be notable also at relatively large separations, when additional conditions are met, as for example low density of the interacting systems or the presence of intra-cluster gas. In spite of the large variety of encounters and effects, in the literature the same terms are often used to refer to different types of interactions. Analysis indicates that only few of the situations show evident signs of interaction. They appear to be most relevant when the size of the two galaxies is comparable. Bridges and tails, like the well known case of NGC 4038/39, the Antennae, are only observed for a very low percentage of all galaxies (approx. 0.38 percent, Arp and Madore 1977). In most cases of gravitational bond between two galaxies, the effects of interactions are not relevant or evident. For instance, the detection of stellar shells (Malin and Carter 1983), which have been attributed to the accretion of gas stripped from another galaxy or to the capture and disruption of a small stellar system (Quinn 1984), requires particular observing and reduction techniques. Besides these difficulties of detection, time plays an important role in erasing, within a massive galaxy, the effects of interactions with smaller objects. This can happen on a timescale shorter than the Hubble time, so the number of systems now showing signs of interaction suggests lower limits to the true frequency of interactions in the life-time of a stellar system.

  2. 1992 system disturbances

    SciTech Connect

    Not Available

    1993-10-01

    When a utility experiences an electric system emergency that requires reporting to the DOE, the utility sends a copy of the report to its Regional Council, which then sends a copy to NERC. Canadian utilities often voluntarily file emergency reports to DOE and NERC as well. NERC's annual review of system disturbances begins in November when the Disturbance Analysis Working Group meets to discuss each disturbance reported to NERC so far that year. The Group then contacts the Regional Council or utility(ies) involved and requests a detailed report of each incident. The Group then summarizes the report for this Review and analyzes it using the NERC Operating Guides and Planning Policies and Guides as the analysis categories. The Commentary section includes the conclusions and recommendations that were formulated from the analyses in this report plus the general experiences of the Working Group through the years. In 1992, utilities reported 22 incidents of system disturbances, load reductions, or unusual occurrences. This is eight fewer than reported in 1991. These incidents are listed chronologically and categorized as: fourteen system interruptions that resulted in loss of customer service, eight unusual occurrences that did not cause a service interruption. No public appeals to reduce demand or voltage reductions occurred in 1992. This document contains reports of 11 incidents plus a summary of the damage from Hurricane Andrew. Each utility or Region approved its analysis in this report. Included is a table of Disturbances by Analysis Category that offers a quick review of the categories applicable to each incident.

  3. Observational evidence that massive cluster galaxies were forming stars at z ~ 2.5 and did not grow in mass at later times

    NASA Astrophysics Data System (ADS)

    Andreon, S.

    2013-06-01

    Using Spitzer 3.6 micron data we derived the luminosity function and the mass function of galaxies in five z > 1.4 clusters selected to have a firm intracluster medium detection. The five clusters differ in richness (ISCS J1438.1+3414 and XMMXCS J2215.9-1738 are twice as rich as ISCS J1432.4+3250, IDCS J1426.5+3508, and JKCS 041) and morphological appareance. At the median redshift z = 1.5, from the 150 member galaxies of the five clusters, we derived a characteristic magnitude of 16.92 ± 0.13 in the [3.6] band and a characteristic mass of lg M∗ = 11.30 ± 0.05 M⊙. We find that the characteristic luminosity and mass does not evolve between z = 1 and 1.4 < z < 1.8, directly ruling out ongoing mass assembly between these epochs because massive galaxies are already present up to z = 1.8. Lower-redshift build-up epochs have already been ruled out by previous works, leaving only z > 1.8 as a possible epoch for the mass build up. However, the observed values of m∗ at very high redshift are too bright for galaxies without any star formation immediately preceding the observed redshift and therefore imply a star formation episode not earlier than zf = 2.5. For the first time, mass/luminosity functions are able to robustly distinguish tiny differences between formation redshifts and to set upper limits to the epoch of the last star-formation episode.

  4. Properties of QSO Metal-line Absorption Systems at High Redshifts: Nature and Evolution of the Absorbers and New Evidence on Escape of Ionizing Radiation from Galaxies

    NASA Astrophysics Data System (ADS)

    Boksenberg, Alec; Sargent, Wallace L. W.

    2015-05-01

    Using Voigt-profile-fitting procedures on Keck High Resolution Spectrograph spectra of nine QSOs, we identify 1099 C IV absorber components clumped in 201 systems outside the Lyman forest over 1.6 <~ z <~ 4.4. With associated Si IV, C II, Si II and N V where available, we investigate the bulk statistical and ionization properties of the components and systems and find no significant change in redshift for C IV and Si IV while C II, Si II and N V change substantially. The C IV components exhibit strong clustering, but no clustering is detected for systems on scales from 150 km s-1 out to 50,000 km s-1. We conclude that the clustering is due entirely to the peculiar velocities of gas present in the circumgalactic media of galaxies. Using specific combinations of ionic ratios, we compare our observations with model ionization predictions for absorbers exposed to the metagalactic ionizing radiation background augmented by proximity radiation from their associated galaxies and find that the generally accepted means of radiative escape by transparent channels from the internal star-forming sites is spectrally not viable for our stronger absorbers. We develop an active scenario based on runaway stars with resulting changes in the efflux of radiation that naturally enable the needed spectral convergence, and in turn provide empirical indicators of morphological evolution in the associated galaxies. Together with a coexisting population of relatively compact galaxies indicated by the weaker absorbers in our sample, the collective escape of radiation is sufficient to maintain the intergalactic medium ionized over the full range 1.9 < z <~ 4.4. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck

  5. PROPERTIES OF QSO METAL-LINE ABSORPTION SYSTEMS AT HIGH REDSHIFTS: NATURE AND EVOLUTION OF THE ABSORBERS AND NEW EVIDENCE ON ESCAPE OF IONIZING RADIATION FROM GALAXIES

    SciTech Connect

    Boksenberg, Alec; Sargent, Wallace L. W.

    2015-05-15

    Using Voigt-profile-fitting procedures on Keck High Resolution Spectrograph spectra of nine QSOs, we identify 1099 C IV absorber components clumped in 201 systems outside the Lyman forest over 1.6 ≲ z ≲ 4.4. With associated Si IV, C II, Si II  and N V where available, we investigate the bulk statistical and ionization properties of the components and systems and find no significant change in redshift for C IV and Si IV while C II, Si II  and N V change substantially. The C IV components exhibit strong clustering, but no clustering is detected for systems on scales from 150 km s{sup –1} out to 50,000 km s{sup –1}. We conclude that the clustering is due entirely to the peculiar velocities of gas present in the circumgalactic media of galaxies. Using specific combinations of ionic ratios, we compare our observations with model ionization predictions for absorbers exposed to the metagalactic ionizing radiation background augmented by proximity radiation from their associated galaxies and find that the generally accepted means of radiative escape by transparent channels from the internal star-forming sites is spectrally not viable for our stronger absorbers. We develop an active scenario based on runaway stars with resulting changes in the efflux of radiation that naturally enable the needed spectral convergence, and in turn provide empirical indicators of morphological evolution in the associated galaxies. Together with a coexisting population of relatively compact galaxies indicated by the weaker absorbers in our sample, the collective escape of radiation is sufficient to maintain the intergalactic medium ionized over the full range 1.9 < z ≲ 4.4.

  6. The galaxy luminosity function at z ≃ 6 and evidence for rapid evolution in the bright end from z ≃ 7 to 5

    NASA Astrophysics Data System (ADS)

    Bowler, R. A. A.; Dunlop, J. S.; McLure, R. J.; McCracken, H. J.; Milvang-Jensen, B.; Furusawa, H.; Taniguchi, Y.; Le Fèvre, O.; Fynbo, J. P. U.; Jarvis, M. J.; Häußler, B.

    2015-09-01

    We present the results of a search for bright (-22.7 ≤ MUV ≤ -20.5) Lyman-break galaxies at z ≃ 6 within a total of 1.65 deg2 of imaging in the UltraVISTA/Cosmological Evolution Survey (COSMOS) and United Kingdom Infrared Telescope Deep Sky Survey (UKIDSS) Ultra Deep Survey (UDS) fields. The deep near-infrared imaging available in the two independent fields, in addition to deep optical (including z'-band) data, enables the sample of z ≃ 6 star-forming galaxies to be securely detected longward of the break (in contrast to several previous studies). We show that the expected contamination rate of our initial sample by cool Galactic brown dwarfs is ≲3 per cent and demonstrate that they can be effectively removed by fitting brown dwarf spectral templates to the photometry. At z ≃ 6, the galaxy surface density in the UltraVISTA field exceeds that in the UDS by a factor of ≃ 1.8, indicating strong cosmic variance even between degree-scale fields at z > 5. We calculate the bright end of the rest-frame Ultraviolet (UV) luminosity function (LF) at z ≃ 6. The galaxy number counts are a factor of ˜1.7 lower than predicted by the recent LF determination by Bouwens et al. In comparison to other smaller area studies, we find an evolution in the characteristic magnitude between z ≃ 5 and z ≃ 7 of ΔM* ˜ 0.4, and show that a double power law or a Schechter function can equally well describe the LF at z = 6. Furthermore, the bright end of the LF appears to steepen from z ≃ 7 to z ≃ 5, which could indicate the onset of mass quenching or the rise of dust obscuration, a conclusion supported by comparing the observed LFs to a range of theoretical model predictions.

  7. AGN feedback in galaxy clusters and groups

    NASA Astrophysics Data System (ADS)

    Hardcastle, Martin

    2016-07-01

    Mechanical feedback via Active Galactic Nuclei (AGN) jets in the centres of galaxy groups and clusters is a crucial ingredient in current models of galaxy formation and cluster evolution. Jet feedback is believed to regulate gas cooling and thus star formation in the most massive galaxies, but a robust physical understanding of this feedback mode is currently lacking. Athena will provide (1) the first kinematic measurements on relevant spatial scales of the hot gas in galaxy, group and cluster haloes as it absorbs the impact of AGN jets, and (2) vastly improved ability to map thermodynamic conditions on scales well-matched to the jets, lobes and gas disturbances produced by them. I will present new predictions of Athena's ability to measure the energetic impact of powerful jets based on our most recent set of numerical models.

  8. IUE observations of amorphous hot galaxies

    NASA Technical Reports Server (NTRS)

    Lamb, S. A.; Hjellming, M. S.; Gallagher, J. S., III; Hunter, D. A.

    1985-01-01

    Blue amorphous galaxies are star-forming, irregularlike systems which lack the spatially distinct OB stellar groups that are characteristic of most late-type galaxies. In order to better understand the nature of star-formation processes in these unusual galaxies, short-wavelength IUE spectra of the amorphous galaxies NGC 1705 and NGC 1800 have been obtained. It is found that NGC 1705 contains a normal mix of OB stars, which is consistent with the nearly constant recent star-formation rate inferred from new optical data. NGC 1800 is likely to have similar properties, and blue galaxies with amorphous structures thus do not show evidence for anomalies in stellar populations. The UV spectra of these galaxies and a variety of other hot extragalactic stellar systems in fact have similar characteristics, which suggests OB stellar populations are often homogeneous in their properties.

  9. Extended Source/Galaxy All Sky 2

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This panoramic view encompasses the entire sky and reveals the distribution of galaxies beyond the Milky Way galaxy, which astronomers call extended sources, as observed by Two Micron All-Sky Survey. The image is assembled from a database of over 1.6 million galaxies listed in the survey's All-Sky Survey Extended Source Catalog,; more than half of the galaxies have never before been catalogued. The colors represent how the many galaxies appear at three distinct wavelengths of infrared light (blue at 1.2 microns, green at 1.6 microns, and red at 2.2 microns). Quite evident are the many galactic clusters and superclusters, as well as some streamers composing the large-scale structure of the nearby universe. The blue overlay represents the very close and bright stars from our own Milky Way galaxy. In this projection, the bluish Milky Way lies predominantly toward the upper middle and edges of the image.

  10. Central star formation in S0 galaxies

    NASA Technical Reports Server (NTRS)

    Dressel, L. L.; Oconnell, R. W.; Telesco, C. M.

    1990-01-01

    As a class, S0 galaxies are characterized by a lack of resolved bright stars in the disk. However, several lines of evidence support the hypothesis that a high rate of star formation is occurring at the centers of some S0 galaxies. Many of the warmest, most powerful far infrared sources in nearby bright galaxies occur in S0 galaxies. (Dressel 1988, Ap. J., 329, L69). The ratios of radio continuum flux to far infrared flux for these S0 galaxies are comparable to the ratios found for spiral galaxy disks and for star-burst galaxies. Very Large Array (VLA) maps of some of these S0 galaxies show that the radio continuum emission originates in the central few kiloparsecs. It is diffuse or clumpy, unlike the radio sources in active S0 galaxies, which are either extremely compact or have jet-lobe structures. Imaging of some of these galaxies at 10.8 microns shows that the infrared emission is also centrally concentrated. Many of the infrared-powerful S0 galaxies are Markarian galaxies. In only one case in this sample is the powerful ultraviolet emission known to be generated by a Seyfert nucleus. Optical spectra of the central few kiloparsecs of these S0 galaxies generally show deep Balmer absorption lines characteristic of A stars, and H beta emission suggestive of gas heated by O stars. A key question to our understanding of these galaxies is whether they really are S0 galaxies, or at least would have been recognized as S0 galaxies before the episode of central star formation began. Some of Nilson's classifications (used here) have been confirmed by Sandage or de Vaucouleurs and collaborators from better plates; some of the galaxies may be misclassified Sa galaxies (the most frequent hosts of central star formation); some are apparently difficult to classify because of mixed characteristics, faint non-S0 features, or peculiarities. More optical imaging is needed to characterize the host galaxies and to study the evolution of their star-forming regions.

  11. "Galaxy," Defined

    NASA Astrophysics Data System (ADS)

    Willman, B.; Strader, J.

    2012-09-01

    A growing number of low luminosity and low surface brightness astronomical objects challenge traditional notions of both galaxies and star clusters. To address this challenge, we propose a definition of galaxy that does not depend on a cold dark matter model of the universe: a galaxy is a gravitationally bound collection of stars whose properties cannot be explained by a combination of baryons and Newton's laws of gravity. After exploring several possible observational diagnostics of this definition, we critically examine the classification of ultra-faint dwarfs, globular clusters, ultra-compact dwarfs, and tidal dwarfs. While kinematic studies provide an effective diagnostic of the definition in many regimes, they can be less useful for compact or very faint systems. To explore the utility of using the [Fe/H] spread as a complementary diagnostic, we use published spectroscopic [Fe/H] measurements of 16 Milky Way dwarfs and 24 globular clusters to uniformly calculate their [Fe/H] spreads and associated uncertainties. Our principal results are (1) no known, old star cluster less luminous than MV = -10 has a significant (gsim0.1 dex) spread in its iron abundance; (2) known ultra-faint dwarf galaxies can be unambiguously classified with a combination of kinematic and [Fe/H] observations; (3) the observed [Fe/H] spreads in massive (gsim 106 M ⊙) globular clusters do not necessarily imply that they are the stripped nuclei of dwarfs, nor a need for dark matter; and (4) if ultra-compact dwarf galaxies reside in dark matter halos akin to those of ultra-faint dwarfs of the same half-light radii, then they will show no clear dynamical signature of dark matter. We suggest several measurements that may assist the future classification of massive globular clusters, ultra-compact dwarfs, and ultra-faint galaxies. Our galaxy definition is designed to be independent of the details of current observations and models, while our proposed diagnostics can be refined or replaced as

  12. Pharmacology for sleep disturbance in PTSD.

    PubMed

    Lipinska, Gosia; Baldwin, David S; Thomas, Kevin G F

    2016-03-01

    Symptoms of sleep disturbance, particularly nightmares and insomnia, are a central feature of post-traumatic stress disorder (PTSD). Emerging evidence suggests that specific treatment of PTSD-related sleep disturbance improves other symptoms of the disorder, which in turn suggests that such disturbance may be fundamental to development and maintenance of the disorder. This mini-review focuses on pharmacological treatment of sleep disturbance in adult PTSD (specifically, studies testing the efficacy of antidepressants, adrenergic inhibiting agents, antipsychotics and benzodiazepine and non-benzodiazepine hypnotics). We conclude that only prazosin, an adrenergic inhibiting agent, has had its efficacy established by multiple randomised controlled trials. There is also high-level evidence supporting use of eszopiclone, as well as risperidone and olanzapine as adjunct therapy. Antidepressants such as sertraline, venlafaxine and mirtazapine, benzodiazepines such as alprazolam and clonazepam and non-benzodiazepine hypnotics such as zolpidem appear ineffective in treating PTSD-related sleep disturbance. Most studies that report reduced frequency of nightmares and insomnia also report decreases in overall symptom severity. Such findings suggest that (i) sleep disruption is central to PTSD; (ii) treating sleep disruption may be an effective way to address other symptoms of the disorder and (iii) PTSD symptoms tend to cluster together in predictable ways. PMID:26856810

  13. Extragalatic zoo. I. [New galaxies

    SciTech Connect

    Schorn, R.A.

    1988-01-01

    The characteristics of various types of extragalactic objects are described. Consideration is given to cD galaxies, D galaxies, N galaxies, Markarian galaxies, liners, starburst galaxies, and megamasers. Emphasis is also placed on the isolated extragalatic H I region; the isolated extragalatic H II region; primeval galaxies or photogalaxies; peculiar galaxies; Arp galaxies; interacting galaxies; ring galaxies; and polar-ring galaxies. Diagrams of these objects are provided.

  14. Crashing galaxies, cosmic fireworks

    SciTech Connect

    Keel, W.C.

    1989-01-01

    The study of binary systems is reviewed. The history of the study of interacting galaxies, the behavior of gas in binary systems, studies to identify the processes that occur when galaxies interact, and the relationship of Seyfert galaxies and quasars to binary systems are discussed. The development of an atlas of peculiar galaxies (Arp, 1966) and methods for modeling galaxy interactions are examined.

  15. Functioning of Adolescents with Symptoms of Disturbed Sleep.

    ERIC Educational Resources Information Center

    Roberts, Robert E.; Roberts, Catherine R.; Chen, Irene G.

    2001-01-01

    Studied the association between disturbed sleep and the functioning of adolescents, especially cumulative effects across multiple life domains. Results from 5,423 students suggest that adolescents experiencing disturbed sleep also experience a range of deficits in functioning. Available evidence does not make it possible to specify causal…

  16. The Growth of Galaxies over the last 12 Billion Years

    NASA Astrophysics Data System (ADS)

    Mosleh, M.

    2016-09-01

    One of the key unsolved problems in astrophysics is to understand the formation and evolution of galaxies. There are many complementary approaches to study the evolution of galaxies and infer how distant galaxies are connected to galaxies in the present day universe. These canonical ways are either focused on the evolution of luminosity/mass function, star formation rate density, or the evolution of the observed scaling relations of galaxies. Among the scaling relations, the relation between the stellar mass and sizes of galaxies has considerable importance. Evidence is provided by many recent studies that the size of galaxies were smaller at higher redshifts compared to galaxies of similar mass in the local Universe. Studying these galaxy properties at different epochs can place important constrains on the underlying processes assumed for the galaxy mass and structural evolution. I will present the study of the mass-size evolution of galaxies from redshift z=7 to z=1 and the stellar mass-size relation for nearby galaxies (z=0). Also, I will present the stellar mass assembly history of quiescent and star-forming galaxies between z=2 and z=0.5, by studying the radial mass profile of these galaxies.

  17. Dark Galaxies and Lost Baryons (IAU S244)

    NASA Astrophysics Data System (ADS)

    Davies, Jonathan I.; Disney, Michael J.

    2008-05-01

    ; Numerical simulation of the dwarf companions of giant galaxies A. Nelson and P. Williams; Delayed galaxies C. Struck, M. Hancock, B. Smith, P. Appleton, V. Charmandaris and M. Giroux; Probe of dark galaxies via disturbed/lopsided isolated galaxies I. Karachentsev, V. Karachentseva, W. Huchtmeier, D. Makarov and S. Kaisin; Star formation thresholds J. Schaye; Scaling relations of dwarf galaxies without supernova-driven winds K. Tassis, A. Kravtsov and N. Gnedin; Star formation in massive low surface brightness galaxies K. O'Neil; Linking clustering properties and the evolution of low surface brightness galaxies D. Bomans and S. Rosenbaum; Too small to form a galaxy: how the UV background determines the baryon fraction M. Hoeft, G. Yepes and S. Gottlober; Star formation in damped Lyman selected galaxies L. Christensen; Dark-matter content of early-type galaxies with planetary nebulae N. Napolitano et al.; Hunting for ghosts: low surface brightnesses from pixels R. Scaramella and S. Sabatini; Baryonic properties of the darkest galaxies E. Grebel; The dwarf low surface brightness population in different environments of the local universe S. Sabatini, J. Davies, S. Roberts and R. Scaramella; Mass modelling of dwarf spheroidal galaxies J. Klimentowski et al.; Evolution of dwarf galaxies in the Centaurus A Group L. Makarova and D. Makarov; A flat faint end of the Fornax cluster galaxy luminosity function S. Mieske, M. Hilker, L. Infante and C. Mendes de Oliveira; Can massive dark halos destroy the discs of dwarf galaxies? B. Fuchs and O. Esquivel; 'Dark galaxies' and local very metal-poor gas-rich galaxies: possible interrelations S. Pustilnik; Morphology and environment of dwarf galaxies in the local universe H. Ann; Arecibo survey of HI emission from disk galaxies at redshift z 0.2 B. Catinella, M. Haynes, J. Gardner, A. Connolly and R. Giovanelli; AGES observations of

  18. Technical Civilizations in the Galaxy

    NASA Technical Reports Server (NTRS)

    Jones, Harry

    2005-01-01

    Are there other technical civilizations in the galaxy? Past analyses come to different conclusions. Cocconi and Morrison demonstrated in 1959 that interstellar radio communication was possible and Drake conducted the first search for beacons in 1960. The Drake equation estimates the number of galactic civilizations that are transmitting beacons as the product of the rate of star formation in the galaxy, the fraction of stars with planets, their average number of earthlike planets, the fraction with intelligent life and interstellar communication, and the average lifetime of a technical civilization. The Drake model of the galaxy contains many technical civilizations with communication but no interstellar travel. Michael Hart in 1975 strongly challenged this model. Starting with the fact that no extraterrestrials have been observed on Earth, and assuming that interstellar colonization is possible, he concluded that it was very likely that we are the first civilization in our galaxy and that searching or beacons is probably a waste of time and money. The Fermi paradox similarly reasons that if extraterrestrials exist: they should be here, and asks, Where are they? The Hart/Fermi model of the galaxy contains only our civilization and suggests we may colonize the galaxy. A third galactic model is that we are alone but will never develop interstellar travel. The fourth alternate model has many technical civilizations, with interstellar travel and colonization. The possibilities are clear and momentous. Either we are the only technical civilization in the galaxy or there are others. Technical civilizations will colonize the galaxy or not. We have four cosmic conjectures - one or many, colonization or not - but however unlikely they seem based on our limited evidence, one of these four models must be collect.

  19. Radio emission in peculiar galaxies

    NASA Technical Reports Server (NTRS)

    Demellorabaca, Dulia F.; Abraham, Zulema

    1990-01-01

    During the last decades a number of surveys of peculiar galaxies have been carried out and accurate positions become available. Since peculiarities are a possible evidence of radio emission (Wright, 1974; Sulentic, 1976; Stocke et al., 1978), the authors selected a sample of 24 peculiar galaxies with optical jet-like features or extensions in different optical catalogues, mainly the Catalogue of Southern Peculiar Galaxies and Associations (Arp and Madore, 1987) and the ESO/Uppsala Survey of the ESO(B) Atlas (Lauberts, 1982) for observation at the radio continuum frequency of 22 GHz. The sample is listed in a table. Sol (1987) studied this sample and concluded that the majority of the jet-like features seem to admit an explanation in terms of interactive galaxies with bridges and/or tails due to tidal effects. Only in a few cases do the jets seem to be possibly linked to some nuclear activity of the host galaxy. The observations were made with the 13.7m-radome enclosed Itapetinga Radiotelescope (HPBW of 4.3 arcmin), in Brazil. The receiver was a 1 GHz d.s.b. super-heterodine mixer operated in total-power mode, with a system temperature of approximately 800 K. The observational technique consisted in scans in right ascention, centralized in the optical position of the galaxy. The amplitude of one scan was 43 arcmin, and its duration time was 20 seconds. The integration time was at least 2 hours (12 ten-minute observations) and the sensibility limit adopted was an antenna temperature greater than 3 times the r.m.s. error of the baseline determination. Virgo A was used as the calibrator source. Three galaxies were detected for the first time as radio sources and four other known galaxies at low frequencies had their flux densities measured at 22 GHz. The results for these sources are presented.

  20. Secular Evolution in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Kormendy, John

    2013-10-01

    bulges because the latter retain a `memory' of their disky origin. That is, they have one or more characteristics of disks: (1) flatter shapes than those of classical bulges, (2) correspondingly large ratios of ordered to random velocities, (3) small velocity dispersions with respect to the Faber-Jackson correlation between velocity dispersion and bulge luminosity, (4) spiral structure or nuclear bars in the `bulge' part of the light profile, (5) nearly exponential brightness profiles and (6) starbursts. So the cleanest examples of pseudobulges are recognisable. However, pseudo and classical bulges can coexist in the same galaxy. I review two important implications of secular evolution: (1) The existence of pseudobulges highlights a problem with our theory of galaxy formation by hierarchical clustering. We cannot explain galaxies that are completely bulgeless. Galaxy mergers are expected to happen often enough so that every giant galaxy should have a classical bulge. But we observe that bulgeless giant galaxies are common in field environments. We now realise that many dense centres of galaxies that we used to think are bulges were not made by mergers; they were grown out of disks. So the challenge gets more difficult. This is the biggest problem faced by our theory of galaxy formation. (2) Pseudobulges are observed to contain supermassive black holes (BHs), but they do not show the well-known, tight correlations between BH mass and the mass and velocity dispersion of the host bulge. This leads to the suggestion that there are two fundamentally different BH feeding processes. Rapid global inward gas transport in galaxy mergers leads to giant BHs that correlate with host ellipticals and classical bulges, whereas local and more stochastic feeding of small BHs in largely bulgeless galaxies evidently involves too little energy feedback to result in BH-host coevolution. It is an important success of the secular evolution picture that morphological differences can be used to

  1. Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution

    NASA Astrophysics Data System (ADS)

    Saghiha, H.; Hilbert, S.; Schneider, P.; Simon, P.

    2012-11-01

    Context. The gravitational lensing effect provides various ways to study the mass environment of galaxies. Aims: We investigate how galaxy-galaxy(-galaxy) lensing can be used to test models of galaxy formation and evolution. Methods: We consider two semi-analytic galaxy formation models based on the Millennium Run N-body simulation: the Durham model by Bower et al. (2006, MNRAS, 370, 645) and the Garching model by Guo et al. (2011, MNRAS, 413, 101). We generate mock lensing observations for the two models, and then employ Fast Fourier Transform methods to compute second- and third-order aperture statistics in the simulated fields for various galaxy samples. Results: We find that both models predict qualitatively similar aperture signals, but there are large quantitative differences. The Durham model predicts larger amplitudes in general. In both models, red galaxies exhibit stronger aperture signals than blue galaxies. Using these aperture measurements and assuming a linear deterministic bias model, we measure relative bias ratios of red and blue galaxy samples. We find that a linear deterministic bias is insufficient to describe the relative clustering of model galaxies below ten arcmin angular scales. Dividing galaxies into luminosity bins, the aperture signals decrease with decreasing luminosity for brighter galaxies, but increase again for fainter galaxies. This increase is likely an artifact due to too many faint satellite galaxies in massive group and cluster halos predicted by the models. Conclusions: Our study shows that galaxy-galaxy(-galaxy) lensing is a sensitive probe of galaxy evolution.

  2. Galaxy formation.

    PubMed

    Peebles, P J

    1998-01-01

    It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z approximately 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation.

  3. Galaxy formation

    PubMed Central

    Peebles, P. J. E.

    1998-01-01

    It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z ∼ 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation. PMID:9419326

  4. Shaping galaxy evolution with galaxy structure

    NASA Astrophysics Data System (ADS)

    Cheung, Edmond

    A fundamental pursuit of astronomy is to understand galaxy evolution. The enormous scales and complex physics involved in this endeavor guarantees a never-ending journey that has enamored both astronomers and laymen alike. But despite the difficulty of this task, astronomers have still attempted to further this goal. Among of these astronomers is Edwin Hubble. His work, which includes the famous Hubble sequence, has immeasurably influenced our understanding of galaxy evolution. In this thesis, we present three works that continues Hubble's line of study by using galaxy structure to learn about galaxy evolution. First, we examine the dependence of galaxy quiescence on inner galactic structure with the AEGIS/ DEEP2 survey at 0.5In this thesis, we present three works that continues Hubble's line of study by using galaxy structure to learn about galaxy evolution. First, we examine the dependence of galaxy quiescence on inner galactic structure with the AEGIS/ DEEP2 survey at 0.5galaxies from quiescent galaxies. Our method indicates that the inner stellar mass is the most correlated parameter of quenching, implying that the process that quenches galaxies must also buildup their inner structure. Second, we explore the relationship between galactic bars and their host galaxies with Galaxy Zoo 2 at z˜0. The correlations of bar properties and galaxy properties are consistent with simulations of bar formation and evolution, indicating that bars affect their host galaxies. Finally, we investigate whether bars can drive supermassive black hole growth with data from Chandra and Galaxy Zoo: Hubble at 0.2galaxies to a matched sample of inactive, control galaxies shows that there is no statistically significant excess of bars in active hosts. Our result shows that bars are not the primary fueling mechanism of supermassive black hole

  5. Very large geomagnetic disturbance during sunspot cycle 21: A prediction

    NASA Technical Reports Server (NTRS)

    Sargent, H. H., III

    1979-01-01

    Evidence is presented which suggests that very large geomagnetic disturbances (350 gammas or greater at an invariant magnetic latitude of 50 degrees) occur once or twice per sunspot cycle, on the average. There is also some tendency for these disturbances to group in large odd numbered sunspot cycles similar to the current cycle, cycle 21. No such disturbance was noted during the past cycle although a series of major solar flares was observed in August 1972. At least one very large geomagnetic disturbance is expected during the current cycle; a prediction with perhaps serious consequences for electric power companies.

  6. Visceral larva migrans and eosinophilia in an emotionally disturbed child.

    PubMed

    Marcus, L C; Stambler, M

    1979-03-01

    Visceral larva migrans, Entamoeba coli, evidence of latent toxoplasmosis and a history of plumbism were found in an emotionally disturbed, retarded child. Patients with pica should be screened for parasitism and other diseases transmitted orally. PMID:422524

  7. Dwarf spheroidal galaxies: Keystones of galaxy evolution

    NASA Technical Reports Server (NTRS)

    Gallagher, John S., III; Wyse, Rosemary F. G.

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  8. Waveguide disturbance detection method

    DOEpatents

    Korneev, Valeri A.; Nihei, Kurt T.; Myer, Larry R.

    2000-01-01

    A method for detection of a disturbance in a waveguide comprising transmitting a wavefield having symmetric and antisymmetric components from a horizontally and/or vertically polarized source and/or pressure source disposed symmetrically with respect to the longitudinal central axis of the waveguide at one end of the waveguide, recording the horizontal and/or vertical component or a pressure of the wavefield with a vertical array of receivers disposed at the opposite end of the waveguide, separating the wavenumber transform of the wavefield into the symmetric and antisymmetric components, integrating the symmetric and antisymmetric components over a broad frequency range, and comparing the magnitude of the symmetric components and the antisymmetric components to an expected magnitude for the symmetric components and the antisymmetric components for a waveguide of uniform thickness and properties thereby determining whether or not a disturbance is present inside the waveguide.

  9. 300 Area Disturbance Report

    SciTech Connect

    LL Hale; MK Wright; NA Cadoret

    1999-01-07

    The objective of this study was to define areas of previous disturbance in the 300 Area of the U.S. Department of Energy (DOE) Hanford Site to eliminate these areas from the cultural resource review process, reduce cultural resource monitoring costs, and allow cultural resource specialists to focus on areas where subsurface disturbance is minimal or nonexistent. Research into available sources suggests that impacts from excavations have been significant wherever the following construction activities have occurred: building basements and pits, waste ponds, burial grounds, trenches, installation of subsurface pipelines, power poles, water hydrants, and well construction. Beyond the areas just mentioned, substrates in the' 300 Area consist of a complex, multidimen- sional mosaic composed of undisturbed stratigraphy, backfill, and disturbed sediments; Four Geographic Information System (GIS) maps were created to display known areas of disturbance in the 300 Area. These maps contain information gleaned from a variety of sources, but the primary sources include the Hanford GIS database system, engineer drawings, and historic maps. In addition to these maps, several assumptions can be made about areas of disturbance in the 300 Area as a result of this study: o o Buried pipelines are not always located where they are mapped. As a result, cultural resource monitors or specialists should not depend on maps depicting subsurface pipelines for accurate locations of previous disturbance. Temporary roads built in the early 1940s were placed on layers of sand and gravel 8 to 12 in. thick. Given this information, it is likely that substrates beneath these early roads are only minimally disturbed. Building foundations ranged from concrete slabs no more than 6 to 8 in. thick to deeply excavated pits and basements. Buildings constructed with slab foundations are more numerous than may be expected, and minimally disturbed substrates may be expected in these locations. Historic black

  10. Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Pérez-Fournon, I.; Balcells, M.; Moreno-Insertis, F.; Sánchez, F.

    2010-08-01

    Participants; Group photograph; Preface; Acknowledgements; 1. Galaxy formation and evolution: recent progress R. Ellis; 2. Galaxies at high redshift M. Dickinson; 3. High-redshift galaxies: the far-infrared and sub-millimeter view A. Franceschini; 4. Quasar absorption lines J. Bechtold; 5. Stellar population synthesis models at low and high redshift G. Bruzual A.; 6. Elliptical galaxies K. C. Freeman; 7. Disk galaxies K. C. Freeman; 8. Dark matter in disk galaxies K. C. Freeman.

  11. Prevalence of sleep disturbance in patients with low back pain.

    PubMed

    Alsaadi, Saad M; McAuley, James H; Hush, Julia M; Maher, Chris G

    2011-05-01

    Low back pain (LBP) is a common health condition that is often associated with disability, psychological distress and work loss. Worldwide, billions of dollars are expended each year trying to manage LBP, often with limited success. Recently, some researchers have reported that LBP patients also report sleep disturbance as a result of their LBP. However, as most of this evidence was obtained from highly selected groups of patients or from studies with small samples, high quality data on prevalence of sleep disturbance for patients with LBP are lacking. It is also unclear whether sleep disturbance is more likely to be reported by patients with recent-onset LBP than by patients with persistent LBP. Finally, it is not known whether high pain intensity, the most relevant condition-specific variable, is associated with higher rates of reported sleep disturbance. The present study aimed to determine the prevalence of reported sleep disturbance in patients with LBP. In addition, we aimed to determine whether sleep disturbance was associated with the duration of back pain symptoms and whether pain intensity was associated with reported sleep disturbance. Data from 1,941 patients obtained from 13 studies conducted by the authors or their colleagues between 2001 and 2009 were used to determine the prevalence of sleep disturbance. Logistic regression analyses explored associations between sleep disturbance, the duration of low back symptoms and pain intensity. The estimated prevalence of sleep disturbance was 58.7% (95% CI 56.4-60.7%). Sleep disturbance was found to be dependent on pain intensity, where each increase by one point on a ten-point visual analogue scale (VAS) was associated with a 10% increase in the likelihood of reporting sleep disturbance. Our findings indicate that sleep disturbance is common in patients with LBP. In addition, we found that the intensity of back pain was only weakly associated with sleep disturbance, suggesting that other factors contribute

  12. Atmospheric Disturbance Environment Definition

    NASA Technical Reports Server (NTRS)

    Tank, William G.

    1994-01-01

    Traditionally, the application of atmospheric disturbance data to airplane design problems has been the domain of the structures engineer. The primary concern in this case is the design of structural components sufficient to handle transient loads induced by the most severe atmospheric "gusts" that might be encountered. The concern has resulted in a considerable body of high altitude gust acceleration data obtained with VGH recorders (airplane velocity, V, vertical acceleration, G, altitude, H) on high-flying airplanes like the U-2 (Ehernberger and Love, 1975). However, the propulsion system designer is less concerned with the accelerations of the airplane than he is with the airflow entering the system's inlet. When the airplane encounters atmospheric turbulence it responds with transient fluctuations in pitch, yaw, and roll angles. These transients, together with fluctuations in the free-stream temperature and pressure will disrupt the total pressure, temperature, Mach number and angularity of the inlet flow. For the mixed compression inlet, the result is a disturbed throat Mach number and/or shock position, and in extreme cases an inlet unstart can occur (cf. Section 2.1). Interest in the effects of inlet unstart on the vehicle dynamics of large, supersonic airplanes is not new. Results published by NASA in 1962 of wind tunnel studies of the problem were used in support of the United States Supersonic Transport program (SST) (White, at aI, 1963). Such studies continued into the late 1970's. However, in spite of such interest, there never was developed an atmospheric disturbance database for inlet unstart analysis to compare with that available for the structures load analysis. Missing were data for the free-stream temperature and pressure disturbances that also contribute to the unStart problem.

  13. A Survey of nearby, nearly face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    2014-09-01

    This is a continuation of a survey of nearby, nearly face-on spiral galaxies. The main purpose is to search for evidence of collisions with small galaxies that show up in X-rays by the generation of hot shocked gas from the collision. Secondary objectives include study of the spatial distribution point sources in the galaxy and to detect evidence for a central massive blackhole. These are alternate targets.

  14. A Survey of nearby, nearly face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    2014-09-01

    This is a continuation of a survey of nearby, nearly face-on spiral galaxies. The main purpose is to search for evidence of collisions with small galaxies that show up in X-rays by the generation of hot shocked gas from the collision. Secondary objectives include study of the spatial distribution point sources in the galaxy and to detect evidence for a central massive blackhole.

  15. [Neuroendocrine disturbances in obesity].

    PubMed

    Isidro, M L; Alvarez, P; Martínez, T; Cordido, F

    2004-01-01

    Obesity is associated with different disturbances in endocrine function. Both spontaneous growth hormone (GH) secretion and its response to several stimuli have shown to be reduced in obese patients. The GH responses to GH-releasing hormone and other challenges by pyridostigmine suggest that the reduction in GH secretion is related to an increased somatostatinergic tone. Other experiments point to a down-regulation of somatostatin receptors in the somatotroph cell. Ghrelin administration is followed by a massive GH release, but the possibility that ghrelin or GHRH deficiency are the cause of GH deficiency in obesity is unlikely. The increase in free fatty acids in obesity might be related to GH reduction, since acipimox administration is able to reverse GH secretion. In women, abdominal obesity is associated with hyperandrogenism and low sex hormone-binding globulin levels. Obese men have low testosterone and gonadotrophin concentrations, specially in cases of morbid obesity. An increase in hypothalamic-pituitary-adrenal axis activity and some resistance to dexamethasone suppression have been described in abdominal obesity. This effect may be due to neuroendocrine alterations related to a genetic origin. Adrenal hyperfunction may favour cardiovascular and metabolic complications. There are no disturbances in thyroid function. Sometimes a reduction in prolactin response to several stimuli has been reported. This effect may be due to hyperinsulinaemia or to disturbances in the dopaminergic tone.

  16. Investigations of Galaxy Clusters Using Gravitational Lensing

    SciTech Connect

    Wiesner, Matthew P.

    2014-08-01

    In this dissertation, we discuss the properties of galaxy clusters that have been determined using strong and weak gravitational lensing. A galaxy cluster is a collection of galaxies that are bound together by the force of gravity, while gravitational lensing is the bending of light by gravity. Strong lensing is the formation of arcs or rings of light surrounding clusters and weak lensing is a change in the apparent shapes of many galaxies. In this work we examine the properties of several samples of galaxy clusters using gravitational lensing. In Chapter 1 we introduce astrophysical theory of galaxy clusters and gravitational lensing. In Chapter 2 we examine evidence from our data that galaxy clusters are more concentrated than cosmology would predict. In Chapter 3 we investigate whether our assumptions about the number of galaxies in our clusters was valid by examining new data. In Chapter 4 we describe a determination of a relationship between mass and number of galaxies in a cluster at higher redshift than has been found before. In Chapter 5 we describe a model of the mass distribution in one of the ten lensing systems discovered by our group at Fermilab. Finally in Chapter 6 we summarize our conclusions.

  17. Merging Galaxy Cluster A2255 in Mid-infrared

    NASA Astrophysics Data System (ADS)

    Shim, Hyunjin; Im, Myungshin; Lee, Hyung Mok; Lee, Myung Gyoon; Kim, Seong Jin; Hwang, Ho Seong; Hwang, Narae; Ko, Jongwan; Lee, Jong Chul; Lim, Sungsoon; Matsuhara, Hideo; Seo, Hyunjong; Wada, Takehiko; Goto, Tomotsugu

    2011-01-01

    We present the mid-infrared (MIR) observation of a nearby galaxy cluster, A2255, by the AKARI space telescope. Using AKARI's continuous wavelength coverage between 3 and 24 μm and the wide field of view, we investigate the properties of cluster member galaxies to see how the infall of the galaxies, the cluster substructures, and the cluster-cluster merger influence their evolution. We show that the excess of MIR (~11 μm) flux is a good indicator for discriminating galaxies at different evolutionary stages and for dividing galaxies into three classes accordingly: strong MIR-excess (N3 - S11>0.2) galaxies that include both unobscured and obscured star-forming galaxies; weak MIR-excess (-2.0 < N3 - S11 < -1.2) galaxies that are quiescent, old (>5 Gyr) galaxies where the MIR emission arises mainly from the circumstellar dust around AGB stars; and intermediate MIR-excess (-1.2 < N3 - S11 < 0.2) galaxies in between the two classes that are less than a few Gyr old past the prime star formation activity. With the MIR-excess diagnostics, we investigate how local and cluster-scale environments affect the individual galaxies. We derive the total star formation rate (SFR) and the specific SFR of A2255 using the strong MIR-excess galaxies. The dust-free, total SFR of A2255 is ~130 M sun yr-1, which is consistent with the SFRs of other clusters of galaxies at similar redshifts and with similar masses. We find no strong evidence that supports enhanced star formation either inside the cluster or in the substructure region, suggesting that the infall or the cluster merging activities tend to suppress star formation. The intermediate MIR-excess galaxies, representing galaxies in transition from star-forming galaxies to quiescent galaxies, are located preferentially at the medium density region or cluster substructures with higher surface density of galaxies. Our findings suggest that galaxies are being transformed from star-forming galaxies into red, quiescent galaxies from the

  18. A Disturbed Galactic Duo

    NASA Astrophysics Data System (ADS)

    2011-04-01

    The galaxies in this cosmic pairing, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166. Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger neighbours. This galactic grouping, found about 70 million light-years away in the constellation Sextans (The Sextant), was discovered by the English astronomer William Herschel in 1783. Modern astronomers have gauged the distance between NGC 3169 (left) and NGC 3166 (right) as a mere 50 000 light-years, a separation that is only about half the diameter of the Milky Way galaxy. In such tight quarters, gravity can start to play havoc with galactic structure. Spiral galaxies like NGC 3169 and NGC 3166 tend to have orderly swirls of stars and dust pinwheeling about their glowing centres. Close encounters with other massive objects can jumble this classic configuration, often serving as a disfiguring prelude to the merging of galaxies into one larger galaxy. So far, the interactions of NGC 3169 and NGC 3166 have just lent a bit of character. NGC 3169's arms, shining bright with big, young, blue stars, have been teased apart, and lots of luminous gas has been drawn out from its disc. In NGC 3166's case, the dust lanes that also usually outline spiral arms are in disarray. Unlike its bluer counterpart, NGC 3166 is not forming many new stars. NGC 3169 has another distinction: the faint yellow dot beaming through a veil of dark dust just to the left of and close to the galaxy's centre [1]. This flash is the leftover of a supernova detected in 2003 and known accordingly as SN 2003cg. A supernova of this

  19. A Disturbed Galactic Duo

    NASA Astrophysics Data System (ADS)

    2011-04-01

    The galaxies in this cosmic pairing, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166. Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger neighbours. This galactic grouping, found about 70 million light-years away in the constellation Sextans (The Sextant), was discovered by the English astronomer William Herschel in 1783. Modern astronomers have gauged the distance between NGC 3169 (left) and NGC 3166 (right) as a mere 50 000 light-years, a separation that is only about half the diameter of the Milky Way galaxy. In such tight quarters, gravity can start to play havoc with galactic structure. Spiral galaxies like NGC 3169 and NGC 3166 tend to have orderly swirls of stars and dust pinwheeling about their glowing centres. Close encounters with other massive objects can jumble this classic configuration, often serving as a disfiguring prelude to the merging of galaxies into one larger galaxy. So far, the interactions of NGC 3169 and NGC 3166 have just lent a bit of character. NGC 3169's arms, shining bright with big, young, blue stars, have been teased apart, and lots of luminous gas has been drawn out from its disc. In NGC 3166's case, the dust lanes that also usually outline spiral arms are in disarray. Unlike its bluer counterpart, NGC 3166 is not forming many new stars. NGC 3169 has another distinction: the faint yellow dot beaming through a veil of dark dust just to the left of and close to the galaxy's centre [1]. This flash is the leftover of a supernova detected in 2003 and known accordingly as SN 2003cg. A supernova of this

  20. A photometrically and spectroscopically confirmed population of passive spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fraser-McKelvie, Amelia; Brown, Michael J. I.; Pimbblet, Kevin A.; Dolley, Tim; Crossett, Jacob P.; Bonne, Nicolas J.

    2016-10-01

    We have identified a population of passive spiral galaxies from photometry and integral field spectroscopy. We selected z < 0.035 spiral galaxies that have WISE colours consistent with little mid-infrared emission from warm dust. Matched aperture photometry of 51 spiral galaxies in ultraviolet, optical and mid-infrared show these galaxies have colours consistent with passive galaxies. Six galaxies form a spectroscopic pilot study and were observed using the Wide-Field Spectrograph to check for signs of nebular emission from star formation. We see no evidence of substantial nebular emission found in previous red spiral samples. These six galaxies possess absorption-line spectra with 4000 Å breaks consistent with an average luminosity-weighted age of 2.3 Gyr. Our photometric and integral field spectroscopic observations confirm the existence of a population of local passive spiral galaxies, implying that transformation into early-type morphologies is not required for the quenching of star formation.

  1. Vehicle Disturbance Test

    NASA Astrophysics Data System (ADS)

    Clapp, Brian

    2001-07-01

    The Vehicle Disturbance Test {VDT} is used to characterize uncompensated environmental disturbances acting upon the HST during normal operation. The VDT is a passive test {not a forced-response test} used to obtain signatures for both externally induced {e.g. SA-3} and internally induced {e.g. NCC and ACS mechanisms} disturbances for comparison with past VDT results. The disturbances observed will be used as the nominal on-orbit disturbances in pointing control simulations until the next VDT is run. The test occurs after release, and most of the VDT can be run during the BEA period. The -V1 sunpoint portion of the VDT occurs after the BEA period is complete. The VDT shall consist of five separate tests that need not occur consecutively. The overall duration of the VDT tests is at least 17 orbits of spacecraft time including {1} at least 1 full orbit at +V3 sunpoint prior to NCS CPL turn-on while performing ACS mechanism motions simulating routine flight operations, {2} at least 5 full orbits at +V3 sunpoint prior to NCS CPL turn-on, {3} at least 1 full orbit at +V3 sunpoint during NCC startup, {4} at least 5 full orbits at +V3 sunpoint while NCC is operating at steady-state, and {5} at least 5 full orbits at -V1 sunpoint with the NCC operating at steady-state. Each test is initiated via SMS execution of stored program macros in the HST flight computer to switch the attitude control law gains to low-bandwidth maneuver gains, command the gyros into low mode, terminate Velocity aberration and parallax {VAP} processing, and modify flight computer diagnostic mnemonics to display the roll component of DVTHEP. The nominal attitude control law configuration will be restored at the end of each test via SMS execution of stored program macros. The stored program command macros are developed specifically for the VDT by the Flight Software and Pointing Control System groups.

  2. NGC 3934: a shell galaxy in a compact galaxy environment

    NASA Astrophysics Data System (ADS)

    Bettoni, D.; Galletta, G.; Rampazzo, R.; Marino, A.; Mazzei, P.; Buson, L. M.

    2011-10-01

    Context. Mergers/accretions are considered the main drivers of the evolution of galaxies in groups. We investigate the NGC 3933 poor galaxy association that contains NGC 3934, which is classified as a polar-ring galaxy. Aims: The multi-band photometric analysis of NGC 3934 allows us to investigate the nature of this galaxy and to re-define the NGC 3933 group members with the aim to characterize the group's dynamical properties and its evolutionary phase. Methods: We imaged the group in the far (FUV, λeff = 1539 Å) and near (NUV, λeff = 2316 Å) ultraviolet (UV) bands of the Galaxy Evolution Explorer (GALEX). From the deep optical imaging we determined the fine structure of NGC 3934. We measured the recession velocity of PGC 213894 which shows that it belongs to the NGC 3933 group. We derived the spectral energy distribution (SED) from FUV to far-IR emission of the two brightest members of the group. We compared a grid of smooth particle hydrodynamical (SPH) chemo-photometric simulations with the SED and the integrated properties of NGC 3934 and NGC 3933 to devise their possible formation/evolutionary scenarios. Results: The NGC 3933 group has six bright members: a core composed of five galaxies, which have Hickson's compact group characteristics, and a more distant member, PGC 37112. The group velocity dispersion is relatively low (157 ± 44 km s-1). The projected mass, from the NUV photometry, is ~7 × 1012 M⊙ with a crossing time of 0.04 Hubble times, suggesting that at least in the center the group is virialized. We do not find evidence that NGC 3934 is a polar-ring galaxy, as suggested by the literature, but find that it is a disk galaxy with a prominent dust-lane structure and a wide type-II shell structure. Conclusions: NGC 3934 is a quite rare example of a shell galaxy in a likely dense galaxy region. The comparison between physically motivated SPH simulations with multi-band integrated photometry suggests that NGC 3934 is the product of a major merger.

  3. Galaxies Collide to Create Hot, Huge Galaxy

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This image of a pair of colliding galaxies called NGC 6240 shows them in a rare, short-lived phase of their evolution just before they merge into a single, larger galaxy. The prolonged, violent collision has drastically altered the appearance of both galaxies and created huge amounts of heat turning NGC 6240 into an 'infrared luminous' active galaxy.

    A rich variety of active galaxies, with different shapes, luminosities and radiation profiles exist. These galaxies may be related astronomers have suspected that they may represent an evolutionary sequence. By catching different galaxies in different stages of merging, a story emerges as one type of active galaxy changes into another. NGC 6240 provides an important 'missing link' in this process.

    This image was created from combined data from the infrared array camera of NASA's Spitzer Space Telescope at 3.6 and 8.0 microns (red) and visible light from NASA's Hubble Space Telescope (green and blue).

  4. THE GALAXY OPTICAL LUMINOSITY FUNCTION FROM THE AGN AND GALAXY EVOLUTION SURVEY

    SciTech Connect

    Cool, Richard J.; Eisenstein, Daniel J.; Kochanek, Christopher S.; Brown, Michael J. I.; Caldwell, Nelson; Forman, William R.; Hickox, Ryan C.; Jones, Christine; Murray, Stephen S.; Dey, Arjun; Jannuzi, Buell T.; Moustakas, John

    2012-03-20

    We present the galaxy optical luminosity function for the redshift range 0.05 < z < 0.75 from the AGN and Galaxy Evolution Survey, a spectroscopic survey of 7.6 deg{sup 2} in the Booetes field of the NOAO Deep Wide-Field Survey. Our statistical sample is composed of 12,473 galaxies with known redshifts down to I = 20.4 (AB). Our results at low redshift are consistent with those from Sloan Digital Sky Survey; at higher redshift, we find strong evidence for evolution in the luminosity function, including differential evolution between blue and red galaxies. We find that the luminosity density evolves as (1 + z){sup (0.54{+-}0.64)} for red galaxies and (1 + z){sup (1.64{+-}0.39)} for blue galaxies.

  5. Dual Stellar Halos in Early-type Galaxies and Formation of Massive Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Myung Gyoon; Jang, In Sung

    2016-08-01

    M105 in the Leo I Group is a textbook example of a standard elliptical galaxy. It is only one of the few elliptical galaxies for which we can study their stellar halos using the resolved stars. It is an ideal target to study the structure and composition of stellar halos in elliptical galaxies. We present photometry and metallicity of the resolved stars in the inner and outer regions of M105. These provide strong evidence that there are two distinct stellar halos in this galaxy, a metal-poor (blue) halo and a metal-rich (red) halo. Then we compare them with those in other early-type galaxies and use the dual halo mode formation scenario to describe how massive galaxies formed.

  6. Galaxy NGC 55

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the nearby edge-on spiral galaxy NGC 55 was taken by Galaxy Evolution Explorer on September 14, 2003, during 2 orbits. This galaxy lies 5.4 million light years from our Milky Way galaxy and is a member of the 'local group' of galaxies that also includes the Andromeda galaxy (M31), the Magellanic clouds, and 40 other galaxies. The spiral disk of NGC 55 is inclined to our line of sight by approximately 80 degrees and so this galaxy looks cigar-shaped. This picture is a combination of Galaxy Evolution Explorer images taken with the far ultraviolet (colored blue) and near ultraviolet detectors, (colored red). The bright blue regions in this image are areas of active star formation detected in the ultraviolet by Galaxy Evolution Explorer. The red stars in this image are foreground stars in our own Milky Way galaxy.

  7. Disturbing Behavior Checklists" Technical Manual

    ERIC Educational Resources Information Center

    Algozzine, Bob

    2012-01-01

    Ecological theorists have suggested that "disturbance" may result from an interaction between a child's behavior and reactions to that behavior within ecosystems such as schools. In this context, behavior is viewed as "disturbing" rather than "disturbed" and equal emphasis is given to the child and to individuals with whom the child interacts when…

  8. Secular Evolution in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Kormendy, John

    2013-10-01

    bulges because the latter retain a `memory' of their disky origin. That is, they have one or more characteristics of disks: (1) flatter shapes than those of classical bulges, (2) correspondingly large ratios of ordered to random velocities, (3) small velocity dispersions with respect to the Faber-Jackson correlation between velocity dispersion and bulge luminosity, (4) spiral structure or nuclear bars in the `bulge' part of the light profile, (5) nearly exponential brightness profiles and (6) starbursts. So the cleanest examples of pseudobulges are recognisable. However, pseudo and classical bulges can coexist in the same galaxy. I review two important implications of secular evolution: (1) The existence of pseudobulges highlights a problem with our theory of galaxy formation by hierarchical clustering. We cannot explain galaxies that are completely bulgeless. Galaxy mergers are expected to happen often enough so that every giant galaxy should have a classical bulge. But we observe that bulgeless giant galaxies are common in field environments. We now realise that many dense centres of galaxies that we used to think are bulges were not made by mergers; they were grown out of disks. So the challenge gets more difficult. This is the biggest problem faced by our theory of galaxy formation. (2) Pseudobulges are observed to contain supermassive black holes (BHs), but they do not show the well-known, tight correlations between BH mass and the mass and velocity dispersion of the host bulge. This leads to the suggestion that there are two fundamentally different BH feeding processes. Rapid global inward gas transport in galaxy mergers leads to giant BHs that correlate with host ellipticals and classical bulges, whereas local and more stochastic feeding of small BHs in largely bulgeless galaxies evidently involves too little energy feedback to result in BH-host coevolution. It is an important success of the secular evolution picture that morphological differences can be used to

  9. "Dead quasars" in nearby galaxies?

    PubMed

    Rees, M J

    1990-02-16

    The nuclei of some galaxies undergo violent activity, quasars being the most extreme instances of this phenomenon. Such activity is probably short-lived compared to galactic lifetimes, and was most prevalent when the universe was only about one-fifth of its present age. A massive black hole seems the inevitable end point of such activity, and dead quasars should greatly outnumber active ones. In recent years, studies of stellar motions in the cores of several nearby galaxies indicate the presence of central dark masses which could be black holes. This article discusses how such evidence might be corroborated, and the potential implications for our understanding of active galaxies and black holes. PMID:17746076

  10. Metal enriched gaseous halos around distant radio galaxies: Clues to feedback in galaxy formation

    SciTech Connect

    Reuland, M; van Breugel, W; de Vries, W; Dopita, A; Dey, A; Miley, G; Rottgering, H; Venemans, B; Stanford, S A; Lacy, M; Spinrad, H; Dawson, S; Stern, D; Bunker, A

    2006-08-01

    We present the results of an optical and near-IR spectroscopic study of giant nebular emission line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07 and B2 0902+34. Previous deep narrow band Ly{alpha} imaging had revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s{sup -1}, and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions >1000 km s{sup -1}. The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of {approx} 60 kpc along the radio-axis. The dynamical structures traced in the Ly{alpha} line are, in most cases, closely echoed in the Carbon and Oxygen lines. This shows that the Ly{alpha} line is produced in a highly clumped medium of small filling factor, and can therefore be used as a tracer of the dynamics of HzRGs. We conclude that these HzRGs are undergoing a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming 'red and dead' Elliptical galaxies.

  11. Infrared images of merging galaxies

    NASA Technical Reports Server (NTRS)

    Wright, G. S.; James, P. A.; Joseph, R. D.; Mclean, I. S.; Doyon, R.

    1990-01-01

    Infrared imaging of interacting galaxies is especially interesting because their optical appearance is often so chaotic due to extinction by dust and emission from star formation regions, that it is impossible to locate the nuclei or determine the true stellar distribution. However, at near-infrared wavelengths extinction is considerably reduced, and most of the flux from galaxies originates from red giant stars that comprise the dominant stellar component by mass. Thus near infrared images offer the opportunity to study directly components of galactic structure which are otherwise inaccessible. Such images may ultimately provide the framework in which to understand the activity taking place in many of the mergers with high Infrared Astronomy Satellite (IRAS) luminosities. Infrared images have been useful in identifying double structures in the nuclei of interacting galaxies which have not even been hinted at by optical observations. A striking example of this is given by the K images of Arp 220. Graham et al. (1990) have used high resolution imaging to show that it has a double nucleus coincident with the radio sources in the middle of the dust lane. The results suggest that caution should be applied in the identification of optical bright spots as multiple nuclei in the absence of other evidence. They also illustrate the advantages of using infrared imaging to study the underlying structure in merging galaxies. The authors have begun a program to take near infrared images of galaxies which are believed to be mergers of disk galaxies because they have tidal tails and filaments. In many of these the merger is thought to have induced exceptionally luminous infrared emission (cf. Joseph and Wright 1985, Sanders et al. 1988). Although the optical images of the galaxies show spectacular dust lanes and filaments, the K images all have a very smooth distribution of light with an apparently single nucleus.

  12. Galaxies of all Shapes Host Black Holes

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This artist's concept illustrates the two types of spiral galaxies that populate our universe: those with plump middles, or central bulges (upper left), and those lacking the bulge (foreground).

    New observations from NASA's Spitzer Space Telescope provide strong evidence that the slender, bulgeless galaxies can, like their chubbier counterparts, harbor supermassive black holes at their cores. Previously, astronomers thought that a galaxy without a bulge could not have a supermassive black hole. In this illustration, jets shooting away from the black holes are depicted as thin streams.

    The findings are reshaping theories of galaxy formation, suggesting that a galaxy's 'waistline' does not determine whether it will be home to a big black hole.

  13. Vehicle Disturbance Test

    NASA Astrophysics Data System (ADS)

    Clapp, Brian

    2009-07-01

    The purpose of the VDT is to measure and characterize uncompensated environmental disturbances acting upon the HST during normal operation. The VDT is a passive test {not a forced-response test} used to obtain signatures for both externally induced {e.g. SCM, SA-3, SSM thermal gradients} and internally induced {e.g. HGA, RWA, COS and WFC3 mechanisms} disturbances affecting HST LOS pointing. The disturbances observed will be used as the nominal on-orbit disturbances in pointing control simulations until the next VDT is run.The test occurs after release, and most of the VDT can be run during the BEA period. The ?V1 sunpoint portion of the VDT usually occurs after the BEA period is complete. The VDT shall consist of two separate tests that need not occur consecutively. The overall duration of the VDT is at least 13 orbits of spacecraft time including {1} at least 8 orbits at +V3 sunpoint after achieving thermal equilibrium {at least 36-hours at +V3 sunpoint} and three out of 8-orbits have RWA Friction Compensation turned Off, and {2} at least 5 orbits at ?V1 sunpoint {all or part of this segment have RWA Friction Compensation turned Off}. At the beginning of each test, the attitude control law gains are switched to maneuver gains, and the gyros are commanded to low mode. The nominal attitude control law configuration will be restored at the end of each test.Each test is initiated via SMS execution of stored program macros in the HST flight computer to switch the attitude control law gains to low-bandwidth maneuver gains, command the gyros into low mode, terminate Velocity aberration and parallax {VAP} processing, and manage the status of on-board RWA Friction Compensation. The nominal attitude control law configuration will be restored at the end of each test via SMS execution of stored program macros. The stored program command macros are developed specifically for the VDT by the Flight Software and Pointing Control System groups.

  14. Disturbed 40Ar 39Ar systematics in hydrothermal biotite and hornblende at the Scotia gold mine, Western Australia: Evidence for argon loss associated with post-mineralisation fluid movement

    NASA Astrophysics Data System (ADS)

    Kent, Adam J. R.; Campbell McCuaig, T.

    1997-11-01

    Homblende and biotite that formed during gold mineralisation at the Scotia mine, Western Australia, have erratic 40Ar 39Ar release spectra and total gas ages that are ˜200-900 million year younger than the ca. 2600-2620 Ma minimum age of gold mineralisation, as given by 40Ar 39Ar plateau (muscovite) ages of crosscutting pegmatite dykes. Analysed hornblendes are dominated by magnesio hornblende but also contain small domains of ferro-actinolitic hornblende, actinolitic hornblende, and actinolite. Biotite also appears to be substantially altered to chlorite along cleavage planes. Relatively young apparent ages and high K/Ca ratios of argon released from hornblendes at temperatures less than ˜1000°C are interpreted to be the result of degassing of contaminant biotite. However, this cannot totally explain the young ages of hornblendes. Gas fractions released at furnace temperatures above 1000 C, where the effect of biotite degassing is demonstrably negligible, still have apparent ages that are ˜200-900 million years younger than the age of muscovite from post-gold pegmatite dykes. The close proximity of disturbed hydrothermal hornblende samples to apparently undisturbed pegmatite muscovite samples (less than a few metres in some cases) is difficult to reconcile with argon loss in hydrothermal hornblende being the product of thermally-driven volume diffusion. Given a suitable thermal history, argon loss could occur preferentially in hornblendes if (1) the closure (for slow cooling) and blocking (for reheating) temperatures of hydrothermal hornblendes were lower than published estimates, as has been observed in structurally complex metamorphic hornblendes and/or (2) the closure and blocking temperature of pegmatite muscovite were higher than commonly estimated. However, neither of these interpretations can easily explain the large variation in hornblende ages. It is instead suggested that argon loss occurred during mineral-fluid interaction during movement of a

  15. Sleep Disturbances in Neurodevelopmental Disorders.

    PubMed

    Robinson-Shelton, Althea; Malow, Beth A

    2016-01-01

    Sleep disturbances are extremely prevalent in children with neurodevelopmental disorders compared to typically developing children. The diagnostic criteria for many neurodevelopmental disorders include sleep disturbances. Sleep disturbance in this population is often multifactorial and caused by the interplay of genetic, neurobiological and environmental overlap. These disturbances often present either as insomnia or hypersomnia. Different sleep disorders present with these complaints and based on the clinical history and findings from diagnostic tests, an appropriate diagnosis can be made. This review aims to provide an overview of causes, diagnosis, and treatment of sleep disturbances in neurodevelopmental disorders that present primarily with symptoms of hypersomnia and/or insomnia. PMID:26719309

  16. The Impossibly Early Galaxy Problem

    NASA Astrophysics Data System (ADS)

    Steinhardt, Charles. L.; Capak, Peter; Masters, Dan; Speagle, Josh S.

    2016-06-01

    The current hierarchical merging paradigm and ΛCDM predict that the z˜ 4-8 universe should be a time in which the most massive galaxies are transitioning from their initial halo assembly to the later baryonic evolution seen in star-forming galaxies and quasars. However, no evidence of this transition has been found in many high-redshift galaxy surveys including CFHTLS, Cosmic Assembly Near-infrared Deep Extragalactic Survey (CANDELS), and Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH), which were the first studies to probe the high-mass end at these redshifts. Indeed, if halo mass to stellar mass ratios estimated at lower-redshift continue to z˜ 6-8, CANDELS and SPLASH report several orders of magnitude more M˜ {10}12-13{M}⊙ halos than is possible to have been formed by those redshifts, implying that these massive galaxies formed impossibly early. We consider various systematics in the stellar synthesis models used to estimate physical parameters and possible galaxy formation scenarios in an effort to reconcile observation with theory. Although known uncertainties can greatly reduce the disparity between recent observations and cold dark matter merger simulations, there remains considerable tension with current theory even if taking the most conservative view of the observations.

  17. The Impossibly Early Galaxy Problem

    NASA Astrophysics Data System (ADS)

    Steinhardt, Charles L.; Capak, Peter L.; Masters, Daniel; Speagle, Josh S.

    2016-01-01

    The current hierarchical merging paradigm and ΛCDM predict that the z ~ 4-8 universe should be a time in which the most massive galaxies are transitioning from their initial halo assembly to the later baryonic evolution seen in star-forming galaxies and quasars. However, no evidence of this transition has been found in many high redshift galaxy surveys including CFHTLS, CANDELS and SPLASH, the first studies to probe the high-mass end at these redshifts. Indeed, if halo mass to stellar mass ratios estimated at lower-redshift continue to z ~ 6-8, CANDELS and SPLASH report several orders of magnitude more M ~ 10^12-13 M⊙ halos than are possible to have formed by those redshifts, implying these massive galaxies formed impossibly early. We consider various systematics in the stellar synthesis models used to estimate physical parameters and possible galaxy formation scenarios in an effort to reconcile observation with theory. Although known uncertainties can greatly reduce the disparity between recent observations and cold dark matter merger simulations, even taking the most conservative view of the observations, there remains considerable tension with current theory.

  18. The galaxy population of the z= 1 cluster of galaxies MG2016+112

    NASA Astrophysics Data System (ADS)

    Toft, S.; Soucail, G.; Hjorth, J.

    2003-09-01

    A photometric redshift analysis of galaxies in the field of the wide-separation gravitational lens MG2016+112 reveals a population of 69 galaxies with photometric redshifts consistent with being in a cluster at the redshift of the giant elliptical lensing galaxy z= 1.00. The Ks-band luminosity function of the cluster galaxies is well represented by the Schechter function with a characteristic magnitude K*s= 18.90+0.45-0.57 and faint-end slope α=-0.60+0.39-0.33, consistent with what is expected for a passively evolving population of galaxies formed at high redshift, zf > 2. From the total Ks-band flux of the cluster galaxies and a dynamical estimate of the total mass of the cluster, the rest-frame Ks-band mass-to-light ratio of the cluster is derived to be M/LKs= 27+64-17h50(M/LKs)solar, in agreement with the upper limit derived earlier from Chandra X-ray observations and the value derived locally in the Coma cluster. The cluster galaxies span a red sequence with a considerable scatter in the colour-magnitude diagrams, suggesting that they contain young stellar populations in addition to the old populations of main-sequence stars that dominate the Ks-band luminosity function. This is in agreement with spectroscopic observations which show that 5 out of the 6 galaxies in the field confirmed to be at the redshift of the lensing galaxy have emission lines. The projected spatial distribution of the cluster galaxies is filamentary-like rather than centrally concentrated around the lensing galaxy, and shows no apparent luminosity segregation. A handful of the cluster galaxies show evidence of merging/interaction. The results presented in this paper suggest that a young cluster of galaxies is assembling around MG2016+112.

  19. Gait disturbances in dystrophic hamsters.

    PubMed

    Hampton, Thomas G; Kale, Ajit; Amende, Ivo; Tang, Wenlong; McCue, Scott; Bhagavan, Hemmi N; VanDongen, Case G

    2011-01-01

    The delta-sarcoglycan-deficient hamster is an excellent model to study muscular dystrophy. Gait disturbances, important clinically, have not been described in this animal model. We applied ventral plane videography (DigiGait) to analyze gait in BIO TO-2 dystrophic and BIO F1B control hamsters walking on a transparent treadmill belt. Stride length was ∼13% shorter (P < .05) in TO-2 hamsters at 9 months of age compared to F1B hamsters. Hindlimb propulsion duration, an indicator of muscle strength, was shorter in 9-month-old TO-2 (247 ± 8 ms) compared to F1B hamsters (272 ± 11 ms; P < .05). Braking duration, reflecting generation of ground reaction forces, was delayed in 9-month-old TO-2 (147 ± 6 ms) compared to F1B hamsters (126 ± 8 ms; P < .05). Hindpaw eversion, evidence of muscle weakness, was greater in 9-month-old TO-2 than in F1B hamsters (17.7 ± 1.2° versus 8.7 ± 1.6°; P < .05). Incline and decline walking aggravated gait disturbances in TO-2 hamsters at 3 months of age. Several gait deficits were apparent in TO-2 hamsters at 1 month of age. Quantitative gait analysis demonstrates that dystrophic TO-2 hamsters recapitulate functional aspects of human muscular dystrophy. Early detection of gait abnormalities in a convenient animal model may accelerate the development of therapies for muscular dystrophy.

  20. Radio continuum observations of the quasar-galaxy pair 3C 232-NGC 3067

    NASA Technical Reports Server (NTRS)

    Haxthausen, Eric; Carilli, Chris; Vangorkom, Jacqueline H.

    1990-01-01

    The quasar-galaxy pair 3C 232-NGC 3067 is well known to show absorption by gas associated with the foreground galaxy against the background quasar (see Stocke et al. this volume). Observations by Carilli, van Gorkom, and Stocke (Nature 338, 134, 1989) found that the absorbing gas is located in a long tail of gas which extends from the galaxy toward the quasar and beyond (in projection). Though the HI observations of NGC 3067 indicate that the galaxy has been severely disturbed, there is no obvious candidate in the field which could cause such a disturbance, leading to the conclusion that the system has undergone a recent merger. The radio continuum observations of this system were designed to study the nature of this highly disturbed galaxy. New continuum observations confirm the notion that NGC 3067 is a highly disturbed system, and, in particular, the notion that the western half of the galaxy extends only 1/2 as far in radius as the eastern half. This disturbance must have occurred recently, since the galactic rotation would smooth out the observed asymmetry in about 10(exp 8) years. Researchers are left with the problem that there are no obvious candidates which could have caused such a disturbance.

  1. Galaxy groups

    SciTech Connect

    Brent Tully, R.

    2015-02-01

    Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well-studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times 10{sup 12}M{sub ⊙} are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of groups, the ratio of first to second turnaround depends on the dark matter and dark energy content of the universe and a crude estimate can be made from the current observations of Ω{sub matter}∼0.15 in a flat topology, with a 68% probability of being less than 0.44.

  2. The origin of galaxies and clusters of galaxies.

    PubMed

    Peebles, P J

    1984-06-29

    Debate on how galaxies and clusters of galaxies formed has reached an interesting stage at which one can find arguments for quite different scenarios. The galaxy distribution has a complex "frothy" character that could be the fossil of a network of protoclusters or pancakes that produced galaxies. However, there are galaxies like our own that seem never to have been in a protocluster but are physically similar to the galaxies in dense clusters. Some clues to be assessed in resolving this dilemma are the possible existence of galaxy filaments, the relative ages of galaxies and clusters of galaxies, and the continuity between cluster and field galaxies and between galaxies and clusters of galaxies.

  3. Photometric and Kinematical Study of Nearby Groups of Galaxies Around IC 65 and NGC 6962

    NASA Astrophysics Data System (ADS)

    Vennik, J.; Tago, E.

    The IC 65 group (z = 0.0089) of four late type galaxies - IC 65, UGC 608, UGC 622, and PGC 138291 - has been studied earlier in the 21 cm HI line by van Moorsel (1983, A&AS, 54, 1), who found disturbed HI envelopes of bright group members, and detected a new HI-rich LSB galaxy.

  4. Oxygen abundance maps of CALIFA galaxies

    NASA Astrophysics Data System (ADS)

    Zinchenko, I. A.; Pilyugin, L. S.; Grebel, E. K.; Sánchez, S. F.; Vílchez, J. M.

    2016-11-01

    We construct maps of the oxygen abundance distribution across the discs of 88 galaxies using Calar Alto Legacy Integral Field Area survey (CALIFA) Data Release 2 (DR2) spectra. The position of the centre of a galaxy (coordinates on the plate) was also taken from the CALIFA DR2. The galaxy inclination, the position angle of the major axis, and the optical radius were determined from the analysis of the surface brightnesses in the Sloan Digital Sky Survey (SDSS) g and r bands of the photometric maps of SDSS Data Release 9. We explore the global azimuthal abundance asymmetry in the discs of the CALIFA galaxies and the presence of a break in the radial oxygen abundance distribution. We found that there is no significant global azimuthal asymmetry for our sample of galaxies, i.e. the asymmetry is small, usually lower than 0.05 dex. The scatter in oxygen abundances around the abundance gradient has a comparable value, ≲0.05 dex. A significant (possibly dominant) fraction of the asymmetry can be attributed to the uncertainties in the geometrical parameters of these galaxies. There is evidence for a flattening of the radial abundance gradient in the central part of 18 galaxies. We also estimated the geometric parameters (coordinates of the centre, the galaxy inclination and the position angle of the major axis) of our galaxies from the analysis of the abundance map. The photometry-map-based and the abundance-map-based geometrical parameters are relatively close to each other for the majority of the galaxies but the discrepancy is large for a few galaxies with a flat radial abundance gradient.

  5. Very metal-poor galaxies: ionized gas kinematics in nine objects

    NASA Astrophysics Data System (ADS)

    Moiseev, A. V.; Pustilnik, S. A.; Kniazev, A. Y.

    2010-07-01

    The study of ionized gas morphology and kinematics in nine extremely metal-deficient (XMD) galaxies with the scanning Fabry-Perot interferometer on the Special Astrophysical Observatory (SAO) 6-m telescope is presented. Some of these very rare objects (with currently known range of O/H of 7.12 < 12 + log(O/H) < 7.65, or ) are believed to be the best proxies of `young' low-mass galaxies in the high-redshift Universe. One of the main goals of this study is to look for possible evidence of star formation (SF) activity induced by external perturbations. Recent results from HI mapping of a small subsample of XMD star-forming galaxies provided confident evidence for the important role of interaction-induced SF. Our observations provide complementary or new information that the great majority of the studied XMD dwarfs have strongly disturbed gas morphology and kinematics or the presence of detached components. We approximate the observed velocity fields by simple models of a rotating tilted thin disc, which allows us the robust detection of non-circular gas motions. These data, in turn, indicate the important role of current/recent interactions and mergers in the observed enhanced SF. As a by-product of our observations, we obtained data for two Low Surface Brightness (LSB) dwarf galaxies: Anon J012544+075957 that is a companion of the merger system UGC 993, and SAO 0822+3545 which shows off-centre, asymmetric, low star formation rate star-forming regions, likely induced by the interaction with the companion XMD dwarf HS 0822+3542. Based on observations obtained with the Special Astrophysical Observatory RAS 6-m telescope. E-mail: moisav@gmail.com (AVM); sap@sao.ru (SAP); akniazev@saao.ac.za (AYK)

  6. ASCA Observation of the Poor Cluster of Galaxies AWM 7: Evidence of an Abundance Increase in the Intra-Cluster Medium at the Center

    NASA Astrophysics Data System (ADS)

    Xu, Haiguang; Ezawa, Hajime; Fukazawa, Yasushi; Kikuchi, Ken'ichi; Makishima, Kazuo; Ohashi, Takaya; Tamura, Takayuki

    1997-02-01

    We present the results of the ASCA central-pointing observation of the poor cD cluster AWM 7. The Performance Verification phase data of GIS 2, GIS 3, SIS 0 chip 1, and SIS 1 chip 3 were used to study the properties of the intra-cluster medium (ICM) within 16' around the X-ray centroid. We found that, compared with the outer regions, the equivalent width of the Fe-K lines increases in the central 4' ( ~ 123 h(-1_{50) kpc)} region by a factor of ~ 1.5. Although the ICM temperature tends to decrease in the same region, the observed increase in the Fe-K line equivalent width cannot be explained away by a possible temperature drop. The model fitting indicates that the abundance increases from ~ 0.4 solar outside 4' to ~ 0.6 solar at the center. Thus, after the Centaurus cluster and the Virgo cluster, AWM 7 is the third poor cD cluster confirmed to show an abundance increase in the central region. The 0.5--3 keV flux of the cool emission within 4' is constrained to be <8*E(42) h(-2}_{50) erg s(-1) , or <21% of the total 0.5--3 keV flux from the same spatial region. We discuss possible relations of these phenomena to the cD galaxy.

  7. A Stellar Stream Surrounds the Whale Galaxy

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-10-01

    The -cold dark matter cosmological model predicts that galaxies are assembled through the disruption and absorption of small satellite dwarf galaxies by their larger hosts. A recent study argues that NGC 4631, otherwise known as the Whale galaxy, shows evidence of such a recent merger in the form of an enormous stellar stream extending from it.Stream SignaturesAccording to the -CDM model, stellar tidal streams should be a ubiquitous feature among galaxies. When satellite dwarf galaxies are torn apart, they spread out into such streams before ultimately feeding the host galaxy. Unfortunately, these streams are very faint, so were only recently starting to detect these features.Stellar tidal streams have been discovered around the Milky Way and Andromeda, providing evidence of these galaxies growth via recent (within the last 8 Gyr) mergers. But discovering stellar streams around other Milky Way-like galaxies would help us to determine if the model of hierarchical galaxy assembly applies generally.To this end, the Stellar Tidal Stream Survey, led by PI David Martnez-Delgado (Center for Astronomy of Heidelberg University), is carrying out the first systematic survey of stellar tidal streams. In a recent study, Martnez-Delgado and collaborators present their detection of a giant (85 kpc long!) stellar tidal stream extending into the halo of NGC 4631, the Whale galaxy.Modeling a SatelliteThe top image is a snapshot from an N-body simulation of a single dwarf satellite, 3.5 Gyr after it started interacting with the Whale galaxy. The satellite has been torn apart and spread into a stream that reproduces observations, which are shown in the lower image (scale is not the same). [Martnez-Delgado et al. 2015]The Whale galaxy is a nearby edge-on spiral galaxy interacting with a second spiral, NGC 4656. But the authors dont believe that the Whale galaxys giant tidal stellar stream is caused by its interactions with NGC 4656. Instead, based on their observations, they believe

  8. Is the Milky Way an interacting galaxy

    SciTech Connect

    Verschuur, G.L.

    1988-01-01

    The Milky Way Galaxy is an interacting galaxy, according to radio astronomers. The disk of stars we live in is linked to the Magellanic Clouds, our Galaxy's satellites, by an enormous arc of neutral hydrogen called the Magellanic Stream. These startling facts have recently been established by piecing together many seemingly unrelated bits of evidence into a new picture of our Milky Way Galaxy. The discoveries that led up to this grand picture of the Milky Way's interaction data back over fifty years to create one of the best detective stories in modern astronomy. The realization that ours is an interacting galaxy is only the latest result of an intensive effort to map the Milky Way. Since the 1930s, astronomers have tried to discover just how our Galaxy is built. Charting the Milky Way hasn't been easy, because we are inside it and our view of the Milky Way is obscured by cosmic dust. This dust creates a region called the zone of avoidance, a band centered along the galactic plane that blocks visible light from objects beyond nearby objects in the Galaxy. Thus radio astronomers have become the Milky Way mappers because cosmic radio waves penetrate the dust and reveal the grand scheme of our Galaxy.

  9. The star formation histories of local group dwarf galaxies. II. Searching for signatures of reionization

    SciTech Connect

    Weisz, Daniel R.; Dolphin, Andrew E.; Skillman, Evan D.; Holtzman, Jon; Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F.

    2014-07-10

    We search for signatures of reionization in the star formation histories (SFHs) of 38 Local Group dwarf galaxies (10{sup 4} < M{sub *} < 10{sup 9} M{sub ☉}). The SFHs are derived from color-magnitude diagrams using archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. Only five quenched galaxies (And V, And VI, And XIII, Leo IV, and Hercules) are consistent with forming the bulk of their stars before reionization, when full uncertainties are considered. Observations of 13 of the predicted 'true fossils' identified by Bovill and Ricotti show that only two (Hercules and Leo IV) indicate star formation quenched by reionization. However, both are within the virial radius of the Milky Way and evidence of tidal disturbance complicates this interpretation. We argue that the late-time gas capture scenario posited by Ricotti for the low mass, gas-rich, and star-forming fossil candidate Leo T is observationally indistinguishable from simple gas retention. Given the ambiguity between environmental effects and reionization, the best reionization fossil candidates are quenched low mass field galaxies (e.g., KKR 25).

  10. Testing Mergers as a Trigger for Quasars: Host Galaxy Morphologies

    NASA Astrophysics Data System (ADS)

    Hamilton, Timothy S.; Villforth, Carolin

    2016-01-01

    What makes a galaxy become active? It is often thought that galaxy mergers trigger the most luminous active galaxies (AGN)—quasars—but lower-luminosity AGN are started by milder processes. In our prior work, we analyzed a range of lower-luminosity AGN at redshifts of 0.5 < z < 0.7 and found no trend of rising merger incidence with luminosity.To reach the high luminosities thought to require mergers, we have now imaged 20 quasars to expand the range of the sample, using the Hubble's Wide Field Camera 3 in the H-band. We have used the Starfit software to remove the nuclear point sources and show the host galaxies beneath, allowing a comparison of galaxy properties. We now reveal the host morphologies and quantify their disturbances.

  11. Old Stellar Populations of The VGS Void Galaxies

    NASA Astrophysics Data System (ADS)

    Beygu, Burcu; Jarrett, Thomas; Jarrett, Tom; van de Weygaert, Rien; Kreckel, Kathryn; van der Hulst, Thijs; van Gorkom, Jacqueline

    2011-05-01

    Cosmic voids form an essential ingredient of the Cosmic Web and may harbour a systematically different population of galaxies. Largely unaffected by the complex processes modifying galaxies in high-density environments, the pristine and isolated void regions must hold important clues to the intrinsic process of formation and evolution of galaxies. The Void Galaxy Survey (VGS) is a multi-wavelength program to study 60 void galaxies. Each has been selected from the deepest interior regions of identified voids in the SDSS redshift survey on the basis of a unique geometric technique, with no a prior selection of intrinsic properties of the void galaxies. The project intends to study in detail the gas content, star formation history and stellar content, as well as kinematics and dynamics of void galaxies and their companions in a broad sample of void environments. It involves the HI imaging of the gas distribution in each of the VGS galaxies. Amongst its most tantalizing findings is the possible evidence for cold gas accretion in some of the most interesting objects, amongst which are a polar ring galaxy and a filamentary configuration of void galaxies. An essential aspect for understanding the formation and evolution of void galaxies concerns their star formation history. The current IRAC proposal is meant to study the older stellar population of void galaxies to constrain their assembly history.

  12. The dynamical fingerprint of core scouring in massive elliptical galaxies

    SciTech Connect

    Thomas, J.; Saglia, R. P.; Bender, R.; Erwin, P.; Fabricius, M.

    2014-02-10

    The most massive elliptical galaxies have low-density centers or cores that differ dramatically from the high-density centers of less massive ellipticals and bulges of disk galaxies. These cores have been interpreted as the result of mergers of supermassive black hole binaries, which depopulate galaxy centers by gravitationally slingshotting central stars toward large radii. Such binaries naturally form in mergers of luminous galaxies. Here, we analyze the population of central stellar orbits in 11 massive elliptical galaxies that we observed with the integral field spectrograph SINFONI at the European Southern Observatory Very Large Telescope. Our dynamical analysis is orbit-based and includes the effects of a central black hole, the mass distribution of the stars, and a dark matter halo. We show that the use of integral field kinematics and the inclusion of dark matter is important to conclude on the distribution of stellar orbits in galaxy centers. Six of our galaxies are core galaxies. In these six galaxies, but not in the galaxies without cores, we detect a coherent lack of stars on radial orbits in the core region and a uniform excess of radial orbits outside of it: when scaled by the core radius r{sub b} , the radial profiles of the classical anisotropy parameter β(r) are nearly identical in core galaxies. Moreover, they quantitatively match the predictions of black hole binary simulations, providing the first convincing dynamical evidence for core scouring in the most massive elliptical galaxies.

  13. Properties of satellite galaxies in nearby groups

    NASA Astrophysics Data System (ADS)

    Vennik, Jaan

    2016-10-01

    We studied the variation of stellar mass and various star-formation characteristics of satellite galaxies in a volume limited sample of nearby groups as a function of their group-centric distance and of their relative line-of-sight velocity in the group rest frame. We found clear radial dependencies, e.g. massive, red and passive satellites being distributed predominantly near the center of composite group. We also found some evidence of velocity modulation of star-forming properties of satellite galaxies near the group virial radius. We conclude that using kinematical data, it should be feasible to separate dynamical classes of bound, in-falling and 'backsplash' satellite galaxies.

  14. Disturbing the solar system. Impacts, close encounters, and coming attractions

    NASA Astrophysics Data System (ADS)

    Rubin, Alan E.

    The solar system is not akin to a well-oiled machine whose parts move smartly along prescribed paths. It has always been - and continues to be - a messy place in which gravity wreaks havoc. Moons form, asteroids and comets crash into planets, ice ages commence, and dinosaurs disappear. By describing the dramatic consequences of such disturbances, this fascinating book reveals the fundamental interconnectedness of the solar system - and what it means for life on its most interesting planet. After relating a brief history of the solar system, Alan Rubin describes how astronomers determined our location in the Milky Way. He provides succinct and up-to-date accounts of the energetic interactions among planetary bodies, the generation of the Earth's magnetic field, the effects of other solar-system objects on our climate, the moon's genesis, the heating of asteroids, and the origin of the mysterious tektites. Along the way, Rubin introduces us to the individual scientists - including the famous, the now obscure, and the newest generation of researchers - who have enhanced our understanding of the galactic neighborhood. He shows how scientific discoveries are made; he discusses the uncertainty that presides over the boundaries of knowledge as well as the occasional reluctance of scientists to change their minds even when confronted by compelling evidence. This fresh historical perspective reveals science as it is: an imperfect but self-correcting enterprise. Journeying to the frontiers of knowledge, Rubin concludes with the exciting realm of astrobiology. He chronicles the history of the search for life on Mars and describes cutting-edge lines of astrobiological inquiry, including panspermia (the possible transfer of life from planet to planet), the likelihood of technologically advanced alien civilizations in our galaxy, and our probable responses to alien contact.

  15. Galaxy and the solar system

    SciTech Connect

    Smoluchowski, R.; Bahcall, J.M.; Matthews, M.S.

    1986-01-01

    The solar-Galactic neighborhood, massive interstellar clouds and other Galactic features, the Oort cloud, perturbations of the solar system, and the existence and stability of a solar companion star are examined in chapters based on contributions to a conference held in Tucson, AZ during January 1985. The individual topics addressed include: the Galactic environment of the solar system; stars within 25 pc of the sun; the path of the sun in 100 million years; the local velocity field in the last billion years; interstellar clouds near the sun; and evidence for a local recent supernova. Also considered are: dynamic influence of Galactic tides and molecular clouds on the Oort cloud; cometary evidence for a solar companion; dynamical interactions between the Oort cloud and the Galaxy; geological periodicities and the Galaxy; giant comets and the Galaxy; dynamical evidence for Planet X; evolution of the solar system in the presence of a solar companion star; mass extinctions, crater ages, and comet showers; evidence for Nemesis, a solar companion star.

  16. SPATIAL ANISOTROPY OF GALAXY KINEMATICS IN SLOAN DIGITAL SKY SURVEY GALAXY CLUSTERS

    SciTech Connect

    Skielboe, Andreas; Wojtak, Radoslaw; Pedersen, Kristian; Rozo, Eduardo; Rykoff, Eli S.

    2012-10-10

    Measurements of galaxy cluster kinematics are important in understanding the dynamical state and evolution of clusters of galaxies, as well as constraining cosmological models. While it is well established that clusters exhibit non-spherical geometries, evident in the distribution of galaxies on the sky, azimuthal variations of galaxy kinematics within clusters have yet to be observed. Here we measure the azimuthal dependence of the line-of-sight velocity dispersion profile in a stacked sample of 1743 galaxy clusters from the Sloan Digital Sky Survey (SDSS). The clusters are drawn from the SDSS DR8 redMaPPer catalog. We find that the line-of-sight velocity dispersion of galaxies lying along the major axis of the central galaxy is larger than those that lie along the minor axis. This is the first observational detection of anisotropic kinematics of galaxies in clusters. We show that the result is consistent with predictions from numerical simulations. Furthermore, we find that the degree of projected anisotropy is strongly dependent on the line-of-sight orientation of the galaxy cluster, opening new possibilities for assessing systematics in optical cluster finding.

  17. Merging Galaxies Create a Binary Quasar

    NASA Astrophysics Data System (ADS)

    2010-02-01

    Astronomers have found the first clear evidence of a binary quasar within a pair of actively merging galaxies. Quasars are the extremely bright centers of galaxies surrounding super-massive black holes, and binary quasars are pairs of quasars bound together by gravity. Binary quasars, like other quasars, are thought to be the product of galaxy mergers. Until now, however, binary quasars have not been seen in galaxies that are unambiguously in the act of merging. But images of a new binary quasar from the Carnegie Institution's Magellan telescope in Chile show two distinct galaxies with "tails" produced by tidal forces from their mutual gravitational attraction. "This is really the first case in which you see two separate galaxies, both with quasars, that are clearly interacting," says Carnegie astronomer John Mulchaey who made observations crucial to understanding the galaxy merger. Most, if not all, large galaxies, such as our galaxy the Milky Way, host super-massive black holes at their centers. Because galaxies regularly interact and merge, astronomers have assumed that binary super-massive black holes have been common in the Universe, especially during its early history. Black holes can only be detected as quasars when they are actively accreting matter, a process that releases vast amounts of energy. A leading theory is that galaxy mergers trigger accretion, creating quasars in both galaxies. Because most such mergers would have happened in the distant past, binary quasars and their associated galaxies are very far away and therefore difficult for most telescopes to resolve. The binary quasar, labeled SDSS J1254+0846, was initially detected by the Sloan Digital Sky Survey, a large scale astronomical survey of galaxies and over 120,000 quasars. Further observations by Paul Green of the Harvard-Smithsonian Center for Astrophysics and colleagues* using NASA's Chandra's X-ray Observatory and telescopes at Kitt Peak National Observatory in Arizona and Palomar

  18. Strong C+ Emission in Galaxies at z ~ 1-2: Evidence for Cold Flow Accretion Powered Star Formation in the Early Universe

    NASA Astrophysics Data System (ADS)

    Brisbin, Drew; Ferkinhoff, Carl; Nikola, Thomas; Parshley, Stephen; Stacey, Gordon J.; Spoon, Henrik; Hailey-Dunsheath, Steven; Verma, Aprajita

    2015-01-01

    We have recently detected the [C II] 157.7 μm line in eight star-forming galaxies at redshifts 1 to 2 using the redshift (z) Early Universe Spectrometer (ZEUS). Our sample targets star formation dominant sources detected in PAH emission. This represents a significant addition to [C II] observations during the epoch of peak star formation. We have augmented this survey with observations of the [O I] 63 μm line and far infrared photometry from the PACS and SPIRE Herschel instruments as well as Spitzer IRS spectra from the literature showing PAH features. Our sources exhibit above average gas heating efficiency, many with both [O I]/FIR and [C II]/FIR of ~1% or more. The relatively strong [C II] emission is consistent with our sources being dominated by star formation powered photo-dissociation regions, extending to kiloparsec scales. We suggest that the star formation mode in these systems follows a Schmidt-Kennicutt law similar to local systems, but at a much higher rate due to molecular gas surface densities 10-100 times that of local star-forming systems. The source of the high molecular gas surface densities may be the infall of neutral gas from the cosmic web. In addition to the high [C II]/FIR values, we also find high [C II]/PAH ratios and, in at least one source, a cool dust temperature. This source, SWIRE 4-5, bears a resemblance in these diagnostics to shocked regions of Stephan's Quintet, suggesting that another mode of [C II] excitation in addition to normal photoelectric heating may be contributing to the observed [C II] line.

  19. STRONG C{sup +} EMISSION IN GALAXIES AT z ∼ 1-2: EVIDENCE FOR COLD FLOW ACCRETION POWERED STAR FORMATION IN THE EARLY UNIVERSE

    SciTech Connect

    Brisbin, Drew; Ferkinhoff, Carl; Nikola, Thomas; Parshley, Stephen; Spoon, Henrik; Stacey, Gordon J.; Hailey-Dunsheath, Steven; Verma, Aprajita

    2015-01-20

    We have recently detected the [C II] 157.7 μm line in eight star-forming galaxies at redshifts 1 to 2 using the redshift (z) Early Universe Spectrometer (ZEUS). Our sample targets star formation dominant sources detected in PAH emission. This represents a significant addition to [C II] observations during the epoch of peak star formation. We have augmented this survey with observations of the [O I] 63 μm line and far infrared photometry from the PACS and SPIRE Herschel instruments as well as Spitzer IRS spectra from the literature showing PAH features. Our sources exhibit above average gas heating efficiency, many with both [O I]/FIR and [C II]/FIR of ∼1% or more. The relatively strong [C II] emission is consistent with our sources being dominated by star formation powered photo-dissociation regions, extending to kiloparsec scales. We suggest that the star formation mode in these systems follows a Schmidt-Kennicutt law similar to local systems, but at a much higher rate due to molecular gas surface densities 10-100 times that of local star-forming systems. The source of the high molecular gas surface densities may be the infall of neutral gas from the cosmic web. In addition to the high [C II]/FIR values, we also find high [C II]/PAH ratios and, in at least one source, a cool dust temperature. This source, SWIRE 4-5, bears a resemblance in these diagnostics to shocked regions of Stephan's Quintet, suggesting that another mode of [C II] excitation in addition to normal photoelectric heating may be contributing to the observed [C II] line.

  20. A RECOLLIMATION SHOCK 80 mas FROM THE CORE IN THE JET OF THE RADIO GALAXY 3C 120: OBSERVATIONAL EVIDENCE AND MODELING

    SciTech Connect

    Agudo, Ivan; Gomez, Jose L.; Casadio, Carolina; Roca-Sogorb, Mar; Cawthorne, Timothy V.

    2012-06-20

    We present Very Long Baseline Array observations of the radio galaxy 3C 120 at 5, 8, 12, and 15 GHz designed to study a peculiar stationary jet feature (hereafter C80) located {approx}80 mas from the core, which was previously shown to display a brightness temperature {approx}600 times larger than expected at such distances. The high sensitivity of the images-obtained between 2009 December and 2010 June-has revealed that C80 corresponds to the eastern flux density peak of an arc of emission (hereafter A80), downstream of which extends a large ({approx}20 mas in size) bubble-like structure that resembles an inverted bow shock. The linearly polarized emission closely follows that of the total intensity in A80, with the electric vector position angle distributed nearly perpendicular to the arc-shaped structure. Despite the stationary nature of C80/A80, superluminal components with speeds up to 3 {+-} 1 c have been detected downstream from its position, resembling the behavior observed in the HST-1 emission complex in M87. The total and polarized emission of the C80/A80 structure, its lack of motion, and brightness temperature excess are best reproduced by a model based on synchrotron emission from a conical shock with cone opening angle {eta} = 10 Degree-Sign , jet viewing angle {theta} = 16 Degree-Sign , a completely tangled upstream magnetic field, and upstream Lorentz factor {gamma}{sub u} = 8.4. The good agreement between our observations and numerical modeling leads us to conclude that the peculiar feature associated with C80/A80 corresponds to a conical recollimation shock in the jet of 3C 120 located at a de-projected distance of {approx}190 pc downstream from the nucleus.

  1. Binary pairs of supermassive black holes - Formation in merging galaxies

    NASA Astrophysics Data System (ADS)

    Valtaoja, L.; Valtonen, M. J.; Byrd, G. G.

    1989-08-01

    A process in which supermassive binary blackholes are formed in nuclei of supergiant galaxies due to galaxy mergers is examined. There is growing evidence that mergers of galaxies are common and that supermassive black holes in center of galaxies are also common. Consequently, it is expected that binary black holes should arise in connection with galaxy mergers. The merger process in a galaxy modeled after M87 is considered. The capture probability of a companion is derived as a function of its mass. Assuming a correlation between the galaxy mass and the blackholes mass, the expected mass ratio in binary black holes is calculated. The binary black holes formed in this process are long lived, surviving longer than the Hubble time unless they are perturbed by black holes from successive mergers. The properties of these binaries agree with Gaskell's (1988) observational work on quasars and its interpretation in terms of binary black holes.

  2. Isolated Galaxies versus Interacting Pairs with MaNGA

    NASA Astrophysics Data System (ADS)

    Fernández, María; Yuan, Fangting; Shen, Shiyin; Yin, Jun; Chang, Ruixiang; Feng, Shuai

    2015-10-01

    We present preliminary results of the spectral analysis on the radial distributions of the star formation history in both, a galaxy merger and a spiral isolated galaxy observed with MaNGA. We find that the central part of the isolated galaxy is composed by older stellar population ($\\sim$2 Gyr) than in the outskirts ($\\sim$7 Gyr). Also, the time-scale is gradually larger from 1 Gyr in the inner part to 3 Gyr in the outer regions of the galaxy. In the case of the merger, the stellar population in the central region is older than in the tails, presenting a longer time-scale in comparison to central part in the isolated galaxy. Our results are in agreement with a scenario where spiral galaxies are built from inside-out. In the case of the merger, we find evidence that interactions enhance star formation in the central part of the galaxy.

  3. Chronic stress, catecholamines, and sleep disturbance at Three Mile Island.

    PubMed

    Davidson, L M; Fleming, R; Baum, A

    1987-01-01

    The present study was concerned with the relationship between chronic stress and sleep disturbance. Previous research has provided evidence of chronic stress responding among people living near the Three Mile Island nuclear generating facility. Compared to control subjects, the TMI group has exhibited greater symptom reporting, poorer performance on behavioral measures of concentration, and elevated levels of urinary norepinephrine and epinephrine. Other research has suggested a relationship between arousal and insomnia. The extent to which stress and sleep disturbances were experienced by residents at TMI was examined and compared to levels of stress and sleep disturbance among a group of control subjects. The relationship between stress and sleep disturbances was also examined. Results indicated that TMI area residents exhibited more stress than the controls and reported greater disturbance of sleep. Modest relationships among stress and sleep measures suggested that the symptoms of stress measured in this study were not primary determinants of sleep problems. PMID:3611754

  4. Tides, Interactions, and Fine-Scale Substructures in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Conselice, Christopher J.; Gallagher, John S., III

    1999-01-01

    We present the results of a study on galaxy interactions, tides, and other processes that produce luminous fine-scale substructures in the galaxy clusters: Coma, Perseus, Abell 2199, AWM 3, and AWM 5. All unusual structures in these clusters can be categorized into seven morphologies: interacting galaxies, multiple galaxies (noninteracting), distorted galaxies, tailed galaxies, line galaxies, dwarf galaxy groups, and galaxy aggregates. The various morphologies are described, and a catalog is presented, of 248 objects in these five clusters along with color, and positional information obtained from CCD images taken with the WIYN 3.5 m telescope in broadband B and R filters. Distorted, interacting, and fine-scale substructures have a range of colors extending from blue objects with B-R~0 to redder colors at B-R~2.5. We also find that the structures with the most disturbed morphology have the bluest colors. In addition, the relative number distributions of these structures suggest that two separate classes of galaxy clusters exist: one dominated by distorted structures and the other dominated by galaxy associations. The Coma and Perseus clusters, respectively, are proposed as models for these types of clusters. These structures avoid the deep potentials of the dominant D or cD galaxies in the Coma and Perseus clusters, and tend to clump together. Possible mechanisms for the production of fine-scale substructure are reviewed and compared with observations of z~0.4 Butcher-Oemler clusters. We conclude, based on color, positional, and statistical data, that the most likely mechanism for the creation of these structures is through an interaction with the gravitational potential of the cluster, possibly coupled with effects of weak interactions with cluster ellipticals.

  5. Star Formation in Irregular Galaxies.

    ERIC Educational Resources Information Center

    Hunter, Deidre; Wolff, Sidney

    1985-01-01

    Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

  6. Star Formation and Feedback in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Dong, Shawfeng; Lin, D. N. C.; Murray, S. D.

    2003-10-01

    We examine the star formation history and stellar feedback effects of dwarf galaxies under the influence of extragalactic ultraviolet radiation. Previous work has indicated that the background UV flux can easily ionize the gas within typical dwarf galaxies, delaying or even preventing cooling and star formation within them. Many dwarf galaxies within the Local Group are, however, observed to contain multiple generations of stars, the oldest of which formed in the early epochs of cosmic evolution, when the background UV flux was intense. In order to address this paradox, we consider the dynamical evolution of gas in dwarf galaxies using a one-dimensional, spherically symmetric, Lagrangian numerical scheme to compute the effects of radiative transfer and photoionization. We include a physically motivated star formation recipe and consider the effects of feedback. This scheme allows us to follow the history of the gas and of star formation within dwarf galaxies, as influenced by both external and internal UV radiation. Our results indicate that star formation in the severe environment of dwarf galaxies is a difficult and inefficient process. In potentials with total mass less than a few times 106 Msolar and velocity dispersion less than a few kilometers per second, residual gas is efficiently photoionized by cosmic background UV radiation. Since the density scale height of the gas within these galaxies is comparable to their size, gas may be tidally removed from them, leaving behind starless residual dark matter clumps. For intermediate-mass systems, such as the dSphs around the Galaxy, star formation can proceed within early cosmic epochs despite the intense background UV flux. Triggering processes such as merger events, collisions, and tidal disturbance can lead to density enhancements, reducing the recombination timescale, allowing gas to cool and star formation to proceed. However, the star formation and gas retention efficiency may vary widely in galaxies with

  7. Suites of dwarfs around Nearby giant galaxies

    SciTech Connect

    Karachentsev, Igor D.; Kaisina, Elena I.; Makarov, Dmitry I. E-mail: kei@sao.ru

    2014-01-01

    The Updated Nearby Galaxy Catalog (UNGC) contains the most comprehensive summary of distances, radial velocities, and luminosities for 800 galaxies located within 11 Mpc from us. The high density of observables in the UNGC makes this sample indispensable for checking results of N-body simulations of cosmic structures on a ∼1 Mpc scale. The environment of each galaxy in the UNGC was characterized by a tidal index Θ{sub 1}, depending on the separation and mass of the galaxy's main disturber (MD). We grouped UNGC galaxies with a common MD in suites, and ranked suite members according to their Θ{sub 1}. All suite members with positive Θ{sub 1} are assumed to be physical companions of the MD. About 58% of the sample are members of physical groups. The distribution of suites by the number of members, n, follows a relation N(n) ∼ n {sup –2}. The 20 most populated suites contain 468 galaxies, i.e., 59% of the UNGC sample. The fraction of MDs among the brightest galaxies is almost 100% and drops to 50% at M{sub B} = –18{sup m}. We discuss various properties of MDs, as well as galaxies belonging to their suites. The suite abundance practically does not depend on the morphological type, linear diameter, or hydrogen mass of the MD, the tightest correlation being with the MD dynamical mass. Dwarf galaxies around MDs exhibit well-known segregation effects: the population of the outskirts has later morphological types, richer H I contents, and higher rates of star formation activity. Nevertheless, there are some intriguing cases where dwarf spheroidal galaxies occur at the far periphery of the suites, as well as some late-type dwarfs residing close to MDs. Comparing simulation results with galaxy groups, most studies assume the Local Group is fairly typical. However, we recognize that the nearby groups significantly differ from each other and there is considerable variation in their properties. The suites of companions around the Milky Way and M31, consisting of the

  8. The High-Risk (Disturbed and Disturbing) College Student

    ERIC Educational Resources Information Center

    Hollingsworth, Kathy R.; Dunkle, John H.; Douce, Louise

    2009-01-01

    The disturbed and disturbing college student causes the most vexing concerns for student affairs administrators. The Assessment-Intervention of Student Problems (AISP) model offers a useful and easily understood framework for dealing with the various challenges of this high-risk student population. This chapter focuses on changes that have…

  9. BV photometry of five shell galaxies

    NASA Astrophysics Data System (ADS)

    Pierfederici, F.; Rampazzo, R.

    2004-06-01

    Current views consider shell structures as bona fide signatures of a recent minor/major merging event though also weak interaction models (WIM) could produce long lasting shells on host galaxies possessing a stellar thick disc. We present a B V band photometric study of a sample of 5 shell galaxies belonging to the Malin & Carter (1983) compilation. The structural properties and colors of the galaxies, as well as the colors of their shells are examined in detail. We did not find signatures of the presence of double nuclei. NGC 7585 is the only E galaxy in the sample and has a moderately boxy structure. The other galaxies have either a discy structure or are mixed E/S0 type galaxies. NGC 474 is a true lenticular. NGC 6776 shows a diffuse asymmetric outer structure and a system of tails of the the same color of the galaxy body; but not clear shells. In general, the color of the shells in our sample is similar or slightly redder than that of the host galaxy, whose color, in turn, is typical of the early-type morphological class. One of the outer shells of NGC 474 is significantly bluer than the body of the galaxy. Since NGC 474 appears to be interacting with NGC 470, the color of this one shell could be explained as result of a recent acquisition of material through tidal interaction. The WIM hypothesis could explain both the red and the blue shells of NGC 474, this latter acquired from the fly-by of the nearby companion NGC 470, but the lack of the constancy of shell surface brightness as a ratio of the underlying galaxy brightness argues against WIM. We speculate about evidence, which also comes from different observations, that suggests a merging/accretion origin of the shells. Based on observations obtained at the Observatoire de Haute Provence, CNRS, Saint Michel l'Observatoire, France and ESO, La Silla, Chile

  10. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    SciTech Connect

    Park, Youngsoo; Krause, Elisabeth; Dodelson, Scott; Jain, Bhuvnesh; Amara, Adam; Becker, Matt; Bridle, Sarah; Clampitt, Joseph; Crocce, Martin; Honscheid, Klaus; Gaztanaga, Enrique; Sanchez, Carles; Wechsler, Risa

    2015-01-01

    Combining galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth rate of large scale structure, a quantity that will shed light on the mechanism driving the acceleration of the Universe. The Dark Energy Survey (DES) is a prime candidate for such an analysis, with its measurements of both the distribution of galaxies on the sky and the tangential shears of background galaxies induced by these foreground lenses. By constructing an end-to-end analysis that combines large-scale galaxy clustering and small-scale galaxy-galaxy lensing, we also forecast the potential of a combined probes analysis on DES datasets. In particular, we develop a practical approach to a DES combined probes analysis by jointly modeling the assumptions and systematics affecting the different components of the data vector, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. Furthermore, we study the effect of external priors on different subsets of these parameters. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the universe, conservatively/ optimistically constraining the growth function to 8%/4.9% with its first-year data covering 1000 square degrees, and to 4%/2.3% with its full five-year data covering 5000 square degrees.

  11. Galaxies as gravitational lenses.

    PubMed

    Barnothy, J; Barnothy, M F

    1968-10-18

    Of all the galaxies in the visible part of the universe, 500 million are seen through intervening galaxies. In some instances the foreground galaxy will act as a gravitational lens and produce distorted and (in brightness) greatly amplified images of the galaxy behind it; such images may simulate starlike superluminous objects such as quasars (quasi-stellar objects). The number of gravitational lenses is several times greater than the number of quasars yet observed. In other instances the superposition of the image upon a visible foreground galaxy may simulate morphological configurations resembling N-type, dumbbell, spiral, or barred-spiral galaxies. PMID:17836654

  12. SUPERDENSE MASSIVE GALAXIES IN WINGS LOCAL CLUSTERS

    SciTech Connect

    Valentinuzzi, T.; D'Onofrio, M.; Fritz, J.; Poggianti, B. M.; Bettoni, D.; Fasano, G.; Moretti, A.; Omizzolo, A.; Varela, J.; Cava, A.; Couch, W. J.; Dressler, A.; Moles, M.; Kjaergaard, P.; Vanzella, E.

    2010-03-20

    Massive quiescent galaxies at z > 1 have been found to have small physical sizes, and hence to be superdense. Several mechanisms, including minor mergers, have been proposed for increasing galaxy sizes from high- to low-z. We search for superdense massive galaxies in the WIde-field Nearby Galaxy-cluster Survey (WINGS) of X-ray selected galaxy clusters at 0.04 < z < 0.07. We discover a significant population of superdense massive galaxies with masses and sizes comparable to those observed at high redshift. They approximately represent 22% of all cluster galaxies more massive than 3 x 10{sup 10} M{sub sun}, are mostly S0 galaxies, have a median effective radius (R{sub e} ) = 1.61 +- 0.29 kpc, a median Sersic index (n) = 3.0 +- 0.6, and very old stellar populations with a median mass-weighted age of 12.1 +- 1.3 Gyr. We calculate a number density of 2.9 x 10{sup -2} Mpc{sup -3} for superdense galaxies in local clusters, and a hard lower limit of 1.3 x 10{sup -5} Mpc{sup -3} in the whole comoving volume between z = 0.04 and z = 0.07. We find a relation between mass, effective radius, and luminosity-weighted age in our cluster galaxies, which can mimic the claimed evolution of the radius with redshift, if not properly taken into account. We compare our data with spectroscopic high-z surveys and find that-when stellar masses are considered-there is consistency with the local WINGS galaxy sizes out to z {approx} 2, while a discrepancy of a factor of 3 exists with the only spectroscopic z > 2 study. In contrast, there is strong evidence for a large evolution in radius for the most massive galaxies with M{sub *} > 4 x 10{sup 11} M{sub sun} compared to similarly massive galaxies in WINGS, i.e., the brightest cluster galaxies.

  13. Persistent effects of physical disturbance on meiobenthos in mangrove sediments.

    PubMed

    Dye, A H

    2006-12-01

    Disturbance is an important factor in structuring ecological communities, exerting its influence through changes to the physical environment and to the trajectories of successional processes. Marine environments are subject to a wide range of disturbances and while much is known about the effects of disturbance on macrobenthos in unconsolidated sediments, little is known about the responses of meiobenthos to disturbance in consolidated sediments, such as mangroves. Trampling was used to study the response of meiobenthos to disturbance in mangrove sediments. Even light trampling appeared to break up the mangrove root mat and increased the proportion of fine sediment. Densities of meiobenthos increased 2-3-fold in disturbed sediments, but there was no evidence of disproportionate abundance. Temporal variability was similar in all treatments, but spatial variability increased 4-5-fold in disturbed sediments. Effects persisted for at least 24 months, with little evidence of convergence of treatments. Meiobenthos may have exploited the increase in habitat resulting from loss of the root mat and possibly benefited from increased food from the decomposition of root material. These effects are likely to persist for several years because of the minimal recovery of the root mat. PMID:16860385

  14. Geomagnetic disturbance and the orientation of nocturnally migrating birds.

    PubMed

    Moore, F R

    1977-05-01

    Free-flying passerine migrants respond to natural fluctuations in the earth's magnetic field. The variability in flight directions of nocturnal migrants is significantly correlated with increasing geomagnetic disturbance as measured by both the K index and various components of the earth's magnetic field. The results indicate that such disturbances influence the orientation of free-flying migrants, but the evidence is not sufficient to show that geomagnetism is a cue in their orientation system. PMID:854743

  15. Sleep disturbance and cardiovascular risk in adolescents

    PubMed Central

    Narang, Indra; Manlhiot, Cedric; Davies-Shaw, Jolie; Gibson, Don; Chahal, Nita; Stearne, Karen; Fisher, Amanda; Dobbin, Stafford; McCrindle, Brian W.

    2012-01-01

    Background: Evidence suggests that inadequate or disturbed sleep is associated with increased cardiovascular risk in adults. There are limited data on sleep quality and associated cardiovascular risk in children. Methods: We obtained data on adolescents from the 2009/10 cycle of the Healthy Heart Schools’ Program, a population-based cross-sectional study in the Niagara region of Ontario. Participants underwent measurements of cardiometabolic risk factors, including body mass index (BMI), lipid profile and blood pressure, and they completed questionnaires measuring sleeping habits and nutritional status. We assessed sleep disturbance using the sleep disturbance score derived from the Pittsburgh Sleep Quality Index. We explored associations between sleeping habits and cardiovascular risk factors. Results: Among 4104 adolescents (51% male), the mean hours of sleep per night (± standard deviation) were 7.9 ± 1.1 on weeknights and 9.4 ± 1.6 on weekends. In total, 19% of participants reported their sleep quality as fairly bad or very bad on weeknights and 10% reported it as fairly bad or very bad on weekends. In the multivariable regression models, a higher sleep disturbance score was associated with increased odds of being at high cardiovascular risk (highest v. lowest tertile odds ratio [OR] 1.43 [95% confidence interval (CI) 1.16–1.77], p < 0.001), increased odds of hypertension (highest v. lowest tertile OR 1.44 [95% CI 1.02–2.05], p = 0.05) and increased odds of elevated non-high density lipoprotein cholesterol (highest v. lowest tertile OR 1.28 [95% CI 1.00–1.64], p = 0.05). The mean duration of sleep was not associated with these outcomes. Interpretation: In healthy adolescents, sleep disturbance is associated with cardiovascular risk factor abnormalities. Intervention strategies to optimize sleep hygiene early in life may be important for the prevention of cardiovascular disease. PMID:23027917

  16. Study of the Lynx-Cancer void galaxies. - V. The extremely isolated galaxy UGC 4722

    NASA Astrophysics Data System (ADS)

    Chengalur, J. N.; Pustilnik, S. A.; Makarov, D. I.; Perepelitsyna, Y. A.; Safonova, E. S.; Karachentsev, I. D.

    2015-04-01

    We present a detailed study of the extremely isolated Sdm galaxy UGC 4722 (MB = -17.4) located in the nearby Lynx-Cancer void. UGC 4722 is a member of the Catalogue of Isolated Galaxies, and has also been identified as one of the most isolated galaxies in the Local Supercluster. Optical images of the galaxy however show that it has a peculiar morphology with an elongated ˜14 kpc-long plume. New observations with the Russian 6-m telescope (BTA) and the Giant Metrewave Radio Telescope (GMRT) of the ionized and neutral gas in UGC 4722 reveal the second component responsible for the disturbed morphology of the system. This is a small, almost completely destroyed, very gas-rich dwarf (MB = -15.2, M(H I)/LB ˜ 4.3) We estimate the oxygen abundance for both galaxies to be 12 + log (O/H) ˜ 7.5-7.6 which is two to three times lower than what is expected from the luminosity-metallicity relation for similar galaxies in denser environments. The ugr colours of the plume derived from Sloan Digital Sky Survey (SDSS) images are consistent with a simple stellar population with a post starburst age of 0.45-0.5 Gyr. This system hence appears to be the first known case of a minor merger with a prominent tidal feature consisting of a young stellar population.

  17. Interventions for Sleep Disturbance in Bipolar Disorder

    PubMed Central

    Harvey, Allison G.; Kaplan, Kate A.; Soehner, Adriane

    2015-01-01

    Synopsis Bipolar disorder is a severe and chronic disorder, ranked in the top 10 leading causes of disability worldwide. Sleep disturbances are strongly coupled with inter-episode dysfunction and symptom worsening in bipolar disorder. Experimental studies suggest that sleep deprivation can trigger manic relapse. There is evidence that sleep deprivation can have an adverse impact on emotion regulation the following day. The clinical management of the sleep disturbances experienced by bipolar patients, including insomnia, hypersomnia delayed sleep phase and irregular sleep-wake schedule, may include medication approaches, psychological interventions, light therapies and sleep deprivation. Psychological interventions, as described here, are advantageous in that they are low in side effects, may be preferred by patients, are durable and have no abuse potential. PMID:25750600

  18. A Zoo of Galaxies

    NASA Astrophysics Data System (ADS)

    Masters, Karen L.

    2015-03-01

    We live in a universe filled with galaxies with an amazing variety of sizes and shapes. One of the biggest challenges for astronomers working in this field is to understand how all these types relate to each other in the background of an expanding universe. Modern astronomical surveys (like the Sloan Digital Sky Survey) have revolutionised this field of astronomy, by providing vast numbers of galaxies to study. The sheer size of the these databases made traditional visual classification of the types galaxies impossible and in 2007 inspired the Galaxy Zoo project (www.galaxyzoo.org); starting the largest ever scientific collaboration by asking members of the public to help classify galaxies by type and shape. Galaxy Zoo has since shown itself, in a series of now more than 30 scientific papers, to be a fantastic database for the study of galaxy evolution. In this Invited Discourse I spoke a little about the historical background of our understanding of what galaxies are, of galaxy classification, about our modern view of galaxies in the era of large surveys. I finish with showcasing some of the contributions galaxy classifications from the Galaxy Zoo project are making to our understanding of galaxy evolution.

  19. ACTIVE GALACTIC NUCLEI AND THE TRUNCATION OF STAR FORMATION IN K+A GALAXIES

    SciTech Connect

    Brown, Michael J. I.; Palamara, David; Moustakas, John; Caldwell, Nelson; Cool, Richard J.; Zaritsky, Dennis; Dey, Arjun; Jannuzi, Buell T.; Hickox, Ryan C.; Murray, Stephen S.

    2009-09-20

    We have searched for active galactic nuclei (AGNs) in K+A galaxies, using multiwavelength imaging and spectroscopy in the Booetes field of the NOAO Deep Wide-Field Survey. The K+A galaxies, which have had their star formation rapidly truncated, are selected via their strong Balmer absorption lines and weak Halpha emission. Our sample consists of 24 K+A galaxies selected from 6594 0.10 < z < 0.35 galaxies brighter than I = 20 with optical spectroscopy from the AGN and Galaxy Evolution Survey. Two thirds of the K+A galaxies are likely ongoing galaxy mergers, with nearby companion galaxies or tidal tails. Galaxy mergers may be responsible for the truncation of star formation, or we are observing the aftermath of merger triggered starbursts. As expected, the optical colors of K+A galaxies largely fall between blue galaxies with ongoing star formation and red passive galaxies. However, only 1% of the galaxies with colors between the red and blue populations are K+A galaxies, and we conclude that the truncation of star formation in K+A galaxies must have been unusually abrupt ({approx}<100 Myr). We examined the AGN content of K+A galaxies with both optical emission-line ratios (BPT diagrams) and Chandra X-ray imaging. At least half of all K+A galaxies display the optical emission-line ratios of AGNs, and a third of M{sub R} < -22 K+A galaxies host AGNs with X-ray luminosities of {approx}10{sup 42} erg s{sup -1}. The faintest K+A galaxies do not show clear evidence for hosting AGNs, having emission-line ratios consistent with photoionization by massive stars and few X-ray detections. We speculate that two mechanisms may be responsible for the truncation of star formation in K+A galaxies, with AGN feedback only playing a role in M{sub R} {approx}< -20.5 galaxies.

  20. Subclassification of School Phobic Disturbances.

    ERIC Educational Resources Information Center

    Atkinson, Leslie; And Others

    The confusion surrounding all aspects of school refusal may rest partly on the misguided assumption that the disturbance represents a single syndrome. Five consistently emerging variables which may help distinguish among school phobic types were abstracted from the literature: extensiveness of disturbance, mode of onset, age, fear source, and…

  1. Population of the Galaxy

    SciTech Connect

    Troitskii, V.

    1981-09-01

    A new theory of the population of the Galaxy, based on the hypothesis of explosive: simultaneous and one-time-origination of life in the universe at a certain moment of its evolutionary development, is discussed in the report. According to the proposed theory, civilizations began to arise around the present moment of the history of the universe. Their possible number is limited even when their lifetime is unlimited. The age and number of simultaneously existing civilizations when their lifetime is unlimited is determined by the duration and dispersion of the time of evolution of life on different planets from the cell level to civilization. The proposed theory explains better than Drake's theory the negative results of the search for evidence of the existence of superpowerful extraterrestrial civilizations and the noncolonization of the earth.

  2. Galaxy interactions and strength of nuclear activity

    NASA Technical Reports Server (NTRS)

    Simkin, S. M.

    1990-01-01

    Analysis of data in the literature for differential velocities and projected separations of nearby Seyfert galaxies with possible companions shows a clear difference in projected separations between type 1's and type 2's. This kinematic difference between the two activity classes reinforces other independent evidence that their different nuclear characteristics are related to a non-nuclear physical distinction between the two classes. The differential velocities and projected separations of the galaxy pairs in this sample yield mean galaxy masses, sizes, and mass to light ratios which are consistent with those found by the statistical methods of Karachentsev. Although the galaxy sample discussed here is too small and too poorly defined to provide robust support for these conclusions, the results strongly suggest that nuclear activity in Seyfert galaxies is associated with gravitational perturbations from companion galaxies, and that there are physical distinctions between the host companions of Seyfert 1 and Seyfert 2 nuclei which may depend both on the environment and the structure of the host galaxy itself.

  3. Star Formation in Galaxies

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Topics addressed include: star formation; galactic infrared emission; molecular clouds; OB star luminosity; dust grains; IRAS observations; galactic disks; stellar formation in Magellanic clouds; irregular galaxies; spiral galaxies; starbursts; morphology of galactic centers; and far-infrared observations.

  4. Galaxy NGC 300

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the nearby spiral galaxy NGC 300 was taken by Galaxy Evolution Explorer in a single orbit exposure of 27 minutes on October 10, 2003. NGC 300 lies 7 million light years from our Milky Way galaxy and is one of a group of galaxies in the constellation Sculptor. NGC 300 is often used as a prototype of a spiral galaxy because in optical images it displays flowing spiral arms and a bright central region of older (and thus redder) stars. The Galaxy Evolution Explorer image taken in ultraviolet light shows us that NGC 300 is an efficient star-forming galaxy. The bright blue regions in the Galaxy Evolution Explorer image reveal new stars forming all the way into the nucleus of NGC 300.

  5. Dynamics of galaxy structures in the Local Volume

    NASA Astrophysics Data System (ADS)

    Karachentsev, I. D.

    2016-10-01

    I consider a sample of `Updated Nearby Galaxy Catalog' that contains eight hundred objects within 11 Mpc. Environment of each galaxy is characterized by a tidal index Θ1 depending on separation and mass of the galaxy Main Disturber (=MD). The UNGC galaxies with a common MD are ascribed to its `suite' and ranked according to their Θ1. Fifteen the most populated suites contain more than half of the UNGC sample. The fraction of MDs among the brightest galaxies is almost 100% and drops to 50% at M_B = -18 mag. The observational properties of galaxies accumulated in UNGC are used to derive orbital masses of giant galaxies via motions of their satellites. The average orbital-to-stellar mass ratio for them is M orb M* ~= 30, corresponding to the mean local density of matter Ωm ~= 0.09, i.e 1/3 of the global cosmic one. The dark-to-stellar mass ratio for the Milky Way and M31 is typical for other neighboring giant galaxies.

  6. Western Disturbances: A review

    NASA Astrophysics Data System (ADS)

    Dimri, A. P.; Niyogi, D.; Barros, A. P.; Ridley, J.; Mohanty, U. C.; Yasunari, T.; Sikka, D. R.

    2015-06-01

    Cyclonic storms associated with the midlatitude Subtropical Westerly Jet (SWJ), referred to as Western Disturbances (WDs), play a critical role in the meteorology of the Indian subcontinent. WDs embedded in the southward propagating SWJ produce extreme precipitation over northern India and are further enhanced over the Himalayas due to orographic land-atmosphere interactions. During December, January, and February, WD snowfall is the dominant precipitation input to establish and sustain regional snowpack, replenishing regional water resources. Spring melt is the major source of runoff to northern Indian rivers and can be linked to important hydrologic processes from aquifer recharge to flashfloods. Understanding the dynamical structure, evolution-decay, and interaction of WDs with the Himalayas is therefore necessary to improve knowledge which has wide ranging socioeconomic implications beyond short-term disaster response including cold season agricultural activities, management of water resources, and development of vulnerability-adaptive measures. In addition, WD wintertime precipitation provides critical mass input to existing glaciers and modulates the albedo characteristics of the Himalayas and Tibetan Plateau, affecting large-scale circulation and the onset of the succeeding Indian Summer Monsoon. Assessing the impacts of climate variability and change on the Indian subcontinent requires fundamental understanding of the dynamics of WDs. In particular, projected changes in the structure of the SWJ will influence evolution-decay processes of the WDs and impact Himalayan regional water availability. This review synthesizes past research on WDs with a perspective to provide a comprehensive assessment of the state of knowledge to assist both researchers and policymakers, and context for future research.

  7. Kinematics in the Interacting, Star-Forming Galaxies NGC 3395/3396 and NGC 3991/3994/3995

    NASA Technical Reports Server (NTRS)

    Weistrop, Donna; Nelson, Charles H.

    1999-01-01

    It has been suggested that induced star formation is more sensitive to galaxy dynamics than to local phenomena and that enhanced star formation is found in galaxies with disturbed velocity structures. We are studying the stellar populations of several UV-bright, interacting galaxies to try to understand the detailed star formation process in these systems. We present preliminary results of an investigation of the kinematics of star-forming regions in the interacting systems NGC 3395/3396 and NGC 3991/3994/3995. Regions of powerful star formation are observed throughout these galaxies. The observatation will be used to investigate rotation curves in the galaxies and motion in the tidal tails.

  8. Experimenting with galaxies

    NASA Technical Reports Server (NTRS)

    Miller, Richard H.

    1992-01-01

    A study to demonstrate how the dynamics of galaxies may be investigated through the creation of galaxies within a computer model is presented. The numerical technique for simulating galaxies is shown to be both highly efficient and highly robust. Consideration is given to the anatomy of a galaxy, the gravitational N-body problem, numerical approaches to the N-body problem, use of the Poisson equation, and the symplectic integrator.

  9. Ultracompact Blue Dwarf Galaxies: Hubble Space Telescope Imaging and Stellar Population Analysis

    NASA Astrophysics Data System (ADS)

    Corbin, Michael R.; Vacca, William D.; Cid Fernandes, Roberto; Hibbard, John E.; Somerville, Rachel S.; Windhorst, Rogier A.

    2006-11-01

    We present deep Hubble Space Telescope (HST) Advanced Camera for Surveys/High Resolution Channel U-, narrow-V-, and I-band images of nine ``ultracompact'' blue dwarf galaxies (UCBDs) selected from the Sloan Digital Sky Survey (SDSS). We define UCBDs as local (z<0.01) star-forming galaxies having angular diameters less than 6" and physical diameters <1 kpc. They are also among the most metal-poor galaxies known, including objects having 12+log(O/H)<7.65, and are found to reside within voids. Both the HST images and the objects' SDSS optical spectra reveal that they are composites of young (~1-10 Myr) populations that dominate their light and older (~10 Gyr) populations that dominate their stellar masses, which we estimate to be ~107-108 Msolar. An intermediate-age (~107-109 yr) population is also indicated in most objects. The objects do not appear to be as dynamically disturbed as the prototype UCBD, POX 186, but the structure of several of them suggests that their current star formation has been triggered by the collisions/mergers of smaller clumps of stars. In one case, HS 0822+3542, the images resolve what may be two small (~100 pc) components that have recently collided, supporting this interpretation. In six of the objects much of the star formation is concentrated in young massive clusters, contributing to their compactness in ground-based images. The evidence that the galaxies consist mainly of ~10 Gyr old stars establishes that they are not protogalaxies, forming their first generation of stars. Their low metallicities are more likely to be the result of the escape of supernova ejecta, rather than youth.

  10. Dynamics of gas disks in triaxial galaxies

    SciTech Connect

    Steiman-Cameron, T.Y.

    1984-01-01

    Increasing evidence has accumulated since the mid 1970's arguing that many, if not all, undisturbed galaxies may have triaxial mass distributions. The steady state configurations (preferred planes) of gas disks in triaxial galaxies with static and rotating surface figures is determined. In addition, the evolution of a gas disk as it settles into the steady state is followed for both axisymmetric and triaxial galaxies. Observational tests are provided for triaxial galactic geometry and give more accurate measures of settling times than those previously published. The preferred planes for gas disks in static and tumbling triaxial galaxies are determined using an analytic method derived from celestial mechanics. The evolution of gas disks which are not in the steady state is followed using numerical methods.

  11. Is mankind unique in the Galaxy?

    NASA Astrophysics Data System (ADS)

    Martin, A. R.; Bond, A.

    1984-10-01

    There is a relation between questions regarding the uniqueness of mankind in the Galaxy and the 'Fermi Paradox'. It has appeared to Fermi that the eventual controlled command of astronomical quantities of energy, and the ability for mankind to head out into the universe was only a matter of time. On the other hand, he reasoned that a large number of sites for intelligence should have developed in the Galaxy a long time ago. He expected that such civilizations in colonizing the Galaxy would come in contact with the earth, and yet, there is no evidence regarding such contacts. Many aspects of the Fermi Paradox have been debated. The present investigation represents an attempt to further contribute to that debate by exploring some of the arguments prompted by the Paradox. It is concluded that all of the arguments have only one self-consistent resolution. According to this resolution, mankind is unique in the Galaxy.

  12. Galaxies: Interactions and Induced Star Formation

    NASA Astrophysics Data System (ADS)

    Kennicutt, R. C., Jr.; Schweizer, F.; Barnes, J. E.; Friedli, D.; Martinet, L.; Pfenniger, D.

    This volume contains the written version of the lectures given at the 26th course of the renowned Saas-Fee series. The book represents a comprehensive and up-to-date review of the field of galaxy interactions. Nowadays, galaxies are no longer seen as immutable objects: they evolve, interact, merge, blaze, and reshape. Dynamical forces can induce powerful stellar activity able to transform the matter composition and morphology of galaxies. With the aim at better understanding and explaining these remarkable and fascinating phenomena, three outstanding lecturers covered the following topics: ``Induced Star Formation" by Robert C. Kennicutt, ``Observational Evidence for Interactions and Mergers" by François Schweizer, and ``Dynamics of Galaxy Interactions" by Joshua E. Barnes. Though the book is intended for graduate students and young post-docs in astrophysics, it contains more advanced and original material, as well as historical perspectives which certainly will be of great interest also for experts and astronomy teachers.

  13. SCUBA Observations of High Redshift Radio Galaxies

    SciTech Connect

    Reuland, M; Rottgering, H; van Breugel, W

    2003-03-11

    High redshift radio galaxies (HzRGs) are key targets for studies of the formation and evolution of massive galaxies.The role of dust in these processes is uncertain. We have therefore observed the dust continuum emission from a sample of z > 3 radio galaxies with the SCUBA bolometer array. We confirm and strengthen the result found by Archibald et al. (1), that HzRGs are massive starforming systems and that submillimeter detection rate appears to be primarily a strong function of redshift. We also observed HzRG-candidates that have so far eluded spectroscopic redshift determination. Four of these have been detected, and provide evidence that they may be extremely obscured radio galaxies, possibly in an early stage of their evolution.

  14. The dwarf spheroidal galaxy Andromeda I

    SciTech Connect

    Mould, J.; Kristian, J. Mount Wilson and Las Campanas Observatories, Pasadena, CA )

    1990-05-01

    Images of Andromeda I in the visual and near-infrared show a giant branch characteristic of galactic globular clusters of intermediate metallicity. The distance of the galaxy is estimated from the tip of the giant branch to be 790 + or - 60 kpc. The physical dimensions and luminosity are similar to those of the dwarf spheroidal in Sculptor. There is no evidence for an intermediate age population in Andromeda I, and appropriate upper limits are specified. There is marginal evidence for a color gradient in the galaxy, a phenomenon not previously noted in a dwarf spheroidal. 21 refs.

  15. Galaxy Zoo: Observing secular evolution through bars

    SciTech Connect

    Cheung, Edmond; Faber, S. M.; Koo, David C.; Athanassoula, E.; Bosma, A.; Masters, Karen L.; Nichol, Robert C.; Melvin, Thomas; Bell, Eric F.; Lintott, Chris; Schawinski, Kevin; Skibba, Ramin A.; Willett, Kyle W.

    2013-12-20

    In this paper, we use the Galaxy Zoo 2 data set to study the behavior of bars in disk galaxies as a function of specific star formation rate (SSFR) and bulge prominence. Our sample consists of 13,295 disk galaxies, with an overall (strong) bar fraction of 23.6% ± 0.4%, of which 1154 barred galaxies also have bar length (BL) measurements. These samples are the largest ever used to study the role of bars in galaxy evolution. We find that the likelihood of a galaxy hosting a bar is anticorrelated with SSFR, regardless of stellar mass or bulge prominence. We find that the trends of bar likelihood and BL with bulge prominence are bimodal with SSFR. We interpret these observations using state-of-the-art simulations of bar evolution that include live halos and the effects of gas and star formation. We suggest our observed trends of bar likelihood with SSFR are driven by the gas fraction of the disks, a factor demonstrated to significantly retard both bar formation and evolution in models. We interpret the bimodal relationship between bulge prominence and bar properties as being due to the complicated effects of classical bulges and central mass concentrations on bar evolution and also to the growth of disky pseudobulges by bar evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

  16. Optical emission line nebulae in galaxy cluster cores 1: the morphological, kinematic and spectral properties of the sample

    NASA Astrophysics Data System (ADS)

    Hamer, S. L.; Edge, A. C.; Swinbank, A. M.; Wilman, R. J.; Combes, F.; Salomé, P.; Fabian, A. C.; Crawford, C. S.; Russell, H. R.; Hlavacek-Larrondo, J.; McNamara, B. R.; Bremer, M. N.

    2016-08-01

    We present an Integral Field Unit survey of 73 galaxy clusters and groups with the VIsible Multi Object Spectrograph on the Very Large Telescope. We exploit the data to determine the H α gas dynamics on kpc scales to study the feedback processes occurring within the dense cluster cores. We determine the kinematic state of the ionized gas and show that the majority of systems (˜2/3) have relatively ordered velocity fields on kpc scales that are similar to the kinematics of rotating discs and are decoupled from the stellar kinematics of the brightest cluster galaxy. The majority of the H α flux (>50 per cent) is typically associated with these ordered kinematics and most systems show relatively simple morphologies suggesting they have not been disturbed by a recent merger or interaction. Approximately 20 per cent of the sample (13/73) have disturbed morphologies which can typically be attributed to active galactic nuclei activity disrupting the gas. Only one system shows any evidence of an interaction with another cluster member. A spectral analysis of the gas suggests that the ionization of the gas within cluster cores is dominated by non-stellar processes, possibly originating from the intracluster medium itself.

  17. MAPPING THE EXTENDED H I DISTRIBUTION OF THREE DWARF GALAXIES

    SciTech Connect

    Hunter, Deidre A.; Zahedy, Fakhri; Bowsher, Emily C.; Wilcots, Eric M.; Kepley, Amanda A.; Gaal, Veronika E-mail: fsz@mit.edu E-mail: ewilcots@astro.wisc.edu

    2011-11-15

    We present large field H I-line emission maps obtained with the single-dish Green Bank Telescope centered on the dwarf irregular galaxies Sextans A, NGC 2366, and WLM. We do not detect the extended skirts of emission associated with the galaxies that were reported from Effelsberg observations. The ratio of H I at 10{sup 19} atoms cm{sup -2} to optical extents of these galaxies is instead 2-3, which is normal for this type of galaxy. There is no evidence for a truncation in the H I distribution {>=}10{sup 19} atoms cm{sup -2}.

  18. Galaxy Cluster Smashes Distance Record

    NASA Astrophysics Data System (ADS)

    2009-10-01

    he most distant galaxy cluster yet has been discovered by combining data from NASA's Chandra X-ray Observatory and optical and infrared telescopes. The cluster is located about 10.2 billion light years away, and is observed as it was when the Universe was only about a quarter of its present age. The galaxy cluster, known as JKCS041, beats the previous record holder by about a billion light years. Galaxy clusters are the largest gravitationally bound objects in the Universe. Finding such a large structure at this very early epoch can reveal important information about how the Universe evolved at this crucial stage. JKCS041 is found at the cusp of when scientists think galaxy clusters can exist in the early Universe based on how long it should take for them to assemble. Therefore, studying its characteristics - such as composition, mass, and temperature - will reveal more about how the Universe took shape. "This object is close to the distance limit expected for a galaxy cluster," said Stefano Andreon of the National Institute for Astrophysics (INAF) in Milan, Italy. "We don't think gravity can work fast enough to make galaxy clusters much earlier." Distant galaxy clusters are often detected first with optical and infrared observations that reveal their component galaxies dominated by old, red stars. JKCS041 was originally detected in 2006 in a survey from the United Kingdom Infrared Telescope (UKIRT). The distance to the cluster was then determined from optical and infrared observations from UKIRT, the Canada-France-Hawaii telescope in Hawaii and NASA's Spitzer Space Telescope. Infrared observations are important because the optical light from the galaxies at large distances is shifted into infrared wavelengths because of the expansion of the universe. The Chandra data were the final - but crucial - piece of evidence as they showed that JKCS041 was, indeed, a genuine galaxy cluster. The extended X-ray emission seen by Chandra shows that hot gas has been detected

  19. Low surface brightness galaxies

    NASA Technical Reports Server (NTRS)

    Vanderhulst, J. M.; Deblok, W. J. G.; Mcgaugh, S. S.; Bothun, G. D.

    1993-01-01

    A program to investigate the properties of low surface brightness (LSB) galaxies involving surface photometry in U, B, V, R, I, and H-alpha, HI imaging with the Westerbork Synthesis Radio Telescope (WSRT) and the very large array (VLA) and spectrophotometry of H2 regions in LSB galaxies is underway. The goal is to verify the idea that LSB galaxies have low star formation rates because the local gas density falls below the critical density for star formation, and to study the stellar population and abundances in LSB galaxies. Such information should help understanding the evolutionary history of LSB galaxies. Some preliminary results are reported.

  20. Evidence that the Severity of Depletion of Inorganic Phosphate Determines the Severity of the Disturbance of Adenine Nucleotide Metabolism in the Liver and Renal Cortex of the Fructose-Loaded Rat

    PubMed Central

    Morris, R. Curtis; Nigon, Kathleen; Reed, Elizabeth B.

    1978-01-01

    decrease in the rate at which ATP is regenerated. (b) The severity of depletion of Pi determines the severity of these disturbances. (c) By differentially mitigating the depletion of Pi, prior phosphate loading largely prevents these disturbances in the renal cortex, and attenuates them in the liver; and adenosine loading attenuates them only in the renal cortex. The findings provide some basis for the observation that in patients with hereditary fructose intolerance experimentally exposed to fructose, prior loading with sodium phosphate substantially attenuates the renal but not hepatic dysfunction. PMID:618911

  1. Galaxies as gravitational lenses.

    PubMed

    Sadeh, D

    1967-12-01

    The probability that a galaxy gathers light from another remote galaxy, and deflects and focuses it toward an observer on Earth, is calculated according to various cosmologic models. I pose the question of whether an object called a quasar is a single, intrinsically luminous entity or the result of accidental alignment, along the line of sight, of two normal galaxies, the more distant of which has its light amplified by the gravitational-lens effect of the nearer galaxy. If galaxies are distributed at random in the universe, the former alternative is true. But, if we assume that most galaxies exist in pairs, we can find about 30 galaxies occurring exactly one behind the other in such a way as to enable amplification of the order of 50. This model explains also the variations in intensity in quasars, but fails to explain others of their observed properties. PMID:17734305

  2. How Do Galaxies Grow?

    NASA Astrophysics Data System (ADS)

    2008-08-01

    Astronomers have caught multiple massive galaxies in the act of merging about 4 billion years ago. This discovery, made possible by combining the power of the best ground- and space-based telescopes, uniquely supports the favoured theory of how galaxies form. ESO PR Photo 24/08 ESO PR Photo 24/08 Merging Galaxies in Groups How do galaxies form? The most widely accepted answer to this fundamental question is the model of 'hierarchical formation', a step-wise process in which small galaxies merge to build larger ones. One can think of the galaxies forming in a similar way to how streams merge to form rivers, and how these rivers, in turn, merge to form an even larger river. This theoretical model predicts that massive galaxies grow through many merging events in their lifetime. But when did their cosmological growth spurts finish? When did the most massive galaxies get most of their mass? To answer these questions, astronomers study massive galaxies in clusters, the cosmological equivalent of cities filled with galaxies. "Whether the brightest galaxies in clusters grew substantially in the last few billion years is intensely debated. Our observations show that in this time, these galaxies have increased their mass by 50%," says Kim-Vy Tran from the University of Zürich, Switzerland, who led the research. The astronomers made use of a large ensemble of telescopes and instruments, including ESO's Very Large Telescope (VLT) and the Hubble Space Telescope, to study in great detail galaxies located 4 billion light-years away. These galaxies lie in an extraordinary system made of four galaxy groups that will assemble into a cluster. In particular, the team took images with VIMOS and spectra with FORS2, both instruments on the VLT. From these and other observations, the astronomers could identify a total of 198 galaxies belonging to these four groups. The brightest galaxies in each group contain between 100 and 1000 billion of stars, a property that makes them comparable

  3. The role of galaxy interaction in the SFR-M {sub *} relation: characterizing morphological properties of Herschel-selected galaxies at 0.2 < z < 1.5

    SciTech Connect

    Hung, Chao-Ling; Sanders, D. B.; Casey, C. M.; Lee, N.; Barnes, J. E.; Koss, M.; Larson, K. L.; Lockhart, K.; Man, A. W. S.; Mann, A. W.; Capak, P.; Kartaltepe, J. S.; Le Floc'h, E.; Riguccini, L.; Scoville, N.; Symeonidis, M.

    2013-12-01

    Galaxy interactions/mergers have been shown to dominate the population of IR-luminous galaxies (L {sub IR} ≳ 10{sup 11.6} L {sub ☉}) in the local universe (z ≲ 0.25). Recent studies based on the relation between galaxies' star formation rates and stellar mass (the SFR-M {sub *} relation or the {sup g}alaxy main sequence{sup )} have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy main sequence. Since the typical SFR at a given M {sub *} increases with redshift, the existence of the galaxy main sequence implies that massive, IR-luminous galaxies at high z may not necessarily be driven by galaxy interactions. We examine the role of galaxy interactions in the SFR-M {sub *} relation by carrying out a morphological analysis of 2084 Herschel-selected galaxies at 0.2 < z < 1.5 in the COSMOS field. Using a detailed visual classification scheme, we show that the fraction of 'disk galaxies' decreases and the fraction of 'irregular' galaxies increases systematically with increasing L {sub IR} out to z ≲ 1.5 and z ≲ 1.0, respectively. At L {sub IR} >10{sup 11.5} L {sub ☉}, ≳ 50% of the objects show evident features of strongly interacting/merger systems, where this percentage is similar to the studies of local IR-luminous galaxies. The fraction of interacting/merger systems also systematically increases with the deviation from the SFR-M {sub *} relation, supporting the view that galaxies falling above the main sequence are more dominated by mergers than the main-sequence galaxies. Meanwhile, we find that ≳ 18% of massive IR-luminous 'main-sequence galaxies' are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model.

  4. Are sleep disturbances preclinical markers of Parkinson's disease?

    PubMed

    dos Santos, Altair B; Kohlmeier, Kristi A; Barreto, George E

    2015-03-01

    Parkinson's disease (PD) is a neurobehavioral disorder characterized by motor symptoms and signs, and non-motor abnormalities such as olfactory dysfunction, pain, sleep disorders and cognitive impairment. Amongst these alterations, sleep disturbances play an important role in the pathology, but presence of disturbed sleep is not currently considered in diagnosis. However, sleeping problems may precede by many years the classic motor abnormalities of PD and should be clinically evaluated as a potential marker before disease onset. The first disturbance reported with this potential was the disorder REM sleep behaviour and currently several other disturbances have gained importance as potential markers, such as excessive daytime sleepiness, restless legs syndrome and new evidence also points to changes in circadian rhythms. Here we present a brief review of the major evidence indicating that sleep disturbances precede the motor symptoms in PD and neurodegeneration occurs in regions that could underlie these phenomena in order to provide support for the conclusion that disturbances of sleep should be considered as valuable preclinical markers for PD.

  5. Discovery of a bright quasar without a massive host galaxy.

    PubMed

    Magain, Pierre; Letawe, Géraldine; Courbin, Frédéric; Jablonka, Pascale; Jahnke, Knud; Meylan, Georges; Wisotzki, Lutz

    2005-09-15

    A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy. Because the optical luminosity of quasars exceeds that of their host galaxy, disentangling the two components can be difficult. This led in the 1990s to the controversial claim of the discovery of 'naked' quasars. Since then, the connection between quasars and galaxies has been well established. Here we report the discovery of a quasar lying at the edge of a gas cloud, whose size is comparable to that of a small galaxy, but whose spectrum shows no evidence for stars. The gas in the cloud is excited by the quasar itself. If a host galaxy is present, it is at least six times fainter than would normally be expected for such a bright quasar. The quasar is interacting dynamically with a neighbouring galaxy, whose gas might be feeding the black hole.

  6. The Evolution of Cuspy Triaxial Galaxies Harboring Central Black Holes

    NASA Astrophysics Data System (ADS)

    Holley-Bockelmann, Kelly; Mihos, J. Christopher; Sigurdsson, Steinn; Hernquist, Lars; Norman, Colin

    2002-03-01

    We use numerical simulations to study the evolution of triaxial elliptical galaxies with central black holes. In contrast to earlier studies which used galaxy models with central density ``cores,'' our galaxies have steep central cusps, as observed in real ellipticals. As a black hole grows in these cuspy triaxial galaxies, the inner regions become rounder owing to chaos induced in the orbital families that populate the model. At larger radii, however, the models maintain their triaxiality, and orbital analyses show that centrophilic orbits there resist stochasticity over many dynamical times. While black hole-induced evolution is strong in the inner regions of these galaxies and reaches out beyond the nominal ``sphere of influence'' of a black hole, our simulations do not show evidence for a rapid global transformation of the host. The triaxiality of observed elliptical galaxies is therefore not inconsistent with the presence of supermassive black holes at their centers.

  7. PROBING THE INTERGALACTIC MEDIUM-GALAXY CONNECTION AT z < 0.5. I. A GALAXY SURVEY IN QSO FIELDS AND A GALAXY-ABSORBER CROSS-CORRELATION STUDY ,

    SciTech Connect

    Chen, H.-W.; Mulchaey, John S. E-mail: mulchaey@ociw.edu

    2009-08-20

    We present an imaging and spectroscopic survey of galaxies in fields around QSOs HE 0226-4110, PKS 0405-123, and PG 1216+069. The fields are selected to have ultraviolet echelle spectra available, which uncover 195 Ly{alpha} absorbers and 13 O{sub VI} absorbers along the three sightlines. We obtain robust redshifts for 1104 galaxies of rest-frame absolute magnitude M{sub R} - 5log h {approx}< -16 and at projected physical distances {rho} {approx}< 4 h{sup -1} Mpc from the QSOs. Hubble Space Telescope (HST)/WFPC2 images of the fields around PKS 0405-123 and PG 1216+069 are available for studying the optical morphologies of absorbing galaxies. Combining the absorber and galaxy data, we perform a cross-correlation study to understand the physical origin of Ly{alpha} and O{sub VI} absorbers and to constrain the properties of extended gas around galaxies. The results of our study are: (1) both strong Ly{alpha} absorbers of N(H{sub I}){>=}14 and O{sub VI} absorbers exhibit a comparable clustering amplitude as emission-line-dominated galaxies and a factor of {approx} 6 weaker amplitude than absorption-line-dominated galaxies on comoving projected distance scales of r{sub p} < 3 h{sup -1} Mpc; (2) weak Ly{alpha} absorbers of N(H{sub I})<13.5 appear to cluster very weakly around galaxies; (3) none of the absorption-line-dominated galaxies at r{sub p} {<=} 250 h{sup -1} kpc has a corresponding O{sub VI} absorber to a sensitive upper limit of W(1031) {approx}< 0.03 A, while the covering fraction of O{sub VI} absorbing gas around emission-line-dominated galaxies is found to be {kappa} {approx} 64%; and (4) high-resolution images of five O{sub VI} absorbing galaxies show that these galaxies exhibit disk-like morphologies with mildly disturbed features on the edge. Together, the data indicate that O{sub VI} absorbers arise preferentially in gas-rich galaxies. In addition, tidal debris in groups/galaxy pairs may be principally responsible for the observed O{sub VI} absorbers

  8. Star formation in quasar and active galaxy environments

    NASA Astrophysics Data System (ADS)

    Coldwell, Georgina V.; Lambas, Diego G.

    2003-09-01

    We use the 2dF public 100 K data release of galaxies and samples of quasars and active galaxies taken from the Véron-Cetty and Véron catalogue to study the nature of galaxies in the surroundings of active objects with redshifts in the range 0.1 < z < 0.2. We explore the distribution of neighbour 2dF galaxy spectral types, η, at different projected distances from the quasars and active galaxies with radial velocity difference ΔV= 500 km s-1. For comparison, we perform a similar analysis on the environment of typical galaxies in the 2dF catalogue, a sample of bright early-type galaxies, i.e. η < -1.4 and MbJ < -21, and also on a sample of 2dF galaxy groups. We find a higher relative fraction of emission-line galaxies, i.e. with 2dF spectral type indices η >3.5, in the vicinity of quasars and active galaxies compared to that in the neighbourhood of typical galaxies, bright early types and groups. This effect extends up to projected distance rp~ 1 h-1 Mpc for active galaxies and rp~ 3 h-1 Mpc for quasars. We also find a tendency for companion galaxies of quasars to be brighter than the neighbours of active galaxies within rp~ 3 h-1 Mpc. We estimate average star-formation rates for objects at different distances from quasars, active galaxies, galaxies and groups. We find a significantly higher star-formation activity within ~2.0 h-1 Mpc from quasars with respect to typical galaxies, which reinforces the idea that star formation is enhanced in the neighbourhood of quasars. Our tests with the group environment provide evidence against quasars being associated with groups. Also, our analysis of the neighbours of bright early types shows that although these galaxies are typical hosts of quasars, their companion galaxies are significantly different in terms of the star-formation activity.

  9. Sources of UV Flux in Early-Type Galaxies

    NASA Astrophysics Data System (ADS)

    Burstein, David

    In a paper in press (Burstein at al. 1988), we show that the level of far-UV flux (relative to optical flux) in 24 'normal' early-type galaxies is strongly correlated with their metallicity. The UV spectra of 4 'active' early-type galaxies show both similarities and differences compared to those of normal galaxies of similar overall UV flux, while the UV spectra of 'starforming' galaxies show clear evidence of ongoing star formation. However, the physical source(s) of UV flux in active and normal galaxies cannot yet be unambiguously identified for two reasons: a) similarity of UV energy distributions of hot stellar populations and b) missing and low SIN LW spectra of key active and mildly star-forming galaxies (e.g. N4486=M87; the hot stellar population contributes 50% of the flux at 2660 A). We propose here to obtain high SIN LWP spectra to better define the differences (and similarities) of the strong UV component among normal, active and star-forming galaxies. Four representative galaxies have been chosen for study: N4486, N1052, N4742 and N4111. Our analysis of these data should serve both to better define the mean temperatures of the main sequence turnoffs in these galaxies, as well as the presence (or absence) of special features in the spectral energy distributions, such as excess emission between 2000 -2500 A in active galaxies (the so-called 'blue bump').

  10. THE ORIENTATION OF GALAXIES IN GALAXY CLUSTERS

    SciTech Connect

    Godlowski, Wlodzimierz; Piwowarska, Paulina; Panko, Elena; Flin, Piotr E-mail: paoletta@interia.p E-mail: sfflin@cyf-kr.edu.p

    2010-11-10

    We present an analysis of the spatial orientations of galaxies in 247 optically selected rich Abell clusters which have at least 100 members in the considered area. We investigated the relation between angles that give information about galaxy angular momenta and the number of members in each structure. The position angles of the galaxies' major axes, as well as two angles describing the spatial orientation of the galaxy plane, were tested for isotropy by applying three different statistical tests. It is found that the values of the statistics increase with the amount of the galaxies' members, which is equivalent to the existence of a relation between anisotropy and the number of galaxies in a cluster. The search for connection between the galaxies' alignments and Bautz-Morgan (BM) morphological types of examined clusters showed a weak dependence. A statistically marginal relation between velocity dispersion and cluster richness was observed. In addition, it was found that the velocity dispersion decreases with BM type at almost 3{sigma} level. These results show the dependence of alignments with respect to clusters' richness, which can be regarded as an environmental effect.

  11. Using Galaxy Winds to Constrain Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Churchill, Christopher W.; Klypin, A.; Ceverino, D.; Kacprzak, G.; Klimek, E.

    2010-01-01

    Analysis of mock quasar spectra of metal absorption lines in the proximity of formed galaxies in cosmological simulation is a highly promising for understanding the role of galaxies in IGM physics, or IGM physics in the role of galaxy formation in context of the cosmic web. Such analysis using neutral hydrogen in the cosmic web has literally revolutionized our understanding of the Lyman alpha forest. We are undertaking a wholesale approach to use powerful Lambda-CDM simulations to interpret absorption line data from redshift 1-3 starbursting galaxies e.g. Lyman break galaxies, etc) The data with which direct quantitative comparison is made are from the DEEP survey (Weiner et al.) and the collective work of Steidel et al. and collaborators. The simulations are performed using the Eulerian Gasdynamics plus N-body Adaptive Refinement Tree (ART) code, which has gas cell resolutions of 20-50 pc. Physical processes implemented in the code include realistic radiative cooling, star formation, metal enrichment and thermal feedback due to type II and type Ia supernovae. We quantitatively compare the spatial and kinematic distribution of HI, MgII, CIV, and OVI of absorption lines over a range of impact parameters for various simulated galaxies as a function of redshift, and discuss key insights for interpreting the underlying temperature, density, and ionization structure of the halo/cosmic-web interface, and the influence of galaxies on its chemical enrichment.

  12. The Hα Galaxy survey. V. The star formation history of late-type galaxies

    NASA Astrophysics Data System (ADS)

    James, P. A.; Prescott, M.; Baldry, I. K.

    2008-06-01

    Aims: This study of 117 low-redshift Im and Sm galaxies investigates the star formation rates of late-type galaxies, to determine whether they are quasi-continuous or dominated by bursts with quiescent interludes. Methods: We analyse the distribution of star formation timescales (stellar masses/star formation rates) for the entire sample, and of gas depletion timescales for those galaxies with gas mass measurements. Results: We find that, on average, the late-type galaxies studied could have produced their total stellar masses by an extrapolation of their current star formation activity over a period of just under a Hubble time. This is not the case for a comparison sample of earlier-type galaxies, even those with disk-dominated morphologies and similar total stellar masses to the late-type galaxies. The earlier-type galaxies are on average forming their stars more slowly at present than the average rate over their past histories. No totally quiescent Im or Sm galaxies are found, and although some evidence of intrinsic variation in the star formation rate with time is found, this is typically less than a factor of 2 increase or decrease relative to the mean level. The Im and Sm galaxies have extensive gas reservoirs and can maintain star formation at the current rate for more than another Hubble time. The average spatial distribution of star formation in the Im galaxies, and to a lesser extent the Sm galaxies, is very similar to that of the older stellar population traced by the red light. Conclusions: Late type, bulge-free galaxies have a predominantly continuous mode of star formation, and could have assembled their stellar masses through continued star formation over a Hubble time with the currently-observed rate and spatial distribution. There is little evidence in this sample of predominantly isolated field galaxies of significant star formation through brief but intense starburst phases. Based on observations made with the Jacobus Kapteyn Telescope operated

  13. Landscape Disturbance History and Belowground Carbon Dynamics.

    NASA Astrophysics Data System (ADS)

    Marin-Spiotta, E.; Smith, A. P.; Atkinson, E. E.; Chaopricha, N. T.

    2014-12-01

    Earth system models vary in their predictions of carbon (C) uptake and release by the terrestrial biosphere, partly due to great uncertainties in the response of soils, one of the largest C reservoirs. The world's soils play a major role in the exchange of greenhouse gases with the atmosphere, in sustaining primary production, and in providing food security. Despite this, the sensitivity of soils to disturbance is highly uncertain. One reason for this is geographic variability in the importance of different mechanisms regulating soil C turnover. Most of our understanding of factors influencing soil organic C dynamics comes from research in temperate soils, despite the major role of tropical soils in the global C cycle. Even in the tropics, the diversity of soil environments is grossly underrepresented in the literature. This has important implications for predictions of soil C change across latitudes. We discuss results from the response of soil C pools and microbial communities to land use legacies on two contrasting tropical soil environments. Uncertainties in the response of soil C to disturbance also stem from a historic focus on shallow depths and the assumption that deep soil C is unreactive to landscape change. Growing evidence indicates that soil C pools in deep mineral horizons can be sensitive to changes in land cover and climate. This realization highlights the need to reassess the source of soil C at depth and the processes contributing to its stabilization. We discuss results from the interaction between multiple disturbances: drought, fire and erosion, on the accumulation of soil C at depths beyond those typically included in regional or global inventories. Our data show that deep soil C can be reactive and be a potential source of C if reconnected to the atmosphere. A deeper, mechanistic appreciation for a landscape's history of disturbance is critical for predicting feedbacks between the terrestrial biosphere and the climate system.

  14. High-resolution spectra of distant compact narrow emission line galaxies: Progrenitors of spheroidal galaxies

    NASA Technical Reports Server (NTRS)

    Koo, David C.; Guzman, Rafael; Faber, S. M.; Illingworth, Garth D.; Bershady, Matthew A.; Kron, Richard G.; Takamiya, Marianne

    1995-01-01

    Emission-line velocity widths have been determined for 17 faint (B approximately 20-23) very blue, compact galaxies whose redshifts range from z = 0.095 to 0.66. The spectra have a resolution of 8 Km/s and were taken with the HIRES echelle spectrograph of the Keck 10 m telescope. The galaxies are luminous with all but two within 1 mag of M(sub B) approximately -21. Yet they exhibit narrow velocity widths between sigma = 28-157 km/s, more consistent with typical values of extreme star-forming galaxies than with those of nearby spiral galaxies of similar luminosity. In particular, objects with sigma is less than or equal to 65 km/s follow the same correlations between sigma and both blue and H beta luminosities as those of nearby H II galaxies. These results strengthen the identification of H II glaxies as thier local counterparts. The blue colors and strong emission lines suggest these compact galaxies are undergoing a recent, strong burst of star formation. Like those which characterize some H II galaxies, this burst could be a nuclear star-forming event within a much larger, older stellar population. If the burst is instead a major episode in the total star-forming history, these distant galaxies could fade enough to match the low luminosities and surface brightnesses typical of nearby spheroidals like NGC 185 or NGC 205. Together with evidence for recent star formation, exponential light profiles, and subsolar metallicities, the postfading correlations between luminosity and velocity width and bewtween luminosity and surface brightness suggest that among the low-sigma galaxies, we may be witnessing, in situ, the progenitors of today's spheroidal galaxies.

  15. Stellar halos around Local Group galaxies

    NASA Astrophysics Data System (ADS)

    McConnachie, Alan W.

    2016-08-01

    The Local Group is now home to 102 known galaxies and candidates, with many new faint galaxies continuing to be discovered. The total stellar mass range spanned by this population covers a factor of close to a billion, from the faintest systems with stellar masses of order a few thousand to the Milky Way and Andromeda, with stellar masses of order 1011 M ⊙. Here, I discuss the evidence for stellar halos surrounding Local Group galaxies spanning from dwarf scales (with the case of the Andromeda II dwarf spheroidal), though to intermediate mass systems (M33) and finishing with M31. Evidence of extended stellar populations and merging is seen across the luminosity function, indicating that the processes that lead to halo formation are common at all mass scales.

  16. Massive Quiescent Disk Galaxies in the CANDELS survey

    NASA Astrophysics Data System (ADS)

    Kesseli, Aurora; McGrath, E. J.; CANDELS Collaboration

    2014-01-01

    Using data from the GOODS-S field of the CANDELS survey, we find evidence for an increasing fraction of disk-dominated galaxies at high-redshift ( 2) among the quiescent, or non-star-forming galaxy population, in agreement with a growing body of evidence from recent results in the literature. We selected all galaxies with mass M>1010 Msun within the redshift range 0.5 ≤ z ≤ 2.5, and imposed a two-color selection criteria using rest-frame U, V, and J-band flux to separate quiescent from star-forming galaxies. From this sample, we performed a qualitative visual classification and a quantitative classification using the galaxy-fitting program Galfit. Of the original 140 quiescent galaxies, 23 have a disk component that contributes 50% or more of the total integrated galaxy light, and most of these are at high-redshift. At a redshift of z ~ 2 a significant fraction of all quiescent galaxies showed strong disk components with 30% being disk-dominated. We also find that massive disk galaxies seem to live in less densely populated environments while massive ellipticals live in environments with more neighbors, which leads us to believe that there are two mechanisms for the creation of massive quiescent galaxies. For the disks, the lower density environment and the disk nature of these galaxies lead us to favor cold streams over the major merger model of galaxy formation. The ellipticals, which live in higher density environments, could be assembled through major mergers of already aged stellar populations (e.g., dry mergers). This research is supported by the Clare Boothe Luce Foundation.

  17. Revealing the nature of star forming blue early-type galaxies at low redshift

    NASA Astrophysics Data System (ADS)

    George, Koshy; Zingade, Kshama

    2015-11-01

    Context. Star forming early-type galaxies with blue optical colours at low redshift can be used to test our current understanding of galaxy formation and evolution. Aims: We want to reveal the fuel and triggering mechanism for star formation in these otherwise passively evolving red and dead stellar systems. Methods: We undertook an optical and ultraviolet study of 55 star forming blue early-type galaxies, searching for signatures of recent interactions that could be driving the molecular gas into the galaxy and potentially triggering the star formation. Results: We report here our results on star forming blue early-type galaxies with tidal trails and in close proximity to neighbouring galaxies that are evidence of ongoing or recent interactions between galaxies. There are 12 galaxies with close companions with similar redshifts, among which two galaxies are having ongoing interactions that potentially trigger the star formation. Two galaxies show a jet feature that could be due to the complete tidal disruption of the companion galaxy. The interacting galaxies have high star formation rates and very blue optical colours. Galaxies with no companion could have undergone a minor merger in the recent past. Conclusions: The recent or ongoing interaction with a gas-rich neighbouring galaxy could be responsible for bringing cold gas to an otherwise passively evolving early-type galaxy. The sudden gas supply could trigger the star formation, eventually creating a blue early-type galaxy. The galaxies with ongoing tidal interaction are blue and star forming, thereby implying that blue early-type galaxies can exist even when the companion is on flyby so does not end up in a merger. Based on data compiled from Galaxy Zoo project, and the volunteers contribution are acknowledged at http://www.galaxyzoo.org/Volunteers.aspx

  18. The Cosmic Dance of Distant Galaxies

    NASA Astrophysics Data System (ADS)

    2006-03-01

    detail, since they had to select a single slit, i.e. a single direction, across the galaxy. Things changed with the availability of the multi-object GIRAFFE spectrograph [2], now installed on the 8.2-m Kueyen Unit Telescope of ESO's Very Large Telescope (VLT) at the Paranal Observatory (Chile). In one mode, known as "3-D spectroscopy" or "integral field", this instrument can obtain simultaneous spectra of smaller areas of extended objects like galaxies or nebulae. For this, 15 deployable fibre bundles, the so-called Integral Field Units (IFUs) , cf. ESO PR 01/02 , are used to make meticulous measurements of distant galaxies. Each IFU is a microscopic, state-of-the-art two-dimensional lens array with an aperture of 3 x 2 arcsec2 on the sky. It is like an insect's eye, with twenty micro-lenses coupled with optical fibres leading the light recorded at each point in the field to the entry slit of the spectrograph. ESO PR Photo 10c/06 ESO PR Photo 10c/06 Dark Matter and Stellar Mass in Distant Galaxies "GIRAFFE on ESO's VLT is the only instrument in the world that is able to analyze simultaneously the light coming from 15 galaxies covering a field of view almost as large as the full moon," said Mathieu Puech, lead author of one the papers presenting the results [3]. "Every galaxy observed in this mode is split into continuous smaller areas where spectra are obtained at the same time." The astronomers used GIRAFFE to measure the velocity fields of several tens of distant galaxies, leading to the surprising discovery that as much as 40% of distant galaxies were "out of balance" - their internal motions were very disturbed - a possible sign that they are still showing the aftermath of collisions between galaxies. When they limited themselves to only those galaxies that have apparently reached their equilibrium, the scientists found that the relation between the dark matter and the stellar content did not appear to have evolved during the last 6 billions years. Thanks to its

  19. Disturbance and diversity at two spatial scales.

    PubMed

    Limberger, Romana; Wickham, Stephen A

    2012-03-01

    The spatial scale of disturbance is a factor potentially influencing the relationship between disturbance and diversity. There has been discussion on whether disturbances that affect local communities and create a mosaic of patches in different successional stages have the same effect on diversity as regional disturbances that affect the whole landscape. In a microcosm experiment with metacommunities of aquatic protists, we compared the effect of local and regional disturbances on the disturbance-diversity relationship. Local disturbances destroyed entire local communities of the metacommunity and required reimmigration from neighboring communities, while regional disturbances affected the whole metacommunity but left part of each local community intact. Both disturbance types led to a negative relationship between disturbance intensity and Shannon diversity. With strong local disturbance, this decrease in diversity was due to species loss, while strong regional disturbance had no effect on species richness but reduced the evenness of the community. Growth rate appeared to be the most important trait for survival after strong local disturbance and dominance after strong regional disturbance. The pattern of the disturbance-diversity relationship was similar for both local and regional diversity. Although local disturbances at least temporally increased beta diversity by creating a mosaic of differently disturbed patches, this high dissimilarity did not result in regional diversity being increased relative to local diversity. The disturbance-diversity relationship was negative for both scales of diversity. The flat competitive hierarchy and absence of a trade-off between competition and colonization ability are a likely explanation for this pattern.

  20. ONLY THE LONELY: H I IMAGING OF VOID GALAXIES

    SciTech Connect

    Kreckel, K.; Van Gorkom, J. H.; Platen, E.; Van de Weygaert, R.; Van der Hulst, J. M.; Aragon-Calvo, M. A.; Yip, C.-W.; Kovac, K.; Peebles, P. J. E.

    2011-01-15

    Void galaxies, residing within the deepest underdensities of the Cosmic Web, present an ideal population for the study of galaxy formation and evolution in an environment undisturbed by the complex processes modifying galaxies in clusters and groups, as well as provide an observational test for theories of cosmological structure formation. We have completed a pilot survey for the H I imaging aspects of a new Void Galaxy Survey (VGS), imaging 15 void galaxies in H I in local (d < 100 Mpc) voids. H I masses range from 3.5 x 10{sup 8} to 3.8 x 10{sup 9} M{sub sun}, with one nondetection with an upper limit of 2.1 x 10{sup 8} M{sub sun}. Our galaxies were selected using a structural and geometric technique to produce a sample that is purely environmentally selected and uniformly represents the void galaxy population. In addition, we use a powerful new backend of the Westerbork Synthesis Radio Telescope that allows us to probe a large volume around each targeted galaxy, simultaneously providing an environmentally constrained sample of fore- and background control samples of galaxies while still resolving individual galaxy kinematics and detecting faint companions in H I. This small sample makes up a surprisingly interesting collection of perturbed and interacting galaxies, all with small stellar disks. Four galaxies have significantly perturbed H I disks, five have previously unidentified companions at distances ranging from 50 to 200 kpc, two are in interacting systems, and one was found to have a polar H I disk. Our initial findings suggest void galaxies are a gas-rich, dynamic population which present evidence of ongoing gas accretion, major and minor interactions, and filamentary alignment despite the surrounding underdense environment.

  1. Galaxy NGC 247

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the dwarf spiral galaxy NGC 247 was taken by Galaxy Evolution Explorer on October 13, 2003, in a single orbit exposure of 1600 seconds. The region that looks like a 'hole' in the upper part of the galaxy is a location with a deficit of gas and therefore a lower star formation rate and ultraviolet brightness. Optical images of this galaxy show a bright star on the southern edge. This star is faint and red in the Galaxy Evolution Explorer ultraviolet image, revealing that it is a foreground star in our Milky Way galaxy. The string of background galaxies to the North-East (upper left) of NGC 247 is 355 million light years from our Milky Way galaxy whereas NGC 247 is a mere 9 million light years away. The faint blue light that can be seen in the Galaxy Evolution Explorer image of the upper two of these background galaxies may indicate that they are in the process of merging together.

  2. Morphology and Dynamics in the Inner Regions of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Jong, Jelte Teun Anne de

    2005-09-01

    It is a well established fact that the universe contains much more matter than we can observe directly from their emission or absorption properties. All massive objects in the universe move with respect to each other under the influence of their mutual gravitational attraction. This enables us to determine the mass of gravitationally bound systems by looking at their dynamics. From the motions of galaxies within galaxy clusters, we know that these clusters contain at least ten times more mass than we can see in the form of galaxies and intergalactic gas. The rotation of spiral galaxies shows that galaxies themselves are also much more massive than can be explained by the stars and gas that we observe. Modern astronomy faces the disturbing fact that we cannot see and do not understand the nature of at least 90 percent of the matter content of the universe. In this thesis we focus on one possible constituent of this unseen, ``dark''or ``missing'' matter, namely dark, massive, compact objects that might be present in the halos of galaxies. Using the gravitational lensing effect we search for these otherwise impossible to observe objects within the halo of the cosmic neighbour of our Milky Way, the Andromeda galaxy.

  3. The Dynamical Equilibrium of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Carlberg, R. G.; Yee, H. K. C.; Ellingson, E.; Morris, S. L.; Abraham, R.; Gravel, P.; Pritchet, C. J.; Smecker-Hane, T.; Hartwick, F. D. A.; Hesser, J. E.; Hutchings, J. B.; Oke, J. B.

    1997-02-01

    If a galaxy cluster is effectively in dynamical equilibrium, then all galaxy populations within the cluster must have distributions in velocity and position that individually reflect the same underlying mass distribution, although the derived virial masses can be quite different. Specifically, within the Canadian Network for Observational Cosmology cluster sample, the virial radius of the red galaxy population is, on the average, a factor of 2.05 +/- 0.34 smaller than that of the blue population. The red galaxies also have a smaller rms velocity dispersion, a factor of 1.31 +/- 0.13 within our sample. Consequently, the virial mass calculated from the blue galaxies is 3.5 +/- 1.3 times larger than from the red galaxies. However, applying the Jeans equation of stellar hydrodynamic equilibrium to the red and blue subsamples separately gives statistically identical cluster mass profiles. This is strong evidence that these clusters are effectively equilibrium systems and therefore demonstrates empirically that the masses in the virialized region are reliably estimated using dynamical techniques.

  4. The baryonic mass function of galaxies.

    PubMed

    Read, J I; Trentham, Neil

    2005-12-15

    In the Big Bang about 5% of the mass that was created was in the form of normal baryonic matter (neutrons and protons). Of this about 10% ended up in galaxies in the form of stars or of gas (that can be in molecules, can be atomic, or can be ionized). In this work, we measure the baryonic mass function of galaxies, which describes how the baryonic mass is distributed within galaxies of different types (e.g. spiral or elliptical) and of different sizes. This can provide useful constraints on our current cosmology, convolved with our understanding of how galaxies form. This work relies on various large astronomical surveys, e.g. the optical Sloan Digital Sky Survey (to observe stars) and the HIPASS radio survey (to observe atomic gas). We then perform an integral over our mass function to determine the cosmological density of baryons in galaxies: Omega(b,gal)=0.0035. Most of these baryons are in stars: Omega(*)=0.0028. Only about 20% are in gas. The error on the quantities, as determined from the range obtained between different methods, is ca 10%; systematic errors may be much larger. Most (ca 90%) of the baryons in the Universe are not in galaxies. They probably exist in a warm/hot intergalactic medium. Searching for direct observational evidence and deeper theoretical understanding for this will form one of the major challenges for astronomy in the next decade. PMID:16286285

  5. The Cosmic Dance of Distant Galaxies

    NASA Astrophysics Data System (ADS)

    2006-03-01

    detail, since they had to select a single slit, i.e. a single direction, across the galaxy. Things changed with the availability of the multi-object GIRAFFE spectrograph [2], now installed on the 8.2-m Kueyen Unit Telescope of ESO's Very Large Telescope (VLT) at the Paranal Observatory (Chile). In one mode, known as "3-D spectroscopy" or "integral field", this instrument can obtain simultaneous spectra of smaller areas of extended objects like galaxies or nebulae. For this, 15 deployable fibre bundles, the so-called Integral Field Units (IFUs) , cf. ESO PR 01/02 , are used to make meticulous measurements of distant galaxies. Each IFU is a microscopic, state-of-the-art two-dimensional lens array with an aperture of 3 x 2 arcsec2 on the sky. It is like an insect's eye, with twenty micro-lenses coupled with optical fibres leading the light recorded at each point in the field to the entry slit of the spectrograph. ESO PR Photo 10c/06 ESO PR Photo 10c/06 Dark Matter and Stellar Mass in Distant Galaxies "GIRAFFE on ESO's VLT is the only instrument in the world that is able to analyze simultaneously the light coming from 15 galaxies covering a field of view almost as large as the full moon," said Mathieu Puech, lead author of one the papers presenting the results [3]. "Every galaxy observed in this mode is split into continuous smaller areas where spectra are obtained at the same time." The astronomers used GIRAFFE to measure the velocity fields of several tens of distant galaxies, leading to the surprising discovery that as much as 40% of distant galaxies were "out of balance" - their internal motions were very disturbed - a possible sign that they are still showing the aftermath of collisions between galaxies. When they limited themselves to only those galaxies that have apparently reached their equilibrium, the scientists found that the relation between the dark matter and the stellar content did not appear to have evolved during the last 6 billions years. Thanks to its

  6. Nucleosynthesis in the Magellanic Clouds and the Galaxy.

    NASA Technical Reports Server (NTRS)

    Burbidge, G.

    1971-01-01

    Available evidence on the chemical composition of the Magellanic Clouds (when compared to the Galaxy) is not sufficient for a detailed theory of the chemical evolution of the Clouds to be developed at present. However, this evidence is thus far compatible with the view that much of the material of the Clouds went through a considerable amount of nucleosynthesis early in its history. The Clouds could once have been part of the Galaxy, or they could have formed as satellites when the protogalaxy condensed. The general problem of the chemical evolution is tied closely to the problem of galaxy formation which remains unsolved.

  7. TEMPORAL SELF-ORGANIZATION IN GALAXY FORMATION

    SciTech Connect

    Cen, Renyue

    2014-04-20

    We report on the discovery of a relation between the number of star formation (SF) peaks per unit time, ν{sub peak}, and the size of the temporal smoothing window function, Δt, used to define the peaks: ν{sub peak}∝Δt {sup 1} {sup –} {sup φ} (φ ∼ 1.618). This relation holds over the range of Δt = 10-1000 Myr that can be reliably computed here, using a large sample of galaxies obtained from a state-of-the-art cosmological hydrodynamic simulation. This means that the temporal distribution of SF peaks in galaxies as a population is fractal with a Hausdorff fractal dimension equal to φ – 1. This finding reveals, for the first time, that the superficially chaotic process of galaxy formation is underlined by temporal self-organization up to at least one gigayear. It is tempting to suggest that, given the known existence of spatial fractals (such as the power-law two-point function of galaxies), there is a joint spatio-temporal self-organization in galaxy formation. From an observational perspective, it will be urgent to devise diagnostics to probe the SF histories of galaxies with good temporal resolution to facilitate a test of this prediction. If confirmed, it would provide unambiguous evidence for a new picture of galaxy formation that is interaction driven, cooperative, and coherent in and between time and space. Unravelling its origin may hold the key to understanding galaxy formation.

  8. On the Nature of Hydrostatic Equilibrium in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Biffi, V.; Borgani, S.; Murante, G.; Rasia, E.; Planelles, S.; Granato, G. L.; Ragone-Figueroa, C.; Beck, A. M.; Gaspari, M.; Dolag, K.

    2016-08-01

    In this paper, we investigate the level of hydrostatic equilibrium (HE) in the intracluster medium of simulated galaxy clusters, extracted from state-of-the-art cosmological hydrodynamical simulations performed with the Smoothed-Particle-Hydrodynamic code GADGET-3. These simulations include several physical processes, among which are stellar and active galactic nucleus feedback, and have been performed with an improved version of the code that allows for a better description of hydrodynamical instabilities and gas mixing processes. Evaluating the radial balance between the gravitational and hydrodynamical forces via the gas accelerations generated, we effectively examine the level of HE in every object of the sample and its dependence on the radial distance from the center and on the classification of the cluster in terms of either cool-coreness or dynamical state. We find an average deviation of 10%–20% out to the virial radius, with no evident distinction between cool-core and non-cool-core clusters. Instead, we observe a clear separation between regular and disturbed systems, with a more significant deviation from HE for the disturbed objects. The investigation of the bias between the hydrostatic estimate and the total gravitating mass indicates that, on average, this traces the deviation from HE very well, even though individual cases show a more complex picture. Typically, in the radial ranges where mass bias and deviation from HE are substantially different, the gas is characterized by a significant amount of random motions (≳ 30 % ), relative to thermal ones. As a general result, the HE-deviation and mass bias, at a given distance from the cluster center, are not very sensitive to the temperature inhomogeneities in the gas.

  9. On the Nature of Hydrostatic Equilibrium in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Biffi, V.; Borgani, S.; Murante, G.; Rasia, E.; Planelles, S.; Granato, G. L.; Ragone-Figueroa, C.; Beck, A. M.; Gaspari, M.; Dolag, K.

    2016-08-01

    In this paper, we investigate the level of hydrostatic equilibrium (HE) in the intracluster medium of simulated galaxy clusters, extracted from state-of-the-art cosmological hydrodynamical simulations performed with the Smoothed-Particle-Hydrodynamic code GADGET-3. These simulations include several physical processes, among which are stellar and active galactic nucleus feedback, and have been performed with an improved version of the code that allows for a better description of hydrodynamical instabilities and gas mixing processes. Evaluating the radial balance between the gravitational and hydrodynamical forces via the gas accelerations generated, we effectively examine the level of HE in every object of the sample and its dependence on the radial distance from the center and on the classification of the cluster in terms of either cool-coreness or dynamical state. We find an average deviation of 10%-20% out to the virial radius, with no evident distinction between cool-core and non-cool-core clusters. Instead, we observe a clear separation between regular and disturbed systems, with a more significant deviation from HE for the disturbed objects. The investigation of the bias between the hydrostatic estimate and the total gravitating mass indicates that, on average, this traces the deviation from HE very well, even though individual cases show a more complex picture. Typically, in the radial ranges where mass bias and deviation from HE are substantially different, the gas is characterized by a significant amount of random motions (≳ 30 % ), relative to thermal ones. As a general result, the HE-deviation and mass bias, at a given distance from the cluster center, are not very sensitive to the temperature inhomogeneities in the gas.

  10. Deep infrared galaxies

    NASA Technical Reports Server (NTRS)

    Ashby, Matthew; Houck, J. R.; Hacking, Perry B.

    1992-01-01

    High signal-to-noise ratio optical spectra of 17 infrared-bright emission-line galaxies near the north ecliptic pole are presented. Reddening-corrected line ratios forbidden O III 5007/H-beta, N II 6583/H-alpha, S II (6716 + 6731)/H-alpha, and O I 6300/H-alpha are used to discriminate between candidate energy generation mechanisms in each galaxy. These criteria have frequently been applied to optically selected samples of galaxies in the past, but this is the first time they have been applied to a set of faint flux-limited infrared-selected objects. The analysis indicates the sample contains seven starburst galaxies and three (AGN). However, seven galaxies in the present sample elude the classification scheme based on these line ratios. It is concluded that a two-component (starburst plus AGN) model for energy generation is inadequate for infrared galaxies.

  11. Classic Galaxy with Glamour

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This color composite image of nearby NGC 300 combines the visible-light pictures from Carnegie Institution of Washington's 100-inch telescope at Las Campanas Observatory (colored red and yellow), with ultraviolet views from NASA's Galaxy Evolution Explorer. Galaxy Evolution Explorer detectors image far ultraviolet light (colored blue).

    This composite image traces star formation in progress. Young hot blue stars dominate the outer spiral arms of the galaxy, while the older stars congregate in the nuclear regions which appear yellow-green. Gases heated by hot young stars and shocks due to winds from massive stars and supernova explosions appear in pink, as revealed by the visible-light image of the galaxy.

    Located nearly 7 million light years away, NGC 300 is a member of a nearby group of galaxies known as the Sculptor Group. It is a spiral galaxy like our own Milky Way.

  12. Tidal Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Duc, P.-A.; Mirabel, I. F.; Brinks, E.

    The life and evolution of galaxies are dramatically affected by environmental effects. Interactions with the intergalactic medium and collisions with companions cause major perturbations in the morphology and contents of galaxies: in particular stars and gas clouds may be gravitationally pulled out from their parent galaxies during tidal encounters, forming rings, tails and bridges. This debris of collisions lies at the origin of a new generation of small galaxies, the so-called "tidal dwarf galaxies" (TDGs). The authors have carried out multi-wavelength observations of some 20 TDGs. These systems are made of two stellar components: young stars, formed from the recent collapse of expelled H I clouds, and an older stellar population, tidally pulled out from the disks of their interacting parent galaxies. In the observed TDGs, the current star formation episode is fuelled by a large reservoir of H I gas and is younger than 10 Myr.

  13. The Unexpected Past of a Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    1996-08-01

    in this way effectively `eats' the smaller one. Thus the Milky Way may contain the remains of many smaller galaxies it has met and consumed in the past. A natural consequence of this theory is that the Milky Way halo may at least partially consist of stars which originally belonged to these smaller galaxies. However, it is also possible that some of the halo stars formed during the early collapse of the gas cloud from which the Milky Way formed. Like the Milky Way, the two nearest, large spiral galaxies (the Andromeda nebula and M33 in the neighbouring Triangulum constellation) are also surrounded by halos of old stars. Contrarily, investigations of the smaller galaxies in the Local Group have until now not shown that they possess such halos. These dwarf galaxies greatly outnumber the large spiral galaxies - to date about two dozen are known - and they are considered to be the last survivors of the earlier cannibalism phase. The nearest are the well-known Magellanic Clouds, about 170,000 (Large Cloud) and 250,000 light years distant (Small Cloud). They can be seen with the unaided eye from the Southern hemisphere. Recent studies indicate that they orbit the Milky Way and that they may eventually fall prey to our galaxy in a future round of cannibalism. So far, no evidence has been found of an old halo around the Magellanic Clouds. This does not necessarily imply that all dwarf galaxies must likewise lack halos: it is also possible that the halos of the Magellanic Clouds were stripped away when they came too close to the Milky Way sometime in the past. The isolated WLM dwarf galaxy Down in the southern sky, in the constellation of Cetus (the Whale or the Sea Monster), lies a relative faint and distant, small galaxy which astronomers normally refer to as the WLM dwarf galaxy . It was first seen in 1909 by the famous astrophotographer Max Wolf on photographic plates obtained at the Heidelberg Observatory (Germany), but it was only in 1926 that its true nature was

  14. Finding the First Galaxies

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2009-01-01

    Astronomers study distant galaxies by taking long exposures in deep survey fields. They choose fields that are empty of known sources, so that they are statistically representative of the Universe as a whole. Astronomers can compare the distribution of the detected galaxies in brightness, color, morphology and redshift to theoretical models, in order to puzzle out the processes of galaxy evolution. In 2004, the Hubble Space Telescope was pointed at a small, deep-survey field in the southern constellation Fornax for more than 500 hours of exposure time. The resulting Hubble Ultra-Deep Field could see the faintest and most distant galaxies that the telescope is capable of viewing. These galaxies emitted their light less than 1 billion years after the Big Bang. From the Ultra Deep Field and other galaxy surveys, astronomers have built up a history of star formation in the universe. the peak occurred about7 billion years ago, about half of the age of the current universe, then the number of stars that were forming was about 15 time the rate today. Going backward in time to when the very first starts and galaxies formed, the average star-formation rate should drop to zero. but when looking at the most distant galaxies in the Ultra Deep field, the star formation rate is still higher than it is today. The faintest galaxies seen by Hubble are not the first galaxies that formed in the early universe. To detect these galaxies NASA is planning the James Webb Space Telescope for launch in 2013. Webb will have a 6.5-meter diameter primary mirror, much bigger than Hubble's 2.4-meter primary, and will be optimized for infrared observations to see the highly redshifted galaxies.

  15. Amazing Andromeda Galaxy

    NASA Technical Reports Server (NTRS)

    2006-01-01

    The many 'personalities' of our great galactic neighbor, the Andromeda galaxy, are exposed in this new composite image from NASA's Galaxy Evolution Explorer and the Spitzer Space Telescope.

    The wide, ultraviolet eyes of Galaxy Evolution Explorer reveal Andromeda's 'fiery' nature -- hotter regions brimming with young and old stars. In contrast, Spitzer's super-sensitive infrared eyes show Andromeda's relatively 'cool' side, which includes embryonic stars hidden in their dusty cocoons.

    Galaxy Evolution Explorer detected young, hot, high-mass stars, which are represented in blue, while populations of relatively older stars are shown as green dots. The bright yellow spot at the galaxy's center depicts a particularly dense population of old stars.

    Swaths of red in the galaxy's disk indicate areas where Spitzer found cool, dusty regions where stars are forming. These stars are still shrouded by the cosmic clouds of dust and gas that collapsed to form them.

    Together, Galaxy Evolution Explorer and Spitzer complete the picture of Andromeda's swirling spiral arms. Hints of pinkish purple depict regions where the galaxy's populations of hot, high-mass stars and cooler, dust-enshrouded stars co-exist.

    Located 2.5 million light-years away, the Andromeda is our largest nearby galactic neighbor. The galaxy's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, our Milky Way galaxy's disk is about 100,000 light-years across.

    This image is a false color composite comprised of data from Galaxy Evolution Explorer's far-ultraviolet detector (blue), near-ultraviolet detector (green), and Spitzer's multiband imaging photometer at 24 microns (red).

  16. Galaxy evolution. Galactic paleontology.

    PubMed

    Tolstoy, Eline

    2011-07-01

    Individual low-mass stars have very long lives, comparable to the age of the universe, and can thus be used to probe ancient star formation. At present, such stars can be identified and studied only in the Milky Way and in the very closest of our neighboring galaxies, which are predominantly small dwarf galaxies. These nearby ancient stars are a fossil record that can provide detailed information about the physical processes that dominated the epoch of galaxy formation and subsequent evolution.

  17. Disturbance and California riparian tree establishment

    NASA Astrophysics Data System (ADS)

    Bendix, J.; Cowell, C. M.

    2010-12-01

    As is the case in many ecosystems, tree establishment in riparian corridors is often episodic, following disturbance events that clear colonization sites. In many riparian settings, flooding is the most obvious, and relevant disturbance agent. However, in Mediterranean-climate regions, fire is an equally important disturbance agent. In California, the frequency and severity of both floods and fire are expected to change with projected climate change, making an understanding of their roles key to understanding future ecological processes in California riparian environments. In this paper, we use tree-ring data from the Transverse Ranges of Southern California to explore the relative importance of fire and flood in the establishment of riparian gallery forest. We examined 42 cores of Alnus rhombifolia, Populus fremontii and Quercus agrifolia from the riparian zone adjacent to Piedra Blanca and Potrero John Creeks in California’s Transverse Ranges, and compared their establishment dates with records of fire and floods, to see how establishment related to disturbance history. Our results show some evidence for major fire having an impact, as all of the largest stems dated to the few years following the 1932 Matilija fire, which had burned all of the sites in our sample. The remainder of the record is less straightforward, although there is an establishment peak in the 1970s, which may be related to a 1975 fire that burned part of the Potrero John watershed. Of note, the establishment chronology shows no relationship to the flood record, as years of major floods do not relate to either prolific or sparse years in the tree-ring record. This record suggests that large fires may serve as a trigger for tree establishment in California riparian settings, but that they are hardly a prerequisite, as many stems germinated between fires. Indeed, ongoing regeneration is apparently independent of disturbance, given the apparent irrelevance of flooding in this regard. The result

  18. Record-breaking ancient galaxy clusters

    NASA Astrophysics Data System (ADS)

    2003-12-01

    , called RDCS1252.9-2927, is as massive as ‘300 trillion’ suns and is the most massive known cluster for its epoch. The image reveals the core of the cluster and is part of a much larger mosaic of the entire cluster. Dominating the core are a pair of large, reddish elliptical galaxies [near centre of image]. Their red colour indicates an older population of stars. Most of the stars are at least 1 000 million years old. The two galaxies appear to be interacting and may eventually merge to form a larger galaxy that is comparable to the brightest galaxies seen in present-day clusters. The red galaxies surrounding the central pair are also cluster members. The cluster probably contains many thousands of galaxies, but only about 50 can be seen in this image. The full mosaic reveals several hundred cluster members. Many of the other galaxies in the image, including several of the blue galaxies, are foreground or background galaxies. The colour-composite image was assembled from two observations (through i and z filters) taken between May and June 2002 by the ACS Wide Field Camera, and one image with the ISAAC instrument on the VLT taken in 2002 (combined from a J filter exposure and a K filter exposure). Looking back in time nearly 9000 million years, an international team of astronomers found mature galaxies in a young Universe. The galaxies are members of a cluster of galaxies that existed when the Universe was only 5000 million years old, or about 35 percent of its present age. This is compelling evidence that galaxies must have started forming just after the Big Bang and is bolstered by observations made by the same team of astronomers when they peered even farther back in time. The team found embryonic galaxies a mere 1500 million years after the birth of the cosmos, or 10 percent of the Universe's present age. The ‘baby galaxies’ reside in a still developing cluster, the most distant proto-cluster ever found. The Advanced Camera for Surveys (ACS) aboard the NASA

  19. The AMIGA sample of isolated galaxies. X. A first look at isolated galaxy colors

    NASA Astrophysics Data System (ADS)

    Fernández Lorenzo, M.; Sulentic, J.; Verdes-Montenegro, L.; Ruiz, J. E.; Sabater, J.; Sánchez, S.

    2012-04-01

    Context. The basic properties of galaxies can be affected by both nature (internal processes) or nurture (interactions and effects of environment). Deconvolving the two effects is an important current effort in astrophysics. Observed properties of a sample of isolated galaxies should be mainly the result of internal (natural) evolution. It follows that nurture-induced galaxy evolution can only be understood through a comparative study of galaxies in different environments. Aims: We take a first look at SDSS (g - r) colors of galaxies in the AMIGA sample, which consists of many of the most isolated galaxies in the local Universe. This alerted us at the same time to the pitfalls of using automated SDSS colors. Methods: We focused on median values for the principal morphological subtypes found in the AMIGA sample (E/S0 and Sb-Sc) and compared them with equivalent measures obtained for galaxies in denser environments. Results: We find a weak tendency for AMIGA spiral galaxies to be redder than objects in close pairs. We find no clear difference when we compared this with galaxies in other (e.g. group) environments. However, the (g - r) color of isolated galaxies shows a Gaussian distribution, as might be expected assuming nurture-free evolution. We find a smaller median absolute deviation in colors for isolated galaxies compared to both wide and close pairs. The majority of the deviation on median colors for spiral subtypes is caused by a color-luminosity correlation. Surprisingly, isolated and non-isolated early-type galaxies show similar (g - r). We see little evidence for a green valley in our sample because most spirals redder than (g - r) = 0.7 have spurious colors. Conclusions: The redder colors of AMIGA spirals and lower color dispersions for AMIGA subtypes - compared with close pairs - are likely caused by a more passive star formation in very isolated galaxies. Full Tables 1 and 2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130

  20. Use of Videotape Feedback with Severely Disturbed Adolescents.

    ERIC Educational Resources Information Center

    Michel, Jane; Blitstein, Sheldon

    1979-01-01

    Summarizes the design and effects of a group therapy project using videotape feedback with seriously disturbed adolescents. Offers anecdotal evidence that the feedback facilitated the correction of the participants' distorted body images, low self-esteem, lack of capacity for self-observation, and poor peer relationships. (SS)

  1. Serious Emotional Disturbance in Children and Adolescents: Multisystemic Therapy.

    ERIC Educational Resources Information Center

    Henggeler, Scott W.; Schoenwald, Sonja K.; Rowland, Melisa D.; Cunningham, Phillippe B.

    Originally developed to treat antisocial behavior, multisystemic therapy (MST) has emerged as a leading evidence-based treatment for serious emotional disturbance in children and adolescents. This manual presents the MST approach to working with this challenging population. Delineated are ways to develop and implement collaborative interventions…

  2. Brainstem Auditory Evoked Response in Children with Central Language Disturbance.

    ERIC Educational Resources Information Center

    Piggott, Leonard R.; Anderson, Theodora

    1983-01-01

    Two groups of 10 children between the ages of 94 and 165 months were paired for age (wthin 6 months) and sex and were compared for Brainstem Auditory Evoked Response patterns. One child in each pair showed evidence of central language disturbance as determined by neuropsychological testing. The other did not. All had normal hearing and IQs of 80…

  3. Childhood Abuse, Body Image Disturbance, and Eating Disorders.

    ERIC Educational Resources Information Center

    Schaaf, Kristin K.; McCanne, Thomas R.

    1994-01-01

    This study examined the relationships among childhood sexual and physical abuse, body image disturbance, and eating disorder symptomatology in college students, of whom 29 had been sexually abused, 32 physically abused, and 29 nonabused. There was no evidence that child sexual or physical abuse was associated with the development of body image…

  4. Galaxy UGC10445

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This ultraviolet color image of the galaxy UGC10445 was taken by NASA's Galaxy Evolution Explorer on June 7 and June 14, 2003. UGC10445 is a spiral galaxy located 40 million light-years from Earth.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  5. Galaxy NGC5962

    NASA Technical Reports Server (NTRS)

    2003-01-01

    NASA's Galaxy Evolution Explorer took this ultraviolet color image of the galaxy NGC5962 on June 7, 2003. This spiral galaxy is located 90 million light-years from Earth.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  6. Extremely Isolated Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Fuse, Christopher R.; Marcum, P.; Fanelli, M.; Aars, C.

    2006-06-01

    Isolated galaxies provide a means of assessing the evolution of galactic systems. Extremely isolated galaxies define a zero-interaction baseline for comparative studies of galaxy evolution. We present results of a search for isolated elliptical galaxies (IEGs). We utilize the optical imaging data produced by the Sloan Digital Sky Survey (SDSS) to identify candidate galaxies from Release 1-4 of the SDSS. Candidate IEGs meet strict isolation criteria: Any IEG must be separated by at least 2.5 Mpc from any neighboring non-dwarf galaxy having a MV fainter than -16.5 mag. The candidate isolated systems have no non-dwarf neighbors within a distance such that we can insure that the IEGs have never interacted with another existing galaxy since formation.In order to increase the signal-to-noise ratio, we have used the SDSS images in the u,g,r filters to create combined sets of images for each IEG. The stacked images permit a more robust determination of the morphology of the candidate galaxies. Verification that these are spheroidal systems is achieved through a bulge/disk decomposition technique using standard surface photometry. Our preliminary sample of 51 isolated systems defines a complete volume-limited population of extremely isolated early-type galaxies within a distance of 72Mpc

  7. Managing Sleep Disturbances in Cirrhosis

    PubMed Central

    Zhao, Xun

    2016-01-01

    Sleep disturbances, particularly daytime sleepiness and insomnia, are common problems reported by patients suffering from liver cirrhosis. Poor sleep negatively impacts patients' quality of life and cognitive functions and increases mortality. Although sleep disturbances can be an early sign of hepatic encephalopathy (HE), many patients without HE still complain of poor quality sleep. The pathophysiology of these disturbances is not fully understood but is believed to be linked to impaired hepatic melatonin metabolism. This paper provides an overview for the clinician of common comorbidities contributing to poor sleep in patients with liver disease, mainly restless leg syndrome and obstructive sleep apnea. It discusses nondrug and pharmacologic treatment options in these patients, such as the use of light therapy and histamine (H1) blockers. PMID:27242950

  8. Gas in void galaxies

    NASA Astrophysics Data System (ADS)

    Kreckel, Kathryn Joyce

    Void galaxies, residing within the deepest underdensities of the Cosmic Web, present an ideal population for the study of galaxy formation and evolution in an environment undisturbed by the complex processes modifying galaxies in clusters and groups, and provide an observational test for theories of cosmological structure formation. We investigate the neutral hydrogen properties (i.e. content, morphology, kinematics) of void galaxies, both individually and systematically, using a combination of observations and simulations, to form a more complete understanding of the nature of these systems. We investigate in detail the H I morphology and kinematics of two void galaxies. One is an isolated polar disk galaxy in a diffuse cosmological wall situated between two voids. The considerable gas mass and apparent lack of stars in the polar disk, coupled with the general underdensity of the environment, supports recent theories of cold flow accretion as an alternate formation mechanism for polar disk galaxies. We also examine KK 246, the only confirmed galaxy located within the nearby Tully Void. It is a dwarf galaxy with an extremely extended H I disk and signs of an H I cloud with anomalous velocity. It also exhibits clear misalignment between the kinematical major and minor axes, and a general misalignment between the H I and optical major axes. The relative isolation and extreme underdense environment make these both very interesting cases for examining the role of gas accretion in galaxy evolution. To study void galaxies as a population, we have carefully selected a sample of 60 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS. We have imaged this new Void Galaxy Survey in H I at the Westerbork Synthesis Radio Telescope with a typical resolution of 8 kpc, probing a volume of 1.2 Mpc and 12,000 km s^-1 surrounding each galaxy. We reach H I mass limits of 2 x 10^8 M_sun and column density sensitivities of 5 x 10^19 cm^-2

  9. Cold Fronts in Clusters of Galaxies: Observations and Modeling

    NASA Technical Reports Server (NTRS)

    Markevitch, Maxim

    2012-01-01

    Mergers of galaxy clusters -- some of the most energetic events in the Universe -- produce disturbances in hot intracluster medium, such as shocks and cold fronts, that can be used as tools to study the physics of galaxy clusters. Cold fronts may constrain viscosity and the structure and strength of the cluster magnetic fields. Combined with radio data, these observations also shed light on the production of ultrarelativistic particles that are known to coexist with the cluster thermal plasma. This talk will summarize the current X-ray observations of cluster mergers, as well as some recent radio data and high resolution hydrodynamic simulations.

  10. On the distribution of galaxy ellipticity in clusters

    NASA Astrophysics Data System (ADS)

    D'Eugenio, F.; Houghton, R. C. W.; Davies, R. L.; Dalla Bontà, E.

    2015-07-01

    We study the distribution of projected ellipticity n(ɛ) for galaxies in a sample of 20 rich (Richness ≥ 2) nearby (z < 0.1) clusters of galaxies. We find no evidence of differences in n(ɛ), although the nearest cluster in the sample (the Coma Cluster) is the largest outlier (P(same) < 0.05). We then study n(ɛ) within the clusters, and find that ɛ increases with projected cluster-centric radius R (hereafter the ɛ-R relation). This trend is preserved at fixed magnitude, showing that this relation exists over and above the trend of more luminous galaxies to be both rounder and more common in the centres of clusters. The ɛ-R relation is particularly strong in the subsample of intrinsically flattened galaxies (ɛ > 0.4), therefore it is not a consequence of the increasing fraction of round slow rotator galaxies near cluster centers. Furthermore, the ɛ-R relation persists for just smooth flattened galaxies and for galaxies with de Vaucouleurs-like light profiles, suggesting that the variation of the spiral fraction with radius is not the underlying cause of the trend. We interpret our findings in light of the classification of early type galaxies (ETGs) as fast and slow rotators. We conclude that the observed trend of decreasing ɛ towards the centres of clusters is evidence for physical effects in clusters causing fast rotator ETGs to have a lower average intrinsic ellipticity near the centres of rich clusters.

  11. Deficiency of ''Thin'' Stellar Bars in Seyfert Host Galaxies

    NASA Technical Reports Server (NTRS)

    Shlosman, Isaac; Peletier, Reynier F.; Knapen, Johan

    1999-01-01

    Using all available major samples of Seyfert galaxies and their corresponding control samples of closely matched non-active galaxies, we find that the bar ellipticities (or axial ratios) in Seyfert galaxies are systematically different from those in non-active galaxies. Overall, there is a deficiency of bars with large ellipticities (i.e., 'fat' or 'weak' bars) in Seyferts, compared to non-active galaxies. Accompanied with a large dispersion due to small number statistics, this effect is strictly speaking at the 2 sigma level. To obtain this result, the active galaxy samples of near-infrared surface photometry were matched to those of normal galaxies in type, host galaxy ellipticity, absolute magnitude, and, to some extent, in redshift. We discuss possible theoretical explanations of this phenomenon within the framework of galactic evolution, and, in particular, of radial gas redistribution in barred galaxies. Our conclusions provide further evidence that Seyfert hosts differ systematically from their non-active counterparts on scales of a few kpc.

  12. The Disturbing Student and the Judicial Process

    ERIC Educational Resources Information Center

    Ragle, John D.; Paine, Gage E.

    2009-01-01

    The Assessment-Intervention of Student Problems (AISP) model is a useful tool for preparing student affairs professionals to assess the problems of disturbed, disturbing, or disturbed/disturbing students and to make appropriate referrals. It is particularly useful because it emphasizes the necessity of developing an integrated system for this…

  13. The SAMI Galaxy Survey: Spatially resolving the environmental quenching of star formation in GAMA galaxies

    NASA Astrophysics Data System (ADS)

    Schaefer, A. L.; Croom, S. M.; Allen, J. T.; Brough, S.; Medling, A. M.; Ho, I.-T.; Scott, N.; Richards, S. N.; Pracy, M. B.; Gunawardhana, M. L. P.; Norberg, P.; Alpaslan, M.; Bauer, A. E.; Bekki, K.; Bland-Hawthorn, J.; Bloom, J. V.; Bryant, J. J.; Couch, W. J.; Driver, S. P.; Fogarty, L. M. R.; Foster, C.; Goldstein, G.; Green, A. W.; Hopkins, A. M.; Konstantopoulos, I. S.; Lawrence, J. S.; López-Sánchez, A. R.; Lorente, N. P. F.; Owers, M. S.; Sharp, R.; Sweet, S. M.; Taylor, E. N.; van de Sande, J.; Walcher, C. J.; Wong, O. I.

    2016-09-01

    We use data from the Sydney-AAO Multi-Object Integral Field Spectrograph (SAMI) Galaxy Survey and the Galaxy And Mass Assembly (GAMA) survey to investigate the spatially-resolved signatures of the environmental quenching of star formation in galaxies. Using dust-corrected measurements of the distribution of Hα emission we measure the radial profiles of star formation in a sample of 201 star-forming galaxies covering three orders of magnitude in stellar mass ({M}_{*}; 108.1-1010.95 M⊙) and in 5th nearest neighbour local environment density (Σ5; 10-1.3- 102.1 Mpc-2). We show that star formation rate gradients in galaxies are steeper in dense (log10(Σ5/Mpc2) > 0.5) environments by 0.58 ± 0.29 dex re-1 in galaxies with stellar masses in the range 1010 < M★/M⊙ < 1011 and that this steepening is accompanied by a reduction in the integrated star formation rate. However, for any given stellar mass or environment density the star-formation morphology of galaxies shows large scatter. We also measure the degree to which the star formation is centrally concentrated using the unitless scale-radius ratio (r50, Hα/r50, cont), which compares the extent of ongoing star formation to previous star formation. With this metric we find that the fraction of galaxies with centrally concentrated star formation increases with environment density, from ˜5 ± 4% in low-density environments (log10(Σ5/Mpc2) < 0.0) to 30 ± 15% in the highest density environments (log10(Σ5/Mpc2) > 1.0). These lines of evidence strongly suggest that with increasing local environment density the star formation in galaxies is suppressed, and that this starts in their outskirts such that quenching occurs in an outside-in fashion in dense environments and is not instantaneous.

  14. The Void Galaxy Survey: Galaxy Evolution and Gas Accretion in Voids

    NASA Astrophysics Data System (ADS)

    Kreckel, Kathryn; van Gorkom, Jacqueline H.; Beygu, Burcu; van de Weygaert, Rien; van der Hulst, J. M.; Aragon-Calvo, Miguel A.; Peletier, Reynier F.

    2016-10-01

    Voids represent a unique environment for the study of galaxy evolution, as the lower density environment is expected to result in shorter merger histories and slower evolution of galaxies. This provides an ideal opportunity to test theories of galaxy formation and evolution. Imaging of the neutral hydrogen, central in both driving and regulating star formation, directly traces the gas reservoir and can reveal interactions and signs of cold gas accretion. For a new Void Galaxy Survey (VGS), we have carefully selected a sample of 59 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS at distances of ~100 Mpc, and pursued deep UV, optical, Hα, IR, and HI imaging to study in detail the morphology and kinematics of both the stellar and gaseous components. This sample allows us to not only examine the global statistical properties of void galaxies, but also to explore the details of the dynamical properties. We present an overview of the VGS, and highlight key results on the HI content and individually interesting systems. In general, we find that the void galaxies are gas rich, low luminosity, blue disk galaxies, with optical and HI properties that are not unusual for their luminosity and morphology. We see evidence of both ongoing assembly, through the gas dynamics between interacting systems, and significant gas accretion, seen in extended gas disks and kinematic misalignments. The VGS establishes a local reference sample to be used in future HI surveys (CHILES, DINGO, LADUMA) that will directly observe the HI evolution of void galaxies over cosmic time.

  15. The Dragonfly nearby Galaxies Survey. I. Substantial Variation in the Diffuse Stellar Halos around Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Merritt, Allison; van Dokkum, Pieter; Abraham, Roberto; Zhang, Jielai

    2016-10-01

    Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep ({μ }g\\gt 31 mag arcsec‑2) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. Our sample includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of 16-19 degrees and distances between 7-18 Mpc. We construct stellar mass surface density profiles from the observed g-band surface brightness in combination with the g ‑ r color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk+bulge fit) beyond 5 half-mass radii. We find a mean halo fraction of 0.009 ± 0.005 and a large rms scatter of {1.01}-0.26+0.9 dex. The peak-to-peak scatter of the halo fraction is a factor of \\gt 100—while some galaxies feature strongly structured halos resembling that of M31, three of the eight have halos that are completely undetected in our data. We conclude that spiral galaxies as a class exhibit a rich variety in stellar halo properties, implying that their assembly histories have been highly non-uniform. We find no convincing evidence for an environmental or stellar mass dependence of the halo fraction in the sample.

  16. GIANT GALAXIES, DWARFS, AND DEBRIS SURVEY. I. DWARF GALAXIES AND TIDAL FEATURES AROUND NGC 7331

    SciTech Connect

    Ludwig, Johannes; Pasquali, Anna; Grebel, Eva K.; Gallagher, John S. III

    2012-12-01

    The Giant GAlaxies, Dwarfs, and Debris Survey (GGADDS) concentrates on the nearby universe to study how galaxies have interacted in groups of different morphology, density, and richness. In these groups, we select the dominant spiral galaxy and search its surroundings for dwarf galaxies and tidal interactions. This paper presents the first results from deep wide-field imaging of NGC 7331, where we detect only four low-luminosity candidate dwarf companions and a stellar stream that may be evidence of a past tidal interaction. The dwarf galaxy candidates have surface brightnesses of {mu}{sub r} Almost-Equal-To 23-25 mag arcsec{sup -2} with (g - r){sub 0} colors of 0.57-0.75 mag in the Sloan Digital Sky Survey filter system, consistent with their being dwarf spheroidal (dSph) galaxies. A faint stellar stream structure on the western edge of NGC 7331 has {mu}{sub g} Almost-Equal-To 27 mag arcsec{sup -2} and a relatively blue color of (g - r){sub 0} = 0.15 mag. If it is tidal debris, then this stream could have formed from a rare type of interaction between NGC 7331 and a dwarf irregular or transition-type dwarf galaxy. We compare the structure and local environments of NGC 7331 to those of other nearby giant spirals in small galaxy groups. NGC 7331 has a much lower ({approx}2%) stellar mass in the form of early-type satellites than found for M31 and lacks the presence of nearby companions like luminous dwarf elliptical galaxies or the Magellanic Clouds. However, our detection of a few dSph candidates suggests that it is not deficient in low-luminosity satellites.

  17. Merger signatures in the galaxy cluster A98

    SciTech Connect

    Paterno-Mahler, R.; Blanton, E. L.; Randall, S. W.; Bulbul, E.; Andrade-Santos, F.; Jones, C.; Murray, S.; Johnson, R. E. E-mail: eblanton@bu.edu E-mail: ebulbul@head.cfa.harvard.edu E-mail: cjones@cfa.harvard.edu E-mail: rjohnson@gettysburg.edu

    2014-08-20

    We present results from Chandra and XMM-Newton observations of Abell 98 (A98), a galaxy cluster with three major components: a relatively bright subcluster to the north (A98N), a disturbed subcluster to the south (A98S), and a fainter subcluster to the far south (A98SS). We find evidence for surface brightness and temperature asymmetries in A98N consistent with a shock-heated region to the south, which could be created by an early stage merger between A98N and A98S. Deeper observations are required to confirm this result. We also find that A98S has an asymmetric core temperature structure, likely due to a separate ongoing merger. Evidence for this is also seen in optical data. A98S hosts a wide-angle tail radio source powered by a central active galactic nucleus (AGN). We find evidence for a cavity in the intracluster medium that has been evacuated by one of the radio lobes, suggesting that AGN feedback is operating in this system. Examples of cavities in non-cool core clusters are relatively rare. The three subclusters lie along a line in projection, suggesting the presence of a large-scale filament. We observe emission along the filament between A98N and A98S, and a surface brightness profile shows emission consistent with the overlap of the subcluster extended gas halos. We find the temperature of this region is consistent with the temperature of the gas at similar radii outside this bridge region. Lastly, we examine the cluster dynamics using optical data. We conclude A98N and A98S are likely bound to one another with a 67% probability, while A98S and A98SS are not bound at a high level of significance.

  18. Statistical analysis of ALFALFA galaxies: Insights in galaxy formation & near-field cosmology

    NASA Astrophysics Data System (ADS)

    Papastergis, Emmanouil

    2013-03-01

    Sky Survey (SDSS), to measure the number density of galaxies as a function of their "baryonic" mass (stars + atomic gas). In the context of a ΛCDM cosmological model, the measured distribution reveals that low-mass halos are heavily "baryon depleted", i.e. their baryonic-to-dark mass ratio is much lower than the cosmological value. These baryon deficits are usually attributed to stellar feedback (e.g. supernova-driven gas outflows), but the efficiency implied by our measurement is extremely high. Whether such efficient feedback can be accommodated in a consistent picture of galaxy formation is an open question, and remains one of the principle scientific drivers for hydrodynamic simulations of galaxy formation. Lastly, we measure the clustering properties of HI-selected samples, through the two-point correlation function of ALFALFA galaxies. We find no compelling evidence for a dependence of clustering on HI mass, suggesting that the relationship between galactic gas mass and host halo mass is not tight. We furthermore find that HI galaxies cluster more weakly than optically selected ones, when no color selection is applied. However, SDSS galaxies with blue colors have very similar clustering characteristics with ALFALFA galaxies, both in real as well as in redshift space. On the other hand, HI galaxies cluster much more weakly than optical galaxies with red colors, and in fact "avoid" being located within ≈3 Mpc from the latter. By considering the clustering properties of ΛCDM halos, we confirm our previous intuition for an MHI-Mh relation with large scatter, and find that spin parameter may be a key halo property related to the gas content of present-day galaxies.

  19. The Gas Distribution in Galaxy Cluster Outer Regions

    NASA Technical Reports Server (NTRS)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Laue, E. T.; Roncarelli, M.; Rossetti, M.; Snowden, S. L.; Gastaldello, F.

    2012-01-01

    Aims. We present the analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Methods. We exploit the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius. We perform a stacking of the density profiles to detect a signal beyond r200 and measure the typical density and scatter in cluster outskirts. We also compute the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compare our average density and scatter profiles with the results of numerical simulations. Results. As opposed to some recent Suzaku results, and confirming previous evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond approximately r(sub 500). Comparing our density profiles with simulations, we find that non-radiative runs predict too steep density profiles, whereas runs including additional physics and/or treating gas clumping are in better agreement with the observed gas distribution. We report for the first time the high-confidence detection of a systematic difference between cool-core and non-cool core clusters beyond 0.3r(sub 200), which we explain by a different distribution of the gas in the two classes. Beyond r(sub 500), galaxy clusters deviate significantly from spherical symmetry, with only little differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the simulations. Conclusions. Comparing our results with numerical simulations, we find that non-radiative simulations fail to reproduce the gas distribution, even well outside cluster

  20. The Gas Distribution in the Outer Regions of Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Lau, E. T.; Roncarelli, M.; Rossetti, M.; Snowden, L.; Gastaldello, F.

    2012-01-01

    Aims. We present our analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Methods. We have exploited the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius, We stacked the density profiles to detect a signal beyond T200 and measured the typical density and scatter in cluster outskirts. We also computed the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compared our average density and scatter profiles with the results of numerical simulations. Results. As opposed to some recent Suzaku results, and confirming previous evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond approximately r(sub 500). Comparing our density profiles with simulations, we find that non-radiative runs predict density profiles that are too steep, whereas runs including additional physics and/ or treating gas clumping agree better with the observed gas distribution. We report high-confidence detection of a systematic difference between cool-core and non cool-core clusters beyond approximately 0.3r(sub 200), which we explain by a different distribution of the gas in the two classes. Beyond approximately r(sub 500), galaxy clusters deviate significantly from spherical symmetry, with only small differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the ENZO simulations. Conclusions. Comparing our results with numerical simulations, we find that non-radiative simulations fail to reproduce the gas distribution, even well outside

  1. Revealing galactic scale bars with the help of Galaxy Zoo

    NASA Astrophysics Data System (ADS)

    Masters, Karen L.

    2015-03-01

    We use visual classifications of the brightest 250,000 galaxies in the Sloan Digital Sky Survey Main Galaxy Sample provided by citizen scientists via the Galaxy Zoo project (www.galaxyzoo.org, Lintott et al. 2008) to identify a sample of local disc galaxies with reliable bar identifications. These data, combined with information on the atomic gas content from the ALFALFA survey (Haynes et al. 2011) show that disc galaxies with higher gas content have lower bar fractions. We use a gas deficiency parameter to show that disc galaxies with more/less gas than expected for their stellar mass are less/more likely to host bars. Furthermore, we see that at a fixed gas content there is no residual correlation between bar fraction and stellar mass. We argue that this suggests previously observed correlations between galaxy colour/stellar mass and (strong) bar fraction (e.g. from the sample in Masters et al. 2011, and also see Nair & Abraham 2010) could be driven by the interaction between bars and the gas content of the disc, since more massive, optically redder disc galaxies are observed to have lower gas contents. Furthermore we see evidence that at a fixed gas content the global colours of barred galaxies are redder than those of unbarred galaxies. We suggest that this could be due to the exchange of angular momentum beyond co-rotation which might stop a replenishment of gas from external sources, and act as a source of feedback to temporarily halt or reduce the star formation in the outer parts of barred discs. These results (published as Masters et al. 2012) combined with those of Skibba et al. (2012), who use the same sample to show a clear (but subtle and complicated) environmental dependence of the bar fraction in disc galaxies, suggest that bars are intimately linked to the evolution of disc galaxies.

  2. The local radio-galaxy population at 20 GHz

    NASA Astrophysics Data System (ADS)

    Sadler, Elaine M.; Ekers, Ronald D.; Mahony, Elizabeth K.; Mauch, Tom; Murphy, Tara

    2014-02-01

    We have made the first detailed study of the high-frequency radio-source population in the local Universe, using a sample of 202 radio sources from the Australia Telescope 20 GHz (AT20G) survey identified with galaxies from the 6dF Galaxy Survey (6dFGS). The AT20G-6dFGS galaxies have a median redshift of z = 0.058 and span a wide range in radio luminosity, allowing us to make the first measurement of the local radio luminosity function at 20 GHz. Our sample includes some classical Fanaroff-Riley type I (FR I) and FR II radio galaxies, but most of the AT20G-6dFGS galaxies host compact (FR 0) radio active galactic nuclei which appear to lack extended radio emission even at lower frequencies. Most of these FR 0 sources show no evidence for relativistic beaming, and the FR 0 class appears to be a mixed population which includes young compact steep-spectrum and gigahertz peaked-spectrum radio galaxies. We see a strong dichotomy in the Wide-field Infrared Survey Explorer (WISE) mid-infrared colours of the host galaxies of FR I and FR II radio sources, with the FR I systems found almost exclusively in WISE `early-type' galaxies and the FR II radio sources in WISE `late-type' galaxies. The host galaxies of the flat- and steep-spectrum radio sources have a similar distribution in both K-band luminosity and WISE colours, though galaxies with flat-spectrum sources are more likely