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Sample records for galaxy mcg-6-30-15 observed

  1. On the deep minimum state in the Seyfert galaxy MCG-6-30-15

    NASA Astrophysics Data System (ADS)

    Reynolds, Christopher S.; Wilms, Jörn; Begelman, Mitchell C.; Staubert, Rüdiger; Kendziorra, Eckhard

    2004-04-01

    We present a detailed spectral analysis of the first observation of the Seyfert 1 galaxy MCG-6-30-15 by the European Photon Imaging Camera on board the XMM-Newton observatory, together with contemporaneous data from the Proportional Counter Array on the Rossi X-ray Timing Explorer. Confirming our previously published result, we find that the presence of extremely broadened reflection features from an ionized relativistic accretion disc is required even when one employs the latest X-ray reflection models and includes the effect of complex absorption. The extremely broadened reflection features are also present if the primary continuum is modelled with a thermal Comptonization spectrum rather than a simple power-law continuum. With this fact established, we examine these data using a relativistic smearing function corresponding to a `generalized thin accretion disc' model. We find strong evidence for torquing of the central parts of the accretion disc (presumably through magnetic interactions with the plunging region of the disc and/or the rotating black hole itself). Indeed, within the context of these torqued disc models, this system appears to be in a torque-dominated (or `infinite-efficiency') state at the time of this observation. In addition, we find marginal evidence that the X-ray emitting corona radiates a greater fraction of the total dissipated energy in the inner portions of the disc. We also perform a study of spectral variability within our observation. We find that the disc reflection features maintain roughly a constant equivalent width with respect to the observed continuum, as predicted by simple reflection models. Taken together with other studies of MCG-6-30-15 that find disc features to possess constant intensity at higher flux states, we suggest that the flux of disc features undergoes a saturation once the source emerges from a deep minimum state. We discuss the implications of these results for the physics of the deep minimum `state

  2. The Broadband Spectral Variability of MCG-6-30-15 Observed by NuSTAR and XMM-Newton

    NASA Astrophysics Data System (ADS)

    Marinucci, A.; Matt, G.; Miniutti, G.; Guainazzi, M.; Parker, M. L.; Brenneman, L.; Fabian, A. C.; Kara, E.; Arevalo, P.; Ballantyne, D. R.; Boggs, S. E.; Cappi, M.; Christensen, F. E.; Craig, W. W.; Elvis, M.; Hailey, C. J.; Harrison, F. A.; Reynolds, C. S.; Risaliti, G.; Stern, D. K.; Walton, D. J.; Zhang, W.

    2014-05-01

    MCG-6-30-15, at a distance of 37 Mpc (z = 0.008), is the archetypical Seyfert 1 galaxy showing very broad Fe Kα emission. We present results from a joint NuSTAR and XMM-Newton observational campaign that, for the first time, allows a sensitive, time-resolved spectral analysis from 0.35 keV up to 80 keV. The strong variability of the source is best explained in terms of intrinsic X-ray flux variations and in the context of the light-bending model: the primary, variable emission is reprocessed by the accretion disk, which produces secondary, less variable, reflected emission. The broad Fe Kα profile is, as usual for this source, well explained by relativistic effects occurring in the innermost regions of the accretion disk around a rapidly rotating black hole. We also discuss the alternative model in which the broadening of the Fe Kα is due to the complex nature of the circumnuclear absorbing structure. Even if this model cannot be ruled out, it is disfavored on statistical grounds. We also detected an occultation event likely caused by broad-line region clouds crossing the line of sight.

  3. The Chandra High Energy Transmission Grating Spectrometer probes the dusty warm absorber in the Seyfert 1 galaxy MCG-6-30-15

    NASA Astrophysics Data System (ADS)

    Lee, J. C.; Canizares, C. R.; Marshall, H. L.; Morales, R.; Schulz, N. S.; Iwasawa, K.

    The Chandra HETGS spectra of the Seyfert 1 galaxy MCG-6-30-15 show numerous narrow, unresolved (FWHM ≈< 200 km s-1) absorption lines from a wide range of ionization states of N, O, Mg, Ne, Si, S, Ar, and Fe. The initial analysis of these data, presented in Lee et al. (2001), shows that a dusty warm absorber model adequately explains the spectral features ≈> 0.48 keV (≈< 26 Å ). We attribute previous reports of an apparently highly redshifted O VII edge to the neutral Fe L absorption complex and the O VII resonance series (by transitions higher than He γ He α,β,γ are also seen at lower energies). The implied dust column density needed to explain the Fe I L edge feature agrees with that obtained from earlier reddening studies, which had already concluded that the dust should be associated with the ionized absorber (given the relatively lower observed X-ray absorption by cold gas). Our findings contradict the interpretation of Branduardi-Raymont et al. (2001), based on XMM RGS spectra, that this spectral region is dominated by highly relativistic soft X-ray line emission originating near the central black hole. Here we review these issues pertaining to the soft X-ray spectral features as addressed by Lee et al., (2001). Details found in Lee et al., 2001, ApJ., 554, L13

  4. Probing MCG-6-30-15 with the Chandra HETGS

    NASA Astrophysics Data System (ADS)

    Lee, J. C.; Canizares, C. R.; Fang, T.; Morales, R.; Fabian, A. C.; Marshall, H. L.; Schulz, N. S.

    The Chandra HETGS spectra of the Seyfert 1 galaxy MCG-6-30-15 show numerous narrow, unresolved (FWHM ≈ < 200 m s-1) absorption lines from a wide range of ionization states of N, O, Mg, Ne, Si, S, Ar, and Fe. The initial analysis of these data, presented in Lee et al. (2001), shows that a dusty warm absorber is reasonable for explaining the soft X-ray spectral features ≈> 0.48 keV (≈< 26 Å ). The implied Hydrogen column density needed to explain the Fe I L edge feature at ~0.707 keV agrees with that obtained from earlier reddening studies. Both results point to dust embedded in the ionized absorber of MCG-6-30-15 (given the relatively lower observed X-ray absorption by cold gas). This conclusion is contrary to the results reported from XMM which call for relativistically broadened soft X-ray emission line. We also report on preliminary results from Lee et al. (in preparation) based on a full treatment of the warm absorber in MCG-6-30-15 in the Chandra spectral bandpass, which shows a distribution of v and NH which depend on ξ and may point to an outflow in the warm absorber of MCG-6-30-15. The results of the in-depth analysis are consistent with those previously published. This proceeding is intended as a review of the findings for the soft 0.5-1 keV X-ray spectrum of MCG-6-30-15 presented by Lee et al. (2001a,b) for the ~67 ks subset of the Chandra HETGS (Lee et al. 2001a,b) AO1 observation corresponding to the period with high continuum flux. Preliminary results (as presented during this meeting) for the full length of the 120 ks integration are reported as highlights from Lee et al., in preparation. Details from the initial papers can be found in Lee et al., 2001, ApJ., 554, L13, and the conference proceeding from ``X-ray emission from Accretion onto Black Holes''

  5. X-ray continuum variability of MCG-6-30-15

    NASA Astrophysics Data System (ADS)

    Vaughan, S.; Fabian, A. C.; Nandra, K.

    2003-03-01

    This paper presents a comprehensive examination of the X-ray continuum variability of the bright Seyfert 1 galaxy MCG-6-30-15. The source clearly shows the strong, linear correlation between rms variability amplitude and flux first seen in Galactic X-ray binaries. The high-frequency power spectral density (PSD) of MCG-6-30-15 is examined in detail using a Monte Carlo fitting procedure and is found to be well represented by a steep power law at high frequencies (with a power-law index α~ 2.5), breaking to a flatter slope (α~ 1) below fbr~ 0.6-2.0 × 10-4 Hz, consistent with the previous results of Uttley, McHardy & Papadakis. The slope of the power spectrum above the break is energy dependent, with the higher energies showing a flatter PSD. At low frequencies the variations between different energy bands are highly coherent, while at high frequencies the coherence is significantly reduced. Time lags are detected between energy bands, with the soft variations leading the hard ones. The magnitude of the lag is small (<~200 s for the frequencies observed) and is most likely frequency dependent. These properties are remarkably similar to the temporal properties of the Galactic black hole candidate Cygnus X-1. The characteristic time-scales in these two types of source differ by ~105 assuming that these time-scales scale linearly with black hole mass then suggests a black hole mass ~106 Msolar for MCG-6-30-15. We speculate that the timing properties of MCG-6-30-15 may be analogous to those of Cyg X-1 in its high/soft state and discuss a simple phenomenological model, originally developed to explain the timing properties of Cyg X-1, which can explain many of the observed properties of MCG-6-30-15.

  6. Long-term monitoring of the archetype Seyfert galaxy MCG-6-30-15: X-ray, optical and near-IR variability of the corona, disc and torus

    NASA Astrophysics Data System (ADS)

    Lira, P.; Arévalo, P.; Uttley, P.; McHardy, I. M. M.; Videla, L.

    2015-11-01

    We present long-term monitoring of MCG-6-30-15 in X-rays, optical and near-IR wavelengths, collected over 5 yr of monitoring. We determine the power spectrum density of all the observed bands and show that after taking into account the host contamination similar power is observed in the optical and near-IR bands. There is evidence for a correlation between the light curves of the X-ray photon flux and the optical B band, but it is not possible to determine a lag with certainty, with the most likely value being around 0 d. Strong correlation is seen between the optical and near-IR bands. Cross-correlation analysis shows some complex probability distributions and lags that range from 10 to 20 d, with the near-IR following the optical variations. Filtering the light curves in frequency space shows that the strongest correlations are those corresponding to the shortest time-scales. We discuss the nature of the X-ray variability and conclude that this is intrinsic and cannot be accounted for by absorption episodes due to material intervening in the line of sight. It is also found that the lags agree with the relation τ ∝ λ4/3, as expected for an optically thick geometrically thin accretion disc, although for a larger disc than that predicted by the estimated black hole mass and accretion rate in MCG-6-30-15. The cross-correlation analysis suggests that the torus is located at ˜20 light-days from the central source and at most at ˜50 light-days from the central region. This implies an active galactic nucleus bolometric luminosity of ˜3 × 1043 erg s-1 cm-2.

  7. On the location and composition of the dust in the MCG-6-30-15 warm absorber

    NASA Astrophysics Data System (ADS)

    Ballantyne, D. R.; Weingartner, J. C.; Murray, N.

    2003-10-01

    The warm absorber observed in the Seyfert 1 galaxy MCG-6-30-15 is known to consist of at least two zones and very likely contains dust. Hubble Space Telescope images of MCG-6-30-15 show a dust lane crossing the galaxy just below the nucleus. In this paper, we argue that this dust lane is responsible for the observed reddening of the nuclear emission and the Fe I edge hinted at in the Chandra spectrum of MCG-6-30-15. We further suggest that the gas within the dust lane can comprise much of the low ionization component (i.e., the one contributing the O VII edge) of the observed warm absorber. Moreover, placing the warm absorbing material at such distances (hundreds of pc) can account for the small outflow velocities of the low ionization absorption lines as well as the constancy of the O VII edge. Photoionization models of a dusty interstellar gas cloud (with a column appropriate for the reddening toward MCG-6-30-15) using a toy Seyfert 1 spectral energy distribution show that it is possible to obtain a significant O VII edge (tau ~ 0.2) if the material is ~ 150 pc from the ionizing source. For MCG-6-30-15, such a distance is consistent with the observed dust lane. We emphasize the point first made by Kraemer et al.: dusty interstellar material will likely contribute to the warm absorber, and should be included in spectral modeling. The current data on MCG-6-30-15 is unable to constrain the dust composition within the warm absorber. Astronomical silicate is a viable candidate, but there are indications of a very low O abundance in the dust, which is inconsistent with a silicate origin. If true, this may indicate that there were repeated cycles of grain destruction and growth from shocks in the interstellar medium of MCG-6-30-15. Pure iron grains are an unlikely dust constituent due to the limit on their abundance in the Galaxy, yet they cannot be ruled out. The high column densities inferred from the highly ionized zone of the warm absorber implies that this gas is

  8. Tracing the origin of the AGN fuelling reservoir in MCG-6-30-15

    NASA Astrophysics Data System (ADS)

    Raimundo, S. I.; Davies, R. I.; Canning, R. E. A.; Celotti, A.; Fabian, A. C.; Gandhi, P.

    2017-02-01

    The active galaxy MCG-6-30-15 has a 400 pc diameter stellar kinematically distinct core, counter-rotating with respect to the main body of the galaxy. Our previous high spatial resolution (0.1 arcsec) H-band observations of this galaxy mapped the stellar kinematics and [Fe II] 1.64 μm gas dynamics though mainly restricted to the spatial region of the counter-rotating core. In this work, we probe the stellar kinematics on a larger field of view and determine the ionized and molecular gas dynamics to study the formation of the counter-rotating core and the implications for active galactic nucleus (AGN) fuelling. We present integral field spectroscopy observations with SINFONI in the H and K bands in the central 1.2 kpc and with VIMOS HR-blue in the central 4 kpc of the galaxy. Ionized gas outflows of vout ˜ 100 km s-1 are traced by the [Ca VIII] 2.32 μm coronal line and extend out to at least a radius of r ˜ 140 pc. The molecular gas, traced by the H2 2.12 μm emission, is also counter-rotating with respect to the main body of the galaxy, indicating that the formation of the distinct core was associated with inflow of external gas into the centre of MCG-6-30-15. The molecular gas traces the available gas reservoir for AGN fuelling and is detected as close as r ˜ 50-100 pc. External gas accretion is able to significantly replenish the fuelling reservoir suggesting that the event which formed the counter-rotating core was also the main mechanism providing gas for AGN fuelling.

  9. The changing X-ray time lag in MCG-6-30-15

    NASA Astrophysics Data System (ADS)

    Kara, E.; Fabian, A. C.; Marinucci, A.; Matt, G.; Parker, M. L.; Alston, W.; Brenneman, L. W.; Cackett, E. M.; Miniutti, G.

    2014-11-01

    MCG-6-30-15 is one of the most observed narrow-line Seyfert 1 galaxies in the X-ray band. In this paper, we examine the X-ray time lags in this source using a total of 600 ks in observations (440 ks exposure) taken with the XMM-Newton telescope (300 ks in 2001 and 300 ks in 2013). Both the old and new observations show the usual hard lag that increases with energy; however, the hard lag turns over to a soft lag at frequencies below ˜10-4 Hz. The highest frequencies (˜10-3 Hz) in this source show a clear soft lag, as previously presented for the first 300 ks observation, but no clear iron K lag is detected in either the old or new observation. The soft lag is more significant in the old observation than the new. The observations are consistent with a reverberation interpretation, where the soft, reflected emission is delayed with respect to the hard power-law component. These spectral timing results suggest that two distinct variability mechanisms are important in this source: intrinsic coronal variations (which lead to correlated variability in the reprocessed emission) and geometrical changes in the corona. Variability due to geometrical changes does not result in correlated variability in the reflection, and therefore inhibits the clear detection of an iron K lag.

  10. The evidence against Comptonization as a mechanism to explain the Fe Kα line profile in MCG-6-30-15

    NASA Astrophysics Data System (ADS)

    Ruszkowski, M.; Fabian, A. C.; Ross, R. R.; Iwasawa, K.

    2000-09-01

    It has recently been suggested that Compton down-scattering may give rise to the broad iron Kα line seen in the X-ray spectrum of the Seyfert 1 galaxy MCG-6-30-15. This model suggests that the Comptonizing optically thick plasma surrounding the central X-ray source has a temperature of 0.5keV and a large radius of 1014cm. This offers an alternative to the standard model whereby the broadening of the iron line is solely the result of strong general relativistic effects. We revise the Comptonization model and show that statistically the disc-line model gives a much better fit to the time average of the data analysed by Iwasawa et al. in 1996 and 1999. We also demonstrate that the Comptonization model has problems with simultaneous fitting of the redshifted tail and the core of the line. We show that, in the case of the 1996 data, the best-fitting Thomson depth τ~1.6 is consistent with the lack of continuum break, which is constrained to be at photon energies E>~100keV. However, the total amount of power in the UV component required to cool the Comptonizing cloud exceeds the Eddington limit. For large black hole masses relativistic effects are important and for small masses the Eddington limit is exceeded by a larger factor. In the case of the 1999 data, the best-fitting Thomson depth is τ~5.7 this would imply the existence of a break in the continuum at E~16keV, which is not observed. (However, we point out that the down-scattering break may be diluted if a fraction of the continuum is observed directly.) This rules out Comptonization as the principal mechanism to explain the shape of the Fe Kα line in MCG-6-30-15.

  11. An Extended Multi-Zone Model for the MCG-6-30-15 Warm Absorber

    NASA Technical Reports Server (NTRS)

    Morales, R.; Fabian, A. C.; Reynolds, C. S.

    2000-01-01

    The variable warm absorber seen with ASCA in the X-ray spectrum of MCG 6-30-15 shows complex time behaviour in which the optical depth of O VIII anticorrelates with the flux whereas that of O VII is unchanging. The explanation in terms of a two zone absorber has since been challenged by BeppoSAX observations. These present a more complicated behaviour for the O VII edge. The explanation we offer for both ASCA and BeppoSAX observations requires a very simple photoionization model together with the presence of a third, intermediate, zone and a period of very low luminosity. In practice warm absorbers are likely to be extended, multi-zone regions of which only part causes directly observable absorption edges at any given time depending on the value of the luminosity.

  12. Probing the Dusty Warm Absorbers in MCG-6-30-15 & Mrk 766 with the Chandra HETG

    NASA Astrophysics Data System (ADS)

    Canizares, Claude R.; Lee, Julia C.; Marshall, Herman L.; Schulz, Norbert S.

    2001-09-01

    HETG spectra of the Seyfert 1 galaxy MCG-6-30-15 show numerous narrow, unresolved (FWHM < 200 km s-1) absorption lines from a wide range of ionization states of N, O, Mg, Ne, Si, S, Ar, and Fe. The initial analysis of these data, presented in Lee et al. (2001), shows that a dusty warm absorber model adequately explains the spectral features > 0.48 keV (< 26 Å ). We attribute previous reports of an apparently highly redshifted O VII edge to the 1s2-1snp (n > 5) O VII resonance lines, and a neutral Fe L absorption complex. The implied dust column density needed to explain the Fe L feature agrees with that obtained from earlier reddening studies, which had already concluded that the dust should be associated with the ionized absorber (given the relatively lower observed absorption by cold gas). Our findings contradict the interpretation of Branduardi-Raymont et al. (2001), based on XMM-Newton RGS spectra, that this spectral region is dominated by highly relativistic soft X-ray line emission originating near the central black hole. Here we review these issues and present more detailed measurements of the absorption lines, constrain the implied range of ionization in the warm absorber, and present the HETG spectrum of the Fe K line region. In addition, we present preliminary results on the HETG spectrum of another reddened Seyfert galaxy, Mrk 766, which Branduardi-Raymont et al. also reported as containing relativistic soft X-ray lines.

  13. Soft X-Ray Emission Lines from a Relativistic Accretion Disk in MCG -6-30-15 and Mrk 766

    NASA Technical Reports Server (NTRS)

    Branduardi-Raymont, G.; Sako, M.; Kahn, S. M.; Brinkman, A. C.; Kaastra, J. S.; Page, M. J.

    2000-01-01

    XMM-Newton Reflection Grating Spectrometer (RGS) spectra of the Narrow Line Seyfert 1 galaxies MCG -6-30-15 and Mrk 766 are physically and spectroscopically inconsistent with standard models comprising a power-law continuum absorbed by either cold or ionized matter. We propose that the remarkably similar features detected in both objects in the 5 - 35 A band are H-like oxygen, nitrogen, and carbon emission lines, gravitation- ally redshifted and broadened by relativistic effects in the vicinity of a Kerr black hole. We discuss the implications of our interpretation, and demonstrate that the derived parameters can be physically self-consistent.

  14. Revealing the Dusty Warm Absorber in MCG -6-30-15 with the Chandra High-Energy Transmission Grating

    NASA Astrophysics Data System (ADS)

    Lee, Julia C.; Ogle, Patrick M.; Canizares, Claude R.; Marshall, Herman L.; Schulz, Norbert S.; Morales, Raquel; Fabian, Andrew C.; Iwasawa, Kazushi

    2001-06-01

    We present detailed evidence for a warm absorber in the Seyfert 1 galaxy MCG -6-30-15 and dispute earlier claims for relativistic O line emission. The High-Energy Transmission Grating spectra show numerous narrow, unresolved (FWHM<~200 km s-1) absorption lines from a wide range of ionization states of N, O, Mg, Ne, Si, S, Ar, and Fe. The O VII edge and the 1s2-1snp resonance line series to n=9 are clearly detected at rest in the active galactic nucleus frame. We attribute previous reports of an apparently highly redshifted O VII edge to the 1s2-1snp (n>5) O VII resonance lines and a neutral Fe L absorption complex. The shape of the Fe L feature is nearly identical to that seen in the spectra of several X-ray binaries and in laboratory data. The implied dust column density agrees with that obtained from reddening studies and gives the first direct X-ray evidence for dust embedded in a warm absorber. The O VIII resonance lines and the weak edge are also detected, and the spectral rollover below ~2 keV is explained by the superposition of numerous absorption lines and edges. We identify, for the first time, a KLL resonance in the O VI photoabsorption cross section, giving a measure of the O VI column density. The O VII (f) emission detected at the systemic velocity implies a covering fraction of ~5% (depending on the observed vs. time-averaged ionizing flux). Our observations show that a dusty warm absorber model is not only adequate to explain all the spectral features >~0.48 keV (<~26 Å) but that the data require it. This contradicts the interpretation of Branduardi-Raymont and coworkers that this spectral region is dominated by highly relativistic line emission from the vicinity of the black hole.

  15. Probing Supermassive Black Hole Spins in MCG--6-30-15 and NGC 1365 with XMM-Newton and NuSTAR

    NASA Astrophysics Data System (ADS)

    Brenneman, Laura; Walton, Dom; Marinucci, Andrea; Matt, Giorgio; Risaliti, Guido; Harrison, Fiona; Stern, Daniel

    2014-08-01

    We report on detailed spectral modeling of the Seyfert 1 AGNs NGC 1365 and MCG--6-30-15 using simultaneous, broadband X-ray spectra from XMM-Newton and NuSTAR. Both of these galaxies show evidence for relativistic reflection from the inner accretion disk in addition to complex, variable absorption. The high signal-to-noise across the 0.3-79 keV energy band enabled by these observations allows us to definitively disentangle the spectral signatures of the continuum, warm and cold absorption, and reflection from the torus and the inner disk in both sources. These deep pointings also enable the use of time-resolved spectral fitting in order to assess the role of each component in driving the spectral and temporal variability of the AGNs. This type of analysis allows us to isolate the relativistic reflection signatures in each object, facilitating the most accurate, precise constrains ever obtained on the spins of their supermassive black holes. We present our spin measurements, as well as a discussion of sources of systematic error. Finally, we place our results in the context of relativistic light-bending models in an effort to characterize the structure of the innermost regions of these AGNs.

  16. Measuring Supermassive Black Hole Spins in NGC 1365 and MCG--6-30-15 Using XMM-Newton and NuSTAR

    NASA Astrophysics Data System (ADS)

    Brenneman, Laura; Marinucci, Andrea; Walton, Dom; Risaliti, Guido; Matt, Giorgio; Harrison, Fiona; Stern, Daniel

    2014-06-01

    We report on detailed spectral modeling of the Seyfert 1 AGN NGC 1365 and MCG--6-30-15 using simultaneous, broadband X-ray spectra from XMM-Newton and NuSTAR. Both of these galaxies show evidence for relativistic reflection from the inner accretion disk in addition to complex, variable absorption. The high signal-to-noise across the 0.2-79 keV energy band enabled by these observations allows us to definitively disentangle the spectral signatures of the continuum, warm and cold absorption, and reflection from the torus and the inner disk in both sources. These deep pointings also enable the use of time-resolved spectral fitting in order to assess the role of each component in driving the spectral and temporal variability of the AGN. This type of analysis allows us to isolate the relativistic reflection signatures in each object, facilitating the most accurate, precise constrains ever obtained on the spins of their supermassive black holes.

  17. Broad line emission from iron K- and L-shell transitions in the active galaxy 1H 0707-495.

    PubMed

    Fabian, A C; Zoghbi, A; Ross, R R; Uttley, P; Gallo, L C; Brandt, W N; Blustin, A J; Boller, T; Caballero-Garcia, M D; Larsson, J; Miller, J M; Miniutti, G; Ponti, G; Reis, R C; Reynolds, C S; Tanaka, Y; Young, A J

    2009-05-28

    Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG-6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies, from accreting stellar-mass black holes and even from accreting neutron stars. The iron K line is prominent in the reflection spectrum created by the hard-X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron L-line emission should be detectable when the iron abundance is high. Here we report the presence of both iron K and iron L emission in the spectrum of the narrow-line Seyfert 1 galaxy 1H 0707-495. The bright iron L emission has enabled us to detect a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the black hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole. The combination of spectral and timing data on 1H 0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light minute, from the event horizon of a rapidly spinning, massive black hole.

  18. Theoretical and Observational Studies of the Central Engines of AGN

    NASA Technical Reports Server (NTRS)

    Sivron, Ran

    1995-01-01

    In Active Galactic Nuclei (AGN) the luminosity is so intense that the effect of radiation pressure on a particle may exceed the gravitational attraction. It was shown that when such luminosities are reached, relatively cold (not completely ionized) thermal matter clouds may form in the central engines of AGN, where most of the luminosity originates. We show that the spectrum of emission from cold clouds embedded in hot relativistic matter is similar to the observed spectrum. We also show that within the hot relativistic matter, cold matter moves faster than the speed of sound or the Alfven speed, and shocks form. The shocks provide a mechanism by which a localized perturbation can propagate throughout the central engine. The shocked matter can emit the observed luminosity, and can explain the flux and spectral variability. It may also provide an efficient mechanism for the outward transfer of angular momentum and provide the outward flow of winds. With observations from X-ray satellites, emission features from the cold and hot matter may be revealed. Our analysis of X-ray data from the Seyfert 1 galaxy MCG - 6-30-15 over five years using detectors on the Ginga and Rosat satellites, revealed some interesting variable features. A source with hot matter emits non-thermal radiation which is Compton reflected from cold matter and then absorbed by warm (partially ionized) absorbing matter in the first model, which can be fit to the data if both the cold and warm absorbers are near the central engine. An alternative model in which the emission from the hot matter is partially covered by very warm matter (in which all elements except Iron are mostly ionized) is also successful. In this model the cold and warm matter may be at distances of up to 100 times the size of the central engine, well within the region where broad optical lines are produced. The flux variability is more naturally explained by the second model. Our results support the existence of cold matter in, or

  19. Ginga observations of Seyfert galaxies

    NASA Technical Reports Server (NTRS)

    Awaki, H.; Koyama, K.

    1993-01-01

    We observed twenty-eight Seyfert 2 galaxies with the Japanese X-ray satellite, Ginga, and found Seyfert 2 galaxies, in general, have the X-ray spectral characteristics of obscured Seyfert 1 nuclei. This results agrees with the predictions from the Unified Seyfert model proposed by Antonucci and Miller. However, among the observed Seyfert 2 galaxies, there are a few galaxies with no evidence of an obscuration, contrary to the general predictions of the unified model. We note that type 2 active galactic nuclei (AGN) will contribute to the Cosmic Diffuse X-ray Background, if the unified Seyfert model can be extended to the far distant AGN such as quasars.

  20. Spectroscopic Observations of Merging Galaxies

    NASA Astrophysics Data System (ADS)

    Donzelli, C. J.; Pastoriza, M. G.

    2000-07-01

    In this paper we describe the spectroscopic and infrared properties of a sample of 25 merging galaxy pairs, selected from the catalog of Arp & Madore, and we compare them with those observed in a similar sample of interacting galaxies (Donzelli & Pastoriza). It is noted that mergers as well as interacting systems comprise a wide range of spectral types, going from those corresponding to well-evolved stellar populations (older than 200 Myr) to those that show clear signatures of H II regions with stellar populations younger than 8 Myr. However, merger galaxies show on average more excited spectra than interacting pairs, which could be attributed to lower gas metallicity. From the emission lines we also found that merging systems show on average higher (about a factor of 2) star formation rates than interacting galaxies. Classical diagnostic diagrams show that only three of 50 of the galaxies (6%) present some form of nuclear activity: two Seyfert galaxies and one LINER. However, through a detailed analysis of the pure emission-line spectra, we conclude that this fraction may raise up to 23% of the mergers if we consider that some galaxies host a low-luminosity active nucleus surrounded by strong star-forming regions. This latter assumption is also supported by the infrared colors of the galaxies. Regarding to the total infrared luminosities, the merging galaxies show on average an IR luminosity, log(Lir)=10.7, lower than that of interacting systems, log(Lir)=10.9. We find that only three mergers of the sample (12%) can be classified as luminous infrared galaxies, while this fraction increases to 24% in the interacting sample. Based on observations made at CASLEO. Complejo Astronómico El Leoncito is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan.

  1. The Relativistic Iron Line Profile in the Seyfert 1 Galaxy IC4329a

    NASA Technical Reports Server (NTRS)

    Done, C.; Madejski, G. M.; Zycki, P. T.

    2000-01-01

    We present simultaneous ASCA and RXTE data on the bright Seyfert 1 galaxy IC4329a. The iron line is significantly broadened, but not to the extent expected from an accretion disk which extends down to the last stable orbit around a black hole. We marginally detect a narrow line component, presumably from the molecular torus, but, even including this gives a line profile from the accretion disk which is significantly narrower that that seen in MCG-6-30-15, and is much more like that seen from the low/hard state galactic black hole candidates. This is consistent with the inner disk being truncated before the last stable orbit, forming a hot flow at small radii as in the ADAF models. However. we cannot rule out the presence of an inner disk which does not contribute to the reflected spectrum. either because of extreme ionisation suppressing the characteristic atomic features of the reflected spectrum or because the X-ray source is intrinsically anisotropic, so it does not illuminate the inner disk. The source was monitored by RXTE every 2 days for 2 months, and these snapshot spectra show that there is intrinsic spectral variability. The data are good enough to disentangle the power law from the reflected continuum and we see that the power law softens as the source brightens. The lack of a corresponding increase in the observed reflected spectrum implies that either the changes in disk inner radial extent/ionization structure are small, or that the variability is actually driven by changes in the seed photons which are decoupled from the hard X-ray mechanism.

  2. Assessing black hole spin in deep Suzaku observations of Seyfert 1 AGN

    NASA Astrophysics Data System (ADS)

    Patrick, A. R.; Reeves, J. N.; Lobban, A. P.; Porquet, D.; Markowitz, A. G.

    2011-10-01

    We present a broad-band analysis of deep Suzaku observations of nearby Seyfert 1 active galactic nuclei (AGN): Fairall 9, MCG-6-30-15, NGC 3516, 3783 and 4051. The use of deep observations (exposures >200 ks) with high signal-to-noise ratio allows the complex spectra of these objects to be examined in full, taking into account features such as the soft excess, reflection continuum and complex absorption components. After a self-consistent modelling of the broad-band data (0.6-100.0 keV, also making use of Burst Alert Telescope data from Swift), the subtle curvature which may be introduced as a consequence of warm absorbers has a measured affect upon the spectrum at energies >3 keV and the Fe K region. Forming a model (including absorption) of these AGN allows the true extent to which broadened disc line emission is present to be examined and as a result the measurement of accretion disc and black hole parameters which are consistent over the full 0.6-100.0 keV energy range. Fitting relativistic line emission models appears to rule out the presence of maximally spinning black holes in all objects at the 90 per cent confidence level, in particular MCG-6-30-15 at >99.5 per cent confidence. Relativistic Fe K line emission is only marginally required in NGC 3516 and not required in NGC 4051, over the full energy bandpass. None the less, statistically significant broadened 6.4 keV Fe Kα emission is detected in Fairall 9, MCG-6-30-15 and NGC 3783 yielding black hole spin estimates of a= 0.67+0.10- 0.11, a= 0.49+0.20- 0.12 and a < -0.04, respectively, when fitted with disc emission models.

  3. BLAST Observations of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Thomas, Nicholas Evan; Ade, P. A. R.; Bock, J. J.; Chapin, E. L.; Devlin, M. J.; Dicker, S.; Griffin, M.; Gundersen, J. O.; Halpern, M.; Hargrave, P. C.; Hughes, D. H.; Klein, J.; Marsden, G.; Martin, P. G.; Mauskopf, P.; Netterfield, C. B.; Olmi, L.; Pascale, E.; Patanchon, G.; Rex, M.; Scott, D.; Semisch, C.; Truch, M. D. P.; Tucker, C.; Tucker, G. S.; Viero, M. P.; Wiebe, D. V.

    2009-01-01

    The Balloon-born Large Aperture Submillimeter Telescope (BLAST) is a 1.8 m mirror that uses focal plane arrays of bolometer detectors at 250, 350 and 500 microns to study the evolutionary history and processes associated with star formation. The most recent long duration balloon flight from Antarctica collected 250 hours of data during a circumpolar flight in December 2006. A large number of observations were conducted including deep and wide surveys to characterize submillimeter galaxies, a galactic plane survey in the Vela region, and a number of pointed observations toward nearby galaxies NGC1097, NGC1291, NGC1365, NGC1512, NGC1566, and NGC1808. In this talk we will focus on these galaxies and combine the BLAST data with Spitzer-MIPS data to uniquely determine dust properties such as temperature and emissivity. The BLAST collaboration acknowledges the support of NASA through grants NAG5 12785, NAG5-13301, and NNGO-6GI11G, the Canadian Space Agency (CSA), the Science and Technology Facilities Council (STFC), Canada's Natural Sciences and Engineering Research Council (NSERC), the Canada Foundation for Innovation, the Ontario Innovation Trust, the Puerto Rico Space Grant Consortium, the Fondo Institucional para la Investigacion of the University of Puerto Rico, and the National Science Foundation Office of Polar Programs.

  4. Observations and Models of Galaxy Assembly Bias

    NASA Astrophysics Data System (ADS)

    Campbell, Duncan A.

    2017-01-01

    The assembly history of dark matter haloes imparts various correlations between a halo’s physical properties and its large scale environment, i.e. assembly bias. It is common for models of the galaxy-halo connection to assume that galaxy properties are only a function of halo mass, implicitly ignoring how assembly bias may affect galaxies. Recently, programs to model and constrain the degree to which galaxy properties are influenced by assembly bias have been undertaken; however, the extent and character of galaxy assembly bias remains a mystery. Nevertheless, characterizing and modeling galaxy assembly bias is an important step in understanding galaxy evolution and limiting any systematic effects assembly bias may pose in cosmological measurements using galaxy surveys.I will present work on modeling and constraining the effect of assembly bias in two galaxy properties: stellar mass and star-formation rate. Conditional abundance matching allows for these galaxy properties to be tied to halo formation history to a variable degree, making studies of the relative strength of assembly bias possible. Galaxy-galaxy clustering and galactic conformity, the degree to which galaxy color is correlated between neighbors, are sensitive observational measures of galaxy assembly bias. I will show how these measurements can be used to constrain galaxy assembly bias and the peril of ignoring it.

  5. IRAS observations of active galaxies

    NASA Technical Reports Server (NTRS)

    Neugebauer, G.; Soifer, B. T.; Rowan-Robinson, M.

    1985-01-01

    The IRAS survey gives an unbiased view of the infrared properties of the active galaxies. Seyfert galaxies occupy much the same area in color-color plots as to normal infrared bright galaxies, but extend the range towards flatter 60 to 25 mm slopes. Statistically the Seyfert 1 galaxies can be distinguished from the Seyfert 2 galaxies, lying predominantly closer to the area with constant slopes between 25 and 200 mm. The infrared measurements of the Seyfert galaxies cannot distinguish between the emission mechanisms in these objects although they agree with the currently popular ideas; they do provide a measure of the total luminosity of the Seyferts. The quasar's position in the color-color diagrams continue the trend of the Seyferts. The quasar 3C48 is shown to be exceptional among the radio loud quasars in that it has a high infrared luminosity which dominates the power output of the quasar and is most likely associated with the underlying host galaxy.

  6. IRAS observations of Seyfert galaxies

    NASA Technical Reports Server (NTRS)

    Miley, G. K.; Neugebauer, G.; Soifer, B. T.

    1985-01-01

    Infrared Astronomy Satellite measurements at 25, 60 and 100 microns were used to analyze the infrared properties of Seyfert galaxies from the Markarian and NGC Catalogs. One hundred and sixteen of 186 Seyfert galaxies were detected. About 50% of all Seyfert galaxies in the sample have 60 micron luminosities in excess of 10 to the 10th power solar luminosity, and the mean 60 micron luminosity increase with the optical B absolute magnitude. The luminosity functions of the Seyfert 1 and Seyfert 2 galaxies appear quite similar. It is possible, however, to statistically separate the two types of galaxies in color-color plots. The 100- to 60- micron energy distributions flatten systematically with increasing 60- micron luminosity. The infrared measurements provide a measure of the bolometric luminosity of the Seyfert galaxies, but do not discriminate between the physical processes involved.

  7. Observations of faint field galaxies

    NASA Technical Reports Server (NTRS)

    Koo, David C.

    1987-01-01

    Number counts, colors, and angular correlations of field galaxies fainter than 20th mag are summarized. Resulting conclusions regarding the presence and nature of luminosity, spectral, and clustering evolution remain contraversial. Preliminary analysis of two major spectroscopic surveys near completion suggests that by z approximately 0.5, larger numbers of very blue galaxies of moderate luminosities are found than today. The skewer-like surveys also provide new probes of galaxy clustering on scales previously unexplored (larger than 200 Mpc) and over lookback times of several billion years.

  8. HC3N observations of nearby galaxies

    NASA Astrophysics Data System (ADS)

    Jiang, Xue-Jian; Wang, Jun-Zhi; Gao, Yu; Gu, Qiu-Sheng

    2017-04-01

    Aims: We aim to systematically study the properties of the different transitions of the dense molecular gas tracer HC3N in galaxies. Methods: We have conducted single-dish observations of HC3N emission lines towards a sample of nearby gas-rich galaxies. HC3N(J = 2-1) was observed in 20 galaxies with the Effelsberg 100-m telescope. HC3N(J = 24-23) was observed in nine galaxies with the 10-m Submillimeter Telescope (SMT). Results: HC3N 2-1 is detected in three galaxies: IC 342, M 66, and NGC 660 (> 3σ). HC3N 24-23 is detected in three galaxies: IC 342, NGC 1068, and IC 694. These are the first measurements of HC3N 2-1 in a relatively large sample of external galaxies, although the detection rate is low. For the HC3N 2-1 non-detections, upper limits (2σ) are derived for each galaxy, and stacking the non-detections is attempted to recover the weak signal of HC3N. The stacked spectrum, however, does not show any significant signs of HC3N 2-1 emission. The results are also compared with other transitions of HC3N observed in galaxies. Conclusions: The low detection rate of both transitions suggests low abundance of HC3N in galaxies, which is consistent with other observational studies. The comparison between HC3N and HCN or HCO+shows a large diversity in the ratios between HC3N and HCN or HCO+. More observations are needed to interpret the behavior of HC3N in different types of galaxies.

  9. Galaxy Alignments: Observations and Impact on Cosmology

    NASA Astrophysics Data System (ADS)

    Kirk, Donnacha; Brown, Michael L.; Hoekstra, Henk; Joachimi, Benjamin; Kitching, Thomas D.; Mandelbaum, Rachel; Sifón, Cristóbal; Cacciato, Marcello; Choi, Ami; Kiessling, Alina; Leonard, Adrienne; Rassat, Anais; Schäfer, Björn Malte

    2015-11-01

    Galaxy shapes are not randomly oriented, rather they are statistically aligned in a way that can depend on formation environment, history and galaxy type. Studying the alignment of galaxies can therefore deliver important information about the physics of galaxy formation and evolution as well as the growth of structure in the Universe. In this review paper we summarise key measurements of galaxy alignments, divided by galaxy type, scale and environment. We also cover the statistics and formalism necessary to understand the observations in the literature. With the emergence of weak gravitational lensing as a precision probe of cosmology, galaxy alignments have taken on an added importance because they can mimic cosmic shear, the effect of gravitational lensing by large-scale structure on observed galaxy shapes. This makes galaxy alignments, commonly referred to as intrinsic alignments, an important systematic effect in weak lensing studies. We quantify the impact of intrinsic alignments on cosmic shear surveys and finish by reviewing practical mitigation techniques which attempt to remove contamination by intrinsic alignments.

  10. Observational properties of compact groups of galaxies

    NASA Technical Reports Server (NTRS)

    Hickson, Paul

    1990-01-01

    Compact groups are small, relatively isolated, systems of galaxies with projected separations comparable to the diameters of the galaxies themselves. Two well-known examples are Stephan's Quintet (Stephan, 1877) and Seyfert's Sextet (Seyfert 1948a,b). In groups such as these, the apparent space density of galaxies approaches 10(exp 6) Mpc(sub -3), denser even than the cores of rich clusters. The apparent unlikeliness of the chance occurrence of such tight groupings lead Ambartsumyan (1958, 1975) to conclude that compact groups must be physically dense systems. This view is supported by clear signs of galaxy interactions that are seen in many groups. Spectroscopic observations reveal that typical relative velocities of galaxies in the groups are comparable to their internal stellar velocities. This should be conducive to strong gravitational interactions - more so than in rich clusters, where galaxy velocities are typically much higher. This suggests that compact groups could be excellent laboratories in which to study galaxy interactions and their effects. Compact groups often contain one or more galaxies whose redshift differs greatly from those of the other group members. If these galaxies are at the same distance as the other members, either entire galaxies are being ejected at high velocities from these groups, or some new physical phenomena must be occurring. If their redshifts are cosmological, we must explain why so many discordant galaxies are found in compact groups. In recent years much progress has been made in addressing these questions. Here, the author discusses the current observational data on compact groups and their implications.

  11. Observing Nearby Galaxies with CCAT

    NASA Astrophysics Data System (ADS)

    Armus, Lee; Stacey, G. J.; Wilson, C.; Bolatto, A. D.; Rangwala, N.; Nikola, T.; Kauffmann, J.; Bertoldi, F.; Glenn, J.; CCAT Team

    2013-01-01

    CCAT, with its 25m primary, advanced detectors and fast mapping speed will be extremely adept at deep, large-scale surveys for distant, dusty galaxies in the early Universe, and the most deeply buried star-forming complexes in the Milky Way. However, since it will also be sensitive to low surface brightness emission from diffuse dust, and the key far-infrared and mm cooling lines of the ISM, CCAT will also be a superb telescope for studying nearby galaxies in exquisite detail. For the nearest systems (e.g. M83), CCAT will be able to produce diffraction-limited maps in the mid-J CO rotational lines, and the [CI] and [NII] fine-structure lines on physical scales approaching those of individual molecular clouds. For samples of luminous starburst galaxies out to 0.3-0.5, CCAT will offer unprecedented sensitivity and spatial resolution in the high-J CO lines which are critical for pinpointing X-ray dissociation regions heated by AGN. Here, we will outline the strong scientific case for using CCAT to map the cold dust, the molecular gas and the ionized and atomic interstellar medium in local galaxies.

  12. 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.

  13. 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).

  14. Space Observations of Starburst Galaxies

    NASA Technical Reports Server (NTRS)

    Heckman, Timothy M.; Leitherer, Claus

    1997-01-01

    Led by JHU postdoc Gerhardt Meurer, we completed our analysis of far-UV HST FOC images of nine nearby starbursts. We have been able to delineate the structure of the regions in which the unusually vigorous star-formation is occurring (Meurer et al 1995). At 0.1 arcsec (2 to 20 pc) resolution, the starbursts are resolved into multiple clumps and bright star clusters distributed over a region several hundred pc to a few kpc in size. This suggests that compact sites of star-formation may propagate from place to place within a larger central gas reservoir over the duration of the burst. The UV and optical properties of these clusters suggest that they may correspond to newly 'minted' globular clusters. These clusters typically produce about 10% to 50% of the far-UV light, and are preferentially located in the heart of the starburst, where the background UV surface brightness is highest. Thus, massive star cluster (globular cluster?) formation is a fundamental part of the starburst phenomenon. This confirms and generalizes the results of Whitmore et al (1993). Our starburst images are also being compared to our recent analysis of the HST FOC image of R136 in the LMC (De Marchi et al 1993). We have also extended our results on the UV photometric structure of starbursts to star-forming galaxies in the early universe (Meurer et al 1997). We show that the most actively- star-forming galaxies at all redshifts seem to have approximately the same bolometric surface-brightness, and that the high redshift galaxies may be larger and more luminous versions of local starbursts.

  15. ROSAT observations of compact groups of galaxies

    NASA Technical Reports Server (NTRS)

    Pildis, Rachel A.; Bregman, Joel N.; Evrard, August E.

    1995-01-01

    We have systematically analyzed a sample of 13 new and archival ROSAT Position Sensitive Proportional Counter (PSPC) observations of compact groups of galaxies: 12 Hickson compact groups plus the NCG 2300 group. We find that approximately two-thirds of the groups have extended X-ray emission and, in four of these, the emission is resolved into diffuse emission from gas at a temperature of kT approximately 1 keV in the group potential. All but one of the groups with extended emission have a spiral fraction of less than 50%. The baryon fraction of groups with diffuse emission is 5%-19%, similar to the values in clusters of galaxies. However, with a single exception (HCG 62), the gas-to-stellar mass ratio in our groups has a median value near 5%, somewhat greater than the values for individual early-type galaxies and two orders of magnitude than in clusters of galaxies. The X-ray luminosities of individual group galaxies are comparable to those of similar field galaxies, although the L(sub X)-L(sub B) relation for early-type galaxies may be flatter in compact groups than in the field.

  16. AMOS Galaxy 15 Satellite Observations and Analysis

    NASA Astrophysics Data System (ADS)

    Hall, D.

    2011-09-01

    In early April 2010, the Galaxy 15 geosynchronous satellite experienced an on-orbit anomaly. Even though the satellite's transmitters and articulating solar panel were still functioning, ground controllers lost the ability to command and maneuver the satellite. With its orbital position no longer maintained, Galaxy 15 began to drift eastward. This forced several other satellites to make collision avoidance maneuvers during the following months. Soon after the initial anomaly, Galaxy 15's operators predicted that the satellite’s reaction wheels would eventually become saturated, causing a loss of both spacecraft attitude and proper sunward orientation of the solar panels. This "off-pointing" event finally occurred in late December, ultimately leading to a depletion of Galaxy 15's batteries. This near-death experience had a fortunate side effect, however, in that it forced the satellite’s command unit to reboot and once again be able to both receive and execute ground commands. The satellite operators have since recovered control of the satellite. AMOS conducted non-resolved photometric observations of Galaxy 15 before, during and after these events. Similar observations were conducted of Galaxy 12, the nearly-identical replacement satellite. This presentation presents and discusses these temporal brightness signatures in detail, comparing the changing patterns in the observations to the known sequence of events.

  17. ROSAT observations of Coma Cluster galaxies

    NASA Technical Reports Server (NTRS)

    Dow, K. L.; White, S. D. M.

    1995-01-01

    The approximately 86 ks ROSAT Position Sensitive Proportional Counter (PSPC) image of the Coma Cluster is deeper than any previous X-ray observation of a galaxy cluster. We search for X-ray emission from 35 individual galaxies in a magnitude-limited sample, all of which lie within 20 arcmins of the optical axis in at least one of the four Coma pointings. We detect seven galaxies in the 0.4-2.4 keV band at a significance level exceeding 3 sigma, and a further four at above 2 sigma. Although we can set only upper limits on the individual flux from each of the other galaxies, we are able to measure their mean flux by stacking the observations. The X-ray luminosities of the seven detections range from 6.2 x 10(exp 40) to 1.5 x 10(exp 42) ergs/s (0.4-2.4 keV for H(sub 0) = 50 km/s/Mpc). For galaxies with a blue absolute magnitude of about -21 we find a mean X-ray luminosity of 1.3 x 10(exp 40) ergs/s. The ratio of X-ray to optical luminosity is substantially smaller for such subjects than for the brightest galaxies in the cluster. The X-ray luminosities of the four brightest galaxies are ill-defined, however, because of ambiguity in distinguishing galaxy emission from cluster emission. Each object appears to be related to significant structure in the diffuse intracluster medium. We also investigate emission in the softer 0.2-0.4 keV band where detections are less significant because of the higher background, and we discuss the properties of a number of interesting individual sources. The X-ray luminosities of the Coma galaxies are similar to those of galaxies in the Virgo Cluster and in other regions with relatively low galaxy density. We conclude that large-scale environmental effects do not significantly enhance or suppress the average X-ray emission from galaxies, but that individual objects vary in luminosity substantially in a way which may depend on the detailed history of their environment.

  18. ROSAT observations of Coma Cluster galaxies

    NASA Technical Reports Server (NTRS)

    Dow, K. L.; White, S. D. M.

    1995-01-01

    The approximately 86 ks ROSAT Position Sensitive Proportional Counter (PSPC) image of the Coma Cluster is deeper than any previous X-ray observation of a galaxy cluster. We search for X-ray emission from 35 individual galaxies in a magnitude-limited sample, all of which lie within 20 arcmins of the optical axis in at least one of the four Coma pointings. We detect seven galaxies in the 0.4-2.4 keV band at a significance level exceeding 3 sigma, and a further four at above 2 sigma. Although we can set only upper limits on the individual flux from each of the other galaxies, we are able to measure their mean flux by stacking the observations. The X-ray luminosities of the seven detections range from 6.2 x 10(exp 40) to 1.5 x 10(exp 42) ergs/s (0.4-2.4 keV for H(sub 0) = 50 km/s/Mpc). For galaxies with a blue absolute magnitude of about -21 we find a mean X-ray luminosity of 1.3 x 10(exp 40) ergs/s. The ratio of X-ray to optical luminosity is substantially smaller for such subjects than for the brightest galaxies in the cluster. The X-ray luminosities of the four brightest galaxies are ill-defined, however, because of ambiguity in distinguishing galaxy emission from cluster emission. Each object appears to be related to significant structure in the diffuse intracluster medium. We also investigate emission in the softer 0.2-0.4 keV band where detections are less significant because of the higher background, and we discuss the properties of a number of interesting individual sources. The X-ray luminosities of the Coma galaxies are similar to those of galaxies in the Virgo Cluster and in other regions with relatively low galaxy density. We conclude that large-scale environmental effects do not significantly enhance or suppress the average X-ray emission from galaxies, but that individual objects vary in luminosity substantially in a way which may depend on the detailed history of their environment.

  19. UV Observations of Seyfert Galaxies

    NASA Astrophysics Data System (ADS)

    Boggess, Albert

    We propose to obtain high-quality, broadened (equivalent to trailed) spectra for 9 Type I and 2 Type 2 Seyfert galaxies. Only broadened spectra have sufficient signal-to-noise ratios to allow detailed fitting of line profiles needed to investigate both the kinematics and dynamics of the emitting regions and their stratification. These spectra will also allow more accurate measurements of weak spectral features, such as: OI 1304 and He II 1640, needed to estimate reddening; N IV] 1486, O III] 1663 and N III] 1749, for abundance analyses; absorption lines such as Si IV l400 and C IV 1550, for estimating the covering factor of the broad line region (BLR); and Galactic halo absorption lines of Si II 1260, C II 1335 and Fe II 1608. There are broad features superposed on the spectrum of Seyfert galaxies: the 2200A dust absorption feature, the emission hump at 3200A and several other unidentified bumps and wiggles. Their detection, measurement and quantitative study also require spectra recorded with high signal-to-noise ratios. X-ray spectra are already available for all 9 Type 1 Seyferts, and these data will be combined with our UV continua to estimate the amounts of available ionizing radiation. We also plan to measure the fluxes of the prominent emission lines: L-alpha, SI IV 1400, C IV 1550, C III] 1900 and Mg II 2800, to extend our investigation of the L-alpha/H-beta ratio and to provide a homogeneous set of high quality data to allow the evaluation of models for individual objects instead of, as in the past, for an assumed "typical" Seyfert or quasar.

  20. Ultraviolet Imaging Telescope (UIT) observations of galaxies

    NASA Technical Reports Server (NTRS)

    Neff, S. G.

    1993-01-01

    Ultraviolet images of several galaxies were obtained during the ASTRO-1 shuttle mission in December, 1990. The images have a FWHM angular resolution of approximately 3 arcsecond and are of circular fields approximately 40 arcminutes in diameter. Most galaxies were observed in at least two and sometimes as many as four broad bands. A very few fields were observed with narrower band filters. The most basic result of these observations is that most systems look dramatically different in the UV from their well-known optical appearances. Preliminary results of these studies will be presented. Information will be available on fields observed by the UTI during the ASTRO 1 mission; when that data becomes public it can be obtained from the NSSDC. The ASTRO observatory is expected to fly again in 1994 with approximately half of the observing time from that mission devoted to guest observers. The Ultraviolet Imaging telescope is extremely well suited for galaxy studies, and the UIT term is interested in encouraging a wide range of scientific studies by guest observers. Ultraviolet Imaging telescope is extremely well suited for galaxy studies, and the UIT team is interested in encouraging a wide range of scientific studies by guest observers.

  1. 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.

  2. Multi-waveband observations of colliding galaxies

    NASA Astrophysics Data System (ADS)

    Appleton, P. N.; Robson, E. I.; Schombert, James M.

    1990-11-01

    Colliding galaxies represent a major challenge to both theorists and observers because of the large variety of phenomena which are expected to come into play during the interaction. Strong gravitational fluctuations may drive non-linear waves and instabilities throughout the stars and gas leading to enhanced star formation, nuclear activity and ultimately a mixing of the morphological components of the original galaxies. One relatively uncomplicated class of colliding galaxy where stellar waves play an important role in star formation are ring galaxies. Ring galaxies are probably formed when a companion galaxy passes through the center of a disk system driving circular waves through the disk (Lynds and Toomre 1976, Toomre 1978, Struck-Marcell 1990). Off-center collisions can generate non-circular waves and can be loosely described as banana-shaped although they may exhibit more complex forms as the waves expand into the disk. The propagation of such stellar and gaseous waves through the disk leads to enhanced star formation (e.g., Appleton and Struck-Marcell 1987a; Jeske 1986) and provides a unique probe of the response of the interstellar medium (ISM) to a propagating wave (see Appleton and Struck-Marcell 1987b). Here, the authors report results for 3 systems; the irregular ring Arp 143 (=VV 117); Wakamatsu's Seyfert ring (A0959-755; see Wakamatsu and Nishida 1987) and the brighter member of the pair of ring galaxies comprising of AM 1358-221. The most complete multi-wavelength data is for Arp 143. Optical charge coupled device (CCD) observations made with the 60 inch Palomar telescope at BV and r band, near-IR images at J (1.25 microns), H (1.65 microns) and k (2.2 microns) bands from the infrared camera (IRCAM) InSb array camera on the 3.8m United Kingdon Infrared Telescope (UKIRT) telescope and very large array (VLA) observations at 20cm in both the neutral hydrogen line and radio continuum are described. The observations of Wakamatsu's ring and AM 1358 were

  3. Multi-waveband observations of colliding galaxies

    NASA Technical Reports Server (NTRS)

    Appleton, P. N.; Robson, E. I.; Schombert, James M.

    1990-01-01

    Colliding galaxies represent a major challenge to both theorists and observers because of the large variety of phenomena which are expected to come into play during the interaction. Strong gravitational fluctuations may drive non-linear waves and instabilities throughout the stars and gas leading to enhanced star formation, nuclear activity and ultimately a mixing of the morphological components of the original galaxies. One relatively uncomplicated class of colliding galaxy where stellar waves play an important role in star formation are ring galaxies. Ring galaxies are probably formed when a companion galaxy passes through the center of a disk system driving circular waves through the disk (Lynds and Toomre 1976, Toomre 1978, Struck-Marcell 1990). Off-center collisions can generate non-circular waves and can be loosely described as banana-shaped although they may exhibit more complex forms as the waves expand into the disk. The propagation of such stellar and gaseous waves through the disk leads to enhanced star formation (e.g., Appleton and Struck-Marcell 1987a; Jeske 1986) and provides a unique probe of the response of the interstellar medium (ISM) to a propagating wave (see Appleton and Struck-Marcell 1987b). Here, the authors report results for 3 systems; the irregular ring Arp 143 (=VV 117); Wakamatsu's Seyfert ring (A0959-755; see Wakamatsu and Nishida 1987) and the brighter member of the pair of ring galaxies comprising of AM 1358-221. The most complete multi-wavelength data is for Arp 143. Optical charge coupled device (CCD) observations made with the 60 inch Palomar telescope at BV and r band, near-IR images at J (1.25 microns), H (1.65 microns) and k (2.2 microns) bands from the infrared camera (IRCAM) InSb array camera on the 3.8m United Kingdon Infrared Telescope (UKIRT) telescope and very large array (VLA) observations at 20cm in both the neutral hydrogen line and radio continuum are described. The observations of Wakamatsu's ring and AM 1358 were

  4. ROSAT observations of Several Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Cui, Wei

    1994-01-01

    We have made observations of several nearby face-on normal spiral galaxies with the ROSAT PSPC to study their 01-2 0 keV diffuse X-ray emission. The cleaned X-ray images of NGC3184, M101, NGC4395, NGC4736 and NGC5055 in the 1/4, 3/4 and 1.5 keV energy bands are presented along with a detailed discussion of how to identify and model known types of non-cosmic X-ray background. Unresolved X-ray emission in the 0.1-2.0 keV range is detected in all the observed galaxies, bright at the center and getting fainter toward the outer edges. It is a combination of diffuse emission and contribution from un-resolved point sources in these galaxies, so represents an upper limit to the diffuse X-ray emission. The derived upper limits on the diffuse emission can be interpreted in terms of upper limits to average emission measure for a putative unabsorbed halo emission, or alternatively as limits on the filling factors of 106 K hot bubbles, similar to the one surrounding the Sun, in the disks of these galaxies. They can also be used to derive limits to the total energy radiated by hot gas as a function of its temperature for various assumed absorbing geometries. Another exciting possibility is to measure shadows of the 1/4 keV extragalactic X-ray background cast by the external galaxies, which then allow us to determine useful limits on it The absorption features observed at the outer edges of some of the galaxies are direct evidence for absorption of this background by matter in there galaxies, and we have derived a 96% confidence lower limit of 32 keV cm-2 s-l sr-l keV-l. This lower limit can be compared directly with the best 95% confidence upper limit derived from observations of the Small Magellanic Cloud, which is 45 keV cm-2 s-l , sr-l keV-l The e lower and upper limits are less than a factor of two apart, and bend to provide a reasonable measurement of the actual value of the 1/4 keV extragalactic X-ray intensity

  5. Observing the epoch of galaxy formation

    PubMed Central

    Steidel, Charles C.

    1999-01-01

    Significant observational progress in addressing the question of the origin and early evolution of galaxies has been made in the past few years, allowing for direct comparison of the epoch when most of the stars in the universe were forming to prevailing theoretical models. There is currently broad consistency between theoretical expectations and the observations, but rapid improvement in the data will provide much more critical tests of theory in the coming years. PMID:10200244

  6. VLBI observations of galaxies at high redshift

    NASA Astrophysics Data System (ADS)

    Schilizzi, R. T.; Gurvits, L. I.; Miley, G. K.; Bremer, M. A. R.; Röttgering, H. J. A.; Nan, R.; Chambers, K. C.; van Breugel, W. J. M.

    Subsets of fifteen high redshift radio galaxies have been observed with VLBI arrays at 327 MHz, 1.66 GHz or 5 GHz. Here we present results of VLBI imaging of four high redshift radio galaxies, three at 327 MHz and one at 1.66 GHz. Results so far show that 1) compact 1 kpc hotspots dominate the VLA components, 2) the magnetic field strengths in the hotspots are an order of magnitude higher than in Cygnus A, 3) the estimated ages of the sources are considerably longer than the radiative lifetimes of electrons in the hotspots, implying energy resupply, and 4) the ratios of overall size to hotspot size are consistent with the correlations found by Hardcastle et al (1998) for FR II radio galaxies and Snellen et al (1998) for GPS and CSS radio galaxies. We also investigate the possibility that the misalignment of the components to the southwest in 4C41.17 may be caused by deflection of the jet by an interstellar cloud of mass ~ 108 solar masses, possibly a proto globular cluster.

  7. Models Constraints from Observations of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Riffel, R.; Pastoriza, M. G.; Rodríguez-Ardila, A.; Dametto, N. Z.; Ruschel-Dutra, D.; Riffel, R. A.; Storchi-Bergmann, T.; Martins, L. P.; Mason, R.; Ho, L. C.; Palomar XD Team

    2015-08-01

    Studying the unresolved stellar content of galaxies generally involves disentangling the various components contributing to the spectral energy distribution (SED), and fitting a combination of simple stellar populations (SSPs) to derive information about age, metallicity, and star formation history. In the near-infrared (NIR, 0.85-2.5 μm), the thermally pulsing asymptotic giant branch (TP-AGB) phase - the last stage of the evolution of intermediate-mass (M ≲ 6 M⊙) stars - is a particularly important component of the SSP models. These stars can dominate the emission of stellar populations with ages ˜ 0.2-2 Gyr, being responsible for roughly half of the luminosity in the K band. In addition, when trying to describe the continuum observed in active galactic nuclei, the signatures of the central engine and from the dusty torus cannot be ignored. Over the past several years we have developed a method to disentangle these three components. Our synthesis shows significant differences between Seyfert 1 (Sy 1) and Seyfert 2 (Sy 2) galaxies. The central few hundred parsecs of our galaxy sample contain a substantial fraction of intermediate-age populations with a mean metallicity near solar. Two-dimensional mapping of the near-infrared stellar population of the nuclear region of active galaxies suggests that there is a spatial correlation between the intermediate-age stellar population and a partial ring of low stellar velocity dispersion (σ*). Such an age is consistent with a scenario in which the origin of the low-σ* rings is a past event which triggered an inflow of gas and formed stars which still keep the colder kinematics of the gas from which they have formed. We also discuss the fingerprints of features attributed to TP-AGB stars in the spectra of the nuclear regions of nearby galaxies.

  8. Galaxy simulations: Kinematics and mock observations

    NASA Astrophysics Data System (ADS)

    Moody, Christopher E.

    2013-08-01

    There are six topics to my thesis, which are: (1) slow rotator production in varied simulation schemes and kinematically decoupled cores and twists in those simulations, (2) the change in number of clumps in radiation pressure and no-radiation pressure simulations, (3) Sunrise experiments and failures including UVJ color-color dust experiments and UVbeta slopes, (4) the Sunrise image pipeline and algorithms. Cosmological simulations of have typically produced too many stars at early times. We find that the additional radiation pressure (RP) feedback suppresses star formation globally by a factor of ~ 3. Despite this reduction, the simulation still overproduces stars by a factor of ~ 2 with respect to the predictions provided by abundance matching methods. In simulations with RP the number of clumps falls dramatically. However, only clumps with masses Mclump/Mdisk ≤ 8% are impacted by the inclusion of RP, and clump counts above this range are comparable. Above this mass, the difference between and RP and no-RP contrast ratios diminishes. If we restrict our selection to galaxies hosting at least a single clump above this mass range then clump numbers, contrast ratios, survival fractions and total clump masses show little discrepancy between RP and no-RP simulations. By creating mock Hubble Space Telescope observations we find that the number of clumps is slightly reduced in simulations with RP. We demonstrate that clumps found in any single gas, stellar, or mock observation image are not necessarily clumps found in another map, and that there are few clumps common to multiple maps. New kinematic observations from ATLAS3D have highlighted the need to understand the evolutionary mechanism leading to a spectrum of fast-rotator and slow-rotators in early-type galaxies. We address the formation of slow and fast rotators through a series of controlled, comprehensive hydrodynamic simulations sampling idealized galaxy merger formation scenarios constructed from model

  9. IUE observations of Fe 2 galaxies

    NASA Technical Reports Server (NTRS)

    Penston, M. V.; Snijders, M. A. J.; Boksenberg, A.; Haskell, J. D. J.; Fosbury, R. A. E.

    1981-01-01

    Repeated observations of the Seyfert 1 galaxies I Zw 1 and II Zw 136, which have very strong Fe II emission lines in the optical region, were made at low resolution with the IUE Satellite. The ultraviolet spectra are very similar: both are variable and show broad emission features of Fe II (especially the UV multiplets 1, 33, 60, 62, and 63) as well as the emission lines usually strong in Seyferts and quasars. The data strongly support the hypothesis that the optical Fe II emission lines are primarily due to collisional excitation and that resonance fluorescence makes only a minor contribution to the excitation of these lines.

  10. Multi-Wavelength Observations of Nearby Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Janice

    2015-08-01

    Do cycles of violent, intense, but short-lived bursts constitute a significant mode of global star formation in present-day galaxies? Such events can have a profound effect on galaxies, particularly those with shallow potential wells, and observational measures of their prevalence inform our understanding of a wide range of issues in galaxy evolution. I will highlight what we have learned about starbursts from multi-wavelength observations of galaxies in the local volume on both galactic and smaller scales, and explore how connections with the study of the deaths of massive stars may further our understanding of open issues in galaxy evolution.

  11. Radio observations of nearby moderately luminous IRAS galaxies.

    NASA Astrophysics Data System (ADS)

    Li, Yongsheng; Su, Bumei

    1999-05-01

    Six nearby moderately luminous IRAS galaxies have been observed at two wavelength by using the Australian AT. Among them, radio emissions have been detected for two galaxies, i.e. IRAS 20272-4738 and IRAS 23156-4238, and their radio parameters, like radio fluxes, peak positions, source sizes and spectral indices, are obtained. The radio sources are confirmed with infrared, radio and optical observations. Some characteristics of the radio emissions of these galaxies are discussed with previous observational data.

  12. 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.

  13. Millimeter and submillimeter observations of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Knapp, G. R.; Patten, Brian M.

    1991-01-01

    Radio galaxies are often observed to be strong long wavelength infrared sources. Twenty-six radio galaxies with strong compact cores were observed at wavelengths near 1 mm with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The detections and upper limits establish the presence of excess infrared emission for almost all of the galaxies in the sample. The exceptions are the BL Lac objects, which have smooth continuous spectra from radio to infrared wavelengths. The spectral energy distributions of the infrared emission from the radio galaxies favor a thermal origin due to emission from cool interstellar dust. The amounts of dust inferred to be present approach those observed in large spirals.

  14. AO Observations of Three Powerful Radio Galaxies

    SciTech Connect

    de Vries, W; van Bruegel, W; Quirrenbach, A

    2002-08-01

    The host galaxies of powerful radio sources are ideal laboratories to study active galactic nuclei (AGN). The galaxies themselves are among the most massive systems in the universe, and are believed to harbor supermassive black holes (SMBH). If large galaxies are formed in a hierarchical way by multiple merger events, radio galaxies at low redshift represent the end-products of this process. However, it is not clear why some of these massive ellipticals have associated radio emission, while others do not. Both are thought to contain SMBHs, with masses proportional to the total luminous mass in the bulge. It either implies every SMBH has recurrent radio-loud phases, and the radio-quiet galaxies happen to be in the ''low'' state, or that the radio galaxy nuclei are physically different from radio-quiet ones, i.e. by having a more massive SMBH for a given bulge mass. Here we present the first results from our adaptive optics imaging and spectroscopy pilot program on three nearby powerful radio galaxies. Initiating a larger, more systematic AO survey of radio galaxies (preferentially with Laser Guide Star equipped AO systems) has the potential of furthering our understanding of the physical properties of radio sources, their triggering, and their subsequent evolution.

  15. Observational Searches for Star-Forming Galaxies at z > 6

    NASA Astrophysics Data System (ADS)

    Finkelstein, Steven L.

    2016-08-01

    Although the universe at redshifts greater than six represents only the first one billion years (< 10%) of cosmic time, the dense nature of the early universe led to vigorous galaxy formation and evolution activity which we are only now starting to piece together. Technological improvements have, over only the past decade, allowed large samples of galaxies at such high redshifts to be collected, providing a glimpse into the epoch of formation of the first stars and galaxies. A wide variety of observational techniques have led to the discovery of thousands of galaxy candidates at z > 6, with spectroscopically confirmed galaxies out to nearly z = 9. Using these large samples, we have begun to gain a physical insight into the processes inherent in galaxy evolution at early times. In this review, I will discuss (i) the selection techniques for finding distant galaxies, including a summary of previous and ongoing ground and space-based searches, and spectroscopic follow-up efforts, (ii) insights into galaxy evolution gleaned from measures such as the rest-frame ultraviolet luminosity function, the stellar mass function, and galaxy star-formation rates, and (iii) the effect of galaxies on their surrounding environment, including the chemical enrichment of the universe, and the reionisation of the intergalactic medium. Finally, I conclude with prospects for future observational study of the distant universe, using a bevy of new state-of-the-art facilities coming online over the next decade and beyond.

  16. Confronting semi-analytic galaxy models with galaxy-matter correlations observed by CFHTLenS

    NASA Astrophysics Data System (ADS)

    Saghiha, Hananeh; Simon, Patrick; Schneider, Peter; Hilbert, Stefan

    2017-05-01

    Testing predictions of semi-analytic models of galaxy evolution against observations helps to understand the complex processes that shape galaxies. We compare predictions from the Garching and Durham models implemented on the Millennium Simulation (MS) with observations of galaxy-galaxy lensing (GGL) and galaxy-galaxy-galaxy lensing (G3L) for various galaxy samples with stellar masses in the range 0.5 ≤ M∗/ 1010M⊙ < 32 and photometric redshifts in the range 0.2 ≤ z < 0.6 in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). We find that the predicted GGL and G3L signals are in qualitative agreement with CFHTLenS data. Quantitatively, the models succeed in reproducing the observed signals in the highest stellar mass bin, 16 ≤ M∗/ 1010M⊙ < 32, but show different degrees of tension for the other stellar mass samples. The Durham models are strongly excluded by the observations at the 95% confidence level because they largely over-predict the amplitudes of the GGL and G3L signals, probably because they predict too many satellite galaxies in massive halos.

  17. HI--line Observations of Low Surface Brightness Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Thomas, D. L.; Taylor, C. L.; Brinks, E.; Skillman, E. D.

    1995-12-01

    We present HI--line observations of low--surface brightness (LSB) dwarf galaxies to survey their nearby environment (r <= 100 kpc) for HI bright companions. It is possible that star formation histories in dwarf galaxies can be strongly affected by interactions with nearby companions. If massive star formation can be triggered by galaxy--galaxy interactions, then the absence of such interactions likely explains the lack of star formation in LSB dwarf galaxies relative to their high surface brightness counterparts (HII galaxies). Taylor et al. (1995, ApJS, 99, 427) surveyed a sample of HII galaxies and found that 60% of the sample had nearby HI companions. In our sample of 18 LSB galaxies, we found that only 22% had companions detectable in HI. Furthermore, we find that the peak column densities for the LSB sample are all below {10(21) } HI atoms cm(-2) . This is below the empirically established level needed for star formation to occur in dwarf galaxies as discussed by Skillman (1987, in Star Formation in Galaxies, ed. C.J. Lonsdale Persson (NASA Conf. Pub. CP--2466), p.263), Kennicutt (1989, ApJ, 344, 685), van der Hulst et al. (1993, AJ, 106, 548), and Taylor et al. (1994, AJ, 107, 971).

  18. Comparing Simulations and Observations of Reionization-Epoch Galaxies

    NASA Astrophysics Data System (ADS)

    Dave, Romeel; Finlator, Kristian

    2006-05-01

    We propose to test and constrain models of early galaxy formation through comparisons with observations of reionization-epoch (z>6) galaxies observed using Spitzer. The goals are to (1) Make predictions for z>6 objects using state-of-the-art cosmological hydrodynamic simulations of galaxy formation tailored to study the reionization epoch; (2) Develop a publicly-available tool called SPOC designed to obtain detailed constraints on physical properties of observed galaxies through comparisons with simulated galaxy catalogs; and (3) Use SPOC to test and constrain models of galaxy formation through comparisons with rapidly- advancing observations in the new frontier of early universe studies. The results of this study will yield deeper insights into the galaxy formation process at these mostly unexplored epochs, with implications for understanding the formation of massive galaxies, studying the topology and evolution of IGM reionization, and designing future surveys to detect first objects. The SPOC tool will facilitate a closer connection between observations and theory by enabling the community to interpret data within the framework of current hierarchical structure formation models, in turn providing detailed tests of these models that is essential for driving the field forward.

  19. ROSAT HRI observations of six early-type galaxies

    NASA Astrophysics Data System (ADS)

    Dahlem, Michael; Stuhrmann, Norbert

    1998-04-01

    High-resolution ROSAT HRI soft X-ray observations of four E/S0 galaxies were conducted by us. The data show no signs of Seyfert activity in the X-ray regime. The central emission peaks of the four galaxies, NGC533, NGC2832, NGC4104 and NGC6329, are associated with their cooling flows. The half intensity radii of the cooling flows range from 0.8 to 3.5 kpc. We find a trend (based up to now on only five objects) of the radio power of the cores in E/S0 galaxies to increase with the size and the accretion rates of their cooling flows. In one galaxy, NGC4921, no centrally peaked extended gaseous envelope was found, which is most likely due to the fact that it is not an E/S0 galaxy, but an early-type spiral. NGC2885, the sixth galaxy in our initial sample, shows signs of X-ray emission from an AGN. It has also been classified as a Sy-1 AGN by Bade et al. (1995). However, optical imaging suggests that this galaxy is probably not an E or S0 type system either, but rather an early-type spiral galaxy. Thus, in the context of accretion rate vs. galaxy type models of low-luminosity AGNs, the presence of an X-ray luminous Sy-1 nucleus in NGC2885 is no surprise.

  20. The ergodicity bias in the observed galaxy distribution

    NASA Astrophysics Data System (ADS)

    Pan, Jun; Zhang, Pengjie

    2010-08-01

    The spatial distribution of galaxies we observed is subject to the given condition that we, human beings are sitting right in a galaxy — the Milky Way. Thus the ergodicity assumption is questionable in interpretation of the observed galaxy distribution. The resultant difference between observed statistics (volume average) and the true cosmic value (ensemble average) is termed as the ergodicity bias. We perform explicit numerical investigation of the effect for a set of galaxy survey depths and near-end distance cuts. It is found that the ergodicity bias in observed two- and three-point correlation functions in most cases is insignificant for modern analysis of samples from galaxy surveys and thus close a loophole in precision cosmology. However, it may become non-negligible in certain circumstances, such as those applications involving three-point correlation function at large scales of local galaxy samples. Thus one is reminded to take extra care in galaxy sample construction and interpretation of the statistics of the sample, especially when the characteristic redshift is low.

  1. The ergodicity bias in the observed galaxy distribution

    SciTech Connect

    Pan, Jun; Zhang, Pengjie E-mail: pjzhang@shao.ac.cn

    2010-08-01

    The spatial distribution of galaxies we observed is subject to the given condition that we, human beings are sitting right in a galaxy — the Milky Way. Thus the ergodicity assumption is questionable in interpretation of the observed galaxy distribution. The resultant difference between observed statistics (volume average) and the true cosmic value (ensemble average) is termed as the ergodicity bias. We perform explicit numerical investigation of the effect for a set of galaxy survey depths and near-end distance cuts. It is found that the ergodicity bias in observed two- and three-point correlation functions in most cases is insignificant for modern analysis of samples from galaxy surveys and thus close a loophole in precision cosmology. However, it may become non-negligible in certain circumstances, such as those applications involving three-point correlation function at large scales of local galaxy samples. Thus one is reminded to take extra care in galaxy sample construction and interpretation of the statistics of the sample, especially when the characteristic redshift is low.

  2. Multi-Wavelength Observations of Nearby Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Johnson, Kelsey; Lee, Janice

    Do cycles of violent, intense, but short-lived bursts constitute a significant mode of global starformation in present-day galaxies? Such events can have a profound effect on galaxies, particularly those with shallowpotential wells, and observational measures of their prevalence inform our understanding of a wide range of issues ingalaxy evolution. I will highlight what we have learned about starbursts from multi-wavelength observations of galaxiesin the local volume on both galactic and smaller scales, and explore how connections with the study of the deaths ofmassive stars may further our understanding of open issues in galaxy evolution.

  3. FISICA observations of the starburst galaxy, NGC 1569

    NASA Astrophysics Data System (ADS)

    Clark, D. M.; Eikenberry, S. S.; Raines, S. N.; Gruel, N.; Elston, R.; Guzman, R.; Julian, J.; Boreman, G.; Glenn, P. E.; Hull-Allen, C. G.; Hoffman, J.; Rodgers, M.; Thompson, K.; Flint, S.; Comstock, L.; Myrick, B.

    2006-06-01

    Using the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) we obtained observations of the dwarf starburst galaxy NGC 1569. We present our JH band spectra, particularly noting the existence of extended emission in Paschen β and He I.

  4. Quantitative Morphology of Galaxies Observed in the Ultraviolet

    NASA Technical Reports Server (NTRS)

    Kuchinski, L.; Madore, B.; Trewhella, M.; Freedman, W.

    2000-01-01

    We present a quantitative study of the far-ultraviolet (FUV) and optical morphology in 32 nearby galaxies and estimate the morphological k-correction expected if these objects were observed unevolved at high redshift.

  5. On the morphological dichotomies observed in the powerful radio galaxies

    NASA Astrophysics Data System (ADS)

    Miraghaei, H.; Best, P. N.

    2017-06-01

    We study environment and host galaxy properties of powerful radio galaxies with different radio morphologies from compact sources to very extended double lobed radio galaxies and with different optical spectra classified as high excitation (HERG; quasar-mode) and low excitation (LERG; jet-mode) radio galaxies. We use a complete sample of morphologically classified radio sources from [1] and perform three different analyses: i) we compare compact radio sources with the extended sources from the same class of excitation. ii) we compare HERGs with the LERGs using a combined sample of compact and extended sources. iii) we investigate the origin of different morphologies observed in the very extended powerful radio galaxies, historically classified as Fanaroff-Riley (FR) radio galaxies of type I and type II by comparing a sample of FRIs with the FRIIs from the same excitation class. We discuss the results and what causes the differences in each comparison. The role of host galaxy and the central super massive black hole, and the galaxy interactions are all investigated.

  6. Millimeter and submillimeter observations of nearby radio galaxies

    SciTech Connect

    Knapp, G.R.; Patten, B.M. Hawaii, University, Honolulu )

    1991-05-01

    Radio galaxies are often observed to be strong long wavelength infrared sources. Twenty-six radio galaxies with strong compact cores were observed at wavelengths near 1 mm with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The detections and upper limits establish the presence of excess infrared emission for almost all of the galaxies in the sample. The exceptions are the BL Lac objects, which have smooth continuous spectra from radio to infrared wavelengths. The spectral energy distributions of the infrared emission from the radio galaxies favor a thermal origin due to emission from cool interstellar dust. The amounts of dust inferred to be present approach those observed in large spirals. 55 refs.

  7. Selections from 2016: Counting Galaxies in the Observable Universe

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-12-01

    Editors note:In these last two weeks of 2016, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.The Evolution of Galaxy Number Density at z 8 and Its ImplicationsPublished October2016Main takeaway:How many galaxies are there in the observable universe? The latest estimate is approximately 2 trillion, according to a study led by Christopher Conselice (University of Nottingham, UK). The authors produced this estimate by using observations of the number of galaxies in recent deep-field surveys by Hubble and other telescopes, and then extrapolating this number to account for small and faint galaxies that we arent able to see.Why its interesting:The original Hubble Deep Field study from the mid-1990s provided the basis for our previous working estimate of the number of galaxies the universe contains, which was around 120 billion. The new estimate from Conselice and collaborators therefore suggests that there are a factor of ten more galaxies in the universe than we previously thought!What to expect from observations:Right now we only have the capability to see roughly 10% of these 2 trillion galaxies. But future observatories like the James Webb Space Telescope will be able to pick out many more distant galaxies than what weve found so far, helping us to understand how these galaxies formed in the early universe.CitationChristopher J. Conselice et al 2016 ApJ 830 83. doi:10.3847/0004-637X/830/2/83

  8. Infrared Observations of Star-Forming Dwarf Galaxies with Spitzer

    NASA Astrophysics Data System (ADS)

    Rosenberg, J. L.; Ashby, M. L. N.; Salzer, J. J.

    2004-12-01

    We present a study of the infrared properties of a sample of actively star-forming dwarf galaxies (MB >-18) drawn from the KPNO International Spectroscopic Survey. Nearby actively star-forming dwarf galaxies are possible analogs to the high redshift star-forming systems that serve as galactic building blocks in hierarchical galaxy formation scenarios. These galaxies are gas-rich, metal-poor systems undergoing bursts of star formation in the local universe. A subset of such objects from the line-flux limited objective-prism survey of Salzer et al. (2001) lie in the NOAO Bootes field, and have therefore been observed by Spitzer as part of the IRAC Shallow Survey. We use the IRAC data to measure the stellar mass in these galaxies. In addition, we examine whether these metal-poor dwarf galaxies show warm dust emission, and examine whether it traces the star formation as it does in normal disk galaxies. J. L. Rosenberg would like to acknowledge the NSF Astronomy and Astrophysics Fellowship for support of this work. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA.

  9. Constraining Cosmological Parameters with Observations of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Böhringer, Hans; Schuecker, Peter; Guzzo, Luigi; Collins, Chris A.

    Galaxy clusters are ideal probes of the large-scale structure of the Universe and for the tests of cosmological models. Based on the REFLEX redshift survey of X-ray selected clusters of galaxies we determine statistical properties of the galaxy cluster population, their spatial correlation, and the density fluctuation power spectrum of the cosmic matter distribution on large scales up to about 1 Gpc. Comparing these results with predictions of cosmological models we obtain tight constrains for the matter density parameter of the Universe, consistent with the combined results from observations of the microwave background anisotropies and distant type Ia supernovae.

  10. A statistical study of merging galaxies: Theory and observations

    NASA Technical Reports Server (NTRS)

    Chatterjee, Tapan K.

    1990-01-01

    A study of the expected frequency of merging galaxies is conducted, using the impulsive approximation. Results indicate that if we consider mergers involving galaxy pairs without halos in a single crossing time or orbital period, the expected frequency of mergers is two orders of magnitude below the observed value for the present epoch. If we consider mergers involving several orbital periods or crossing times, the expected frequency goes up by an order of magnitude. Preliminary calculation indicate that if we consider galaxy mergers between pairs with massive halos, the merger is very much hastened.

  11. Deep CCD observations of nearby dwarf galaxy candidates

    NASA Technical Reports Server (NTRS)

    Hoessel, J. G.; Saha, A.; Danielson, G. E.

    1988-01-01

    During their search for faint planetary nebulae on the Palomar Sky Survey, Ellis, Grayson, and Bond (1984) found three low-surface-brightness objects which they speculated were dwarf galaxies. Deep CCD observations of these objects indicate that one, EGB 04 27+63 is a previously uncataloged dwarf irregular galaxy which is partially resolved into stars. The other two objects appear to be faint diffuse nebulae: perhaps gaseous or reflection nebulae.

  12. Biases and systematics in the observational derivation of galaxy properties: comparing different techniques on synthetic observations of simulated galaxies

    NASA Astrophysics Data System (ADS)

    Guidi, Giovanni; Scannapieco, Cecilia; Walcher, C. Jakob

    2015-12-01

    We study the sources of biases and systematics in the derivation of galaxy properties from observational studies, focusing on stellar masses, star formation rates, gas and stellar metallicities, stellar ages, magnitudes and colours. We use hydrodynamical cosmological simulations of galaxy formation, for which the real quantities are known, and apply observational techniques to derive the observables. We also analyse biases that are relevant for a proper comparison between simulations and observations. For our study, we post-process the simulation outputs to calculate the galaxies' spectral energy distributions (SEDs) using stellar population synthesis models and also generate the fully consistent far-UV-submillimetre wavelength SEDs with the radiative transfer code SUNRISE. We compared the direct results of simulations with the observationally derived quantities obtained in various ways, and found that systematic differences in all studied galaxy properties appear, which are caused by: (1) purely observational biases, (2) the use of mass-weighted and luminosity-weighted quantities, with preferential sampling of more massive and luminous regions, (3) the different ways of constructing the template of models when a fit to the spectra is performed, and (4) variations due to different calibrations, most notably for gas metallicities and star formation rates. Our results show that large differences can appear depending on the technique used to derive galaxy properties. Understanding these differences is of primary importance both for simulators, to allow a better judgement of similarities and differences with observations, and for observers, to allow a proper interpretation of the data.

  13. International Ultraviolet Explorer observations of amorphous hot galaxies

    SciTech Connect

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

    1984-08-01

    In order to better understand the nature of star formation processes in amorphous galaxies, short wavelength International Ultraviolet Explorer (IUE) spectra of galaxies NGC 1705 and NGC 1800 were obtained. The IUE data for NGC 1705 were of excellent quality while the low signal-to-noise NGC 1800 observation was useful only as a rough guide to the ultraviolet energy distribution. It was 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. The NGC 1800 is likely to have similar properties, and blue galaxies with amorphous structures thus do not show evidence for anomalies in stellar mass distributions. The UV spectra of amorphous galaxies and a variety of other hot extragalactic stellar systems have similar characteristics, which suggests OB stellar populations often are homogeneous in their properties.

  14. International Ultraviolet Explorer observations of amorphous hot galaxies

    NASA Technical Reports Server (NTRS)

    Lamb, S. A.; Gallac gher, J. S.; Hjellming, M.; Hunter, D. A.

    1984-01-01

    In order to better understand the nature of star formation processes in amorphous galaxies, short wavelength International Ultraviolet Explorer (IUE) spectra of galaxies NGC 1705 and NGC 1800 were obtained. The IUE data for NGC 1705 were of excellent quality while the low signal-to-noise NGC 1800 observation was useful only as a rough guide to the ultraviolet energy distribution. It was 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. The NGC 1800 is likely to have similar properties, and blue galaxies with amorphous structures thus do not show evidence for anomalies in stellar mass distributions. The UV spectra of amorphous galaxies and a variety of other hot extragalactic stellar systems have similar characteristics, which suggests OB stellar populations often are homogeneous in their properties.

  15. Observation of the microlensing toward the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Shulga, V. V.; Sazhin, M. V.; Gorbatko, N. P.

    Observation of the Andromeda galaxy (M31) stars microlensed by dark bodies in the halo of our Galaxy is considered. Observations toward the Andromeda galaxy significantly increase the probability to reveal microlensing effects in comparison with MACHO and EROS procedures for observations of LMC and SMC. This is due to: greater amount of background stars (stars from M31) for which it is possible to observe the microlensing effect; greater distance to M31 (690 kps). This fact allows us to consider ALL the dark bodies in our Galaxy whereas LMC and SMC are actually situated INSIDE (55 kps) the halo of the Galaxy. The probability of microlensing effects, their characteristic times and the maximum factor of M31 star brightness amplification are estimated for different models. If the mass of a dark body in the halo of our Galaxy is of the order of 1M, it is possible to detect 5-6 microlensing events in one year. When the maximum factor of brightness amplification is 10, the characteristic time of the event is 7-10 days. If masses of dark bodies is of the order of 10-3 M it is possible detect 175-200 events per year and duration of these events is 0.2-0.3 days provided that the maximum amplification factor is 10. Procedures of real astronomical observations to search for the microlensing effect are discussed in detail. Information about observational series obtained is given. This series was obtained with the telescope AFR-1 in observatory at Mount Majdanak in 1990-1992 (total duration of the series is about 1.5 years). Processing of long observational series is being performed for the purpose of revealing microlensing effect. Preliminary results of the processing are presented.

  16. Physical and observable properties of the first galaxies

    NASA Astrophysics Data System (ADS)

    Wise, John; Simeon Barrow, Kirk Stuart; O'Shea, Brian W.; Norman, Michael L.; Xu, Hao

    2017-01-01

    The Hubble Ultra Deep Field and Frontier Fields have discovered over 1,500 galaxies at redshifts greater than 6. We present observational predictions for this high-redshift population, using the Renaissance Simulations, a suite of high-resolution cosmological simulations, that enables the correlation between key observables and the physical properties of the first galaxies in the Universe. Using a sample of over 3,000 resolved galaxies along with the formation of 10,000 massive Population III stars, we show that the luminosity function flattens above a UV magnitude of -14 but does not drop to zero even to our resolution limit of M_UV = -4. We find that dark matter halos below the atomic cooling limit (~10^8 M_sun) can form stars if they are chemically enriched, and they have similar mass-to-light ratios as local ultra-faint dwarfs. We utilize stellar population synthesis models, dust extinction using Monte Carlo methods, and photo-ionization modeling, all sourced from the simulation data, to obtain synthetic observations of the first galaxies. Using these results, we will be able to constrain the following properties of the first galaxies: (1) star formation histories and stellar populations, (2) nebular emission and dust extinction, and (3) the faint end of the luminosity function.

  17. Spectral Observations of Two Galaxies with UV Excess

    NASA Astrophysics Data System (ADS)

    Karapetyan, E. L.

    2016-09-01

    Spectral observations of two galaxies with UV-excess from Kazarian's list are reported. The spectra were obtained with the 2.6-m telescope at the Byurakan Observatory using the SCORPIO spectral camera. A grism was used to obtain spectra in the wavelength interval λλ7420-3920 Å. The spectra of Kaz 151, Kaz 153 have Sy2 features. In the spectra of the Kaz 151, and Kaz 153 galaxies absorption lines are observed along with high excitation emission lines such as HeI λ5876 Å and HeII λ4686 Å.

  18. 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.

  19. Low-Frequency Radio Observations of Galaxy Cluster Merger Shocks

    NASA Astrophysics Data System (ADS)

    van Weeren, Reinout

    2014-10-01

    In a few dozen merging galaxy clusters diffuse extended radio emission has been found, implying the presence of relativistic particles and magnetic fields in the intracluster medium. A major question is how these particles are accelerated up to such extreme energies. In this talk I will present LOFAR and JVLA radio observations of the Toothbrush galaxy cluster. The Toothbrush cluster hosts diffuse 2 Mpc extended radio emission in the form of a radio relic and halo. Our deep LOFAR and JVLA observations allow a radio spectral study to test the shock origin of the relic and underlying particle acceleration mechanisms.

  20. Structures and Components in Galaxy Clusters: Observations and Models

    NASA Astrophysics Data System (ADS)

    Bykov, A. M.; Churazov, E. M.; Ferrari, C.; Forman, W. R.; Kaastra, J. S.; Klein, U.; Markevitch, M.; de Plaa, J.

    2015-05-01

    Clusters of galaxies are the largest gravitationally bounded structures in the Universe dominated by dark matter. We review the observational appearance and physical models of plasma structures in clusters of galaxies. Bubbles of relativistic plasma which are inflated by supermassive black holes of AGNs, cooling and heating of the gas, large scale plasma shocks, cold fronts, non-thermal halos and relics are observed in clusters. These constituents are reflecting both the formation history and the dynamical properties of clusters of galaxies. We discuss X-ray spectroscopy as a tool to study the metal enrichment in clusters and fine spectroscopy of Fe X-ray lines as a powerful diagnostics of both the turbulent plasma motions and the energetics of the non-thermal electron populations. The knowledge of the complex dynamical and feedback processes is necessary to understand the energy and matter balance as well as to constrain the role of the non-thermal components of clusters.

  1. OBSERVABILITY OF DUAL ACTIVE GALACTIC NUCLEI IN MERGING GALAXIES

    SciTech Connect

    Van Wassenhove, Sandor; Volonteri, Marta; Bellovary, Jillian; Mayer, Lucio; Callegari, Simone; Dotti, Massimo

    2012-03-20

    Supermassive black holes (SMBHs) have been detected in the centers of most nearby massive galaxies. Galaxies today are not only the products of billions of years of galaxy mergers, but also billions of years of SMBH activity as active galactic nuclei (AGNs) that is connected to galaxy mergers. In this context, detection of AGN pairs should be relatively common. Observationally, however, dual AGNs are scant, being just a few percent of all AGNs. In this Letter, we investigate the triggering of AGN activity in merging galaxies via a suite of high-resolution hydrodynamical simulations. We follow the dynamics and accretion onto the SMBHs as they move from separations of tens of kiloparsecs to tens of parsecs. Our resolution, cooling, and star formation implementation produce an inhomogeneous, multi-phase interstellar medium, allowing us to accurately trace star formation and accretion onto the SMBHs. We study the impact of gas content, morphology, and mass ratio, focusing on AGN activity and dynamics across a wide range of relevant conditions. We test when the two AGNs are simultaneously detectable, for how long and at which separations. We find that strong dual AGN activity occurs during the late phases of the mergers, at small separations (<1-10 kpc) below the resolution limit of most surveys. Much of the SMBH accretion is not simultaneous, limiting the dual AGN fraction detectable through imaging and spectroscopy to a few percent, in agreement with observational samples.

  2. CHANDRA OBSERVATIONS OF THE COLLISIONAL RING GALAXY NGC 922

    SciTech Connect

    Prestwich, A. H.; Galache, J. L.; Zezas, A.; Linden, T.; Kalogera, V.; Roberts, T. P.; Kilgard, R.; Wolter, A.; Trinchieri, G.

    2012-03-10

    In this paper, we report on Chandra observations of the starburst galaxy NGC 922. NGC 922 is a drop-through ring galaxy with an expanding ring of star formation, similar in many respects to the Cartwheel galaxy. The Cartwheel galaxy is famous for hosting 12 ultraluminous X-ray sources (ULXs), most of which are in the star-forming ring. This is the largest number of ULXs seen in a single system and has led to speculation that the low metallicity of the Cartwheel (0.3 Z{sub Sun }) may optimize the conditions for ULX formation. In contrast, NGC 922 has metallicity near solar. The Chandra observations reveal a population of bright X-ray sources, including seven ULXs. The number of ULXs in NGC 922 and the Cartwheel scales with the star formation rate: we do not find any evidence for an excess of sources in the Cartwheel. Simulations of the binary population in these galaxies suggest that the ULX population in both systems is dominated by systems with strong wind accretion from supergiant donors onto direct-collapse black holes. The simulations correctly predict the ratio of the number of sources in NGC 922 and the Cartwheel. Thus, it would appear that the metallicity of the Cartwheel is not low enough to see a difference in the ULX population compared to NGC 922.

  3. Chandra Observations of the Collisional Ring Galaxy NGC 922

    NASA Astrophysics Data System (ADS)

    Prestwich, A. H.; Galache, J. L.; Linden, T.; Kalogera, V.; Zezas, A.; Roberts, T. P.; Kilgard, R.; Wolter, A.; Trinchieri, G.

    2012-03-01

    In this paper, we report on Chandra observations of the starburst galaxy NGC 922. NGC 922 is a drop-through ring galaxy with an expanding ring of star formation, similar in many respects to the Cartwheel galaxy. The Cartwheel galaxy is famous for hosting 12 ultraluminous X-ray sources (ULXs), most of which are in the star-forming ring. This is the largest number of ULXs seen in a single system and has led to speculation that the low metallicity of the Cartwheel (0.3 Z ⊙) may optimize the conditions for ULX formation. In contrast, NGC 922 has metallicity near solar. The Chandra observations reveal a population of bright X-ray sources, including seven ULXs. The number of ULXs in NGC 922 and the Cartwheel scales with the star formation rate: we do not find any evidence for an excess of sources in the Cartwheel. Simulations of the binary population in these galaxies suggest that the ULX population in both systems is dominated by systems with strong wind accretion from supergiant donors onto direct-collapse black holes. The simulations correctly predict the ratio of the number of sources in NGC 922 and the Cartwheel. Thus, it would appear that the metallicity of the Cartwheel is not low enough to see a difference in the ULX population compared to NGC 922.

  4. The Evolution of Galaxies, I-Observational Clues

    NASA Astrophysics Data System (ADS)

    Vilchez, José M.; Stasińska, Grazyna; Pérez, Enrique

    2001-12-01

    Galaxies have a history. This has become clear from recent sky surveys, which have shown that distant galaxies, formed early in the life of the Universe, differ from the nearby ones. New observational windows at ultraviolet, infrared and millimetric wavelengths (provided by ROSAT, IRAM, IUE, IRAS, ISO) have revealed that galaxies contain a wealth of components: very hot gas, atomic hydrogen, molecules, dust, dark matter.... A significant advance is expected due to new instruments (VLT, FIRST, XMM) which will allow one to explore the most distant Universe. Three Euroconferences have been planned to punctuate this new epoch in galactic research, bringing together specialists in various fields of Astronomy. The first, held in Granada (Spain) in May 2000, addressed the observational clues. The second will take place in October 2001 in St Denis de la Réunion (France) and will review the basic building blocks and small-scale processes in galaxy evolution. The third will take place in July 2002 in Kiel (Germany) and will be devoted to the overall modelling of galaxy evolution. This book contains the proceedings of the first conference. It is recommended to researchers and PhD students in Astrophysics. Link: http://www.wkap.nl/prod/b/1-4020-0001-4

  5. Spectroscopic Observations of the Star Formation Regions in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Kong, X.; Lin, L.; Li, J. R.; Zhou, X.; Zou, H.; Li, H. Y.; Chen, F. Z.; Du, W.; Fan, Z.; Mao, Y. W.; Wang, J.; Zhu, Y. N.; Zhou, Z. M.

    2014-01-01

    During the late 1990s and the first decade of the 21st century, the 8˜10 m scale ground-based telescopes are helping astronomers learn much more about how galaxies develop. The existing 2˜4 m scale telescopes become less important for astrophysical researches. To use the existing 2˜4 m scale telescopes to address important issues in cosmology and extragalactic and galactic astronomy, we have to consider very carefully which kind of things we can do, and which we can not. For this reason, the Time Allocation Committee (TAC) of the National Astronomical Observatories of China (NAOC) 2.16 m telescope decides to support some key projects since 2013. Nearby galaxies supply us with the opportunity to study galaxy dynamics and star formation on large scales, yet are close enough to reveal the details. Star formation regions in nearby galaxies provide an excellent laboratory to study the star formation processes, the evolution of massive stars, and the properties of the surrounding interstellar medium. A wealth of information can be obtained from the spectral analysis of the bright emission lines and the stellar continuum. Considering these, we proposed a long-term project ``Spectroscopic Observations of the Star Formation Regions in Nearby Galaxies'', and it becomes the key project of the NAOC 2.16 m telescope since 2013, supported with 30 dark/grey nights per year. The primary goal of this project is to observe the spectroscopy of star formation regions in 20 nearby galaxies, with the NAOC 2.16 m telescope and the Hectospec/MMT (Multiple Mirror Telescope) multifiber spectrograph by Telescope Access Program (TAP). With the spectra of a large sample of star formation regions, combining multi-wavelength data from UV to IR, we can investigate, understand, and quantify the nature of the deviation from the starbursts' IRX-β (the IR/UV ratio ``IRX'' versus the UV color ``β'') correlation. It will be important for a better understanding of the interaction of dust and

  6. Some observational tests of a minimal galaxy formation model

    NASA Astrophysics Data System (ADS)

    Cohn, J. D.

    2017-04-01

    Dark matter simulations can serve as a basis for creating galaxy histories via the galaxy-dark matter connection. Here, one such model by Becker is implemented with several variations on three different dark matter simulations. Stellar mass and star formation rates are assigned to all simulation subhaloes at all times, using subhalo mass gain to determine stellar mass gain. The observational properties of the resulting galaxy distributions are compared to each other and observations for a range of redshifts from 0 to 2. Although many of the galaxy distributions seem reasonable, there are noticeable differences as simulations, subhalo mass gain definitions or subhalo mass definitions are altered, suggesting that the model should change as these properties are varied. Agreement with observations may improve by including redshift dependence in the added-by-hand random contribution to star formation rate. There appears to be an excess of faint quiescent galaxies as well (perhaps due in part to differing definitions of quiescence). The ensemble of galaxy formation histories for these models tend to have more scatter around their average histories (for a fixed final stellar mass) than the two more predictive and elaborate semi-analytic models of Guo et al. and Henriques et al., and require more basis fluctuations (using principal component analysis) to capture 90 per cent of the scatter around their average histories. The codes to plot model predictions (in some cases alongside observational data) are publicly available to test other mock catalogues at https://github.com/jdcphysics/validation/. Information on how to use these codes is in Appendix A.

  7. Magnetism in galaxies - Observational overview and next generation radio telescopes

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    2011-06-01

    The strength and structure of cosmic magnetic fields is best studied by observations of radio continuum emission, its polarization and its Faraday rotation. Fields with a well-ordered spiral structure exist in many types of galaxies. Total field strengths in spiral arms and bars are 20-30 μG and dynamically important. Strong fields in central regions can drive gas inflows towards an active nucleus. The strongest regular fields (10-15 μG) are found in interarm regions, sometimes forming ``magnetic spiral arms'' between the optical arms. The typical degree of polarization is a few % in spiral arms, but high (up to 50%) in interarm regions. The detailed field structures suggest interaction with gas flows. Faraday rotation measures of the polarization vectors reveals large-scale patterns in several spiral galaxies which are regarded as signatures of large-scale (coherent) fields generated by dynamos. - Polarization observations with the forthcoming large radio telescopes will open a new era in the observation of magnetic fields and should help to understand their origin. Low-frequency radio synchrotron emission traces low-energy cosmic ray electrons which can propagate further away from their origin. LOFAR (30-240 MHz) will allow us to map the structure of weak magnetic fields in the outer regions and halos of galaxies, in galaxy clusters and in the Milky Way. Polarization at higher frequencies (1-10 GHz), to be observed with the EVLA, MeerKAT, APERTIF and the SKA, will trace magnetic fields in the disks and central regions of galaxies in unprecedented detail. All-sky surveys of Faraday rotation measures towards a dense grid of polarized background sources with ASKAP and the SKA are dedicated to measure magnetic fields in distant intervening galaxies and clusters, and will be used to model the overall structure and strength of the magnetic field in the Milky Way.

  8. The Arecibo Galaxy Environment Survey (AGES) - HI Observations of the Isolated Galaxy UGC 2082

    NASA Astrophysics Data System (ADS)

    Taber, Timothy M.; Minchin, R.; AGES

    2011-01-01

    The Arecibo Galactic Environment Survey (AGES) is a 21-cm neutral hydrogen survey utilizing the Arecibo L-band Feed Array on the 305-m radio telescope at Arecibo Observatory. AGES uses a bandwidth of 100 MHz, allowing the detection of galaxies out to heliocentric velocities of 20000 km/s. Many different galaxy environments are being examined in AGES including isolated galaxies, where one objective is to find possible low surface brightness companion galaxies. The field surrounding isolated galaxy UGC 2082 was examined for this project, and 90 possible sources were found in the data cube. Of these, 46 are regarded as definite detections; the others will be re-observed with the L-Band Wide receiver at Arecibo Observatory in order to confirm their reality. Using optical data from the Sloan Digital Sky Survey and SuperCOSMOS the most likely optical counterparts have been chosen for each 21-cm source. 24 of the detected HI sources have no clear optical counterpart, many of these being dubious detections. A very faint companion galaxy to UGC 2082 was found at a heliocentric velocity of 590 km/s. This source is located approximately 66.5 arcminutes north of UGC 2082 (which has a measured heliocentric velocity of 713 km/s). Using the published Tully-Fisher distance to UGC 2082 of 14.7 Mpc, the projected physical separation of the two galaxies is 284.4 kpc. Another objective of AGES is to gain insight on the HI mass function and the large-scale structure of the universe. All of the detected sources in this data were plotted by right ascension or declination versus heliocentric velocity. These plots showed noticeable structure at both 5500 km/s and 11000 km/s. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation.

  9. IUE observations of luminous blue star associations in irregular galaxies

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    Two regions of recent star formation in blue irregular galaxies were observed with the IUE in the short wavelength, low dispersion mode. The spectra indicate that the massive star content is similar in these regions and is best fit by massive stars formed in a burst and now approximately 2.5 to 3.0 million years old.

  10. Radio-continuum observations of Sersic-Pastoriza galaxies

    NASA Astrophysics Data System (ADS)

    Yates, G. J.; Saikia, D. J.; Pedlar, A.; Axon, D. J.

    1989-07-01

    Preliminary results of radio continuum observations of selected Sersic-Pastoriza galaxies are presented. Subjects reported are their radio properties at 6 and 20 cm, estimates of linear polarization and spectral indices and a discussion of possible relationships between nuclear morphology and radio luminosity.

  11. HERSCHEL SPECTROSCOPIC OBSERVATIONS OF LITTLE THINGS DWARF GALAXIES

    SciTech Connect

    Cigan, Phil; Young, Lisa; Cormier, Diane; Lebouteiller, Vianney; Madden, Suzanne; Brinks, Elias; Elmegreen, Bruce; Schruba, Andreas; Heesen, Volker; Collaboration: LITTLE THINGS Team

    2016-01-15

    We present far-infrared (FIR) spectral line observations of five galaxies from the Little Things sample: DDO 69, DDO 70, DDO 75, DDO 155, and WLM. While most studies of dwarfs focus on bright systems or starbursts due to observational constraints, our data extend the observed parameter space into the regime of low surface brightness dwarf galaxies with low metallicities and moderate star formation rates. Our targets were observed with Herschel at the [C ii] 158 μm, [O i] 63 μm, [O iii] 88 μm, and [N ii] 122 μm emission lines using the PACS Spectrometer. These high-resolution maps allow us for the first time to study the FIR properties of these systems on the scales of larger star-forming complexes. The spatial resolution in our maps, in combination with star formation tracers, allows us to identify separate photodissociation regions (PDRs) in some of the regions we observed. Our systems have widespread [C ii] emission that is bright relative to continuum, averaging near 0.5% of the total infrared (TIR) budget—higher than in solar-metallicity galaxies of other types. [N ii] is weak, suggesting that the [C ii] emission in our galaxies comes mostly from PDRs instead of the diffuse ionized interstellar medium (ISM). These systems exhibit efficient cooling at low dust temperatures, as shown by ([O i]+[C ii])/TIR in relation to 60 μm/100 μm, and low [O i]/[C ii] ratios which indicate that [C ii] is the dominant coolant of the ISM. We observe [O iii]/[C ii] ratios in our galaxies that are lower than those published for other dwarfs, but similar to levels noted in spirals.

  12. Observational hints of radial migration in disc galaxies from CALIFA

    NASA Astrophysics Data System (ADS)

    Ruiz-Lara, T.; Pérez, I.; Florido, E.; Sánchez-Blázquez, P.; Méndez-Abreu, J.; Sánchez-Menguiano, L.; Sánchez, S. F.; Lyubenova, M.; Falcón-Barroso, J.; van de Ven, G.; Marino, R. A.; de Lorenzo-Cáceres, A.; Catalán-Torrecilla, C.; Costantin, L.; Bland-Hawthorn, J.; Galbany, L.; García-Benito, R.; Husemann, B.; Kehrig, C.; Márquez, I.; Mast, D.; Walcher, C. J.; Zibetti, S.; Ziegler, B.; Califa Team

    2017-07-01

    , in light of these results we cannot further quantify the importance of radial migration in shaping spiral galaxies, and other processes, such as recent star formation or satellite accretion, might play a role. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/604/A4

  13. New Galaxies From Old? VLA Observations Strengthen the Case

    NASA Astrophysics Data System (ADS)

    1996-01-01

    Astronomers using the Very Large Array (VLA) radio telescope have found some of the best evidence to date that small, new galaxies can form from material pulled out of older galaxies. The new observations seriously weaken models of galactic evolution that attempt to explain the various types of galaxies seen in the universe as the result of different, but independent, processes. Steve Gottesman of the University of Florida in Gainesville, Tim Hawarden of the Joint Astronomy Center in Hilo, Hawaii, Caroline Simpson of Florida International University in Miami and Benjamin Malphrus of Morehead State University in Morehead, Kentucky, presented the results today to the American Astronomical Society meeting in San Antonio, TX. The astronomers used the VLA, a facility of the National Science Foundation, to study a galaxy system some 180 million light-years distant in the constellation Centaurus called NGC 5291. NGC 5291 is a peculiar spiral galaxy that appears to be interacting with a nearby object called the Seashell. The VLA observations show a large, elongated cloud of neutral hydrogen gas surrounding NGC 5291 and the Seashell. Within that gas cloud there are several concentrations. These mostly coincide with faint "knots" which were first seen on optical photographs taken twenty years ago with the UK Schmidt Telescope in Australia for the ESO/SRC Southern Sky Survey. In a detailed study at that time, using the 4-meter Anglo-Australian Telescope (AAT) and the 65m Parkes radio telescope, the knots were shown to be giant star-forming regions and the system was found to contain an extremely large cloud of gas. Though details were lacking then, astronomers suggested that the larger knots would turn out to be galaxies either in the process of formation or recently formed from the material of the parent system. Subsequently, similar suggestions were made about concentrations of material in the "tidal tails" ejected by galactic collisions elsewhere in the sky, but it was not

  14. Radio and Submillimeter Continuum Observations of High-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Hao; Barger, Amy J.; Cowie, Lennox L.; Chen, Chian-Chou; Williams, Jonathan P.; Owen, Frazer N.

    2013-03-01

    Observing galaxies in the radio and submillimeter continuum has the advantage of being unaffected by dust extinction, which is a major drawback of studying galaxy evolution using optical data. Submillimeter single-dish surveys have made tremendous progress in understanding the high-redshift dusty population, but the low angular resolution of single-dish telescopes has also hampered these studies. Our recent JCMT and SMA imaging of high-redshift submillimeter sources revealed z > 4 objects that are radio and optically faint. Such objects cannot be easily identified with the combination of submillimeter single-dish and radio imaging. We also found a large fraction of multiple objects that are blended in single-dish images. Such objects may be early-stage mergers, or dusty starbursts in group environments. Since our work, larger surveys with PdBI and ALMA have been carried out to further address these issues. Additional to submillimeter imaging, future ultradeep EVLA imaging at 20 cm can also detect large samples of ultraluminous star forming galaxies at z ≳ 2. Sensitivities in radio and submillimeter observations have different redshift and dust temperature dependencies. Radio observations are also less affected by confusion. It will be necessary to combine deep surveys in both wavebands in order to achieve a more complete picture of the evolution of high-redshift star forming galaxies.

  15. CONFRONTING COLD DARK MATTER PREDICTIONS WITH OBSERVED GALAXY ROTATIONS

    SciTech Connect

    Obreschkow, Danail; Meyer, Martin; Power, Chris; Staveley-Smith, Lister; Ma, Xiangcheng; Zwaan, Martin; Drinkwater, Michael J.

    2013-04-01

    The rich statistics of galaxy rotations as captured by the velocity function (VF) provide invaluable constraints on galactic baryon physics and the nature of dark matter (DM). However, the comparison of observed galaxy rotations against cosmological models is prone to subtle caveats that can easily lead to misinterpretations. Our analysis reveals full statistical consistency between {approx}5000 galaxy rotations, observed in line-of-sight projection, and predictions based on the standard cosmological model ({Lambda}CDM) at the mass-resolution of the Millennium simulation (H I line-based circular velocities above {approx}50 km s{sup -1}). Explicitly, the H I linewidths in the H I Parkes All Sky Survey (HIPASS) are found to be consistent with those in S{sup 3}-SAX, a post-processed semi-analytic model for the Millennium simulation. Previously found anomalies in the VF can be plausibly attributed to (1) the mass-limit of the Millennium simulation, (2) confused sources in HIPASS, (3) inaccurate inclination measurements for optically faint sources, and (4) the non-detectability of gas-poor early-type galaxies. These issues can be bypassed by comparing observations and models using linewidth source counts rather than VFs. We investigate if and how well such source counts can constrain the temperature of DM.

  16. Mid-Infrared Observation of Mass Loss in Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Athey, Alex; Bregman, Joel; Bregman, Jesse; Temi, Pasquale; Sauvage, Marc

    2002-05-01

    Early-type galaxies exhibit thermal and molecular resonance emission from dust that is shed and heated through stellar mass loss as a subset of the population moves through the asymptotic giant branch (AGB) phase of evolution. Because this emission can give direct insight into stellar evolution in addition to galactic stellar mass loss and interstellar medium injection rates, we conducted a program to search for this signature emission with CAM on the Infrared Space Observatory. We obtained 6-15 μm imaging observations in six narrow bands for nine elliptical galaxies; every galaxy is detected in every band. For wavelengths shorter than 9 μm, the spectra are well matched by a blackbody originating from the K and M stars that dominate the integrated light of elliptical galaxies. At wavelengths between 9 and 15 μm, however, the galaxies display excess emission relative to the stellar photospheric radiation. Additional data taken with the fine-resolution circular variable filter on one source clearly shows broad emission from 9 to 15 μm, peaking around 10 μm. This result is consistent with the known broad silicate feature at 9.7 μm originating in the circumstellar envelopes of AGB stars. This emission is compared with studies of Galactic and Large Magellanic Cloud AGB stars to derive cumulative mass-loss rates. In general, these mass-loss rates agree with the expected ~0.8 Msolar yr-1 value predicted by stellar evolutionary models. Both the photospheric and circumstellar envelope emission follow a de Vaucouleurs R1/4 law, supporting the conclusion that the mid-infrared excess emission originates in the stellar component of the galaxies and acts as a tracer of AGB mass loss and mass injection into the interstellar medium.

  17. A homogeneous sample of binary galaxies: Basic observational properties

    NASA Technical Reports Server (NTRS)

    Karachentsev, I. D.

    1990-01-01

    A survey of optical characteristics for 585 binary systems, satisfying a condition of apparent isolation on the sky, is presented. Influences of various selection effects distorting the average parameters of the sample are noted. The pair components display mutual similarity over all the global properties: luminosity, diameter, morphological type, mass-to-luminosity ratio, angular momentum etc., which is not due only to selection effects. The observed correlations must be caused by common origin of pair members. Some features (nuclear activity, color index) could acquire similarity during synchronous evolution of double galaxies. Despite the observed isolation, the sample of double systems is seriously contaminated by accidental pairs, and also by members of groups and clusters. After removing false pairs estimates of orbital mass-to-luminosity ratio range from 0 to 30 f(solar), with the mean value (7.8 plus or minus 0.7) f(solar). Binary galaxies possess nearly circular orbits with a typical eccentrity e = 0.25, probably resulting from evolutionary selection driven by component mergers under dynamical friction. The double-galaxy population with space abundance 0.12 plus or minus 0.02 and characteristic merger timescale 0.2 H(exp -1) may significantly influence the rate of dynamical evolution of galaxies.

  18. An observational study of quasar host galaxies, radio galaxies, and lyman alpha emitters

    NASA Astrophysics Data System (ADS)

    Wold, Isak George Bayard

    In this thesis I provide observational constraints on quasar host galaxies, radio galaxies, and Lyman Alpha Emitters (LAEs). I develop and implement a method to provide stellar age constraints for the host galaxies of nearby (z<0.3) quasars. The observational strategy is to spectroscopically observe quasar host galaxies offset from the bright central point source to maximize the signal-to-noise of the stellar light. The central quasar is also spectroscopically observed, so that any nuclear light scattered into our off-axis spectrum can be efficiently modeled and subtracted. The reliability of my technique is tested via a Monte-Carlo routine in which the correspondence between synthetic spectra with known parameters and the model output is determined. Application of this model to a preliminary sample of 10 objects is presented and compared to previous studies. I present 1.4 GHz catalogs for the cluster fields A370 and A2390 observed with the Very Large Array. These are two of the deepest radio images of cluster fields ever taken. I construct differential number counts for each field and find results consistent with previous studies. I emphasize the need to account for cosmic variance. These high resolution, ultra-deep radio catalogs will be vital to future multiwavelength studies. Finally, I apply a newly developed search method to all of the deep GALEX grism fields, which correspond to some of the most intensively studied regions in the sky. My work provides the first large sample of z=0.67-1.16 LAEs (N=60) that can be used to investigate the physical properties of these galaxies. I catalog the candidate z=1 LAE samples in each field and give optical redshifts from both archival and newly obtained observations. With X-ray, UV, and optical data, I determine the false detection rate (cases where the emission line is either not confirmed or is not Lya) and the AGN contamination rate of my sample. With the remaining LAEs, I compute the LAE galaxy luminosity function

  19. 37 GHz observations of narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Lähteenmäki, A.; Järvelä, E.; Hovatta, T.; Tornikoski, M.; Harrison, D. L.; López-Caniego, M.; Max-Moerbeck, W.; Mingaliev, M.; Pearson, T. J.; Ramakrishnan, V.; Readhead, A. C. S.; Reeves, R. A.; Richards, J. L.; Sotnikova, Y.; Tammi, J.

    2017-07-01

    Observations performed at Metsähovi Radio Observatory at 37 GHz are presented for a sample of 78 radio-loud and radio-quiet narrow-line Seyfert 1 (NLS1) galaxies, together with additional lower and higher frequency radio data from RATAN-600, Owens Valley Radio Observatory, and the Planck satellite. Most of the data have been gathered between February 2012 and April 2015 but for some sources even longer light curves exist. The detection rate at 37 GHz is around 19%, which is comparable to other populations of active galactic nuclei presumed to be faint at radio frequencies, such as BL Lac objects. Variability and spectral indices are determined for sources with enough detections. Based on the radio data, many NLS1 galaxies show a blazar-like radio spectra exhibiting significant variability. The spectra at a given time are often inverted or convex. The source of the high-frequency radio emission in NLS1 galaxies, detected at 37 GHz, is most probably a relativistic jet rather than star formation. Jets in NLS1 galaxies are therefore expected to be a much more common phenomenon than earlier assumed. Full Table 7 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/603/A100

  20. Directly Observing the Galaxies Likely Responsible for Reionization

    NASA Astrophysics Data System (ADS)

    Livermore, R. C.; Finkelstein, S. L.; Lotz, J. M.

    2017-02-01

    We report a new analysis of the Hubble Frontier Fields clusters Abell 2744 and MACS 0416 using wavelet decomposition to remove the cluster light, enabling the detection of highly magnified (>50×) galaxies a factor of 10× fainter in luminosity than previous studies. We find 167 galaxies at z≳ 6, and with this sample we are able to characterize the UV luminosity function to {M}{UV}=-12.5 at z∼ 6, ‑14 at z∼ 7, and ‑15 at z∼ 8. We find a steep faint-end slope (α < -2), and with our improved statistics at the faint end we reduce the fractional uncertainty on α to < 2 % at z∼ 6{--}7 and 4% at z∼ 8. We also investigate the systematic uncertainty due to the lens modeling by using every available lens model individually and comparing the results; this systematic fractional uncertainty on α is < 4 % at all redshifts. We now directly observe galaxies in the luminosity regime where some simulations predict a change in the faint-end slope of the luminosity function, yet our results provide statistically very strong evidence against any turnover in the luminosity range probed, more consistent with simulations in which stars form in lower-mass halos. Thus, we find strong support for the extension of the steep luminosity function to {M}{UV}=-13 at z> 6, consistent with the number of faint galaxies needed to reionize the universe under standard assumptions.

  1. The TANGO Project: Thorough ANalysis of radio-Galaxies Observations

    NASA Astrophysics Data System (ADS)

    Ocaña Flaquer, Breezy; Leon Tanne, Stephane; Combes, Francoise; Lim, Jeremy

    2010-05-01

    We present a sample of radio galaxies selected only on the basis of radio continuum emission and we confirm that these galaxies have lower molecular gas mass than other elliptical galaxies with different selection criteria.

  2. Radio observations of nearby moderately luminous IRAS galaxies

    NASA Astrophysics Data System (ADS)

    Li, Yong-sheng; Su, Bu-mei

    Six nearby moderately luminous IRAS galaxies have been observed at two wavelengths with the Australia Telescope Compact Array. Radio emission was detected in two of them, IRAS 20272-4738 and IRAS 23156-4238, and their parameters including flux, peak position, size and spectral index, obtained. These sources were confirmed with infrared, radio and optical data. Combining with previous results we discuss their emission characteristics.

  3. A Statistical Approach to Galaxy Cluster Gas Inhomogeneity: Chandra Observations of Nearby Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Reese, Erik D.; Kawahara, H.; Kitayama, T.; Sasaki, S.; Suto, Y.

    2009-01-01

    Motivated by cosmological hydrodynamic simulations, the intracluster medium (ICM) inhomogeneity of galaxy clusters is modeled statistically with a lognormal model for density inhomogeneity. Through mock observations of synthetic clusters the relationship between density inhomogeneities and that of the X-ray surface brightness has been developed. This enables one to infer the statistical properties of the fluctuations of the underlying three-dimensional density distribution of real galaxy clusters from X-ray observations. We explore inhomogeneity in the intracluster medium by applying the above methodology to Chandra observations of a sample of nearby galaxy clusters. We also consider extensions of the model, including Poissonian effects and compare this hybrid lognormal-Poisson model to the nearby cluster Chandra data. EDR gratefully acknowledges support from JSPS (Japan Society for the Promotion of Science) Postdoctoral Fellowhip for Foreign Researchers award P07030. HK is supported by Grands-in-Aid for JSPS of Science Fellows. This work is also supported by Grant-in-Aid for Scientific research of Japanese Ministry of Education, Culture, Sports, Science and Technology (Nos. 20.10466, 19.07030, 16340053, 20340041, and 20540235) and by JSPS Core-to-Core Program "International Research Network for Dark Energy".

  4. FIR colours and SEDs of nearby galaxies observed with Herschel

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Ciesla, L.; Buat, V.; Cortese, L.; Auld, R.; Baes, M.; Bendo, G. J.; Bianchi, S.; Bock, J.; Bomans, D. J.; Bradford, M.; Castro-Rodriguez, N.; Chanial, P.; Charlot, S.; Clemens, M.; Clements, D.; Corbelli, E.; Cooray, A.; Cormier, D.; Dariush, A.; Davies, J.; de Looze, I.; di Serego Alighieri, S.; Dwek, E.; Eales, S.; Elbaz, D.; Fadda, D.; Fritz, J.; Galametz, M.; Galliano, F.; Garcia-Appadoo, D. A.; Gavazzi, G.; Gear, W.; Giovanardi, C.; Glenn, J.; Gomez, H.; Griffin, M.; Grossi, M.; Hony, S.; Hughes, T. M.; Hunt, L.; Isaak, K.; Jones, A.; Levenson, L.; Lu, N.; Madden, S. C.; O'Halloran, B.; Okumura, K.; Oliver, S.; Page, M.; Panuzzo, P.; Papageorgiou, A.; Parkin, T.; Perez-Fournon, I.; Pierini, D.; Pohlen, M.; Rangwala, N.; Rigby, E.; Roussel, H.; Rykala, A.; Sabatini, S.; Sacchi, N.; Sauvage, M.; Schulz, B.; Schirm, M.; Smith, M. W. L.; Spinoglio, L.; Stevens, J.; Sundar, S.; Symeonidis, M.; Trichas, M.; Vaccari, M.; Verstappen, J.; Vigroux, L.; Vlahakis, C.; Wilson, C.; Wozniak, H.; Wright, G.; Xilouris, E. M.; Zeilinger, W.; Zibetti, S.

    2010-07-01

    We present infrared colours (in the 25-500 μm spectral range) and UV to radio continuum spectral energy distributions of a sample of 51 nearby galaxies observed with SPIRE on Herschel. The observed sample includes all morphological classes, from quiescent ellipticals to active starbursts. Active galaxies have warmer colour temperatures than normal spirals. In ellipticals hosting a radio galaxy, the far-infrared (FIR) emission is dominated by the synchrotron nuclear emission. The colour temperature of the cold dust is higher in quiescent E-S0a than in star-forming systems probably because of the different nature of their dust heating sources (evolved stellar populations, X-ray, fast electrons) and dust grain properties. In contrast to the colour temperature of the warm dust, the f350/f500 index sensitive to the cold dust decreases with star formation and increases with metallicity, suggesting an overabundance of cold dust or an emissivity parameter β < 2 in low metallicity, active systems. Herschel is an ESA space observatory with science instruments provided by Principal Investigator consortia. It is open for proposals for observing time from the worldwide astronomical community.

  5. OBSERVATIONAL EVIDENCE AGAINST LONG-LIVED SPIRAL ARMS IN GALAXIES

    SciTech Connect

    Foyle, K.; Rix, H.-W.; Walter, F.; Dobbs, C. L.; Leroy, A. K.

    2011-07-10

    We test whether the spiral patterns apparent in many large disk galaxies should be thought of as dynamical features that are stationary in a corotating frame for {approx}> t{sub dyn}, as implied by the density wave approach for explaining spiral arms. If such spiral arms have enhanced star formation (SF), observational tracers for different stages of the SF sequence should show a spatial ordering, from upstream to downstream in the corotating frame: dense H I, CO, tracing molecular hydrogen gas, 24 {mu}m emission tracing enshrouded SF, and UV emission tracing unobscured young stars. We argue that such a spatial ordering should be reflected in the angular cross-correlation (CC, in polar coordinates) using all azimuthal positions among pairs of these tracers; the peak of the CC should be offset from zero, in different directions inside and outside the corotation radius. Recent spiral SF simulations by Dobbs and Pringle show explicitly that for the case of a stationary spiral arm potential such angular offsets between gas and young stars of differing ages should be observable as cross-correlation offsets. We calculate the angular cross-correlations for different observational SF sequence tracers in 12 nearby spiral galaxies, drawing on a data set with high-quality maps of the neutral gas (H I, THINGS) and molecular gas (CO, HERACLES), along with 24 {mu}m emission (Spitzer, SINGS); we include FUV images (GALEX) and 3.6 {mu}m emission (Spitzer, IRAC) for some galaxies, tracing aging stars and longer timescales. In none of the resulting tracer cross-correlations for this sample do we find systematic angular offsets, which would be expected for a stationary dynamical spiral pattern of well-defined pattern speed. This result indicates that spiral density waves in their simplest form are not an important aspect of explaining spirals in large disk galaxies.

  6. COMPARISONS OF COSMOLOGICAL MAGNETOHYDRODYNAMIC GALAXY CLUSTER SIMULATIONS TO RADIO OBSERVATIONS

    SciTech Connect

    Xu Hao; Li Hui; Collins, David C.; Govoni, Federica; Murgia, Matteo; Norman, Michael L.; Cen Renyue; Feretti, Luigina; Giovannini, Gabriele E-mail: hli@lanl.gov E-mail: mlnorman@ucsd.edu E-mail: matteo@oa-cagliari.inaf.it E-mail: lferetti@ira.inaf.it

    2012-11-01

    Radio observations of galaxy clusters show that there are {mu}G magnetic fields permeating the intracluster medium (ICM), but it is hard to accurately constrain the strength and structure of the magnetic fields without the help of advanced computer simulations. We present qualitative comparisons of synthetic Very Large Array observations of simulated galaxy clusters to radio observations of Faraday rotation measure (RM) and radio halos. The cluster formation is modeled using adaptive mesh refinement magnetohydrodynamic simulations with the assumption that the initial magnetic fields are injected into the ICM by active galactic nuclei (AGNs) at high redshift. In addition to simulated clusters in Xu et al., we present a new simulation with magnetic field injections from multiple AGNs. We find that the cluster with multiple injection sources is magnetized to a similar level as in previous simulations with a single AGN. The RM profiles from simulated clusters, both |RM| and the dispersion of RM ({sigma}{sub RM}), are consistent at a first order with the radial distribution from observations. The correlations between the {sigma}{sub RM} and X-ray surface brightness from simulations are in a broad agreement with the observations, although there is an indication that the simulated clusters could be slightly overdense and less magnetized with respect to those in the observed sample. In addition, the simulated radio halos agree with the observed correlations between the radio power versus the cluster X-ray luminosity and between the radio power versus the radio halo size. These studies show that the cluster-wide magnetic fields that originate from AGNs and are then amplified by the ICM turbulence match observations of magnetic fields in galaxy clusters.

  7. Observational tests of nonlocal gravity: Galaxy rotation curves and clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Rahvar, S.; Mashhoon, B.

    2014-05-01

    A classical nonlocal generalization of Einstein's theory of gravitation has recently been developed via the introduction of a scalar causal "constitutive" kernel that must ultimately be determined from observational data. It turns out that the nonlocal aspect of gravity in this theory can simulate dark matter; indeed, in the Newtonian regime of nonlocal gravity, we recover the phenomenological Tohline-Kuhn approach to modified gravity. A simple generalization of the Kuhn kernel in the context of nonlocal general relativity leads to a two-parameter modified Newtonian force law that involves an additional repulsive Yukawa-type interaction. We determine the parameters of our nonlocal kernel by comparing the predictions of the theory with observational data regarding the rotation curves of spiral galaxies. The best-fitting stellar mass-to-light ratio turns out to be in agreement with astrophysical models; moreover, our results are consistent with the Tully-Fisher relation for spiral galaxies. Light deflection in nonlocal gravity is consistent with general relativity at solar-system scales, while beyond galactic scales, an enhanced deflection angle is predicted that is compatible with lensing by the effective "dark matter." Furthermore, we extend our results to the internal dynamics of rich clusters of galaxies and show that the dynamical mass of the cluster obtained from nonlocal gravity is consistent with the measured baryonic mass.

  8. Observations of CO in the Magellanic irregular galaxy NGC 55

    NASA Technical Reports Server (NTRS)

    Heithausen, Andreas; Dettmar, Ralf-Juergen

    1990-01-01

    The content of molecular gas in galaxies, mainly H2, is one of the key observations necessary for the understanding of star formation processes and history. As the CO molecule is the most widely distributed molecule after H2 and has easily observable mm lines, it is used as a tracer for the molecular gas. CO was detected towards the direction where the H alpha and 6 cm radio continuum emission is strongest (Hummel et al. 1986). Here, researchers present the Gaussian line parameters in tabular form. The distribution of CO corresponds well with the intense HI cloud near the bar of NGC 55. The extent of the CO cloud is about 975 pc perpendicular to the major axis. As the radio continuum and the H alpha emission also peaks in this region, it is most probably associated with the star forming region in NGC 55. Assuming that the molecular gas is in virial equilibrium, researchers derive a mass of about 8 times 10(exp 7) solar magnitude. The molecular mass found indicates that the conversion factor for the molecular mass in Irr galaxies as inferred from CO line emission is indeed higher by up to a factor of 20 compared to the canonical value for the Galaxy.

  9. Observations of CO in the Magellanic irregular galaxy NGC 55

    NASA Astrophysics Data System (ADS)

    Heithausen, Andreas; Dettmar, Ralf-Juergen

    1990-07-01

    The content of molecular gas in galaxies, mainly H2, is one of the key observations necessary for the understanding of star formation processes and history. As the CO molecule is the most widely distributed molecule after H2 and has easily observable mm lines, it is used as a tracer for the molecular gas. CO was detected towards the direction where the H alpha and 6 cm radio continuum emission is strongest (Hummel et al. 1986). Here, researchers present the Gaussian line parameters in tabular form. The distribution of CO corresponds well with the intense HI cloud near the bar of NGC 55. The extent of the CO cloud is about 975 pc perpendicular to the major axis. As the radio continuum and the H alpha emission also peaks in this region, it is most probably associated with the star forming region in NGC 55. Assuming that the molecular gas is in virial equilibrium, researchers derive a mass of about 8 times 107 solar magnitude. The molecular mass found indicates that the conversion factor for the molecular mass in Irr galaxies as inferred from CO line emission is indeed higher by up to a factor of 20 compared to the canonical value for the Galaxy.

  10. H I OBSERVATIONS OF FIVE GROUPS OF GALAXIES

    SciTech Connect

    Freeland, E.; Wilcots, E.; Stilp, A.

    2009-07-15

    We present the results of H I observations of five groups of galaxies spanning a range of velocity dispersion and spiral fraction (brightest optical group member in parenthesis): NGC 7582 (NGC 7552), USGC U207 (NGC 2759), USGC U070 (NGC 664), USGC U412 (NGC 3822), USGC U451 (NGC 4065). Neutral intragroup gas is detected in three of the five groups. We present the discovery of a previously uncataloged galaxy in the USGC U070 group at {alpha}(2000) = 01{sup h}45{sup m}27{sup s}, {delta}(2000) = +0436'19'', which we are designating FSW J014526.92+043619.1. We compile an H I mass function for the group environment and find that the faint-end slope is consistent with being flat.

  11. Percolation analyses of observed and simulated galaxy clustering

    NASA Astrophysics Data System (ADS)

    Bhavsar, S. P.; Barrow, J. D.

    1983-11-01

    A percolation cluster analysis is performed on equivalent regions of the CFA redshift survey of galaxies and the 4000 body simulations of gravitational clustering made by Aarseth, Gott and Turner (1979). The observed and simulated percolation properties are compared and, unlike correlation and multiplicity function analyses, favour high density (Omega = 1) models with n = - 1 initial data. The present results show that the three-dimensional data are consistent with the degree of filamentary structure present in isothermal models of galaxy formation at the level of percolation analysis. It is also found that the percolation structure of the CFA data is a function of depth. Percolation structure does not appear to be a sensitive probe of intrinsic filamentary structure.

  12. Comparing models of star formation simulating observed interacting galaxies

    NASA Astrophysics Data System (ADS)

    Quiroga, L. F.; Muñoz-Cuartas, J. C.; Rodrigues, I.

    2017-07-01

    In this work, we make a comparison between different models of star formation to reproduce observed interacting galaxies. We use observational data to model the evolution of a pair of galaxies undergoing a minor merger. Minor mergers represent situations weakly deviated from the equilibrium configuration but significant changes in star fomation (SF) efficiency can take place, then, minor mergers provide an unique scene to study SF in galaxies in a realistic but yet simple way. Reproducing observed systems also give us the opportunity to compare the results of the simulations with observations, which at the end can be used as probes to characterize the models of SF implemented in the comparison. In this work we compare two different star formation recipes implemented in Gadget3 and GIZMO codes. Both codes share the same numerical background, and differences arise mainly in the star formation recipe they use. We use observations from Pico dos Días and GEMINI telescopes and show how we use observational data of the interacting pair in AM2229-735 to characterize the interacting pair. Later we use this information to simulate the evolution of the system to finally reproduce the observations: Mass distribution, morphology and main features of the merger-induced star formation burst. We show that both methods manage to reproduce roughly the star formation activity. We show, through a careful study, that resolution plays a major role in the reproducibility of the system. In that sense, star formation recipe implemented in GIZMO code has shown a more robust performance. Acknowledgements: This work is supported by Colciencias, Doctorado Nacional - 617 program.

  13. Galaxy Populations and Evolution in Clusters IV Deep H 1 Observations of Dwarf Elliptical Galaxies in the Virgo Cluster

    NASA Technical Reports Server (NTRS)

    Conselice, Christopher J.; ONeil, Karen; Gallagher, John S.; Wyse, Rosemary F. G.

    2003-01-01

    In this paper we present deep Arecibo H I and WIYN optical observations of Virgo Cluster dwarf elliptical galaxies. Based on this data we argue that a significant fraction of low-mass galaxies in the Virgo Cluster recently underwent evolution. Our new observations consist of H I 21 cm line observations for 22 classified dE galaxies with optical radial velocities consistent with membership in the Virgo Cluster. Cluster members VCC 390 and VCC 1713 are detected with H 1 masses M H1= 6 x 10 sup 7 and 8 x 10 sup 7 M , respectively, while MH I values in the remaining 20 dE galaxies have upper limits as low as about 5 x 1O sup 5 M. We combine our results with those for 26 other Virgo Cluster dE galaxies with H 1 observations in the literature, seven of which have H I detection claims.

  14. HST/WFPC2 Observations of Warm Ultraluminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Surace, Jason A.; Sanders, D. B.; Vacca, William D.; Veilleux, Sylvain; Mazzarella, J. M.

    1998-01-01

    We present new high-resolution B- and I-band images of a nearly complete sample of nine ``warm'' (f25/f60 > 0.2), ultraluminous infrared galaxies (ULIGs) obtained with the Wide Field Planetary Camera of the Hubble Space Telescope (HST). The HST images clearly reveal the presence of tidal tails and other features associated with merging galaxies. All of the warm ULIGs show evidence of complex structures such as dust lanes and spiral features in their inner few kiloparsecs. Additionally, they show compact, blue ``knots'' of star formation (between 4 and 31 knots per object) that appear similar to those seen in more nearby merger systems. Spectral synthesis modeling is used to estimate mean upper age limits and masses: the median upper age limit for the knots in individual galaxies is ~3 × 108 yr (ranging from ~107 to 1 × 109 yr), and the range of knot masses is ~105-109 M⊙. We also argue that these starburst knots cannot be significant contributors to the extremely high bolometric luminosity of these galaxies. Additionally, each object contains one or two knots whose luminosity and color are implausible in terms of star formation; we identify these as putative active nuclei. These observations are consistent with the hypothesis that warm ULIGs may represent a critical transition stage in the evolution of ULIGs into optical quasi-stellar objects. Based on observations 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.

  15. New Observations Deepen Mystery Surrounding Water Masers in Elliptical Galaxy

    NASA Astrophysics Data System (ADS)

    New observations with the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope have deepened the mystery surrounding water molecules in a galaxy 65 million light- years away. The water molecules are acting as natural masers -- amplifiers of microwave radio emissions -- and these cosmic masers within the galaxy NGC 1052 are raising difficult questions for astronomers trying to explain them. Results of the new observations, which pinpoint the location of water masers in NGC 1052, were announced today at the American Astronomical Society meeting in Toronto, Ontario. The researchers are: Jim Braatz of Harvard University in Cambridge, Massachusetts, Mark Claussen and Phil Diamond of the National Radio Astronomy Observatory in Socorro, New Mexico, Andrew Wilson of the University of Maryland in College Park, Maryland, and Christian Henkel of the Max Planck Institute fur Radioastronomie in Bonn, Germany. Water masers have been detected in several other galaxies. However, most galaxies containing water "megamasers" such as those in NGC 1052 are spiral galaxies. NGC 1052 is one of only two elliptical galaxies in which water megamasers have been detected. Because ellipticals tend to have much less gas and dust than spirals, the existence of the water masers in NGC 1052 is surprising by itself, though that galaxy does have more gas and dust than the typical elliptical. Located in the constellation Cetus, NGC 1052 also has an active nucleus, believed to be powered by the gravitational energy of a supermassive black hole at its core. The new VLBA observations produced an additional mystery. In other galaxies with water megamasers, the masers are believed to lie within a disk of molecules orbiting the galaxy's central black hole. This is the case, for example, in the now-famous galaxy NGC 4258, where the movement of the orbiting disk can be traced by measuring both the Doppler shift of radio emission from the masers and by tracking the motion of

  16. New water and remote galaxies complete ISO's observations

    NASA Astrophysics Data System (ADS)

    to deduce the presence of diverse materials in interstellar space, in the surroundings of stars, and in other galaxies. As previously reported, ISO has identified stony materials, tarry compounds of carbon, and vapours and ices like water and carbon monoxide. Together they give the first clear picture of how Mother Nature prepares, from elements manufactured in stars, the ingredients needed for planets and for life itself. Particularly striking for the human imagination are ISO's repeated discoveries of water in the deserts of space. They encourage expectations of life elsewhere in the Universe. Water has turned up around dying stars, newborn stars, in the general interstellar medium, in the atmospheres of the outer planets and in other galaxies too. A link to the Earth's oceans and the water we live by comes in the water- ice long known to be a major ingredient of comets, which are relics from the era of planet-building. A further link to the investigation of the origin of life is the apparent detection of water vapour in the mysterious atmosphere of Saturn's largest moon, Titan. A preliminary announcement comes from an international team headed by Athena Coustenis of Paris Observatory and Alberto Salama of the ISO Science Operations Center at Villafranca. The team used ISO's Short Wavelength Spectrometer during several hours of observations last December, when Titan was at its farthest from Saturn as seen by ISO. Emissions at wavelengths of 39 and 44 microns showed up, as an expected signature of water vapour. The news will excite the scientists involved in ESA's probe Huygens, launched last year aboard NASA's Cassini spacecraft. It will parachute into Titan's atmosphere to see what the chemistry of the Earth may have been like before life began. "Water vapour makes Titan much richer," comments Athena Coustenis. "We knew there was carbon monoxide and carbon dioxide in Titan's atmosphere, so we expected water vapour too. Now that we believe we've found it, we can

  17. Observational evidence for AGN feedback in early-type galaxies

    NASA Astrophysics Data System (ADS)

    Schawinski, Kevin; Thomas, Daniel; Sarzi, Marc; Maraston, Claudia; Kaviraj, Sugata; Joo, Seok-Joo; Yi, Sukyoung K.; Silk, Joseph

    2007-12-01

    A major amendment in recent models of hierarchical galaxy formation is the inclusion of so-called active galactic nucleus (AGN) feedback. The energy input from an active central massive black hole is invoked to suppress star formation in early-type galaxies at later epochs. A major problem is that this process is poorly understood, and compelling observational evidence for its mere existence is still missing. In search for signatures of AGN feedback, we have compiled a sample of 16000 early-type galaxies in the redshift range 0.05 < z < 0.1 from the Sloan Digital Sky Survey (SDSS) data base (MOSES: Morphologically Selected Ellipticals in SDSS). Key in our approach is the use of a purely morphological selection criterion through visual inspection which produces a sample that is not biased against recent star formation and nuclear activity. Based on the nebular emission-line characteristics we separate between star formation activity, black hole activity, the composite of the two and quiescence. We find that emission is mostly LINER (low ionization nuclear emission line region) like in high-mass galaxies (σ > 200kms-1) and roughly evenly distributed between star formation and AGN at intermediate and low (σ < 100kms-1) masses. The objects with emission (~20 per cent) are offset from the red sequence and form a well-defined pattern in the colour-mass diagram. Star-forming early-types inhabit the blue cloud, while early-types with AGN are located considerably closer to and almost on the red sequence. Star formation-AGN composites are found right between these two extremes. We further derive galaxy star formation histories using a novel method that combines multiwavelength photometry from near-ultraviolet (UV) to near-infrared (IR) and stellar absorption indices. We find that in those objects deviating from the red sequence star formation occurred several 100Myr in the past involving 1-10per cent of the total stellar mass. We identify an evolutionary sequence from star

  18. WFPC2 Observations of the URSA Minor Dwarf Spheroidal Galaxy

    NASA Technical Reports Server (NTRS)

    Mighell, Kenneth J.; Burke, Christopher J.

    1999-01-01

    We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) observations in F555W (approximately V) and F814W (approximately I) of the central region of the Ursa Minor dwarf spheroidal galaxy. The V versus V - I color-magnitude diagram features a sparsely populated blue horizontal branch, a steep thin red giant branch, and a narrow subgiant branch. The main sequence reaches approximately 2 magnitudes below the main-sequence turnoff (V(sup UMi, sub TO) approximately equals 23.27 +/- 0.11 mag) of the median stellar population. We compare the fiducial sequence of the Galactic globular cluster M92 (NGC 6341). The excellent match between Ursa Minor and M92 confirms that the median stellar population of the UMi dSph galaxy is metal poor ([Fe/H](sub UMi) approximately equals [Fe/H](sub M92) approximately equals -2.2 dex) and ancient (age(sub UMi)approximately equalsage(sub M92) approximately equals 14 Gyr). The B - V reddening and the absorption in V are estimated to be E(B - V) = 0.03 +/- 0.01 mag and A(sup UMi, sub V) = 0.09 +/- 0.03 mag. A new estimate of the distance modulus of Ursa Minor, (m - M)(sup UMi, sub 0) = 19.18 +/- 0.12 mag, has been derived based on fiducial-sequence fitting M92 [DELTA.V(sub UMi - M92) = 4.60 +/- 0.03 mag and DELTA(V - I)(sub UMi - M92) = 0.010 +/- 0.005 mag] and the adoption of the apparent V distance modulus for M92 of (m - M)(sup M92, sub V) = 14.67 +/- 0.08 mag (Pont et al. 1998, A&A, 329, 87). The Ursa Minor dwarf spheroidal galaxy is then at a distance of 69 +/- 4 kpc from the Sun. These HST observations indicate that Ursa Minor has had a very simple star formation history consisting mainly of a single major burst of star formation about 14 Gyr ago which lasted approximately < 2 Gyr. While we may have missed minor younger stellar populations due to the small field-of-view of the WFPC2 instrument, these observations clearly show that most of the stars in the central region Ursa Minor dwarf

  19. Revisiting perfect fluid dark matter: Observational constraints from our galaxy

    NASA Astrophysics Data System (ADS)

    Potapov, Alexander A.; Garipova, Guzel M.; Nandi, Kamal K.

    2016-02-01

    We revisit certain features of an assumed spherically symmetric perfect fluid dark matter halo in the light of the observed data of our galaxy, the Milky Way (MW). The idea is to apply the Faber-Visser approach of combined observations of rotation curves and lensing to a first post-Newtonian approximation to "measure" the equation of state ω (r) of the perfect fluid galactic halo. However, for the model considered here, no constraints from lensing are used as it will be sufficient to consider only the rotation curve observations. The lensing mass together with other masses will be just computed using recent data. Since the halo has attractive gravity, we shall impose the constraint that ω (r) ≥ 0 for r ≤RMW, where RMW ∼ 200 kpc is the adopted halo radius of our galaxy. The observed circular velocity ℓ (= 2 vc2 / c02) from the flat rotation curve and a crucial adjustable parameter D appearing in the perfect fluid solution then yield different numerical ranges of ω (r). It is demonstrated that the computed observables such as the rotation curve mass, the lens mass, the post-Newtonian mass of our galaxy compare well with the recent mass data. We also calculate the Faber-Visser χ-factor, which is a measure of pressure content in the dark matter. Our analysis indicates that a range 0 ≤ ω (r) ≤ 2.8 ×10-7 for the perfect fluid dark matter can reasonably describe the attractive galactic halo. This is a strong constraint indicating a dust-like CDM halo (ω ∼ 0) supported also by CMB constraints.

  20. Radio continuum JVLA observations of the dwarf galaxy Sextans A

    NASA Astrophysics Data System (ADS)

    Monkiewicz, Jacqueline A.; Powell, Devon; Dettmar, Ralf-Juergen; Bomans, Dominik; Bowman, Judd D.; Scannapieco, Evan

    2017-06-01

    We present 20-cm Jansky Very Large Array (JVLA) observations of the star-forming dwarf galaxy Sextans A. Located at the outer edge of the Local Group, with an oxygen abundance of less than one-tenth of the Solar abundance (12+log O/H = 7.49), Sextans A provides a nearby laboratory for the study of low-metallicity star formation processes. This galaxy is a weak source in the infrared, but exhibits evidence for vigorous star formation-powered outflows in ionized gas, including large-scale H-alpha shells and filaments up to a kpc in length. Sextans A has not previously been detected in radio continuum. The upgraded JVLA and WIDAR correlator provide enhanced sensitivity over previous studies. We resolve a 3.0 mJy (+/- 0.3 mJy) continuum source centered on the brightest star formation region in Sextans A. Using two relatively interference-free windows at 1.4 GHz and 1.85 GHz, we are able to measure the spectral slope of the detected emission. We estimate the non-thermal contribution and the strength of the galaxy's magnetic field. We discuss the impact of low metallicity on the reliability of the IR/radio relation.

  1. 1 Mpc giant radio galaxy IC 711 - 3 km Westerbork observations at 92 cm

    SciTech Connect

    Vallee, J.P.; Strom, R.G.

    1988-05-01

    New Westerbork obsevations at 92 cm of the galaxy IC 711 show a radio trail that extends 1 Mpc long, much farther out than previously observed at shorter wavelengths. These new observations confirm IC 711 as the longest head-tail galaxy known, and move IC 711 to the fifth rank among galaxies with the largest radio extension from an optical galaxy nucleus (after the classical double sources 3C 236, 3C 326, HB 13, and MSH 05-22). 20 references.

  2. Deep Radio Observations of the Toothbrush Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    Van Weeren, Reinout J.; Jones, C.; Forman, W. R.; Röttgering, H.; Brüggen, M.; Brunetti, G.; de Gasperin, F.; Bonafede, A.; Pizzo, R.; Ferrari, C.; Orrù, E.; Ogrean, G. A.; LOFAR Busyweek Team; surveys KSP, LOFAR

    2014-01-01

    We present LOFAR and JVLA radio observations of the Toothbrush galaxy cluster. The Toothbrush cluster hosts diffuse 2 Mpc extended radio emission in the form of a radio relic and halo. XMM-Newton X-ray observations show that the cluster is undergoing a major merger event. Both the radio relic and halo are likely related to this ongoing merger. Radio relics are proposed to be direct tracers of shock waves in the intracluster medium. The XMM observations indeed reveal a shock, but there is a puzzling 200 kpc spatial offset between the shock position and relic. Our deep LOFAR and JVLA observations allow a detailed spectral study to test the shock origin of the relic and underlying particle acceleration mechanisms. Finally, the LOFAR observations highlight the science that could be obtained from a deep low-frequency all-sky survey.

  3. Observing the First Stars in Luminous, Red Galaxies

    NASA Technical Reports Server (NTRS)

    Heap, Sally; Lindler, Don

    2010-01-01

    Modern cosmological simulations predict that the first stars are to be found today in luminous, red galaxies. Although observing such stars individually against a background of younger, metal-rich stars is impossible, the first stars should make their presence known by their strong, line-free ultraviolet flux. We have found evidence for a UV-bright stellar population in Sloan spectra of LRG's at z=0.4-0.5. We present arguments for interpreting this UV-bright stellar population as the oldest stars, rather than other types of stellar populations (e.g. young stars or blue straggler stars in the dominant, metal-rich stellar population

  4. High-dynamic range JVLA observations of clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Hlavacek-Larrondo, Julie

    2017-08-01

    The recently upgraded JVLA has enabled a breakthrough in radio astronomy by providing a radio telescope with unprecedented sensitivity, resolution, and imaging capabilities. We present new JVLA observations of clusters of galaxies, including state-of-the-art low-frequency 230-470 MHz observations of the Perseus cluster. These observations not only illustrate the high-quality/high-dynamic range images that can be obtained with the upgraded JVLA, but they also reveal that mini-halos are not simply diffuse, uniform radio sources. Instead, mini-halos appear to be filled with a rich variety of complex radio structures including arcs, filaments and edges. The depth and resolution of the JVLA observations allow us to conduct for the first time a detailed comparison of the mini-halo structure with the X-ray structure as seen in the Chandra X-ray images, providing new clues about the acceleration mechanisms of relativistic particles in the intracluster medium.

  5. Galactic Observations of Terahertz C+ (GOT C+): Inner Galaxy Survey

    NASA Astrophysics Data System (ADS)

    Yorke, Harold; Langer, William; Velusamy, T.; Pineda, J. L.; Goldsmith, P. F.; Li, D.

    To understand the lifecycle of the interstellar gas and star formation we need detailed information about the diffuse atomic and diffuse molecular gas cloud properties. The ionized carbon [CII] 1.9 THz fine structure line is an important tracer of the atomic gas in the diffuse regions and the interface regions of atomic gas to molecular clouds. Furthermore, C+ is a major ISM coolant and among the Galaxy's strongest far-IR emission lines, and thus controls the thermal conditions throughout large parts of the Galaxy. Until now our knowledge of interstellar gas has been limited to the diffuse atomic phase traced by HI and to the dense molecular H2 phase traced by CO. However, we are missing an important phase of the ISM, called "dark gas" in which there is no or little, HI, and mostly molecular hydrogen but with insufficient shielding of UV to allow CO to form. C+ emission and absorption lines at 1.9 THz have the potential to trace such cloud transitions and evolution. Galactic Observations of the Terahertz C+ Line (GOT C+) is a Herschel Space Observatory Open Time Key Program to study the diffuse interstellar medium by sampling [CII] 1.9 THz line emission throughout the Galactic disk. We discuss the broader perspective of this survey and the first results of GOT C+ obtained during the Science Demonstration Phase (SDP) and Priority Science Phase (PSP) of HIFI, which focus on approximately 100 lines of sight in the inner galaxy. These observations are being carried out with the Herschel Space Observatory, which is an ESA cornerstone mission, with contributions from NASA. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. JLP is a Caltech-JPL Postdoctoral Associate.

  6. Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097

    NASA Astrophysics Data System (ADS)

    Martín, S.; Kohno, K.; Izumi, T.; Krips, M.; Meier, D. S.; Aladro, R.; Matsushita, S.; Takano, S.; Turner, J. L.; Espada, D.; Nakajima, T.; Terashima, Y.; Fathi, K.; Hsieh, P.-Y.; Imanishi, M.; Lundgren, A.; Nakai, N.; Schinnerer, E.; Sheth, K.; Wiklind, T.

    2015-01-01

    Context. The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory for exploring the molecular chemistry in the surroundings of an active galactic nucleus (AGN). Aims: Exploring the distribution of different molecular species allows us to understand the physical processes affecting the interstellar medium both in the AGN vicinity and in the outer star forming molecular ring. Methods: We carried out 3 mm ALMA observations that include seven different molecular species, namely HCN, HCO+, CCH, CS, HNCO, SiO, HC3N, and SO, as well as the 13C isotopologues of the first two. Spectra were extracted from selected positions and all species were imaged over the central 2 kpc (~30'') of the galaxy at a resolution of ~2.2'' × 1.5'' (150 pc × 100 pc). Results: HCO+ and CS appear to be slightly enhanced in the star forming ring. CCH shows the largest variations across NGC 1097 and is suggested to be a good tracer of both obscured and early stage star formation. HNCO, SiO, and HC3N are significantly enhanced in the inner circumnuclear disk surrounding the AGN. Conclusions: Differences in the molecular abundances are observed between the star forming ring and the inner circumnuclear disk. We conclude that the HCN/HCO+ and HCN/CS differences observed between AGN-dominated and starburst (SB) galaxies are not due to a HCN enhancement due to X-rays, but rather this enhancement is produced by shocked material at distances of 200 pc from the AGN. Additionally, we claim that lower HCN/CS is a combination of a small underabundance of CS in AGNs, together with excitation effects, where a high density gas component (~106 cm-3) may be more prominent in SB galaxies. However, the most promising are the differences found among the dense gas tracers that, at our modest spatial resolution, seem to outline the physical structure of the molecular disk around the AGN. In this picture, HNCO probes the well-shielded gas in the disk, surrounding the dense material moderately exposed to the X

  7. Spectroscopic observations of southern nearby galaxies. I. NGC 2442

    NASA Astrophysics Data System (ADS)

    Bajaja, E.; Agüero, E.; Paolantonio, S.

    1999-04-01

    The galaxy NGC 2442 was observed with a REOSC spectrograph, installed in the 2.15 m CASLEO telescope, in order to derive galactic parameters from the observed optical lines and to compare them with the results of radioastronomical observations made in the continuum, at 843 MHz, with the MOST and in the CO lines with the SEST telescope. Recent publications allowed us to extend the comparison to results from interferometric observations of Hα and H I 21 cm lines and of the continuum at 1415 MHz. The long slit observations were made placing the 5farcm 8 slit at six different positions on the optical image of the galaxy. The emission line intensity ratios at the nuclear region indicate that NGC 2442 is a LINER. The electron temperature and volume density are Te ~ 14 000 K and Ne ~ 530 cm(-3) , respectively. In contrast, a spectrum of a region 87arcsec to the NE shows the typical characteristics of a H Ii region. In this case Te ~ 6,500 K and Ne ~ 10 cm(-3) . Good correlations between the distributions of intensities, velocity fields and rotation curves have been found for the optical and radio lines. It is shown that the three intensity peaks along the line at PA = 40degr were not resolved by the observations at radio frequencies. The steep central rotation curve seen in CO has been confirmed and improved showing the existence of a disc or a ring, with a radius of 12.5 arcsec, rotating at 216/sin(i) km s(-1). Two velocity components in three optical spectra obtained in the nuclear region, have been related to two small Hα regions close to the nucleus and to the central ring. Asymmetries in the distributions of the emitting sources and irregularities in their velocity fields indicate the need of modelling the galaxy before any dynamical study is attempted. Based on observations made in the Complejo Astronomico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina and the National

  8. THE ARECIBO GALAXY ENVIRONMENT SURVEY. III. OBSERVATIONS TOWARD THE GALAXY PAIR NGC 7332/7339 AND THE ISOLATED GALAXY NGC 1156

    SciTech Connect

    Minchin, R. F.; Momjian, E.; Auld, R.; Davies, J. I.; Smith, M. W. L.; Taylor, R.; Valls-Gabaud, D.; Van Driel, W.; Karachentsev, I. D.; Henning, P. A.; O'Neil, K. L.

    2010-10-15

    Two 5 deg{sup 2} regions around the NGC 7332/9 galaxy pair and the isolated galaxy NGC 1156 have been mapped in the 21 cm line of neutral hydrogen (H I) with the Arecibo L-band Feed Array out to a redshift of {approx}0.065 ({approx}20,000 km s{sup -1}) as part of the Arecibo Galaxy Environment Survey. One of the aims of this survey is to investigate the environment of galaxies by identifying dwarf companions and interaction remnants; both of these areas provide the potential for such discoveries. The neutral hydrogen observations were complemented by optical and radio follow-up observations with a number of telescopes. A total of 87 galaxies were found, of which 39 (45%) were previously cataloged and 15 (17%) have prior redshifts. Two dwarf galaxies have been discovered in the NGC 7332 group and a single dwarf galaxy in the vicinity of NGC 1156. A parallel optical search of the area revealed one further possible dwarf galaxy near NGC 7332.

  9. Iron line profiles and BH spin in deep Suzaku observations of Seyfert 1 AGN

    NASA Astrophysics Data System (ADS)

    Patrick, A. R.; Reeves, J. N.; Lobban, A. P.; Porquet, D.; Markowitz, A. G.

    2012-03-01

    We present a broad-band analysis of deep Suzaku observations of nearby Seyfert 1 AGN: Fairall 9, MCG-6-30-15, NGC 3516, NGC 3783 and NGC 4051. The use of deep observations (exposures > 200 ks) with high S/N allows the complex spectra of these objects to be examined in full, taking into account features such as the soft excess, reflection continuum and complex absorption components. After a self-consistent modelling of the broad-band data (0.6-100.0 keV, also making use of BAT data from Swift), the subtle curvature which may be introduced as a consequence of warm absorbers has a measured affect upon the spectrum at energies > 3 keV and the FeK region. Forming a model (including absorption) of these AGN allows the true extent to which broadened diskline emission is present to be examined and as a result the measurement of accretion disc and black hole parameters which are consistent over the full 0.6-100.0 keV energy range.

  10. Chandra Observations of Dying Radio Sources in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-01-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims. We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods. We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results. The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions. We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  11. An observational study of arm structure in normal spiral galaxies

    NASA Astrophysics Data System (ADS)

    Magri, Christopher

    Multivariate data were obtained and analyzed in an effort to develop a new classification system for spiral galaxies, one which is not necessarily based on morphological properties. By comparing morphological measures with the intrinsic parameters on which the new system is based, it can be seen just how fundamentally important a galactic property arm structure truly is. A sample of 492 moderately bright northern Sa, SBa, Sc, and SBc spirals was chosen for statistical analysis. The literature was searched for redshifts, optical and near-infrared photometric data, 20 cm fluxes, and H I 21 cm line parameters. New observations were made at 20 and 21 cm; in addition, IRAS fluxes were obtained from archival data. These data were subjected to principal component analysis, modified in that non-detections were explicitly acknowledged. Spiral galaxies have two fundamental properties, confirming previous work done with fewer data. While scale (bulk) is most important, galaxies of given scale can vary in form (color, bulge/disk ratio, H I surface density). Arm strength is unrelated to other properties. Forty-five spatially isolated spirals were chosen for two-color optical CCD imaging, for 20 cm continuum imaging, and for CO 2.6 mm spectroscopy. Isolated Sa's are often found to be misclassified; they are either armless SO's or else peculiar victims of collisions. Isolated Sc's are surprising in that all but the most isolated examples have symmetric arms over at least part of the disk, contrary to the predictions of stochastic models for arm formation. Given the extreme isolation of all highly chaotic disks, the presence of tidal companions (or at least candidates) for the other normal isolated spirals, the apparent prevalence of violent processes in isolated Sa's, and recent N-body simulations of tidal encounters, it is likely that arm structure in most spirals is produced by tidal encounters with small companions. Arm structure is not an intrinsic property of a given galaxy

  12. Chandra observations of dying radio sources in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-12-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims: We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods: We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results: The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions: We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  13. Constraining Galaxy Evolution Using Observed UV-Optical Spectra

    NASA Technical Reports Server (NTRS)

    Heap, Sally

    2007-01-01

    Our understanding of galaxy evolution depends on model spectra of stellar populations, and the models are only as good as the observed spectra and stellar parameters that go into them. We are therefore evaluating modem UV-optical model spectra using Hubble's Next Generation Spectral Library (NGSL) as the reference standard. The NGSL comprises intermediate-resolution (R is approximately 1000) STIS spectra of 378 stars having a wide range in metallicity and age. Unique features of the NGSL include its broad wavelength coverage (1,800-10,100 A) and high-S/N, absolute spectrophotometry. We will report on a systematic comparison of model and observed UV-blue spectra, describe where on the HR diagram significant differences occur, and comment on current approaches to correct the models for these differences.

  14. Further radio observations of IRAS extreme infrared galaxies

    NASA Astrophysics Data System (ADS)

    Antonucci, R. R. J.; Olszewski, E. W.

    1986-01-01

    Aaronson and Olszewski (1984) have identified five IRAS infrared sources, previously considered to be blank fields, with faint galaxies. The authors reported previously the results of their VLA D-array observations at 6 cm (Antonucci and Olszewski, 1985), which resulted in detections of all objects at the mJy level. The sources were unresolved by the ≡16 arcsec beam. The present paper reports on B-array observations at 6 and 20 cm, made in order to determine or limit the source angular sizes, and to measure the spectral indices. The source 0358+223 has an angular size of ≡3 arcsec at 20 cm, but no redshift is available for this object; also 0404+101 is marginally resolved at 20 cm. The other sources are unresolved by the ≡1.1 arcsec resolution deep 6 cm maps, implying linear sizes <2 kpc. The spectra are steep, indicating that the radiation mechanism is optically thin synchrotron emission.

  15. High-energy gamma-ray observations of active galaxies

    NASA Technical Reports Server (NTRS)

    Fichtel, Carl E.

    1994-01-01

    During the period from 1992 May to early 1992 November, the Energetic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory obtained high-energy gamma-ray data for most of the sky. A total of 18 active galaxies have been seen with high certainty, and it is expected that more will be found in the data when a more thorough analysis is complete. All of those that have been seen are radio-loud quasars or BL Lacertae objects; most have already been identified as blazars. No Seyfert galaxies have been found thus far. If the spectra are represented as a power law in energy, spectral slopes ranging from approximately -1.7 to -2.4 are found. A wide range of z-values exits in the observed sample, eight having values in excess of 1.0. Time variations have been seen, with the timescale for a significant change being as short as days in at least one case. These results imply the existence of very large numbers of relativistic particles, probably close to the central object. Although a large extrapolation is required, their existence also suggests that these active galactic nuclei may be the source of the extragalactic cosmic rays.

  16. Far-Infrared Spectral Observations of the Galaxy by COBE

    SciTech Connect

    Reach, W.T.; Dwek, E.; Fixsen, D.J.; Hewagama, T.; Mather, J.C.; Shafer, R.A.; Banday, A.J.; Bennett, C.L.; Cheng, E.S.; Eplee Jr., R.E.,; Leisawi tz, D.; Lubin, P.M.; Read, S.M.; Rosen, L.P.; Shuman, F.G.D.; Smoot, G.F.; Sodroski, T.J.; Wright, E.L.

    1994-10-27

    We derive Galactic continuum spectra from 5-96 cm(-1) fromCOBE/FIRAS observations. The spectra are dominated by warm dust emission,which may be fitted with a single temperature in the range 16-21 K (fornu(2) emissivity) along each line of sight. Dust heated by the attenuatedradiation field in molecular clouds gives rise tointermediate-temperature (10-14 K) emission in the inner Galaxy only. Awidespread, very cold component (4-7 K) with optical depth that isspatially correlated with the warm component is also detected. The coldcomponent is unlikely to be due to very cold dust shielded from starlightbecause it is present at high latitude. We consider hypotheses that thecold component is due to enhanced submillimeter emissivity of the dustthat gives rise to the warm component, or that it may be due to verysmall, large, or fractal particles. Lack of substantial power above theemission from warm dust places strong constraints on the amount of coldgas in the Galaxy. The microwave sky brightness due to interstellar dustis dominated by the cold component, and its angular variation could limitour ability to discern primordial fluctuations in the cosmic microwavebackground radiation.

  17. Observational and Numerical Diagnostics of Galaxy Cluster Outer Regions

    NASA Technical Reports Server (NTRS)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Lau, E.; Roncarelli, M.; Rossetti, M.; Snowden, S. L.; Gastaldello, F.

    2011-01-01

    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 r(sub 200) 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 several recent results, we observe a steepening of the density profiles beyond approximately 0.3r(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 gas clumping are in better agreement with the observed gas distribution. We note 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 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. The general trend of steepening density around the virial radius indicates that the shallow density profiles found in several recent works were probably obtained along particular directions (e.g., filaments) and are not representative of the

  18. Observational and Numerical Diagnostics of Galaxy Cluster Outer Regions

    NASA Technical Reports Server (NTRS)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Lau, E.; Roncarelli, M.; Rossetti, M.; Snowden, S. L.; Gastaldello, F.

    2011-01-01

    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 r(sub 200) 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 several recent results, we observe a steepening of the density profiles beyond approximately 0.3r(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 gas clumping are in better agreement with the observed gas distribution. We note 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 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. The general trend of steepening density around the virial radius indicates that the shallow density profiles found in several recent works were probably obtained along particular directions (e.g., filaments) and are not representative of the

  19. Radial Gas Flows in Colliding Galaxies: Connecting Simulations and Observations

    NASA Astrophysics Data System (ADS)

    Iono, Daisuke; Yun, Min S.; Mihos, J. Christopher

    2004-11-01

    We investigate the detailed response of gas to the formation of transient and long-lived dynamical structures induced in the early stages of a disk-disk collision and identify observational signatures of radial gas inflow through a detailed examination of the collision simulation of an equal-mass bulge-dominated galaxy. Our analysis and discussion mainly focuses on the evolution of the diffuse and dense gas in the early stages of the collision, when the two disks are interacting but have not yet merged. Stars respond to the tidal interaction by forming both transient arms and long-lived m=2 bars, but the gas response is more transient, flowing directly toward the central regions within about 108 yr after the initial collision. The rate of inflow declines when more than half of the total gas supply reaches the inner few kiloparsecs, where the gas forms a dense nuclear ring inside the stellar bar. The average gas inflow rate to the central 1.8 kpc is ~7 Msolar yr-1 with a peak rate of 17 Msolar yr-1. Gas with high volume density is found in the inner parts of the postcollision disks at size scales close to the spatial resolution of the simulations, and this may be a direct result of shocks traced by the discontinuity in the gas velocity field. The evolution of gas in a bulgeless progenitor galaxy is also discussed, and a possible link to the ``chain galaxy'' population observed at high redshifts is inferred. The evolution of the structural parameters such as asymmetry and concentration of both stars and gas are studied in detail. Further, a new structure parameter (the compactness parameter K) that traces the evolution of the size scale of the gas relative to the stellar disk is introduced, and this may be a useful tracer to determine the merger chronology of colliding systems. Noncircular gas kinematics driven by the perturbation of the nonaxisymmetric structure can produce distinct emission features in the ``forbidden velocity quadrants'' of the position

  20. SATELLITES AROUND MASSIVE GALAXIES SINCE z {approx} 2: CONFRONTING THE MILLENNIUM SIMULATION WITH OBSERVATIONS

    SciTech Connect

    Quilis, Vicent; Trujillo, Ignacio

    2012-06-20

    Minor merging has been postulated as the most likely evolutionary path to produce the increase in size and mass observed in the massive galaxies since z {approx} 2. In this Letter, we directly test this hypothesis, comparing the population of satellites around massive galaxies in cosmological simulations versus the observations. We use state-of-the-art, publically available, Millennium I and II simulations, and the associated semi-analytical galaxy catalogs to explore the time evolution of the fraction of massive galaxies that have satellites, the number of satellites per galaxy, the projected distance at which the satellites locate from the host galaxy, and the mass ratio between the host galaxies and their satellites. The three virtual galaxy catalogs considered here overproduce the fraction of galaxies with satellites by a factor ranging between 1.5 and 6 depending on the epoch, whereas the mean projected distance and ratio of the satellite mass over host mass are in closer agreement with data. The larger pull of satellites in the semi-analytical samples could suggest that the size evolution found in previous hydrodynamical simulations is an artifact due to the larger number of infalling satellites compared to the real universe. These results advise us to revise the physical ingredients implemented in the semi-analytical models in order to reconcile the observed and computed fraction of galaxies with satellites, and eventually, it would leave some room for other mechanisms explaining the galaxy size growth not related to the minor merging.

  1. Gas Kinematics In and Around Edge-on Galaxies from MaNGA Observations

    NASA Astrophysics Data System (ADS)

    Bizyaev, D.

    2016-06-01

    Mapping Nearby Galaxies at APO (MaNGA) is a massive Integral Field Unit survey of a large number of relatively nearby galaxies that started in 2014 as a part of SDSS-IV at the Apache Point Observatory. After the first year of observations MaNGA has obtained IFU spectra of about a thousand of objects, with several dozens of edge-on galaxies among them. The two-dimensional spectra help us constrain parameters of galactic components with superior rotation curves. There is a significant fraction of galaxies in which the extra-planar gas emission is confidently detected. The extra-planar gas velocity fields in several galaxies show signs of lagging rotation with respect to the gas motion close to the galactic plane. We show progress of MaNGA survey in observations of edge-on galaxies and discuss their impact on our understanding of gas kinematics in and around spiral galaxies after finishing the survey.

  2. The Arecibo Galaxy Environment Survey: Observations towards the NGC 7817/7798 Galaxy Pair

    NASA Astrophysics Data System (ADS)

    Harrison, Amanda; Robert Minchin

    2016-01-01

    The Arecibo Galaxy Environment Survey (AGES) examines the environment of neutral hydrogen gas in the interstellar medium. AGES uses the 305m Arecibo Radio Telescope and the Arecibo L-Band Feed Array to create a deep field neutral hydrogen survey which we used to detect galaxies in an area five square degrees around the galaxy pair NGC 7817/7798. By finding and investigating hydrogen rich galaxies we hope to gain a better understanding of how the environment affects galaxy evolution. H1 line profiles were made for the detected H1 emission and ten galaxies which had the characteristic double-horned feature were found. NGC 7798 was not detected, but NGC 7817 and the other galaxies were cross-identified in NASA/IPAC Extragalactic Database as well as in Sloan Digital Sky Survey to obtain optical data. Out of the ten, two of the sources were uncatalogued. We analyzed the hydrogen spectra and aperture photometry to learn about the characteristics of these galaxies such as their heliocentric velocity, flux, and mass of the neutral hydrogen. Furthermore, we graphed the Tully-Fisher and the Baryonic Tully-Fisher of the ten sources and found that most followed the relation. One that is the biggest outlier is suspected be a galaxy cluster while other outliers may be caused by ram pressure stripping deforming the galaxy.

  3. Diffuse continuum gamma rays from the Galaxy observed by COMPTEL

    NASA Technical Reports Server (NTRS)

    Strong, A. W.; Bennett, K.; Bloemen, H.; Diehl, R.; Hermsen, W.; Morris, D.; Schonfelder, V.; Stacy, J. G.; De Vries, C.; Varendorff, M.

    1994-01-01

    The diffuse Galactic continuum gamma-ray emission has been studied using the full Sky Survey from COMPTEL on the Compton Observatory CGRO. The diffuse emission appears to be visible in the whole 0.75-30 MeV range covered by the instrument, although a considerable contribution from unresolved point sources cannot be excluded. A correlation analysis using HI and CO surveys of the Galaxy is used to derive the Galactic emissivity spectrum, and this is consistent with a smooth continuation to the spectrum at higher energies derived by a similar analysis of COS-B data. The apparent conversion factor from integrated CO temperature to molecular hydrogen column density can also be determined from the correlation analysis. The value obtained is consistent with results from COS-B and other non-gamma-ray methods. Calculations of the emissivity spectrum from bremsstrahlung from a cosmic-ray electron spectrum based on propagation models are compared with the observations.

  4. Near-infrared observations of IRAS minisurvey galaxies

    NASA Technical Reports Server (NTRS)

    Carico, David P.; Soifer, B. T.; Elias, J. H.; Matthews, K.; Neugebauer, G.; Beichman, C.; Persson, C. J.; Persson, S. E.

    1987-01-01

    Near infrared photometry at J, H, and K was obtained for 82 galaxies from the IRAS minisurvey. The near infrared colors of these galaxies cover a larger range in J-H and H-K than do normal field spiral galaxies, and evidence is presented of a tighter correlation between the near and far infrared emission in far infrared bright galaxies than exists between the far infrared and the visible emission. These results suggest the presence of dust in the far infrared bright galaxies, with hot dust emission contributing to the 2.2 micron emission, and extinction by dust affecting both the near infrared colors and the visible luminosities. In addition, there is some indication that the infrared emission in many of the minisurvey galaxies is coming from a strong nuclear component.

  5. Observing z > 4 Galaxies Through a Cosmic Lens

    NASA Astrophysics Data System (ADS)

    Benítez, Narciso; Broadhurst, Tom; Frye, Brenda; Lidman, Chris; King, Lindsay; Meylan, Georges; Schneider, Peter

    Practical considerations dictate two basic strategies to find very high redshift galaxies: going very deep in small fields (e.g. the HDFs) or doing shallower, wide area surveys which target the bright end of the luminosity function. A third approach which combines some of the advantages of both is to look for strongly magnified objects in the fields of lensing clusters. We present results from such an ongoing program, which has already yielded seven spectroscopically confirmed z > 4 galaxies, and several candidates to z > 6 galaxies. We also discuss the prospects for finding z ˜ 6.5 galaxies with HST and the Advanced Camera for Surveys.

  6. Interstellar Hydrogen in Galaxies: Radio observations of neutral hydrogen yield valuable information on the properties of galaxies.

    PubMed

    Roberts, M S

    1974-02-01

    Measurement of the 21-cm line radiation originating from the interstellar neutral hydrogen in a galaxy yields information on the total mass and total hydrogen content of the galaxy. The ratio of these two quantities is correlated with structural type in the sense that the later type galaxies contain a higher fraction of their total mass in the form of interstellar hydrogen This ratio is one of the few physical parameters known to correlate with structural type. It need not, however, reflect an evolutionary sequence, such as more hydrogen implying a younger galaxy. Efficiency of conversion of hydrogen to stars can just as easily explain the correlation. Except for the very latest systems, the total mass of a spiral does not appear to be correlated with type. Red shifts of galaxies measured at optical wavelengths and at 21 cm are in excellent agreement. The form of the Doppler expression has been shown to hold over a wavelength range of 5 x 105. All spirals earlier than type Ir which have been studied with adequate resolution show a central minimum in their hydrogen distribution. The region of maximum projected HI surface density occurs at some distance from the center. In the earlier type spirals the optical arms are located in the region of this maximum surface density. In the later type spirals the maximum HI density and prominent optical arms are less well correlated and, at times, are anticorrelated. Detailed studies of the HI distribution and motions within a galaxy require the high relative resolution of beam synthesis arrays. We may expect significant new information from such studies, which are now in progress. Filled-aperture telescopes will supply the necessary observations at zero spacing and vital statistical information on large numbers of galaxies, peculiar systems and groups and clusters of galaxies. The two types of telescope systems will complement one another. In the near future we should have a much better description of spiral galaxies and, we

  7. (Star)bursts of FIRE: observational signatures of bursty star formation in galaxies

    NASA Astrophysics Data System (ADS)

    Sparre, Martin; Hayward, Christopher C.; Feldmann, Robert; Faucher-Giguère, Claude-André; Muratov, Alexander L.; Kereš, Dušan; Hopkins, Philip F.

    2017-04-01

    Galaxy formation models are now able to reproduce observed relations such as the relation between galaxies' star formation rates (SFRs) and stellar masses (M*) and the stellar-mass-halo-mass relation. We demonstrate that comparisons of the short-time-scale variability in galaxy SFRs with observational data provide an additional useful constraint on the physics of galaxy formation feedback. We apply SFR indicators with different sensitivity time-scales to galaxies from the Feedback in Realistic Environments (FIRE) simulations. We find that the SFR-M* relation has a significantly greater scatter when the Hα-derived SFR is considered compared with when the far-ultraviolet (FUV)-based SFR is used. This difference is a direct consequence of bursty star formation because the FIRE galaxies exhibit order-of-magnitude SFR variations over time-scales of a few Myr. We show that the difference in the scatter between the simulated Hα- and FUV-derived SFR-M* relations at z = 2 is consistent with observational constraints. We also find that the Hα/FUV ratios predicted by the simulations at z = 0 are similar to those observed for local galaxies except for a population of low-mass (M* ≲ 109.5 M⊙) simulated galaxies with lower Hα/FUV ratios than observed. We suggest that future cosmological simulations should compare the Hα/FUV ratios of their galaxies with observations to constrain the feedback models employed.

  8. H I Imaging Observations of Superthin Galaxies. I. UGC 7321

    NASA Astrophysics Data System (ADS)

    Uson, Juan M.; Matthews, L. D.

    2003-05-01

    We have used the Very Large Array to image the isolated ``superthin'' galaxy UGC 7321 in the H I line with a spatial resolution of 16" and a spectral resolution of 24 kHz (5.2 km s-1). We have reached a sensitivity of (0.36-0.40) mJy beam-1 channel-1, which correspond to a column density of (8-9)×1018 atoms cm-2 (1 σ). UGC 7321 has a gas-rich disk, with MHI=(1.06+/-0.01)×109 d210 Msolar and MHI/LB=1.0 (d10 is the distance to UGC 7321 in units of 10 Mpc, the value adopted in this paper), and no detectable radio continuum emission (FCONT=0.41+/-0.25 mJy). The global H I distribution of UGC 7321 is rather symmetric and extends to ~1.5 times the optical radius (DHI=8.65‧+/-0.15‧ at nHI=3×1019 atoms cm-2). An ``integral sign'' warp is observed in the H I disk, commencing near the edge of the stellar distribution and twisting back toward the equatorial plane in the outermost regions. In addition, the position-velocity diagram suggests the presence of a bar or inner arm within ~40" from the center. The rotation curve of UGC 7321 is slowly rising; it reaches its asymptotic velocity of ~110 km s-1 at ~2.5‧ from the center (about 0.9 optical radii) and declines near the edge of the H I disk. The ratio of the inferred dynamical mass to the mass in gas and stars is ~12d-110, implying that UGC 7321 is a highly dark-matter-dominated galaxy.

  9. Evidence of Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-NEWTON/EPIC SPECTRUM of XTE 11650-500

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fabian, A. C.; Wunands, R.; Reynolds, C. S.; Ehle, M.; Freyberg, M. J.; VanDerKlis, M.; Lewin, W. H. G.; Sanchez-Fernandez, C.; Castro-Tirado, A. J.

    2002-01-01

    We observed the Galactic black hole candidate XTE J1650-500 early in its fall of 2001 outburst with the XMM-Newton European Photon Imaging pn Camera (EPIC-pn). The observed spectrum is consistent with the source having been in the very high state. We h d a broad, skewed Fe Kar emission line that suggests the primary in this system may be a Kerr black hole and that indicates a steep disk emissivity profile that is hard to explain in terms of a standard accretion disk model. These results are quantitatively and qualitatively similar to those from an XMM-Newton observation of the Seyfert galaxy MCG -6-30-15. The steep emissivity in MCG -6-30-15 may be explained by the extraction and dissipation of rotational energy from a black hole with nearly maximal angular momentum or from material in the plunging region via magnetic connections to the inner accretion disk. If this process is at work in both sources, an exotic but fundamental general relativistic prediction may be confirmed across a factor of l0(exp 6) in black hole mass. We discuss these results in terms of the accretion flow geometry in stellar-mass black holes and the variety of enigmatic phenomena often observed in the very high state.

  10. Evidence of Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-NEWTON/EPIC SPECTRUM of XTE 11650-500

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fabian, A. C.; Wunands, R.; Reynolds, C. S.; Ehle, M.; Freyberg, M. J.; VanDerKlis, M.; Lewin, W. H. G.; Sanchez-Fernandez, C.; Castro-Tirado, A. J.

    2002-01-01

    We observed the Galactic black hole candidate XTE J1650-500 early in its fall of 2001 outburst with the XMM-Newton European Photon Imaging pn Camera (EPIC-pn). The observed spectrum is consistent with the source having been in the very high state. We h d a broad, skewed Fe Kar emission line that suggests the primary in this system may be a Kerr black hole and that indicates a steep disk emissivity profile that is hard to explain in terms of a standard accretion disk model. These results are quantitatively and qualitatively similar to those from an XMM-Newton observation of the Seyfert galaxy MCG -6-30-15. The steep emissivity in MCG -6-30-15 may be explained by the extraction and dissipation of rotational energy from a black hole with nearly maximal angular momentum or from material in the plunging region via magnetic connections to the inner accretion disk. If this process is at work in both sources, an exotic but fundamental general relativistic prediction may be confirmed across a factor of l0(exp 6) in black hole mass. We discuss these results in terms of the accretion flow geometry in stellar-mass black holes and the variety of enigmatic phenomena often observed in the very high state.

  11. Hard X-ray observations of ultraluminous infrared galaxies

    NASA Technical Reports Server (NTRS)

    Rieke, G. H.

    1988-01-01

    X-ray flux upper limits of 2-10 keV for ultraluminous infrared galaxies were drawn from the HEAO A-1 data base. The hard X-ray luminosities of these sources are much weaker relative to their total luminosities than would be expected for Seyfert 1 galaxies or quasi-stellar objects. Because of the low level of interstellar extinction for hard X-rays, this result suggests that the ultraluminous galaxies are not powered by embedded QSOs that are otherwise similar to other QSOs. Three other possibilities are: (1) the infrared galaxies may contain a form of X-ray-quiet active nucleus; (2) the X-ray sources in active nuclei may not turn on until after the circumnuclear gas has cleared; or (3) the bulk of the infrared luminosity in these galaxies may be generated by intense circumnuclear star formation.

  12. Hard X-ray observations of ultraluminous infrared galaxies

    SciTech Connect

    Rieke, G.H.

    1988-08-01

    X-ray flux upper limits of 2-10 keV for ultraluminous infrared galaxies were drawn from the HEAO A-1 data base. The hard X-ray luminosities of these sources are much weaker relative to their total luminosities than would be expected for Seyfert 1 galaxies or quasi-stellar objects. Because of the low level of interstellar extinction for hard X-rays, this result suggests that the ultraluminous galaxies are not powered by embedded QSOs that are otherwise similar to other QSOs. Three other possibilities are: (1) the infrared galaxies may contain a form of X-ray-quiet active nucleus; (2) the X-ray sources in active nuclei may not turn on until after the circumnuclear gas has cleared; or (3) the bulk of the infrared luminosity in these galaxies may be generated by intense circumnuclear star formation. 27 references.

  13. Andromeda Galaxy

    NASA Image and Video Library

    2003-12-10

    This image is from NASA Galaxy Evolution Explorer is an observation of the large galaxy in Andromeda, Messier 31. The Andromeda galaxy is the most massive in the local group of galaxies that includes our Milky Way.

  14. Constraints on decaying dark matter from Fermi observations of nearby galaxies and clusters

    SciTech Connect

    Dugger, Leanna; Profumo, Stefano; Jeltema, Tesla E. E-mail: tesla@ucolick.org

    2010-12-01

    We analyze the impact of Fermi gamma-ray observations (primarily non-detections) of selected nearby galaxies, including dwarf spheroidals, and of clusters of galaxies on decaying dark matter models. We show that the fact that galaxy clusters do not shine in gamma rays puts the most stringent limits available to-date on the lifetime of dark matter particles for a wide range of particle masses and decay final states. In particular, our results put strong constraints on the possibility of ascribing to decaying dark matter both the increasing positron fraction reported by PAMELA and the high-energy feature in the electron-positron spectrum measured by Fermi. Observations of nearby dwarf galaxies and of the Andromeda Galaxy (M31) do not provide as strong limits as those from galaxy clusters, while still improving on previous constraints in some cases.

  15. New observations and a photographic atlas of polar-ring galaxies

    NASA Technical Reports Server (NTRS)

    Whitmore, Bradley C.; Lucas, Ray A.; Mcelroy, Douglas B.; Steiman-Cameron, Thomas Y.; Sackett, Penny D.

    1990-01-01

    A photographic atlas of polar-ring galaxies and related objects is presented. The atlas includes kinematically confirmed polar-ring galaxies (category A), good candidates based on their morphological appearance (category B), possible candidates (category C), and possibly related objects (category D). New photometric and kinematic observations are reported for several galaxies in the catalog, including observations that show that UGC 7576 and UGC 9796 ( = II ZW 73) are S0 galaxies with polar rings. Roughly 0.5 percent of all nearby S0 galaxies appear to have polar rings. When corrected for various selection effects (e.g., nonoptimal viewing orientation, possible dimming, or limited lifetime of the ring) the percentage increases to about 5 percent of S0 galaxies which have, or have had a polar ring.

  16. A Catalog of Galaxy Clusters Observed by XMM-Newton

    NASA Technical Reports Server (NTRS)

    Snowden, S. L.; Mushotzky, R. M.; Kuntz, K. D.; Davis, David S.

    2007-01-01

    Images and the radial profiles of the temperature, abundance, and brightness for 70 clusters of galaxies observed by XMM-Newton are presented along with a detailed discussion of the data reduction and analysis methods, including background modeling, which were used in the processing. Proper consideration of the various background components is vital to extend the reliable determination of cluster parameters to the largest possible cluster radii. The various components of the background including the quiescent particle background, cosmic diffuse emission, soft proton contamination, and solar wind charge exchange emission are discussed along with suggested means of their identification, filtering, and/or their modeling and subtraction. Every component is spectrally variable, sometimes significantly so, and all components except the cosmic background are temporally variable as well. The distributions of the events over the FOV vary between the components, and some distributions vary with energy. The scientific results from observations of low surface brightness objects and the diffuse background itself can be strongly affected by these background components and therefore great care should be taken in their consideration.

  17. COMPARATIVE STUDY OF ASYMMETRY ORIGIN OF GALAXIES IN DIFFERENT ENVIRONMENTS. I. OPTICAL OBSERVATIONS

    SciTech Connect

    Plauchu-Frayn, I.; Coziol, R. E-mail: rcoziol@astro.ugto.m

    2010-06-15

    This paper presents the first of two analyses about the influence of environment on the formation and evolution of galaxies observed in the nearby universe. For our study, we used three different samples representing different density environments: galaxies in Compact Groups (HCGs), Isolated Pairs of Galaxies (KPGs), and Isolated Galaxies (KIGs), which were taken as references. Usingboth characteristic isophotal parameters and evidence of asymmetries in the optical and the near-infrared, we are able to establish differences in the characteristics of galaxies with different morphologies in different environments, allowing us to better understand their different formation histories. In this first paper, we present the isophotal and asymmetry analyses of a sample of 214 galaxies in different environments observed in the optical (V and I images). For each galaxy, we have determined different characteristic isophotal parameters and V - I color profiles, as a function of semi-major axis, and performed a full asymmetry analysis in residual images using the V filter. Evidence of asymmetry in the optical is almost missing in the KIG sample and significantly more common in the KPG than in the HCG samples. Our isophotal analysis suggests that the stellar populations in the HCG galaxies are older and more dynamically relaxed than in the KPG. The HCG galaxies seem to be at a more advanced stage of interaction than the KPGs. One possible explanation is that these structures formed at different epochs: compact groups of galaxies would have formed before close pairs of galaxies, which only began interacting recently. However, similarities in the formation process of galaxies with same morphology suggest CGs and close pairs of galaxies share similar conditions; they are new structures forming relatively late in low-density environments.

  18. Ultraviolet observations of galaxies with the FAUST experiment

    NASA Technical Reports Server (NTRS)

    Deharveng, J.-M.; Sasseen, T. P.; Buat, V.; Bowyer, S.; Lampton, M.; Wu, X.

    1994-01-01

    We have used the set of point sources detected by the Far Ultraviolet Space Telescope (FAUST) instrument to identify galaxies and study the total galaxy flux in a 250 A wide band peaking at 1650 A. A sample of 144 galaxies has been obtained after cross-reference with the RC3 catalog, elimination of objects confused with stars and various corrections for the photometry. The UV-B color dispersion is found to increase while the galaxies get redder from late to early types. The irregular galaxies appear on average redder and the Sbc galaxies bluer than indicated by the spectral energy distributions currently used for the calculations of K-corrections. Various arguments lead us to make the assumption of a constant dust extinction within each galaxy. The UV flux per unit area decreases on average from late to early type spirals. We find a weak correlation between the UV and far infra-red emission while the infra-red to UV flux ratio gets lower when galaxies get bluer (as measured by the UV to B flux ratio). The UV flux per unit area correlates with the HI gas surface density and the total gas surface density when this quantity is available. The correlation with the molecular gas alone is weak. In the Virgo cluster, the UV flux per unit area does not decrease in direct proportion to the HI deficiency. Galaxy counts per square degree and per magnitude interval have been obtained at high-galactic latitudes. Combined with data at fainter magnitudes, they show a variation as a function of magnitude with a near-euclidean slope over a range of 8 magnitudes.

  19. The shape of dark matter haloes - I. H I observations of edge-on galaxies

    NASA Astrophysics Data System (ADS)

    Peters, S. P. C.; van der Kruit, P. C.; Allen, R. J.; Freeman, K. C.

    2017-01-01

    We present neutral hydrogen observations for a sample of eight nearby, late-type, edge-on galaxies. All of the galaxies have been well resolved in the radial direction, while six have also been well resolved in the vertical direction. We find that each of the galaxies has approximately the same maximum surface brightness temperature throughout its disc. We argue that self-absorption is the main cause of this phenomenon and that subsequent decompositions will require a treatment of this.

  20. LOFAR, VLA, and Chandra Observations of the Toothbrush Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    van Weeren, R. J.; Brunetti, G.; Brüggen, M.; Andrade-Santos, F.; Ogrean, G. A.; Williams, W. L.; Röttgering, H. J. A.; Dawson, W. A.; Forman, W. R.; de Gasperin, F.; Hardcastle, M. J.; Jones, C.; Miley, G. K.; Rafferty, D. A.; Rudnick, L.; Sabater, J.; Sarazin, C. L.; Shimwell, T. W.; Bonafede, A.; Best, P. N.; Bîrzan, L.; Cassano, R.; Chyży, K. T.; Croston, J. H.; Dijkema, T. J.; Enßlin, T.; Ferrari, C.; Heald, G.; Hoeft, M.; Horellou, C.; Jarvis, M. J.; Kraft, R. P.; Mevius, M.; Intema, H. T.; Murray, S. S.; Orrú, E.; Pizzo, R.; Sridhar, S. S.; Simionescu, A.; Stroe, A.; van der Tol, S.; White, G. J.

    2016-02-01

    We present deep LOFAR observations between 120 and 181 MHz of the “Toothbrush” (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of α =-0.8+/- 0.1 at the northern edge of the main radio relic, steepening toward the south to α ≈ -2. The spectral index of the radio halo is remarkably uniform (α =-1.16, with an intrinsic scatter of ≤slant 0.04). The observed radio relic spectral index gives a Mach number of { M }={2.8}-0.3+0.5, assuming diffusive shock acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock ({ M }≈ 1.2, with an upper limit of { M }≈ 1.5). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and re-acceleration at cluster merger shocks.

  1. Observations of the impact of starbursts on the interstellar medium in dwarf galaxies

    NASA Technical Reports Server (NTRS)

    Marlowe, Amanda T.; Heckman, Timothy M.; Wyse, Rosemary F. G.; Schommer, Robert

    1995-01-01

    Dwarf galaxies play a crucial role in our understanding of the formation and evolution of galaxies, and the concept of supernova-driven mass outflows is a vital ingredient in theories of the structure and evolution of dwarf galaxies. Despite the theoretical importance of these outflows, there is a very limited amount of direct observational evidence for their existence. We have therefore begun a detailed multi-wave-band search for outflows in dwarf (M(sub B) greater than or = -18) galaxies with extensive recent or ongoing centrally concentrated star formation. We report the first results of this search in the present paper. Observations of the ionized gas in dwarf amorphous galaxies with centrally concentrated populations of massive stars provide evidence for the large-scale expansion of their expansion of their ionized interstellar media. Fabry-Perot H alpha images reveal the presence of kiloparsec-scale 'superbubbles' and filaments which tend to be oriented along the galaxy minor axis. These structures are comparable in size to the chracteristic optical sizes of the galaxies, and dominate the morphology of the galaxies at low surface brightness in H alpha. Since expanding structure of this size and velocity are not observed in all low-mass galaxies with recent or ongoing star formation, we suggest that we are witnessing transient events that likely have a relatively low 'duty cycle' in such galaxies. That is, we argue that the particular galaxies in the present paper have had significantly elevated star formation rates over the past 10(exp 7)-10(exp 8) yr (i.e., these are starburst or young poststarburst systems). This interpretation is consistent with the optical colors and emission-line properties of these galaxies.

  2. Observations of the impact of starbursts on the interstellar medium in dwarf galaxies

    NASA Technical Reports Server (NTRS)

    Marlowe, Amanda T.; Heckman, Timothy M.; Wyse, Rosemary F. G.; Schommer, Robert

    1995-01-01

    Dwarf galaxies play a crucial role in our understanding of the formation and evolution of galaxies, and the concept of supernova-driven mass outflows is a vital ingredient in theories of the structure and evolution of dwarf galaxies. Despite the theoretical importance of these outflows, there is a very limited amount of direct observational evidence for their existence. We have therefore begun a detailed multi-wave-band search for outflows in dwarf (M(sub B) greater than or = -18) galaxies with extensive recent or ongoing centrally concentrated star formation. We report the first results of this search in the present paper. Observations of the ionized gas in dwarf amorphous galaxies with centrally concentrated populations of massive stars provide evidence for the large-scale expansion of their expansion of their ionized interstellar media. Fabry-Perot H alpha images reveal the presence of kiloparsec-scale 'superbubbles' and filaments which tend to be oriented along the galaxy minor axis. These structures are comparable in size to the chracteristic optical sizes of the galaxies, and dominate the morphology of the galaxies at low surface brightness in H alpha. Since expanding structure of this size and velocity are not observed in all low-mass galaxies with recent or ongoing star formation, we suggest that we are witnessing transient events that likely have a relatively low 'duty cycle' in such galaxies. That is, we argue that the particular galaxies in the present paper have had significantly elevated star formation rates over the past 10(exp 7)-10(exp 8) yr (i.e., these are starburst or young poststarburst systems). This interpretation is consistent with the optical colors and emission-line properties of these galaxies.

  3. The observed peripheral growth of disc galaxies from z ~ 1

    NASA Astrophysics Data System (ADS)

    Gadotti, Dimitri A.; Sachdeva, Sonali; Saha, Kanak; Singh, Harinder P.

    2017-03-01

    Using images from the Hubble Space Telescope and Sloan Digital Sky Survey, we have computed both parametric and non-parametric measures, and examined the evolution in size, concentration, stellar mass, effective stellar mass density and asymmetry for a sample of 600 disc galaxies from z ~ 1 till z ~ 0. We find that disc galaxies have gained more than 50 per cent of their present stellar mass over the last 8 Gyr. Also, the increase in disc size is found to be peripheral. While the average total (Petrosian) radius almost doubles from z ~ 1 to z ~ 0, the average effective (half-light) radius undergoes a marginal increase in comparison. This indicates that galaxies grow more substantially in their outskirts, and is consistent with the inside-out growth picture. The substantial increase in mass and size indicates that accretion of external material has been a dominant mode of galaxy growth, where the circumgalactic environment plays a significant role.

  4. MAGPHYS: a publicly available tool to interpret observed galaxy SEDs

    NASA Astrophysics Data System (ADS)

    da Cunha, Elisabete; Charlot, Stéphane; Dunne, Loretta; Smith, Dan; Rowlands, Kate

    2012-08-01

    We present a simple, physically-motivated model to interpret consistently the emission from galaxies at ultraviolet, optical and infrared wavelengths. We combine this model with a Bayesian method to obtain robust statistical constraints on key parameters describing the stellar content, star formation activity and dust content of galaxies. Our model is now publicly available via a user-friendly code package, MAGPHYS at www.iap.fr/magphys. We present an application of this model to interpret a sample of ~1400 local (z<0.5) galaxies from the H-ATLAS survey. We find that, for these galaxies, the diffuse interstellar medium, powered mainly by stars older than 10 Myr, accounts for about half the total infrared luminosity. We discuss the implications of this result to the use of star formation rate indicators based on total infrared luminosity.

  5. IUE and Einstein observations of the LINER galaxy NGC 4579

    NASA Technical Reports Server (NTRS)

    Reichert, G. A.; Puchnarewicz, E. M.; Mason, K. O.

    1990-01-01

    Results of International Ultraviolet Explorer (IUE) and Einstein observations of the LINER galaxy NGC 4579 are reported. Spatial profiles of the long wavelength IUE emission show a two component structure, with an unresolved core superimposed on broader underlying emission. The core spectrum shows strong C II lambda 2326 and broad Mg II lambda 2800 emission, and perhaps emission due to blends of Fe II multiplets (2300 to 23600 angstrom). The short wavelength emission is spatially unresolved, and shows C II lambda 1335, C III lambda 1909 broad C IV lambda 1550 emission, and a broad feature at approximately 1360 angstrom which may be due to 0.1 lambda 1356. Contrary to previous reports no evidence for He II lambda 1640 is found in the spectrum. An unresolved x ray source is detected at the location of the nucleus; its spectrum is well fitted by a power law of energy slope alpha approximately -0.5. These results further support the idea that NGC 4579 may contain a dwarf Seyfert nucleus.

  6. 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.

  7. Gas density histograms of galaxies: the observational density probability function of the interstellar gas density

    NASA Astrophysics Data System (ADS)

    Toshihiro, Handa; Takahiro, Yoda; Nario, Kuno

    2015-03-01

    In the steady state, the probability density function (PDF) of the gaseous interstellar matter (ISM) can be observed as a gas density histogram (GDH) of all cells in the system. We made GDHs of the Milky Way Galaxy (MWG) using Galactic plane surveys in CO lines. We found that the GDH in the MWG is log-normal which suggests that the density structure of the molecular gas is a result of many stochastic processes. Using the Nobeyama CO atlas, we made GDHs of nearby galaxies but in column density. Although some galaxies show log-normal, the others show completely different shapes, suggesting that the density structure of galaxies may be different from galaxy to galaxy.

  8. Characterizing Clumpy Structure of z 2 Galaxies in HST Observations from CANDELS and Hydrodynamical Simulations

    NASA Astrophysics Data System (ADS)

    Mozena, Mark; Faber, S. M.; Primack, J. R.; Dekel, A.; Ceverino, D.; Koo, D. C.; Fumagalli, M.; Wuyts, S.; Rosario, D. J.; Lai, K.; Kocevski, D. D.; McGrath, E. J.; Trump, J. R.; CANDELS

    2011-01-01

    The first data from the HST Multi-Cycle Treasury CANDELS (Cosmic Assembly Near Infra-red Deep Extragalactic Legacy Survey - candels.ucolick.org) are producing images of thousands of z 2 galaxies in observed optical (ACS) and NIR (WFC3) bands. We have developed a new visual classification scheme for z 2 galaxies which is motivated by the significant population of galaxies that are dominated by giant clumps in the HST images, and by the theoretical predictions for clumpy galaxies based on analytic studies and zoom-in hydrodynamical cosmological simulations. This classification method was developed using about a thousand z 2 galaxies in the GOODS-S Early Release Survey (ERS) region imaged with ACS and WFC3. The ERS data have been observed in a way similar to the CANDELS observations. I will also discuss the latest cosmologically motivated ART hydrodynamical simulations by Ceverino, Dekel, and Primack. We render these simulated z 2 galaxies to mimic our HST ACS and WFC3 images and visually classify their stellar structure to compare them with the galaxies observed in ERS. We have compared the effects of dust extinction due to the complex clumpy distribution of gas within these simulations. Comparing the visual classification of the HST observations with the simulations provides new clues to galaxy assembly.

  9. CO observations of nearby galaxies and the efficiency of star formation

    NASA Technical Reports Server (NTRS)

    Young, Judith S.

    1987-01-01

    The CO distributions and total molecular content of 160 galaxies were observed using the 14 meter millimeter telescope of the FCRAO. For the luminous, relatively face-on Sc galaxies, the azimuthally averaged CO distributions are centrally peaked, while for the Sb and Sa galaxies the Co distributions often exhibit central CO holes up to 5 kpc across. None of the Sc galaxies have CO distributions which resemble the Milky Way. A general correlation was found between total CO and IR luminosities in galaxies. The scatter in this relation is highly correlated with dust temperature. No strong correlation of IR luminosities was found with HI masses, and it was thereby concluded that the infrared emission is more directly tied to the molecular content of galaxies. It is suggested that galaxies which have high Star Formation Effiencies (SFEs) produce more stars per unit molecular mass, thereby increasing the average temperature of the dust in the star forming regions. Irregular galaxies and galaxies previously identified as mergers have the highest observed star formation efficiencies. For the mergers, evidence was found that the IR/CO luminosity ratio increases with the merger age estimated by Joseph and Wright (1985).

  10. UNIFICATION SCHEME OF RADIO GALAXIES AND QUASARS FALSIFIED BY THEIR OBSERVED SIZE DISTRIBUTIONS

    SciTech Connect

    Singal, Ashok K.; Singh, Raj Laxmi

    2013-03-20

    In the currently popular orientation-based unified scheme, a radio galaxy appears as a quasar when its principal radio-axis happens to be oriented within a certain cone opening angle around the observer's line of sight. Due to geometrical projection, the observed sizes of quasars should therefore appear smaller than those of radio galaxies. We show that this simple, unambiguous prediction of the unified scheme is not borne out by the actually observed angular sizes of radio galaxies and quasars. Except in the original 3CR sample, based on which the unified scheme was proposed, in other much larger samples no statistically significant difference is apparent in the size distributions of radio galaxies and quasars. The population of low-excitation radio galaxies with apparently no hidden quasars inside, which might explain the observed excess number of radio galaxies at low redshifts, cannot account for the absence of any foreshortening of the sizes of quasars at large redshifts. On the other hand, from infrared and X-ray studies, there is evidence of a hidden quasar within a dusty torus in many radio galaxies, at z > 0.5. It is difficult to reconcile this with the absence of foreshortening of quasar sizes at even these redshifts, and perhaps one has to allow that the major radio axis may not have anything to do with the optical axis of the torus. Otherwise, to resolve the dichotomy of radio galaxies and quasars, a scheme quite different from the present might be required.

  11. ROSAT Observations of Low Mass Disk Galaxies: No Evidence of Baryonic Blow Out

    NASA Technical Reports Server (NTRS)

    Bothun, Gregory D.; Eriksen, James

    1994-01-01

    To test the hypothesis that galctic winds associated with star formation in low mass disk galaxies can be an effective means of relocating cold disk gas to a warm tenuous halo, we have obtained long exposure ROSAT PSPC observations of three such galaxies.

  12. ROSAT Observations of Low Mass Disk Galaxies: No Evidence of Baryonic Blow Out

    NASA Technical Reports Server (NTRS)

    Bothun, Gregory D.; Eriksen, James

    1994-01-01

    To test the hypothesis that galctic winds associated with star formation in low mass disk galaxies can be an effective means of relocating cold disk gas to a warm tenuous halo, we have obtained long exposure ROSAT PSPC observations of three such galaxies.

  13. A UNIFIED EMPIRICAL MODEL FOR INFRARED GALAXY COUNTS BASED ON THE OBSERVED PHYSICAL EVOLUTION OF DISTANT GALAXIES

    SciTech Connect

    Bethermin, Matthieu; Daddi, Emanuele; Sargent, Mark T.; Elbaz, David; Mullaney, James; Pannella, Maurilio; Hezaveh, Yashar; Le Borgne, Damien; Buat, Veronique; Charmandaris, Vassilis; Lagache, Guilaine; Scott, Douglas

    2012-10-01

    We reproduce the mid-infrared to radio galaxy counts with a new empirical model based on our current understanding of the evolution of main-sequence (MS) and starburst (SB) galaxies. We rely on a simple spectral energy distribution (SED) library based on Herschel observations: a single SED for the MS and another one for SB, getting warmer with redshift. Our model is able to reproduce recent measurements of galaxy counts performed with Herschel, including counts per redshift slice. This agreement demonstrates the power of our 2-Star-Formation Modes (2SFM) decomposition in describing the statistical properties of infrared sources and their evolution with cosmic time. We discuss the relative contribution of MS and SB galaxies to the number counts at various wavelengths and flux densities. We also show that MS galaxies are responsible for a bump in the 1.4 GHz radio counts around 50 {mu}Jy. Material of the model (predictions, SED library, mock catalogs, etc.) is available online.

  14. IRAS high resolution studies and modeling of closely interacting galaxies. Galaxy collisions: Infrared observations and analysis of numerical models. UV spectroscopy of massive young stellar populations in interacting galaxies

    NASA Technical Reports Server (NTRS)

    Lamb, Susan A.

    1993-01-01

    The Final Technical Report covering the period from 15 Aug. 1989 to 14 Aug. 1991 is presented. Areas of research included Infrared Astronomy Satellite (IRAS) high resolution studies and modeling of closely interacting galaxies; galaxy collisions: infrared observations and analysis of numerical models; and UV spectroscopy of massive young stellar populations in interacting galaxies. Both observational studies and theoretical modelling of interacting galaxies are covered. As a consequence the report is divided into two parts, one on each aspect of the overall project.

  15. Gas flows in galactic nuclei: Observational constraints on the co-evolution of SMBHs and galaxies

    NASA Astrophysics Data System (ADS)

    Garcia-Burillo, Santiago

    2015-08-01

    Galaxy nuclei are a unique laboratory to study gas flows. High-resolution imaging of the gas flows in galactic nuclei are instrumental in the study of the fueling and the feedback of star formation and nuclear activity in nearby galaxies. Several fueling mechanisms can be now confronted in detail with observations done with state of the art interferometers like ALMA. Furthermore, the study of gas flows in galactic nuclei can probe the feedback of activity on the energy balance/redistribution of the interstellar medium of galaxies. Feedback action from star formation and AGN activity is invoked to prevent galaxies from becoming overly massive , but also to explain scaling laws like BH-bulge mass correlations and the bimodal color distribution of galaxies. This close relationship between galaxies and their central SMBH can be described as 'co-evolution'. There is mounting observational evidence for the existence of gas outflows in different populations of starbursts and active galaxies, a manifestation of the feedback of activity. The outflow phenomenon concerns virtually all the phases of the interstellar medium (ISM).In this talk I will summarize the main results recently obtained from the observation of galactic inflows and outflows in a variety of active galaxies with current millimeter interferometers like ALMA or the IRAM array. I will also discuss recent results on the study of sptially-resolved SF laws in AGN hosts.

  16. Panchromatic observations of dwarf starburst galaxies: Infant super star clusters and a low-luminosity AGN

    NASA Astrophysics Data System (ADS)

    Reines, Amy Ellen

    2011-01-01

    Globular star clusters and supermassive black holes are fundamental components of today's massive galaxies, with origins dating back to the very early universe. Both globular clusters and the seeds of supermassive black holes are believed to have formed in the progenitors of modern massive galaxies, although the details are poorly understood. Direct observations of these low-mass, distant, and hence faint systems are unobtainable with current capabilities. However, gas-rich dwarf starburst galaxies in the local universe, analogous in many ways to protogalaxies at high-redshift, can provide critical insight into the early stages of galaxy evolution including the formation of globular clusters and massive black holes. This thesis presents a panchromatic study of nearby dwarf starburst galaxies harboring nascent globular clusters still embedded in their birth material. Infant clusters are identified via their production of thermal radio emission at centimeter wavelengths, which comes from dense gas ionized by young massive stars. By combining radio observations with complementary data at ultraviolet, optical and infrared wavelengths, we obtain a comprehensive view of massive clusters emerging from their gaseous and dusty birth cocoons. This thesis also presents the first example of a nearby dwarf starburst galaxy hosting an actively accreting massive central black hole. The black hole in this dwarf galaxy is unusual in that it is not associated with a bulge, a nuclear star cluster, or any other well-defined nucleus, likely reflecting an early phase of black hole and galaxy evolution that has not been previously observed.

  17. The Observability of Abundance Ratio Effects in Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Serven, J. L.; Worthey, G.; Briley, M. M.

    2004-12-01

    Using synthetic spectra we construct a simple model of an elliptical galaxy, with a velocity dispersion σ = 200 km s-1. Absorption feature indices are defined for C, N, O, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba, and Eu as a first step in determining the abundances of these elements in stellar populations, such as elliptical galaxies, for which integrated light spectra are available. Then using these indices and assuming a photon error such that S/N = 100 around 5000 Å , the feasibility of measuring individual elements in real galaxies is assessed. Of the elements studied only S, K, Cu, Zn, and Eu appear to be difficult to determine; the rest appear to be at least feasible.

  18. Using galaxy formation simulations to optimize LIGO follow-up observations

    NASA Astrophysics Data System (ADS)

    Antolini, Elisa; Caiazzo, Ilaria; Davé, Romeel; Heyl, Jeremy S.

    2017-04-01

    The recent discovery of gravitational radiation from merging black holes poses a challenge of how to organize the electromagnetic follow-up of gravitational-wave events as well as observed bursts of neutrinos. We propose a technique to select the galaxies that are most likely to host the event given some assumptions of whether the particular event is associated with recent star formation, low-metallicity stars or simply proportional to the total stellar mass in the galaxy. We combine data from the 2-MASS Photometric Redshift Galaxy Catalogue with results from galaxy formation simulations to develop observing strategies that potentially reduce the area of sky to search by up to a factor of 2 relative to an unweighted search of galaxies, and a factor of 20 to a search over the entire LIGO localization region.

  19. A comparison between observed and analytical velocity dispersion profiles of 20 nearby galaxy clusters

    NASA Astrophysics Data System (ADS)

    Khan, Mohammad S.; Abdullah, Mohamed H.; Ali, Gamal B.

    2014-05-01

    We derive analytical expression for the velocity dispersion of galaxy clusters, using the statistical mechanical approach. We compare the observed velocity dispersion profiles for 20 nearby ( z≤0.1) galaxy clusters with the analytical ones. It is interesting to find that the analytical results closely match with the observed velocity dispersion profiles only if the presence of the diffuse matter in clusters is taken into consideration. This takes us to introduce a new approach to detect the ratio of diffuse mass, M diff , within a galaxy cluster. For the present sample, the ratio f= M diff / M, where M the cluster's total mass is found to has an average value of 45±12 %. This leads us to the result that nearly 45 % of the cluster mass is impeded outside the galaxies, while around 55 % of the cluster mass is settled in the galaxies.

  20. Observing the Earliest Galaxies: Looking for the Sources of Reionization

    NASA Astrophysics Data System (ADS)

    Illingworth, Garth

    2015-04-01

    Systematic searches for the earliest galaxies in the reionization epoch finally became possible in 2009 when the Hubble Space Telescope was updated with a powerful new infrared camera during the final Shuttle servicing mission SM4 to Hubble. The reionization epoch represents the last major phase transition of the universe and was a major event in cosmic history. The intense ultraviolet radiation from young star-forming galaxies is increasingly considered to be the source of the photons that reionized intergalactic hydrogen in the period between the ``dark ages'' (the time before the first stars and galaxies at about 100-200 million years after the Big Bang) and the end of reionization around 800-900 million years. Yet finding and measuring the earliest galaxies in this era of cosmic dawn has proven to a challenging task, even with Hubble's new infrared camera. I will discuss the deep imaging undertaken by Hubble and the remarkable insights that have accrued from the imaging datasets taken over the last decade on the Hubble Ultra-Deep Field (HUDF, HUDF09/12) and other regions. The HUDF datasets are central to the story and have been assembled into the eXtreme Deep Field (XDF), the deepest image ever from Hubble data. The XDF, when combined with results from shallower wide-area imaging surveys (e.g., GOODS, CANDELS) and with detections of galaxies from the Frontier Fields, has provided significant insights into the role of galaxies in reionization. Yet many questions remain. The puzzle is far from being fully solved and, while much will done over the next few years, the solution likely awaits the launch of JWST. NASA/STScI Grant HST-GO-11563.

  1. CANDELS: THE CONTRIBUTION OF THE OBSERVED GALAXY POPULATION TO COSMIC REIONIZATION

    SciTech Connect

    Finkelstein, Steven L.; Pawlik, Andreas H.; Papovich, Casey; Ryan, Russell E.; Ferguson, Henry C.; Koekemoer, Anton M.; Grogin, Norman A.; Dickinson, Mark; Finlator, Kristian; Giavalisco, Mauro; Cooray, Asantha; Dunlop, James S.; Faber, Sandy M.; Kocevski, Dale D.

    2012-10-20

    We present measurements of the specific ultraviolet luminosity density from a sample of 483 galaxies at 6 {approx}< z {approx}< 8. These galaxies were selected from new deep near-infrared Hubble Space Telescope imaging from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, Hubble UltraDeep Field 2009, and Wide Field Camera 3 Early Release Science programs. We investigate the contribution to reionization from galaxies that we observe directly, thus sidestepping the uncertainties inherent in complementary studies that have invoked assumptions regarding the intrinsic shape or the faint-end cutoff of the galaxy ultraviolet (UV) luminosity function. Due to our larger survey volume, wider wavelength coverage, and updated assumptions about the clumping of gas in the intergalactic medium (IGM), we find that the observable population of galaxies can sustain a fully reionized IGM at z = 6, if the average ionizing photon escape fraction (f {sub esc}) is {approx}30%. Our result contrasts with a number of previous studies that have measured UV luminosity densities at these redshifts that vary by a factor of five, with many concluding that galaxies could not complete reionization by z = 6 unless a large population of galaxies fainter than the detection limit were invoked, or extremely high values of f {sub esc} were present. The specific UV luminosity density from our observed galaxy samples at z = 7 and 8 is not sufficient to maintain a fully reionized IGM unless f {sub esc} > 50%. We examine the contribution from galaxies in different luminosity ranges and find that the sub-L* galaxies we detect are stronger contributors to the ionizing photon budget than the L > L* population, unless f {sub esc} is luminosity dependent. Combining our observations with constraints on the emission rate of ionizing photons from Ly{alpha} forest observations at z = 6, we find that we can constrain f {sub esc} < 34% (2{sigma}) if the observed galaxies are the only contributors to

  2. HST Observations of the Host Galaxy of GRB970508

    NASA Astrophysics Data System (ADS)

    Fruchter, A.; Pian, E.

    1998-08-01

    The field of GRB970508 was imaged by HST with the STIS CCD in open filter mode (50CCD) on 1998 August 5.78-6.03 for a total exposure time of 11,568 seconds. An extended object, which we believe to be the host galaxy of GRB970508, was detected at the astrometric position of the optical transient of GRB970508. The galaxy has high signal-to-noise in our data and is clearly resolved, with a major axis of approximately 0."5 .

  3. Low X-Ray Luminosity Galaxy Clusters: Main Goals, Sample Selection, Photometric and Spectroscopic Observations

    NASA Astrophysics Data System (ADS)

    Nilo Castellón, José Luis; Alonso, M. Victoria; García Lambas, Diego; Valotto, Carlos; O'Mill, Ana Laura; Cuevas, Héctor; Carrasco, Eleazar R.; Ramírez, Amelia; Astudillo, José M.; Ramos, Felipe; Jaque Arancibia, Marcelo; Ulloa, Natalie; Órdenes, Yasna

    2016-06-01

    We present our study of 19 low X-ray luminosity galaxy clusters (L{}X ˜ 0.5-45 × 1043 erg s-1), selected from the ROSAT Position Sensitive Proportional Counters Pointed Observations and the revised version of Mullis et al. in the redshift range of 0.16-0.7. This is the introductory paper of a series presenting the sample selection, photometric and spectroscopic observations, and data reduction. Photometric data in different passbands were taken for eight galaxy clusters at Las Campanas Observatory; three clusters at Cerro Tololo Interamerican Observatory; and eight clusters at the Gemini Observatory. Spectroscopic data were collected for only four galaxy clusters using Gemini telescopes. Using the photometry, the galaxies were defined based on the star-galaxy separation taking into account photometric parameters. For each galaxy cluster, the catalogs contain the point-spread function and aperture magnitudes of galaxies within the 90% completeness limit. They are used together with structural parameters to study the galaxy morphology and to estimate photometric redshifts. With the spectroscopy, the derived galaxy velocity dispersion of our clusters ranged from 507 km s-1 for [VMF98]022 to 775 km s-1 for [VMF98]097 with signs of substructure. Cluster membership has been extensively discussed taking into account spectroscopic and photometric redshift estimates. In this sense, members are the galaxies within a projected radius of 0.75 Mpc from the X-ray emission peak and with clustercentric velocities smaller than the cluster velocity dispersion or 6000 km s-1, respectively. These results will be used in forthcoming papers to study, among the main topics, the red cluster sequence, blue cloud and green populations, the galaxy luminosity function, and cluster dynamics.

  4. Molecular line observations of infrared dark clouds in the galaxy

    NASA Astrophysics Data System (ADS)

    Finn, Susanna C.

    Although massive stars play many important roles in the universe, their formation is poorly understood. Recently, a class of interstellar clouds known as Infrared Dark Clouds (IRDCs) has been identified as likely progenitors of massive stars and clusters. These clouds are dense (nH 2 > 105 cm--3), cold (T < 20 K), have very high column densities (N ˜ 1023--10 25 cm--2), and contain dense clumps and cores. In this dissertation, I present radio observations of a large sample of IRDCs in order to examine their properties and explore the hypothesis that high-mass stars and clusters form in these dense, cold molecular clouds. I determine kinematic distances to a large sample of IRDCs in the inner Galaxy based on CS (2--1) radial velocities. IRDCs are concentrated at specific Galactocentric radii and their distribution appears to trace Milky Way spiral structure. To identify IRDC clumps and determine properties such as mass, size, and chemical evolution, I map a sample of IRDCs in various high density-tracing molecular transitions. The size and mass estimates show that IRDC clumps are comparable in size to more evolved regions of massive star formation. I compare the integrated intensities and linewidths of the molecular emission with a proposed evolutionary sequence of the clumps. The ratio of N2H + with HNC, HCN, and HCO+ is a function of evolutionary stage. The linewidths and virial parameters of the clumps show no clear trend with the evolutionary sequence. Finally, I explore the filamentary shape of IRDCs. The "sausage instability," which describes clumps forming in a gas cylinder, is explored as a mechanism for star-forming clumps to collapse in filaments. First, I compare observations of the "Nessie Nebula," an extreme case of a filamentary IRDC, with predictions from the theory of the fluid instability and then expand the sample to other filamentary IRDCs. The observations are consistent with theoretical predictions of clump spacing, clump masses, and linear

  5. GAS INFLOW AND OUTFLOW HISTORIES IN DISK GALAXIES AS REVEALED FROM OBSERVATIONS OF DISTANT STAR-FORMING GALAXIES

    SciTech Connect

    Toyouchi, Daisuke; Chiba, Masashi

    2015-09-01

    We investigate gas inflow and outflow histories in Milky Way-like disk galaxies, to get new insights into the baryonic processes in galaxy formation and evolution. For this purpose, we solve the equations for the evolution of the surface mass densities of gas and metals at each radius in a galactic disk, based on the observed structural properties of distant star-forming galaxies, including the redshift evolution of their stellar mass distribution, their scaling relation between the mass of baryonic components, star formation rate (SFR), and chemical abundance, as well as the supposed evolution of their radial metallicity gradients (RMGs). We find that the efficiency of gas inflow for a given SFR decreases with time and that the inflow rate is always nearly proportional to the SFR. For gas outflow, although its efficiency for a given SFR is a decreasing function of time, similar to gas inflow, the outflow rate is not necessarily proportional to the SFR and the relation between the outflow rate and SFR strongly depends on the evolution of the adopted RMG. We also find that the results on the outflow rate can be reproduced in the framework of a momentum-driven (energy-driven) wind mechanism if the RMG is steepening (flattening) with time. Therefore if the well-measured RMGs and their evolution for Milky Way-like galaxies are obtained from future observations, then our results will be useful to constrain the main driving mechanism for their galactic outflows.

  6. NIR SPECTROSCOPIC OBSERVATION OF MASSIVE GALAXIES IN THE PROTOCLUSTER AT z = 3.09

    SciTech Connect

    Kubo, Mariko; Yamada, Toru; Ichikawa, Takashi; Kajisawa, Masaru; Matsuda, Yuichi; Tanaka, Ichi

    2015-01-20

    We present the results of near-infrared spectroscopic observations of the K-band-selected candidate galaxies in the protocluster at z = 3.09 in the SSA22 field. We observed 67 candidates with K {sub AB} < 24 and confirmed redshifts of the 39 galaxies at 2.0 < z {sub spec} < 3.4. Of the 67 candidates, 24 are certainly protocluster members with 3.04 ≤ z {sub spec} ≤ 3.12, which are massive red galaxies that have been unidentified in previous optical observations of the SSA22 protocluster. Many distant red galaxies (J – K {sub AB} > 1.4), hyper extremely red objects (J – K {sub AB} > 2.1), Spitzer MIPS 24 μm sources, active galactic nuclei (AGNs) as well as the counterparts of Lyα blobs and the AzTEC/ASTE 1.1 mm sources in the SSA22 field are also found to be protocluster members. The mass of the SSA22 protocluster is estimated to be ∼2-5 × 10{sup 14} M {sub ☉}, and this system is plausibly a progenitor of the most massive clusters of galaxies in the current universe. The reddest (J – K {sub AB} ≥ 2.4) protocluster galaxies are massive galaxies with M {sub star} ∼ 10{sup 11} M {sub ☉} showing quiescent star formation activities and plausibly dominated by old stellar populations. Most of these massive quiescent galaxies host moderately luminous AGNs detected by X-ray. There are no significant differences in the [O III] λ5007/Hβ emission line ratios and [O III] λ5007 line widths and spatial extents of the protocluster galaxies from those of massive galaxies at z ∼ 2-3 in the general field.

  7. NIR Spectroscopic Observation of Massive Galaxies in the Protocluster at z = 3.09

    NASA Astrophysics Data System (ADS)

    Kubo, Mariko; Yamada, Toru; Ichikawa, Takashi; Kajisawa, Masaru; Matsuda, Yuichi; Tanaka, Ichi

    2015-01-01

    We present the results of near-infrared spectroscopic observations of the K-band-selected candidate galaxies in the protocluster at z = 3.09 in the SSA22 field. We observed 67 candidates with K AB < 24 and confirmed redshifts of the 39 galaxies at 2.0 < z spec < 3.4. Of the 67 candidates, 24 are certainly protocluster members with 3.04 <= z spec <= 3.12, which are massive red galaxies that have been unidentified in previous optical observations of the SSA22 protocluster. Many distant red galaxies (J - K AB > 1.4), hyper extremely red objects (J - K AB > 2.1), Spitzer MIPS 24 μm sources, active galactic nuclei (AGNs) as well as the counterparts of Lyα blobs and the AzTEC/ASTE 1.1 mm sources in the SSA22 field are also found to be protocluster members. The mass of the SSA22 protocluster is estimated to be ~2-5 × 1014 M ⊙, and this system is plausibly a progenitor of the most massive clusters of galaxies in the current universe. The reddest (J - K AB >= 2.4) protocluster galaxies are massive galaxies with M star ~ 1011 M ⊙ showing quiescent star formation activities and plausibly dominated by old stellar populations. Most of these massive quiescent galaxies host moderately luminous AGNs detected by X-ray. There are no significant differences in the [O III] λ5007/Hβ emission line ratios and [O III] λ5007 line widths and spatial extents of the protocluster galaxies from those of massive galaxies at z ~ 2-3 in the general field.

  8. What Do We Learn from IRAC Observations of Galaxies at 2 < z < 3.5?

    NASA Astrophysics Data System (ADS)

    Wuyts, Stijn; Labbé, Ivo; Franx, Marijn; Rudnick, Gregory; van Dokkum, Pieter G.; Fazio, Giovanni G.; Förster Schreiber, Natascha M.; Huang, Jiasheng; Moorwood, Alan F. M.; Rix, Hans-Walter; Röttgering, Huub; van der Werf, Paul

    2007-01-01

    We analyze very deep HST, VLT, and Spitzer photometry of galaxies at 2galaxies. Galaxies with red rest-frame U-V colors are generally red in rest-frame V-J as well. However, at a given U-V color a range in V-J colors exists, and we show that this allows us to distinguish young, dusty galaxies from old, passively evolving galaxies. We quantify the effects of IRAC photometry on estimates of masses, ages, and the dust content of z>2 galaxies. The estimated distributions of these properties do not change significantly when IRAC data are added to the UBVIJHK photometry. However, for individual galaxies the addition of IRAC can improve the constraints on the stellar populations, especially for red galaxies: uncertainties in stellar mass decrease by a factor of 2.7 for red [(U-V)rest>1] galaxies, but only by a factor of 1.3 for blue [(U-V)rest<1] galaxies. We find a similar color dependence of the improvement for estimates of age and dust extinction. In addition, the improvement from adding IRAC depends on the availability of full NIR JHK coverage; if only K band were available, the mass uncertainties of blue galaxies would decrease by a more substantial factor of 1.9. Finally, we find that a trend of galaxy color with stellar mass is already present at z>2. The most massive galaxies at high redshift have red rest-frame U-V colors compared to lower mass galaxies, even when allowing for complex star formation histories. Based on observations with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through contract 125790 issued by JPL at Caltech. Based on service-mode observations collected at

  9. VLBA Observations of Low Luminosity Flat Spectrum Radio Galaxies and BL Lac Objects: Polarisation Properties

    NASA Astrophysics Data System (ADS)

    Bondi, M.; Dallacasa, D.; Stanghellini, C.; Marchã, M. J. M.

    We obtained two-epoch VLBA observations at 5 GHz of a list of radio galaxies drawn from the 200 mJy sample (Marcha et al. 1996). The objects selected for milli-arcsecond scale observations are classified, on the basis of their optical spectroscopic and polarimetric properties, as BL Lac objects, normal weak line radio galaxies, broad line radio galaxies, and transition objects (those with intermediate properties). We present preliminary results on the radio polarization properties, on the milli-arcsecond scale, of objects with different optical properties and discuss structural variations detected from the two epochs.

  10. Integral field observations of the blue compact galaxy Haro14. Star formation and feedback in dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Cairós, L. M.; González-Pérez, J. N.

    2017-04-01

    Context. Low-luminosity, gas-rich blue compact galaxies (BCG) are ideal laboratories to investigate the triggering and propagation of star formation in galaxies, the effects of massive stellar feedback within a shallow gravitational potential, and the enrichment of the interstellar medium. Aims: We aim to probe the morphology, stellar content, and kinematics, along with the nebular excitation and ionization mechanism, in the BCG Haro 14 by means of integral field observations. Methods: We observed Haro 14 at the Very Large Telescope, working with the Visible Multi-Object Spectrograph. From these data we build maps in continuum and in the brighter emission lines, produce line-ratio maps (interstellar extinction, density, and diagnostic-line ratios), and obtain the velocity and velocity dispersion fields. We also generate the integrated spectrum of the major H ii regions and young stellar clusters identified in the maps to determine reliable physical parameters and oxygen abundances. Results: We find as follows: i) the current star formation in Haro 14 is spatially extended with the major H ii regions placed along a linear (chain-like) structure, elongated in the north-south direction, and in a horseshoe-like curvilinear feature that extends about 760 pc eastward; the continuum emission is more concentrated and peaks close to the galaxy center; ii) two different episodes of star formation are present in the central galaxy regions: the recent starburst, with ages ≤6 Myr and the intermediate-age clusters, with ages between 10 and 30 Myr; these stellar components rest on a several Gyr old underlying host galaxy; iii) the Hα/Hβ pattern is inhomogeneous, with excess color values varying from E(B-V) = 0.04 up to E(B-V) = 1.09; iv) shocks play a significant role in the galaxy; and v) the velocity field displays a complicated pattern with regions of material moving toward us in the east and north galaxy areas. Conclusions: The morphology of Haro 14, its irregular

  11. IRTF Observations of Lensed Star-Forming Galaxies Identified in the SDSS Imaging Data

    NASA Astrophysics Data System (ADS)

    Allyn Smith, J.; Allam, S. S.; Tucker, D. L.; Lin, H.; SDSS Bright Arcs Search Team

    2009-12-01

    The SDSS Bright Arcs Search Team (see poster by H. Lin et al. #478.02) has been carrying out an ongoing systematic search for bright, strongly-lensed, high-redshift galaxies in samples of SDSS luminous red galaxies, clusters, and interacting/merging galaxy pairs. So far we have spectroscopically confirmed a dozen lensing systems, with source galaxy redshifts z = 0.4 - 2.7, with 6 of these among the brightest known z > 2 lensed galaxies, including the 8 O'Clock Arc (Allam et al. 2007) and the Clone (Lin et al. 2008). Here, we report on our JHK imaging of several of these confirmed lensed systems based upon observations taken with the SpeX and NSFCAM2 on the NASA Infrared Telescope Facility. Further, we discuss our future plans for NIR imaging of this sample.

  12. A Sneak Peek at the JWST Era: Observing Galaxies Below the Hubble Limit with Gravitational Lensing

    NASA Astrophysics Data System (ADS)

    Livermore, Rachael C.

    2016-01-01

    The installation of WFC3 on the Hubble Space Telescope pushed the frontier of high-redshift galaxy studies to only 500 Myr after the Big Bang. However, observations in this epoch remain challenging and are limited to the brightest galaxies; the fainter sources believed to be responsible for reionizing the Universe remain beyond the grasp of Hubble. With gravitational lensing, however, we can benefit from the magnification of faint sources, which brings them within reach of today's telescopes. The Hubble Frontier Fields program is a deep survey of strongly lensing clusters observed in the optical and near-infrared. Unfortunately, detecting highly magnified, intrinsically faint galaxies in these fields has proved challenging due to the bright foregound cluster galaxies and intracluster light. We have developed a technique using wavelet decomposition to overcome these difficulties and detect galaxies at z~7 with intrinsic UV magnitudes as faint as MUV = -13. We present this method and the resulting luminosity functions, which support a steep faint-end slope extending out to the observational limits. Our method has uncovered hundreds of galaxies at z > 6 fainter than any that have been seen before, providing our first insight into the small galaxy population during the epoch of reionization and a preview of the capabilities of JWST.

  13. THE OBSERVED RELATION BETWEEN STELLAR MASS, DUST EXTINCTION, AND STAR FORMATION RATE IN LOCAL GALAXIES

    SciTech Connect

    Zahid, H. J.; Kewley, L. J.; Kudritzki, R. P.; Yates, R. M.

    2013-02-15

    In this study, we investigate the relation between stellar mass, dust extinction, and star formation rate (SFR) using {approx}150,000 star-forming galaxies from SDSS DR7. We show that the relation between dust extinction and SFR changes with stellar mass. For galaxies at the same stellar mass, dust extinction is anti-correlated with the SFR at stellar masses <10{sup 10} M {sub Sun }. There is a sharp transition in the relation at a stellar mass of 10{sup 10} M {sub Sun }. At larger stellar masses, dust extinction is positively correlated with the SFR for galaxies at the same stellar mass. The observed relation between stellar mass, dust extinction, and SFR presented in this study helps to confirm similar trends observed in the relation between stellar mass, metallicity, and SFR. The relation reported in this study provides important new constraints on the physical processes governing the chemical evolution of galaxies. The correlation between SFR and dust extinction for galaxies with stellar masses >10{sup 10} M {sub Sun} is shown to extend to the population of quiescent galaxies suggesting that the physical processes responsible for the observed relation between stellar mass, dust extinction, and SFR may be related to the processes leading to the shutdown of star formation in galaxies.

  14. Galaxy pairs in the Sloan Digital Sky Survey - VIII. The observational properties of post-merger galaxies

    NASA Astrophysics Data System (ADS)

    Ellison, Sara L.; Mendel, J. Trevor; Patton, David R.; Scudder, Jillian M.

    2013-11-01

    In order to investigate the effects of galaxy mergers throughout the interaction sequence, we present a study of 10 800 galaxies in close pairs and a smaller sample of 97 post-mergers identified in the Sloan Digital Sky Survey. We find that the average central star formation rate (SFR) enhancement (×3.5) and the fraction of starbursts (20 per cent) peak in the post-merger sample. The post-mergers also show a stronger deficit in gas phase metallicity than the closest pairs, being more metal-poor than their control by -0.09 dex. Combined with the observed trends in SFR and the time-scales predicted in merger simulations, we estimate that the post-mergers in our sample have undergone coalescence within the last few hundred Myr. In contrast with the incidence of star-forming galaxies, the frequency of active galactic nuclei (AGN) peaks in the post-mergers, outnumbering AGN in the control sample by a factor of 3.75. Moreover, amongst the galaxies that host an AGN, the black hole accretion rates in the closest pairs and post-mergers are higher by a factor of ˜3 than AGN in the control sample. These results are consistent with a picture in which star formation is initiated early on in the encounter, with AGN activity peaking post-coalescence.

  15. HALO GAS AND GALAXY DISK KINEMATICS DERIVED FROM OBSERVATIONS AND LAMBDACDM SIMULATIONS OF Mg II ABSORPTION-SELECTED GALAXIES AT INTERMEDIATE REDSHIFT

    SciTech Connect

    Kacprzak, Glenn G.; Murphy, Michael T.; Churchill, Christopher W.; Ceverino, Daniel; Klypin, Anatoly; Steidel, Charles C. E-mail: mmurphy@astro.swin.edu.a E-mail: ceverino@nmsu.ed E-mail: ceverino@phys.huji.ac.i

    2010-03-10

    We obtained ESI/Keck rotation curves of 10 Mg II absorption-selected galaxies (0.3 <= z <= 1.0) for which we have WFPC-2/HST images and high-resolution HIRES/Keck and UVES/VLT quasar spectra of the Mg II absorption profiles. We perform a kinematic comparison of these galaxies and their associated halo Mg II absorption. For all 10 galaxies, the majority of the absorption velocities lie in the range of the observed galaxy rotation velocities. In 7/10 cases, the absorption velocities reside fully to one side of the galaxy systemic velocity and usually align with one arm of the rotation curve. In all cases, a constant rotating thick-disk model poorly reproduces the full spread of observed Mg II absorption velocities when reasonably realistic parameters are employed. In 2/10 cases, the galaxy kinematics, star formation surface densities, and absorption kinematics have a resemblance to those of high-redshift galaxies showing strong outflows. We find that Mg II absorption velocity spread and optical depth distribution may be dependent on galaxy inclination. To further aid in the spatial-kinematic relationships of the data, we apply quasar absorption-line techniques to a galaxy (v{sub c} = 180 km s{sup -1}) embedded in LAMBDACDM simulations. In the simulations, Mg II absorption selects metal-enriched 'halo' gas out to {approx}100 kpc from the galaxy, tidal streams, filaments, and small satellite galaxies. Within the limitations inherent in the simulations, the majority of the simulated Mg II absorption arises in the filaments and tidal streams and is infalling toward the galaxy with velocities between -200 km s{sup -1} <= v{sub r} <= -180 km s{sup -1}. The Mg II absorption velocity offset distribution (relative to the simulated galaxy) spans {approx}200 km s{sup -1} with the lowest frequency of detecting Mg II at the galaxy systematic velocity.

  16. Extracting cosmological and evolutionary parameters from distant galaxy observations

    NASA Astrophysics Data System (ADS)

    Bruzual, Gustavo A.

    Models of the galaxy number counts and color distribution in SA 68 (Koo 1986) built according to a non-negative least squares (NNLS) algorithm (Lawson and Hanson 1974) are discussed. The value of chi(red) squared that characterizes each model can be used as a goodness of fit indicator to decide in favor of a model over another, providing an objective and unbiased criterion to extract cosmological and evolutionary parameters from a data set.

  17. Infrared observations of the spiral galaxy NGC 891

    NASA Astrophysics Data System (ADS)

    Whaley, Cynthia

    2007-08-01

    This thesis is a detailed, multi-waveband study of the inner 14 kpc of the famous spiral galaxy, NCG 891. The primary data have come from the Infrared Space Observatory's Camera. These data are images of the galaxy in 9 different mid-infrared wavebands. We have supported these data with archived data from the Spitzer Infrared Array Camera in 4 similar wavebands. Surface brightness contour maps of the galaxy were created and examined to determine where the mid-infrared emitters are located with respect to the galactic plane. We have determined that the main mid-infrared emission, due to warm dust and PAHs, lies in a thin disk of width 700 - 800 pc, but has faint emission that reaches up to about 2.3 kpc into the halo. The infrared spectral energy distribution (SED) for four environments in NGC 891 were created from the above mentioned wavebands as well as measurements from Spitzer's Multiband Imaging Photometer (3 Far-Infrared wavebands), the Two Micron All Sky Survey J, H, and K near-infrared wavebands, and the Sub- millimeter Common User Bolometer Array 450 and 850 mm bands. These spectra were fit with a SED model created by Frederic Galliano, and the physical properties of these environments were computed. The maps and SED show that while there is a relatively large amount of dust in NGC 891's halo, there is a depletion of PAHs beyond 2.3 kpc from the mid-plane. This is only the fourth galaxy to date that has PAH emission discovered in the halo, and it is the first in which the SED has been modeled for the halo.

  18. CCD surface photometry of field galaxies. I - Observations

    NASA Technical Reports Server (NTRS)

    Kent, S. M.

    1984-01-01

    Images of 105 galaxies selected from a larger complete sample of intrinsically luminous galaxies have been obtained for the purpose of computing surface brightness profiles. The intensity profiles along the major and minor axes are computed by a method in which elliptical contours whose position angle and ellipticity are allowed to vary with radius are fitted to the true isophotes of a galaxy. The resulting profiles and ellipse parameters are listed for each object. An extensive comparison of the present photometry with that of other workers is made to assess the reliability of the data. For most objects, additional photometric information is given, including an isophotal radius and magnitude within a limiting isophote of 24.0 mag/sq arcsec, an approximate total magnitude, the effective radius containing one-half the total light, and the mean surface brightness inside this radius. A full analysis of the data is deferred to a second paper where the profiles will be decomposed into bulge and disk components.

  19. High-resolution Velocity Fields of Low-mass Disk Galaxies. I. CO Observations

    NASA Astrophysics Data System (ADS)

    Truong, Phuongmai N.; Newman, Andrew B.; Simon, Joshua D.; Blitz, Leo; Ellis, Richard; Bolatto, Alberto

    2017-07-01

    This paper is the first in a series whose aim is to examine the relative distributions of dark and baryonic matter as a function of star formation history in a representative sample of low-mass disk galaxies. In this paper, we present high-resolution 12CO(J=1\\to 0) interferometry for a sample of 26 nearby dwarf galaxies that were obtained from the Combined Array for Research in Millimeter-wave Astronomy (CARMA). Among these 26 galaxies, 14 have good CO detections, including 6 galaxies previously detected in single-dish CO measurements and 8 newly detected ones. We find a linear correlation between the CO flux and the mid- and far-IR flux from the WISE and IRAS catalogs. Compared to the far-IR flux, the mid-IR flux may be a better indication of whether a galaxy contains sufficient CO for detection at the level of instrument sensitivity of CARMA. This correlation might prove to be useful in future studies to help choosing other CO targets for observation. The median molecular mass (including helium) of our galaxies is 2.8× {10}8 {M}⊙ , which is consistent with past observations for dwarf galaxies. The molecular content is weakly correlated with the dynamical mass, r-band luminosity and size of the galaxies. The median ratios of molecular mass versus dynamical mass and molecular mass versus r-band luminosity are {M}{mol}/{M}{dyn}≈ 0.035 and {M}{mol}/{L}r≈ 0.078 {M}⊙ /{L}r,⊙ , respectively, which are also consistent with past observations for dwarf galaxies.

  20. OBSERVATIONAL CONSTRAINTS ON THE MOLECULAR GAS CONTENT IN NEARBY STARBURST DWARF GALAXIES

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dalcanton, Julianne J.; Weisz, Daniel R.; Williams, Benjamin F.; Dolphin, Andrew E.; Cannon, John M.; Holtzman, Jon

    2012-06-01

    Using star formation histories derived from optically resolved stellar populations in 19 nearby starburst dwarf galaxies observed with the Hubble Space Telescope, we measure the stellar mass surface densities of stars newly formed in the bursts. By assuming a star formation efficiency (SFE), we then calculate the inferred gas surface densities present at the onset of the starbursts. Assuming an SFE of 1%, as is often assumed in normal star-forming galaxies, and assuming that the gas was purely atomic, translates to very high H I surface densities ({approx}10{sup 2}-10{sup 3} M{sub Sun} pc{sup -2}), which are much higher than have been observed in dwarf galaxies. This implies either higher values of SFE in these dwarf starburst galaxies or the presence of significant amounts of H{sub 2} in dwarfs (or both). Raising the assumed SFEs to 10% or greater (in line with observations of more massive starbursts associated with merging galaxies), still results in H I surface densities higher than observed in 10 galaxies. Thus, these observations appear to require that a significant fraction of the gas in these dwarf starbursts galaxies was in the molecular form at the onset of the bursts. Our results imply molecular gas column densities in the range 10{sup 19}-10{sup 21} cm{sup -2} for the sample. In the galaxies where CO observations have been made, these densities correspond to values of the CO-H{sub 2} conversion factor (X{sub CO}) in the range >(3-80) Multiplication-Sign 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -1}, or up to 40 Multiplication-Sign greater than Galactic X{sub CO} values.

  1. ROSAT observations of quiescent low mass disk galaxies: No evidence of baryonic blow out

    NASA Technical Reports Server (NTRS)

    Bothun, Gregory D.; Eriksen, James; Schombert, James M.

    1994-01-01

    To test the hypothesis that galactic winds associated with star formation in low mass disk galaxies can be an effective means of relocating cold disk gas to a warm tenuous halo, we have obtained long exposure ROSAT Position Sensitive Proportional Counter (PSPC) observations of three such galaxies. The sensitivity of the PSPC to the presence of an extended, approximately 0.15 KEV halo of 10(exp 9) solar mass of gas, is quite high for the exposure times we used. We failed to detect this halo in all three cases and the observed x-ray luminosity of the galaxy is two orders of magnitude less than the hypothetical case in which the mass of gas that has been expelled by previous generations of star formation is equal to the stellar mass of the galaxy itself. This limit is much less than the actual mass of cold gas in these galaxies. Thus, we were unable to verify directly the presence of significant galactic winds in these three galaxies either because they are not operative, because their halos are not sufficiently massive to aid in the retention of this gas, or because the amount of injected gas is just a small percentage of the cold disk gas. If the latter reason is emblematic of low mass galaxies then we would not expect the detection of halos. We also report here the serendipitous detection of Abell 1560, a distance class 7 cluster of unknown redshift.

  2. Radio continuum and far-infrared observations of low surface brightness galaxies

    NASA Technical Reports Server (NTRS)

    Hoeppe, G.; Brinks, E.; Klein, U.; Giovanardi, C.; Altschuler, D. R.; Price, R. M.; Deeg, H. -J.

    1994-01-01

    We present Very Large Array (VLA) radio continuum and Infrared Astronomy Satellite (IRAS) far-infrared (FIR) observations of 16 low luminosity galaxies of mostly low surface brightness. All galaxies had previously claimed single dish radio continuum detections. However, at the frequencies of our observations (1.49 and 8.48 GHz), we find significant radio emission for two objects only. We show that the other previously claimed detections are due to confusion with physically unrelated background sources. This implies a low radio continuum detection rate for these galaxies. Re-reduced IRAS scans yield significant far-infrared flux densities in at least one IRAS band for 6 of the 16 galaxies. These, together with the FIR and radio continuum upper limits, are consistent with the well established radio/FIR relation, where most of our galaxies populate the low-luminosity end. From the radio continuum and FIR flux densities and their upper limits we estimate the current star formation rates and demonstrate that the galaxies are currently passive in forming stars, in agreement with previous optical investigations. There is an indication that the galaxies were forming stars more intensively averaged over their lifetime than they are presently.

  3. ROSAT observations of quiescent low mass disk galaxies: No evidence of baryonic blow out

    NASA Technical Reports Server (NTRS)

    Bothun, Gregory D.; Eriksen, James; Schombert, James M.

    1994-01-01

    To test the hypothesis that galactic winds associated with star formation in low mass disk galaxies can be an effective means of relocating cold disk gas to a warm tenuous halo, we have obtained long exposure ROSAT Position Sensitive Proportional Counter (PSPC) observations of three such galaxies. The sensitivity of the PSPC to the presence of an extended, approximately 0.15 KEV halo of 10(exp 9) solar mass of gas, is quite high for the exposure times we used. We failed to detect this halo in all three cases and the observed x-ray luminosity of the galaxy is two orders of magnitude less than the hypothetical case in which the mass of gas that has been expelled by previous generations of star formation is equal to the stellar mass of the galaxy itself. This limit is much less than the actual mass of cold gas in these galaxies. Thus, we were unable to verify directly the presence of significant galactic winds in these three galaxies either because they are not operative, because their halos are not sufficiently massive to aid in the retention of this gas, or because the amount of injected gas is just a small percentage of the cold disk gas. If the latter reason is emblematic of low mass galaxies then we would not expect the detection of halos. We also report here the serendipitous detection of Abell 1560, a distance class 7 cluster of unknown redshift.

  4. 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.

  5. HST/ACS observations of shell galaxies: inner shells, shell colours and dust

    NASA Astrophysics Data System (ADS)

    Sikkema, G.; Carter, D.; Peletier, R. F.; Balcells, M.; Del Burgo, C.; Valentijn, E. A.

    2007-06-01

    Context: Shells in Elliptical Galaxies are faint, sharp-edged features, believed to provide evidence for a merger event. Accurate photometry at high spatial resolution is needed to learn on presence of inner shells, population properties of shells, and dust in shell galaxies. Aims: Learn more about the origin of shells and dust in early type galaxies. Methods: V-I colours of shells and underlying galaxies are derived, using HST Advanced Camera for Surveys (ACS) data. A galaxy model is made locally in wedges and subtracted to determine shell profiles and colours. We applied Voronoi binning to our data to get smoothed colour maps of the galaxies. Comparison with N-body simulations from the literature gives more insight to the origin of the shell features. Shell positions and dust characteristics are inferred from model galaxy subtracted images. Results: The ACS images reveal shells well within the effective radius in some galaxies (at 0.24 re = 1.7 kpc in the case of NGC 5982). In some cases, strong nuclear dust patches prevent detection of inner shells. Most shells have colours which are similar to the underlying galaxy. Some inner shells are redder than the galaxy. All six shell galaxies show out of dynamical equilibrium dust features, like lanes or patches, in their central regions. Our detection rate for dust in the shell ellipticals is greater than that found from HST archive data for a sample of normal early-type galaxies, at the 95% confidence level. Conclusions: The merger model describes better the shell distributions and morphologies than the interaction model. Red shell colours are most likely due to the presence of dust and/or older stellar populations. The high prevalence and out of dynamical equilibrium morphologies of the central dust features point towards external influences being responsible for visible dust features in early type shell galaxies. Inner shells are able to manifest themselves in relatively old shell systems. Based on observations made

  6. Kinematic signatures of AGN feedback in moderately powerful radio galaxies at z ~ 2 observed with SINFONI

    NASA Astrophysics Data System (ADS)

    Collet, C.; Nesvadba, N. P. H.; De Breuck, C.; Lehnert, M. D.; Best, P.; Bryant, J. J.; Hunstead, R.; Dicken, D.; Johnston, H.

    2016-02-01

    relatively low, up to AV ~ 2 mag. The ratio of line widths, σ, to bulk velocity, v, is so large that even the gas in galaxies with regular velocity fields is unlikely to be gravitationally bound. It is unclear, however, whether the large line widths are due to turbulence or unresolved, local outflows as are sometimes observed at low redshifts. We compare our sources with sets of radio galaxies at low and high redshift, finding that they may have more in common with gas-rich nearby radio galaxies with similar jet power than with the most powerful high-z radio galaxies. Comparison of the kinetic energy with the energy supply from the AGNs through jet and radiation pressure suggests that the radio source still plays a dominant role for feedback, consistent with low-redshift radio-loud quasars. Based on observations carried out with the Very Large Telescope of ESO under Program IDs 084.A-0324 and 085.A-0897, and at ATCA under Program ID C2604.

  7. 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.

  8. Radio observations confirm young stellar populations in local analogues to z ˜ 5 Lyman break galaxies

    NASA Astrophysics Data System (ADS)

    Greis, Stephanie M. L.; Stanway, Elizabeth R.; Levan, Andrew J.; Davies, Luke J. M.; Eldridge, J. J.

    2017-09-01

    We present radio observations at 1.5 GHz of 32 local objects selected to reproduce the physical properties of z ∼ 5 star-forming galaxies. We also report non-detections of five such sources in the sub-millimetre. We find a radio-derived star formation rate that is typically half than that derived from H α emission for the same objects. These observations support previous indications that we are observing galaxies with a young dominant stellar population, which has not yet established a strong supernova-driven synchrotron continuum. We stress caution when applying star formation rate calibrations to stellar populations younger than 100 Myr. We calibrate the conversions for younger galaxies, which are dominated by a thermal radio emission component. We improve the size constraints for these sources, compared to previous unresolved ground-based optical observations. Their physical size limits indicate very high star formation rate surface densities, several orders of magnitude higher than the local galaxy population. In typical nearby galaxies, this would imply the presence of galaxy-wide winds. Given the young stellar populations, it is unclear whether a mechanism exists in our sources that can deposit sufficient kinetic energy into the interstellar medium to drive such outflows.

  9. Observational Constraints on Reddening and Diffuse Interstellar Bands in Early Epoch Galaxies

    NASA Astrophysics Data System (ADS)

    Lawton, Brandon L.; Churchill, C. W.; York, B. A.; Ellison, S. L.; Snow, T. P.; Rupke, D. S.; Veilleux, S.; Johnson, R. A.; Ryan, S. G.

    2007-12-01

    The diffuse interstellar bands (DIBs) are absorption profiles thought to be due to organic molecules such as polycyclic aromatic hydrocarbons. These molecules are ubiquitous in the Galaxy and may be of astrobiological importance. Observations of DIBs in the Galaxy are fairly mature and increasing rapidly in the Magellanic Clouds; however, studies of DIBs in other extragalactic sources are rare. We present a survey of DIBs in hydrogen (HI) rich galaxies known as damped Lyman-alpha (DLAs) systems and starbursting galaxies. These galaxies allow us to test the strengths of the DIBs in environments with varying amounts of gas, metallicity, reddening, and ionizing radiation. Understanding the environmental factors that enhance or inhibit the DIBs will give insight into the types of galaxies and cosmological epochs where these organic molecules arise. We have DIB limits in six DLAs and DIB detections in the DLA with the highest HI content (z=0.5). The results suggest that DIBs in DLAs do not follow the Galactic HI-DIB relation, but they are not inconsistent with the DIBs in the Magellanic Clouds. Reddening is an important environmental factor for DIBs in DLAs. Our detection is consistent with the Galactic reddening-DIB relation. The limits indicate that DLAs are low in reddening suggesting that the environments of DLAs are not conducive to sustaining the organics that produce the DIBs. We also present preliminary findings of DIBs in 19 starbursting galaxies. Starbursting galaxies have significant reddening suggesting that DIBs may be more plentiful in starbursting galaxies than DLAs. Detections of DIBs in the z=0.5 DLA proves that the organics responsible for the DIBs existed in the Universe 5 billion years ago. More observations will allow us to determine the evolution of DIBs in cosmic time. Brandon Lawton acknowledges the support of NASA via the GSRP fellowship which helped fund this research dissertation.

  10. A Multi-wavelength Study of Nearby Galaxies Based on Molecular Line Surveys: MIPS Observations

    NASA Astrophysics Data System (ADS)

    Fazio, Giovanni; Wang, Zhong; Bush, Stephanie; Cox, Thomas J.; Keto, Eric; Pahre, Michael; Rosolowsky, Erik; Smith, Howard

    2008-03-01

    Dense molecular gas, warm dust, and hot ionized gas are different components of the multi-step transformation of cold gas into stars and star clusters. While empirical laws on star formation in galaxies have been established based on global measurements of these components, substantial galaxy-to-galaxy variations still exist and remain unexplained. To understand the mechanisms that induce and regulate star formation and thus galaxy evolution, we need to study processes on the local scales of typical star forming regions and giant molecular clouds. In a set of pilot studies, we analyzed the Spitzer and Galex data of nearby giant spirals M31, M33 and M99, and compared with the new interferometric CO maps of matching angular resolution. We found evidence that variations in local condition, environmental effects, and viewing geometry may explain much of the large scatter in the empirical relationships. Based on the success of this initial investigation, we have collected high- resolution CO images of 63 late-type galaxies from several large surveys, and we are working on obtaining a complete set of Spitzer and Galex data for these galaxies. A companion Spitzer archival research program will re-examine the existing observations along with CO, HI, UV and optical data, focusing on correlations in spatially resolved, individual star-forming regions. Here we propose MIPS imaging of the 11 galaxies in our CO sample that have not already been observed by Spitzer. A GO proposal will request IRAC time for these galaxies, which are a significant addition to our study because they substantially increase the fraction of gas-rich late types in the full sample. Insight from this program will be applicable to not only nearby system, but also high red-shift galaxies for which only integrated quantities are measurable.

  11. Jellyfish: Observational Properties of Extreme Ram-Pressure Stripping Events in Massive Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Conor, McPartland; Ebeling, Harald; Roediger, Elke

    2015-08-01

    We investigate the physical origin and observational signatures of extreme ram-pressure stripping (RPS) in 63 massive galaxy clusters at z=0.3-0.7, based on data in the F606W passband obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope. Using a training set of a dozen ``jellyfish" galaxies identified earlier in the same imaging data, we define quantitative morphological criteria to select candidate galaxies which are similar to known cases of RPS. Considering a sample of 16 ``jellyfish" galaxies (10 of which we present for the first time), we visually derive estimates of the projected direction of motion based on dynamical features such as apparent compression shocks and debris trails. Our findings suggest that the observed events occur primarily at large distances from the cluster core and involve infall trajectories featuring high impact parameters. Simple models of cluster growth show that such trajectories are consistent with two scenarios: 1) galaxy infall along filaments; and 2) infall at high velocities (≥1000 km/s) characteristic of cluster mergers. The observed distribution of events is best described by timescales of ˜few Myr in agreement with recent numerical simulations of RPS. The broader areal coverage of the Hubble Frontier Fields should provide an even larger sample of RPS events to determine the relative contributions of infall and cluster mergers. Prompted by the discovery of several jellyfish galaxies whose brightness in the F606W passband rivals or exceeds that of the respective brightest cluster galaxy, we attempt to constrain the luminosity function of galaxies undergoing RPS. The observed significant excess at the bright end compared to the luminosity functions of blue cluster members strongly suggests enhanced star formation, thus challenging theoretical and numerical studies according to which RPS merely displaces existing star-forming regions. In-depth studies of individual objects will help test our

  12. Einstein SSS+MPC observations of Seyfert type galaxies

    NASA Technical Reports Server (NTRS)

    Holt, S. S.; Turner, T. J.; Mushotzky, R. F.; Weaver, K.

    1989-01-01

    The X-ray spectra of 27 Seyfert galaxies measured with the Solid State Spectrometer (SSS) onboard the Einstein Observatory is investigated. This new investigation features the utilization of simultaneous data from the Monitor Proportional Counter (MPC) and automatic correction for systematic effects in the SSS. The new results are that the best-fit single power law indices agree with those previously reported, but that soft excesses are inferred for at least 20 percent of the measured spectra. The soft excesses are consistent with either an approximately 0.25 keV black body or Fe-L line emission.

  13. Ultraviolet Galaxy Counts From STIS Observations of The Hubble Deep Fields

    NASA Technical Reports Server (NTRS)

    Gardner, J. P.; Brown, T. M.; Ferguson, H. C.; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    We present galaxy counts in the near and far ultraviolet (NUV and FUV) obtained from Space Telescope Imaging Spectrograph (STIS) observations of portions of the Hubble Deep Field North, (HDFN), the Hubble Deep Field South, (HDFS) and a parallel field near the HDFN. All three fields have deep (AB>29) optical imaging, and we determine magnitudes by taking the ultraviolet flux detected within the limiting optical isophote. An analysis of the UV-optical colors of detected objects, combined with a visual inspection of the UV images, indicates that there are no detectable objects in the UV images which are not also detected in the optical. We measure the detection area and completeness as a function of magnitude by taking the size-magnitude distribution of galaxies in the entire HDFN WFPC2 V+I image, applying the measured UV-optical colors from the detected galaxies, and determining the total area over which each galaxy would have been detected in the UV images. The average area for the simulated galaxies in each UV magnitude bin, (including galaxies which would not be detected at all), provides the effective area and completeness for the bin. We test this procedure with Monte Carlo simulations. The galaxy counts reach to AB=29 in both the NUV and FUV; 1 magnitude fainter than the HDF F30OW counts, and 7 magnitudes fainter than balloon-based counts. We compare our measured counts to various models.

  14. Ultraviolet Galaxy Counts From STIS Observations of The Hubble Deep Fields

    NASA Technical Reports Server (NTRS)

    Gardner, J. P.; Brown, T. M.; Ferguson, H. C.; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    We present galaxy counts in the near and far ultraviolet (NUV and FUV) obtained from Space Telescope Imaging Spectrograph (STIS) observations of portions of the Hubble Deep Field North, (HDFN), the Hubble Deep Field South, (HDFS) and a parallel field near the HDFN. All three fields have deep (AB>29) optical imaging, and we determine magnitudes by taking the ultraviolet flux detected within the limiting optical isophote. An analysis of the UV-optical colors of detected objects, combined with a visual inspection of the UV images, indicates that there are no detectable objects in the UV images which are not also detected in the optical. We measure the detection area and completeness as a function of magnitude by taking the size-magnitude distribution of galaxies in the entire HDFN WFPC2 V+I image, applying the measured UV-optical colors from the detected galaxies, and determining the total area over which each galaxy would have been detected in the UV images. The average area for the simulated galaxies in each UV magnitude bin, (including galaxies which would not be detected at all), provides the effective area and completeness for the bin. We test this procedure with Monte Carlo simulations. The galaxy counts reach to AB=29 in both the NUV and FUV; 1 magnitude fainter than the HDF F30OW counts, and 7 magnitudes fainter than balloon-based counts. We compare our measured counts to various models.

  15. The EDGE-CALIFA Survey: Interferometric Observations of 126 Galaxies with CARMA

    NASA Astrophysics Data System (ADS)

    Bolatto, Alberto D.; Wong, Tony; Utomo, Dyas; Blitz, Leo; Vogel, Stuart N.; Sánchez, Sebastián F.; Barrera-Ballesteros, Jorge; Cao, Yixian; Colombo, Dario; Dannerbauer, Helmut; García-Benito, Rubén; Herrera-Camus, Rodrigo; Husemann, Bernd; Kalinova, Veselina; Leroy, Adam K.; Leung, Gigi; Levy, Rebecca C.; Mast, Damián; Ostriker, Eve; Rosolowsky, Erik; Sandstrom, Karin M.; Teuben, Peter; van de Ven, Glenn; Walter, Fabian

    2017-09-01

    We present interferometric CO observations, made with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer, of galaxies from the Extragalactic Database for Galaxy Evolution survey (EDGE). These galaxies are selected from the Calar Alto Legacy Integral Field Area (CALIFA) sample, mapped with optical integral field spectroscopy. EDGE provides good-quality CO data (3σ sensitivity {{{Σ }}}{mol}∼ 11 {M}ȯ {{pc}}-2 before inclination correction, resolution ∼1.4 kpc) for 126 galaxies, constituting the largest interferometric CO survey of galaxies in the nearby universe. We describe the survey and data characteristics and products, then present initial science results. We find that the exponential scale lengths of the molecular, stellar, and star-forming disks are approximately equal, and galaxies that are more compact in molecular gas than in stars tend to show signs of interaction. We characterize the molecular-to-stellar ratio as a function of Hubble type and stellar mass and present preliminary results on the resolved relations between the molecular gas, stars, and star-formation rate. We then discuss the dependence of the resolved molecular depletion time on stellar surface density, nebular extinction, and gas metallicity. EDGE provides a key data set to address outstanding topics regarding gas and its role in star formation and galaxy evolution, which will be publicly available on completion of the quality assessment.

  16. Evolution of magnetic fields in galaxies and future observational tests with the Square Kilometre Array

    NASA Astrophysics Data System (ADS)

    Arshakian, T. G.; Beck, R.; Krause, Marita; Sokoloff, D.

    2009-01-01

    Aims: In the context of models of galaxy formation and evolution, we investigate the cosmological evolution of large- and small-scale magnetic fields inside galaxies. Methods: We use the dynamo theory to derive the timescales of amplification and ordering of magnetic fields in disk and puffy galaxies. Turbulence in protogalactic halos generated by thermal virialization can drive an efficient turbulent dynamo. Results from simulations of hierarchical structure formation cosmology provide a tool to develop an evolutionary model of regular magnetic fields coupled with galaxy formation and evolution. Results: The turbulent (small-scale) dynamo was able to amplify a weak seed magnetic field in halos of protogalaxies to a few μG strength within a few 108 yr. This turbulent field served as a seed to the mean-field (large-scale) dynamo. Galaxies similar to the Milky Way formed their disks at z≈10 and regular fields of μG strength and a few kpc coherence length were generated within 2 Gyr (at z≈3), but field-ordering on the coherence scale of the galaxy size required an additional 6 Gyr (at z≈0.5). Giant galaxies formed their disks at z≈10, allowing more efficient dynamo generation of strong regular fields (with kpc coherence length) already at z≈4. However, the age of the Universe is short for fully coherent fields in giant galaxies larger than 15 kpc to have been achieved. Dwarf galaxies should have hosted fully coherent fields at z≈1. After a major merger, the strength of the turbulent field is enhanced by a factor of a few. Conclusions: This evolutionary scenario can be tested by measurements of polarized synchrotron emission and Faraday rotation with the planned Square Kilometre Array (SKA). We predict an anticorrelation between galaxy size and ratio between ordering scale and galaxy size. Weak regular fields (small Faraday rotation) in galaxies at z⪉3 are signatures of major mergers. Undisturbed dwarf galaxies should host fully coherent fields, giving

  17. Determining the Hubble Constant from Gravitational-wave Observations of Merging Binary Neutron Stars and Electromagnetic Observations of Galaxies

    NASA Astrophysics Data System (ADS)

    Qi, Hong; Brady, Patrick; Pankow, Chris; Kaplan, David; van Sistine, Angela

    2017-01-01

    Active research has been made in the past few decades on measuring the Hubble constant H0. Most of the research use electromagnetic observations only. In our research, we propose a different method of determining the Hubble constant more accurately with both electromagnetic observations of galaxies and gravitational-wave observations of signals that happen in these galaxies. Our method is based on the method proposed by Bernard Schutz in 1986, in which one uses information from galaxy surveys as prior information for the location of a gravitational wave source. Since the first direct detection of gravitational waves in 2015, this approach has been made more supported and useful. We show how accurate we can constrain H0 by combining the results from a couple of hundreds of simulated gravitational-wave observations of merging binary neutron stars from a network of two advanced interferometers. This accuracy will be expectedly dramatically improved when we use a network of three advanced detectors. We also show various systematic effects on the measurements of H0 due to the incompleteness of galaxy catalog, the uncertainty in the measurements of the redshifts of galaxies, and so forth. We will also review the ongoing work.

  18. Giant Clumps in Star-forming Galaxies at z>1 in CANDELS Observations and CANDElized Simulations

    NASA Astrophysics Data System (ADS)

    Guo, Yicheng; Closson Ferguson, Henry; Ravindranath, Swara; Primack, Joel; Dekel, Avishai; Koo, David; Faber, Sandra

    2015-08-01

    A common feature of star-forming galaxies at z>1 is the existence of giant star-forming clumps, which are fundamental to our understanding of the accretion history of galaxies, formation of bulges, and evolution of gas-rich disks. In this talk, I will present our work on understanding the nature of clumps in high-redshift galaxies by comparing CANDELS observations with CANDELized high-resolution cosmological hydrodynamic simulations. The CANDELized simulations take into account of all observational effects, e.g., spatial resolution and sensitivity, of CANDELS images and thus provide a direct way to compare clumps identified in both observations and simulations. The comparison with the cosmological simulations also sheds a light on the roles that clumps play in the broad picture of galaxy formation and evolution. Our work focus on three questions: (1) When and how clumps are formed? (2) How they evolve once formed? (3) Can we use clumps as diagnostics of physical mechanisms that govern star formation, e.g., feedback? The three aspects provide important clues of tracing how distant clumpy galaxies evolve into galaxies seen in the local universe.

  19. Herschel observations of FIR emission lines in brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Edge, A. C.; Oonk, J. B. R.; Mittal, R.; Allen, S. W.; Baum, S. A.; Böhringer, H.; Bregman, J. N.; Bremer, M. N.; Combes, F.; Crawford, C. S.; Donahue, M.; Egami, E.; Fabian, A. C.; Ferland, G. J.; Hamer, S. L.; Hatch, N. A.; Jaffe, W.; Johnstone, R. M.; McNamara, B. R.; O'Dea, C. P.; Popesso, P.; Quillen, A. C.; Salomé, P.; Sarazin, C. L.; Voit, G. M.; Wilman, R. J.; Wise, M. W.

    2010-07-01

    The question of how much gas cools in the cores of clusters of galaxies has been the focus of many, multiwavelength studies in the past 30 years. In this letter we present the first detections of the strongest atomic cooling lines, [Cii], [Oi] and [Nii] in two strong cooling flow clusters, A1068 and A2597, using Herschel-PACS. These spectra indicate that the substantial mass of cold molecular gas (> 109 M_⊙) known to be present in these systems is being irradiated by intense UV radiation, most probably from young stars. The line widths of these FIR lines indicate that they share dynamics similar but not identical to other ionised and molecular gas traced by optical, near-infrared and CO lines. The relative brightness of the FIR lines compared to CO and FIR luminosity is consistent with other star-forming galaxies indicating that the properties of the molecular gas clouds in cluster cores and the stars they form are not unusual. These results provide additional evidence for a reservoir of cold gas that is fed by the cooling of gas in the cores of the most compact clusters and provide important diagnostics of the temperature and density of the dense clouds this gas resides in. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  20. High-J CO Intensity Measurements for Galaxies Observed by the Herschel FTS

    NASA Astrophysics Data System (ADS)

    Kamenetzky, Julia; Rangwala, Naseem; Glenn, Jason; Maloney, Philip; Conley, Alex

    Molecular gas is the raw material for star formation and is commonly traced by the carbon monoxide (CO) molecule. The atmosphere blocks all but the lowest-J transitions of CO for observatories on the ground, but the launch of the Herschel Space Observatory revealed the CO emission of nearby galaxies from J = 4-3 to J = 13-12. Herschel showed that mid- and high-J CO lines in nearby galaxies are emitted from warm gas, accounting for approximately 10% of the molecular mass, but the majority of the CO luminosity. The energy budget of this warm, highly-excited gas is a significant window into the feedback interactions among molecular gas, star formation, and galaxy evolution. Likely, mechanical heating is required to explain the excitation. Such gas has also been observed in star forming regions within our galaxy. We have examined all ~300 spectra of galaxies from the Herschel Fourier Transform Spectrometer and measured line fluxes or upper limits for the CO J = 4-3 to J = 13-12, [CI], and [NII] 205 micron lines in ~200 galaxies, taking systematic effects of the FTS into account. We will present our line fitting method, illustrate trends available so far in this large sample, and preview the full 2-component radiative transfer likelihood modeling of the CO emission using an illustrative sample of 20 galaxies, including comparisons to well-resolved galactic regions. This work is a comprehensive study of mid- and high-J CO emission among a variety of galaxy types, and can be used as a resource for future (sub)millimeter studies of galaxies with ground-based instruments.

  1. (12)CO (3-2) & (1-0) emission line observations of nearby starburst galaxy nuclei

    NASA Technical Reports Server (NTRS)

    Devereux, Nicholas; Taniguchi, Yoshiaki; Sanders, D. B.; Nakai, N.; Young, J. S.

    1994-01-01

    New measurements of the (12)CO (1-0) and (12)CO (3-2) line emission are presented for the nuclei of seven nearby starburst galaxies selected from a complete sample of 21 nearby starburst galaxies for which the nuclear star formation rates are measured to be comparable to the archetype starburst galaxies M82 and NGC 253. The new observations capitalize on the coincidence between the beam size of the 45 m Nobeyama telescope at 115 GHz and that of the 15 m James Clerk Maxwell Telescope at 345 GHz to measure the value of the (12)CO (3-2)/(1-0) emission line ratio in a 15 sec (less than or equal to 2.5 kpc) diameter region centered on the nuclear starburst. In principle, the (12)CO (3-2)/(1-0) emission line ratio provides a measure of temperature and optical depth for the (12)CO gas. The error weighted mean value of the (12)CO (3-2)/(1-0) emission line ratio measured for the seven starburst galaxy nuclei is -0.64 +/- 0.06. The (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is significantly higher than the average value measured for molecular gas in the disk of the Galaxy, implying warmer temperatures for the molecular gas in starburst galaxy nuclei. On the other hand, the (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is not as high as would be expected if the molecular gas were hot, greater than 20 K, and optically thin, tau much less than 1. The total mass of molecular gas contained within the central 1.2-2.8 kpc diameter region of the starburst galaxy nuclei ranges from 10(exp 8) to 10(exp 9) solar mass. While substantial, the molecular gas mass represents only a small percentage, approximately 9%-16%, of the dynamical mass in the same region.

  2. (12)CO (3-2) & (1-0) emission line observations of nearby starburst galaxy nuclei

    NASA Technical Reports Server (NTRS)

    Devereux, Nicholas; Taniguchi, Yoshiaki; Sanders, D. B.; Nakai, N.; Young, J. S.

    1994-01-01

    New measurements of the (12)CO (1-0) and (12)CO (3-2) line emission are presented for the nuclei of seven nearby starburst galaxies selected from a complete sample of 21 nearby starburst galaxies for which the nuclear star formation rates are measured to be comparable to the archetype starburst galaxies M82 and NGC 253. The new observations capitalize on the coincidence between the beam size of the 45 m Nobeyama telescope at 115 GHz and that of the 15 m James Clerk Maxwell Telescope at 345 GHz to measure the value of the (12)CO (3-2)/(1-0) emission line ratio in a 15 sec (less than or equal to 2.5 kpc) diameter region centered on the nuclear starburst. In principle, the (12)CO (3-2)/(1-0) emission line ratio provides a measure of temperature and optical depth for the (12)CO gas. The error weighted mean value of the (12)CO (3-2)/(1-0) emission line ratio measured for the seven starburst galaxy nuclei is -0.64 +/- 0.06. The (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is significantly higher than the average value measured for molecular gas in the disk of the Galaxy, implying warmer temperatures for the molecular gas in starburst galaxy nuclei. On the other hand, the (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is not as high as would be expected if the molecular gas were hot, greater than 20 K, and optically thin, tau much less than 1. The total mass of molecular gas contained within the central 1.2-2.8 kpc diameter region of the starburst galaxy nuclei ranges from 10(exp 8) to 10(exp 9) solar mass. While substantial, the molecular gas mass represents only a small percentage, approximately 9%-16%, of the dynamical mass in the same region.

  3. Multiwavelength observations of giant radio galaxy 3C 35 and 3C 284

    NASA Astrophysics Data System (ADS)

    Pal, Sabyasachi; Chakrabarti, Sandip Kumar; Patra, Dusmanta; Konar, Chiranjib

    2016-07-01

    We report multi wavelength observations of large radio galaxy 3C35 and 3C284. The low frequency observations were done with the Giant Metrewave Radio Telescope (GMRT) starting from 150 MHz. The high frequency observations were done with Jansky Very Large Array (JVLA). Our main motivation for these observations is to estimate the spectral ages of these galaxies and to examine any proof of extended emission at low radio frequencies due to an earlier cycle of activity. The spectral age is measured by fitting the spectra with different spectral ageing models e.g. Kardashev-Pacholczyk (KP), Jaffe-Perola (JP) and Continuous Injection (CI).

  4. Simulations of high-z galaxy observations with an E-ELT/MOS

    NASA Astrophysics Data System (ADS)

    Puech, Mathieu; Disseau, Karen; Pentericci, Laura

    2013-12-01

    I will present simulated observations of two important science cases of the 39m E-ELT, ie, the mass assembly in galaxies over z=2-5 and the detection of very high-z galaxies. These simulations are currently used to constrain the top level requirements of MOSAIC, which is a new MOS concept for the E-ELT. MOSAIC largely builds on two E-ELT instrument phase A studies, namely EAGLE, an MOAO-fed NIR multi-IFU spectragraph and OPTIMOS-EVE, a GLAO-limited fiber-fed NIR spectrograph. I will give a short summary of the MOSAIC study and detail how galaxy simulations are currently used to constrain the instrument conceptual design, and in particular simulations of the detection of UV interstellar lines in very distant (i.e.: z > 6) galaxies.

  5. OBSERVATIONAL EVIDENCE FOR YOUNG RADIO GALAXIES IS TRIGGERED BY ACCRETION DISK INSTABILITY

    SciTech Connect

    Wu Qingwen

    2009-08-20

    Bolometric luminosities and black hole (BH) masses are estimated by various methods for a sample of young radio galaxies with known ages. We find that the ages are positively correlated with the bolometric luminosities in these young radio galaxies. This positive correlation is consistent with the theoretical prediction based on the radiation pressure instability of accretion disks in Czerny et al. The ages of young radio galaxies are also found to be consistent with the theoretical durations of outbursts in BH mass and accretion rate (in Eddington unit) plane, where the outbursts are assumed to be triggered by the radiation pressure instabilities. Our results provide observational evidence for the radiation pressure instability, which causes limit-cycle behavior, as a physical mechanism that may be responsible for these short-lived young radio galaxies.

  6. Constraining the Evolution of Galaxy Properties in Interacting Systems with UV-FIR Observations and Simulations

    NASA Astrophysics Data System (ADS)

    Lanz, Lauranne; Zezas, A.; Brassington, N.; Smith, H. A.; Ashby, M. N.; da Cunha, E.; Hayward, C. C.; Jonsson, P.; Hernquist, L. E.; Fazio, G. G.

    2013-01-01

    The evolution of galaxies is greatly influenced by their interactions. As part of the Spitzer Interacting Galaxy Survey (SIGS), we imaged 48 nearby systems with Spitzer. We measured and modeled the spectral energy distributions (SEDs) at wavelengths from the ultraviolet (UV) to the far-infrared (FIR) of the set of these galaxies with publicly available Herschel SPIRE observations. We fit these SEDs with the Bayesian SED-fitting program MAGPHYS developed by da Cunha et al. (2008). In order to determine the reliability of the parameters extracted, we determined how well MAGPHYS recovers parameters of hydrodynamic simulations run with GADGET (Springel et al. 2005) and for which simulated photometry was calculated using the SUNRISE radiative transfer code (Jonsson et al. 2010). We present our conclusions on the variations with interaction stage of galaxy properties including: star formation histories; dust luminosities, temperatures, and masses; and stellar masses. We discuss how successfully MAGPHYS recovers galaxy properties and which instruments are most crucial for constraining masses, star formation histories, and dust properties. We compare the simulations directly to the observations, examining how unique a diagnostic an interacting galaxy SED can be. Finally, we compare and discuss how well the many simple star formation estimating relations (using 24 micron flux, for example) succeed and why.

  7. Submillimeter Observations of CLASH 2882 and the Evolution of Dust in this Galaxy

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G; Kovacs, Attila; Decarli, Roberto; Egami, Eiichi; Michalowski, Michal J.; Rawle, Timothy D.; Toft, Sune; Walter, Fabian

    2015-01-01

    Two millimeter observations of the MACS J1149.6+2223 cluster have detected a source that was consistent with the location of the lensed MACS 1149-JD galaxy at z = 9.6. A positive identification would have rendered this galaxy as the youngest dust forming galaxy in the universe. Follow up observation with the AzTEC 1.1 mm camera and the IRAM NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm have not confirmed this association. In this paper we show that the NOEMA observations associate the 2 mm source with [PCB2012] 2882,12 source number 2882 in the Cluster Lensing And Supernova survey with Hubble (CLASH) catalog of MACS J1149.6 +2223. This source, hereafter referred to as CLASH 2882, is a gravitationally lensed spiral galaxy at z = 0.99. We combine the Goddard IRAM Superconducting 2-Millimeter Observer (GISMO) 2 mm and NOEMA 1.3 mm fluxes with other (rest frame) UV to far-IR observations to construct the full spectral energy distribution of this galaxy, and derive its star formation history, and stellar and interstellar dust content. The current star formation rate of the galaxy is 54/mu/Solar Mass/yr, and its dust mass is about 5 × 10(exp 7)/mu Solar Mass, where mu is the lensing magnification factor for this source, which has a mean value of 2.7. The inferred dust mass is higher than the maximum dust mass that can be produced by core collapse supernovae and evolved AGB stars. As with many other star forming galaxies, most of the dust mass in CLASH 2882 must have been accreted in the dense phases of the interstellar medium.

  8. Submillimeter Observations of CLASH 2882 and the Evolution of Dust in this Galaxy

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G; Kovacs, Attila; Decarli, Roberto; Egami, Eiichi; Michalowski, Michal J.; Rawle, Timothy D.; Toft, Sune; Walter, Fabian

    2015-01-01

    Two millimeter observations of the MACS J1149.6+2223 cluster have detected a source that was consistent with the location of the lensed MACS 1149-JD galaxy at z = 9.6. A positive identification would have rendered this galaxy as the youngest dust forming galaxy in the universe. Follow up observation with the AzTEC 1.1 mm camera and the IRAM NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm have not confirmed this association. In this paper we show that the NOEMA observations associate the 2 mm source with [PCB2012] 2882,12 source number 2882 in the Cluster Lensing And Supernova survey with Hubble (CLASH) catalog of MACS J1149.6 +2223. This source, hereafter referred to as CLASH 2882, is a gravitationally lensed spiral galaxy at z = 0.99. We combine the Goddard IRAM Superconducting 2-Millimeter Observer (GISMO) 2 mm and NOEMA 1.3 mm fluxes with other (rest frame) UV to far-IR observations to construct the full spectral energy distribution of this galaxy, and derive its star formation history, and stellar and interstellar dust content. The current star formation rate of the galaxy is 54/mu/Solar Mass/yr, and its dust mass is about 5 × 10(exp 7)/mu Solar Mass, where mu is the lensing magnification factor for this source, which has a mean value of 2.7. The inferred dust mass is higher than the maximum dust mass that can be produced by core collapse supernovae and evolved AGB stars. As with many other star forming galaxies, most of the dust mass in CLASH 2882 must have been accreted in the dense phases of the interstellar medium.

  9. Submillimeter Observations of CLASH 2882 and the Evolution of Dust in this Galaxy

    NASA Astrophysics Data System (ADS)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G.; Kovács, Attila; Decarli, Roberto; Egami, Eiichi; Michałowski, Michał J.; Rawle, Timothy D.; Toft, Sune; Walter, Fabian

    2015-11-01

    Two millimeter observations of the MACS J1149.6+2223 cluster have detected a source that was consistent with the location of the lensed MACS 1149-JD galaxy at z = 9.6. A positive identification would have rendered this galaxy as the youngest dust forming galaxy in the universe. Follow up observation with the AzTEC 1.1 mm camera and the IRAM NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm have not confirmed this association. In this paper we show that the NOEMA observations associate the 2 mm source with [PCB2012] 2882,12 source number 2882 in the Cluster Lensing And Supernova survey with Hubble (CLASH) catalog of MACS J1149.6+2223. This source, hereafter referred to as CLASH 2882, is a gravitationally lensed spiral galaxy at z = 0.99. We combine the Goddard IRAM Superconducting 2-Millimeter Observer (GISMO) 2 mm and NOEMA 1.3 mm fluxes with other (rest frame) UV to far-IR observations to construct the full spectral energy distribution of this galaxy, and derive its star formation history, and stellar and interstellar dust content. The current star formation rate of the galaxy is 54{μ }-1 M⊙ yr-1, and its dust mass is about 5 × 107{μ }-1 M⊙, where μ is the lensing magnification factor for this source, which has a mean value of 2.7. The inferred dust mass is higher than the maximum dust mass that can be produced by core collapse supernovae and evolved AGB stars. As with many other star forming galaxies, most of the dust mass in CLASH 2882 must have been accreted in the dense phases of the interstellar medium.

  10. The evolution of C/O in dwarf galaxies from Hubble Space Telescope FOS observations

    NASA Technical Reports Server (NTRS)

    Garnett, D. R.; Skillman, E. D.; Dufour, R. J.; Peimbert, M.; Torres-Peimbert, S.; Terlevich, R.; Terlevich, E.; Shields, G. A.

    1995-01-01

    We present UV observations of seven H II regions in low-luminosity dwarf irregular galaxies and the Magellanic Clouds obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) in order to measure the C/O abundance ratio in the interstellar medium (ISM) of those galaxies. We measure both O III 1666 A and C III 1909 A in our spectra, enabling us to determine C(+2)/O(+2) with relatively small uncertainties. The results from our HST observations show a continuous increase in C/O with increasing O/H, consistent with a power law having an index of 0.43 +/- 0.09 over the range -4.7 to -3.6 in log (O/H). One possible interpretation of this trend is that the most metal-poor galaxies are the youngest and dominated by the products of early enrichment by massive stars, while more metal-rich galaxies show increasing, delayed contributions of carbon from intermediate-mass stars. Our results also suggest that it may not be appropiate to combine abundances in irregular galaxies with those in spiral galaxies to study the evolution of chemical abundances. Our measured C/O ratios in the most metal-poor galaxies are consistent with predictions of nucleosynthesis from massive stars for Weaver & Woosley's best estimate for the 12C(alpha, gamma) 16O nuclear reaction rate, assuming negligible contanmination from carbon produced in intermediate-mass stars in these galaxies. We detect a weak N III 1750 A multiplet in SMC N88A and obtain interesting upper limits for two other objects. Our 2 sigma uppr limits on the 1750 A feature indicate that the N(+2)/O(+2) ratios in these objects are not significantly larger than the N(+)/O(+) ratios measured from optical spectra. This behavior is consistent with predictions of photionization models, although better detections of N III are needed to confirm the results.

  11. Observational Manifestation of Chaos in Grand Design Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Fridman, Alexei M.; Sagdeev, Roald Z.; Khoruzii, Oleg V.; et al.

    To study dynamic properties of the gaseous disk of the grand design spiral galaxy NGC 3631 we calculate the Lyapunov characteristic numbers (LCN) for different families of streamlines in the disk. For the trajectories near separatrices of the giant vortices and near saddle points presenting in the velocity field, the LCN turned out to be positive. The result is insensitive to the method of the calculation. Both methods -- using two trajectories and based on linearized equations -- give the identical results. The values of the LCN in the gaseous disk of NGC 3631 are independent on the Riemannian metric used for the calculations in agreement with the classical mathematical theorem. The spectra of the 'short-time' LCN (stretching numbers) evaluated for the same trajectories turned out to be non-invariant. We confirmed this result obtained for the real galactic disk on classical model examples.

  12. VERITAS Observations of the Cygnus Region of the Galaxy

    NASA Astrophysics Data System (ADS)

    Bird, Ralph; VERITAS Collaboration

    2016-03-01

    The Cygnus region is a very active region of our Galaxy, with many sources of GeV and TeV gamma-ray emission, such as supernova remnants, pulsar wind nebulae, high mass X-ray binaries and massive star clusters. A detailed study of the Cygnus region can give insight into the processes of particle acceleration in astrophysical sources. VERITAS is an array of four 12-meter diameter imaging atmospheric Cherenkov telescopes located at Mt. Hopkins, AZ, USA. From 2007 through 2012 nearly 300 hours of data was gathered in the Cygnus region, covering 67 to 83 degrees Galactic longitude and -2 to 5 degrees in Galactic latitude. An update of the Fermi-LAT and VERITAS analysis of this region is presented. In particular we examine the source and hotspot regions within the Milagro dataset covering this region and the comparison between these objects in the three different instruments.

  13. Herschel Observed Stripe 82 Quasars and Their Host Galaxies: Connections between AGN Activity and host Galaxy Star Formation

    NASA Astrophysics Data System (ADS)

    Dong, X. Y.; Wu, Xue-Bing

    2016-06-01

    In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high-luminosity quasars with a mean bolometric luminosity of 1046.4 erg s-1. The redshift range of this sample is within z < 4, with a mean value of 1.5 ± 0.78. Because we only selected quasars that have been detected in all three Herschel-SPIRE bands, the quasar sample is complete yet highly biased. Based on the multi-wavelength photometric observation data, we conducted a spectral energy distribution (SED) fitting through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity, far-IR (FIR) luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419 M ⊙ yr-1 and the mean gas mass is ˜1011.3 M ⊙. All of these results point to an IR luminous quasar system. Compared with star formation main sequence (MS) galaxies, at least 80 out of 207 quasars are hosted by starburst galaxies. This supports the statement that luminous AGNs are more likely to be associated with major mergers. The SFR increases with the redshift up to z = 2. It is correlated with the AGN bolometric luminosity, where {L}{{FIR}}\\propto {L}{{Bol}}0.46+/- 0.03. The AGN bolometric luminosity is also correlated with the host galaxy mass and gas mass. Yet the correlation between L FIR and L Bol has higher significant level, implies that the link between AGN accretion and the SFR is more primal. The M BH/M * ratio of our sample is 0.02, higher than the value 0.005 in the local universe. It might indicate an evolutionary trend of the M BH-M * scaling relation.

  14. DEEP GALEX OBSERVATIONS OF THE COMA CLUSTER: SOURCE CATALOG AND GALAXY COUNTS

    SciTech Connect

    Hammer, D.; Hornschemeier, A. E.; Miller, N.; Jenkins, L.; Mobasher, B.; Smith, R.; Arnouts, S.; Milliard, B.

    2010-09-15

    We present a source catalog from a deep 26 ks Galaxy Evolution Explorer (GALEX) observation of the Coma cluster in the far-UV (FUV; 1530 A) and near-UV (NUV; 2310 A) wavebands. The observed field is centered {approx}0.{sup 0}9 (1.6 Mpc) southwest of the Coma core in a well-studied region of the cluster known as 'Coma-3'. The entire field is located within the apparent virial radius of the Coma cluster, and has optical photometric coverage with Sloan Digital Sky Survey (SDSS) and deep spectroscopic coverage to r {approx} 21. We detect GALEX sources to NUV = 24.5 and FUV = 25.0, which corresponds to a star formation rate of {approx}10{sup -3} M {sub sun} yr{sup -1} for galaxies at the distance of Coma. We have assembled a catalog of 9700 galaxies with GALEX and SDSS photometry, including 242 spectroscopically confirmed Coma member galaxies that span a large range of galaxy types from giant spirals and elliptical galaxies to dwarf irregular and early-type galaxies. The full multi-wavelength catalog (cluster plus background galaxies) is {approx}80% complete to NUV = 23 and FUV = 23.5. The GALEX images presented here are very deep and include detections of many resolved cluster members superposed on a dense field of unresolved background galaxies. This required a two-fold approach to generating a source catalog: we used a Bayesian deblending algorithm to measure faint and compact sources (using SDSS coordinates as position prior), and used the GALEX pipeline catalog for bright and/or extended objects. We performed simulations to assess the importance of systematic effects (e.g., object blends, source confusion, Eddington Bias) that influence the source detection and photometry when using both methods. The Bayesian deblending method roughly doubles the number of source detections and provides reliable photometry to a few magnitudes deeper than the GALEX pipeline catalog. This method is free from source confusion over the UV magnitude range studied here; we estimate that

  15. Real & Simulated IFU Observations of Low-Mass Early-Type Galaxies: Environmental Influence Probed for Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Sybilska, Agnieszka; Łokas, Ewa Luiza; Fouquet, Sylvain

    2017-03-01

    We combine high-quality IFU data with a new set of numerical simulations to study low-mass early type galaxies (dEs) in dense environments. Our earlier study of dEs in the Virgo cluster has produced the first large-scale maps of kinematic and stellar population properties of dEs in those environments (Ryś et al. 2013, 2014, 2015). A quantitative discrimination between various (trans)formation processes proposed for these objects is, however, a complex issue, requiring a priori assumptions about the progenitors of galaxies we observe and study today. To bridge this gap between observations and theoretical predictions, we use the expertise gained in the IFU data analysis to look ``through the eye of SAURON'' at our new suite of high-resolution N-body simulations of dEs in the Virgo cluster. Mimicking the observers perspective as closely as possible, we can also indicate the existing instrumental and viewer limitations regarding what we are/are not able to detect as observers.

  16. Observing Evolution in Star-Forming Galaxies in X-Rays

    NASA Technical Reports Server (NTRS)

    Ptak, Andrew

    2011-01-01

    The Chandra Deep Fields (CDFs) have reached flux limits where normal/starburst galaxies are significant contributors to the X-ray number counts (approximately 40% at F _{0.5-2.0} = 1 x 10(^)-17). Based on these results and current theoretical models of X-ray binary evolution we will discuss expectations for observing galaxy evolution in X-rays in IXO deep surveys. With the high sensitivity of IXO (particularly approximately 5" resolution constant across the WFI FOV and high effective area) IXO surveys should detect large numbers of galaxies which will allow evolution to be studied in multiple redshift bins. High spatial resolution will also drive the need to minimize source confusion below F _{0.5-2.0 keV} = 10^{-17} ergs/s/cm^2. In addition to detecting starburst galaxies individually, stacking will be used to constrain their properties on average, particularly Lyman-break galaxies at z greater than 2. We will also discuss challenges in segregating galaxies from obscured AGN in IXO deep fields and expectations proposed survey X-ray missions.

  17. 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.

  18. Comparing Simulations and Observations of Galaxy Evolution: Methods for Constraining the Nature of Stellar Feedback

    NASA Astrophysics Data System (ADS)

    Hummels, Cameron

    Computational hydrodynamical simulations are a very useful tool for understanding how galaxies form and evolve over cosmological timescales not easily revealed through observations. However, they are only useful if they reproduce the sorts of galaxies that we see in the real universe. One of the ways in which simulations of this sort tend to fail is in the prescription of stellar feedback, the process by which nascent stars return material and energy to their immediate environments. Careful treatment of this interaction in subgrid models, so-called because they operate on scales below the resolution of the simulation, is crucial for the development of realistic galaxy models. Equally important is developing effective methods for comparing simulation data against observations to ensure galaxy models which mimic reality and inform us about natural phenomena. This thesis examines the formation and evolution of galaxies and the observable characteristics of the resulting systems. We employ extensive use of cosmological hydrodynamical simulations in order to simulate and interpret the evolution of massive spiral galaxies like our own Milky Way. First, we create a method for producing synthetic photometric images of grid-based hydrodynamical models for use in a direct comparison against observations in a variety of filter bands. We apply this method to a simulation of a cluster of galaxies to investigate the nature of the red-sequence/blue-cloud dichotomy in the galaxy color-magnitude diagram. Second, we implement several subgrid models governing the complex behavior of gas and stars on small scales in our galaxy models. Several numerical simulations are conducted with similar initial conditions, where we systematically vary the subgrid models, afterward assessing their efficacy through comparisons of their internal kinematics with observed systems. Third, we generate an additional method to compare observations with simulations, focusing on the tenuous circumgalactic

  19. Herschel Extreme Lensing Line Observations: [CII] Variations in Galaxies at Redshifts z=1-3*

    NASA Technical Reports Server (NTRS)

    Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, K.; Yang, Huan; Carilli, Chris; Combes, Francoise; Dassas, Karine; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne; hide

    2017-01-01

    We observed the [C II] line in 15 lensed galaxies at redshifts 1 less than z less than 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3sigma or better. High magnifications enable even modestly luminous galaxies to be detected in [C II] with Herschel. The [C II] luminosity in this sample ranges from 8 × 10(exp 7) solar luminosity to 3.7 × 10(exp 9) solar luminosity (after correcting for magnification), confirming that [C II] is a strong tracer of the ISM at high redshifts. The ratio of the [C II] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C II]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C II]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C II]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C II]/FIR correlates most strongly with dust temperature. The [C II] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.

  20. Herschel Extreme Lensing Line Observations: [CII] Variations in Galaxies at Redshifts z=1-3

    NASA Astrophysics Data System (ADS)

    Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, K.; Yang, Huan; Carilli, Chris; Combes, Françoise; Dassas, Karine; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne; Guillard, Pierre; Nesvadba, Nicole; Rigby, Jane; Shin, Min-Su; Spaans, Marco; Strauss, Michael A.; Papovich, Casey

    2017-01-01

    We observed the [C ii] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C ii] with Herschel. The [C ii] luminosity in this sample ranges from 8 × 107 L⊙ to 3.7 × 109 L⊙ (after correcting for magnification), confirming that [C ii] is a strong tracer of the ISM at high redshifts. The ratio of the [C ii] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C ii]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C ii]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C ii]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C ii]/FIR correlates most strongly with dust temperature. The [C ii] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  1. Gemini Observations of Galaxies in Rich Early Environments (GOGREEN) I: survey description

    NASA Astrophysics Data System (ADS)

    Balogh, Michael L.; Gilbank, David G.; Muzzin, Adam; Rudnick, Gregory; Cooper, Michael C.; Lidman, Chris; Biviano, Andrea; Demarco, Ricardo; McGee, Sean L.; Nantais, Julie B.; Noble, Allison; Old, Lyndsay; Wilson, Gillian; Yee, Howard K. C.; Bellhouse, Callum; Cerulo, Pierluigi; Chan, Jeffrey; Pintos-Castro, Irene; Simpson, Rane; van der Burg, Remco F. J.; Zaritsky, Dennis; Ziparo, Felicia; Alonso, María Victoria; Bower, Richard G.; De Lucia, Gabriella; Finoguenov, Alexis; Lambas, Diego Garcia; Muriel, Hernan; Parker, Laura C.; Rettura, Alessandro; Valotto, Carlos; Wetzel, Andrew

    2017-10-01

    We describe a new Large Program in progress on the Gemini North and South telescopes: Gemini Observations of Galaxies in Rich Early Environments (GOGREEN). This is an imaging and deep spectroscopic survey of 21 galaxy systems at 1 < z < 1.5, selected to span a factor >10 in halo mass. The scientific objectives include measuring the role of environment in the evolution of low-mass galaxies, and measuring the dynamics and stellar contents of their host haloes. The targets are selected from the SpARCS, SPT, COSMOS, and SXDS surveys, to be the evolutionary counterparts of today's clusters and groups. The new red-sensitive Hamamatsu detectors on GMOS, coupled with the nod-and-shuffle sky subtraction, allow simultaneous wavelength coverage over λ ˜ 0.6-1.05 μm, and this enables a homogeneous and statistically complete redshift survey of galaxies of all types. The spectroscopic sample targets galaxies with AB magnitudes z΄ < 24.25 and [3.6] μm < 22.5, and is therefore statistically complete for stellar masses M* ≳ 1010.3 M⊙, for all galaxy types and over the entire redshift range. Deep, multiwavelength imaging has been acquired over larger fields for most systems, spanning u through K, in addition to deep IRAC imaging at 3.6 μm. The spectroscopy is ˜50 per cent complete as of semester 17A, and we anticipate a final sample of ˜500 new cluster members. Combined with existing spectroscopy on the brighter galaxies from GCLASS, SPT, and other sources, GOGREEN will be a large legacy cluster and field galaxy sample at this redshift that spectroscopically covers a wide range in stellar mass, halo mass, and clustercentric radius.

  2. Observations of dwarfs in nearby voids: implications for galaxy formation and evolution

    NASA Astrophysics Data System (ADS)

    Pustilnik, Simon A.

    2016-10-01

    The intermediate results of the ongoing study of deep samples of ~200 galaxies residing in nearby voids, are presented. Their properties are probed via optical spectroscopy, ugri surface photometry, and HI 21-cm line measurements, with emphasis on their evolutionary status. We derive directly the hydrogen mass M(HI), the ratio M(HI)/LB and the evolutionary parameter gas-phase O/H. Their luminosities and integrated colours are used to derive stellar mass M* and the second evolutionary parameter - gas mass-fraction f g). The colours of the outer parts, typically representative of the galaxy oldest stellar population, are used to estimate the upper limits on time since the beginning of the main SF episode. We compare properties of void galaxies with those of the similar late-type galaxies in denser environments. Most of void galaxies show smaller O/H for their luminosity, in average by ~30\\%, indicating slower evolution. Besides, the fraction of ~10\\% of the whole void sample or ~30\\% of the least luminous void LSB dwarfs show the oxygen deficiency by a factor of 2-5. The majority of this group appear very gas-rich, with f g ~(95-99)%, while their outer parts appear rather blue, indicating the time of onset of the main star-formation episode of less than 1-4 Gyr. Such unevolved LSBD galaxies appear not rare among the smallest void objects, but turned out practically missed to date due to the strong observational selection effects. Our results evidense for unusual evolutionary properties of the sizable fraction of void galaxies, and thus, pose the task of better modelling of dwarf galaxy formation and evolution in voids.

  3. Observational probes of the connection between Star Formation Efficiency and Dark Matter halo mass of galaxies

    NASA Astrophysics Data System (ADS)

    Kalinova, Veselina; Colombo, Dario; Rosolowsky, Erik

    2015-08-01

    Modern simulations predict that the stellar mass and the star formation efficiency of a galaxy are tightly linked to the dark matter (DM) halo mass of that galaxy. This prediction relies on a specific model of galaxy evolution and so testing this prediction directly tests our best models of galaxy formation and evolution. Recent DM numerical studies propose relationships between star formation efficiency and the DM halo mass with two domains based on SF feedback (low-mass) vs. AGN feedback (high-mass), see Moster et al. (2013). The observational probe of such parameters in the relationship imply globally important physics that are fundamental as, e.g., the star formation law (e.g., Kennicutt et al., 1998), the universal depletion time (Leroy et al. 2008), and the origin of the cold gas phase with respect to the stellar disc (Davis et al.2011). Thus, we can directly measure whether this parameterization is correct by estimating the stellar mass, star formation efficiency and dynamical (DM) mass for a set of galaxies at strategically selected points to test if they fall on the predicted relationship.We use CO data from the Extragalactic Database for Galaxy Evolution survey (EDGE) in conjunction with archival 21-cm data and spectroscopic data from Calar Alto Legacy Integral Field spectroscopy Area survey (CALIFA) to measure the stellar vs. halo mass and star-formation-efficiency vs. halo mass relations of the galaxies. We also analyze archival 21-cm spectra to estimate rotation speeds, atomic gas masses and halo masses for a set of EDGE galaxies. Data from CALIFA are used for high quality star formation efficiency and stellar mass measurements. By linking these three parameters - stellar mass, star formation efficiency (SFE) and DM halo mass - we can test the simulation models of how the gas is cooling in the potential wells of the dark matter halos and then forms stars.

  4. Dense Cloud Cores revealed by ALMA CO observations in the low metallicity dwarf galaxy WLM

    NASA Astrophysics Data System (ADS)

    Rubio, M.; Elmegreen, B.; Hunter, D.; Cortes, J.; Brinks, E.; Cigan, P.

    2017-03-01

    Understanding stellar birth requires observations of the clouds in which they form. These clouds are dense and self-gravitating, and in all existing observations, they are molecular with H2 the dominant species and CO the best available. When the abundances of carbon and oxygen are low compared to hydrogen, and the opacity from dust is also low, as in primeval galaxies and local dwarf irregular galaxies CO forms slowly and is easily destroyed, so it cannot accumulate inside dense clouds. Then we lose our ability to trace the gas in regions of star formation and we lose critical information on the temperatures, densities, and velocities of the material that collapses. I will report on high resolution observations with ALMA of CO clouds in the local group dwarf irregular galaxy WLM, which has a metallicity that is 13% of the solar value and 50% lower than the previous CO detection threshold and the properties derived of very small dense CO clouds mapped..

  5. 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.

  6. Local Group Dwarf Galaxies in the LCDM Cosmology: Theory Meets Observations

    NASA Astrophysics Data System (ADS)

    Tollerud, Erik Jon

    2012-05-01

    Dwarf galaxies include some of the most extreme low-luminosity objects in the universe, and provide important windows into a wide variety of processes in galaxy formation and evolution. In this thesis, I describe a series of comparisons between observations of dwarf galaxies and predictions of the ΛCDM concordance cosmology, with a focus on Local Group satellites. I first correct the Milky Way satellite luminosity function for luminosity bias under the assumption of a typical ΛCDM satellite distribution, finding consistency with the observations and a prediction of possibly hundreds of faint Milky Way satellites. I also describe a new technique to connect the luminous properties of these satellites (as well as brighter galaxies) to their expected dark matter halo properties. I further consider the brightest Milky Way satellite, the Large Magellanic cloud (LMC), in a cosmological context by comparing it to similar galaxies in the Sloan Digital Sky Survey (SDSS). This shows that ΛCDM n-body simulations provide a good match to observations of such satellites. I also show that, while LMC-like satellites are not uncommon, the LMC is unusual in how blue it is, especially given that the SDSS satellites are significantly redder than typical galaxies of their size. Finally, I present a large new data for faint satellites of M31, the nearest galaxy similar to the Milky Way, providing a second data point for detailed studies of faint satellite systems. I also shows that its satellites are very similar in their general properties to that of the Milky Way satellites.

  7. Modeling spatially and spectrally resolved observations to diagnose the formation of elliptical galaxies

    NASA Astrophysics Data System (ADS)

    Snyder, Gregory Frantz

    2013-03-01

    In extragalactic astronomy, a central challenge is that we cannot directly watch what happens to galaxies before and after they are observed. This dissertation focuses on linking predictions of galaxy time-evolution directly with observations, evaluating how interactions, mergers, and other processes affect the appearance of elliptical galaxies. The primary approach is to combine hydrodynamical simulations of galaxy formation, including all major components, with dust radiative transfer to predict their observational signatures The current paradigm implies that a quiescent elliptical emerges following a formative starburst event. These trigger accretion onto the central supermassive black hole (SMBH), which then radiates as an active galactic nucleus (AGN). However, it is not clear the extent to which SMBH growth is fueled by these events nor how important is their energy input at setting the appearance of the remnant. This thesis presents results drawing from three phases in the formation of a typical elliptical: 1) I evaluate how to disentangle AGN from star formation signatures in mid-infrared spectra during a dust-enshrouded starburst, making testable predictions for robustly tracing SMBH growth with the James Webb Space Telescope; 2) I develop a model for the rate of merger-induced post-starburst galaxies selected from optical spectra, resolving tension between their observed rarity and merger rates from other estimates; and 3) I present results from Hubble Space Telescope imaging of elliptical galaxies in galaxy clusters at 1 < z < 2, the precursors of present-day massive clusters with M ~ 1015 solar masses, demonstrating that their stars formed over an extended period and ruling out the simplest model for their formation history. These results lend support to a stochastic formation history for ellipticals driven by mergers or interactions. However, significant uncertainties remain in how to evaluate the implications of galaxy appearance, in particular their

  8. 12CO(1-0) observation of isolated late-type galaxies

    NASA Astrophysics Data System (ADS)

    Sauty, S.; Casoli, F.; Boselli, A.; Gerin, M.; Lequeux, J.; Braine, J.; Gavazzi, G.; Dickey, J.; Kazès, I.; Fouqué, P.

    2003-12-01

    We present 12CO(J=1-0) line observations of 99 galaxies obtained with the SEST 15 m, the Kitt Peak 12 m and the IRAM 30 m telescopes. The target galaxies were selected from the catalogue of isolated galaxies of Karachentseva (\\cite{Karachentseva73}). These data are thus representative of the CO properties of isolated late-type galaxies. All objects were observed in their central position, those with large angular sizes were mapped. These new measurements are used to estimate the molecular gas mass of the target galaxies. The molecular gas is on average ~ 18% of the atomic gas mass. Tables 1 and 2 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/381 Based on observations made with the 12-m National Radio Astronomical Observatory, Kitt Peak, Arizona, with the Swedish-ESO Submillimetre telescope SEST, La Silla, Chile, with the IRAM 30 m radiotelescope, Pico Veleta, Granada, Spain.

  9. Integral Observations of the Reflection Component of Seyfert Galaxies

    NASA Technical Reports Server (NTRS)

    Fabian, Andrew

    2005-01-01

    The data were analyzed by Dr. Fabian's student Adrian Turner and included in his thesis (completed Sept 2004). We did not detect MCG-6 using the then current software and the spectrum of the Circinus galaxy turned out to be even worse then the published BeppoSAX spectrum. We decided not to do any more work on it. We were contacted about the data in March by Thierry Courvoisier (the data were thea public) as he had a student, Simona Soidi, working on a compilation of spectra. Dr. Fabian sent them the chapter from Adrian's thesis and we provided some general comments on what they were doing on 6 objects. This has since been accepted for publication with Fabian as a co-author. A paper on the Integral AGN catalogue appeared on astro-ph a few days ago which contains an detection of MCG-6 with a very poor spectrum. We didn't detect it because the software back then required a source to be detected within something like 30 min exposure in order to work. Integral is NOT very sensitive.

  10. Integral Observations of the Reflection Component of Seyfert Galaxies

    NASA Technical Reports Server (NTRS)

    Fabian, Andrew

    2005-01-01

    The data were analyzed by Dr. Fabian's student Adrian Turner and included in his thesis (completed Sept 2004). We did not detect MCG-6 using the then current software and the spectrum of the Circinus galaxy turned out to be even worse then the published BeppoSAX spectrum. We decided not to do any more work on it. We were contacted about the data in March by Thierry Courvoisier (the data were thea public) as he had a student, Simona Soidi, working on a compilation of spectra. Dr. Fabian sent them the chapter from Adrian's thesis and we provided some general comments on what they were doing on 6 objects. This has since been accepted for publication with Fabian as a co-author. A paper on the Integral AGN catalogue appeared on astro-ph a few days ago which contains an detection of MCG-6 with a very poor spectrum. We didn't detect it because the software back then required a source to be detected within something like 30 min exposure in order to work. Integral is NOT very sensitive.

  11. VLA observations of radio sources in interacting galaxy pairs in poor clusters

    NASA Technical Reports Server (NTRS)

    Batuski, David J.; Hanisch, Robert J.; Burns, Jack O.

    1992-01-01

    Observations of 16 radio sources in interacting galaxies in 14 poor clusters were made using the Very Large Array in the B configuration at lambda of 6 and 2 cm. These sources had been unresolved in earlier observations at lambda of 21 cm, and were chosen as a sample to determine which of three models for radio source formation actually pertains in interacting galaxies. From the analysis of this sample, the starburst model appears most successful, but the 'central monster' model could pertain in some cases.

  12. VLA observations of radio sources in interacting galaxy pairs in poor clusters

    NASA Technical Reports Server (NTRS)

    Batuski, David J.; Hanisch, Robert J.; Burns, Jack O.

    1992-01-01

    Observations of 16 radio sources in interacting galaxies in 14 poor clusters were made using the Very Large Array in the B configuration at lambda of 6 and 2 cm. These sources had been unresolved in earlier observations at lambda of 21 cm, and were chosen as a sample to determine which of three models for radio source formation actually pertains in interacting galaxies. From the analysis of this sample, the starburst model appears most successful, but the 'central monster' model could pertain in some cases.

  13. Characterizing ultraviolet and infrared observational properties for galaxies. II. Features of attenuation law

    SciTech Connect

    Mao, Ye-Wei; Kong, Xu; Lin, Lin E-mail: xkong@ustc.edu.cn

    2014-07-01

    Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-β relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies, we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 Å bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 Å bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.

  14. Observationally Constrained Metal Signatures of Galaxy Evolution in the Stars and Gas of Cosmological Simulations

    NASA Astrophysics Data System (ADS)

    Corlies, Lauren N.

    The halos of galaxies - consisting of gas, stars, and satellite galaxies - are formed and shaped by the most fundamental processes: hierarchical merging and the flow of gas into and out of galaxies. While these processes are hard to disentangle, metals are tied to the gas that fuels star formation and entrained in the wind that the deaths of these stars generate. As such, they can act as important indicators of the star formation, the chemical enrichment, and the outflow histories of galaxies. Thus, this thesis aims to take advantage of such metal signatures in the stars and gas to place observational constraints on current theories of galaxy evolution as implemented in cosmological simulations. The first two chapters consider the metallicities of stars in the stellar halo of the Milky Way and its surviving satellite dwarf galaxies. Chapter 2 pairs an N-body simulation with a semi-analytic model for supernova-driven winds to examine the early environment of a Milky Way-like galaxy. At z = 10, progenitors of surviving z = 0 satellite galaxies are found to sit preferentially on the outskirts of progenitor halos of the eventual main halo. The consequence of these positions is that main halo progenitors are found to more effectively cross-pollute each other than satellite progenitors. Thus, inhomogeneous cross-pollution as a result of different high-z spatial locations of different progenitors can help to explain observed differences in abundance patterns measured today. Chapter 3 expands this work into the analysis of a cosmological, hydrodynamical simulation of dwarf galaxies in the early universe. We find that simple assumptions for modeling the extent of supernova-driven winds used in Chapter 2 agree well with the simulation whereas the presence of inhomogeneous mixing in the simulation has a large effect on the stellar metallicities. Furthermore, the star-forming halos show both bursty and continuous SFHs, two scenarios proposed by stellar metallicity data

  15. Feathers in CO: CARMA CO(1-0) Observations of Four Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    La Vigne, Misty A.; Vogel, S. N.

    2007-12-01

    Feathers are striking extinction features that emerge from a spiral arm dust lane and arch into the interarm. Based on a study of HST archival images, La Vigne et al. 2006 find that feathers are common in a range of spiral galaxy types, and that observations of M51 suggest feathers emerge from giant molecular associations (GMAs) and can be associated with much of the star formation in a spiral galaxy. To evaluate whether the conclusions based on M51 can be more generally applied, we have observed CO(1-0) emission in four spiral galaxies at 2-3” resolution using the newly operational CARMA millimeter wave array. Maps of NGC 0628, NGC 3627, NGC 4637, and NGC 5055 are presented and implications for theories for the origin of feathers are discussed. CARMA operations are supported by the NSF under a cooperative agreement, and by the partner universities.

  16. Observational constraints on bending the wide-angle tailed radio galaxy 1919+479

    NASA Technical Reports Server (NTRS)

    Burns, J. O.; Gregory, S. A.; Odea, C. P.; Balonek, T. J.

    1986-01-01

    A wide range of new observations of the wide-angle tailed radio galaxy 1919+479 and its environs are presented. Multifrequency and multiconfiguration VLA observations are described, ranging in resolution from 0.7 arcsec to 40 arcsec. Distributions of source structures at different scale sizes, spectral indices, and polarizations are presented. Wide-field photographic and CCD imaging data are presented along with a review of the measured galaxy redshifts in the field. A newly reprocessed Einstein IPC X-ray image of the cluster is shown, and the X-ray emission's relationship to the radio morphology is described. The radio, optical, and X-ray data are used to constrain the cD galaxy dynamics and models for bending the radio structure. In particular, the possible role of jet collisions with clouds in the intracluster medium is considered. The applicability of cloud collision models to wide-angle tails in general is considered.

  17. COMPARING THE OBSERVABLE PROPERTIES OF DWARF GALAXIES ON AND OFF THE ANDROMEDA PLANE

    SciTech Connect

    Collins, Michelle L. M.; Martin, Nicolas F.; Rich, R. M.; Ibata, Rodrigo A.; Chapman, Scott C.; McConnachie, Alan W.; Ferguson, Annette M.; Irwin, Michael J.; Lewis, Geraint F.

    2015-01-20

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the Λ-cold dark matter paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) from their off-plane neighbors. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for two on-plane M31 dwarf spheroidal galaxies (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  18. Alma observations of nearby luminous infrared galaxies with various agn energetic contributions using dense gas tracers

    SciTech Connect

    Imanishi, Masatoshi; Nakanishi, Kouichiro

    2014-07-01

    We present the results of our ALMA Cycle 0 observations, using HCN/HCO{sup +}/HNC J = 4-3 lines, of six nearby luminous infrared galaxies with various energetic contributions from active galactic nuclei (AGNs) estimated from previous infrared spectroscopy. These lines are very effective for probing the physical properties of high-density molecular gas around the hidden energy sources in the nuclear regions of these galaxies. We find that HCN to HCO{sup +} J = 4-3 flux ratios tend to be higher in AGN-important galaxies than in starburst-dominated regions, as was seen at the J = 1-0 transition, while there is no clear difference in the HCN-to-HNC J = 4-3 flux ratios among observed sources. A galaxy with a starburst-type infrared spectral shape and very large molecular line widths shows a high HCN-to-HCO{sup +} J = 4-3 flux ratio, which could be due to turbulence-induced heating. We propose that enhanced HCN J = 4-3 emission relative to HCO{sup +} J = 4-3 could be used to detect more energetic activity than normal starbursts, including deeply buried AGNs, in dusty galaxy populations.

  19. New photometric and spectroscopic observations of the Seyfert galaxy Mrk 315

    NASA Astrophysics Data System (ADS)

    Ciroi, S.; Afanasiev, V. L.; Moiseev, A. V.; Botte, V.; Di Mille, F.; Dodonov, S. N.; Rafanelli, P.; Smirnova, A. A.

    2005-06-01

    We present new important results about the intermediate-type Seyfert galaxy Mrk 315, recently observed through optical imaging and integral-field spectroscopy. Broad-band images were used to study the morphology of the host galaxy, narrow-band Hα images to trace the star-forming regions, and middle-band [OIII] images to evidence the distribution of the highly ionized gas. Some extended emission regions were isolated and their physical properties studied by means of flux-calibrated spectra. High-resolution spectroscopy was used to separate different kinematic components in the velocity fields of gas and stars. Some peculiar features characterize this apparently undisturbed and moderately isolated active galaxy. Such features, already investigated by other authors, are re-analysed and discussed in the light of these new observations. The most relevant results we obtained are: the multitiers structure of the disc; the presence of a quasi-ring of regions with star formation much higher than previous claims; a secondary nucleus confirmed by a stellar component kinematically decoupled by the main galaxy; a new hypothesis about the controversial nature of the long filament, initially described as hook shaped, and more likely made of two independent filaments caused by interaction events between the main galaxy and two dwarf companions.

  20. A general relativistic signature in the galaxy bispectrum: the local effects of observing on the lightcone

    NASA Astrophysics Data System (ADS)

    Umeh, Obinna; Jolicoeur, Sheean; Maartens, Roy; Clarkson, Chris

    2017-03-01

    Next-generation galaxy surveys will increasingly rely on the galaxy bispectrum to improve cosmological constraints, especially on primordial non-Gaussianity. A key theoretical requirement that remains to be developed is the analysis of general relativistic effects on the bispectrum, which arise from observing galaxies on the past lightcone, as well as from relativistic corrections to the dynamics. As an initial step towards a fully relativistic analysis of the galaxy bispectrum, we compute for the first time the local relativistic lightcone effects on the bispectrum, which come from Doppler and gravitational potential contributions. For the galaxy bispectrum, the problem is much more complex than for the power spectrum, since we need the lightcone corrections at second order. Mode-coupling contributions at second order mean that relativistic corrections can be non-negligible at smaller scales than in the case of the power spectrum. In a primordial Gaussian universe, we show that the local lightcone projection effects for squeezed shapes at z ~ 1 mean that the bispectrum can differ from the Newtonian prediction by gtrsim 10% when the short modes are k lesssim (50 Mpc)‑1. These relativistic projection effects, if ignored in the analysis of observations, could be mistaken for primordial non-Gaussianity. For upcoming surveys which probe equality scales and beyond, all relativistic lightcone effects and relativistic dynamical corrections should be included for an accurate measurement of primordial non-Gaussianity.

  1. Luminous Infrared Galaxies Observed from the Ground and Space in the 2020s

    NASA Astrophysics Data System (ADS)

    Inami, Hanae; Armus, L.; Packham, C.; Dickinson, M.

    2014-07-01

    The dust-penetrating power of infrared observations will allow us to reveal the physical and chemical properties in and around the dust enshrouded nuclei of galaxies. While current near-infrared spectroscopic observations with 8-10m class telescopes can access to z=1-3 regime, they are still very challenging and limited to luminous targets. For z=0 objects, these telescopes can resolve HII regions, but we still do not fully understand the properties of more extreme star formation environments (e.g., rich in gas), which are more prevalent at higher redshifts. Near- and mid-infrared TMT instruments (e.g., two of the first light instruments IRIS and IRMS, and a planned mid-infrared instrument MICHI) will exploit TMT's unprecedented high spatial resolution to constrain the physical processes in individual dusty, intense star-forming regions of local galaxies as well as obtain resolved spectra for z=2-3 star-forming galaxies. During the era of 2020, JWST and SPICA are also expected to be commissioned. The high sensitivity of these space-based infrared observatories will facilitate investigations of the properties of dusty galaxies at even higher redshifts (z > 3). Only with the combination of ground- and space-observatories, we will be able to obtain a complete picture of star formation and AGN activity to explore the evolution of LIRGs which dominate the peak of the galaxy growth in the universe.

  2. Spitzer Observations of Passive and Star-Forming Early-Type Galaxies: An Infrared Color-Color Sequence

    NASA Astrophysics Data System (ADS)

    Temi, Pasquale; Brighenti, Fabrizio; Mathews, William G.

    2009-12-01

    We describe the infrared properties of a large sample of early-type galaxies, comparing data from the Spitzer archive with Ks-band emission from the Two Micron All Sky Survey. While most representations of this data result in correlations with large scatter, we find a remarkably tight relation among colors formed by ratios of luminosities in Spitzer-Multiband Imaging Photometer bands (24, 70, and 160 μm) and the Ks band. Remarkably, this correlation among E and S0 galaxies follows that of nearby normal galaxies of all morphological types. In particular, the tight infrared color-color correlation for S0 galaxies alone follows that of the entire Hubble sequence of normal galaxies, roughly in order of galaxy type from ellipticals to spirals to irregulars. The specific star formation rate (SFR) of S0 galaxies estimated from the 24 μm luminosity increases with decreasing K-band luminosity (or stellar mass) from essentially zero, as with most massive ellipticals, to rates typical of irregular galaxies. Moreover, the luminosities of the many infrared-luminous S0 galaxies can significantly exceed those of the most luminous (presumably post-merger) E galaxies. SFRs in the most infrared-luminous S0 galaxies approach 1-10 solar masses per year. Consistently, with this picture we find that while most early-type galaxies populate an infrared red sequence, about 24% of the objects (mostly S0s) are in an infrared blue cloud together with late-type galaxies. For those early-type galaxies also observed at radio frequencies, we find that the far-infrared luminosities correlate with the mass of neutral and molecular hydrogen, but the scatter is large. This scatter suggests that the star formation may be intermittent or that similar S0 galaxies with cold gaseous disks of nearly equal mass can have varying radial column density distributions that alter the local and global SFRs.

  3. Near-Infrared Faint Galaxies in the Subaru Deep Field: Comparing the Theory with Observations for Galaxy Counts, Colors, and Size Distributions to K ~ 24.5

    NASA Astrophysics Data System (ADS)

    Totani, Tomonori; Yoshii, Yuzuru; Maihara, Toshinori; Iwamuro, Fumihide; Motohara, Kentaro

    2001-10-01

    Galaxy counts in the K band, (J-K) colors, and apparent size distributions of faint galaxies in the Subaru Deep Field (SDF) down to K~24.5 were studied in detail. Special attention has been paid to take into account various selection effects, including the cosmological dimming of surface brightness, to avoid any systematic bias that may be the origin of controversy in previously published results. We also tried to be very careful about systematic model uncertainties; we present a comprehensive survey of these systematic uncertainties and dependence on various parameters, and we have shown that the dominant factors to determine galaxy counts in this band are cosmology and number evolution. We found that the pure luminosity evolution (PLE) model is very consistent with all the SDF data down to K~22.5, without any evidence for number or size evolution in a low-density, Λ-dominated flat universe, which is now favored by various cosmological observations. On the other hand, a number evolution of galaxies with η~2, when invoked as the luminosity conserving mergers as φ*~(1+z)η and L*~(1+z)-η for all types of galaxies, is necessary to explain the data in the Einstein-de Sitter universe. If the popular Λ-dominated universe is taken for granted, our result then gives a strong constraint on the number evolution of giant elliptical or early-type galaxies to z~1-2 that must be met by any models in the hierarchically clustering universe, since such galaxies are the dominant population in this magnitude range (K<~22.5). A number evolution with η~1 is already difficult to reconcile with the data in this universe. On the other hand, number evolution of late-type galaxies and/or dwarf galaxies, which has been suggested by previous studies of optical galaxies, is allowed from the data. In the fainter magnitude range of K>~22.5, we found a slight excess of observed counts over the prediction of the PLE model when elliptical galaxies are treated as a single population. We

  4. Deep Fabry-Perot Hα observations of two Sculptor group galaxies, NGC 247 and 300

    NASA Astrophysics Data System (ADS)

    Hlavacek-Larrondo, J.; Marcelin, M.; Epinat, B.; Carignan, C.; de Denus-Baillargeon, M.-M.; Daigle, O.; Hernandez, O.

    2011-09-01

    It has been suggested that diffuse ionized gas can extend all the way to the end of the H I disc, and even beyond, such as in the case of the warped galaxyNGC 253 (Bland-Hawthorn et al.). Detecting ionized gas at these radii could carry significant implications as to the distribution of dark matter in galaxies. With the aim of detecting this gas, we carried out a deep Hα kinematical analysis of two Sculptor group galaxies, NGC 247 and 300. The Fabry-Perot data were taken at the 36-cm Marseille Telescope in La Silla, Chile, offering a large field of view. With almost 20 hours of observations for each galaxy, very faint diffuse emission is detected. Typical emission measures of 0.1 cm-6 pc are reached. For NGC 247, emission extending up to a radius comparable with that of the H I disc (r˜ 13 arcmin) is found, but no emission is seen beyond the H I disc. For NGC 300, we detect ionized gas on the entirety of our field of view (rmax˜ 14 arcmin), and find that the bright H II regions are embedded in a diffuse background. Using the deep data, extended optical rotation curves are obtained, as well as mass models. These are the most extended optical rotation curves thus far for these galaxies. We find no evidence suggesting that NGC 247 has a warped disc, and to account for our non-detection of Hα emission beyond its H I disc, as opposed to the warped galaxy NGC 253, our results favour the model in which, only through a warp, ionization by hot young stars in the central region of a galaxy can let photons escape and ionize the interstellar medium in the outer parts.

  5. BLAST OBSERVATIONS OF RESOLVED GALAXIES: TEMPERATURE PROFILES AND THE EFFECT OF ACTIVE GALACTIC NUCLEI ON FIR TO SUBMILLIMETER EMISSION

    SciTech Connect

    Wiebe, Donald V.; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Pascale, Enzo; Bock, James J.; Devlin, Mark J.; Dicker, Simon; Klein, Jeff; Rex, Marie; Gundersen, Joshua O.; Hughes, David H.; Martin, Peter G.; Netterfield, Calvin B.; Olmi, Luca; Patanchon, Guillaume

    2009-12-20

    Over the course of two flights, the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) made resolved maps of seven nearby (<25 Mpc) galaxies at 250, 350, and 500 mum. During its 2005 June flight from Sweden, BLAST observed a single nearby galaxy, NGC 4565. During the 2006 December flight from Antarctica, BLAST observed the nearby galaxies NGC 1097, NGC 1291, NGC 1365, NGC 1512, NGC 1566, and NGC 1808. We fit physical dust models to a combination of BLAST observations and other available data for the galaxies observed by Spitzer. We fit a modified blackbody to the remaining galaxies to obtain total dust mass and mean dust temperature. For the four galaxies with Spitzer data, we also produce maps and radial profiles of dust column density and temperature. We measure the fraction of BLAST detected flux originating from the central cores of these galaxies and use this to calculate a 'core fraction', an upper limit on the 'active galactic nucleus fraction' of these galaxies. We also find our resolved observations of these galaxies give a dust mass estimate 5-19 times larger than an unresolved observation would predict. Finally, we are able to use these data to derive a value for the dust mass absorption coefficient of kappa = 0.29 +- 0.03 m{sup 2} kg{sup -1} at 250 mum. This study is an introduction to future higher-resolution and higher-sensitivity studies to be conducted by Herschel and SCUBA-2.

  6. Deep Galex Observations of the Coma Cluster: Source Catalog and Galaxy Counts

    NASA Technical Reports Server (NTRS)

    Hammer, D.; Hornschemeier, A. E.; Mobasher, B.; Miller, N.; Smith, R.; Arnouts, S.; Milliard, B.; Jenkins, L.

    2010-01-01

    We present a source catalog from deep 26 ks GALEX observations of the Coma cluster in the far-UV (FUV; 1530 Angstroms) and near-UV (NUV; 2310 Angstroms) wavebands. The observed field is centered 0.9 deg. (1.6 Mpc) south-west of the Coma core, and has full optical photometric coverage by SDSS and spectroscopic coverage to r-21. The catalog consists of 9700 galaxies with GALEX and SDSS photometry, including 242 spectroscopically-confirmed Coma member galaxies that range from giant spirals and elliptical galaxies to dwarf irregular and early-type galaxies. The full multi-wavelength catalog (cluster plus background galaxies) is 80% complete to NUV=23 and FUV=23.5, and has a limiting depth at NUV=24.5 and FUV=25.0 which corresponds to a star formation rate of 10(exp -3) solar mass yr(sup -1) at the distance of Coma. The GALEX images presented here are very deep and include detections of many resolved cluster members superposed on a dense field of unresolved background galaxies. This required a two-fold approach to generating a source catalog: we used a Bayesian deblending algorithm to measure faint and compact sources (using SDSS coordinates as a position prior), and used the GALEX pipeline catalog for bright and/or extended objects. We performed simulations to assess the importance of systematic effects (e.g. object blends, source confusion, Eddington Bias) that influence source detection and photometry when using both methods. The Bayesian deblending method roughly doubles the number of source detections and provides reliable photometry to a few magnitudes deeper than the GALEX pipeline catalog. This method is also free from source confusion over the UV magnitude range studied here: conversely, we estimate that the GALEX pipeline catalogs are confusion limited at NUV approximately 23 and FUV approximately 24. We have measured the total UV galaxy counts using our catalog and report a 50% excess of counts across FUV=22-23.5 and NUV=21.5-23 relative to previous GALEX

  7. Integral field spectroscopy of a sample of nearby galaxies. I. Sample, observations, and data reduction

    NASA Astrophysics Data System (ADS)

    Mármol-Queraltó, E.; Sánchez, S. F.; Marino, R. A.; Mast, D.; Viironen, K.; Gil de Paz, A.; Iglesias-Páramo, J.; Rosales-Ortega, F. F.; Vilchez, J. M.

    2011-10-01

    Aims: Integral field spectroscopy (IFS) is a powerful approach to studying nearby galaxies since it enables a detailed analysis of their resolved physical properties. Here we present our study of a sample of nearby galaxies selected to exploit the two-dimensional information provided by the IFS. Methods: We observed a sample of 48 galaxies from the local universe with the PPaK integral field spectroscopy unit (IFU), of the PMAS spectrograph, mounted at the 3.5 m telescope at Calar Alto Observatory (Almeria, Spain). Two different setups were used during these studies (low - V300 - and medium - V600 - resolution mode) covering a spectral range of around 3700-7000 ÅÅ. We developed a full automatic pipeline for the data reduction, which includes an analysis of the quality of the final data products. We applied a decoupling method to obtain the ionised gas and stellar content of these galaxies, and derive the main physical properties of the galaxies. To assess the accuracy in the measurements of the different parameters, we performed a set of simulations to derive the expected relative errors obtained with these data. In addition, we extracted spectra for two types of aperture, one central and another integrated over the entire galaxy, from the datacubes. The main properties of the stellar populations and ionised gas of these galaxies and an estimate of their relative errors are derived from those spectra, as well as from the whole datacubes. Results: We compare the central spectrum extracted from our datacubes and the SDSS spectrum for each of the galaxies for which this is possible, and find close agreement between the derived values for both samples. We find differences on the properties of galaxies when comparing a central and an integrated spectra, showing the effects of the extracted aperture on the interpretation of the data. Finally, we present two-dimensional maps of some of the main properties derived with the decoupling procedure. Based on observations

  8. Similarity and dimensional theory for galaxies: Explanation of long-known results of observations

    NASA Astrophysics Data System (ADS)

    Golitsyn, G. S.

    2017-08-01

    A practical extension of the similarity and dimensional theory to the case of several similarity parameters is proposed. On this basis, for galaxies an explanation is given for the empirical correlations noticed in the last quarter of the 20th century: the Tully-Fisher relation, the concept of a fundamental plane, etc. For galaxies, apart from the virial, there is another similarity parameter whose choice is arbitrary. Here, it is introduced in the simplest form for an empirical determination:Π1 = U 0/ U d, U 0 is the observed velocity, the scale U d = ( GL)1/5, where L is the object luminosity, G is the gravitational constant.

  9. HUBBLE SPACE TELESCOPE Observations of the Host Galaxy of GRB 970508

    NASA Astrophysics Data System (ADS)

    Fruchter, A. S.; Pian, E.; Gibbons, R.; Thorsett, S. E.; Ferguson, H.; Petro, L.; Sahu, K. C.; Livio, M.; Caraveo, P.; Frontera, F.; Kouveliotou, C.; Macchetto, D.; Palazzi, E.; Pedersen, H.; Tavani, M.; van Paradijs, J.

    2000-12-01

    We report on observations of the field of GRB 970508 made in 1998 early August, 454 days after outburst, with the STIS CCD camera on board the Hubble Space Telescope (HST). The images, taken in open filter (50CCD) mode, clearly reveal the presence of a galaxy that was overwhelmed in earlier (1997 June) HST images by emission from the optical transient (OT). The galaxy is regular in shape: after correcting for the HST/STIS PSF, it is well fitted by an exponential disk with a scale length of 0.046"+/-0.006" and an ellipticity of 0.70+/-0.07. All observations are marginally consistent with a continuous decline in OT emission as t-1.3 beginning 2 days after outburst; however, we find no direct evidence in the late-time HST image for emission from the OT, and the surface brightness profile of the galaxy is most regular if we assume that the OT emission is negligible, suggesting that the OT may have faded more rapidly at late times than is predicted by the power-law decay. Due to the wide bandwidth of the STIS clear mode, the estimated magnitude of the galaxy is dependent on the galaxy spectrum that is assumed. Using colors obtained from late-time ground-based observations to constrain the spectrum, we find V=25.4+/-0.15, a few tenths of a magnitude brighter than earlier ground-based estimates that were obtained by observing the total light of the galaxy and the OT and then subtracting the estimated OT brightness, assuming that it fades as a single power law. This again suggests that the OT may have faded faster at late time than the power law predicts. The position of the OT agrees with that of the isophotal center of the galaxy to 0.01", which, at the galaxy redshift z=0.83, corresponds to an offset from the center of the host of <~70 pc. This remarkable agreement raises the possibility that the gamma-ray burst may have been associated with either an active galactic nucleus or a nuclear starburst.

  10. HUBBLE SPACE TELESCOPE Observations of the Local Group Dwarf Galaxy Leo I

    NASA Astrophysics Data System (ADS)

    Gallart, Carme; Freedman, Wendy L.; Mateo, Mario; Chiosi, Cesare; Thompson, Ian B.; Aparicio, Antonio; Bertelli, Gianpaolo; Hodge, Paul W.; Lee, Myung G.; Olszewski, Edward W.; Saha, Abhijit; Stetson, Peter B.; Suntzeff, Nicholas B.

    1999-04-01

    We present deep HST F555W (V) and F814W (I) observations of a central field in the Local Group dwarf spheroidal (dSph) galaxy Leo I. The resulting color-magnitude diagram (CMD) reaches I~=26 and reveals the oldest ~=10-15 Gyr old turnoffs. Nevertheless, a horizontal branch is not obvious in the CMD. Given the low metallicity of the galaxy, this likely indicates that the first substantial star formation in the galaxy may have been somehow delayed in Leo I in comparison with the other dSph satellites of the Milky Way. The subgiant region is well and uniformly populated from the oldest turnoffs up to the 1 Gyr old turnoff, indicating that star formation has proceeded in a continuous way, with possible variations in intensity but no big gaps between successive bursts, over the galaxy's lifetime. The structure of the red clump of core He-burning stars is consistent with the large amount of intermediate-age population inferred from the main sequence and the subgiant region. In spite of the lack of gas in Leo I, the CMD clearly shows star formation continuing until 1 Gyr ago and possibly until a few hundred Myr ago in the central part of the galaxy.

  11. Optical studies of galaxies in clusters. Observations of spirals in Virgo. III.

    NASA Astrophysics Data System (ADS)

    Sperandio, M.; Chincarini, G.; Rampazzo, R.; de Souza, R.

    1995-04-01

    We present the analysis of the rotation curves of a sample of 32 spiral galaxies derived from the spectroscopic observations of a sample of 47 galaxies. For 15 galaxies we were either unable to detect emission lines or measure a reasonably good rotation curve. Of the 32 rotation curves 23 are of galaxies member of the Virgo Cluster and 9 selected from the "field". Analysis of mass and density distribution have been obtained. The mass distribution of cluster galaxies belongs to the Type III proposed by Burstein & Rubin (1985) with few exceptions (NGC 4519 Type I, NGC 2280, NGC 4189, NGC 5861, NGC 6070 Type II) and, is unrelated to the morphological type. Density distribution curves from equidensity surface spheroids model, computed for the Virgo sample, result to be primarily composed of three classes. Rotation curves, none of which shows a peculiar trend, have been parametrized using the criteria introduced by Whitmore et al. (1984). The clustercentric distance of Virgo spirals does not correlate neither with OG nor with OGML in agreement with the findings of Distefano et al. (1990) and Amram et al. (1993, 1994) for other clusters.

  12. Extending ALFALFA: Reducing L-Band Wide Observations of Optically Selected Galaxies

    NASA Astrophysics Data System (ADS)

    Smith, Evan; O'Donoghue, Aileen A.; Haynes, Martha P.; Koopmann, Rebecca A.; Undergraduate ALFALFA Team

    2016-01-01

    Observations of galaxies in the Virgo Cluster were completed at the Arecibo Observatory in the spring and summer of 2015. 161 targets were observed, selected by photometry criteria such as magnitude and shape from the Sloan Digital Sky Survey. The targets, some too dim to be detected by Arecibo's ALFA drift scanner, were observed with the L-Band Wide detector. Once reductions in an IDL environment were done, these data were matched to the targets from the Sloan Digital Sky Survey and the GALEX/MAST catalog. 115 of the 161 targets observed had positive detections, a 71% success rate. Comparing the galaxies that were detected against the galaxies that were not detected (by the L-Band Wide receiver) will allow us to refine our method of using photometric data to select HI-rich galaxies in the 2000 km/s to 9000 km/s range to refine our selection for the Arecibo Pisces-Perseus Supercluster Survey (APPSS), which uses the same method of target selection.

  13. The impact of compact radio sources on their host galaxies: observations

    NASA Astrophysics Data System (ADS)

    Tadhunter, C.

    2016-02-01

    I review the observational evidence that CSS/GPS radio sources have a significant impact on the evolution of their host galaxies, particularly on the kpc-scales of the galaxy bulges. Starting with an overview of the observational evidence for jet-cloud interactions and warm ionised outflows in CSS/GPS sources, I then consider the challenges involved in quantifying the feedback effect of the warm outflows in terms of their mass outflow rates and kinetic powers. For the best-observed cases it is shown that the warm outflows may have a major negative feedback effect in the very central regions, but probably lack the power to heat and eject the full cool ISM contents of the host galaxies. In contrast, the recently-discovered neutral and molecular outflows are more massive and powerful and therefore carry more destructive potential. However, the feedback effect of such outflows is not necessarily negative: there is now clear observational evidence that the molecular outflows are formed as the hot, compressed gas cools behind fast shocks driven into the ISM by the relativistic jets. The natural endpoint of this process is the formation of stars. Therefore, jet-induced star formation may be a significant process in CSS/GPS radio galaxies. Finally, I discuss whether CSS/GPS sources are ``imposters'' in flux-limited radio samples, due the flux boosting of the radio sources by strong jet-cloud interactions in the early stages of radio source evolution.

  14. NIRcam-NIRSpec GTO Observations of Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Rieke, Marcia J.; Ferruit, Pierre; Alberts, Stacey; Bunker, Andrew; Charlot, Stephane; Chevallard, Jacopo; Dressler, Alan; Egami, Eiichi; Eisenstein, Daniel; Endsley, Ryan; Franx, Marijn; Frye, Brenda L.; Hainline, Kevin; Jakobsen, Peter; Lake, Emma Curtis; Maiolino, Roberto; Rix, Hans-Walter; Robertson, Brant; Stark, Daniel; Williams, Christina; Willmer, Christopher; Willott, Chris J.

    2017-06-01

    The NIRSpec and and NIRCam GTO Teams are planning a joint imaging and spectroscopic study of the high redshift universe. By virtue of planning a joint program which includes medium and deep near- and mid-infrared imaging surveys and multi-object spectroscopy (MOS) of sources in the same fields, we have learned much about planning observing programs for each of the instruments and using them in parallel mode to maximize photon collection time. The design and rationale for our joint program will be explored in this talk with an emphasis on why we have chosen particular suites of filters and spectroscopic resolutions, why we have chosen particular exposure patterns, and how we have designed the parallel observations. The actual observations that we intend on executing will serve as examples of how to layout mosaics and MOS observations to maximize observing efficiency for surveys with JWST.

  15. Improving Type Ia Supernova Standard Candle Cosmology Measurements Using Observations of Early-Type Host Galaxies

    NASA Astrophysics Data System (ADS)

    Meyers, Joshua Evan

    Type Ia supernovae (SNe Ia) are the current standard-bearers for dark energy but face several hurdles for their continued success in future large surveys. For example, spectroscopic classification of the myriad SNe soon to be discovered will not be possible, and systematics from uncertainties in dust corrections and the evolution of SN demographics and/or empirical calibrations used to standardize SNe Ia must be studied. Through the identification of low-dust host galaxies and through increased understanding of both the SN - progenitor connections and empirical calibrations, host galaxy information may offer opportunities to improve the cosmological utility of SNe Ia. The first half of this thesis analyzes the sample of SNe Ia discovered by the Hubble Space Telescope (HST) Cluster Supernova Survey augmented with HST-observed SNe Ia in the Great Observatories Origins Deep Survey (GOODS) fields. Correlations between properties of SNe and their host galaxies are examined at high redshift. Using galaxy color and quantitative morphology to determine the red sequence in 25 clusters, a model is developed to distinguish passively evolving early-type galaxies from star-forming galaxies in both clusters and the field. With this approach, 6 early-type cluster member hosts and 11 SN Ia early-type field hosts are identified. For the first time at z > 0.9, the correlation between host galaxy type and the rise and fall time of SN Ia light curves is confirmed. The relatively simple spectral energy distributions of early-type galaxies also enables stellar mass measurements for these hosts. In combination with literature host mass measurements, these measurements are used to show, at z > 0.9, a hint of the correlation between host mass and Hubble residuals reported at lower redshift. By simultaneously fitting cluster galaxy formation histories and dust content to the scatter of the cluster red sequences, it is shown that dust reddening of early-type cluster SN hosts is likely less

  16. Observational Studies of the Angular Structure of the Radio Galaxy 3C 234 at Decameter Wavelengths

    NASA Astrophysics Data System (ADS)

    Megn, A. V.; Braude, S. Ya.; Rashkovskiy, S. L.; Sharykin, N. K.; Shepelev, V. A.; Inyutin, G. A.; Vashchishin, R. V.; Brazhenko, A. I.; Bulatsen, V. G.

    2003-12-01

    An analysis of the angular structure of the radio galaxy 3C 234 at decameter wavelengths based on data obtained on the URAN-1 and URAN-2 interferometers is presented. Four of the five model components that describe the radio-brightness distribution at centimeter wavelengths are observed at decameter wavelengths: two compact components and two neighboring extended components. The fifth, undetected, component is the most extended, and encompasses the central region of the radio source, including the nucleus of the galaxy. Self-absorption is detected in the compact components, whose angular sizes are determined to be 0.27±0.03″ (northeast component) and 0.55±0.05″ (southwest component), in agreement with direct measurements at centimeter wavelengths. Most of the decameter emission of the radio galaxy is associated with its extended components.

  17. New X-ray and radio observations of the galaxy cluster A2319

    NASA Technical Reports Server (NTRS)

    Grindlay, J. E.; Parsignault, D. R.; Gursky, H.; Brinkman, A. C.; Heise, J.; Harris, D. E.

    1977-01-01

    A significantly improved position for the X-ray source 3U 1921 + 43 has been obtained by ANS and Uhuru. The combined ANS-Uhuru error box is only about 7 by 7 arcmin and is centered on the cD galaxy in the Abell 2319 cluster of galaxies. Radio observations of this cluster indicate that the emission at 610 MHz includes several discrete sources and a weak extended component. This strengthens the general association between extended radio halos and X-ray emission from clusters of galaxies. The radio halo fills the X-ray error box and is consistent with the limits reported for the angular size of the X-ray source

  18. CO OBSERVATIONS OF THE HOST GALAXY OF GRB 000418 AT z = 1.1

    SciTech Connect

    Hatsukade, B.; Ohta, K.; Kohno, K.; Endo, A.; Nakanishi, K.

    2011-09-01

    We performed CO (J = 2-1) observations of the host galaxy of GRB 000418 at z = 1.1181 with the Plateau de Bure Interferometer. Previous studies show that the host galaxy has properties similar to those of an ultraluminous infrared galaxy (ULIRG). The star formation rate (SFR) of the host galaxy as derived from submillimeter and radio continuum emission is a few 100 M{sub sun} yr{sup -1}, which is an order of magnitude greater than the SFR derived from optical line emission. The large discrepancy between the SFRs derived from different observing wavelengths indicates the presence of a bulk of dust-obscured star formation and molecular gas that is enough to sustain the intense star formation. We failed to detect CO emission and derived 2{sigma} upper limits on the velocity-integrated CO (2-1) luminosity of L'{sub CO} < 6.9 x 10{sup 9} K km s{sup -1} pc{sup 2} and the molecular gas mass of M{sub H{sub 2}}< 5.5x10{sup 9} M{sub sun} by adopting a velocity width of 300 km s{sup -1} and a CO-to-H{sub 2} conversion factor of {alpha}{sub CO} = 0.8 M{sub sun} (K km s{sup -1} pc{sup 2}){sup -1}, which are standard values for ULIRGs. The lower limit on the ratio of far-infrared luminosity to CO luminosity, a measure of the star formation efficiency, is higher compared to that of other gamma-ray burst hosts and other galaxy populations, which is consistent with active star formation taking place in this galaxy.

  19. Galaxy Morphology From the UV to the FIR: An Intercomparison of Recent Observations From Space With New Radiative Transfer Models

    NASA Technical Reports Server (NTRS)

    (CIT), Barry Madore

    1995-01-01

    We will present the latest multiwavelength observations of spiral galaxies made from space and from the ground covering the electromagnetic spectrum from the far ultraviolet (ASTRO-2 UIT observations) through the optical, and out to the far infrared (IRAS). Comparisons with recent theoretical models for the radiative transfer of stellar light through a three-dimensional dusty galaxy will be presented.

  20. Feedback and Brightest Cluster Galaxy Formation: ACS Observations of the Radio Galaxy TN J1338-1942 at z = 4.1

    NASA Astrophysics Data System (ADS)

    Zirm, Andrew W.; Overzier, R. A.; Miley, G. K.; Blakeslee, J. P.; Clampin, M.; De Breuck, C.; Demarco, R.; Ford, H. C.; Hartig, G. F.; Homeier, N.; Illingworth, G. D.; Martel, A. R.; Röttgering, H. J. A.; Venemans, B.; Ardila, D. R.; Bartko, F.; Benítez, N.; Bouwens, R. J.; Bradley, L. D.; Broadhurst, T. J.; Brown, R. A.; Burrows, C. J.; Cheng, E. S.; Cross, N. J. G.; Feldman, P. D.; Franx, M.; Golimowski, D. A.; Goto, T.; Gronwall, C.; Holden, B.; Infante, L.; Kimble, R. A.; Krist, J. E.; Lesser, M. P.; Mei, S.; Menanteau, F.; Meurer, G. R.; Motta, V.; Postman, M.; Rosati, P.; Sirianni, M.; Sparks, W. B.; Tran, H. D.; Tsvetanov, Z. I.; White, R. L.; Zheng, W.

    2005-09-01

    We present deep optical imaging of the z=4.1 radio galaxy TN J1338-1942, obtained using the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope, as well as ground-based near-infrared imaging data from the European Southern Observatory (ESO) Very Large Telescope (VLT). The radio galaxy is known to reside within a large galaxy overdensity (both in physical extent and density contrast). There is good evidence that this ``protocluster'' region is the progenitor of a present-day rich galaxy cluster. TN J1338 is the dominant galaxy in the protocluster in terms of size and luminosity (in both the optical and near-infrared) and therefore seems destined to evolve into the brightest cluster galaxy. The high spatial resolution ACS images reveal several kiloparsec-scale features within and around the radio galaxy. The continuum light is aligned with the radio axis and is resolved into two clumps in the i775 and z850 bands. These components have luminosities ~109 Lsolar and sizes of a few kpc. The estimated nebular continuum, scattered light, synchrotron- and inverse Compton-scattering contributions to the aligned continuum light are only a few percent of the observed total, indicating that the observed flux is likely dominated by forming stars. The estimated star formation rate for the whole radio galaxy is ~200 Msolar yr-1. A simple model in which the jet has triggered star formation in these continuum knots is consistent with the available data. A striking, but small, linear feature is evident in the z850 aligned light and may be indicative of a large-scale shock associated with the advance of the radio jet. The rest of the aligned light also seems morphologically consistent with star formation induced by shocks associated with the radio source, as seen in other high-z radio galaxies (e.g., 4C 41.17). An unusual feature is seen in Lyα emission. A wedge-shaped extension emanates from the radio galaxy perpendicularly to the radio axis. This ``wedge

  1. Discordance of the unified scheme with observed properties of quasars and high-excitation galaxies in the 3CRR sample

    SciTech Connect

    Singal, Ashok K.

    2014-07-01

    We examine the consistency of the unified scheme of Fanaroff-Riley type II radio galaxies and quasars with their observed number and size distributions in the 3CRR sample. We separate the low-excitation galaxies from the high-excitation ones, as the former might not harbor a quasar within and thus may not be partaking in the unified scheme models. In the updated 3CRR sample, at low redshifts (z < 0.5), the relative number and luminosity distributions of high-excitation galaxies and quasars roughly match the expectations from the orientation-based unified scheme model. However, a foreshortening in the observed sizes of quasars, which is a must in the orientation-based model, is not seen with respect to radio galaxies even when the low-excitation galaxies are excluded. This dashes the hope that the unified scheme might still work if one includes only the high-excitation galaxies.

  2. Emission Line Galaxies in the STIS Parallel Survey. 1; Observations and Data Analysis

    NASA Technical Reports Server (NTRS)

    Teplitz, Harry I.; Collins, Nicholas R.; Gardner, Jonathan P.; Hill, Robert S.; Heap, Sara R.; Lindler, Don J.; Rhodes, Jason; Woodgate, Bruce E.

    2002-01-01

    In the first three years of operation STIS obtained slitless spectra of approximately 2500 fields in parallel to prime HST observations as part of the STIS Parallel Survey (SPS). The archive contains approximately 300 fields at high galactic latitude (|b| greater than 30) with spectroscopic exposure times greater than 3000 seconds. This sample contains 220 fields (excluding special regions and requiring a consistent grating angle) observed between 6 June 1997 and 21 September 2000, with a total survey area of approximately 160 square arcminutes. At this depth, the SPS detects an average of one emission line galaxy per three fields. We present the analysis of these data, and the identification of 131 low to intermediate redshift galaxies detected by optical emission lines. The sample contains 78 objects with emission lines that we infer to be redshifted [OII]3727 emission at 0.43 < z < 1.7. The comoving number density of these objects is comparable to that of Halpha-emitting galaxies in the NICMOS parallel observations. One quasar and three probable Seyfert galaxies are detected. Many of the emission-line objects show morphologies suggestive of mergers or interactions. The reduced data are available upon request from the authors.

  3. Chandra Observations of NGC 4698: A Seyfert 2 Galaxy with No Absorption

    NASA Technical Reports Server (NTRS)

    Georgantopoulos, I.; Zezas, A.

    2003-01-01

    We present Chandra ACIS-S observations of the enigmatic Seyfert 2 galaxy NGC 4698. This object, together with several other bona fide Seyfert 2 galaxies, shows no absorption in the low spatial resolution ASCA data, in contrast to the standard unification models. Our Chandra observations of NGC 4698 probe directly the nucleus, allowing us to check whether nearby sources contaminate the ASCA spectrum. Indeed, the Chandra observations show that the ASCA spectrum is dominated by two nearby AGNs. The X-ray flux of NGC 4698 is dominated by a nuclear source with luminosity L(sub 0.3-8 keV) approximately 10(exp 39) ergs per second, coincident with the radio nucleus. Its spectrum is well represented by a power law, GAMMA approximately equal to 2.2, obscured by a small column density of 5 x 10(exp 20) per square centimeter, suggesting that NGC 4698 is an atypical Seyfert galaxy. On the basis of its low luminosity, we then interpret NGC 4698 as a Seyfert galaxy that lacks a broad-line region.

  4. VALIDATION OF THE EQUILIBRIUM MODEL FOR GALAXY EVOLUTION TO z ∼ 3 THROUGH MOLECULAR GAS AND DUST OBSERVATIONS OF LENSED STAR-FORMING GALAXIES

    SciTech Connect

    Saintonge, Amélie; Lutz, Dieter; Genzel, Reinhard; Tacconi, Linda J.; Berta, Stefano; Förster Schreiber, Natascha M.; Poglitsch, Albrecht; Sturm, Eckhard; Wuyts, Eva; Wuyts, Stijn; Magnelli, Benjamin; Nordon, Raanan; Baker, Andrew J.; Bandara, Kaushala

    2013-11-20

    We combine IRAM Plateau de Bure Interferometer and Herschel PACS and SPIRE measurements to study the dust and gas contents of high-redshift star-forming galaxies. We present new observations for a sample of 17 lensed galaxies at z = 1.4-3.1, which allow us to directly probe the cold interstellar medium of normal star-forming galaxies with stellar masses of ∼10{sup 10} M{sub ☉}, a regime otherwise not (yet) accessible by individual detections in Herschel and molecular gas studies. The lensed galaxies are combined with reference samples of submillimeter and normal z ∼ 1-2 star-forming galaxies with similar far-infrared photometry to study the gas and dust properties of galaxies in the SFR-M{sub *}-redshift parameter space. The mean gas depletion timescale of main-sequence (MS) galaxies at z > 2 is measured to be only ∼450 Myr, a factor of ∼1.5 (∼5) shorter than at z = 1 (z = 0), in agreement with a (1 + z){sup –1} scaling. The mean gas mass fraction at z = 2.8 is 40% ± 15% (44% after incompleteness correction), suggesting a flattening or even a reversal of the trend of increasing gas fractions with redshift recently observed up to z ∼ 2. The depletion timescale and gas fractions of the z > 2 normal star-forming galaxies can be explained under the 'equilibrium model' for galaxy evolution, in which the gas reservoir of galaxies is the primary driver of the redshift evolution of specific star formation rates. Due to their high star formation efficiencies and low metallicities, the z > 2 lensed galaxies have warm dust despite being located on the star formation MS. At fixed metallicity, they also have a gas-to-dust ratio 1.7 times larger than observed locally when using the same standard techniques, suggesting that applying the local calibration of the δ{sub GDR}-metallicity relation to infer the molecular gas mass of high-redshift galaxies may lead to systematic differences with CO-based estimates.

  5. A deep Chandra observation of the interacting star-forming galaxy Arp 299

    NASA Astrophysics Data System (ADS)

    Anastasopoulou, K.; Zezas, A.; Ballo, L.; Della Ceca, R.

    2016-08-01

    We present results from a 90 ks Chandra ACIS-S observation of the X-ray luminous interacting galaxy system Arp 299 (NGC 3690/IC 694). We detect 25 discrete X-ray sources with luminosities above ˜4.0 × 1038 erg s-1 covering the entire Ultra Luminous X-ray source (ULX) regime. Based on the hard X-ray spectra of the non-nuclear discrete sources identified in Arp 299, and their association with young, actively star-forming region of Arp 299 we identify them as HMXBs. We find in total 20 off-nuclear sources with luminosities above the ULX limit, 14 of which are point-like sources. Furthermore we observe a marginally significant deficit in the number of ULXs, with respect to the number expected from scaling relations of X-ray binaries with the star formation rate (SFR). Although the high metallicity of the galaxy could result in lower ULX numbers, the good agreement between the observed total X-ray luminosity of ULXs, and that expected from the relevant scaling relation indicates that this deficit could be the result of confusion effects. The integrated spectrum of the galaxy shows the presence of a hot gaseous component with kT = 0.72 ± 0.03 keV, contributing ˜20 per cent of the soft (0.1-2.0 keV) unabsorbed luminosity of the galaxy. A plume of soft X-ray emission in the west of the galaxy indicates a large scale outflow. We find that the AGN in NGC 3690 contributes only 22 per cent of the observed broad-band X-ray luminosity of Arp 299.

  6. GBT CO observations of two ACT dusty star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Rivera, Jesus; Baker, Andrew J.; Wilson, Grant; Yun, Min Su; Frayer, David T.; Harris, Andrew I.; Marriage, Tobias; Gralla, Megan; Su, Ting; Aretxaga, Itziar; Hall, Kirsten; Hughes, David; Hughes, John Patrick; Keeton, Charles R.; Menanteau, Felipe; Montana, Alfredo; Tagore, Amitpal; Tang, Yuping; Atacama Cosmology Telescope Team

    2017-01-01

    We report new observations of low-J CO emission lines in two dusty star-forming galaxies (DSFGs) originally detected in a 470 deg^2 survey with the Atacama Cosmology Telescope (ACT). Continuum and spectral line followup of the DSFG sample from which these two objects are drawn is allowing us to characterize the physical conditions and redshift distribution of this important population. The new observations, obtained with the Ka and Q-band receivers on the Robert C. Byrd Green Bank Telescope (GBT), complement higher-J CO observations with the Large Millimeter Telescope (LMT) and the IRAM 30m telescope, trace the galaxies' cold gas reservoirs, and enable estimates of lensing magnifications within modest uncerstainties.This work has been supported by a Student Observing Support grant from the National Radio Astronomy Observatory.

  7. UV Observations of the Galaxy Cluster Abell 1795 with the Optical Monitor on XMM-Newton

    NASA Technical Reports Server (NTRS)

    Mittaz, J. P. D.; Kaastra, J. S.; Tamura, T.; Fabian, A. C.; Mushotzky, F.; Peterson, J. R.; Ikebe, Y.; Lumb, D. H.; Paerels, F.; Stewart, G.

    2000-01-01

    We present the results of an analysis of broad band UV observations of the central regions of Abell 1795 observed with the optical monitor on XMM-Newton. As have been found with other UV observations of the central regions of clusters of galaxies, we find evidence for star formation. However, we also find evidence for absorption in the cD galaxy on a more extended scale than has been seen with optical imaging. We also report the first UV observation of part of the filamentary structure seen in H-alpha, X-rays and very deep U band imaging. The part of the filament we see is very blue with UV colours consistent with a very early (O/B) stellar population. This is the first direct evidence of a dominant population of early type stars at the centre of Abell 1795 and implies very recent star formation. The relationship of this emission to emission at other wavebands is discussed.

  8. The no-spin zone: rotation versus dispersion support in observed and simulated dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Wheeler, Coral; Pace, Andrew B.; Bullock, James S.; Boylan-Kolchin, Michael; Oñorbe, Jose; Elbert, Oliver D.; Fitts, Alex; Hopkins, Philip F.; Kereš, Dušan

    2017-02-01

    We perform a systematic Bayesian analysis of rotation versus dispersion support (vrot/σ) in 40 dwarf galaxies throughout the local volume (LV) over a stellar mass range of 10^{3.5} M_{⊙}< M_{star }< 108 M_{⊙}. We find that the stars in ˜80 per cent of the LV dwarf galaxies studied - both satellites and isolated systems - are dispersion-supported. In particular, we show that 6/10 isolated dwarfs in our sample have vrot/σ ≲ 1.0, while all have vrot/σ ≲ 2.0. These results challenge the traditional view that the stars in gas-rich dwarf irregulars (dIrrs) are distributed in cold, rotationally supported stellar discs, while gas-poor dwarf spheroidals (dSphs) are kinematically distinct in having dispersion-supported stars. We see no clear trend between vrot/σ and distance to the closest L⋆ galaxy, nor between vrot/σ and M⋆ within our mass range. We apply the same Bayesian analysis to four FIRE hydrodynamic zoom-in simulations of isolated dwarf galaxies (10^9 M_{⊙}< M_{vir}< 10^{10} M_{⊙}) and show that the simulated isolated dIrr galaxies have stellar ellipticities and stellar vrot/σ ratios that are consistent with the observed population of dIrrs and dSphs without the need to subject these dwarfs to any external perturbations or tidal forces. We posit that most dwarf galaxies form as puffy, dispersion-dominated systems, rather than cold, angular-momentum-supported discs. If this is the case, then transforming a dIrr into a dSph may require little more than removing its gas.

  9. Relative merits of different types of rest-frame optical observations to constrain galaxy physical parameters

    NASA Astrophysics Data System (ADS)

    Pacifici, Camilla; Charlot, Stéphane; Blaizot, Jérémy; Brinchmann, Jarle

    2012-04-01

    We present a new approach to constrain galaxy physical parameters from the combined interpretation of stellar and nebular emission in wide ranges of observations. This approach relies on the Bayesian analysis of any type of galaxy spectral energy distribution using a comprehensive library of synthetic spectra assembled using state-of-the-art models of star formation and chemical enrichment histories, stellar population synthesis, nebular emission and attenuation by dust. We focus on the constraints set by five-band ugriz photometry and low- and medium-resolution spectroscopy at rest wavelengths λ= 3600-7400 Å on a few physical parameters of galaxies: the observer-frame absolute r-band stellar mass-to-light ratio, M*/Lr; the fraction of a current galaxy stellar mass formed during the last 2.5 Gyr, fSFH; the specific star formation rate, ψS; the gas-phase oxygen abundance, 12 + log(O/H); the total effective V-band absorption optical depth of the dust, ?; and the fraction of this arising from dust in the ambient interstellar medium, μ. Since these parameters cannot be known a priori for any galaxy sample, we assess the accuracy to which they can be retrieved from observations by simulating 'pseudo-observations' using models with known parameters. Assuming that these models are good approximations of true galaxies, we find that the combined analysis of stellar and nebular emission in low-resolution [50 Å full width at half-maximum (FWHM)] galaxy spectra provides valuable constraints on all physical parameters. The typical uncertainties in high-quality spectra are about 0.13 dex for M*/Lr, 0.23 for fSFH, 0.24 dex for ψS, 0.28 for 12 + log(O/H), 0.64 for ? and 0.16 for μ. The uncertainties in 12 + log(O/H) and ? tighten by about 20 per cent for galaxies with detectable emission lines and by another 45 per cent when the spectral resolution is increased to 5 Å FWHM. At this spectral resolution, the analysis of the combined stellar and nebular emission in the high

  10. The Milky Way Bulge: Observed Properties and a Comparison to External Galaxies

    NASA Astrophysics Data System (ADS)

    Gonzalez, Oscar A.; Gadotti, Dimitri

    The Milky Way bulge offers a unique opportunity to investigate in detail the role that different processes such as dynamical instabilities, hierarchical merging, and dissipational collapse may have played in the history of the Galaxy formation and evolution based on its resolved stellar population properties. Large observation programs and surveys of the bulge are providing for the first time a look into the global view of the Milky Way bulge that can be compared with the bulges of other galaxies, and be used as a template for detailed comparison with models. The Milky Way has been shown to have a boxy/peanut (B/P) bulge and recent evidence seems to suggest the presence of an additional spheroidal component. In this review we summarize the global chemical abundances, kinematics and structural properties that allow us to disentangle these multiple components and provide constraints to understand their origin. The investigation of both detailed and global properties of the bulge now provide us with the opportunity to characterize the bulge as observed in models, and to place the mixed component bulge scenario in the general context of external galaxies. When writing this review, we considered the perspectives of researchers working with the Milky Way and researchers working with external galaxies. It is an attempt to approach both communities for a fruitful exchange of ideas.

  11. Velocities of Warm Galactic Outflows from Synthetic Hα Observations of Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Ceverino, Daniel

    2017-07-01

    The velocity structure imprinted in the Hα emission line profiles contains valuable information about galactic outflows. Using a set of high-resolution zoom-in cosmological simulations of galaxies at z ≃ 2, we generate Hα emission line profiles, taking into account the temperature- dependent Hα emissivity, as well as dust extinction. The Hα line can be described as a sum of two Gaussians, as typically done with observations. In general, its properties are in good agreement with those observed in local isolated galaxies with similar masses and star formation rates, assuming a spatially constant clumping factor of c ≃ 24. Blueshifted outflows are very common in the sample. They extend several kpc above the galaxy discs. They are also spread over the full extent of the discs. However, at small radii, the material with high velocities tends to remain confined within a thick disc, as part of galactic fountains or a turbulent medium, most probably due to the deeper gravitational potential at the galaxy centre.

  12. Velocities of warm galactic outflows from synthetic Hα observations of star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Ceverino, Daniel; Arribas, Santiago; Colina, Luis; Rodríguez Del Pino, Bruno; Dekel, Avishai; Primack, Joel

    2016-08-01

    The velocity structure imprinted in the Hα emission line profiles contains valuable information about galactic outflows. Using a set of high-resolution zoom-in cosmological simulations of galaxies at z ≃ 2, we generate Hα emission line profiles, taking into account the temperature-dependent Hα emissivity, as well as dust extinction. The Hα line can be described as a sum of two Gaussians, as typically done with observations. In general, its properties are in good agreement with those observed in local isolated galaxies with similar masses and star formation rates, assuming a spatially constant clumping factor of c ≃ 24. Blueshifted outflows are very common in the sample. They extend several kpc above the galaxy discs. They are also spread over the full extent of the discs. However, at small radii, the material with high velocities tends to remain confined within a thick disc, as part of galactic fountains or a turbulent medium, most probably due to the deeper gravitational potential at the galaxy centre.

  13. X-ray reflection from black-hole accretion discs with a radially stratified ionisation

    NASA Astrophysics Data System (ADS)

    Svoboda, J.; Domcek, V.; Dovčiak, M.; Guainazzi, M.; Marinucci, A.

    2015-07-01

    Recent X-ray observations have suggested a very high compactness of coronae in Active Galactic Nuclei as well as in X-ray Binaries. The compactness of the source implies that the black-hole accretion disc irradiation is a strong function of radius. We will show how the X-ray spectra are modified assuming the radially stratified ionisation according to the illumination by a point-like source on the black-hole rotational axis. We will discuss how this affects the measurements of the other model parameters, such as spin and radial emissivity. We will show the application of this model to the recent XMM-Newton/NUSTAR data of an active galaxy MCG-6-30-15.

  14. Hubble Space Telescope and Very Large Array Observations of the H2O Gigamaser Galaxy TXS 2226-184.

    PubMed

    Falcke; Wilson; Henkel; Brunthaler; Braatz

    2000-02-10

    We present Hubble Space Telescope/Wide-Field and Planetary Camera 2 images in Halpha + [N ii] lambdalambda6548, 6583 lines and continuum radiation and a VLA map at 8 GHz of the H2O gigamaser galaxy TXS 2226-184. This galaxy has the most luminous H2O maser emission known to date. Our red continuum images reveal a highly elongated galaxy with a dust lane crossing the nucleus. The surface brightness profile is best fitted by a bulge plus exponential disk model, favoring classification as a highly inclined spiral galaxy (i=70&j0;). The color map confirms that the dust lane is aligned with the galaxy major axis and is crossing the putative nucleus. The Halpha + [N ii] map exhibits a gaseous, jetlike structure perpendicular to the nuclear dust lane and the galaxy major axis. The radio map shows compact, steep spectrum emission that is elongated in the same direction as the Halpha + [N ii] emission. By analogy with Seyfert galaxies, we therefore suspect that this alignment reflects an interaction between the radio jet and the interstellar medium. The axes of the nuclear dust disk, the radio emission, and the optical line emission apparently define the axis of the active galactic nucleus. The observations suggest that in this galaxy the nuclear accretion disk, obscuring torus, and large-scale molecular gas layer are roughly coplanar. Our classification of the host galaxy strengthens the trend for megamasers to be found preferentially in highly inclined spiral galaxies.

  15. THE OBSERVED PROPERTIES OF DWARF GALAXIES IN AND AROUND THE LOCAL GROUP

    SciTech Connect

    McConnachie, Alan W.

    2012-07-15

    Positional, structural, and dynamical parameters for all dwarf galaxies in and around the Local Group are presented, and various aspects of our observational understanding of this volume-limited sample are discussed. Over 100 nearby galaxies that have distance estimates reliably placing them within 3 Mpc of the Sun are identified. This distance threshold samples dwarfs in a large range of environments, from the satellite systems of the MW and M31, to the quasi-isolated dwarfs in the outer regions of the Local Group, to the numerous isolated galaxies that are found in its surroundings. It extends to, but does not include, the galaxies associated with the next nearest groups, such as Maffei, Sculptor, and IC 342. Our basic knowledge of this important galactic subset and their resolved stellar populations will continue to improve dramatically over the coming years with existing and future observational capabilities, and they will continue to provide the most detailed information available on numerous aspects of dwarf galaxy formation and evolution. Basic observational parameters, such as distances, velocities, magnitudes, mean metallicities, as well as structural and dynamical characteristics, are collated, homogenized (as far as possible), and presented in tables that will be continually updated to provide a convenient and current online resource. As well as discussing the provenance of the tabulated values and possible uncertainties affecting their usage, the membership and spatial extent of the MW sub-group, M31 sub-group, and the Local Group are explored. The morphological diversity of the entire sample and notable sub-groups is discussed, and timescales are derived for the Local Group members in the context of their orbital/interaction histories. The scaling relations and mean stellar metallicity trends defined by the dwarfs are presented, and the origin of a possible 'floor' in central surface brightness (and, more speculatively, stellar mean metallicity) at

  16. Implications of a variable IMF for the interpretation of observations of galaxy populations

    NASA Astrophysics Data System (ADS)

    Clauwens, Bart; Schaye, Joop; Franx, Marijn

    2016-11-01

    We investigate the effect of a metallicity-dependent stellar initial mass function (IMF), as deduced observationally by Martín-Navarro et al., on the inferred stellar masses and star formation rates (SFRs) of a representative sample of 186 886 SDSS galaxies. Relative to a Chabrier IMF, for which we show the implied masses to be close to minimal, the inferred masses increase in both the low- and high-metallicity regimes due to the addition of stellar remnants and dwarf stars, respectively. The resulting galaxy stellar mass function (GSMF) shifts towards higher masses by 0.5 dex, without affecting the high-mass slope (and thus the need for effective quenching). The implied low-redshift SFR density increases by an order of magnitude. However, these results depend strongly on the assumed IMF parametrization, which is not directly constrained by the observations. Varying the low-end IMF slope instead of the high-end IMF slope, while maintaining the same dwarf-to-giant ratio, results in a much more modest GSMF shift of 0.2 dex and a 10 per cent increase in the SFR density relative to the Chabrier IMF. A bottom-heavy IMF during the late, metal-rich evolutionary stage of a galaxy would help explain the rapid quenching and the bimodality in the galaxy population by on the one hand making galaxies less quenched (due to the continued formation of dwarf stars) and on the other hand reducing the gas consumption time-scale. We conclude that the implications of the observational evidence for a variable IMF could vary from absolutely dramatic to mild but significant.

  17. LBT/LUCIFER OBSERVATIONS OF THE z {approx} 2 LENSED GALAXY J0900+2234

    SciTech Connect

    Bian Fuyan; Fan Xiaohui; Bechtold, Jill; McGreer, Ian D.; Just, Dennis W.; Sand, David J.; Green, Richard F.; Thompson, David; Peng, Chien Y.; Seifert, Walter; Ageorges, Nancy; Buschkamp, Peter; Juette, Marcus; Knierim, Volker

    2010-12-20

    We present rest-frame optical images and spectra of the gravitationally lensed, star-forming galaxy J0900+2234 (z = 2.03). The observations were performed with the newly commissioned LUCIFER1 near-infrared (NIR) instrument mounted on the Large Binocular Telescope. We fitted lens models to the rest-frame optical images and found that the galaxy has an intrinsic effective radius of 7.4 {+-} 0.8 kpc with a lens magnification factor of about 5 for the A and B components. We also discovered a new arc belonging to another lensed high-z source galaxy, which makes this lens system a potential double Einstein ring system. Using the high signal-to-noise ratio rest-frame spectra covered by the H + K band, we detected H{beta}, [O III], H{alpha}, [N II], and [S II] emission lines. Detailed physical properties of this high-z galaxy were derived. The extinction toward the ionized H II regions (E{sub g} (B - V)) was computed from the flux ratio of H{alpha} and H{beta} and appears to be much higher than that toward the stellar continuum (E{sub s} (B - V)), derived from the optical and NIR broadband photometry fitting. The metallicity was estimated using N2 and O3N2 indices. It is in the range of 1/5 - 1/3 solar abundance, which is much lower than for typical z {approx} 2 star-forming galaxies. From the flux ratio of [S II]{lambda}6717 and [S II]{lambda}6732, we found that the electron number density of the H II regions in the high-z galaxy was {approx_equal}1000 cm{sup -3}, consistent with other z {approx} 2 galaxies but much higher than that in local H II regions. The star formation rate was estimated via the H{alpha} luminosity, after correction for the lens magnification, to be about 365 {+-} 69 M{sub sun} yr{sup -1}. Combining the FWHM of H{alpha} emission lines and the half-light radius, we found that the dynamical mass of the lensed galaxy is (5.8 {+-} 0.9) x 10{sup 10} M{sub sun}. The gas mass is (5.1 {+-} 1.1) x 10{sup 10} M{sub sun} from the H{alpha} flux surface density

  18. Hitomi observations of the Perseus Cluster / Constant metallicity in the outskirts of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Werner, Norbert; Simionescu, Aurora; Urban, Ondrej; Allen, Steven

    2016-07-01

    X-ray observations with the Suzaku satellite reveal a remarkably homogeneous distribution of iron out to the virial radii of nearby galaxy clusters. Observations of the Virgo Cluster, that also allow us to measure the abundances of Si, S, and Mg out to the outskirts, show that the chemical composition of the intra-cluster medium is constant on large scales. These observations require that most of the metal enrichment and mixing of the intergalactic medium occurred before clusters formed, probably more than ten billion years ago, during the period of maximal star formation and black hole activity. We estimate the ratio between the number of SN Ia and the total number of supernovae enriching the intergalactic medium to be between 15-20%, generally consistent with the metal abundance patterns in our own Galaxy.

  19. Herschel+Hubble Observations of a Multiply-Lensed Sub-millimeter Galaxy at z~3

    NASA Astrophysics Data System (ADS)

    Nayyeri, Hooshang; Cooray, Asantha R.; Calanog, Jae Alyson B.; Riechers, Dominik A.; Frayer, David T.; Herschel HERMES, H-ATLAS

    2016-01-01

    We present the results of our deep Keck/NIRC2 and Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) observations of an extremely star forming lensed dusty Sub-Millimeter Galaxy (SMG) identified from the Herschel Astrohysical Terahertz Large Area Survey (H-ATLAS). The object under study forms a complex lensing system that consists of four foreground aligned galaxies at z ~ 1 (measured from Keck/DEIMOS observations) with multiple lensing features that consist of giant arcs and counter images. Molecular line observations of the background source with Green Bank Telescope (GBT) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) put it at a redshift of 2.685. Multi-band data from Keck, HST and Herschel yields a Star Formation Rate in excess of 1000 Solar masses per year putting this system among the most intensely star forming systems at z>2. The measured SFR puts this system well above the main sequence of star forming galaxies at z ~ 3. The measured gas fraction and molecular gas surface density measurements from long wavelength observations are consistent with theoretical models and observational trends of gas rich SMGs at high redshifts.

  20. The Many Faces of Galaxy Clusters: Mock Observations of Cluster Populations in Multiple Wavelengths

    NASA Astrophysics Data System (ADS)

    Nord, Brian; Evrard, A. E.; Rasia, E.; Stanek, R.

    2008-05-01

    Clusters of Galaxies trace the cosmic mass density field and thus have have potential as sensitive probes of the universe's energy content, including Dark Energy. To form a complete and unbiased perspective of these buoys, observations must occur at several wavelengths, including the X-ray, optical, and radio bands. Within the next decade, projects like the Dark Energy Survey will detect 50,000 clusters through optical observations of their galaxies. In an overlapping region of the sky, the South Pole Telescope will provide measurements of arcminute CMB anomalies, revealing the hot gas of clusters (via the Sunyaev Zeldovich effect). Independent observations of clusters--from the light of galaxies and from the scattering effect of hot gas--will allow us to address selection effects and completeness in cluster samples, as well as the definition and categorization of clusters. These efforts promise a holistic view of galaxy cluster populations; however, to properly "weigh the universe," we must precisely match observable features with masses, which are provided by the underlying dark matter halo. N-body cosmological simulations of dark matter and realistic baryonic components (e.g., hydrodynamics, AGN, star formation, etc.) offer rich, state-of-the-art venues for mock observations of cluster populations. We use re-simulations of the Millennium Run that include gas physics and pre-heating to create lightcones and then mock surveys, incorporating selection effects and survey limitations. With these mock skies, we may help to calibrate upcoming surveys (like DES and SPT), as well as to draw robust links between observable cluster properties and the underlying mass. Here, we present the recent work in construction and analysis of these mock, multi-wavelength cluster surveys.

  1. Molecular Carbon in the Galaxy: Laboratory and Observational Studies

    NASA Technical Reports Server (NTRS)

    Saykally, Richard James

    2003-01-01

    In a collaboration with the Mats Larsson group from Stockholm, we carried out a new measurement of the rate of dissociative recombination of H(sup *, sub j), using a new pulsed supersonic beam source of rotationally cold H(sup *, sub j). This source was first designed and characterized in our lab by IR cavity ringdown spectroscopy, determining a rotationaYtranslationa1 temperature of 20-60K, depending on conditions. This new source was then taken to Stockholm for the recombination rate studies at the CRYRING storage ring. The recombination rate constant measured against temperature yields values consistent with the most recent calculations, whereas previous experimental measurements varied over a range of 10(exp 4) and were poor agreement with theory. This is a crucial achievement for understanding the ion chemistry of diffuse clouds. Moreover, this result in combination with recent observations implies a greatly enhanced (factor of 40) cosmic ray ionization rate in a diffuse cloud (zeta Persei) relative to previous studies. The implications of this are discussed in our recent Nature paper. An enhanced cosmic-ray flux towards zeta Persei inferred from a laboratory study of the H(sup *, sub j)-e(sup -) recombination rate.

  2. Surface Brightness Profiles and Energetics of Intracluster Gas in Cool Galaxy Clusters and ROSAT Observations of Bright, Early-Type Galaxies

    NASA Technical Reports Server (NTRS)

    White, Raymond E., III

    1994-01-01

    Preliminary results on the elliptical galaxy NGC 1407 were published in the proceedings of the first ROSAT symposium. NGC 1407 is embedded in diffuse X-ray-emitting gas which is extensive enough that it is likely to be related to the surrounding group of galaxies, rather than just NGC 1407. Spectral data for NGC 1407 (AO2) and IC 1459 (AO3) are also included in a complete sample of elliptical galaxies I compiled in collaboration with David Davis. This allowed us to construct the first complete X-ray sample of optically-selected elliptical galaxies. The complete sample allows us to apply Malmquist bias corrections to the observed correlation between X-ray and optical luminosities. I continue to work on the implications of this first complete X-ray sample of elliptical galaxies. Paul Eskridge Dave Davis and I also analyzed three long ROSAT PSPC observations of the small (but not dwarf) elliptical galaxy M32. We found the X-ray spectra and variability to be consistent with either a Low Mass X-Ray Binary (LMXRB) or a putative 'micro"-AGN.

  3. Log-normal Star Formation Histories in Simulated and Observed Galaxies

    NASA Astrophysics Data System (ADS)

    Diemer, Benedikt; Sparre, Martin; Abramson, Louis E.; Torrey, Paul

    2017-04-01

    Gladders et al. have recently suggested that the star formation histories (SFHs) of individual galaxies are characterized by a log-normal function in time, implying a slow decline rather than rapid quenching. We test their conjecture on theoretical SFHs from the cosmological simulation Illustris and on observationally inferred SFHs. While the log-normal form necessarily ignores short-lived features such as starbursts, it fits the overall shape of the majority of SFHs very well. In particular, 85% of the cumulative SFHs are fitted to within a maximum error of 5% of the total stellar mass formed, and 99% to within 10%. The log-normal performs systematically better than the commonly used delayed-τ model, and is superseded only by functions with more than three free parameters. Poor fits are mostly found in galaxies that were rapidly quenched after becoming satellites. We explore the log-normal parameter space of normalization, peak time, and full width at half maximum, and find that the simulated and observed samples occupy similar regions, though Illustris predicts wider, later-forming SFHs on average. The ensemble of log-normal fits correctly reproduces complex metrics such as the evolution of Illustris galaxies across the star formation main sequence, but overpredicts their quenching timescales. SFHs in Illustris are a diverse population not determined by any one physical property of galaxies, but follow a tight relation, where {width} \\propto {({peak}{time})}3/2. We show that such a relation can be explained qualitatively (though not quantitatively) by a close connection between the growth of dark matter halos and their galaxies.

  4. Sub-millimeter Telescope CO (2-1) Observations of Nearby Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Jiang, Xue-Jian; Wang, Zhong; Gu, Qiusheng; Wang, Junzhi; Zhang, Zhi-Yu

    2015-01-01

    We present CO J = 2-1 observations toward 32 nearby gas-rich star-forming galaxies selected from the ALFALFA and Wide-field Infrared Survey Explorer (WISE) catalogs, using the Sub-millimeter Telescope (SMT). Our sample is selected to be dominated by intermediate-M * galaxies. The scaling relations between molecular gas, atomic gas, and galactic properties (stellar mass, NUV - r, and WISE color W3 - W2) are examined and discussed. Our results show the following. (1) In the galaxies with stellar mass M * <=1010 M ⊙, the H I fraction (f H I ≡ M H I /M *) is significantly higher than that of more massive galaxies, while the H2 gas fraction (f_H_2 ≡ M_H_2/M *) remains nearly unchanged. (2) Compared to f_H_2, f H I correlates better with both M * and NUV - r. (3) A new parameter, WISE color W3 - W2 (12-4.6 μm), is introduced, which is similar to NUV - r in tracing star formation activity, and we find that W3 - W2 has a tighter anti-correlation with log f_H_2 than the anti-correlation of (NUV - r)-f H I , (NUV - r)-f_H_2, and (W3 - W2)-f H I . This indicates that W3 - W2 can trace the H2 fraction in galaxies. For the gas ratio M_H_2/M H I , only in the intermediate-M * galaxies it appears to depend on M * and NUV - r. We find a tight correlation between the molecular gas mass M_H_2 and 12 μm (W3) luminosities (L 12 μm), and the slope is close to unity (1.03 ± 0.06) for the SMT sample. This correlation may reflect that the cold gas and dust are well mixed on a global galactic scale. Using the all-sky 12 μm (W3) data available in WISE, this correlation can be used to estimate CO flux for molecular gas observations and can even predict H2 mass for star-forming galaxies.

  5. OBSERVATIONS OF STARBURST GALAXIES WITH FAR-ULTRAVIOLET SPECTROGRAPHIC EXPLORER: GALACTIC FEEDBACK IN THE LOCAL UNIVERSE

    SciTech Connect

    Grimes, J. P.; Heckman, T.; Meurer, G.; Strickland, D.; Aloisi, A.; Leitherer, C.; Sembach, K.; Calzetti, D.; Martin, C. L. E-mail: heckman@pha.jhu.edu E-mail: dks@pha.jhu.edu E-mail: leitherer@stsci.edu E-mail: cmartin@physics.ucsb.edu

    2009-03-15

    We have analyzed FUSE (905-1187 A) spectra of a sample of 16 local starburst galaxies. These galaxies cover almost three orders of magnitude in star-formation rates and over two orders of magnitude in stellar mass. Absorption features from the stars and interstellar medium are observed in all the spectra. The strongest interstellar absorption features are generally blue-shifted by {approx} 50-300 km s{sup -1}, implying the almost ubiquitous presence of starburst-driven galactic winds in this sample. The outflow velocites increase with both the star-formation rate and the star-formation rate per unit stellar mass, consistent with a galactic wind, driven by the population of massive stars. We find outflowing coronal-phase gas (T {approx}10{sup 5.5} K) detected via the O VI absorption line in nearly every galaxy. The O VI absorption-line profile is optically thin, is generally weak near the galaxy-systemic velocity, and has a higher mean outflow velocity than seen in the lower ionization lines. The relationship between the line width and column density for the O VI absorbing gas is in good agreement with expectations for radiatively cooling and outflowing gas. Such gas will be created in the interaction of the hot out-rushing wind seen in X-ray emission and cool dense ambient material. O VI emission is not generally detected in our sample, suggesting that radiative cooling by the coronal gas is not dynamically significant in draining energy from galactic winds. We find that the measured outflow velocities in the H I and H II phases of the interstellar gas in a given galaxy increase with the strength (equivalent width) of the absorption feature and not with the ionization potential of the species. The strong lines often have profiles consisting of a broad and optically-thick component centered near the galaxy-systemic velocity and weaker but highly blue-shifted absorption. This suggests that the outflowing gas with high velocity has a lower column density than the more

  6. Cosmological implications of ROSAT observations of groups and clusters of galaxies

    NASA Technical Reports Server (NTRS)

    David, Laurence P.; Jones, Christine; Forman, William

    1995-01-01

    We have combined ROSAT Position Sensitive Proportional Counter (PSPC) and optical observations of a sample of groups and clusters of galaxies to determine the fundamental parameters of these systems (e.g., the dark matter distribution, gas mass fraction, baryon mass fraction, mass-to-light ratio, and the ratio of total-to-luminous mass). Imaging X-ray spectroscopy of groups and clusters show that the gas is essentially isothermal beyond the central region, indicating that the total mass density (mostly dark matter) scales as rho(sub dark) varies as 1/r squared. The density profile of the hot X-ray emitting gas is fairly flat in groups with rho(sub gas) varies as 1/r and becomes progressively steeper in hotter richer systems, with rho(sub gas) varies as 1/r squared in the richest clusters. These results show, that in general, the hot X-ray-emitting gas is the most extended mass component in groups and clusters, the galaxies are the most centrally concentrated component, and the dark matter is intermediate between the two. The flatter density rofile of the hot gas compared to the dark matter produces a gas mass fraction that increases with radius within each object. There is also a clear trend of increasing gas mass fraction (from 2% to 30%) between elliptical galaxies and rich clusters due to the greater detectable extent of the X-ray emission in richer systems. For the few systems in which the X-ray emission can be traced to the virial radius (where the overdensity delta is approximately equal 200), the gas mass fraction (essentially the baryon mass fraction) approaches a roughly constant value of 30%, suggesting that this is the true primordial value. Based on standard big bang nucleosynthesis, the large baryon mass fraction implies that Omega = 0.1 - 0.2. The antibiased gas distribution suggests that feedback from galaxy formation and hydrodynamics play important roles in the formation of structure on the scale of galaxies to rich clusters. All the groups and

  7. CO and continuum observations toward a strongly-lensed Submillimeter galaxy behind the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Takekoshi, Tatsuya; Kohno, Kotaro; Tamura, Yoichi; Minamidani, Tetsuhiro

    2013-10-01

    Continuum observations at 1.1 mm by AzTEC/ASTE toward the Small Magellanic Cloud provide an extremely bright submillimeter galaxy MMJ0107. MMJ0107 is very unique sample to investigate the radio-loud AGN activity in the era of extreme star formation activity. The Herschel [CII] observation reveals that MMJ0107 is likely located at the redshift of 2.766, but reliable determination is needed. In addition, to reveal the star formation and radio-loud AGN activity, we propose CO (J=1-0) observation and radio continuum observations by ATCA.

  8. A Line-of-Sight Galaxy Cluster Collision: Simulated X-Ray Observations

    NASA Astrophysics Data System (ADS)

    Zu Hone, J. A.; Ricker, P. M.; Lamb, D. Q.; Karen Yang, H.-Y.

    2009-07-01

    Several lines of evidence have suggested that the galaxy cluster Cl 0024+17, an apparently relaxed system, is actually a collision of two clusters, the interaction occurring along our line of sight. In this paper, we present a high-resolution N-body/hydrodynamics simulation of such a collision. We have created mock X-ray observations of our simulated system using MARX, a program that simulates the on-orbit performance of the Chandra X-ray Observatory. We analyze these simulated data to generate radial profiles of the surface brightness and temperature. At later times, t = 2.0-3.0 Gyr after the collision, the simulated surface brightness profiles are better fit by a superposition of two β-model profiles than a single profile, in agreement with the observations of Cl 0024+17. In general, due to projection effects, much of the post-collision density and temperature structure of the clusters is not seen in the observations. In particular, the observed temperatures from spectral fitting are much lower than the temperature of the hottest gas. We determine from our fitted profiles that if the system is modeled as a single cluster, the hydrostatic mass estimate is a factor ~2-3 less than the actual mass, but if the system is modeled as two galaxy clusters in superposition, a hydrostatic mass estimation can be made which is accurate to within ~10%. We examine some implications of these results for galaxy cluster X-ray surveys.

  9. A Galaxy Cluster Collision Viewed Along the Line of Sight: Simulated X-ray Observations

    NASA Astrophysics Data System (ADS)

    ZuHone, John; Ricker, P.; Lamb, D.; Yang, H.

    2008-03-01

    Several lines of evidence have suggested that the the galaxy cluster Cl0024+17, an apparently relaxed system, is actually a collision of two clusters, the interaction occurring along our line of sight. In this paper we present a N-body/hydrodynamics simulation of such a collision between two galaxy clusters. We have created mock X-ray observations of our simulated system using MARX, a program that simulates the on-orbit performance of the Chandra X-ray Observatory. We analyze this simulated data to generate profiles of the surface brightness and temperature profiles. The surface brightness profiles are better fit by a superposition of two β-model profiles rather than a single profile, in agreement with the observations of Cl 0024+17. However, due to projection effects, much of the density and temperature structure of the clusters post-collision is not seen in the observations. In particular, the observed temperatures from spectral fitting are lower than the temperature of the highest-temperature gas in the clusters. We determine from our fitted profiles that if the system is modeled as a single cluster, then the hydrostatic mass estimate is a factor 2-3 less than the actual mass, but if the system is modeled as two galaxy clusters in superposition, a hydrostatic mass estimation can be made which is accurate to within 10-20%.

  10. Further observations of the head-tail radio galaxy PKS 2247 + 11

    NASA Astrophysics Data System (ADS)

    Robertson, J. G.

    1981-01-01

    Observations of the head-tail radio galaxy PKS 2247+11, which is located in a poor Zwicky cluster, are presented. Maps of polarized emission at 5.0, 1.4, and 0.61 GHz are given, as well as further observations of total intensity. Rotation measures and projected magnetic field directions are derived. Thermal plasma densities are computed from the observed depolarization ratios. The radio-optical knot (Simkin and Ekers, 1979) is significantly polarized; the physical conditions inside this component are similar to those in the region of the tail near to the galaxy, consistent with the view that the knot is a component ejected almost in the direction of motion of the galaxy. The direction of the projected magnetic field in the near tail is perpendicular to the axis of the tail, in agreement with recent observations of jet sources, but in disagreement with the magneto- spheric model of tail sources. In the more distant, diffuse parts of the tail the magnetic field structure is more complex. The density and temperature of the intracluster medium are estimated: n ˜ 10-3 and T ˜ 2 10-7 K, with considerable uncertainty.

  11. ROSAT/XRT-PSPC observations and the ionizing continuum of Seyfert 1 galaxy MKN 478

    NASA Astrophysics Data System (ADS)

    Gondhalekar, P. M.; Kellett, B. J.; Pounds, K. A.; Matthews, L.; Quenby, J. J.

    1994-06-01

    The ROSAT/XRT-PSPC observations of the Seyfert 1 galaxy Mkn478 are presented. Together with the optical and ultraviolet spectra of this galaxy, obtained within eight months of the x-ray observations, these new data are used to determine the continuum energy distribution (CED) of Mkn478, from 1 micrometer to about 2.0 keV with a small break between 11.3 eV and 0.1 keV. The ultraviolet/soft x-ray CED is similar to the spectrum of a thin accretion disc for both a rotating and a non-rotating black hole, although both models underestimate the flux at energies higher than 0.4 keV.

  12. VLBI observations of the nucleus of the radio galaxy Cygnus A

    NASA Technical Reports Server (NTRS)

    Kellermann, K. I.; Downes, A. J. B.; Pauling-Toth, I. I. K.; Preuss, E.; Witzel, A.; Shaffer, D. B.

    1981-01-01

    The central component of the radio galaxy Cygnus A has been observed in several (very long baseline interferometry) experiments between 1975 and 1979, and the results have been combined to derive a model for the brightness distribution. Some 65% of the nuclear emission appears to come from a compact core. The remaining flux density comes from a more extended region (or regions) up to 4 or 5 mas away lying along a position angle near 100 deg, which is close to that of the extended lobes. Evidence that compact central components reflect the collimation and transport of energy to the outer lobes of radio galaxies is discussed, and several interpretations of the observed asymmetries are considered.

  13. XMM-Newton Observations of the Cluster of Galaxies Sersic 159-03

    NASA Technical Reports Server (NTRS)

    Kaastra, J. S.; Ferrigno, C.; Tamura, T.; Paerels, F. B. S.; Peterson, J. R.; Mittaz, J. P. D.

    2000-01-01

    The cluster of galaxies Sersic 159-03 was observed with the XMM-Newton X-ray observatory as part of the Guaranteed Time program. X-ray spectra taken with the EPIC and RGS instruments show no evidence for the strong cooling flow derived from previous X-ray observations. There is a significant lack of cool gas below 1.5 keV as compared to standard isobaric cooling flow models. While the oxygen is distributed more or less uniformly over the cluster, iron shows a strong concentration in the center of the cluster, slightly offset from the brightness center but within the central cD galaxy. This points to enhanced type Ia supernova activity in the center of the cluster. There is also an elongated iron-rich structure ex- tending to the east of the cluster, showing the inhomogeneity of the iron distribution. Finally, the temperature drops rapidly beyond 4' from the cluster center.

  14. EXAMINING THE RADIO-LOUD/RADIO-QUIET DICHOTOMY WITH NEW CHANDRA AND VLA OBSERVATIONS OF 13 UGC GALAXIES

    SciTech Connect

    Kharb, P.; Axon, D. J.; Robinson, A.; Capetti, A.; Balmaverde, B.; Chiaberge, M.; Macchetto, D.; Grandi, P.; Giovannini, G.; Montez, R.

    2012-04-15

    We present the results from new {approx}15 ks Chandra-ACIS and 4.9 GHz Very Large Array (VLA) observations of 13 galaxies hosting low-luminosity active galactic nuclei (AGNs). This completes the multiwavelength study of a sample of 51 nearby early-type galaxies described in Capetti and Balmaverde and Balmaverde and Capetti. The aim of the three previous papers was to explore the connection between the host galaxies and AGN activity in a radio-selected sample. We detect nuclear X-ray emission in eight sources and radio emission in all but one (viz., UGC 6985). The new VLA observations improve the spatial resolution by a factor of 10: the presence of nuclear radio sources in 12 of the 13 galaxies confirms their AGN nature. As previously indicated, the behavior of the X-ray and radio emission in these sources depends strongly on the form of their optical surface brightness profiles derived from Hubble Space Telescope imaging, i.e., on their classification as 'core', 'power-law', or 'intermediate' galaxies. With more than twice the number of 'power-law' and 'intermediate' galaxies compared to previous work, we confirm with a much higher statistical significance that these galaxies lie well above the radio-X-ray correlation established in Fanaroff-Riley type I radio galaxies and the low-luminosity 'core' galaxies. This result highlights the fact that the 'radio-loud/radio-quiet' dichotomy is a function of the host galaxy's optical surface brightness profile. We present radio-optical-X-ray spectral indices for all 51 sample galaxies. Survival statistics point to significant differences in the radio-to-optical and radio-to-X-ray spectral indices between the 'core' and 'power-law galaxies (Gehan's Generalized Wilcoxon test probability p for the two classes being statistically similar is <10{sup -5}), but not in the optical-to-X-ray spectral indices (p = 0.25). Therefore, the primary difference between the 'core' and 'power-law' galaxies is in their ability to launch

  15. The star formation-AGN interplay in merging galaxies: insights from hydrodynamical simulations and observations.

    NASA Astrophysics Data System (ADS)

    Martinez Galarza, Juan R.; Smith, Howard Alan; Weiner, Aaron; Hayward, Christopher C.; Lanz, Lauranne; Zezas, Andreas; Rosenthal, Lee; Ashby, Matthew

    2016-01-01

    Thermal emission from an Active Galactic Nucleus (AGN) can provide a significant contribution to the bolometric luminosity of galaxies, and its effect at infrared wavelengths can mimic the process of star-formation, jeopardizing star formation rate (SFR) diagnostics. It is therefore important to model the AGN emission and to quantify its effect on the estimated SFRs when SED fitting tools are applied. We tackle this problem by studying the dust radiative transfer calculations of hydrodynamically simulated binary galaxy mergers covering a broad range of parameters, including stellar mas ratios, gas contents, AGN luminosity and viewing angles. We apply the energy balance SED fitting codes CHIBURST and CIGALE to the mock SEDs of our simulated merger, and then compare with the results of applying the same codes to the SEDs of observed merging galaxies in the Local Universe. At different stages of the interaction, we compare their derived SFRs and AGN fractions with those predicted by the hydrodynamical simulations, for a broad range of the interaction parameters, but focus on the stages near coalescence, when the AGN contribution exceed 10% of the total luminosity. We show that the contribution to IR luminosity is greatest during and immediately after coalescence, when the two supermassive black holes of the interacting pair merge and undergo and enhanced period of accretion. Under certain conditions, CIGALE succeeds at recovering the SFRs and AGN fractions with higher accuracy than other available codes, such as MAGPHYS, even during these extreme stages. Our results show that using the IR luminosity as a simple surrogate for star formation can significantly overestimate the true SFR by underestimating the contribution from the AGN. Finally, we study the effect of using different parametric star formation histories (SFHs) when fitting the SEDs of galaxies, and show that a delayed SFH is usually a reasonable choice for merging galaxies.

  16. GALEX Ultraviolet Observations of the Interacting Galaxy NGC 4438 in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Boissier, S.; Cortese, L.; Gil de Paz, A.; Buat, V.; Iglesias-Paramo, J.; Madore, B. F.; Barlow, T.; Bianchi, L.; Byun, Y.-I.; Donas, J.; Forster, K.; Friedman, P. G.; Heckman, T. M.; Jelinsky, P.; Lee, Y.-W.; Malina, R.; Martin, D. C.; Milliard, B.; Morrissey, P.; Neff, S.; Rich, R. M.; Schiminovich, D.; Seibert, M.; Siegmund, O.; Small, T.; Szalay, A. S.; Welsh, B.; Wyder, T. K.

    2005-04-01

    We present GALEX near-ultraviolet (2310 Å) and far-ultraviolet (1530 Å) images of the interacting galaxy NGC 4438 (Arp 120) in the center of the Virgo Cluster. These images show an extended (20 kpc) tidal tail at the northwest edge of the galaxy that was previously undetected at other wavelengths; this tail is 15-25 kpc from NGC 4438's nucleus. Except for in the nucleus, the UV morphology of NGC 4438 is totally different from the Hα + [N II] morphology, which is more similar to the X-ray emission, confirming its gas cooling origin. We study the star formation history of NGC 4438 by combining spectrophotometric data in the UV-visible-near-IR wavelength range with population synthesis and galaxy evolution models. The data are consistent with a recent (~10 Myr), instantaneous burst of star formation in the newly discovered UV northwestern tail that is significantly younger than the age of the tidal interaction with NGC 4435, dated by dynamical models at ~100 Myr ago. Recent star formation events are also present at the edge of the northern arm and in the southern tail, while totally lacking in the other regions, which are dominated by the old stellar population that was perturbed during the dynamical interaction with NGC 4435. The contribution of this recent starburst to the total galaxy stellar mass is lower than 0.1%, an extremely low value for such a violent interaction. High-velocity, off-center tidal encounters such as that observed in Arp 120 are thus not sufficient to significantly increase the star formation activity of cluster galaxies.

  17. VLBI observations of a complete sample of radio galaxies. 4: The radio galaxies NGC 2484, 3C 109, and 3C 382

    NASA Technical Reports Server (NTRS)

    Giovannini, G.; Feretti, L.; Venturi, T.; Lara, L.; Marcaide, J.; Rioja, M.; Spangler, S. R.; Wehrle, A. E.

    1994-01-01

    We present here new Very Long Base Interferometry (VLBI) observations of one Fanaroff and Riley (F-R) I radio galaxy (NGC 2484) and two broad-line F-R II radio galaxies (3C 109 and 3C 382). For 3C 109 new Very Large Array (VLA) maps are also shown. These sources belong to a complete sample of radio galaxies under study for a better knowledge of their structures at parsec resolution. The parsec structure of these three objects is very similar: asymmetric emission, which we interpret as the core plus a one-side jet. The parsec-scale jet is always on the same side of the main kiloparsec-scale jet. The limit on the jet to counterjet brightness ratio, the ratio of the core radio power to the total radio power and the synchrotron-self Compton model allow us to derive some constraints on the jet velocity and orientation with respect to the line of sight. From these data and from those published on two other sources of our sample, we suggest that parsec-scale jets are relativistic in both F-R I and F-R II radio galaxies and that parsec scale properties in F-R I and F-R II radio galaxies are very similar despite the large difference between these two classes of radio galaxies on the kiloparsec scale.

  18. VLBI observations of a complete sample of radio galaxies. 4: The radio galaxies NGC 2484, 3C 109, and 3C 382

    NASA Technical Reports Server (NTRS)

    Giovannini, G.; Feretti, L.; Venturi, T.; Lara, L.; Marcaide, J.; Rioja, M.; Spangler, S. R.; Wehrle, A. E.

    1994-01-01

    We present here new Very Long Base Interferometry (VLBI) observations of one Fanaroff and Riley (F-R) I radio galaxy (NGC 2484) and two broad-line F-R II radio galaxies (3C 109 and 3C 382). For 3C 109 new Very Large Array (VLA) maps are also shown. These sources belong to a complete sample of radio galaxies under study for a better knowledge of their structures at parsec resolution. The parsec structure of these three objects is very similar: asymmetric emission, which we interpret as the core plus a one-side jet. The parsec-scale jet is always on the same side of the main kiloparsec-scale jet. The limit on the jet to counterjet brightness ratio, the ratio of the core radio power to the total radio power and the synchrotron-self Compton model allow us to derive some constraints on the jet velocity and orientation with respect to the line of sight. From these data and from those published on two other sources of our sample, we suggest that parsec-scale jets are relativistic in both F-R I and F-R II radio galaxies and that parsec scale properties in F-R I and F-R II radio galaxies are very similar despite the large difference between these two classes of radio galaxies on the kiloparsec scale.

  19. Observations of Paschen alpha in a Complete Sample of Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Hill, Gary J.; Goodrich, Robert W.; Depoy, D. L.

    1996-05-01

    We present infrared spectrophotometry of the Paα (n = 4-3) emission line of hydrogen, together with optical spectrophotometry of Hα and Hβ, of a flux-limited sample of 11 radio sources. The sample consists of all FR II 3CR radio sources with 0.1 <= z <= 0.2 and 5^h^ < R.A. < 16^h^ which contains eight narrow-line radio galaxies (3CR 135, 184.1, 219, 223, 236, 319, 321, and 327), two broad-line radio galaxies (3CR 234 and 3CR 303), and one quasar (3CR 273). The observations were aimed at the detection of obscured broad lines, hidden from our view by dust absorption, as a means of testing theories of the unification of radio galaxies and quasars. All the objects except 3CR 236 and 3CR 273 show significant reddening of the narrow and broad lines, typically of order A_V_ ~ 1.5 for narrow lines and ~3 for broad lines. We detect highly obscured broad-line regions in 3CR 184.1, 219, and 223, which appear to be narrow-line objects in the optical, so these should be reclassified as broad-line radio galaxies. In all cases except 3CR 273 and 3CR 303, the broad lines are reddened more than the narrow lines, locating much of the dust responsible for absorbing the broad-line emission between the broad- and narrow-line regions. The dereddened line luminosities range up to those of low-luminosity quasars. The results are broadly consistent with models which seek to unify radio galaxies and quasars through orientation, where an axisymmetric equatorial obscuring region hides the quasar nucleus from view unless the radio axis is pointing close to our line of sight. These data provide the first opportunity to model the distribution of broad-line region extinctions in a complete sample, rather than model just the fraction of quasars and radio galaxies. We develop a simple unification model that matches the observed distribution of extinctions, explains our observations, and makes predictions about the fraction of obscured quasars that will be present in samples of higher radio

  20. A systematic observational study of radio properties of H2O megamaser Seyfert-2 galaxies

    NASA Astrophysics Data System (ADS)

    Liu, Z. W.; Zhang, J. S.; Henkel, C.; Liu, J.; Müller, P.; Wang, J. Z.; Guo, Q.; Wang, J.; Li, J.

    2017-04-01

    A systematic study is performed on radio properties of H2O megamaser host Seyfert 2 galaxies, through multiband radio continuum observations (at 11, 6.0, 3.6, 2.0 and 1.3 cm) with the Effelsberg 100-m radio telescope within a total time duration of 4 d. For comparison, a control Seyfert 2 galaxy sample without detected maser emission was also observed. Spectral indices were determined for those sources for which measurements exist at two adjacent bands assuming a power-law dependence Sν ∝ ν-α, where S is the flux density and ν is the frequency. Comparisons of the radio continuum properties between megamaser and non-masing Seyfert 2s show no difference in spectral indices. However, a difference in radio luminosity is statistically significant, i.e. the maser galaxies tend to have higher radio luminosities by a factor of 2-3 than the non-masing ones, commonly reaching values above a critical threshold of 1029 erg s-1 Hz-1. This result confirms an earlier conclusion by Zhang et al., but is based on superior data with respect to the time interval within which the data were obtained, with respect to the observational facility (only one telescope used), and the number of frequency bands.

  1. The properties, origin and evolution of stellar clusters in galaxy simulations and observations

    NASA Astrophysics Data System (ADS)

    Dobbs, C. L.; Adamo, A.; Few, C. G.; Calzetti, D.; Dale, D. A.; Elmegreen, B. G.; Evans, A. S.; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Johnson, K. E.; Kim, H.; Lee, J. C.; Messa, M.; Ryon, J. E.; Smith, L. J.; Thilker, D.; Ubeda, L.; Whitmore, B.

    2017-01-01

    We investigate the properties and evolution of star particles in two simulations of isolated spiral galaxies, and two galaxies from cosmological simulations. Unlike previous numerical work, where typically each star particle represents one `cluster', for the isolated galaxies we are able to model features we term `clusters' with groups of particles. We compute the spatial distribution of stars with different ages, and cluster mass distributions, comparing our findings with observations including the recent LEGUS survey. We find that spiral structure tends to be present in older (100s Myr) stars and clusters in the simulations compared to the observations. This likely reflects differences in the numbers of stars or clusters, the strength of spiral arms, and whether the clusters are allowed to evolve. Where we model clusters with multiple particles, we are able to study their evolution. The evolution of simulated clusters tends to follow that of their natal gas clouds. Massive, dense, long-lived clouds host massive clusters, whilst short-lived clouds host smaller clusters which readily disperse. Most clusters appear to disperse fairly quickly, in basic agreement with observational findings. We note that embedded clusters may be less inclined to disperse in simulations in a galactic environment with continuous accretion of gas on to the clouds than isolated clouds and correspondingly, massive young clusters which are no longer associated with gas tend not to occur in the simulations. Caveats of our models include that the cluster densities are lower than realistic clusters, and the simplistic implementation of stellar feedback.

  2. HALOGAS: H I OBSERVATIONS AND MODELING OF THE NEARBY EDGE-ON SPIRAL GALAXY NGC 4244

    SciTech Connect

    Zschaechner, Laura K.; Rand, Richard J.; Heald, George H.; Gentile, Gianfranco; Kamphuis, Peter E-mail: rjr@phys.unm.edu E-mail: Gianfranco.Gentile@ugent.be

    2011-10-10

    We present 21 cm observations and models of the H I kinematics and distribution of NGC 4244, a nearby edge-on Scd galaxy observed as part of the Westerbork HALOGAS (Hydrogen Accretion in LOcal GAlaxieS) survey. Our models give insight into the H I kinematics and distribution with an emphasis on the potential existence of extraplanar gas as well as a negative gradient in rotational velocity with height above the plane of the disk (a lag). Our models yield strong evidence against a significantly extended halo and instead favor a warp component along the line of sight as an explanation for most of the observed thickening of the disk. Based on these models, we detect a lag of -9{sup +3}{sub -2} km s{sup -1} kpc{sup -1} in the approaching half and -9 {+-} 2 km s{sup -1} kpc{sup -1} in the receding half. This lag decreases in magnitude to -5 {+-} 2 km s{sup -1} kpc{sup -1} and -4 {+-} 2 km s{sup -1} kpc{sup -1} near a radius of 10 kpc in the approaching and receding halves, respectively. Additionally, we detect several distinct morphological and kinematic features including a shell that is probably driven by star formation within the disk.

  3. Lyα blobs as an observational signature of cold accretion streams into galaxies

    NASA Astrophysics Data System (ADS)

    Dijkstra, Mark; Loeb, Abraham

    2009-12-01

    Recent hydrodynamic simulations of galaxy formation reveal streams of cold (T ~ 104 K) gas flowing into the centres of dark matter haloes as massive as 1012-13.5Msolar at redshifts z ~ 1-3. In this paper, we show that if >~20 per cent of the gravitational binding energy of the gas is radiated away then the simulated cold flows are spatially extended Lyα sources with luminosities, Lyα linewidths and number densities that are comparable to those of observed Lyα blobs. Furthermore, the filamentary structure of the cold flows can explain the wide range of observed Lyα blob morphologies. Since the most massive haloes form in dense environments, the association of Lyα blobs with overdense regions arise naturally. We argue that Lyα blobs - even those which are clearly associated with starburst galaxies or quasars - provide direct observational support for the cold accretion mode of galaxies. We discuss various testable predictions of this association.

  4. X-ray Scaling Relations of SPT Selected Galaxy Clusters Observed with XMM-Newton

    NASA Astrophysics Data System (ADS)

    Bulbul, Esra; Chiu, Inon; McDonald, Michael; Bautz, Mark W.; Benson, Bradford; Bleem, Lindsey; Miller, Eric D.; Mohr, Joseph J.

    2017-01-01

    We will present results of X-ray observations of a sample of 68 South Pole Telescope selected galaxy clusters observed with XMM-Newton. Using X-ray follow-up observations with XMM-Newton, we estimate the temperature, luminosity, and mass of the intracluster medium within R500 for each cluster. From these, we constrain the Mg-Tx, Lx-Tx, and Yx-Mgas scaling relations for a sample of massive clusters at 0.1

  5. Galaxy Survey On the Fly: Prospects of Rapid Galaxy Cataloging to Aid the Electromagnetic Follow-Up of Gravitational Wave Observations

    NASA Astrophysics Data System (ADS)

    Bartos, I.; Crotts, A. P. S.; Márka, S.

    2015-03-01

    Galaxy catalogs are essential for efficient searches of the electromagnetic counterparts of extragalactic gravitational wave (GW) signals with highly uncertain localization. We show that one can efficiently catalog galaxies within a short period of time with 1-2 m class telescopes such as the Palomar Transient Factory (PTF) or MDM, in response to an observed GW signal from a compact binary coalescence. We find that a rapid galaxy survey is feasible on the relevant time scale of ≲ 1 week, with a maximum source distance of \\gt 200 Mpc and a sky area of 100 deg2. With PTF-like telescopes, even 1 day is sufficient for such a survey. This catalog can then be provided to other telescopes to aid electromagnetic follow-up observations to find kilonovae from binary coalescences, as well as other sources. We consider Hα observations, which track the star formation rate (SFR) and are therefore correlated with the rate of compact binary mergers. Hα surveys are also able to filter out galaxies that are farther away than the maximum GW source distance. Rapid galaxy surveys that follow GW triggers could achieve ˜90% completeness with respect to SFR, which is currently unavailable. This will significantly reduce the required effort and enhance the immediate availability of catalogs compared to possible future all-sky surveys.

  6. Observational study of the candidate polar-ring galaxies NGC 304 and NGC 7625

    NASA Astrophysics Data System (ADS)

    Karataeva, G. M.; Kuznetsov, A. N.

    2008-09-01

    We present the results of our photometric ( BV R) and spectroscopic CCD observations of NGC 304 and NGC 7625, candidate polar-ring galaxies, performed with the 6-m Special Astrophysical Observatory telescope. For NGC 304, such a study has been carried out for the first time. We have obtained basic integrated characteristics of the galaxies and determined their morphological types (S0 for NGC 304 and Sa for NGC 7625). The absolute magnitudes of the galaxies, M B = -20m.81 for NGC 304 and M B = -19m.34 for NGC7625, are indicative of their fairly high luminosities. The disk and bulge parameters have been determined forNGC 304 (µ0 = 20m.60, h = 3.86 kpc, µ e = 21m.59, r e = 1.26 kpc in the B band); these correspond to the parameters of S0-type objects. The rotation velocity for NGC 304 (200 km s-1) reaches its maximum at a galactocentric distance of 3.1 kpc, which yields a mass estimate for the galaxy of 2.8 × 1010 mathcal{M}_ odot . The observed photometric features at the center of NGC 304 indicate that it may have an inner ring structure, although we have failed to confirm the existence of two kinematic systems based on our spectroscopic observations. In NGC 7625, the disk makes a dominant contribution to the total brightness. The derived integrated color indices ( B-V = 0m.81 and V-R = 0m.61) agree with previous determinations of other authors. We have estimated the учештсешщт in the inner galactic regions. In the outer regions, we have detected structures with bluer colors ( B-V = 0m.60), which may be indicative of a polar ring with a minor stellar component.

  7. ASCA observation of three bright early-type galaxies: NGC 4472, NGC 4406, and NGC 4636

    NASA Technical Reports Server (NTRS)

    Awaki, Hisamitsu; Mushotzky, Richard; Tsuru, Takeshi; Fabian, Andrew C.; Fukazawa, Yasushi; Loewenstein, Michael; Makishima, Kazuo; Matsumoto, Hironori; Matsushita, Kyoko; Mihara, Tatehiro

    1994-01-01

    We report Advanced Satellite for Cosmology and Astrophysics (ASCA) 0.3-10 keV and X-ray observations of three early type galaxies, NGC 4472, NGC 4406, and NGC 4636. The extended mission in these galaxies is well described by thin thermal eimssion from hot gas. The gas temperature is 0.92 +/- 0.02 keV for NGC 4472, 0.79 +/- 0.01 keV for NGC 4406, and 0.73 +/- 0.02 keV for NGC 4636. The metal abundance for NGC 4472, NGC 4406, and NGC 4636 are, under the assumption of solar ratios, 0.63 +/- 0.15, 0.45 +/- 0.10, and 0.38 +/- 0.07, respectively. Detailed analysis has allowed determination of the abundances of oxygen, silicon, sulfur, and iron. The observed abundances are consistent with the solar ratios. For NGC 4472 and NGC 4406 we also determined the mean temperature of the gas producing the Si lines from the ratio of the Si H to He-like lines and find it to be consistent with the continuum temperature. The X-ray temperature is in good agreement with the observed optical velocity dispersion, stellar density profile, and gas density profile. Our data indicates that the supernova rate should be less than one fifth of the nominal rate in early type galaxies. We derive the mass of these systems within fixed angular scales and find that M/L greater than 40, confirming that elliptical galaxies are dark matter dominated at large radii.

  8. Simultaneous Broadband Observations of jet-dominated active galaxies with NuSTAR

    NASA Astrophysics Data System (ADS)

    Furniss, Amy

    2014-08-01

    The exceptionally energetic particle populations at work within powerful relativistic jets associated with active galaxies make these sources natural targets for the NuSTAR hard X-ray instrument. This space-based satellite can observe their emission between 3 and 70 keV with unprecedented sensitivity. This emission is likely due to the synchrotron process, and particles responsible for the hard X-ray emission are also expected to produce gamma-rays via inverse Compton process observed by instruments such as Fermi Large Area Telescope, VERITAS, MAGIC and HESS. Since the launch of NuSTAR, the instrument has led simultaneous broadband campaigns on multiple gamma-ray emitting jetted active galaxies. NuSTAR was able to observe Mrk 421 during unprecedented low and high states, as well as variability in Mrk 501 consistent with a magnetic reconnection event. Additionally, the extreme blazar 1ES 0229+200 was observed with NuSTAR, together with ground based gamma-ray instruments, providing the first complete picture of the broadband emission. These invaluable observations of BL Lac-type objects were supplemented with NuSTAR observations of the exceptionally variable flat spectrum radio quasar 3C 279, observed during the highest gamma-ray state yet observed by the Fermi LAT instrument. We will share the results from these multiwavelength campaigns, with particular emphasis on the implications for the study of the most relativistic particle populations at work within the Universe.

  9. Time-resolved visible/near-infrared spectrometric observations of the Galaxy 11 geostationary satellite

    NASA Astrophysics Data System (ADS)

    Bédard, Donald; Wade, Gregg A.

    2017-01-01

    Time-resolved spectrometric measurements of the Galaxy 11 geostationary satellite were collected on three consecutive nights in July 2014 with the 1.6-m telescope at the Observatoire du Mont-Mégantic in Québec, Canada. Approximately 300 low-resolution spectra (R ≈ 700 , where R = λ / Δλ) of the satellite were collected each night, covering a spectral range between 425 and 850 nm. The two objectives of the experiment were to conduct material-type identification from the spectra and to study how the spectral energy distribution inferred from these measurements varied as the illumination and observation geometry changed on nightly timescales. We present results that indicate the presence of a highly reflective aluminized surface corresponding to the solar concentrator arrays of the Galaxy 11 spacecraft. Although other material types could not be identified using the spectra, the results showed that the spectral energy distribution of the reflected sunlight from the Galaxy 11 spacecraft varied significantly, in a systematic manner, over each night of observation. The variations were quantified using colour indices calculated from the time-resolved spectrometric measurements.

  10. Structure and kinematics of polar ring galaxies: new observations and estimation of the dark halo shape

    NASA Astrophysics Data System (ADS)

    Moiseev, A.; Khoperskov, S.; Khoperskov, A.; Smirnova, K.; Smirnova, A.; Saburova, A.; Reshetnikov, V.

    The polar ring galaxies (PRGs) represent an interesting type of peculiar systems in which the outer matter is rotating in the plane which is roughly perpendicular to the disk of the main galaxy. Despite the long-lasting study of the PRGs, the amount of observational data detailed enough is insufficient; there still remain many open questions. Among the most interesting issues, there are: estimating the flattening of dark matter halos in these systems and verifying the assumption that the most massive polar structures were formed by accretion of the matter from intergalactic filaments. The new catalog recently compiled by our team using SDSS images increased, by several times, the number of known PRGs. The current paper gives an overview of our latest results on the study of morphological and photometric structure of the PRGs. Using the stellar and ionized gas kinematics data based on spectroscopic observations with the Russian 6-m telescope, we estimate the shape of dark matter halo in individual galaxies.

  11. Using Hydro-Simulations To Interpret Observed Kinematic Maps Of Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Simons, Raymond

    2016-09-01

    Our understanding of disk formation at z 2 is being shaped by several ongoing kinematics surveys using IFUs and slits. Primitive disks that have formed by this epoch are kinematically complex. Several processes that disrupt disks, including clumpy and smooth accretion as well as major mergers, are expected to drive these irregularities and leave signatures in the kinematic maps. While global measurements of rotation and dispersion provide a reasonable description of galaxy kinematics, the rich details of the full kinematic maps have yet to be incorporated into our analyses. In this presentation, I will present new work aimed at exploiting the full information of these data sets. We investigate mock observations (kinematic and photometric maps) for the VELA suite of ART zoom/in cosmological simulations of galaxy formation using a full dust-radiative transfer model with SUNRISE. We find that quantitative morphological indices, once applied to galaxy kinematic maps, are good discriminators of ordered, perturbed and destroyed disks. I will discuss how these indices can be applied to observational data to investigate the disk fraction at z 2.

  12. A distance to the galaxy NGC4258 from observations of Cepheid variable stars.

    PubMed

    Maoz, E; Newman, J A; Ferrarese, L; Stetson, P B; Zepf, S E; Davis, M; Freedman, W L; Madore, B F

    1999-09-23

    Cepheid variable stars pulsate in a way that is correlated with their intrinsic luminosity, making them useful as 'standard candles' for determining distances to galaxies; the potential systematic uncertainties in the resulting distances have been estimated to be only 8-10%. They have played a crucial role in establishing the extragalactic distance scale and hence the value of the Hubble constant. Here we report observations of Cepheids in the nearby galaxy NGC4258; the distance calculated from the Cepheids is 8.1 +/- 0.4 Mpc, where the uncertainty does not include possible systematic errors. There is an independently determined geometric distance to this galaxy of 7.2 +/- 0.5 Mpc, based on the observed proper motions of water masers orbiting the central black hole; the distances differ by 1.3sigma. If the maser-based distance is adopted and the Cepheid distance scale revised accordingly, the derived value of the Hubble constant would increase by 12 +/- 9%, while the expansion age of the Universe would decrease by the same amount.

  13. Reconstructing the primordial spectrum of fluctuations of the universe from the observed nonlinear clustering of galaxies

    NASA Technical Reports Server (NTRS)

    Hamilton, A. J. S.; Matthews, Alex; Kumar, P.; Lu, Edward

    1991-01-01

    It was discovered that the nonlinear evolution of the two point correlation function in N-body experiments of galaxy clustering with Omega = 1 appears to be described to good approximation by a simple general formula. The underlying form of the formula is physically motivated, but its detailed representation is obtained empirically by fitting to N-body experiments. In this paper, the formula is presented along with an inverse formula which converts a final, nonlinear correlation function into the initial linear correlation function. The inverse formula is applied to observational data from the CfA, IRAs, and APM galaxy surveys, and the initial spectrum of fluctuations of the universe, if Omega = 1.

  14. OSSE observations of the ultraluminous infrared galaxies ARP 220 and MRK 273

    NASA Technical Reports Server (NTRS)

    Dermer, C. D.; Shier, L. M.; Sturner, S. J.; McNaron-Brown, K.; Bland-Hawthorn, J.

    1997-01-01

    The results of oriented scintillation spectrometer experiment (OSSE) observations of the ultraluminous infrared galaxies Arp 220 and Mrk 273 are reported. The pointings of Arp 220 and Mrk 273 concentrated on their upper limits. The gamma ray luminosities from these sources were found to be between one and two orders of magnitude smaller than the infrared luminosities. Multiwavelength luminosity spectra are produced from the radio to the gamma ray regime, and are compared with the typical multiwavelength spectra of active galactic nuclei. The lack of measured gamma ray emission provides no evidence for the existence of buried active galactic nuclei in these ultraluminous infrared galaxies, but is consistent with an origin of the infrared luminosity from starburst activity.

  15. Synthetic HI observations of spiral structure in the outer disk in galaxies

    NASA Astrophysics Data System (ADS)

    Khoperskov, Sergey A.; Bertin, Giuseppe

    2015-12-01

    > By means of 3D hydrodynamical simulations, in a separate paper we have discussed the properties of non-axisymmetric density wave trains in the outermost regions of galaxy disks, based on the picture that self-excited global spiral modes in the bright optical stellar disk are accompanied by low-amplitude short trailing wave signals outside corotation; in the gas, such wave trains can penetrate through the outer Lindblad resonance and propagate outwards, forming prominent spiral patterns. In this paper we present the synthetic 21 cm velocity maps expected from simulated models of the outer gaseous disk, focusing on the case when the disk is dominated by a two-armed spiral pattern, but considering also other more complex situations. We discuss some aspects of the spiral pattern in the gaseous periphery of galaxy disks noted in our simulations that might be interesting to compare with specific observed cases.

  16. Optical emission in the radio lobes of radio galaxies. II - New observations of 21 radio lobes

    NASA Astrophysics Data System (ADS)

    Crane, P.; Tyson, J. A.; Saslaw, W. C.

    1983-02-01

    The authors report new identifications of optical emission associated with the radio lobes of double radio galaxies. Optical emission is present in the outer radio structure of the sources 3C 219, 3C 244.1, 3C 247, 3C 252, 3C 268.2, 3C 321, 3C 319, 3C 337, and possibly in 3C 330. The authors have not found emission to the detection limit of V ≡ 24 in the sources 3C 79, 3C 173.1, 3C 223, 3C 325, and 3C 381. Of the 21 separate sources in optical studies of extended lobes of radio galaxies reported to date, 16 radio sources observed so far show significant optical emission within one or both lobes, while in 11 of these the optical object is within 2arcsec of the radio peak.

  17. Age-dating luminous red galaxies observed with the Southern African Large Telescope

    NASA Astrophysics Data System (ADS)

    Ratsimbazafy, A. L.; Loubser, S. I.; Crawford, S. M.; Cress, C. M.; Bassett, B. A.; Nichol, R. C.; Väisänen, P.

    2017-05-01

    We measure a value for the cosmic expansion of H(z) = 89 ± 23(stat) ± 44(syst) km s-1 Mpc-1 at a redshift of z ≃ 0.47 based on the differential age technique. This technique, also known as cosmic chronometers, uses the age difference between two redshifts for a passively evolving population of galaxies to calculate the expansion rate of the Universe. Our measurement is based on the analysis of high-quality spectra of luminous red galaxies obtained with the Southern African Large Telescope in two narrow redshift ranges of z ≃ 0.40 and 0.55 as part of an initial pilot study. Ages were estimated by fitting single stellar population models to the observed spectra. This measurement presents one of the best estimates of H(z) via this method at z ˜ 0.5 to date.

  18. Simulated observations of high-redshift galaxies with the HARMONI spectrograph for the European Extremely Large Telescope

    NASA Astrophysics Data System (ADS)

    Kendrew, Sarah; Zieleniewski, Simon; Houghton, Ryan C. W.; Thatte, Niranjan; Devriendt, Julien; Tecza, Matthias; Clarke, Fraser; O'Brien, Kieran; Häußler, Boris

    2016-08-01

    We show the results of a study into the performance of the E-ELT integral field spectrograph HARMONI for observations of galaxies at 2 < z < 4. Using the instrument simulation pipeline HSIM, we performed mock observations of galaxies in this redshift range using two different methods: (i) passive galaxies modeled with simple analytical spatial profiles and star formation histories; and (ii) a single z = 3 galaxy extracted from a high-resolution cosmological simulation, with a more complex and physically representative morphology and star formation history. We describe the software tools developed to convert the simulation data into a spectral cube containing the spatial and spectral properties of the galaxy's light. From the mock observations we estimate how well the intrinsic properties of the galaxy can be recovered using commonly used analysis tools. The HSIM pipeline also allows us to study observational biases and their likely impact on the data. We discuss the implications of the project for the future science with HARMONI in the critical redshift regime for mass assembly in galaxies.

  19. Spitzer Observations of MAMBO Galaxies: Weeding Out Active Nuclei in Starbursting Protoellipticals

    NASA Astrophysics Data System (ADS)

    Ivison, R. J.; Greve, T. R.; Serjeant, S.; Bertoldi, F.; Egami, E.; Mortier, A. M. J.; Alonso-Herrero, A.; Barmby, P.; Bei, L.; Dole, H.; Engelbracht, C. W.; Fazio, G. G.; Frayer, D. T.; Gordon, K. D.; Hines, D. C.; Huang, J.-S.; Le Floc'h, E.; Misselt, K. A.; Miyazaki, S.; Morrison, J. E.; Papovich, C.; Pérez-González, P. G.; Rieke, M. J.; Rieke, G. H.; Rigby, J.; Rigopoulou, D.; Smail, I.; Wilson, G.; Willner, S. P.

    2004-09-01

    We present 3.6-24 μm Spitzer observations of an unbiased sample of nine luminous, dusty galaxies selected at 1200 μm by MAMBO on the IRAM 30 m telescope, a population akin to the well-known submillimeter or SCUBA galaxies (hereafter SMGs). Owing to the coarse resolution of submillimeter/millimeter cameras, SMGs have traditionally been difficult to identify at other wavelengths. We compare our multiwavelength catalogs to show that the overlap between 24 and 1200 μm must be close to complete at these flux levels. We find that all (4/4) of the most secure >=4 σ SMGs have >=4 σ counterparts at 1.4 GHz, while the fraction drops to 7/9 using all >=3 σ SMGs. We show that combining mid-infrared (MIR) and marginal (>=3 σ) radio detections provides plausible identifications in the remaining cases, enabling us to identify the complete sample. Accretion onto an obscured central engine is betrayed by the shape of the MIR continuum emission for several sources, confirming Spitzer's potential to weed out active galaxies. We demonstrate the power of an S24μm/S8μm versus S8μm/S4.5μm color-color plot as a diagnostic for this purpose. However, we conclude that the majority (~75%) of SMGs have rest-frame mid/far-IR spectral energy distributions commensurate with obscured starbursts. Sensitive 24 μm observations are clearly a useful route to identify and characterize reliable counterparts to high-redshift far-IR-bright galaxies, complementing what is possible via deep radio imaging.

  20. XMM-Newton Observations of the Heavily Absorbed Seyfert 1 Galaxy IC 4329A

    SciTech Connect

    Steenbrugge, K.

    2005-01-05

    We detect seven distinct absorbing systems in the high-resolution X-ray spectrum of the Seyfert 1 galaxy IC 4329A, taken with XMM-Newton. Firstly we detect absorption due to cold gas in our own Galaxy and warm gas in the Galactic halo or the Local Group. This local warm gas is only detected through O VII absorption, from which we deduce a temperature between 0.03 and 0.2 keV. In IC 4329A we detect absorption from the host galaxy as well as from a warm absorber, close to the nucleus, which has 4 components. The absorption from the host galaxy is well modeled by neutral material. The warm absorber detected in IC 4329A is photoionized and has an ionization range between log {xi} = -1.37 and log {xi} = 2.7. A broad excess is measured at the O VIII Ly{alpha} and N VII Ly{alpha} emission lines, which can be modeled by either disklines or multiple Gaussians. From the lightcurve we find that the source changed luminosity by about 20 % over the 140 ks observation, while the spectral shape, i.e. the softness ratio did not vary. In the EPIC spectra a narrow Fe K{alpha} and Fe XXVI Ly{alpha} emission line are detected. The narrowness of the Fe K{alpha} line and the fact that there is no evidence for flux variability between different observations leads us to conclude that the Fe K{alpha} line is formed at a large distance from the central black hole.

  1. The ``Sausage'' and ``Toothbrush'' clusters of galaxies and the prospects of LOFAR observations of clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Röttgering, H.; van Weeren, R.; Brüggen, M.; Croston, J.; Hoeft, M.; Ogrean, G.; Barthel, P.; Best, P.; Bonafede, A.; Brunetti, G.; Cassano, R.; Chyży, K.; Conway, J.; De Gasperin, F.; Ferrari, C.; Heald, G.; Jackson, N.; Jarvis, M.; Lehnert, M.; Macario, G.; Miley, G.; Orrú, E.; Pizzo, R.; Rafferty, D.; Stroe, A.; Tasse, C.; van der Tol, S.; White, G.; Wise, M.; LOFAR Collaboration

    2013-04-01

    LOFAR, the Low Frequency Radio Array, is a new pan-European radio telescope that is almost fully operational. One of its main drivers is to make deep images of the low frequency radio sky. To be able to do this a number of challenges need to be addressed. These include the high data rates, removal of radio frequency interference, calibration of the beams and correcting for the corrupting influence of the ionosphere. One of the key science goals is to study merger shocks, particle acceleration mechanisms and the structure of magnetic fields in nearby and distant merging clusters. Recent studies with the GMRT and WSRT radio telescopes of the ``Sausage'' and the ``Toothbrush'' clusters have given a very good demonstration of the power of radio observations to study merging clusters. Recently we discovered that both clusters contain relic and halo sources, large diffuse regions of radio emission not associated with individual galaxies. The 2 Mpc northern relic in the Sausage cluster displays highly aligned magnetic fields and and exhibits a strong spectral index gradient that is a consequence of cooling of the synchrotron emitting particles in the post-shock region. We have argued that these observations provide strong evidence that shocks in merging clusters are capable of accelerating particles. For the Toothbrush cluster we observe a puzzling linear relic that extends over 2 Mpc. The proposed scenario is that a triple-merger can lead to such a structure. With LOFAR's sensitivity it will not only be possible to trace much weaker shocks, but also to study those shocks due to merging clusters up to redshifts of at least one.

  2. Einstein observations of the Hydra A cluster and the efficiency of galaxy formation in groups and clusters

    NASA Technical Reports Server (NTRS)

    David, L. P.; Arnaud, K. A.; Forman, W.; Jones, C.

    1990-01-01

    The Einstein imaging proportional counter observations of the poor cluster of galaxies centered on the radio galaxy Hydra A are examined. From the surface brightness profile, it is found that the X-ray-emitting gas in the Hydra A cluster must be condensing out of the intracluster medium at a rate of 600 solar masses/yr. This is one of the largest mass deposition rates observed in a cluster of galaxies. The ratio of gas mass to stellar mass is compared for a variety of systems, showing that this ratio correlates with the gas temperature.

  3. Einstein observations of the Hydra A cluster and the efficiency of galaxy formation in groups and clusters

    NASA Technical Reports Server (NTRS)

    David, L. P.; Arnaud, K. A.; Forman, W.; Jones, C.

    1990-01-01

    The Einstein imaging proportional counter observations of the poor cluster of galaxies centered on the radio galaxy Hydra A are examined. From the surface brightness profile, it is found that the X-ray-emitting gas in the Hydra A cluster must be condensing out of the intracluster medium at a rate of 600 solar masses/yr. This is one of the largest mass deposition rates observed in a cluster of galaxies. The ratio of gas mass to stellar mass is compared for a variety of systems, showing that this ratio correlates with the gas temperature.

  4. Low-frequency radio observations of Seyfert galaxies: A test of the unification scheme

    NASA Astrophysics Data System (ADS)

    Singh, V.; Shastri, P.; Ishwara-Chandra, C. H.; Athreya, R.

    2013-06-01

    Aims: We present low-frequency radio imaging and spectral properties of a well-defined sample of Seyfert galaxies using GMRT 240/610 MHz dual frequency observations. Radio spectra of Seyfert galaxies over 240 MHz to 5.0 GHz are investigated using 240 MHz, 610 MHz flux densities derived from GMRT, and 1.4 GHz and 5.0 GHz flux densities mainly from published VLA data. We test the predictions of Seyfert unification scheme by comparing the radio properties of Seyfert type 1s and type 2s. Methods: We chose a sample such that the two Seyferts subtypes have matched distributions in parameters that are independent of the orientation of AGN, obscuring torus, and the host galaxy. Our sample selection criteria allowed us to assume that the two Seyfert subtypes are intrinsically similar within the framework of the unification scheme. Results: The new observations at 240/610 MHz, together with archival observations at 1.4 GHz, 5.0 GHz show that types 1s and 2s have statistically similar radio luminosity distributions at 240 MHz, 610 MHz, 1.4 GHz, and 5.0 GHz. The spectral indices at selected frequency intervals (α240 MHz610 MHz, α610 MHz1.4 GHz, and α1.4 GHz5.0 GHz), as well as index measured over 240 MHz to 5.0 GHz (αint) for the two Seyfert subtypes, have similar distributions with median spectral index (α) ~ -0.7 (Sν ∝ να), consistent with the synchrotron emission from optically thin plasma. In our snapshot 240/610 MHz GMRT observations, most of the Seyfert galaxies primarily show an unresolved central radio component, except for a few sources in which faint kpc-scale extended emission is apparent at 610 MHz. Our results on the statistical comparison of the multifrequency radio properties of our sample Seyfert galaxies agree with the predictions of the Seyfert unification scheme. Figures 2, 4 and Appendix A are available in electronic form at http://www.aanda.org

  5. [C II] 158-micrometer Observations of a Sample of Late-type Galaxies from the Virgo Cluster

    NASA Technical Reports Server (NTRS)

    Leech, K. J.; Volk, H. J.; Heinrichsen, I.; Hippelein, H.; Metcalfe, L.; Pierini, D.; Popescu, C. C.; Tuffs, R. J.; Xu, C.

    1998-01-01

    We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESAs Infrared Space Observatory (ISO) obtaining spectral around the (C II) 157.741-micrometer fine structure line.

  6. Detection of Lensing Substructure Using Alma Observations of the Dusty Galaxy SDP.81

    SciTech Connect

    Hezaveh, Yashar D.; Dalal, Neal; Marrone, Daniel P.; Mao, Yao-Yuan; Morningstar, Warren; Wen, Di; Blandford, Roger D.; Carlstrom, John E.; Fassnacht, Christopher D.; Holder, Gilbert P.; Kemball, Athol; Marshall, Philip J.; Murray, Norman; Levasseur, Laurence Perreault; Vieira, Joaquin D.; Wechsler, Risa H.

    2016-05-19

    We study the abundance of substructure in the matter density near galaxies using ALMA Science Verification observations of the strong lensing system SDP.81. We present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. Using simulated ALMA observations we explore the effects of various systematics, including antenna phase errors and source priors, and show how such errors may be measured or marginalized. We apply our formalism to ALMA observations of SDP.81. We find evidence for the presence of a M = 108.96±0.12 M subhalo near one of the images, with a significance of 6.9σ in a joint fit to data from bands 6 and 7; the effect of the subhalo is also detected in both bands individually. We also derive constraints on the abundance of dark matter (DM) subhalos down to M ~ 2 × 107 M, pushing down to the mass regime of the smallest detected satellites in the Local Group, where there are significant discrepancies between the observed population of luminous galaxies and predicted DM subhalos. We find hints of additional substructure, warranting further study using the full SDP.81 data set (including, for example, the spectroscopic imaging of the lensed carbon monoxide emission). We compare the results of this search to the predictions of ΛCDM halos, and find that given current uncertainties in the host halo properties of SDP.81, our measurements of substructure are consistent with theoretical expectations. Finally, observations of larger samples of gravitational lenses with ALMA should be able to improve the constraints on the abundance of galactic substructure.

  7. Detection of Lensing Substructure Using Alma Observations of the Dusty Galaxy SDP.81

    SciTech Connect

    Hezaveh, Yashar D.; Dalal, Neal; Marrone, Daniel P.; Mao, Yao-Yuan; Morningstar, Warren; Wen, Di; Blandford, Roger D.; Carlstrom, John E.; Fassnacht, Christopher D.; Holder, Gilbert P.; Kemball, Athol; Marshall, Philip J.; Murray, Norman; Levasseur, Laurence Perreault; Vieira, Joaquin D.; Wechsler, Risa H.

    2016-05-19

    We study the abundance of substructure in the matter density near galaxies using ALMA Science Verification observations of the strong lensing system SDP.81. We present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. Using simulated ALMA observations we explore the effects of various systematics, including antenna phase errors and source priors, and show how such errors may be measured or marginalized. We apply our formalism to ALMA observations of SDP.81. We find evidence for the presence of a M = 108.96±0.12 M subhalo near one of the images, with a significance of 6.9σ in a joint fit to data from bands 6 and 7; the effect of the subhalo is also detected in both bands individually. We also derive constraints on the abundance of dark matter (DM) subhalos down to M ~ 2 × 107 M, pushing down to the mass regime of the smallest detected satellites in the Local Group, where there are significant discrepancies between the observed population of luminous galaxies and predicted DM subhalos. We find hints of additional substructure, warranting further study using the full SDP.81 data set (including, for example, the spectroscopic imaging of the lensed carbon monoxide emission). We compare the results of this search to the predictions of ΛCDM halos, and find that given current uncertainties in the host halo properties of SDP.81, our measurements of substructure are consistent with theoretical expectations. Finally, observations of larger samples of gravitational lenses with ALMA should be able to improve the constraints on the abundance of galactic substructure.

  8. Detection of Lensing Substructure Using Alma Observations of the Dusty Galaxy SDP.81

    DOE PAGES

    Hezaveh, Yashar D.; Dalal, Neal; Marrone, Daniel P.; ...

    2016-05-19

    We study the abundance of substructure in the matter density near galaxies using ALMA Science Verification observations of the strong lensing system SDP.81. We present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. Using simulated ALMA observations we explore the effects of various systematics, including antenna phase errors and source priors, and show how such errors may be measured or marginalized. We apply our formalism to ALMA observations of SDP.81. We find evidence for the presence of a M = 108.96±0.12 M⊙ subhalo near one of the images, with a significance ofmore » 6.9σ in a joint fit to data from bands 6 and 7; the effect of the subhalo is also detected in both bands individually. We also derive constraints on the abundance of dark matter (DM) subhalos down to M ~ 2 × 107 M⊙, pushing down to the mass regime of the smallest detected satellites in the Local Group, where there are significant discrepancies between the observed population of luminous galaxies and predicted DM subhalos. We find hints of additional substructure, warranting further study using the full SDP.81 data set (including, for example, the spectroscopic imaging of the lensed carbon monoxide emission). We compare the results of this search to the predictions of ΛCDM halos, and find that given current uncertainties in the host halo properties of SDP.81, our measurements of substructure are consistent with theoretical expectations. Finally, observations of larger samples of gravitational lenses with ALMA should be able to improve the constraints on the abundance of galactic substructure.« less

  9. Analysis of LAC Observations of Clusters of Galaxies and Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Hughes, J.

    1996-01-01

    The following publications are included and serve as the final report: The X-ray Spectrum of Abell 665; Clusters of Galaxies; Ginga Observation of an Oxygen-rich Supernova Remnant; Ginga Observations of the Coma Cluster and Studies of the Spatial Distribution of Iron; A Measurement of the Hubble Constant from the X-ray Properties and the Sunyaev-Zel'dovich Effect of Abell 2218; Non-polytropic Model for the Coma Cluster; and Abundance Gradients in Cooling Flow Clusters: Ginga LAC (Large Area Counter) and Einstein SSS (Solid State Spectrometer) Spectra of A496, A1795, A2142, and A2199.

  10. Spectra, fluxes, and observability of gamma rays from dark matter annihilation in the Galaxy

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Tylka, A. J.

    1989-01-01

    Details of the physics of gamma-ray production by the annihilation of dark matter particles in the Galaxy are presented. Improved gamma-ray spectra and fluxes are calculated and compared with present observational data on cosmic gamma-ray fluxes at high Galactic latitudes. A comparison with the gamma-ray flux from cosmic-ray interactions is made. It is found that gamma-rays from dark matter annihilation are most potentially observable from patches of the sky at high Galactic latitudes in directions having an unusually low total column density of gas and from a dark matter core at the Galactic center.

  11. An Observational Guide to Identifying Pseudobulges and Classical Bulges in Disc Galaxies

    NASA Astrophysics Data System (ADS)

    Fisher, David B.; Drory, Niv

    In this review our aim is to summarize the observed properties of pseudobulges and classical bulges. We utilize an empirical approach to studying the properties of bulges in disc galaxies, and restrict our analysis to statistical properties. A clear bimodality is observed in a number of properties including morphology, structural properties, star formation, gas content & stellar population, and kinematics. We conclude by summarizing those properties that isolate pseudobulges from classical bulges. Our intention is to describe a practical, easy to use, list of criteria for identifying bulge types.

  12. Compton Observatory observations of clusters of galaxies and extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This task involved the investigation of the emission of clusters of galaxies, particularly those which contain extended radio emission, in the gamma-ray region of the spectrum. Observations were made of several clusters using the Compton Observatory EGRET instrument. For each cluster a measured flux or upper limit on the gamma-ray flux was obtained. In only one case, Abell 2199, was there a significant measured flux. This source is spatially confused with a know blazar in the field of view. The observation is consistent with all emissions being from the blazar.

  13. NGC 5548: LACK OF A BROAD Fe K{alpha} LINE AND CONSTRAINTS ON THE LOCATION OF THE HARD X-RAY SOURCE

    SciTech Connect

    Brenneman, L. W.; Elvis, M.; Krongold, Y.; Liu, Y.; Mathur, S.

    2012-01-01

    We present an analysis of the co-added and individual 0.7-40 keV spectra from seven Suzaku observations of the Sy 1.5 galaxy NGC 5548 taken over a period of eight weeks. We conclude that the source has a moderately ionized, three-zone warm absorber, a power-law continuum, and exhibits contributions from cold, distant reflection. Relativistic reflection signatures are not significantly detected in the co-added data, and we place an upper limit on the equivalent width of a relativistically broad Fe K{alpha} line at EW {<=} 26 eV at 90% confidence. Thus NGC 5548 can be labeled as a 'weak' type 1 active galactic nucleus (AGN) in terms of its observed inner disk reflection signatures, in contrast to sources with very broad, strong iron lines such as MCG-6-30-15, which are likely much fewer in number. We compare physical properties of NGC 5548 and MCG-6-30-15 that might explain this difference in their reflection properties. Though there is some evidence that NGC 5548 may harbor a truncated inner accretion disk, this evidence is inconclusive, so we also consider light bending of the hard X-ray continuum emission in order to explain the lack of relativistic reflection in our observation. If the absence of a broad Fe K{alpha} line is interpreted in the light-bending context, we conclude that the source of the hard X-ray continuum lies at radii r{sub s} {approx}> 100 r{sub g}. We note, however, that light-bending models must be expanded to include a broader range of physical parameter space in order to adequately explain the spectral and timing properties of average AGNs, rather than just those with strong, broad iron lines.

  14. Comparative Analysis of Gas Halos in High Redshift Galaxies: Observations vs Λ-CDM Simluations with Feedback

    NASA Astrophysics Data System (ADS)

    Churchill, Christopher W.; Klypin, A.; Ceverino, D.; Kacprzak, G. G.

    2007-12-01

    Analysis of mock quasar spectra of metal absorption lines in the proximity of formed galaxies in cosmological simulation is a highly promising approach for interpreting the efficiency with which gas is converted into stars in galaxies, the mechanisms of gas inflow in the context of the cosmic web, and the star-gas feedback processes in galaxies. We are undertaking a wholesale approach to use powerful Λ-CDM simulations to interpret high-quality absorption line data (HIRES/UVES) and high-quality galaxy imaging data (HST) for inferring the interplay between galaxies and metal enriched gas in the vicinity of galaxies (few hundred kpc). 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 radiative cooling, star formation, metal enrichment and thermal feedback due to type II and type Ia supernovae. We quantitatively compare the observed and simulated spatial and kinematic distribution of HI, MgII, CIV, and OVI absorption lines over a range of impact parameters 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. Disparities between the simulations and the statistical cross sections and velocity spreads of the absorption line data in turn provide powerful constraints on the galaxy feedback recipes, which we quantitatively examine.

  15. Radio continuum observations of local star-forming galaxies using the Caltech Continuum Backend on the green bank telescope

    SciTech Connect

    Rabidoux, Katie; Pisano, D. J.; Kepley, Amanda A.; Johnson, Kelsey E.; Balser, Dana S.

    2014-01-01

    We observed radio continuum emission in 27 local (D < 70 Mpc) star-forming galaxies with the Robert C. Byrd Green Bank Telescope between 26 GHz and 40 GHz using the Caltech Continuum Backend. We obtained detections for 22 of these galaxies at all four sub-bands and four more marginal detections by taking the average flux across the entire bandwidth. This is the first detection (full or marginal) at these frequencies for 22 of these galaxies. We fit spectral energy distributions (SEDs) for all of the four sub-band detections. For 14 of the galaxies, SEDs were best fit by a combination of thermal free-free and nonthermal synchrotron components. Eight galaxies with four sub-band detections had steep spectra that were only fit by a single nonthermal component. Using these fits, we calculated supernova rates, total number of equivalent O stars, and star formation rates within each ∼23'' beam. For unresolved galaxies, these physical properties characterize the galaxies' recent star formation on a global scale. We confirm that the radio-far-infrared correlation holds for the unresolved galaxies' total 33 GHz flux regardless of their thermal fractions, though the scatter on this correlation is larger than that at 1.4 GHz. In addition, we found that for the unresolved galaxies, there is an inverse relationship between the ratio of 33 GHz flux to total far-infrared flux and the steepness of the galaxy's spectral index between 1.4 GHz and 33 GHz. This relationship could be an indicator of the timescale of the observed episode of star formation.

  16. Galaxy Formation At Extreme Redshifts: Semi-Analytic Model Predictions And Challenges For Observations

    NASA Astrophysics Data System (ADS)

    Yung, L. Y. Aaron; Somerville, Rachel S.

    2017-06-01

    The well-established Santa Cruz semi-analytic galaxy formation framework has been shown to be quite successful at explaining observations in the local Universe, as well as making predictions for low-redshift observations. Recently, metallicity-based gas partitioning and H2-based star formation recipes have been implemented in our model, replacing the legacy cold-gas based recipe. We then use our revised model to explore the high-redshift Universe and make predictions up to z = 15. Although our model is only calibrated to observations from the local universe, our predictions seem to match incredibly well with mid- to high-redshift observational constraints available-to-date, including rest-frame UV luminosity functions and the reionization history as constrained by CMB and IGM observations. We provide predictions for individual and statistical galaxy properties at a wide range of redshifts (z = 4 - 15), including objects that are too far or too faint to be detected with current facilities. And using our model predictions, we also provide forecasted luminosity functions and other observables for upcoming studies with JWST.

  17. From Observations to Self-consistent Modelling of the ISM in Galaxies

    NASA Astrophysics Data System (ADS)

    de Avillez, M.; Breitschwerdt, D.

    Since we are on the verge of studying the ISM in great detail due to immensely improved observational facilities and techniques in all wavelength ranges and similar progress on the computer hard- and software side, a major goal of this symposium will be to stimulate an intense discussion between observers and theoreticians on a self-consistent picture of the ISM. Observers should tell us WHAT we see on ALL scales of the ISM, near and far, and what boundary conditions would be appropriate for realistic models, and theoreticians should point out what assumptions and simplifications their codes need, and WHAT future observations could test their models. Thus, the workshop will start with sessions on ISM observations: Bubbles, superbubbles, stellar winds, chimneys, galactic fountains, HVCs, X-ray halos, diffuse ionized gas in galaxies, formation of molecular clouds, magnetic fields and the dynamo mechanism in the Galaxy, and turbulence in the ISM. All these subjects are of great importance for the task at hand. Followed on the last day with a session on the self consistent picture of the ISM where observations that give us information of the self-consistent picture will discussed as well as the numerical modeling and techniques.

  18. Non-Gaussianities due to relativistic corrections to the observed galaxy bispectrum

    NASA Astrophysics Data System (ADS)

    Di Dio, E.; Perrier, H.; Durrer, R.; Marozzi, G.; Moradinezhad Dizgah, A.; Noreña, J.; Riotto, A.

    2017-03-01

    High-precision constraints on primordial non-Gaussianity (PNG) will significantly improve our understanding of the physics of the early universe. Among all the subtleties in using large scale structure observables to constrain PNG, accounting for relativistic corrections to the clustering statistics is particularly important for the upcoming galaxy surveys covering progressively larger fraction of the sky. We focus on relativistic projection effects due to the fact that we observe the galaxies through the light that reaches the telescope on perturbed geodesics. These projection effects can give rise to an effective fNL that can be misinterpreted as the primordial non-Gaussianity signal and hence is a systematic to be carefully computed and accounted for in modelling of the bispectrum. We develop the technique to properly account for relativistic effects in terms of purely observable quantities, namely angles and redshifts. We give some examples by applying this approach to a subset of the contributions to the tree-level bispectrum of the observed galaxy number counts calculated within perturbation theory and estimate the corresponding non-Gaussianity parameter, fNL, for the local, equilateral and orthogonal shapes. For the local shape, we also compute the local non-Gaussianity resulting from terms obtained using the consistency relation for observed number counts. Our goal here is not to give a precise estimate of fNL for each shape but rather we aim to provide a scheme to compute the non-Gaussian contamination due to relativistic projection effects. For the terms considered in this work, we obtain contamination of fNLloc ~ Script O(1).

  19. Multiwavelength Observations of the Most Massive Stellar Clusters in the Galaxy

    NASA Astrophysics Data System (ADS)

    Richards, Emily; Lang, C. C.; Trombley, C.; Figer, D. F.; HST/NICMOS GC Paschen Alpha Team

    2011-01-01

    The Galactic Center Arches and Quintuplet stellar clusters are two of the most luminous clusters in the Galaxy. These massive clusters produce high rates of ionizing photons and powerful winds which sculpt the surrounding interstellar medium (ISM) and form the Sickle and Arched Filaments HII regions. Recently, these clusters and HII regions have been studied in high resolution by Spitzer, Chandra and HST/NICMOS. Here we present a multiwavelength analysis of the interaction between the clusters and the ISM. Throughout the Galaxy, only a handful of similarly luminous and massive clusters are known. It is likely that other such clusters reside in our Galaxy but are obscured from optical detection. Using data from infrared and radio surveys, 40 candidate massive clusters have been identified. We have followed up on the interstellar environment of six candidate clusters using the VLA at 8.5 and 4.9 GHz. Parameters such as the Lyman continuum flux, electron density, and total ionized mass can be determined from these radio observations and can provide estimates of the stellar content in the candidate clusters. Finally, comparison between the radio and infrared (Spitzer) data will lead to a more complete understanding of the interaction between the stellar clusters and the ISM. This material is based upon work supported by the National Science Foundation under Grant Number 0907934. The authors also acknowledge support from the University of Iowa.

  20. Herschel And Alma Observations Of The Ism In Massive High-Redshift Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Wu, John F.; Aguirre, Paula; Baker, Andrew J.; Devlin, Mark J.; Hilton, Matt; Hughes, John P.; Infante, Leopoldo; Lindner, Robert R.; Sifón, Cristóbal

    2017-06-01

    The Sunyaev-Zel'dovich effect (SZE) can be used to select samples of galaxy clusters that are essentially mass-limited out to arbitrarily high redshifts. I will present results from an investigation of the star formation properties of galaxies in four massive clusters, extending to z 1, which were selected on the basis of their SZE decrements in the Atacama Cosmology Telescope (ACT) survey. All four clusters have been imaged with Herschel/PACS (tracing star formation rate) and two with ALMA (tracing dust and cold gas mass); newly discovered ALMA CO(4-3) and [CI] line detections expand an already large sample of spectroscopically confirmed cluster members. Star formation rate appears to anti-correlate with environmental density, but this trend vanishes after controlling for stellar mass. Elevated star formation and higher CO excitation are seen in "El Gordo," a violent cluster merger, relative to a virialized cluster at a similar high (z 1) redshift. Also exploiting ATCA 2.1 GHz observations to identify radio-loud active galactic nuclei (AGN) in our sample, I will use these data to develop a coherent picture of how environment influences galaxies' ISM properties and evolution in the most massive clusters at early cosmic times.

  1. Chandra Observation of the Core of the Galaxy Cluster AWM 7

    NASA Technical Reports Server (NTRS)

    Furusho, T.; Yanasaki, N. Y.; Ohashi, T.

    2003-01-01

    We present results from a Chandra observation of the core region of the nearby X-ray bright galaxy cluster AWM 7. There are blob-like substructures, which are seen in the energy band 2-10 keV, within 10 kpc (20") of the cD galaxy NGC 1129, and the brightest sub-peak has a spatial extent more than 4 kpc. We also notice that the central soft X-ray peak is offset from the optical center by 1.3 kpc. These structures have no correlated features in optical, infrared, or radio band. Energy spectrum of the hard sub-peak indicates a temperature higher than 3 keV with a metallicity less than 0.3 solar, or a power-law spectrum with photon index approximately 1.2. A hardness ratio map and a narrow Fe-K band image jointly indicate two Fe-rich blobs symmetrically located around the cD galaxy, with the direction perpendicular to the sub-peak direction. In larger scales (r less than 60 kpc), the temperature gradually drops from 4 keV to 2 keV toward the cluster center and the metal abundance rises steeply to a peak of 1.5 solar at r approximately equal to 7 kpc. These results indicate that a dynamical process is going on in the central region of AWM 7, which probably creates heated gas blobs and drives metal injection.

  2. A comparative study of local galaxy clusters - I. Derived X-ray observables

    NASA Astrophysics Data System (ADS)

    Rozo, E.; Rykoff, E. S.; Bartlett, J. G.; Evrard, A.

    2014-02-01

    We examine systematic differences in the derived X-ray properties of galaxy clusters as reported by three different groups: Vikhlinin et al., Mantz et al. and Plank Collaboration. The sample overlap between any two pairs of works ranges between 16 to 28 galaxy clusters. We find systematic differences in most reported X-ray properties, including the total cluster mass, M500. The most extreme case is an average 45 ± 5 per cent difference in cluster mass between the Plank Collaboration and Mantz et al., for clusters at z > 0.13 (averaged over 16 clusters). These differences also induce differences in cluster observables defined within an R500 aperture. After accounting for aperture differences, we find very good agreement in gas mass estimates between the different groups. However, the soft-band X-ray luminosity, LX, core-excised spectroscopic temperature, TX, and gas thermal energy, YX = MgasTX display mean differences at the 5-15 per cent level. We also find that the low (z ≤ 0.13) and high (z ≥ 0.13) redshift galaxy cluster samples in Plank Collaboration appear to be systematically different: the YSZ/YX ratio for each of these two sub-samples is ln (YSZ/YX) = -0.06 ± 0.04 and ln (YSZ/YX) = 0.08 ± 0.04, respectively.

  3. Dark matter constraints from a joint analysis of dwarf Spheroidal galaxy observations with VERITAS

    NASA Astrophysics Data System (ADS)

    Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Brantseg, T.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Christiansen, J. L.; Connolly, M. P.; Cui, W.; Daniel, M. K.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Geringer-Sameth, A.; Griffin, S.; Grube, J.; Hütten, M.; Hâkansson, N.; Hanna, D.; Hervet, O.; Holder, J.; Hughes, G.; Hummensky, B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Koushiappas, S.; Krause, M.; Krennrich, F.; Lang, M. J.; Lin, T. T. Y.; McArthur, S.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; Ong, R. A.; Otte, A. N.; Park, N.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Trepanier, S.; Tucci, J. V.; Tyler, J.; Wakely, S. P.; Weinstein, A.; Wilcox, P.; Williams, D. A.; Zitzer, B.; VERITAS Collaboration

    2017-04-01

    We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of ˜230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is 1.35 ×10-23 cm3 s-1 at 1 TeV for the bottom quark (b b ¯) final state, 2.85 ×10-24 cm3 s-1 at 1 TeV for the tau lepton (τ+τ-) final state and 1.32 ×10-25 cm3 s-1 at 1 TeV for the gauge boson (γ γ ) final state.

  4. Abundance patterns in the interstellar medium of early-type galaxies observed with Suzaku

    SciTech Connect

    Konami, Saori; Matsushita, Kyoko; Tamagawa, Toru; Nagino, Ryo

    2014-03-01

    We have analyzed 17 early-type galaxies, 13 ellipticals and 4 S0 galaxies, observed with Suzaku, and investigated metal abundances (O, Mg, Si, and Fe) and abundance ratios (O/Fe, Mg/Fe, and Si/Fe) in the interstellar medium (ISM). The emission from each on-source region, which is four times the effective radius, r {sub e}, is reproduced with one-temperature (1T) or two-temperature (2T) thermal plasma models as well as a multi-temperature model, using APEC plasma code version 2.0.1. The multi-temperature model gave almost the same abundances and abundance ratios with the 1T or 2T models. The weighted averages of the O, Mg, Si, and Fe abundances of all the sample galaxies derived from the multi-temperature model fits are 0.83 ± 0.04, 0.93 ± 0.03, 0.80 ± 0.02, and 0.80 ± 0.02 solar, respectively, in solar units according to the solar abundance table by Lodders in 2003. These abundances show no significant dependence on the morphology and environment. The systematic differences in the derived metal abundances between versions 2.0.1 and 1.3.1 of the APEC plasma codes were investigated. The derived O and Mg abundances in the ISM agree with the stellar metallicity within an aperture with a radius of one r {sub e} derived from optical spectroscopy. From these results, we discuss the past and present Type Ia supernova rates and star formation histories in early-type galaxies.

  5. Observational properties of simulated galaxies in overdense and average regions at redshifts z ≃ 6-12

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Shlosman, Isaac; Romano-Díaz, Emilio; Nagamine, Kentaro

    2015-07-01

    We use high-resolution zoom-in cosmological simulations of galaxies of Romano-Díaz et al., post-processing them with a panchromatic three-dimensional radiation transfer code to obtain the galaxy UV luminosity function (LF) at z ≃ 6-12. The galaxies are followed in a rare, heavily overdense region within a ˜5σ density peak, which can host high-z quasars, and in an average density region, down to the stellar mass of Mstar ˜ 4 × 107 M⊙. We find that the overdense regions evolve at a substantially accelerated pace - the most massive galaxy has grown to Mstar ˜ 8.4 × 1010 M⊙ by z = 6.3, contains dust of Mdust ˜ 4.1 × 108 M⊙, and is associated with a very high star formation rate, SFR ˜ 745 M⊙ yr- 1. The attained SFR-Mstar correlation results in the specific SFR slowly increasing with Mstar. Most of the UV radiation in massive galaxies is absorbed by the dust, its escape fraction fesc is low, increasing slowly with time. Galaxies in the average region have less dust, and agree with the observed UV LF. The LF of the overdense region is substantially higher, and contains much brighter galaxies. The massive galaxies are bright in the infrared (IR) due to the dust thermal emission, with LIR ˜ 3.7 × 1012 L⊙ at z = 6.3, while LIR < 1011 L⊙ for the low-mass galaxies. Therefore, ALMA can probe massive galaxies in the overdense region up to z ˜ 10 with a reasonable integration time. The UV spectral properties of discy galaxies depend significantly upon the viewing angle. The stellar and dust masses of the most massive galaxy in the overdense region are comparable to those of the sub-millimetre galaxy found by Riechers et al. at z = 6.3, while the modelled SFR and the sub-millimetre flux fall slightly below the observed one. Statistical significance of these similarities and differences will only become clear with the upcoming ALMA observations.

  6. Rotation curve fitting and its fatal attraction to cores in realistically simulated galaxy observations

    NASA Astrophysics Data System (ADS)

    Pineda, Juan C. B.; Hayward, Christopher C.; Springel, Volker; Mendes de Oliveira, Claudia

    2017-04-01

    We study the role of systematic effects in observational studies of the cusp-core problem under the minimum disc approximation using a suite of high-resolution (25-pc softening length) hydrodynamical simulations of dwarf galaxies. We mimic realistic kinematic observations and fit the mock rotation curves with two analytic models commonly used to differentiate cores from cusps in the dark matter distribution. We find that the cored pseudo-isothermal sphere (ISO) model is strongly favoured by the reduced χ ^2_ν of the fits in spite of the fact that our simulations contain cuspy Navarro-Frenk-White profiles (NFW). We show that even idealized measurements of the gas circular motions can lead to the incorrect answer if velocity underestimates induced by pressure support, with a typical size of order ∼5 km s-1 in the central kiloparsec, are neglected. Increasing the spatial resolution of the mock observations leads to more misleading results because the inner region, where the effect of pressure support is most significant, is better sampled. Fits to observations with a spatial resolution of 100 pc (2 arcsec at 10 Mpc) favour the ISO model in 78-90 per cent of the cases, while at 800-pc resolution, 41-77 per cent of the galaxies indicate the fictitious presence of a dark matter core. The coefficients of our best-fitting models agree well with those reported in observational studies; therefore, we conclude that NFW haloes cannot be ruled out reliably from this type of analysis.

  7. SMA observations on faint submillimeter galaxies with S {sub 850} < 2 mJy: Ultra dusty low-luminosity galaxies at high redshift

    SciTech Connect

    Chen, Chian-Chou; Cowie, Lennox L.; Barger, Amy J.; Williams, Jonathan P.; Wang, Wei-Hao

    2014-07-01

    We obtained Submillimeter Array (SMA) observations of eight faint (intrinsic 850 μm fluxes < 2 mJy) submillimeter galaxies (SMGs) discovered in SCUBA images of the massive lensing cluster fields A370, A2390, and A1689 and detected five. In total, we obtain five SMA detections, all of which have de-lensed fluxes <1 mJy with estimated total infrared luminosities 10{sup 10}-10{sup 12} L {sub ☉}, comparable to luminous infrared galaxies and normal star-forming galaxies. Based on the latest number counts, these galaxies contribute ∼70% of the 850 μm extragalactic background light and represent the dominant star-forming galaxy population in the dusty universe. However, only 40{sub −16}{sup +30}% of our faint SMGs would be detected in deep optical or near-infrared surveys, which suggests many of these sources are at high redshifts (z ≳ 3) or extremely dusty, and they are not included in current star formation history estimates.

  8. Preparing for JWST Observations. Insights from First Light and Assembly of Galaxies GTO Programs II: Studying galaxy properties with MIRI Spectroscopy

    NASA Astrophysics Data System (ADS)

    Garcia Marin, Macarena; Wright, Gillian; Rieke, George; MIRI GTO Team

    2017-06-01

    The MIRI instrument, a result of the collaborative work of a consortium of European and US institutes, is the only Mid-IR science instrument on board of the James Webb Space Telescope. It will achieve unprecedented sensitivity and spatial resolution in the 5-28 microns wavelength range. A significant part of the MIRI GTO time will be dedicated to extragalactic observations, with the aim of covering a broad range of redshifts and giving new insights to galaxy history through time. While some of the programme will use deep MIRI images complemented with NIR observations, in this talk I will focus on the spectroscopic studies of galaxies planned by the MIRI team. At redshifts of about 7-8 we will study the reionization epoch, by observing spectroscopically confirmed targets. The strong emission lines predicted for these galaxies will be measured with the MIRI MRS (an integral field spectrometer).Moving closer in redshift, MIRI will be able to provide spatially resolved spectroscopy of massive dusty star forming galaxies at redshifts of about 3 or higher. This will give us the opportunity to study obscured AGNs, internal extinction and star formation activity, and gas-kpc scales kinematics. Finally, in the local Universe, we will observe the nuclei of well-known nearby galaxies with the MIRI MRS and the NIRSpec IFU. The spectra will yield new insights into the distribution, physical conditions, and kinematics of the various gas components (ionized, atomic, or molecular) in the immediate vicinity of the nucleus.In this contribution I will present this overall spectroscopic GTO program, giving insight into the observing strategies we plan to use for optimally implementing our observations.

  9. HUBBLE SPACE TELESCOPE WFC3 EARLY RELEASE SCIENCE: EMISSION-LINE GALAXIES FROM INFRARED GRISM OBSERVATIONS

    SciTech Connect

    Straughn, Amber N.; Gardner, Jonathan P.; Kuntschner, Harald; Kuemmel, Martin; Walsh, Jeremy R.; Cohen, Seth H.; Windhorst, Rogier A.; Malhotra, Sangeeta; Rhoads, James; O'Connell, Robert W.; Pirzkal, Norbert; Bond, Howard E.; Meurer, Gerhardt; McCarthy, Patrick J.; Hathi, Nimish P.; Balick, Bruce; Calzetti, Daniela; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.

    2011-01-15

    We present grism spectra of emission-line galaxies (ELGs) from 0.6 to 1.6 {mu}m from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope. These new infrared grism data augment previous optical Advanced Camera for Surveys G800L 0.6-0.95 {mu}m grism data in GOODS-South from the PEARS program, extending the wavelength coverage well past the G800L red cutoff. The Early Release Science (ERS) grism field was observed at a depth of two orbits per grism, yielding spectra of hundreds of faint objects, a subset of which is presented here. ELGs are studied via the H{alpha}, [O III], and [O II] emission lines detected in the redshift ranges 0.2 {approx}< z {approx}< 1.4, 1.2 {approx}< z {approx}< 2.2, and 2.0 {approx}< z {approx}< 3.3, respectively, in the G102 (0.8-1.1 {mu}m; R {approx_equal} 210) and G141 (1.1-1.6 {mu}m; R {approx_equal} 130) grisms. The higher spectral resolution afforded by the WFC3 grisms also reveals emission lines not detectable with the G800L grism (e.g., [S II] and [S III] lines). From these relatively shallow observations, line luminosities, star formation rates, and grism spectroscopic redshifts are determined for a total of 48 ELGs to m A{sub B(F098M)} {approx_equal} 25 mag. Seventeen GOODS-South galaxies that previously only had photometric redshifts now have new grism-spectroscopic redshifts, in some cases with large corrections to the photometric redshifts ({Delta}z {approx_equal} 0.3-0.5). Additionally, one galaxy had no previously measured redshift but now has a secure grism-spectroscopic redshift, for a total of 18 new GOODS-South spectroscopic redshifts. The faintest source in our sample has a magnitude m{sub AB(F098M)}= 26.9 mag. The ERS grism data also reflect the expected trend of lower specific star formation rates for the highest mass galaxies in the sample as a function of redshift, consistent with downsizing and discovered previously from large surveys. These results demonstrate the remarkable efficiency and capability of the

  10. AN OBSERVED LINK BETWEEN ACTIVE GALACTIC NUCLEI AND VIOLENT DISK INSTABILITIES IN HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Bournaud, Frederic; Juneau, Stephanie; Le Floc'h, Emeric; Mullaney, James; Daddi, Emanuele; Duc, Pierre-Alain; Elbaz, David; Salmi, Fadia; Dekel, Avishai; Dickinson, Mark

    2012-09-20

    We provide evidence for a correlation between the presence of giant clumps and the occurrence of active galactic nuclei (AGNs) in disk galaxies. Giant clumps of 10{sup 8}-10{sup 9} M{sub Sun} arise from violent gravitational instability in gas-rich galaxies, and it has been proposed that this instability could feed supermassive black holes (BHs). We use emission line diagnostics to compare a sample of 14 clumpy (unstable) disks and a sample of 13 smoother (stable) disks at redshift z {approx} 0.7. The majority of clumpy disks in our sample have a high probability of containing AGNs. Their [O III] {lambda}5007 emission line is strongly excited, inconsistent with low-metallicity star formation (SF) alone. [Ne III] {lambda}3869 excitation is also higher. Stable disks rarely have such properties. Stacking ultra sensitive Chandra observations (4 Ms) reveals an X-ray excess in clumpy galaxies, which confirms the presence of AGNs. The clumpy galaxies in our intermediate-redshift sample have properties typical of gas-rich disk galaxies rather than mergers, being in particular on the main sequence of SF. This suggests that our findings apply to the physically similar and numerous gas-rich unstable disks at z > 1. Using the observed [O III] and X-ray luminosities, we conservatively estimate that AGNs hosted by clumpy disks have typical bolometric luminosities of the order of a few 10{sup 43} erg s{sup -1}, BH growth rates m-dot{sub BH}{approx}10{sup -2} M{sub Sun} yr{sup -1}, and that these AGNs are substantially obscured in X-rays. This moderate-luminosity mode could provide a large fraction of today's BH mass with a high duty cycle (>10%), accretion bursts with higher luminosities being possible over shorter phases. Violent instabilities at high redshift (giant clumps) are a much more efficient driver of BH growth than the weak instabilities in nearby spirals (bars), and the evolution of disk instabilities with mass and redshift could explain the simultaneous downsizing of

  11. Testing the dark matter origin of the WMAP-Planck haze with radio observations of spiral galaxies

    SciTech Connect

    Carlson, Eric; Linden, Tim; Profumo, Stefano; Hooper, Dan E-mail: dhooper@fnal.gov E-mail: profumo@ucsc.edu

    2013-07-01

    If the Galactic WMAP radio haze, as recently confirmed by Planck, is produced by dark matter annihilation or decay, similar diffuse radio halos should exist around other galaxies with physical properties comparable to the Milky Way. If instead the haze is due to an astrophysical mechanism peculiar to the Milky Way or to a transient event, a similar halo need not exist around all Milky Way ''twins''. We use radio observations of 66 spiral galaxies to test the dark matter origin of the haze. We select galaxies based on morphological type and maximal rotational velocity, and obtain their luminosities from a 1.49 GHz catalog and additional radio observations at other frequencies. We find many instances of galaxies with radio emission that is less than 5% as bright as naively expected from dark matter models that could produce the Milky Way haze, and at least 3 galaxies that are less than 1% as bright as expected, assuming dark matter distributions, magnetic fields, and cosmic ray propagation parameters equal to those of the Milky Way. For reasonable ranges for the variation of these parameters, we estimate the fraction of galaxies that should be expected to be significantly less bright in radio, and argue that this is marginally compatible with the observed distribution. While our findings therefore cannot rule out a dark matter origin for the radio haze at this time, we find numerous examples (including the Andromeda Galaxy) where, if dark matter is indeed the origin of the Milky Way haze, some mechanism must be in place to suppress the corresponding haze of the external galaxy. We point out that Planck data will offer opportunities to improve this type of constraint in a highly relevant frequency range and for a potentially larger set of candidate galaxies.

  12. LBT/LUCIFER Observations of the z ~ 2 Lensed Galaxy J0900+2234

    NASA Astrophysics Data System (ADS)

    Bian, Fuyan; Fan, Xiaohui; Bechtold, Jill; McGreer, Ian D.; Just, Dennis W.; Sand, David J.; Green, Richard F.; Thompson, David; Peng, Chien Y.; Seifert, Walter; Ageorges, Nancy; Juette, Marcus; Knierim, Volker; Buschkamp, Peter

    2010-12-01

    We present rest-frame optical images and spectra of the gravitationally lensed, star-forming galaxy J0900+2234 (z = 2.03). The observations were performed with the newly commissioned LUCIFER1 near-infrared (NIR) instrument mounted on the Large Binocular Telescope. We fitted lens models to the rest-frame optical images and found that the galaxy has an intrinsic effective radius of 7.4 ± 0.8 kpc with a lens magnification factor of about 5 for the A and B components. We also discovered a new arc belonging to another lensed high-z source galaxy, which makes this lens system a potential double Einstein ring system. Using the high signal-to-noise ratio rest-frame spectra covered by the H + K band, we detected Hβ, [O III], Hα, [N II], and [S II] emission lines. Detailed physical properties of this high-z galaxy were derived. The extinction toward the ionized H II regions (Eg (B - V)) was computed from the flux ratio of Hα and Hβ and appears to be much higher than that toward the stellar continuum (Es (B - V)), derived from the optical and NIR broadband photometry fitting. The metallicity was estimated using N2 and O3N2 indices. It is in the range of 1/5-1/3 solar abundance, which is much lower than for typical z ~ 2 star-forming galaxies. From the flux ratio of [S II]λ6717 and [S II]λ6732, we found that the electron number density of the H II regions in the high-z galaxy was sime1000 cm-3, consistent with other z ~ 2 galaxies but much higher than that in local H II regions. The star formation rate was estimated via the Hα luminosity, after correction for the lens magnification, to be about 365 ± 69 M sun yr-1. Combining the FWHM of Hα emission lines and the half-light radius, we found that the dynamical mass of the lensed galaxy is (5.8 ± 0.9) × 1010 M sun. The gas mass is (5.1 ± 1.1) × 1010 M sun from the Hα flux surface density using global Kennicutt-Schmidt law, indicating a very high gas fraction of 0.79 ± 0.19 in J0900+2234. Based on data acquired

  13. Multi-Wavelength Observations of the Supernova Remnant Populations in the Nearby Spiral Galaxies IC 342 and NGC 4258

    NASA Astrophysics Data System (ADS)

    Pannuti, Thomas; Chomiuk, L.; Grimes, C. K.; Staggs, W. D.; Tussey, J. M.; Laine, S.; Schlegel, E.

    2011-01-01

    Supernova remnants (SNRs) are intimately tied to many crucial processes associated with the interstellar medium of galaxies, such as the acceleration of cosmic-ray particles and the deposition of vast amounts of kinetic energy and chemically-enriched material. Well-known observational challenges in the study of SNRs located in the Milky Way Galaxy (for example, formidable extinction along Galactic lines of sight and considerable uncertainties in the distances to these sources) have motivated searches for SNRs in nearby galaxies at such characteristic wavelengths as X-ray, optical and radio. These searches have revealed a considerable number of SNRs and led to new insights into their properties, but the SNR populations in only a handful of nearby galaxies have been adequately surveyed at multiple wavelengths. To help remedy this situation, we are conducting a multi-wavelength study of the SNR population of selected nearby galaxies. To illustrate our work, we present the results of studies of the SNR population in two nearby spiral galaxies, IC 342 and NGC 4258. Our results draw upon the analysis of pointed archival radio and X-ray observations of these two galaxies. Initial results will be presented and discussed.

  14. CHARACTERIZING ULTRAVIOLET AND INFRARED OBSERVATIONAL PROPERTIES FOR GALAXIES. I. INFLUENCES OF DUST ATTENUATION AND STELLAR POPULATION AGE

    SciTech Connect

    Mao Yewei; Kong Xu; Kennicutt, Robert C. Jr.; Hao, Cai-Na; Zhou Xu E-mail: xkong@ustc.edu.cn

    2012-09-20

    The correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color (or ultraviolet spectral slope), i.e., the IRX-UV (or IRX-{beta}) relation, found in studies of starburst galaxies is a prevalent recipe for correcting extragalactic dust attenuation. Considerable dispersion in this relation discovered for normal galaxies, however, complicates its usability. In order to investigate the cause of the dispersion and to have a better understanding of the nature of the IRX-UV relation, in this paper, we select five nearby spiral galaxies, and perform spatially resolved studies on each of the galaxies, with a combination of ultraviolet and infrared imaging data. We measure all positions within each galaxy and divide the extracted regions into young and evolved stellar populations. By means of this approach, we attempt to discover separate effects of dust attenuation and stellar population age on the IRX-UV relation for individual galaxies. In this work, in addition to dust attenuation, stellar population age is interpreted to be another parameter in the IRX-UV function, and the diversity of star formation histories is suggested to disperse the age effects. At the same time, strong evidence shows the need for more parameters in the interpretation of observational data, such as variations in attenuation/extinction law. Fractional contributions of different components to the integrated luminosities of the galaxies suggest that the integrated measurements of these galaxies, which comprise different populations, would weaken the effect of the age parameter on IRX-UV diagrams. The dependence of the IRX-UV relation on luminosity and radial distance in galaxies presents weak trends, which offers an implication of selective effects. The two-dimensional maps of the UV color and the infrared-to-ultraviolet ratio are displayed and show a disparity in the spatial distributions between the two galaxy parameters, which offers a spatial interpretation of the scatter

  15. Relativistic Fe Kα line study in Seyfert 1 galaxies observed with Suzaku

    NASA Astrophysics Data System (ADS)

    Mantovani, G.; Nandra, K.; Ponti, G.

    2016-06-01

    We present an analysis of a sample of Seyfert 1 galaxies observed with Suzaku. The aim of this work is to examine critically the evidence for a relativistic Fe Kα line in the X-ray spectra of these active galactic nuclei. The sample was compiled from those sources in which a relativistic component was missing in at least one XMM-Newton observation. We analysed the Suzaku spectra of these objects in order to have more constraints on the high-energy emission, including the Compton reflection hump. The results show that the relativistic Fe Kα line is detected (at >95 per cent confidence) in all sources observed with high-signal-to-noise ratio (e.g. where the counts in the 5-7 keV energy band are ≳4 × 104). This is in agreement with the idea that relativistic lines are a ubiquitous feature in the spectra of Seyfert galaxies, but are often difficult to detect without very high-quality data. We also investigate the relation between the Fe Kα line and the reflection continuum at high energies. For most of the sample, the strength of the reflection component is consistent with that of the line. There are exceptions in both senses, however i.e. where the reflection continuum is strong but with weak line emission, and vice versa. These observations present a challenge for standard reflection models.

  16. LATE-TIME OBSERVATIONS OF GRB 080319B: JET BREAK, HOST GALAXY, AND ACCOMPANYING SUPERNOVA

    SciTech Connect

    Tanvir, N. R.; O'Brien, P. T.; Wiersema, K.; Starling, R. L. C.; Rol, E.; Levan, A. J.; Svensson, K.; Fruchter, A. S.; Granot, J.; Jakobsson, P.; Fynbo, J.; Hjorth, J.; Curran, P. A.; Burrows, D. N.; Genet, F.

    2010-12-10

    The Swift-discovered GRB 080319B was by far the most distant source ever observed at naked-eye brightness, reaching a peak apparent magnitude of 5.3 at a redshift of z = 0.937. We present our late-time optical (Hubble Space Telescope, Gemini, and Very Large Telescope) and X-ray (Chandra) observations, which confirm that an achromatic break occurred in the power-law afterglow light curve at {approx}11 days post-burst. This most likely indicates that the gamma-ray burst (GRB) outflow was collimated, which for a uniform jet would imply a total energy in the jet E{sub jet} {approx}> 10{sup 52} erg. Our observations also show a late-time excess of red light, which is well explained if the GRB was accompanied by a supernova (SN), similar to those seen in some other long-duration GRBs. The latest observations are dominated by light from the host and show that the GRB took place in a faint dwarf galaxy (r(AB) {approx} 27.0, rest frame M{sub B} {approx} -17.2). This galaxy is small even by the standards of other GRB hosts, which is suggestive of a low-metallicity environment. Intriguingly, the properties of this extreme event-a small host and bright SN-are entirely typical of the very low luminosity bursts such as GRB 980425 and GRB 060218.

  17. A Galaxy Cluster Collision Viewed Along the Line of Sight: Simulated X-ray Observations

    NASA Astrophysics Data System (ADS)

    ZuHone, John; Ricker, P.; Lamb, D.; Yang, H.

    2008-05-01

    Several lines of evidence have suggested that the the galaxy cluster Cl 0024+17, an apparently relaxed system, is actually a collision of two clusters, the interaction occurring along our line of sight. In this paper we present a high-resolution N-body/hydrodynamics simulation of such a collision. We have created mock X-ray observations of our simulated system using MARX, a program that simulates the on-orbit performance of the Chandra X-ray Observatory. We analyze these simulated data to generate profiles of the surface brightness and temperature. The simulated surface brightness profiles are better fit by a superposition of two β-model profiles than a single profile, in agreement with the observations of Cl 0024+17. However, due to projection effects, much of the post-collision density and temperature structure of the clusters is not seen in the observations. In particular, the observed temperatures from spectral fitting are much lower than the temperature of the hottest gas. We determine from our fitted profiles that if the system is modeled as a single cluster, the hydrostatic mass estimate is a factor 2-3 less than the actual mass, but if the system is modeled as two galaxy clusters in superposition, a hydrostatic mass estimation can be made which is accurate to within 10-20%.

  18. Observational Constraints on the Link Between the Intracluster Medium and Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Fogarty, Kevin; Postman, Marc; Donahue, Megan; CLASH

    2017-01-01

    We use data from Chandra, HST, Spitzer, and Herschel to study the nature of feedback in the brightest cluster galaxies (BCGs) of cool core galaxy clusters. Using the 16-band photometry HST available with CLASH in combination with observations taken with Spitzer, Herschel, and Chandra, we study the nature of the feedback mechanism required to offset cooling. While a great deal of progress has been made on this front, there is still much to learn from the feedback-affected stellar populations of cool core BCGs and X-ray observations of the intracluster medium (ICM).With UV through FIR SED fitting, we estimate the star formation rate, dust content, and starburst duration in UV-bright cool core BCGs in CLASH, and examine relationships between these findings and ICM cooling time and free-fall time profiles derived from Chandra X-ray imaging. We present observational evidence constraining the duration of feedback episodes and find a very tight relationship between the BCG star formation rate and the ratio of ICM cooling time to free-fall time (tcool/tff). Our observational results are fully consistent with a scenario where condensation of a depleting supply of thermally instable overdensities of the ICM gas are fueling long-duration (> 1 Gyr) BCG starbursts. We discuss the implications of our findings for theoretical models of BCG-ICM interaction.

  19. CO observations of the SAB galaxies NGC 157, 2903, 4321, and 5248, and the Seyfert galaxy NGC 1068

    NASA Astrophysics Data System (ADS)

    Elmegreen, D. M.; Elmegreen, B. G.

    1982-04-01

    Extragalactic carbon monoxide emission regions can, in principle, be located more precisely than the telescope beamwidth by using optically derived velocity distributions which have much higher angular resolution. Using this technique, the CO emission from five distant galaxies was analyzed. CO emission from NGC 1068 is strongest in the central region. In NGC 4321, it is strongest in the long bright spiral arms. CO emission from NGC 157 and NGC 2903 occurs more uniformly over the disk of these galaxies; the H II regions and dust clouds are more uniformly distributed in these galaxies as well. In NGC 157, the CO is brightest from the area including the NE spiral arm, which has more continuity and bright star formation than the SW arm. These results agree with the expectation that CO emission should be intensified near the H II regions and obvious dust clouds that usually concentrate near the spiral arms.

  20. Molecular Line Emission as a Tool for Galaxy Observations (LEGO). I. HCN as a tracer of moderate gas densities in molecular clouds and galaxies

    NASA Astrophysics Data System (ADS)

    Kauffmann, Jens; Goldsmith, Paul F.; Melnick, Gary; Tolls, Volker; Guzman, Andres; Menten, Karl M.

    2017-09-01

    Trends observed in galaxies, such as the Gao & Solomon relation, suggest a linear relationship between the star formation rate and the mass of dense gas available for star formation. Validation of such trends requires the establishment of reliable methods to trace the dense gas in galaxies. One frequent assumption is that the HCN (J = 1-0) transition is unambiguously associated with gas at H2 densities ≫ 104 cm-3. If so, the mass of gas at densities ≫ 104 cm-3 could be inferred from the luminosity of this emission line, LHCN (1-0). Here we use observations of the Orion A molecular cloud to show that the HCN (J = 1-0) line traces much lower densities 103 cm-3 in cold sections of this molecular cloud, corresponding to visual extinctions AV ≈ 6 mag. We also find that cold and dense gas in a cloud like Orion produces too little HCN emission to explain LHCN (1-0) in star forming galaxies, suggesting that galaxies might contain a hitherto unknown source of HCN emission. In our sample of molecules observed at frequencies near 100 GHz (also including 12CO, 13CO, C18O, CN, and CCH), N2H+ is the only species clearly associated with relatively dense gas.

  1. Observed galaxy number counts on the lightcone up to second order: I. Main result

    SciTech Connect

    Bertacca, Daniele; Maartens, Roy; Clarkson, Chris E-mail: roy.maartens@gmail.com

    2014-09-01

    We present the galaxy number overdensity up to second order in redshift space on cosmological scales for a concordance model. The result contains all general relativistic effects up to second order that arise from observing on the past light cone, including all redshift effects, lensing distortions from convergence and shear, and contributions from velocities, Sachs-Wolfe, integrated SW and time-delay terms. This result will be important for accurate calculation of the bias on estimates of non-Gaussianity and on precision parameter estimates, introduced by nonlinear projection effects.

  2. Multi-wavelength observations of galaxy clusters: Population evolution and scaling relations for intermediate-redshift clusters

    NASA Astrophysics Data System (ADS)

    Connor, Thomas Patrick

    Galaxy clusters are key signatures of the formation of structure in the Universe due to their positions at the nodes of the cosmic web. However, these privileged positions feature significant amounts of activity as a consequence of frequent accretion and collisions with other galaxies and clusters of galaxies. Thus, a rigorous understanding of cluster evolution constrains not only cosmological structure formation but also galaxy dynamics in the most extreme environments. Here, we examine the evolution of clusters in two situations: how the properties of the hot intracluster gas changes with the total masses of the clusters at the observational frontiers of mass and redshift; and how cluster galaxies evolve with redshift in some of the most massive clusters in the Universe. In Chapter 2 we examine a population of moderate-luminosity clusters at intermediate redshifts using the XMM-Newton telescope with well-determined masses from Hubble Space Telescope (HST) observations. We find that these systems do not deviate from scaling relations between mass, luminosity, and temperature derived from more massive clusters, implying that, even at the redshifts and masses probed here, gravitational energetics still dominate over supernovae. In Chapter 3 we utilize new techniques to maximize a multi-wavelength dataset from HST of 25 massive galaxy clusters. We present new methods for detection and photometry of galaxies in the presence of inconsistent, diffuse background. Using these techniques, we construct a photometric catalog down to M* + 4-5 for clusters at redshift z 0:2 to z 0:9, which we validate with comparisons to spectral observations and a similar catalog. We also consider the luminosity function for these clusters; we find a drop-off in the faint-end slope when only selecting red sequence galaxies. Finally, in Chapter 4, we exploit our new photometric catalogs to study the evolution of the red galaxies, the "red sequence of galaxies," in these massive clusters of

  3. Redshift observations of Abell/ACO galaxy clusters in two candidate superclusters

    NASA Astrophysics Data System (ADS)

    Batuski, D. J.; Maurogordato, S.; Balkowski, C.; Olowin, R. P.

    1995-02-01

    The results of spectroscopic observations of five R greater than or equal to 1 clusters of galaxies from the Abell (1958) and Abell et al. (1989) (hereafter ACO) catalogs are presented. The observations were conducted at the ESO 3.6m telescope with the EFOSC spectrograph and PUMA hole-punch aperture plates. Two of the clusters (A2576 and A2628) had been identified as members of one candidate supercluster that appears particularly dense in projection, and the other three clusters (A3802, A3817, and A3834) were in another candidate supercluster, based on redshifts estimated from the magnitudes of tenth brightest galaxies. Our observations confirm very similar redshifts for A2576 and A2628 ( z = 0.1875 and z = 0.1858, respectively) and for A3802 and A3834 (z = 0.1579 and z = 0.1518). From the agreement in redshifts and the proximity on the sky, it is suggestive that both pairs are indeed components of superclusters, although redshifts of other nearby candidates must be measured to determine the significance of the structure present. The fifth cluster, A3817, has a mean redshift of z = 0.2115, and so appears to be background to any possible A3802/A3834 supercluster. We note that the complex of clusters around A2576 and A2628 is a region of high spatial density, even ignoring the many clusters with unmeasured redshift. The region is an exceptional opportunity for large-scale structure study.

  4. KEPLER OBSERVATIONS OF THE SEYFERT 1 GALAXY II ZW 229.015

    SciTech Connect

    Carini, M. T.; Ryle, Wesley T.

    2012-04-10

    The Seyfert 1 galaxy II ZW 229.015 has been observed with the Kepler spacecraft since quarter 4 of Kepler science operations. The results of the quarters 4-7 (1 year) Kepler observations are presented in this paper. We find the source to be highly variable on multiple timescales, with discrete variations occurring on timescales as short as tens of hours with amplitudes as small as 0.5%. Such small amplitude, rapid variability has never before been detected in active galactic nuclei. The presence of a strong galaxy component dilutes the variability determined from the photometric aperture used in the standard Kepler PDC analysis. Using the tools provided by the Kepler Guest Observer Office and simultaneous V-band photometry found in the literature, we determine an optimal customized aperture for photometry of this source with Kepler. The results of a PSRESP analysis reveal tentative evidence of a characteristic variability timescale in the power spectrum. Using this timescale, we estimate the mass of the central supermassive black hole and this estimate is consistent with the virial mass estimate from reverberation mapping studies.

  5. Observations of the z = 4.514 radio galaxy RC J0311+0507

    NASA Astrophysics Data System (ADS)

    Parijskij, Yu. N.; Thomasson, P.; Kopylov, A. I.; Zhelenkova, O. P.; Muxlow, T. W. B.; Beswick, R.; Soboleva, N. S.; Temirova, A. V.; Verkhodanov, O. V.

    2014-04-01

    RC J0311+0507 is one of the most luminous objects in the high-redshift Universe having L ≥ 3 × 1029 W Hz-1 at a 500 MHz rest frequency. A very steep radio spectrum and an indication of a Fanaroff-Riley type II (FR II) structure from early Very Large Array (VLA) maps suggested the presence of a supermassive black hole inside the parent galaxy. Multi-Element Radio-Linked Interferometer Network and European Very Long Baseline Interferometer Network maps (intensity and polarization) of this object at 1.7 and 5 GHz with an order of magnitude better resolution than that of the VLA are presented. Also included are further optical observations with the Russian 6-m telescope and infrared K-band observations with the United Kingdom Infra-Red Telescope, which indicate the object to be a galaxy. The new radio observations now confirm the source's structure to be that of an FR II, but with a high degree of asymmetry in the flux densities of the source components.

  6. BIMA CO (1-0) Observations of the Dwarf Elliptical Galaxy NGC 404

    NASA Astrophysics Data System (ADS)

    Taylor, C. L.; Petitpas, G. R.

    2004-12-01

    We present high resolution observations of the CO emission in NGC 404, a nearby dwarf elliptical (dE) galaxy (D = 3.3 Mpc). NGC 404 is only the third dwarf elliptical to have its CO emission mapped by interferometric observations, and is the first outside the Local Group. Our observations show a very concentrated, marginally resolved structure about 9 × 9 arcseconds in diameter. This corresponds to a very small cloud at the center of a much larger distribution of stars. NGC 404 is surrounded by a doughnut shaped distribution of HI gas centered on the stellar component. The CO and HI appear to be kinematically distinct components, suggesting that the HI may be part of the galaxy's original gas distribution, while the CO may be recycled from the products of stellar evolution. C.L.T. has been supported by CSU Sacramento via a Research and Creative Activity Award. G.R.P. has been supported by the Laboratory for Millimeter-Wave Astronomy through NSF grant AST 99-81289

  7. Observations of Interstellar Hydrogen Fluoride and Hydrogen Chloride in the Galaxy

    NASA Astrophysics Data System (ADS)

    Monje, Raquel R.; Lis, Darek C.; Phillips, Thomas G.; Goldsmith, Paul F.; Emprechtinger, Martin; Neufeld, David A.

    2011-06-01

    We present Herschel/HIFI observations of interstellar hydrogen chloride (HCl) and hydrogen fluoride (HF) along the line-of-sight towards Galactic sources with strong submillimeter continuum emission from the PRISMAS and HEXOS GT KP. The halogen-containing molecules are of special interest because of their unique thermochemistry and their important role as tracers of the neutral ISM. The detection of foreground absorption by HF J = 1--0 transition line in each source probes the distribution of HF throughout the Milky Way, in diffuse clouds with varying values of the visual extinction, as a potential valuable surrogate for molecular hydrogen. For the optically thin absorption components we calculate the column densities of HF. We find that, in many of the background clouds, the abundances of HF with respect to H_2 is consistent with the theoretical prediction that HF is the main reservoir of gas-phase fluorine for these clouds. Observations of hydrogen chloride isotopologues, H35Cl and H37Cl J = 1--0 transition line at different galactocentric distances provide insights of how elemental abundances change with location in the Galaxy. We model the HCl observations with a non-LTE radiative transfer model to derive gas densities and HCl column densities for sources with HCl emission. Interstellar HCl abundances and isotopic ratios [Cl35/Cl37] are essential for improving our understanding of stellar nucleosynthesis and global chemical enrichment and evolution in the Galaxy.

  8. VizieR Online Data Catalog: X-ray observations of HCG galaxies (Tzanavaris+, 2016)

    NASA Astrophysics Data System (ADS)

    Tzanavaris, P.; Hornschemeier, A. E.; Gallagher, S. C.; Lenkic, L.; Desjardins, T. D.; Walker, L. M.; Johnson, K. E.; Mulchaey, J. S.

    2016-04-01

    In this paper we study a sample of 15 compact groups (CGs) observed with Chandra/ACIS, Swift/UVOT and Spitzer/IRAC-MIPS for which archival data exist, allowing us to obtain SFRs, stellar masses, sSFRs and X-ray fluxes and luminosities. Table 1 shows the group sample, including redshifts, luminosity distances and group evolutionary types. Allowing for the fact that some galaxies do not fall in the field of view of all three instruments, the total number of CG galaxies analyzed is 47. Details on the Swift and Spitzer observations and data for systems in this sample can be found in Tzanavaris et al. (2010ApJ...716..556T) and (L. Lenkic et al. 2015, in preparation). For Chandra/ACIS observations we refer the reader to Tzanavaris et al. (2014, J/ApJS/212/9) and Desjardins et al. (2013ApJ...763..121D; 2014ApJ...790..132D). (2 data files).

  9. ALMA Observations of Gas-rich Galaxies in z ˜ 1.6 Galaxy Clusters: Evidence for Higher Gas Fractions in High-density Environments

    NASA Astrophysics Data System (ADS)

    Noble, A. G.; McDonald, M.; Muzzin, A.; Nantais, J.; Rudnick, G.; van Kampen, E.; Webb, T. M. A.; Wilson, G.; Yee, H. K. C.; Boone, K.; Cooper, M. C.; DeGroot, A.; Delahaye, A.; Demarco, R.; Foltz, R.; Hayden, B.; Lidman, C.; Manilla-Robles, A.; Perlmutter, S.

    2017-06-01

    We present ALMA CO (2-1) detections in 11 gas-rich cluster galaxies at z ˜ 1.6, constituting the largest sample of molecular gas measurements in z > 1.5 clusters to date. The observations span three galaxy clusters, derived from the Spitzer Adaptation of the Red-sequence Cluster Survey. We augment the >5σ detections of the CO (2-1) fluxes with multi-band photometry, yielding stellar masses and infrared-derived star formation rates, to place some of the first constraints on molecular gas properties in z ˜ 1.6 cluster environments. We measure sizable gas reservoirs of 0.5-2 × 1011 M ⊙ in these objects, with high gas fractions (f gas) and long depletion timescales (τ), averaging 62% and 1.4 Gyr, respectively. We compare our cluster galaxies to the scaling relations of the coeval field, in the context of how gas fractions and depletion timescales vary with respect to the star-forming main sequence. We find that our cluster galaxies lie systematically off the field scaling relations at z = 1.6 toward enhanced gas fractions, at a level of ˜4σ, but have consistent depletion timescales. Exploiting CO detections in lower-redshift clusters from the literature, we investigate the evolution of the gas fraction in cluster galaxies, finding it to mimic the strong rise with redshift in the field. We emphasize the utility of detecting abundant gas-rich galaxies in high-redshift clusters, deeming them as crucial laboratories for future statistical studies.

  10. Suzaku observations of metal distribution out to 0.5 r180 in the intracluster medium of four galaxy groups

    NASA Astrophysics Data System (ADS)

    Sasaki, Toru; Matsushita, Kyoko; Sato, Kosuke

    We studied the distributions of metal abundances and metal-mass-to-light ratios in the intracluster medium of four galaxy groups, MKW 4, HCG 62, the NGC 1550 group, and the NGC 5044 group, out to ˜ 0.5 r_{180} observed with Suzaku.The Fe abundance decreases with radius, and about 0.2-0.4 solar beyond 0.1 r _{180}. At a given radius in units of r_{180}, the Fe abundance in the ICM of the four galaxy groups were consistent or smaller than those of clusters of galaxies. The Mg/Fe and Si/Fe ratios in the ICM are nearly constant at the solar ratio out to 0.5 r_{180}. Since the metals have been synthesized in galaxies, we collected K-band luminosities of galaxies from Two Micron All Sky Survey catalogue and calculated the integrated iron-mass-to-light-ratios (IMLR), or the ratios of the iron mass in the ICM to light from stars in galaxies. The groups with smaller gas mass to light ratios have smaller IMLR values and the IMLR inversely correlated with the entropy excess. Based on these abundance features, we discussed the past history of metal enrichment process in groups of galaxies. These results and discussions were shown in Sasaki et al. 2014,ApJ,781,36.

  11. Metal Distributions out to 0.5 r 180 in the Intracluster Medium of Four Galaxy Groups Observed with Suzaku

    NASA Astrophysics Data System (ADS)

    Sasaki, Toru; Matsushita, Kyoko; Sato, Kosuke

    2014-01-01

    We studied the distributions of metal abundances and metal-mass-to-light ratios in the intracluster medium (ICM) of four galaxy groups, MKW 4, HCG 62, the NGC 1550 group, and the NGC 5044 group, out to ~0.5 r 180 observed with Suzaku. The iron abundance decreases with radius and is about 0.2-0.4 solar beyond 0.1 r 180. At a given radius in units of r 180, the iron abundance in the ICM of the four galaxy groups was consistent with or smaller than those of clusters of galaxies. The Mg/Fe and Si/Fe ratios in the ICM are nearly constant at the solar ratio out to 0.5 r 180. We also studied systematic uncertainties in the derived metal abundances, comparing the results from two versions of atomic data for astrophysicists (ATOMDB) and single- and two-temperature model fits. Since the metals have been synthesized in galaxies, we collected K-band luminosities of galaxies from the Two Micron All Sky Survey catalog and calculated the integrated iron-mass-to-light-ratios (IMLR), or the ratios of the iron mass in the ICM to light from stars in galaxies. The groups with smaller gas-mass-to-light ratios have smaller IMLR values and the IMLR is inversely correlated with the entropy excess. Based on these abundance features, we discussed the past history of metal enrichment processes in groups of galaxies.

  12. A nearby GRB host galaxy: VLT/X-shooter observations of HG 031203

    NASA Astrophysics Data System (ADS)

    Guseva, N. G.; Izotov, Y. I.; Fricke, K. J.; Henkel, C.

    2011-10-01

    Context. Long-duration gamma-ray bursts (LGRBs), which release enormous amounts of energy into the interstellar medium, occur in galaxies of generally low metallicity. For a better understanding of this phenomenon, detailed observations of the specific properties of the host galaxies (HG) and the environment near the LGRBs are mandatory. Aims: We aim at a spectroscopic analysis of HG 031203, the host galaxy of a LRGB burst, to obtain its properties. Our results will be compared with those of previous studies and the properties of a sample of luminous compact emission-line galaxies (LCGs) selected from SDSS DR7. Methods: Based on VLT/X-shooter spectroscopic observations taken from commissioning mode in the wavelength range ~λλ3200-24 000 Å, we use standard direct methods to evaluate physical conditions and element abundances. The resolving power of the instrument also allowed us to trace the kinematics of the ionised gas. Furthermore, we use X-shooter data together with Spitzer observations in the mid-infrared range for testing hidden star formation. Results: We derive an interstellar oxygen abundance of 12 + log O/H = 8.20 ± 0.03 for HG 031203. The observed fluxes of hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value C(Hβ) = 1.67. We produce the CLOUDY photoionisation H ii region model that reproduces observed emission-line fluxes of different ions in the optical range. This model also predicts emission-line fluxes in the near-infrared (NIR) and mid-infrared (MIR) ranges that agree well with the observed ones. This implies that the star-forming region observed in the optical range is the only source of ionisation and there is no additional source of ionisation seen in the NIR and MIR ranges that is hidden in the optical range. We find the composite kinematic structure from profiles of the strong emission lines by decomposing them into two Gaussian narrow and broad components. These components

  13. HST WFC3 Early Release Science: Emission-Line Galaxies from IR Grism Observations

    NASA Technical Reports Server (NTRS)

    Straughn, A. N.; Kuntschner, H.; Kuemmel, M.; Walsh, J. R.; Cohen, S. H.; Gardner, J. P.; Windhorst, R. A.; O'Connell, R. W.; Pirzkal, N.; Meurer, G.; hide

    2010-01-01

    We present grism spectra of emission line galaxies (ELGs) from 0.6-1.6 microns from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). These new infrared grism data augment previous optical Advanced Camera for Surveys G800L (0.6-0.95 micron) grism data in GOODS South, extending the wavelength coverage well past the G800L red cutoff. The ERS grism field was observed at a depth of 2 orbits per grism, yielding spectra of hundreds of faint objects, a subset of which are presented here. ELGs are studied via the Ha, [O III ], and [OII] emission lines detected in the redshift ranges 0.2 less than or equal to z less than or equal to 1.6, 1.2 less than or equal to z less than or equal to 2.4 and 2.0 less than or equal to z less than or equal to 3.6 respectively in the G102 (0.8-1.1 microns; R approximately 210) and C141 (1.1-1.6 microns; R approximately 130) grisms. The higher spectral resolution afforded by the WFC3 grisms also reveals emission lines not detectable with the G800L grism (e.g., [S II] and [S III] lines). From these relatively shallow observations, line luminosities, star formation rates, and grism spectroscopic redshifts are determined for a total of 25 ELGs to M(sub AB)(F098M) approximately 25 mag. The faintest source in our sample with a strong but unidentified emission line--is MAB(F098M)=26.9 mag. We also detect the expected trend of lower specific star formation rates for the highest mass galaxies in the sample, indicative of downsizing and discovered previously from large surveys. These results demonstrate the remarkable efficiency and capability of the WFC3 NIR grisms for measuring galaxy properties to faint magnitudes.

  14. Multifrequency radio continuum observations of head-tail galaxies in the Perseus cluster

    NASA Astrophysics Data System (ADS)

    Sijbring, D.; de Bruyn, A. G.

    1998-03-01

    New observations of head-tail radio galaxies in the Perseus cluster at 21, 49 and 92 cm using the WSRT are presented. Two new head-tail galaxies were discovered bringing the total for the cluster to five. We show total intensity maps for all of them and spectral index distribution and polarization maps for NGC 1265 and IC 310. The observations with high dynamic range, obtained with the WSRT and the redundancy and self-calibration techniques, reveal a large extension of the tail of NGC 1265 both at 49 cm and at 92 cm. The projected tail bends over an angle of almost 360°. There are several clear differences between the bright and the faint part of the radio tail: within a distance of one or two resolution beams the intensity decreases by more than an order of magnitude and the spectral index steepens from -1 to -2. The simplest model for the tail is that it delineates the orbit of the galaxy through the cluster. Because the tail is seen in projection, the faint part of the tail is visible only when it is not superimposed onto the bright part of the tail. It is likely, however, that large scale motions of the hot intracluster medium also help shape the tail. In this respect it is interesting to note that the tails of both NGC 1265 and IC 310, as well as the low brightness emission of NGC 1275 appear to have their faint extensions shifted to the east. The very long tail of NGC 1265 makes it possible to test at low frequencies models of the ageing process of the radiating electrons. In the faint part of the tail the brightness temperature is very low, which either indicates a very weak magnetic field or a large deviation from equipartition between particle and magnetic energy. The most remarkable properties of the faint part of the tail of NGC1265, namely its constant surface brightness and spectral index, are compared with three synchrotron ageing models, making some standard assumptions. All these models disagree with either the data or one of the assumptions. The

  15. Galaxy formation in the Planck cosmology - I. Matching the observed evolution of star formation rates, colours and stellar masses

    NASA Astrophysics Data System (ADS)

    Henriques, Bruno M. B.; White, Simon D. M.; Thomas, Peter A.; Angulo, Raul; Guo, Qi; Lemson, Gerard; Springel, Volker; Overzier, Roderik

    2015-08-01

    We have updated the Munich galaxy formation model to the Planck first-year cosmology, while modifying the treatment of baryonic processes to reproduce recent data on the abundance and passive fractions of galaxies from z = 3 down to z = 0. Matching these more extensive and more precise observational results requires us to delay the reincorporation of wind ejecta, to lower the surface density threshold for turning cold gas into stars, to eliminate ram-pressure stripping in haloes less massive than {˜ }10^{14}{ M_{⊙}}, and to modify our model for radio mode feedback. These changes cure the most obvious failings of our previous models, namely the overly early formation of low-mass galaxies and the overly large fraction of them that are passive at late times. The new model is calibrated to reproduce the observed evolution both of the stellar mass function and of the distribution of star formation rate at each stellar mass. Massive galaxies (log M⋆/M⊙ ≥ 11.0) assemble most of their mass before z = 1 and are predominantly old and passive at z = 0, while lower mass galaxies assemble later and, for log M⋆/M⊙ ≤ 9.5, are still predominantly blue and star forming at z = 0. This phenomenological but physically based model allows the observations to be interpreted in terms of the efficiency of the various processes that control the formation and evolution of galaxies as a function of their stellar mass, gas content, environment and time.

  16. Dissecting High-Redshift Galaxies with GRBs: Three Hosts at z 6 Observed with HST

    NASA Astrophysics Data System (ADS)

    McGuire, J. T. W.

    2016-10-01

    The first detection of three GRB hosts at z 6 is presented, along with their comparison to Lyman-break galaxies, potential star formation histories and a brief look at their impact on the high-redshift galaxy luminosity function.

  17. Investigating the thermal and nonthermal properties of galaxy clusters with radio observations

    NASA Astrophysics Data System (ADS)

    Farnsworth, Damon Patrick

    This thesis presents my recent investigations of the tenuous intracluster medium (ICM) in galaxy clusters using radio observations. The ICM is composed primarily of thermal and nonthermal plasma populations, permeated by magnetic fields which influence their evolution. Radio observations provide unique probes of the properties of the ICM, allowing for estimation of particle densities, magnetic field strengths, and even yielding clues to the physical mechanisms of particle acceleration. A major theme of this dissertation is that faint diffuse radio emission may contribute a significant amount of the synchrotron luminosity in galaxy clusters, yet goes unobserved due to an underappreciated deficiency of interferometric radio telescopes. Some of the current physical models do not account for this low surface brightness synchrotron emission, which may hold the key to distinguishing between competing models of relativistic particle acceleration and magnetic field amplification in these low density environments. I first discuss the use of polarization observations to probe magnetized plasmas, exploring various methods of Faraday rotation measure determination. I demonstrate that methods such as traditional fitting of models to polarization angle only (without consideration of the fractional polarization) or the novel Rotation Measure Synthesis may yield erroneous results in the presence of complex Faraday structure. The best way to more accurately recover the true Faraday structure is by fitting models directly to the observables Q and U, using radio polarization observations of the southern lobe of the radio galaxy 3C33 as an example. Next I exhibit results from a 1.4~GHz GBT study of twelve merging galaxy clusters. After subtraction of confusion from Galactic foreground and extragalactic background radio sources, eleven of the twelve clusters exhibited a significant excess of diffuse emission over that found by previous interferometric studies. Faint large-scale radio

  18. Chemical evolution of dwarf spheroidal galaxies based on model calculations incorporating observed star formation histories

    NASA Astrophysics Data System (ADS)

    Homma, H.; Murayama, T.

    We investigate the chemical evolution model explaining the chemical composition and the star formation histories (SFHs) simultaneously for the dwarf spheroidal galaxies (dSphs). Recently, wide imaging photometry and multi-object spectroscopy give us a large number of data. Therefore, we start to develop the chemical evolution model based on an SFH given by photometric observations and estimates a metallicity distribution function (MDF) comparing with spectroscopic observations. With this new model we calculate the chemical evolution for 4 dSphs (Fornax, Sculptor, Leo II, Sextans), and then we found that the model of 0.1 Gyr for the delay time of type Ia SNe is too short to explain the observed [alpha /Fe] vs. [Fe/H] diagrams.

  19. A CHANDRA OBSERVATION OF THE NEARBY SCULPTOR GROUP Sd GALAXY NGC 7793

    SciTech Connect

    Pannuti, Thomas G.; Staggs, Wayne D.; Schlegel, Eric M.; Filipovic, Miroslav D.; Payne, Jeffrey L.; Petre, Robert

    2011-07-15

    We conducted a Chandra ACIS observation of the nearby Sculptor Group Sd galaxy NGC 7793 as part of a multiwavelength study of supernova remnants (SNRs) in nearby galaxies. At the assumed distance to NGC 7793 of 3.91 Mpc, the limiting unabsorbed luminosity of the detected discrete X-ray sources is L{sub X} (0.2-10.0 keV) {approx}3x10{sup 36} erg s{sup -1}. A total of 22 discrete sources were detected at the {approx}3{sigma} level or greater including one ultraluminous X-ray source (ULX). Based on multiwavelength comparisons, we identify X-ray sources coincident with one SNR, the candidate microquasar N7793-S26, one H II region, and two foreground Galactic stars. We also find that the X-ray counterpart to the candidate radio SNR R3 is time variable in its X-ray emission: we therefore rule out the possibility that this source is a single SNR. A marked asymmetry is seen in the distribution of the discrete sources with the majority lying in the eastern half of this galaxy. All of the sources were analyzed using quantiles to estimate spectral properties and spectra of the four brightest sources (including the ULX) were extracted and analyzed. We searched for time variability in the X-ray emission of the detected discrete sources using our measured fluxes along with fluxes measured from prior Einstein and Roentgensatellit observations. From this study, three discrete X-ray sources are established to be significantly variable. A spectral analysis of the galaxy's diffuse emission is characterized by a temperature of kT = 0.19-0.25 keV. The luminosity function of the discrete sources shows a slope with an absolute value of {Gamma} = -0.65 {+-} 0.11 if we exclude the ULX. If the ULX is included, the luminosity function has a long tail to high L{sub X} with a poor-fitting slope of {Gamma} = -0.62 {+-} 0.2. The ULX-less slope is comparable to the slopes measured for the distributions of NGC 6946 and NGC 2403 but much shallower than the slopes measured for the distributions of

  20. Herschel photometric observations of the low metallicity dwarf galaxy NGC 1705

    NASA Astrophysics Data System (ADS)

    O'Halloran, B.; Galametz, M.; Madden, S. C.; Auld, R.; Baes, M.; Barlow, M. J.; Bendo, G. J.; Bock, J. J.; Boselli, A.; Bradford, M.; Buat, V.; Castro-Rodriguez, N.; Chanial, P.; Charlot, S.; Ciesla, L.; Clements, D. L.; Cormier, D.; Cooray, A.; Cortese, L.; Davies, J. I.; Dwek, E.; Eales, S. A.; Elbaz, D.; Galliano, F.; Gear, W. K.; Glenn, J.; Gomez, H. L.; Hony, S.; Isaak, K. G.; Levenson, L. R.; Lu, N.; Okumura, K.; Oliver, S.; Page, M. J.; Panuzzo, P.; Papageorgiou, A.; Parkin, T. J.; Perez-Fournon, I.; Pohlen, M.; Rangwala, N.; Rigby, E. E.; Roussel, H.; Rykala, A.; Sacchi, N.; Sauvage, M.; Schulz, B.; Schirm, M. R. P.; Smith, M. W. L.; Spinoglio, L.; Srinivasan, S.; Stevens, J. A.; Symeonidis, M.; Trichas, M.; Vaccari, M.; Vigroux, L.; Wilson, C. D.; Wozniak, H.; Wright, G. S.; Zeilinger, W. W.

    2010-07-01

    We present Herschel SPIRE and PACS photometeric observations of the low metallicity (Z ~ 0.35 Z⊙) nearby dwarf galaxy, NGC 1705, in six wavelength bands as part of the Dwarf Galaxy Survey guaranteed time Herschel key program. We confirm the presence of two dominant circumnuclear IR-bright regions surrounding the central super star cluster that had been previously noted at mid-IR wavelengths and in the sub-mm by LABOCA. On constructing a global spectral energy distribution using the SPIRE and PACS photometry, in conjunction with archival IR measurements, we note the presence of an excess at sub-mm wavelengths. This excess suggests the presence of a signiPcant cold dust component within NGC 1705 and was modeled as an additional cold component in the SED. Although alternative explanations for the sub-mm excess beyond 350 μm, such as changes to the dust emissivity cannot be ruled out, the most likely explanation for the observed submillimetre excess is that of an additional cold dust component.

  1. Why are so many primitive stars observed in the Galaxy halo

    NASA Astrophysics Data System (ADS)

    Gibson, Carl H.; Nieuwenhuizen, Theo M.; Schild, Rudolph E.

    2013-03-01

    Small values of lithium observed in a small, primitive, Galaxy-Halo star SDSS J102915 + 172927 cannot be explained using the standard cold dark matter CDM theory of star formation, but are easily understood using the Gibson/Schild 1996 hydrogravitational- dynamics (HGD) theory. From HGD, primordial H-4He gas fragments into Earth-mass planets in trillion-planet proto-globular-star-cluster (PGC) clumps at the 300 Kyr time of transition from the plasma epoch, soon after the big bang. The first HGD stars formed from pristine, frictionally-merging, gas-planets within the gently stressed clumps of the early universe, burning most available lithium in brown-dwarfs and hot-stars before creating metals that permit cooler burning. The Caffau halo star is a present day example. CDM first stars (Population III) were massive and promptly exploded, re- ionizing the gas of the universe and seeding it with metals, thus making the observed star unexplainable. From HGD, CDM and its massive first stars, and re-ionization by Pop III supernovae, never happened. All stars are formed from planets in primordial clumps. HGD first stars (Pop III) were small and long-lived, and the largest ones were hot. We suggest such small HGD (Pop III) stars still form in the gently stressed Galaxy halo.

  2. An x-ray study of luminous infrared galaxies observed with ASCA

    NASA Astrophysics Data System (ADS)

    Misaki, K.; Iwasawa, K.; Taniguchi, Y.; Terashima, Y.; Kunieda, H.; Watarai, H.

    The discovery of ultra-luminous infrared galaxies (ULIRGs) has provided a clue to an evolutionary connection between starburst and active galactic nuclei. The IRAS color is suggested to be a possible trace of the evolution. We present the results of ASCA observations of two ULIRGs, IRAS20551-4250 and IRAS23128-5919, which are southern 100 μm bright galaxies with LIR ~ 1012Lsolar. Both are mergers and have a ``warm'' IRAS color (25μm100μm >= 0.15). The ASCA spectrum of IRAS20551-4250 can be characterized by two components, one of which is a soft thermal component (kT ~ 0.3keV) and the other is a hard power-law component absorbed by a column density of 1022 cm-2. The observed X-ray luminosity is ~ 2.5 × 1042 ergs/s in the rest frame 2-10keV band (assuming H0 = 50 km/s/Mpc). IRAS23128-5919 also shows a hard spectrum (LX ~ 3 × 1042 ergs/s), but thermal emission is not as clear as that in IRAS20551-4250. Since these targets are similar in infrared luminosity as well as in hard X-rays but not in soft X-rays, LIR would be associated with hard X-rays. In addition to these results, we here compare X-ray properties of ULIRGs with IR properties.

  3. The Bright and Dark Sides of High-redshift Starburst Galaxies from Herschel and Subaru Observations

    NASA Astrophysics Data System (ADS)

    Puglisi, A.; Daddi, E.; Renzini, A.; Rodighiero, G.; Silverman, J. D.; Kashino, D.; Rodríguez-Muñoz, L.; Mancini, C.; Mainieri, V.; Man, A.; Franceschini, A.; Valentino, F.; Calabrò, A.; Jin, S.; Darvish, B.; Maier, C.; Kartaltepe, J. S.; Sanders, D. B.

    2017-04-01

    We present rest-frame optical spectra from the FMOS-COSMOS survey of 12 z ∼ 1.6 Herschel starburst galaxies, with star formation rate (SFR) elevated by ×8, on average, above the star-forming main sequence (MS). Comparing the Hα to IR luminosity ratio and the Balmer decrement, we find that the optically thin regions of the sources contain on average only ∼10% of the total SFR, whereas ∼90% come from an extremely obscured component that is revealed only by far-IR observations and is optically thick even in Hα. We measure the [N ii]6583/Hα ratio, suggesting that the less obscured regions have a metal content similar to that of the MS population at the same stellar masses and redshifts. However, our objects appear to be metal-rich outliers from the metallicity–SFR anticorrelation observed at fixed stellar mass for the MS population. The [S ii]6732/[S ii]6717 ratio from the average spectrum indicates an electron density n e ∼ 1100 cm‑3 , larger than what was estimated for MS galaxies but only at the 1.5σ level. Our results provide supporting evidence that high-z MS outliers are analogous of local ULIRGs and are consistent with a major-merger origin for the starburst event.

  4. Observational evidence for the accretion-disk origin for a radio jet in an active galaxy.

    PubMed

    Marscher, Alan P; Jorstad, Svetlana G; Gómez, José-Luis; Aller, Margo F; Teräsranta, Harri; Lister, Matthew L; Stirling, Alastair M

    2002-06-06

    Accretion of gas onto black holes is thought to power the relativistic jets of material ejected from active galactic nuclei (AGN) and the 'microquasars' located in our Galaxy. In microquasars, superluminal radio-emitting features appear and propagate along the jet shortly after sudden decreases in the X-ray fluxes. This establishes a direct observational link between the black hole and the jet: the X-ray dip is probably caused by the disappearance of a section of the inner accretion disk as it falls past the event horizon, while the remainder of the disk section is ejected into the jet, creating the appearance of a superluminal bright spot. No such connection has hitherto been established for AGN, because of insufficient multi-frequency data. Here we report the results of three years of monitoring the X-ray and radio emission of the galaxy 3C120. As has been observed for microquasars, we find that dips in the X-ray emission are followed by ejections of bright superluminal knots in the radio jet. The mean time between X-ray dips appears to scale roughly with the mass of the black hole, although there are at present only a few data points.

  5. Observational evidence that positive and negative AGN feedback depends on galaxy mass and jet power

    NASA Astrophysics Data System (ADS)

    Kalfountzou, E.; Stevens, J. A.; Jarvis, M. J.; Hardcastle, M. J.; Wilner, D.; Elvis, M.; Page, M. J.; Trichas, M.; Smith, D. J. B.

    2017-10-01

    Several studies support the existence of a link between the active galactic nucleus (AGN) and star formation activity. Radio jets have been argued to be an ideal mechanism for direct interaction between the AGN and the host galaxy. A drawback of previous surveys of AGN is that they are fundamentally limited by the degeneracy between redshift and luminosity in flux-density limited samples. To overcome this limitation, we present far-infrared Herschel observations of 74 radio-loud quasars (RLQs), 72 radio-quiet quasars (RQQs) and 27 radio galaxies (RGs), selected at 0.9 < z < 1.1, which span over two decades in optical luminosity. By decoupling luminosity from evolutionary effects, we investigate how the star formation rate (SFR) depends on AGN luminosity, radio-loudness and orientation. We find that (1) the SFR shows a weak correlation with the bolometric luminosity for all AGN sub-samples, (2) the RLQs show an SFR excess of about a factor of 1.4 compared to the RQQs, matched in terms of black hole mass and bolometric luminosity, suggesting that either positive radio-jet feedback or radio AGN triggering is linked to star formation triggering, and (3) RGs have lower SFRs by a factor of 2.5 than the RLQ sub-sample with the same BH mass and bolometric luminosity. We suggest that there is some jet power threshold at which radio-jet feedback switches from enhancing star formation (by compressing gas) to suppressing it (by ejecting gas). This threshold depends on both galaxy mass and jet power.

  6. NuSTAR Observations of the Powerful Radio Galaxy Cygnus A

    NASA Astrophysics Data System (ADS)

    Reynolds, Christopher S.; Lohfink, Anne M.; Ogle, Patrick M.; Harrison, Fiona A.; Madsen, Kristin K.; Fabian, Andrew C.; Wik, Daniel R.; Madejski, Grzegorz; Ballantyne, David R.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Fuerst, Felix; Hailey, Charles J.; Lanz, Lauranne; Miller, Jon M.; Saez, Cristian; Stern, Daniel; Walton, Dominic J.; Zhang, William

    2015-08-01

    We present NuSTAR observations of the powerful radio galaxy Cygnus A, focusing on the central absorbed active galactic nucleus (AGN). Cygnus A is embedded in a cool-core galaxy cluster, and hence we also examine archival XMM-Newton data to facilitate the decomposition of the spectrum into the AGN and intracluster medium components. NuSTAR gives a source-dominated spectrum of the AGN out to \\gt 70 keV. In gross terms, the NuSTAR spectrum of the AGN has the form of a power law ({{Γ }}∼ 1.6-1.7) absorbed by a neutral column density of {N}{{H}}∼ 1.6× {10}23 {{cm}}-2. However, we also detect curvature in the hard (\\gt 10 keV) spectrum resulting from reflection by Compton-thick matter out of our line of sight to the X-ray source. Compton reflection, possibly from the outer accretion disk or obscuring torus, is required even permitting a high-energy cut off in the continuum source; the limit on the cut-off energy is {E}{cut}\\gt 111 keV(90% confidence). Interestingly, the absorbed power law plus reflection model leaves residuals suggesting the absorption/emission from a fast (15,000-26,000 {km} {{{s}}}-1 ), high column-density ({N}W\\gt 3× {10}23 {{cm}}-2), highly ionized (ξ ∼ 2500 {erg} {cm} {{{s}}}-1) wind. A second, even faster ionized wind component is also suggested by these data. We show that the ionized wind likely carries a significant mass and momentum flux, and may carry sufficient kinetic energy to exercise feedback on the host galaxy. If confirmed, the simultaneous presence of a strong wind and powerful jets in Cygnus A demonstrates that feedback from radio-jets and sub-relativistic winds are not mutually exclusive phases of AGN activity but can occur simultaneously.

  7. Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope

    SciTech Connect

    Ackermann, M.; et al.

    2014-02-11

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma-ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma-ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical Standard Model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma-ray background modeling, and assumed dark matter density profile.

  8. Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope

    SciTech Connect

    Ackermann, M.; Albert, A.; Anderson, B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; D’Ammando, F.; de Angelis, A.; Dermer, C. D.; Digel, S. W.; do Couto e Silva, E.; Drell, P. S.; Drlica-Wagner, A.; Essig, R.; Favuzzi, C.; Ferrara, E. C.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giroletti, M.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Hayashida, M.; Hays, E.; Hewitt, J.; Hughes, R. E.; Jogler, T.; Kamae, T.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Larsson, S.; Latronico, L.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Martinez, G.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohsugi, T.; Orlando, E.; Ormes, J. F.; Perkins, J. S.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Sánchez-Conde, M.; Sehgal, N.; Sgrò, C.; Siskind, E. J.; Spinelli, P.; Strigari, L.; Suson, D. J.; Tajima, H.; Takahashi, H.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vianello, G.; Vitale, V.; Werner, M.; Winer, B. L.; Wood, K. S.; Wood, M.; Zaharijas, G.; Zimmer, S.

    2014-02-11

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via γ rays. We report on γ -ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in γ rays, and we present γ -ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. Furthermore, we set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical standard model channels. We also find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse γ -ray background modeling, and assumed dark matter density profile.

  9. Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope

    DOE PAGES

    Ackermann, M.; Albert, A.; Anderson, B.; ...

    2014-02-11

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via γ rays. We report on γ -ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in γ rays, and we present γ -ray flux upper limits between 500 MeVmore » and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. Furthermore, we set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical standard model channels. We also find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse γ -ray background modeling, and assumed dark matter density profile.« less

  10. Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Albert, A.; Anderson, B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; hide

    2013-01-01

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma ray flux upper limits between 500MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10TeV into prototypical standard model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma ray background modeling, and assumed dark matter density profile.

  11. Redshift evolution of stellar mass versus gas fraction relation in 0 < z < 2 regime: observational constraint for galaxy formation models

    NASA Astrophysics Data System (ADS)

    Morokuma-Matsui, Kana; Baba, Junichi

    2015-12-01

    We investigate the redshift evolution of molecular gas mass fraction (f_mol = M_mol/M_star +M_mol, where Mmol is molecular gas mass and M⋆ is stellar mass) of galaxies in the redshift range of 0 < z < 2 as a function of the stellar mass by combining carbon monoxide (CO) literature data. We observe a stellar-mass dependence of the fmol evolution where massive galaxies have largely depleted their molecular gas at z = 1, whereas the fmol value of less massive galaxies drastically decreases from z = 1. We compare the observed M⋆ - fmol relation with theoretical predictions from cosmological hydrodynamic simulations and semi-analytical models for galaxy formation. Although the theoretical studies approximately reproduce the observed mass dependence of the fmol evolution, they tend to underestimate the fmol values, particularly of less massive (<1010 M⊙) and massive galaxies (>1011 M⊙) when compared with the observational values. Our result suggests the importance of the feedback models which suppress the star formation while simultaneously preserving the molecular gas in order to reproduce the observed M⋆ - fmol relation.

  12. COMPARATIVE STUDY OF ASYMMETRY ORIGIN OF GALAXIES IN DIFFERENT ENVIRONMENTS. II. NEAR-INFRARED OBSERVATIONS

    SciTech Connect

    Plauchu-Frayn, I.; Coziol, R. E-mail: rcoziol@astro.ugto.m

    2010-08-15

    In this second paper of two analyses, we present near-infrared (NIR) morphological and asymmetry studies performed in a sample of 92 galaxies found in different density environments: galaxies in compact groups (CGs; HCGs in the Hickson Catalog of Compact Groups of Galaxies), isolated pairs of galaxies (KPGs in Karachentsev's list of isolated pairs of galaxies), and isolated galaxies (KIGs in Karachentseva's Catalog of Isolated Galaxies). Both studies have proved useful for identifying the effect of interactions on galaxies. In the NIR, the properties of the galaxies in HCGs, KPGs, and KIGs are more similar than they are in the optical. This is because the NIR band traces the older stellar populations, which formed earlier and are more relaxed than the younger populations. However, we found asymmetries related to interactions in both KPG and HCG samples. In HCGs, the fraction of asymmetric galaxies is even higher than what we found in the optical. In the KPGs the interactions look like very recent events, while in the HCGs galaxies are more morphologically evolved and show properties suggesting they suffered more frequent interactions. The key difference seems to be the absence of star formation in the HCGs; while interactions produce intense star formation in the KPGs, we do not see this effect in the HCGs. This is consistent with the dry merger hypothesis; the interaction between galaxies in CGs is happening without the presence of gas. If the gas was spent in stellar formation (to build the bulge of the numerous early-type galaxies), then the HCGs possibly started interacting sometime before the KPGs. On the other hand, the dry interaction condition in CGs suggests that the galaxies are on merging orbits, and consequently such system cannot be that much older either. Cosmologically speaking, the difference in formation time between pairs of galaxies and CGs may be relatively small. The two phenomena are typical of the formation of structures in low

  13. The Spatial Distribution of Star Formation in Galaxies: Observing the Emergence of Galactic Structure

    NASA Astrophysics Data System (ADS)

    Nelson, Erica June

    A high resolution measurement of the distribution of star formation within galaxies is key to understanding the emergence of galactic structure. The aim of this thesis is to understand how the structure of galaxies is built by developing a new method to spatially resolve their star formation. Using Ha maps for 2676 galaxies, this thesis shows where star formation is distributed in galaxies during the epoch 0.7 < z < 1.5 when a third of the total star formation in the history of the universe occurred. Across the star formation rate - stellar mass plane (the "main sequence"), star formation is `spatially coherent': in galaxies with higher than average star formation rates, Ha is enhanced throughout the disk; similarly, in galaxies with low star formation rates Ha is depressed throughout the disk. This places constraints both on the mechanisms for enhancing and quenching star formation as well as on how the structure of galaxies is built. The disk scale length of star formation in galaxies is larger than that of the stars, a direct demonstration that the disks of galaxies grow inside-out. While most star formation in most galaxies occurs in disks, not all of it does. With the first spatially resolved measurement of the Balmer decrement at z > 1, it can be seen that galaxies with M* > 1010M ⊙ have significant dust attenuation toward their centers. This means that we are witnessing the build-up of the dense stellar cores of massive galaxies through dust-obscured in-situ star formation. The most massive galaxies are thought to have formed their dense stellar cores at even earlier cosmic epochs. This thesis presents the first confirmed example of a massive galaxy core in the process of formation at z = 2.3. It has one of the highest velocity dispersions ever measured for a normal star forming galaxy and also appears to be building through very dense, dust-enshrouded star formation.

  14. Deep MUSE observations in the HDFS. Morpho-kinematics of distant star-forming galaxies down to 108M⊙

    NASA Astrophysics Data System (ADS)

    Contini, T.; Epinat, B.; Bouché, N.; Brinchmann, J.; Boogaard, L. A.; Ventou, E.; Bacon, R.; Richard, J.; Weilbacher, P. M.; Wisotzki, L.; Krajnović, D.; Vielfaure, J.-B.; Emsellem, E.; Finley, H.; Inami, H.; Schaye, J.; Swinbank, M.; Guérou, A.; Martinsson, T.; Michel-Dansac, L.; Schroetter, I.; Shirazi, M.; Soucail, G.

    2016-06-01

    Aims: Whereas the evolution of gas kinematics of massive galaxies is now relatively well established up to redshift z ~ 3, little is known about the kinematics of lower mass (M⋆≤ 1010M⊙) galaxies. We use MUSE, a powerful wide-field, optical integral-field spectrograph (IFS) recently mounted on the VLT, to characterize this galaxy population at intermediate redshift. Methods: We made use of the deepest MUSE observations performed so far on the Hubble Deep Field South (HDFS). This data cube, resulting from 27 h of integration time, covers a one arcmin2 field of view at an unprecedented depth (with a 1σ emission-line surface brightness limit of 1 × 10-19 erg s-1 cm-2 arcsec-2) and a final spatial resolution of ≈0.7''. We identified a sample of 28 resolved emission-line galaxies, extending over an area that is at least twice the seeing disk, spread over a redshift interval of 0.2 galaxies are at z ~ 0.3 - 0.7, which is a redshift range poorly studied so far with IFS kinematics. We used the public HST images and multiband photometry over the HDFS to constrain the stellar mass and star formation rate (SFR) of the galaxies and to perform a morphological analysis using Galfit, providing estimates of the disk inclination, disk scale length, and position angle of the major axis. We derived the resolved ionized gas properties of these galaxies from the MUSE data and model the disk (both in 2D and in 3D with GalPaK3D) to retrieve their intrinsic gas kinematics, including the maximum rotation velocity and velocity dispersion. Results: We build a sample of resolved emission-line galaxies of much lower stellar mass and SFR (by ~1 - 2 orders of magnitude) than previous IFS surveys. The gas kinematics of most of the spatially resolved MUSE-HDFS galaxies is consistent with disk-like rotation, but about 20% have velocity dispersions that are larger than the rotation velocities and 30% are part of a close pair and/or show clear signs of recent

  15. LOCAL LUMINOUS INFRARED GALAXIES. I. SPATIALLY RESOLVED OBSERVATIONS WITH THE SPITZER INFRARED SPECTROGRAPH

    SciTech Connect

    Pereira-Santaella, Miguel; Alonso-Herrero, Almudena; Colina, Luis; Diaz-Santos, Tanio; Rieke, George H.; Engelbracht, Charles W.; Smith, J.-D. T.; Perez-Gonzalez, Pablo G.

    2010-06-15

    We present results from the Spitzer Infrared Spectrograph spectral mapping observations of 15 local luminous infrared galaxies (LIRGs). In this paper, we investigate the spatial variations of the mid-IR emission which includes fine structure lines, molecular hydrogen lines, polycyclic aromatic features (PAHs), continuum emission, and the 9.7 {mu}m silicate feature. We also compare the nuclear and integrated spectra. We find that the star formation takes place in extended regions (several kpc) as probed by the PAH emission, as well as the [Ne II]12.81 {mu}m and [Ne III]15.56 {mu}m emissions. The behavior of the integrated PAH emission and 9.7 {mu}m silicate feature is similar to that of local starburst galaxies. We also find that the minima of the [Ne III]15.56 {mu}m/[Ne II]12.81 {mu}m ratio tends to be located at the nuclei and its value is lower than that of H II regions in our LIRGs and nearby galaxies. It is likely that increased densities in the nuclei of LIRGs are responsible for the smaller nuclear [Ne III]15.56 {mu}m/[Ne II]12.81 {mu}m ratios. This includes the possibility that some of the most massive stars in the nuclei are still embedded in ultracompact H II regions. In a large fraction of our sample, the 11.3 {mu}m PAH emission appears more extended than the dust 5.5 {mu}m continuum emission. We find a dependency of the 11.3 {mu}m PAH/7.7 {mu}m PAH and [Ne II]12.81 {mu}m/11.3 {mu}m PAH ratios with the age of the stellar populations. Smaller and larger ratios, respectively, indicate recent star formation. The estimated warm (300 K galaxies. Finally we find that the [Ne II]12.81 {mu}m velocity fields for most of the LIRGs in our sample are compatible with a rotating disk at {approx}kpc scales, and they are in a good agreement with H{alpha} velocity fields.

  16. ON THE ROAD TO MORE REALISTIC GALAXY CLUSTER SIMULATIONS: THE EFFECTS OF RADIATIVE COOLING AND THERMAL FEEDBACK PRESCRIPTIONS ON THE OBSERVATIONAL PROPERTIES OF SIMULATED GALAXY CLUSTERS

    SciTech Connect

    Skory, Stephen; Hallman, Eric; Burns, Jack O.; Skillman, Samuel W.; O'Shea, Brian W.; Smith, Britton D.

    2013-01-20

    Flux-limited X-ray surveys of galaxy clusters show that clusters come in two roughly equally proportioned varieties: 'cool core' clusters (CCs) and non-'cool core' clusters (NCCs). In previous work, we have demonstrated using cosmological N-body + Eulerian hydrodynamic simulations that NCCs are often consistent with early major merger events that destroy embryonic CCs. In this paper we extend those results and conduct a series of simulations using different methods of gas cooling and of energy and metal feedback from supernovae, where we attempt to produce a population of clusters with realistic central cooling times, entropies, and temperatures. We find that the use of metallicity-dependent gas cooling is essential to prevent early overcooling, and that adjusting the amount of energy and metal feedback can have a significant impact on observable X-ray quantities of the gas. We are able to produce clusters with more realistic central observable quantities than have previously been attained. However, there are still significant discrepancies between the simulated clusters and observations, which indicates that a different approach to simulating galaxies in clusters is needed. We conclude by looking toward a promising subgrid method of modeling galaxy feedback in clusters that may help to ameliorate the discrepancies between simulations and observations.

  17. EVN observations of the radio galaxy M87 following a TeV flare

    NASA Astrophysics Data System (ADS)

    Giroletti, M.; Giovannini, G.; Beilicke, M.; Cesarini, A.; Krawczynski, H.

    2010-02-01

    We report on EVN observations of the radio galaxy M87, taken at 5 GHz on 2010 Feb 10. Data were acquired by 7 radio telescopes from 21:40 UT on Feb 10 to 8:30 UT on Feb 11, directly streamed to the central data processor at JIVE, and correlated in real-time (eVLBI). This permits us to promptly report on the status of the radio jet of the source, following the increase in gamma ray emission above 100GeV reported by MAGIC (ATel #2431) The observations have an angular resolution of about 7 mas x 3 mas and rms noise of 0.12 mJy/beam.

  18. Observed galaxy number counts on the lightcone up to second order: II. Derivation

    SciTech Connect

    Bertacca, Daniele; Maartens, Roy; Clarkson, Chris E-mail: roy.maartens@gmail.com

    2014-11-01

    We present a detailed derivation of the observed galaxy number over-density on cosmological scales up to second order in perturbation theory. We include all relativistic effects that arise from observing on the past lightcone. The derivation is in a general gauge, and applies to all dark energy models (including interacting dark energy) and to metric theories of modified gravity. The result will be important for accurate cosmological parameter estimation, including non-Gaussianity, since all projection effects need to be taken into account. It also offers the potential for new probes of General Relativity, dark energy and modified gravity. This paper accompanies Paper I which presents the key results for the concordance model in Poisson gauge.

  19. Chandra Observations of the Evening Core of the Starburst Galaxy NGC 253

    NASA Technical Reports Server (NTRS)

    Weaver, K. A.; Heckman, T. M.; Dahlem, M.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    Chandra observations of the core of the nearby starburst galaxy NGC 253 reveal a heavily absorbed source of hard X-rays embedded within the nuclear starburst region. The source has an unabsorbed, 2 to 10 keV luminosity of greater than or equal to 10(exp 39) erg per s and photoionizes the surrounding gas. We observe this source through a dusty torus with a neutral absorbing column density of N(sub eta) approximately 2 x 10(exp 23)cm (exp -2). The torus is hundreds of pc across and collimates the starburst-driven nuclear outflow. We suggest that the ionizing source is an intermediate-mass black hole or a weakly accreting supermassive black hole, which may signal the beginnings or endings of AGN (active galactic nuclei) activity.

  20. Observational Manifestation of Chaos in the Gaseous Disk of the Grand Design Spiral Galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Khoruzhii, O. V.; Polyachenko, E. V.

    2002-10-01

    The main goal of the paper is to demonstrate the presence of chaotic trajectories in the gaseous disk of a real spiral galaxy. As an example we have chosen NGC 3631. First, we show the stationarity of the 3-D velocity field restored from the observed line-of-sight velocity field of the gaseous disk. That allows to analyse behaviour of the trajectories of the fluid particles (gas clouds) in the disk, calculating the corresponding observed streamlines. We estimate the Lyapunov characteristic numbers using their independence of the metrics and show the existence of chaotic trajectories outside the vortices which are present in the velocity field, and in the vicinity of the saddle point. Related spectra of the stretching numbers for some trajectories are also calculated.

  1. Radio and infrared observations of (almost) one hundred non-Seyfert Markarian galaxies

    NASA Technical Reports Server (NTRS)

    Dressel, Linda L.

    1987-01-01

    The 13 cm flux densities of 96 non-Seyfert Markarian galaxies were measured at Arecibo Observatory. Far infrared flux densities have been published for 78 of these galaxies in the IRAS catalog. The radio, infrared, and optical fluxes of these galaxies and of a magnitude limited sample of normal galaxies were compared to clarify the nature of the radio emission in Markarian galaxies. It was found that Markarian galaxies of a given apparent magnitude and Hubble type generally have radio fluxes several times higher that the fluxes typical of normal galaxies of the same magnitude and type. Remarkably, the ratio of radio flux to far infrared flux is nearly the same for most of these starburst galaxies and for normal spiral disks. However, the compact and peculiar Markarian galaxies consistently have about 60% more radio flux per unit infrared flux than the other Markarian galaxies and the normal spirals. It is not clear whether this difference reflects a difference in the evolution of the starbursts in these galaxies or whether there is excess radio emission of nonstellar origin.

  2. Hubble Space Telescope observations determine the age of some of the oldest stars in our Galaxy

    NASA Astrophysics Data System (ADS)

    1996-05-01

    Globular clusters like NGC 6752 are compact, spherically shaped collections of several hundred thousand stars which orbit our galaxy. Virtually all of the stars in these clusters began their lives at the time of the formation of our galaxy. Astronomers therefore believe that globular clusters contain the oldest sample of stars that we can easily study and that an accurate determination of the ages of such stars would also define the age of our own galaxy since its formation. The age of our galaxy, in turn, sets a firm lower limit on the age of the Universe. Obtaining accurate ages of stars in globular clusters has previously been hindered by the inability to determine accurate distances to these clusters. Using the Wide Field and Planetary Camera on the Hubble Space Telescope, a team of astronomers in Italy, the US and Canada obtained long exposure images of NGC 6752 in April 1995. These sharp images allowed them to detect and measure the brightness and color of a number of faint white dwarf stars in the cluster. With dwarfs are the condensed cores of stars that have reached the final stage of their lives as stars. They represent the stellar remains of the more massive stars in NGC 6752 which have completed their evolution. By comparing the apparent brightness and color of these stars with a sample of white dwarfs in the neighborhood of the Sun which have known distances, the team determined the distance to NGC 6752 to be 13,300 light years with an uncertainty of less than 5%. This distance provides an accurate measure of the luminosity of the brightest stars in NGC 67523 that are still burning hydrogen at their center. In turn, the knowledge of this luminosity allows to estimate the time elapsed since the formation of the stars in the cluster, hence the cluster age. This leads rather directly to an age of 15 billion years with a 10% uncertainty. Using current estimates of the time interval between the Big Bang and the era of galaxy formation gives 16-17 billion

  3. Recent Observations of Intrinsic UV Absorption Lines in Seyfert Galaxies with STIS

    NASA Astrophysics Data System (ADS)

    Crenshaw, D. M.; Kraemer, S. B.; Ruiz, J. R.

    2000-05-01

    We present recent observations of the intrinsic UV absorption lines in several Seyfert 1 galaxies with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). Echelle observations of NGC 4151 on 1999 June 19 indicate that the continuum and broad emission lines were at a low state at this time. Consequently, strong low-ionization absorption lines appear in the spectra, including numerous metastable Fe II lines. A feature in the blue wing of the C IV emission line, identified as a transient C IV absorption line at high outflow velocity by Weymann et al., turns out to be a fine-structure Si II line. Our current work focuses on determining the physical conditions in different kinematic components of the absorption using detailed photoionization models. Our STIS echelle observations of NGC 3783 on 2000 February 27 reveal that a new component of C IV and N V absorption has appeared since the last GHRS observation 5 years earlier, at a radial velocity of -800 km/sec relative to the systemic velocity. In addition, the component at -1400 km/sec has become much stronger and is present in Si IV, indicating a lower ionization state compared to the other components. We have also obtained low-resolution UV spectra of the Seyfert 1 galaxy NGC 3227, which is characterized by significant reddening of the continuum and emission lines. In addition to saturated absorption from high-ionization lines, we detect strong absorption in the Si IV and Mg II lines. This confirms our prediction that a lukewarm absorber that occults much of the narrow-line region is responsible for the reddening (Kraemer et al. 2000), rather than a large neutral column or a dusty X-ray absorber.

  4. RADIO GALAXY 3C 230 OBSERVED WITH GEMINI LASER ADAPTIVE-OPTICS INTEGRAL-FIELD SPECTROSCOPY

    SciTech Connect

    Steinbring, Eric

    2011-11-15

    The Altair laser-guide-star adaptive optics facility combined with the near-infrared integral-field spectrometer on Gemini North have been employed to study the morphology and kinematics of 3C 230 at z = 1.5, the first such observations of a high-redshift radio galaxy. These suggest a bi-polar outflow spanning 0.''9 ({approx}16 kpc projected distance for a standard {Lambda} CDM cosmology) reaching a mean relative velocity of 235 km s{sup -1} in redshifted H{alpha} +[N II] and [S II] emission. Structure is resolved to 0.''1 (0.8 kpc), which is well correlated with optical images from the Hubble Space Telescope and Very Large Array radio maps obtained at similar spatial resolution. Line diagnostics suggest that over the 10{sup 7} yr to 10{sup 8} yr duration of its active galactic nucleus activity, gas has been ejected into bright turbulent lobes at rates comparable to star formation, although constituting perhaps only 1% of the baryonic mass in the galaxy.

  5. The outer limits of galaxy clusters: Observations to the virial radius with Suzaku, XMM, and Chandra

    NASA Astrophysics Data System (ADS)

    Miller, Eric D.; Bautz, Marshall; George, Jithin; Mushotzky, Richard; Davis, David; Henry, J. Patrick

    2012-03-01

    The outskirts of galaxy clusters, near the virial radius, remain relatively unexplored territory and yet are vital to our understanding of cluster growth, structure, and mass. In this presentation, we show the first results from a program to constrain the state of the outer intra-cluster medium (ICM) in a large sample of galaxy clusters, exploiting the strengths of three complementary X-ray observatories: Suzaku (low, stable background), XMM-Newton (high sensitivity), and Chandra (good spatial resolution). By carefully combining observations from the cluster core to beyond r200, we are able to identify and reduce systematic uncertainties that would impede our spatial and spectral analysis using a single telescope. Our sample comprises nine clusters at z ~ 0.1-0.2 fully covered in azimuth to beyond r200, and our analysis indicates that the ICMis not in hydrostatic equilibrium in the cluster outskirts, where we see clear azimuthal variations in temperature and surface brightness. In one of the clusters, we are able to measure the diffuse X-ray emission well beyond r200, and we find that the entropy profile and the gas fraction are consistent with expectations from theory and numerical simulations. These results stands in contrast to recent studies which point to gas clumping in the outskirts; the extent to which differences of cluster environment or instrumental effects factor in this difference remains unclear. From a broader perspective, this project will produce a sizeable fiducial data set for detailed comparison with high-resolution numerical simulations.

  6. Mass-to-Light-Ratios of the galaxy clusters and groups observed with Suzaku

    NASA Astrophysics Data System (ADS)

    Sasaki, T.; Matsushita, K.; Sato, K.; Abe, Y.; Akamatsu, H.; Fujita, Y.; Kanno, Y.; Simionescu, A.; Tamura, T.; Werner, N.

    2016-06-01

    We analyzed 15 nearby (z < 0.06 ) clusters and groups observed with Suzaku out to ˜ 2 r_{500}. We derived Fe abundance profiles in the ICM, electron density, cumulative gas mass and Fe mass. We also collected K-band luminosities of galaxies and calculated the ratio of the cumulative gas mass and Fe mass in the ICM to the K-band luminosity (gas-mass-to-light ratio and iron-mass-to-light ratio, respectively). The Coma, Perseus, and medium systems have relatively flat radial profiles of the metal abundances at 0.3 solar within 0.5-1 r_{500}, and ˜ 0.2 solar beyond r_{500}. The gas-mass-to-light-ratios and iron-mass-to-light-ratios ratios increase with radius out to r_{500} and become flatter beyond the radius. The weighted average of the iron-mass-to-light ratios of the clusters at 1.6 r_{500} agrees with the expectation with the Salpeter initial-mass-function of stars, and we do not need a top-heavy slope. In contrast, groups and poor clusters have lower gas-mass-to-light ratios and lower iron-mass-to-light ratios than that of rich systems, with the higher entropy excess. Above these results, we discuss an early metal enrichment in galaxy clusters and groups.

  7. High Resolution Radio Observations Of Energetically Dominant Regions In Local Luminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Barcos-Munoz, Loreto

    2016-07-01

    Luminous and Ultra-luminous Infrared galaxies (U/LIRGs) are one of the most powerful classes of extragalactic objects in the local universe, and they provide a unique opportunity to study star formation and feedback processes in extreme environments. They are primarily observed to be interacting or merging disk galaxies. During the interaction, large amounts of gas are funneled to the central few kpc, triggering high star formation rates (SFR) and dust production. The absorption of UV and optical radiation from stars, or active galactic nuclei (AGN), by dust produces their observed high infrared luminosities.The high level of dust obscuration intrinsic to U/LIRGs makes them difficult to study. Radio interferometry is thus the perfect tool for revealing the nature of these systems - it provides the high spatial resolution needed to resolve energetically dominant regions in U/LIRGs at wavelengths that have both diagnostic power and transparency to dust. In this thesis, 6 and 33 GHz radio continuum interferometric observations with the upgraded Karl G. Jansky Very Large Array (VLA) are used to study a sample of 22 local U/LIRGs.First, a detailed analysis of the 6 and 33 GHz radio continuum emission from the closest ULIRG, Arp 220, is presented. This late stage merger is highly obscured, being optically thick even at mid-infrared wavelengths. Further, due to its extreme environment, it is often used as a template for high redshift starbursts. Arp 220 hosts two distinct nuclei that are separated by (\\sim) 370 pc. The nuclei are well resolved with the 33 GHz observations (i.e., with a spatial resolution of ˜ 30 pc). The deconvolved radii enclosing half of the total 33 GHz light are approximately 50 and 35 pc for the eastern and western nucleus, respectively. Literature values of the gas mass and infrared luminosity are combined with the 33 GHz sizes under the assumption of co-spatiality to show that Arp 220 has one of the highest molecular gas surface densities

  8. Hubble Space Telescope photometry of the central regions of Virgo Cluster elliptical galaxies. 1: Observations, discussion, and conclusions

    NASA Technical Reports Server (NTRS)

    Jaffe, Walter; Ford, Holland C.; O'Connell, Robert W.; Bosch, Frank C. Van Den; Ferrarese, Laura

    1994-01-01

    Using the Hubble Space Telescope we have observed at 10 pc resolution the nuclei of a luminosity-limited sample of 14 E and E/SO galaxies in the Virgo Cluster with magnitudes B(sub T) = 9.4 to 13.4. In this paper we present the images, and discuss the results of the detailed analysis of the surface photometry given in two companion papers. We find that the nuclear and near-nuclear morphologies confirm and strengthen the previously recognized dichotomy of 'E' galaxies into 'true' and 'disky' subtypes. The latter, usually classified E4 or later, often show a bright nuclear disk of radius approximately 100 pc. Essentially all early-type galaxies with -18 greater than M(sub B) greater than -20 are disky. Most true E galaxies are classified E4 or earlier. Most galaxies of both types show dust in the nuclear regions, the most remarkable example being a compact dust disk in NGC 4261. Other than dust, no anomalies were detected in the centers of the three galaxies in our sample which show clear kinematic evidence for a decoupled component.

  9. Hubble Space Telescope photometry of the central regions of Virgo Cluster elliptical galaxies. 1: Observations, discussion, and conclusions

    NASA Technical Reports Server (NTRS)

    Jaffe, Walter; Ford, Holland C.; O'Connell, Robert W.; Bosch, Frank C. Van Den; Ferrarese, Laura

    1994-01-01

    Using the Hubble Space Telescope we have observed at 10 pc resolution the nuclei of a luminosity-limited sample of 14 E and E/SO galaxies in the Virgo Cluster with magnitudes B(sub T) = 9.4 to 13.4. In this paper we present the images, and discuss the results of the detailed analysis of the surface photometry given in two companion papers. We find that the nuclear and near-nuclear morphologies confirm and strengthen the previously recognized dichotomy of 'E' galaxies into 'true' and 'disky' subtypes. The latter, usually classified E4 or later, often show a bright nuclear disk of radius approximately 100 pc. Essentially all early-type galaxies with -18 greater than M(sub B) greater than -20 are disky. Most true E galaxies are classified E4 or earlier. Most galaxies of both types show dust in the nuclear regions, the most remarkable example being a compact dust disk in NGC 4261. Other than dust, no anomalies were detected in the centers of the three galaxies in our sample which show clear kinematic evidence for a decoupled component.

  10. The Confirmation and Characterization of the Highest Redshift Galaxies: The Power of Complementary Observations by Keck, Spitzer and Hubble.

    NASA Astrophysics Data System (ADS)

    Illingworth, Garth D.

    2017-01-01

    Extraordinary numbers of high-redshift galaxies have been detected in deep Hubble imaging over the last ~20-yrs. While much is learned from the images, spectroscopy holds the key to both confirming their redshifts and to characterizing their astrophysical properties. The faintness of the galaxies requires our biggest telescopes and high-throughput instruments to do such spectroscopy, and many such combinations are now available on 8-10 m class telescopes. This talk will largely concentrate on Keck's role given the focus of this special session. Since the HDF in 1995 and the HUDF and GOODS in 2003-4, Keck and its powerful optical instruments such as LRIS and DEIMOS have played a major role in spectroscopic studies. With the advent of the WFC3/IR in 2009 and near-IR imaging of fields such as HUDF09, CANDELS and HUDF12 between 2009-and 2012, not only were greater insights for z~1-6 galaxies enabled, but whole new opportunities were opened up for the detection of large samples of galaxies in the first billion years at z>6. The recognition that Spitzer could measure galaxies in the IR well into the confusion-limited regime also resulted in much enhanced datasets on the most distant galaxies. Keck soon was positioned to take advantage of these new higher redshift sources with instruments such as MOSFIRE. The result was a series of detections of the highest redshift galaxies. I will discuss the role that Keck spectroscopy has played in pushing the spectroscopic frontiers for high-redshift galaxies and highlight the synergies that have resulted from Hubble, Spitzer and Keck observations.

  11. H I observations of two new dwarf galaxies: Pisces A and B with the SKA Pathfinder KAT-7

    NASA Astrophysics Data System (ADS)

    Carignan, C.; Libert, Y.; Lucero, D. M.; Randriamampandry, T. H.; Jarrett, T. H.; Oosterloo, T. A.; Tollerud, E. J.

    2016-03-01

    Context. Pisces A and Pisces B are the only two galaxies found via optical imaging and spectroscopy out of 22 Hi clouds identified in the GALFAHI survey as dwarf galaxy candidates. Aims: We derive the Hi content and kinematics of Pisces A and B. Methods: Our aperture synthesis Hi observations used the seven-dish Karoo Array Telescope (KAT-7), which is a pathfinder instrument for MeerKAT, the South African precursor to the mid-frequency Square Kilometre Array (SKA-MID). Results: The low rotation velocities of ~5 km s-1 and ~10 km s-1 in Pisces A and B, respectively, and their Hi content show that they are really dwarf irregular galaxies (dIrr). Despite that small rotation component, it is more the random motions ~9-11 km s-1 that provide most of the gravitational support, especially in the outer parts. The study of their kinematics, especially the strong gradients of random motions, suggest that those two dwarf galaxies are not yet in equilibrium. Conclusions: These Hi- rich galaxies may be indicative of a large population of dwarfs at the limit of detectability. However, such gas-rich dwarf galaxies will most likely never be within the virial radius of MW-type galaxies and become subhalo candidates. Systems such as Pisces A and B are more likely to be found at a few Mpc s from MW-type galaxies. The final FITS cube is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/L3

  12. A Chandra observation of the interacting pair of galaxies NGC 4485/4490

    NASA Astrophysics Data System (ADS)

    Roberts, T. P.; Warwick, R. S.; Ward, M. J.; Murray, S. S.

    2002-12-01

    We report the results of a 20-ks Chandra ACIS-S observation of the galaxy pair NGC 4485/4490. This is an interacting system containing a late-type spiral with an enhanced star formation rate (NGC 4490), and an irregular companion that possesses a disturbed morphology. A total of 29 discrete X-ray sources are found coincident with NGC 4490, but only one is found within NGC 4485. The sources range in observed X-ray luminosity from ~2 × 1037 to 4 × 1039 erg s-1. The more luminous sources appear, on average, to be spectrally harder than the fainter sources, an effect that is attributable to increased absorption in their spectra. Extensive diffuse X-ray emission is detected coincident with the disc of NGC 4490, and in the tidal tail of NGC 4485, which appears to be thermal in nature and hence the signature of a hot interstellar medium in both galaxies. However, the diffuse component accounts for only ~10 per cent of the total X-ray luminosity of the system (2 × 1040 erg s-1, 0.5-8 keV), which arises predominantly in a handful of the brightest discrete sources. This diffuse emission fraction is unusually low for a galaxy pair which has many characteristics that would lead it to be classified as a starburst system, possibly as a consequence of the small gravitational potential well of the system. The discrete source population, on the other hand, is similar to that observed in other starburst systems, possessing a flat luminosity function slope of ~-0.6 and a total of six ultraluminous X-ray sources (ULX). Five of the ULX are identified as probable black hole X-ray binary systems, and the sixth (which is coincident with a radio continuum source) is identified as an X-ray luminous supernova remnant. The ULX all lie in star formation regions, providing further evidence of the link between the ULX phenomenon and active star formation. Importantly, this shows that even in star-forming regions, the ULX population is dominated by accreting systems. We discuss the

  13. RXTE Observations of the Seyfert 2 Galaxy MrK 348

    NASA Technical Reports Server (NTRS)

    Smith, David A.; Georgantopoulos, Ioannis; Warwick, Robert S.

    2000-01-01

    We present RXTE monitoring observations of the Seyfert 2 galaxy Mrk 348 spanning a 6 month period. The time-averaged spectrum in the 3-20 keV band shows many features characteristic of a Compton-thin Seyfert 2 galaxy, namely a hard underlying power-law continuum (Gamma approximately equal 1.8) with heavy soft X-ray absorption (N(sub H) approximately 10(exp 23)/sq cm) plus measurable iron K.alpha emission (equivalent width approximately 100 eV) and, at high energy, evidence for a reflection component (R approximately < 1). During the first half of the monitoring period the X-ray continuum flux from Mrk 348 remained relatively steady. However this was followed by a significant brightening of the source (by roughly a factor of 4) with the fastest change corresponding to a doubling of its X-ray flux on a timescale of about 20 days. The flux increase was accompanied by a marked softening of X-ray spectrum most likely attributable to a factor approximately 3 decline in the intrinsic line-of-sight column density. In contrast the iron K.alpha line and the reflection components showed no evidence of variability. These observations suggest a scenario in which the central X-ray source is surrounded by a patchy distribution of absorbing material located within about a light-week of the nucleus of Mrk 348. The random movement of individual clouds within the absorbing screen, across our line of sight, produces substantial temporal variations in the measured column density on timescales of weeks to months and gives rise to the observed X-ray spectral variability. However, as viewed from the nucleus the global coverage and typical thickness of the cloud layer remains relatively constant.

  14. THE MASS-DEPENDENT STAR FORMATION HISTORIES OF DISK GALAXIES: INFALL MODEL VERSUS OBSERVATIONS

    SciTech Connect

    Chang, R. X.; Hou, J. L.; Shen, S. Y.; Shu, C. G.

    2010-10-10

    We introduce a simple model to explore the star formation histories of disk galaxies. We assume that the disk originate and grows by continuous gas infall. The gas infall rate is parameterized by the Gaussian formula with one free parameter: the infall-peak time t{sub p} . The Kennicutt star formation law is adopted to describe how much cold gas turns into stars. The gas outflow process is also considered in our model. We find that, at a given galactic stellar mass M{sub *}, the model adopting a late infall-peak time t{sub p} results in blue colors, low-metallicity, high specific star formation rate (SFR), and high gas fraction, while the gas outflow rate mainly influences the gas-phase metallicity and star formation efficiency mainly influences the gas fraction. Motivated by the local observed scaling relations, we 'construct' a mass-dependent model by assuming that the low-mass galaxy has a later infall-peak time t{sub p} and a larger gas outflow rate than massive systems. It is shown that this model can be in agreement with not only the local observations, but also with the observed correlations between specific SFR and galactic stellar mass SFR/M{sub *} {approx} M{sub *} at intermediate redshifts z < 1. Comparison between the Gaussian-infall model and the exponential-infall model is also presented. It shows that the exponential-infall model predicts a higher SFR at early stage and a lower SFR later than that of Gaussian infall. Our results suggest that the Gaussian infall rate may be more reasonable in describing the gas cooling process than the exponential infall rate, especially for low-mass systems.

  15. Hard X-Ray Emission of the Luminous Infrared Galaxy NGC 6240 as Observed by Nustar

    NASA Technical Reports Server (NTRS)

    Puccetti, S.; Comastri, A.; Bauer, F. E.; Brandt, W. N.; Fiore, F.; Harrison, F. A.; Luo, B.; Stern, D.; Urry, C. M.; Alexander, D. M.; Annuar, A.; Arévalo, P.; Balokovic, M.; Boggs, S. E.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Hailey, C. J.; Koss, M. J.; La Massa, S.; Marinucci, A.; Ricci, C.; Walton, D. J.; Zappacosta, L.; Zhang, W.

    2016-01-01

    We present a broadband (approx.0.3-70 keV) spectral and temporal analysis of NuSTAR observations of the luminous infrared galaxy NGC 6240 combined with archival Chandra, XMM-Newton, and BeppoSAX data. NGC 6240 is a galaxy in a relatively early merger state with two distinct nuclei separated by approx.1.5. Previous Chandra observations resolved the two nuclei and showed that they are both active and obscured by Compton-thick material. Although they cannot be resolved by NuSTAR, we were able to clearly detect, for the first time, both the primary and the reflection continuum components thanks to the unprecedented quality of the NuSTAR data at energies >10 keV. The NuSTAR hard X-ray spectrum is dominated by the primary continuum piercing through an absorbing column density which is mildly optically thick to Compton scattering (tau approx. = 1.2, NH approx. 1.5×10(exp 24)/sq cm. We detect moderately hard X-ray (>10 keV) flux variability up to 20% on short (15-20 ks) timescales. The amplitude of the variability is largest at approx..30 keV and is likely to originate from the primary continuum of the southern nucleus. Nevertheless, the mean hard X-ray flux on longer timescales (years) is relatively constant. Moreover, the two nuclei remain Compton-thick, although we find evidence of variability in the material along the line of sight with column densities NH < or = 2×10(exp 23)/sq cm over long (approx.3-15 yr) timescales. The observed X-ray emission in the NuSTAR energy range is fully consistent with the sum of the best-fit models of the spatially resolved Chandra spectra of the two nuclei.

  16. Hard X-Ray Emission of the Luminous Infrared Galaxy NGC 6240 as Observed by Nustar

    NASA Technical Reports Server (NTRS)

    Puccetti, S.; Comastri, A.; Bauer, F. E.; Brandt, W. N.; Fiore, F.; Harrison, F. A.; Luo, B.; Stern, D.; Urry, C. M.; Alexander, D. M.; hide

    2016-01-01

    We present a broadband (approx.0.3-70 keV) spectral and temporal analysis of NuSTAR observations of the luminous infrared galaxy NGC 6240 combined with archival Chandra, XMM-Newton, and BeppoSAX data. NGC 6240 is a galaxy in a relatively early merger state with two distinct nuclei separated by approx.1.5. Previous Chandra observations resolved the two nuclei and showed that they are both active and obscured by Compton-thick material. Although they cannot be resolved by NuSTAR, we were able to clearly detect, for the first time, both the primary and the reflection continuum components thanks to the unprecedented quality of the NuSTAR data at energies >10 keV. The NuSTAR hard X-ray spectrum is dominated by the primary continuum piercing through an absorbing column density which is mildly optically thick to Compton scattering (tau approx. = 1.2, NH approx. 1.5×10(exp 24)/sq cm. We detect moderately hard X-ray (>10 keV) flux variability up to 20% on short (15-20 ks) timescales. The amplitude of the variability is largest at approx..30 keV and is likely to originate from the primary continuum of the southern nucleus. Nevertheless, the mean hard X-ray flux on longer timescales (years) is relatively constant. Moreover, the two nuclei remain Compton-thick, although we find evidence of variability in the material along the line of sight with column densities NH < or = 2×10(exp 23)/sq cm over long (approx.3-15 yr) timescales. The observed X-ray emission in the NuSTAR energy range is fully consistent with the sum of the best-fit models of the spatially resolved Chandra spectra of the two nuclei.

  17. The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

    NASA Astrophysics Data System (ADS)

    Newman, Jeffrey A.; Cooper, Michael C.; Davis, Marc; Faber, S. M.; Coil, Alison L.; Guhathakurta, Puragra; Koo, David C.; Phillips, Andrew C.; Conroy, Charlie; Dutton, Aaron A.; Finkbeiner, Douglas P.; Gerke, Brian F.; Rosario, David J.; Weiner, Benjamin J.; Willmer, C. N. A.; Yan, Renbin; Harker, Justin J.; Kassin, Susan A.; Konidaris, N. P.; Lai, Kamson; Madgwick, Darren S.; Noeske, K. G.; Wirth, Gregory D.; Connolly, A. J.; Kaiser, N.; Kirby, Evan N.; Lemaux, Brian C.; Lin, Lihwai; Lotz, Jennifer M.; Luppino, G. A.; Marinoni, C.; Matthews, Daniel J.; Metevier, Anne; Schiavon, Ricardo P.

    2013-09-01

    We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ~ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude MB = -20 at z ~ 1 via ~90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg2 divided into four separate fields observed to a limiting apparent magnitude of R AB = 24.1. Objects with z <~ 0.7 are readily identifiable using BRI photometry and rejected in three of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ~2.5 times more efficiently than in a purely magnitude-limited sample. Approximately 60% of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets that fail to yield secure redshifts are blue objects that lie beyond z ~ 1.45, where the [O II] 3727 Å doublet lies in the infrared. The DEIMOS 1200 line mm-1 grating used for the survey delivers high spectral resolution (R ~ 6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the DEEP2 DEIMOS data reduction pipelines. Extensive details are provided on object selection, mask design, biases in target selection and redshift measurements, the spec2d two-dimensional data-reduction pipeline, the spec1d automated redshift pipeline, and the zspec visual redshift verification process, along with examples of instrumental signatures or other artifacts that in some cases remain after data reduction. Redshift

  18. Search for dark matter annihilation signatures in H.E.S.S. observations of dwarf spheroidal galaxies

    NASA Astrophysics Data System (ADS)

    Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Carrigan, S.; Casanova, S.; Chadwick, P. M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Dalton, M.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goudelis, A.; Grondin, M.-H.; Grudzińska, M.; Hadsch, D.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Morâ, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Odaka, H.; Ohm, S.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reichardt, I.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Serpico, P.; Sol, H.; Spanier, F.; Spengler, G.; Spieß, F.; Stawarz, L.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Völk, H. J.; Volpe, F.; Vorster, M.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.; H. E. S. S. Collaboration

    2014-12-01

    Dwarf spheroidal galaxies of the Local Group are close satellites of the Milky Way characterized by a large mass-to-light ratio and are not expected to be the site of nonthermal high-energy gamma-ray emission or intense star formation. Therefore they are among the most promising candidates for indirect dark matter searches. During the last years the High Energy Stereoscopic System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes observed five of these dwarf galaxies for more than 140 hours in total, searching for TeV gamma-ray emission from annihilation of dark matter particles. The new results of the deep exposure of the Sagittarius dwarf spheroidal galaxy, the first observations of the Coma Berenices and Fornax dwarves and the reanalysis of two more dwarf spheroidal galaxies already published by the H.E.S.S. Collaboration, Carina and Sculptor, are presented. In the absence of a significant signal new constraints on the annihilation cross section applicable to weakly interacting massive particles (WIMPs) are derived by combining the observations of the five dwarf galaxies. The combined exclusion limit depends on the WIMP mass and the best constraint is reached at 1-2 TeV masses with a cross-section upper bound of ˜ 3.9 ×10-24 cm3 s-1 at a 95% confidence level.

  19. Observations of MilkyWay Dwarf Spheroidal galaxies with the Fermi-LAT detector and

    SciTech Connect

    Abdo, A.A.; Ackermann, M.; Ajello, M.; Atwood, W.B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E.D.; Bonamente, E.; Borgland, A.W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T.H.; Buson, S.; Caliandro, G.A.; /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC /UC, Santa Cruz /INFN, Pisa /DAPNIA, Saclay /INFN, Trieste /Trieste U. /INFN, Padua /Padua U. /INFN, Perugia /Perugia U. /Bari Polytechnic /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /IASF, Milan /George Mason U. /NASA, Goddard

    2010-05-26

    We report on the observations of 14 dwarf spheroidal galaxies with the Fermi Gamma-Ray Space Telescope taken during the first 11 months of survey mode operations. The Fermi telescope, which is conducting an all-sky {gamma}-ray survey in the 20 MeV to >300 GeV energy range, provides a new opportunity to test particle dark matter models through the expected {gamma}-ray emission produced by pair annihilation of weakly interacting massive particles (WIMPs). Local Group dwarf spheroidal galaxies, the largest galactic substructures predicted by the cold dark matter scenario, are attractive targets for such indirect searches for dark matter because they are nearby and among the most extreme dark matter dominated environments. No significant {gamma}-ray emission was detected above 100 MeV from the candidate dwarf galaxies. We determine upper limits to the {gamma}-ray flux assuming both power-law spectra and representative spectra from WIMP annihilation. The resulting integral flux above 100 MeV is constrained to be at a level below around 10{sup -9} photons cm{sup -2}s{sup -1}. Using recent stellar kinematic data, the {gamma}-ray flux limits are combined with improved determinations of the dark matter density profile in 8 of the 14 candidate dwarfs to place limits on the pair annihilation cross-section ofWIMPs in several widely studied extensions of the standard model, including its supersymmetric extension and other models that received recent attention. With the present data, we are able to rule out large parts of the parameter space where the thermal relic density is below the observed cosmological dark matter density and WIMPs (neutralinos here) are dominantly produced non-thermally, e.g. in models where supersymmetry breaking occurs via anomaly mediation. The {gamma}-ray limits presented here also constrain some WIMP models proposed to explain the Fermi and PAMELA e{sup +}e{sup -} data, including low-mass wino-like neutralinos and models with TeV masses pair

  20. Simultaneous X-ray and optical observations of true type 2 Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Bianchi, Stefano; Panessa, Francesca; Barcons, Xavier; Carrera, Francisco J.; La Franca, Fabio; Matt, Giorgio; Onori, Francesca; Wolter, Anna; Corral, Amalia; Monaco, Lorenzo; Ruiz, Ángel; Brightman, Murray

    2012-11-01

    We present the results of a campaign of simultaneous X-ray and optical observations of 'true' type 2 Seyfert galaxies candidates, i.e. active galactic nuclei without a broad-line region (BLR). Out of the initial sample composed of eight sources, one object, IC 1631, was found to be a misclassified starburst galaxy, another, Q2130-431, does show broad optical lines, while other two, IRAS 01428-0404 and NGC 4698, are very likely absorbed by Compton-thick gas along the line of sight. Therefore, these four sources are not unabsorbed Seyfert 2s as previously suggested in the literature. On the other hand, we confirm that NGC 3147, NGC 3660 and Q2131-427 belong to the class of true type 2 Seyfert galaxies, since they do not show any evidence for a broad component of the optical lines nor for obscuration in their X-ray spectra. These three sources have low accretion rates (ṁ=L bol /L Edd ≲0.01), in agreement with theoretical models which predict that the BLR disappears below a critical value of Lbol/LEdd. The last source, Mrk 273x, would represent an exception even of these accretion-dependent versions of the Unification Models, due to its high X-ray luminosity and accretion rate, and no evidence for obscuration. However, its optical classification as a Seyfert 2 is only based on the absence of a broad component of Hβ, due to the lack of optical spectra encompassing the Hα band. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA); with the TNG and Nordic Optical Telescope (NOT) operated on the island of La Palma by the Centro Galileo Galilei and the Nordic Optical Telescope Science Association, respectively, in the Spanish Observatorio del Roque de los Muchachos; at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC); at the European

  1. Aperture Synthesis Observations of Molecular Gas in the Wolf-Rayet Galaxy He 2-10

    NASA Astrophysics Data System (ADS)

    Kobulnicky, Chip; Sargent, Anneila; Conti, Peter; Hogg, David; Dickey, John

    1994-05-01

    We present aperture synthesis observations of the prototype Wolf-Rayet galaxy He 2-10 in the line of (12) CO(1-0). These observations represent one of the first aperture synthesis maps of molecular gas in a blue compact dwarf galaxy. He 2-10 contains two starburst regions, A and B, separated by 8 arcsec which corresponds to 350 pc at at distance of 9 Mpc. Optical spectroscopy of region A indicates the presence of some 300 Wolf-Rayet and 4000 O-type stars, consistent with a very young starburst (Vacca & Conti, 1992, ApJ 401, 543). From a line integral of of 165+/-8 K km s(-1) we derive a total molecular gas mass of 1.8 times 10(8) M_sun based on (12) CO(1-0) spectra from the 12m NRAO telescope. The ratio of molecular to atomic gas mass, M(H_2)/M(HI)=0.54, is among the highest of any late type or blue compact dwarf galaxy. (12) CO(1-0) maps made with the Owens valley interferometer show two dynamical systems, suggesting an interaction-triggered starburst. While the CO peak is not conincident with either optical maximum, the CO is more nearly centered on the brighter and younger of the two starburst regions, A. There is no visible concentration of molecular gas near starburst region B which contains only a few hundred O-type stars. A significant fraction of the CO lies well outside the bright optical core, and is thus unaffiliated with the site of active star formation. We find a lower limit to the dynamical mass in the central 70 pc of 3.0times 10(6) M_sun inferred from the CO rotation curve. Conti & Vacca (1994, ref) estimate the combined mass of nine blue starburst knots revealed by HST UV imaging to be 4.5times 10(6) M_sun. Even if the inclination of He 2-10 is as low as 30(deg) , the young clusters, termed proto-globular clusters by Conti & Vacca, comprise at least 75% of the dynamical mass in the inner 70 pc!

  2. Constraining the History of the Sagittarius Dwarf Galaxy Using Observations of Its Tidal Debris

    NASA Astrophysics Data System (ADS)

    Johnston, K. V.; Majewski, S. R.; Siegel, M. H.; Reid, I. N.; Kunkel, W. E.

    1999-10-01

    We present a comparison of semianalytic models of the phase-space structure of tidal debris with measurements of average distances, velocities, and surface densities of stars associated with the Sagittarius dwarf galaxy, compiled from all observations reported since its discovery in 1994. We find that several interesting features in the data can be explained by these models. The properties of stars about +/-10 deg-15 deg away from the center of Sgr-in particular, the orientation of material perpendicular to Sgr's orbit and the kink in the velocity gradient-are consistent with those expected for unbound material stripped during the most recent pericentric passage ~50 Myr ago. The break in the slope of the surface density seen by Mateo, Olszewski, & Morrison at b~-35 deg can be understood as marking the end of this material. However, the detections beyond this point are unlikely to represent debris in a trailing streamer, torn from Sgr during the immediately preceding passage ~0.7 Gyr ago, as the surface density of this streamer would be too low compared with observations in these regions. The low-b detections are more plausibly explained by a leading streamer of material that was lost more that 1 Gyr ago and has wrapped all the way around the Galaxy to intercept the line of sight. The distance and veloc