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Sample records for ly-alpha selected galaxies

  1. THE UV-CONTINUUM PROPERTIES OF Ly{alpha}-SELECTED GALAXIES AT z = 6.5

    SciTech Connect

    Cowie, Lennox L.; Hu, Esther M.; Songaila, Antoinette E-mail: acowie@ifa.hawaii.edu

    2011-07-10

    We report the first space-based very deep near-infrared continuum observations of a uniform sample of z = 6.5 galaxies with log(L(Ly{alpha})) = 42.5-43 erg s{sup -1} selected from narrowband line searches and with spectroscopically confirmed Ly{alpha} emission. The 1.4 {mu}m Hubble Space Telescope WFC3 observations are deep enough (AB(1{sigma}) = 28.75) to measure individual continuum magnitudes at this redshift for all of the objects. We compare the results with continuum-selected samples at the same redshift and find that Ly{alpha} emission is present in 24% of all galaxies with M{sub AB}(1350 A) < -20 at z = 6.5. The error in this quantity is dominated by systematic uncertainties, which could be as large as multiplicative factors of three. The Ly{alpha} galaxies are extended but small (size <1 kpc), and have star formation rates of approximately 10 M{sub sun} yr{sup -1}. We find a mean L(Ly{alpha})/{nu}L{sub {nu}} at 1400 A to be 0.08, with the seven objects showing a range from 0.026 to 0.26, implying that there is little sign of destruction of the Ly{alpha} line. All of the properties of the z = 6.5 sample appear to be very similar to those of Ly{alpha} emitters at lower redshifts.

  2. STACKED REST-FRAME ULTRAVIOLET SPECTRA OF Ly{alpha}-EMITTING AND CONTINUUM-SELECTED GALAXIES AT 2 < z < 3.5

    SciTech Connect

    Berry, Michael; Gawiser, Eric; Guaita, Lucia; Padilla, Nelson; Francke, Harold; Treister, Ezequiel; Blanc, Guillermo A.; Ciardullo, Robin; Gronwall, Caryl

    2012-04-10

    We present properties of individual and composite rest-UV spectra of continuum- and narrowband-selected star-forming galaxies (SFGs) at a redshift of 2 < z < 3.5 discovered by the MUSYC collaboration in the Extended Chandra Deep Field-South. Among our sample of 81 UV-bright SFGs, 59 have R < 25.5, of which 32 have rest-frame equivalent widths of W{sub Ly{alpha}} > 20 A, the canonical limit to be classified as an Ly{alpha}-emitting galaxy. We divide our data set into subsamples based on properties that we are able to measure for each individual galaxy: Ly{alpha} equivalent width, rest-frame UV colors, and redshift. Among our subsample of galaxies with R < 25.5, those with rest frame W{sub Ly{alpha}} > 20 A have bluer UV continua, weaker low-ionization interstellar absorption lines, weaker C IV absorption, and stronger Si II* nebular emission than those with W{sub Ly{alpha}} < 20 A. We measure a velocity offset of {Delta}v {approx} 600 km s{sup -1} between Ly{alpha} emission and low-ionization absorption, which does not vary substantially among any of our subsamples. We find that the interstellar component, as opposed to the stellar component, dominates the high-ionization absorption line profiles. We find that the low- and high-ionization Si ionization states have similar kinematic properties, yet the low-ionization absorption is correlated with Ly{alpha} emission and the high-ionization absorption is not. These trends are consistent with outflowing neutral gas being in the form of neutral clouds embedded in ionized gas as previously suggested by Steidel et al. Moreover, our galaxies with bluer UV colors have stronger Ly{alpha} emission, weaker low-ionization absorption, and more prominent nebular emission line profiles. From a redshift of 2.7 < z < 3.5 to 2.0 < z < 2.7, our subsample of galaxies with W{sub Ly{alpha}} < 20 Angstrom-Sign shows no significant evolution in their physical properties or the nature of their outflows. Among our data set, UV-bright galaxies

  3. FIRST SPECTROSCOPIC MEASUREMENTS OF [O III] EMISSION FROM Ly{alpha} SELECTED FIELD GALAXIES AT z {approx} 3.1

    SciTech Connect

    McLinden, Emily M.; Rhoads, James E.; Malhotra, Sangeeta; Hibon, Pascale; Richardson, Mark L. A.; Finkelstein, Steven L.; Cresci, Giovanni; Quirrenbach, Andreas; Pasquali, Anna; Bian Fuyan; Fan Xiaohui; Woodward, Charles E.

    2011-04-01

    We present the first spectroscopic measurements of the [O III] 5007 A line in two z {approx} 3.1 Ly{alpha} emitting galaxies (LAEs) using the new near-infrared instrument LUCIFER1 on the 8.4 m Large Binocular Telescope. We also describe the optical imaging and spectroscopic observations used to identify these LAEs. Using the [O III] line we have measured accurate systemic redshifts for these two galaxies, and discovered a velocity offset between the [O III] and Ly{alpha} lines in both, with the Ly{alpha} line peaking 342 and 125 km s{sup -1} redward of the systemic velocity. These velocity offsets imply that there are powerful outflows in high-redshift LAEs. They also ease the transmission of Ly{alpha} photons through the interstellar medium and intergalactic medium around the galaxies. By measuring these offsets directly, we can refine both Ly{alpha}-based tests for reionization, and Ly{alpha} luminosity function measurements where the Ly{alpha} forest affects the blue wing of the line. Our work also provides the first direct constraints on the strength of the [O III] line in high-redshift LAEs. We find [O III] fluxes of 7 and 36 x10{sup -17} erg s{sup -1} cm{sup -2} in two z {approx} 3.1 LAEs. These lines are strong enough to dominate broadband flux measurements that include the line (in this case, K{sub s} -band photometry). Spectral energy distribution fits that do not account for the lines would therefore overestimate the 4000 A (and/or Balmer) break strength in such galaxies, and hence also the ages and stellar masses of such high-z galaxies.

  4. SIZING UP Ly{alpha} AND LYMAN BREAK GALAXIES

    SciTech Connect

    Malhotra, Sangeeta; Rhoads, James E.; McLinden, Emily; Finkelstein, Steven L.; Hathi, Nimish; Nilsson, Kim; Pirzkal, Norbert

    2012-05-10

    We measure the sizes for a sample of 174 Ly{alpha}-selected galaxies with broadband imaging with the Hubble Space Telescope. Over the redshift range 2.25 < z < 6, Ly{alpha}-selected galaxies have a characteristic, constant, small size in rest-frame ultraviolet (UV) light. Coupled with a characteristic star formation intensity (i.e., UV luminosity per unit area), this can explain their non-evolving ultraviolet continuum luminosity function. This is in contrast to Lyman break galaxies (LBGs) over the same redshift range, which have been previously shown to increase in linear size as H(z){sup -1}. The compact physical size seems to be a critical determining factor in whether a galaxy will show Ly{alpha} emission or not. The L{sub *} of LBGs and its evolution with redshift can be derived from a simple model where the star formation intensity has an upper limit set by feedback processes, independent of redshift. The increase in L{sub *} of LBGs is mainly driven by the increase in linear size over redshifts for z = 2-7. Since Ly{alpha} galaxies do not grow in linear size, they do not show an increase in L{sub *}.

  5. A Ly{alpha} GALAXY AT REDSHIFT z = 6.944 IN THE COSMOS FIELD

    SciTech Connect

    Rhoads, James E.; Hibon, Pascale; Malhotra, Sangeeta; Cooper, Michael; Weiner, Benjamin E-mail: James.Rhoads@asu.edu E-mail: m.cooper@uci.edu

    2012-06-20

    Ly{alpha} emitting galaxies can be used to study cosmological reionization, because a neutral intergalactic medium (IGM) scatters Ly{alpha} photons into diffuse halos whose surface brightness falls below typical survey detection limits. Here, we present the Ly{alpha} emitting galaxy LAE J095950.99+021219.1, identified at redshift z = 6.944 in the COSMOS field using narrowband imaging and follow-up spectroscopy with the IMACS instrument on the Magellan I Baade telescope. With a single object spectroscopically confirmed so far, our survey remains consistent with a wide range of IGM neutral fraction at z Almost-Equal-To 7, but further observations are planned and will help clarify the situation. Meantime, the object we present here is only the third Ly{alpha}-selected galaxy to be spectroscopically confirmed at z {approx}> 7, and is {approx}2-3 times fainter than the previously confirmed z Almost-Equal-To 7 Ly{alpha} galaxies.

  6. RADIATIVE TRANSFER MODELING OF Ly{alpha} EMITTERS. II. NEW EFFECTS ON GALAXY CLUSTERING

    SciTech Connect

    Zheng Zheng; Cen Renyue; Trac, Hy; Miralda-Escude, Jordi

    2011-01-01

    We study the clustering properties of z {approx} 5.7 Ly{alpha} emitters (LAEs) in a cosmological reionization simulation with a full Ly{alpha} radiative transfer calculation. Ly{alpha} radiative transfer substantially modifies the intrinsic Ly{alpha} emission properties, compared to observed ones, depending on the density and velocity structure environment around the Ly{alpha}-emitting galaxy. This environment-dependent Ly{alpha} selection introduces new features in LAE clustering, suppressing (enhancing) the line-of-sight (transverse) density fluctuations and giving rise to scale-dependent galaxy bias. In real space, the contours of the three-dimensional two-point correlation function of LAEs appear to be prominently elongated along the line of sight on large scales, an effect that is opposite to and much stronger than the linear redshift-space distortion effect. The projected two-point correlation function is greatly enhanced in amplitude by a factor of up to a few, compared to the case without the environment-dependent selection effect. The new features in LAE clustering can be understood with a simple, physically motivated model, where Ly{alpha} selection depends on matter density, velocity, and their gradients. We discuss the implications and consequences of the effects on galaxy clustering from Ly{alpha} selection in interpreting clustering measurements and in constraining cosmology and reionization from LAEs.

  7. EXTENDED Ly{alpha} EMISSION AROUND STAR-FORMING GALAXIES

    SciTech Connect

    Zheng Zheng; Cen Renyue; Weinberg, David; Trac, Hy; Miralda-Escude, Jordi

    2011-10-01

    Ly{alpha} photons that escape the interstellar medium of star-forming galaxies may be resonantly scattered by neutral hydrogen atoms in the circumgalactic and intergalactic media, thereby increasing the angular extent of the galaxy's Ly{alpha} emission. We present predictions of this extended, low surface brightness Ly{alpha} emission based on radiative transfer modeling in a cosmological reionization simulation. The extended emission can be detected from stacked narrowband images of Ly{alpha} emitters (LAEs) or of Lyman break galaxies (LBGs). Its average surface brightness profile has a central cusp, then flattens to an approximate plateau beginning at an inner characteristic scale below {approx}0.2 Mpc (comoving), then steepens again beyond an outer characteristic scale of {approx}1 Mpc. The inner scale marks the transition from scattered light of the central source to emission from clustered sources, while the outer scale marks the spatial extent of scattered emission from these clustered sources. Both scales tend to increase with halo mass, UV luminosity, and observed Ly{alpha} luminosity. The extended emission predicted by our simulation is already within reach of deep narrowband photometry using large ground-based telescopes. Such observations would test radiative transfer models of emission from LAEs and LBGs, and they would open a new window on the circumgalactic environment of high-redshift star-forming galaxies.

  8. Discovery of a Ly-alpha galaxy near a damped Ly-alpha absorber at z = 2.3

    NASA Technical Reports Server (NTRS)

    Lowenthal, James D.; Hogan, Craig J.; Green, Richard F.; Caulet, Adeline; Woodgate, Bruce E.; Brown, Larry; Foltz, Craig B.

    1991-01-01

    The detection of a galaxy associated with the damped Ly-alpha absorbing cloud seen at z = 2.309 toward the QSO PHL 957 is reported. In addition to a strong but narrow Ly-alpha emission line and weaker C IV and He II lines, the object shows continuum at V about 24, with a slope rising slightly toward the red. This is similar to what is seen in high-redshift radio galaxies, but this galaxy does not correspond to any known radio source. The detected emission lines and continuum are most easily interpreted as light from hot, recently formed stars, implying a sizable star formation rate and a scarcity of dust. The spatial correlation of the absorbing cloud and the companion galaxy supports the interpretation of damped Ly-alpha clouds as objects fundamentally different from the lower column density Ly-alpha forest clouds, which show weak or no clustering.

  9. DIFFUSE Ly{alpha} EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES

    SciTech Connect

    Steidel, Charles C.; Bogosavljevic, Milan; Shapley, Alice E.; Kollmeier, Juna A.; Reddy, Naveen A.; Erb, Dawn K.; Pettini, Max

    2011-08-01

    Using a sample of 92 UV continuum-selected, spectroscopically identified galaxies with (z) = 2.65, all of which have been imaged in the Ly{alpha} line with extremely deep narrow-band imaging, we examine galaxy Ly{alpha} emission profiles to very faint surface brightness limits. The galaxy sample is representative of spectroscopic samples of Lyman break galaxies (LBGs) at similar redshifts in terms of apparent magnitude, UV luminosity, inferred extinction, and star formation rate and was assembled without regard to Ly{alpha} emission properties. Approximately 45% (55%) of the galaxy spectra have Ly{alpha} appearing in net absorption (emission), with {approx_equal} 20% satisfying commonly used criteria for the identification of 'Ly{alpha} emitters' (LAEs; W{sub 0}(Ly{alpha}) {>=} 20 A). We use extremely deep stacks of rest-UV continuum and continuum-subtracted Ly{alpha} images to show that all sub-samples exhibit diffuse Ly{alpha} emission to radii of at least 10'' ({approx}80 physical kpc). The characteristic exponential scale lengths for Ly{alpha} line emission exceed that of the {lambda}{sub 0} = 1220 A UV continuum light by factors of {approx}5-10. The surface brightness profiles of Ly{alpha} emission are strongly suppressed relative to the UV continuum light in the inner few kpc, by amounts that are tightly correlated with the galaxies' observed spectral morphology; however, all galaxy sub-subsamples, including that of galaxies for which Ly{alpha} appears in net absorption in the spectra, exhibit qualitatively similar diffuse Ly{alpha} emission halos. Accounting for the extended Ly{alpha} emission halos, which generally would not be detected in the slit spectra of individual objects or with typical narrow-band Ly{alpha} imaging, increases the total Ly{alpha} flux (and rest equivalent width W{sub 0}(Ly{alpha})) by an average factor of {approx}5, and by a much larger factor for the 80% of LBGs not classified as LAEs. We argue that most, if not all, of the observed

  10. Ly{alpha} COOLING EMISSION FROM GALAXY FORMATION

    SciTech Connect

    Faucher-Giguere, Claude-Andre; Keres, Dusan; Dijkstra, Mark; Hernquist, Lars; Zaldarriaga, Matias

    2010-12-10

    Recent numerical and analytical studies have shown that galaxies accrete most of their baryons via the cold mode, from streams with temperatures T {approx} 10{sup 4}-10{sup 5} K. At these temperatures, the streams should radiate primarily in the Ly{alpha} line and have therefore been proposed as a model to power the extended, high-redshift objects known as Ly{alpha} blobs, and may also be relevant for powering a range of less luminous Ly{alpha} sources. We introduce a new Ly{alpha} radiative transfer code, {alpha}RT, and calculate the transport of the Ly{alpha} emission from cold accretion in cosmological hydrodynamical simulations. In this paper, we describe our methodology, and address physical and numerical issues that are critical to making accurate predictions for the cooling luminosity, but that have been mostly neglected or treated simplistically so far. In particular, we highlight the importance of self-shielding and of properly treating sub-resolution models in numerical simulations. Most existing simulations do not self-consistently incorporate these effects, which can lead to order-of-magnitude errors in the predicted cooling luminosity. Using a combination of post-processing ionizing radiative transfer and re-simulation techniques, we develop an approximation to the consistent evolution of the self-shielded gas. We quantify the dependence of the Ly{alpha} cooling luminosity on halo mass at z = 3 for the simplified problem of pure gas accretion embedded in the cosmic radiation background and without feedback, and present radiative transfer results for a particular system. While pure cooling in massive halos (without additional energy input from star formation and active galactic nuclei) is in principle sufficient to produce L{sub {alpha}} {approx} 10{sup 43}-10{sup 44} erg s{sup -1} blobs, this requires including energy released in gas of density sufficient to form stars, but which is kept 100% gaseous in our optimistic estimates. Excluding emission from

  11. Ly{alpha} EMITTING GALAXIES AS EARLY STAGES IN GALAXY FORMATION

    SciTech Connect

    Cowie, Lennox L.; Barger, Amy J.; Hu, Esther M.

    2011-09-10

    We present optical spectroscopy of two samples of Galaxy Evolution Explorer grism selected Ly{alpha} emitters (LAEs): one at z = 0.195-0.44 and the other at z = 0.65-1.25. We have also observed a comparison sample of galaxies in the same redshift intervals with the same UV magnitude distributions but with no detected Ly{alpha}. We use the optical spectroscopy to eliminate active galactic nuclei and to obtain the optical emission-line properties of the samples. We compare the luminosities of the LAEs in the two redshift intervals and show that there is dramatic evolution in the maximum Ly{alpha} luminosity over z = 0-1. Focusing on the z = 0.195-0.44 samples alone, we show that there are tightly defined relations between all of the galaxy parameters and the rest-frame equivalent width (EW) of H{alpha}. The higher EW(H{alpha}) sources all have lower metallicities, bluer colors, smaller sizes, and less extinction, consistent with their being in the early stages of the galaxy formation process. We find that 75% {+-} 12% of the LAEs have EW(H{alpha}) >100 A and, conversely, that 31% {+-} 13% of galaxies with EW(H{alpha}) >100 A are LAEs. We correct the broadband magnitudes for the emission-line contributions and use spectral synthesis fits to estimate the ages of the galaxies. We find a median age of 1.1 x 10{sup 8} yr for the LAE sample and 1.4 x 10{sup 9} yr for the UV-continuum sample without detected Ly{alpha}. The median metallicity of the LAE sample is 12 + log (O/H) = 8.24, or about 0.4 dex lower than the UV-continuum sample.

  12. RESOLVING THE GALAXIES WITHIN A GIANT Ly{alpha} NEBULA: WITNESSING THE FORMATION OF A GALAXY GROUP?

    SciTech Connect

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T.; Brodwin, Mark; Chaffee, Frederic H.; Desai, Vandana; Soifer, B. T.; Eisenhardt, Peter; Le Floc'h, Emeric; Matsuda, Yuichi

    2012-06-20

    Detailed analysis of the substructure of Ly{alpha} nebulae can put important constraints on the physical mechanisms at work and the properties of galaxies forming within them. Using high-resolution Hubble Space Telescope (HST) imaging of a Ly{alpha} nebula at z Almost-Equal-To 2.656, we have taken a census of the compact galaxies in the vicinity, used optical/near-infrared colors to select system members, and put constraints on the morphology of the spatially extended emission. The system is characterized by (1) a population of compact, low-luminosity ({approx}0.1 L*) sources-17 primarily young, small (R{sub e} Almost-Equal-To 1-2 kpc), disky galaxies including an obscured active galactic nucleus-that are all substantially offset ({approx}>20 kpc) from the line-emitting nebula; (2) the lack of a central galaxy at or near the peak of the Ly{alpha} emission; and (3) several nearly coincident, spatially extended emission components-Ly{alpha}, He II, and UV continuum-that are extremely smooth. These morphological findings are difficult to reconcile with theoretical models that invoke outflows, cold flows, or resonant scattering, suggesting that while all of these physical phenomena may be occurring, they are not sufficient to explain the powering and large extent of Ly{alpha} nebulae. In addition, although the compact galaxies within the system are irrelevant as power sources, the region is significantly overdense relative to the field galaxy population (by at least a factor of four). These observations provide the first estimate of the luminosity function of galaxies within an individual Ly{alpha} nebula system and suggest that large Ly{alpha} nebulae may be the seeds of galaxy groups or low-mass clusters.

  13. A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. I. SURVEY DESIGN AND CANDIDATE SELECTION

    SciTech Connect

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T.

    2012-04-01

    Giant Ly{alpha} nebulae (or Ly{alpha} 'blobs') are likely sites of ongoing massive galaxy formation, but the rarity of these powerful sources has made it difficult to form a coherent picture of their properties, ionization mechanisms, and space density. Systematic narrowband Ly{alpha} nebula surveys are ongoing, but the small redshift range covered and the observational expense limit the comoving volume that can be probed by even the largest of these surveys and pose a significant problem when searching for such rare sources. We have developed a systematic search technique designed to find large Ly{alpha} nebulae at 2 {approx}< z {approx}< 3 within deep broadband imaging and have carried out a survey of the 9.4 deg{sup 2} NOAO Deep Wide-Field Survey Booetes field. With a total survey comoving volume of Almost-Equal-To 10{sup 8} h{sup -3}{sub 70} Mpc{sup 3}, this is the largest volume survey for Ly{alpha} nebulae ever undertaken. In this first paper in the series, we present the details of the survey design and a systematically selected sample of 79 candidates, which includes one previously discovered Ly{alpha} nebula.

  14. Ly{alpha} ESCAPE FROM z {approx} 0.03 STAR-FORMING GALAXIES: THE DOMINANT ROLE OF OUTFLOWS

    SciTech Connect

    Wofford, Aida; Leitherer, Claus; Salzer, John

    2013-03-10

    The usefulness of H I Ly{alpha} photons for characterizing star formation in the distant universe is limited by our understanding of the astrophysical processes that regulate their escape from galaxies. These processes can only be observed in detail out to a few Multiplication-Sign 100 Mpc. Past nearby (z < 0.3) spectroscopic studies are based on small samples and/or kinematically unresolved data. Taking advantage of the high sensitivity of Hubble Space Telescope's Cosmic Origins Spectrograph (COS), we observed the Ly{alpha} lines of 20 H{alpha}-selected galaxies located at =0.03. The galaxies cover a broad range of luminosity, oxygen abundance, and reddening. In this paper, we characterize the observed Ly{alpha} lines and establish correlations with fundamental galaxy properties. We find seven emitters. These host young ({<=}10 Myr) stellar populations have rest-frame equivalent widths in the range 1-12 A, and have Ly{alpha} escape fractions within the COS aperture in the range 1%-12%. One emitter has a double-peaked Ly{alpha} with peaks 370 km s{sup -1} apart and a stronger blue peak. Excluding this object, the emitters have Ly{alpha} and O I {lambda}1302 offsets from H{alpha} in agreement with expanding-shell models and Lyman break galaxies observations. The absorbers have offsets that are almost consistent with a static medium. We find no one-to-one correspondence between Ly{alpha} emission and age, metallicity, or reddening. Thus, we confirm that Ly{alpha} is enhanced by outflows and is regulated by the dust and H I column density surrounding the hot stars.

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

    SciTech Connect

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

    2010-06-20

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

  16. Ly(alpha) emission and absorption features in the spectra of galaxies

    NASA Technical Reports Server (NTRS)

    Chen, W. L.; Neufeld, David A.

    1994-01-01

    The combined effects of interstellar dust absorption and of scattering by hydrogen atoms may give rise to a Ly(alpha) spectral feature of negative equivalent width, as has been observed in several star-forming galaxies. By considering the transfer of Ly(alpha) line radiation and of neighboring stellar continuum radiation within a dusty galaxy, we find that dust absorption has three effects: (1) it reduces the apparent ultraviolet continuum luminosity at all wavelengths; (2) it preferentially decreases the apparent Ly(alpha) line luminosity from H II regions; and (3) it creates an 'attenuation feature' in the continuum spectrum -- centered at the Ly(alpha) rest frequency -- which occurs because the attenuation of the stellar continuum radiation increases as the Ly(alpha) rest frequency is approached, due to the effects of scattering by hydrogen atoms. For plausible values of the galactic dust content and of the disk thickness, these effects can lead to a negative net Ly(alpha) equivalent width, even for galaxies in which the unattenuated spectrum would show a strong Ly(alpha) emission line.

  17. WERE PROGENITORS OF LOCAL L* GALAXIES Ly{alpha} EMITTERS AT HIGH REDSHIFT?

    SciTech Connect

    Yajima, Hidenobu; Li Yuexing; Zhu Qirong; Gronwall, Caryl; Ciardullo, Robin; Abel, Tom

    2012-08-01

    The Ly{alpha} emission has been observed from galaxies over a redshift span z {approx} 0-8.6. However, the evolution of high-redshift Ly{alpha} emitters (LAEs), and the link between these populations and local galaxies, remains poorly understood. Here, we investigate the Ly{alpha} properties of progenitors of a local L* galaxy by combining cosmological hydrodynamic simulations with three-dimensional radiative transfer calculations using the new ART{sup 2} code. We find that the main progenitor (the most massive one) of a Milky-Way-like galaxy has a number of Ly{alpha} properties close to those of observed LAEs at z {approx} 2-6, but most of the fainter ones appear to fall below the detection limits of current surveys. The Ly{alpha} photon escape fraction depends sensitively on a number of physical properties of the galaxy, such as mass, star formation rate, and metallicity, as well as galaxy morphology and orientation. Moreover, we find that high-redshift LAEs show blueshifted Ly{alpha} line profiles characteristic of gas inflow, and that the Ly{alpha} emission by excitation cooling increases with redshift, and becomes dominant at z {approx}> 6. Our results suggest that some observed LAEs at z {approx} 2-6 with luminosity of L{sub Ly{alpha}} {approx} 10{sup 42}-10{sup 43} erg s{sup -1} may be similar to the main progenitor of the Milky Way at high redshift, and that they may evolve into present-day L* galaxies.

  18. Ly alpha and IR galaxy companions of high redshift damped Ly alpha QSO absorbers

    NASA Technical Reports Server (NTRS)

    Caulet, Adeline; Mccaughrean, Mark

    1993-01-01

    We have used a Near-Infrared Camera and Multi-Object Spectrometer (NICMOS3) HgCdTe 256x256 array detector with the Infrared (IR) camera on the 2.3m telescope at Steward Observatory to image several Quasi-Stellar Object (QSO) fields. The limiting magnitude is K'(2.1 microns) = 21.0 - 21.5 mag per square arcsec for a 3 sigma detection in 3 hours of in-field chopping observations. Each QSO line-of-sight samples several known absorbers with Mg2(lambda)2796-2803 A and/or C4(lambda)1548-1551 A absorption doublets. The equivalent width distributions of the low and high ionization absorption lines of the absorber sample are identical to those of the parent population of all absorbers. This selection process, used already for a spectroscopic survey of Mg2 absorption lines in C4-selected absorption systems at high z, gives a methodical approach to observing, reduces the observer biases, and makes a more efficient use of telescope time. This selection guarantees that imaging of the sample of QSO fields will provide complete sampling of the whole population of high z QSO absorbers. Follow-up optical and IR spectroscopy of these objects is scheduled for redshift measurement and confirmation of the absorbing galaxies and the cluster members.

  19. A FLUX-LIMITED SAMPLE OF z {approx} 1 Ly{alpha} EMITTING GALAXIES IN THE CHANDRA DEEP FIELD SOUTH ,

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    Barger, A. J.; Wold, I. G. B.; Cowie, L. L.

    2012-04-20

    We describe a method for obtaining a flux-limited sample of Ly{alpha} emitters from Galaxy Evolution Explorer (GALEX) grism data. We show that the multiple GALEX grism images can be converted into a three-dimensional (two spatial axes and one wavelength axis) data cube. The wavelength slices may then be treated as narrowband images and searched for emission-line galaxies. For the GALEX NUV grism data, the method provides a Ly{alpha} flux-limited sample over the redshift range z = 0.67-1.16. We test the method on the Chandra Deep Field South field, where we find 28 Ly{alpha} emitters with faint continuum magnitudes (NUV > 22) that are not present in the GALEX pipeline sample. We measure the completeness by adding artificial emitters and measuring the fraction recovered. We find that we have an 80% completeness above a Ly{alpha} flux of 10{sup -15} erg cm{sup -2} s{sup -1}. We use the UV spectra and the available X-ray data and optical spectra to estimate the fraction of active galactic nuclei in the selection. We report the first detection of a giant Ly{alpha} blob at z < 1, though we find that these objects are much less common at z = 1 than at z = 3. Finally, we compute limits on the z {approx} 1 Ly{alpha} luminosity function and confirm that there is a dramatic evolution in the luminosity function over the redshift range z = 0-1.

  20. The Ly(alpha) Line Profiles of Ultraluminous Infrared Galaxies: Fast Winds and Lyman Continuum Leakage

    NASA Technical Reports Server (NTRS)

    Martin, Crystal L.; Dijkstra, Mark; Henry, Alaina L.; Soto, Kurt T.; Danforth, Charles W.; Wong, Joseph

    2015-01-01

    We present new Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet (far-UV) spectroscopy and Keck Echellete optical spectroscopy of 11 ultraluminous infrared galaxies (ULIRGs), a rare population of local galaxies experiencing massive gas inflows, extreme starbursts, and prominent outflows. We detect Ly(alpha) emission from eight ULIRGs and the companion to IRAS09583+4714. In contrast to the P Cygni profiles often seen in galaxy spectra, the Ly(alpha) profiles exhibit prominent, blueshifted emission out to Doppler shifts exceeding -1000 km/s in three H II-dominated and two AGN-dominated ULIRGs. To better understand the role of resonance scattering in shaping the Ly(alpha) line profiles, we directly compare them to non-resonant emission lines in optical spectra. We find that the line wings are already present in the intrinsic nebular spectra, and scattering merely enhances the wings relative to the line core. The Ly(alpha) attenuation (as measured in the COS aperture) ranges from that of the far-UV continuum to over 100 times more. A simple radiative transfer model suggests the Ly(alpha) photons escape through cavities which have low column densities of neutral hydrogen and become optically thin to the Lyman continuum in the most advanced mergers. We show that the properties of the highly blueshifted line wings on the Ly(alpha) and optical emission-line profiles are consistent with emission from clumps of gas condensing out of a fast, hot wind. The luminosity of the Ly(alpha) emission increases nonlinearly with the ULIRG bolometric luminosity and represents about 0.1-1% of the radiative cooling from the hot winds in the H II-dominated ULIRGs.

  1. POLARIZED EXTENDED Ly{alpha} EMISSION FROM A z = 2.3 RADIO GALAXY

    SciTech Connect

    Humphrey, A.; Vernet, J.; Fosbury, R. A. E.; Villar-Martin, M.; Di Serego Alighieri, S.; Cimatti, A.

    2013-05-01

    We present spatially resolved spectropolarimetric measurements of the 100 kpc scale gaseous environment of the z = 2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Ly{alpha} emission is low centrally (P < 5%), but rises to P = 16.4% {+-} 4.6% in the eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Ly{alpha} photons by H I. Not only is this the first detection of polarized Ly{alpha} around a radio-loud active galaxy, it is also the second detection to date for any kind of Ly{alpha} nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Ly{alpha} nebula, which we suggest may be the limb of a dusty shell, related to the large-scale H I absorbers often associated with high-z radio galaxies.

  2. DUST EXTINCTION AND METALLICITIES OF STAR-FORMING Ly{alpha} EMITTING GALAXIES AT LOW REDSHIFT

    SciTech Connect

    Finkelstein, Steven L.; Papovich, Casey; Cohen, Seth H.; Malhotra, Sangeeta; Rhoads, James E.; Moustakas, John

    2011-06-01

    We present the results of an optical spectroscopic study of 12 GALEX-discovered star-forming Ly{alpha} emitting galaxies (LAEs) at z {approx} 0.3. We measure the emission-line fluxes from these galaxies by fitting their observed spectra to stellar population models in order to correct for underlying stellar absorption. We revisit earlier stellar population model fitting results, finding that excluding now-known active galactic nuclei lowers the typical stellar population age and stellar mass of this sample to {approx}300 Myr and {approx}4 x 10{sup 9} M{sub sun}, respectively. We calculate their dust extinction using the Balmer decrement, and find a typical visual attenuation of A{sub V} {approx} 0.3 mag, similar to that seen in some high-redshift LAEs. Comparing the ratios of Ly{alpha}/H{alpha} and the Ly{alpha} equivalent widths to the measured dust extinction, we find that the interstellar media (ISMs) in these objects appear to be neither enhancing nor seriously attenuating the Ly{alpha} equivalent widths, as would be the case in a quasi-clumpy ISM. Lastly, we perform a detailed analysis of the gas-phase metallicities of these galaxies, and we find that most galaxies in our sample have Z {approx}< 0.4 Z{sub sun}. We find that at a fixed stellar mass, these low-redshift LAE analogs are offset by {approx}0.3-0.6 dex lower metallicity from the general galaxy population at similar redshifts based on the local mass-metallicity relationship. This implies that galaxies with Ly{alpha} in emission may be systematically more metal-poor than star-forming galaxies at the same stellar mass and redshift, similar to preliminary results at z {approx} 2.

  3. KECK SPECTROSCOPY OF LYMAN-BREAK GALAXIES AND ITS IMPLICATIONS FOR THE UV-CONTINUUM AND Ly{alpha} LUMINOSITY FUNCTIONS AT z > 6

    SciTech Connect

    Jiang Linhua; Egami, Eiichi; Walth, Gregory; Kashikawa, Nobunari; Matsuda, Yuichi; Shimasaku, Kazuhiro; Nagao, Tohru; Ota, Kazuaki; Ouchi, Masami

    2011-12-10

    We present Keck spectroscopic observations of z > 6 Lyman-break galaxy (LBG) candidates in the Subaru Deep Field (SDF). The candidates were selected as i'-dropout objects down to z' = 27 AB magnitudes from an ultra-deep SDF z'-band image. With the Keck spectroscopy we identified 19 LBGs with prominent Ly{alpha} emission lines at 6 {<=} z {<=} 6.4. The median value of the Ly{alpha} rest-frame equivalent widths (EWs) is {approx}50 A, with four EWs >100 A. This well-defined spectroscopic sample spans a UV-continuum luminosity range of -21.8 {<=} M{sub UV} {<=} -19.5 (0.6 {approx} 5 L*{sub UV}) and a Ly{alpha} luminosity range of (0.3-3) Multiplication-Sign 10{sup 43} erg s{sup -1} (0.3-3 L*{sub Ly{alpha}}). We derive the UV and Ly{alpha} luminosity functions (LFs) from our sample at (z) {approx} 6.2 after we correct for sample incompleteness. We find that our measurement of the UV LF is consistent with the results of previous studies based on photometric LBG samples at 5 < z < 7. Our Ly{alpha} LF is also generally in agreement with the results of Ly{alpha}-emitter surveys at z {approx} 5.7 and 6.6. This study shows that deep spectroscopic observations of LBGs can provide unique constraints on both the UV and Ly{alpha} LFs at z > 6.

  4. EXTENDED Ly{alpha} EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS

    SciTech Connect

    Yajima, Hidenobu; Li Yuexing; Zhu Qirong

    2013-08-20

    Recent observations have discovered a population of extended Ly{alpha} sources, dubbed Ly{alpha} blobs (LABs), at high redshift z {approx} 2-6.6. These LABs typically have a luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and a size of tens of kiloparsecs, with some giant ones reaching up to D {approx} 100 kpc. However, the origin of these LABs is not well understood. In this paper, we investigate a merger model for the formation of LABs by studying Ly{alpha} emission from interacting galaxies at high redshifts by means of a combination of hydrodynamics simulations with three-dimensional radiative transfer calculations. Our galaxy simulations focus on a set of binary major mergers of galaxies with a mass range of 3-7 Multiplication-Sign 10{sup 12} M{sub Sun} in the redshift range z {approx} 3-7, and we use the newly improved ART{sup 2} code to perform the radiative transfer calculations, which couple multi-wavelength continuum, ionization of hydrogen, and Ly{alpha} line emission. We find that intense star formation and enhanced cooling induced by gravitational interaction produce strong Ly{alpha} emission from these merging galaxies. The Ly{alpha} emission appears to be extended due to the extended distribution of sources and gas. During the close encounter of galaxy progenitors when the star formation rate peaks at {approx}10{sup 3} M{sub Sun} yr{sup -1}, our model produces LABs with luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and size of D {approx} 10-20 kpc at z > 6 and D {approx} 20-50 kpc at z {approx} 3, in broad agreement with observations in the same redshift range. Our results suggest that merging galaxies may produce some typical LABs as observed, but the giant ones may be produced by mergers more massive than those in our model, or a combination of mergers and cold accretion from filaments on a large scale.

  5. Extended LY alpha -absorbing Halos around Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Bowen, David V.; Blades, J. Chris; Pettini, Max

    1996-06-01

    In order to establish the Lyα absorption cross section of present-day galaxies, we have identified 38 galaxies with z = 0-0.08 that lie within 40-500 h^-1^ kpc of the line of sight to a QSO observed with the Faint Object Spectrograph aboard the Hubble Space Telescope (HST). Including three galaxies in the field of 3C 273 investigated by previous authors, we find that nine of 41 galaxies have associated Lyα absorption. If the identified Lyα absorption systems are genuinely associated with the galaxies, then the covering factor of gas around galaxies remains roughly constant at ~40% between 100 and 300 h^-1^ kpc. Beyond 300 h^-1^ kpc, the incidence of absorption drops sharply. We conclude that (1) nearby galaxies do not possess Lyα-absorbing halos beyond 300 h^-1^ kpc in radius and (2) the covering factor of present-day galaxies between 50 and 300 h^-1^ kpc is 44% at an equivalent width limit of W >= 0.3 A. For the nine galaxies with associated Lyα absorption lines, differences in the galaxies systemic velocities and the velocity of the absorption line, {DELTA}v, range over +/- 300 km s^-1^, consistent with the distribution found at redshifts > 0.1 by Lanzetta et al. and Le Brun, Bergeron, & Boisse. Values of {DELTA}v spanning several hundred km s^-1^ are probably real for some of the QSO-galaxy pairs, however, and do not simply arise from errors in measuring cz_gal_ or cz_abs_. This suggests that the absorbing clouds are kinematically tied to the galaxy disks and that the distribution of {DELTA}v may arise because of the effects of galaxy inclination. We find no evidence for a correlation between Lyα equivalent width and galaxy line-of-sight separation, which weakens the argument that the identified galaxies are directly associated with the Lyα lines. Also, we find that absorption does not arise only from bright galaxies, since there are several examples in which low-luminosity galaxies apparently cause absorption. Yet we show that the absorbing halos around

  6. THE KINEMATICS OF MULTIPLE-PEAKED Ly{alpha} EMISSION IN STAR-FORMING GALAXIES AT z {approx} 2-3

    SciTech Connect

    Kulas, Kristin R.; Shapley, Alice E.; Kollmeier, Juna A.; Zheng Zheng; Steidel, Charles C.; Hainline, Kevin N.

    2012-01-20

    We present new results on the Ly{alpha} emission-line kinematics of 18 z {approx} 2-3 star-forming galaxies with multiple-peaked Ly{alpha} profiles. With our large spectroscopic database of UV-selected star-forming galaxies at these redshifts, we have determined that {approx}30% of such objects with detectable Ly{alpha} emission display multiple-peaked emission profiles. These profiles provide additional constraints on the escape of Ly{alpha} photons due to the rich velocity structure in the emergent line. Despite recent advances in modeling the escape of Ly{alpha} from star-forming galaxies at high redshifts, comparisons between models and data are often missing crucial observational information. Using Keck II NIRSPEC spectra of H{alpha} (z {approx} 2) and [O III]{lambda}5007 (z {approx} 3), we have measured accurate systemic redshifts, rest-frame optical nebular velocity dispersions, and emission-line fluxes for the objects in the sample. In addition, rest-frame UV luminosities and colors provide estimates of star formation rates and the degree of dust extinction. In concert with the profile sub-structure, these measurements provide critical constraints on the geometry and kinematics of interstellar gas in high-redshift galaxies. Accurate systemic redshifts allow us to translate the multiple-peaked Ly{alpha} profiles into velocity space, revealing that the majority (11/18) display double-peaked emission straddling the velocity-field zero point with stronger red-side emission. Interstellar absorption-line kinematics suggest the presence of large-scale outflows for the majority of objects in our sample, with an average measured interstellar absorption velocity offset of ({Delta}v{sub abs}) = -230 km s{sup -1}. A comparison of the interstellar absorption kinematics for objects with multiple- and single-peaked Ly{alpha} profiles indicate that the multiple-peaked objects are characterized by significantly narrower absorption line widths. We compare our data with the

  7. Obscuration of LY alpha Photons in Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Giavalisco, Mauro; Koratkar, Anuradha; Calzetti, Daniela

    1996-08-01

    We present a new study of the correlations between the Lyα emission, the UV extinction, and the metal content in a sample of 21 local, low-metallicity starburst galaxies from archival IUE spectra. We have consistently reextracted all the spectra using the optimal extraction algorithm by Kinney and coworkers, and we have also included galaxies not previously studied. In 40% of the cases our new measures of the Lyα equivalent width, Walpha_, differ from those reported in the literature by up to 50% of their value. The new measures show no significant correlation with either the obscuration of the UV continuum or the Balmer decrement, and only a very weak correlation with the metal index [O/H]. Using the flux ratio Lyα/Hβ instead of Walpha_ to take into account differences in the ionizing conditions of the nebular gas does not change these results. This shows that the extinction vicissitudes of the Lyα and nonresonant radiations have been decoupled during their propagations through the ISM. We interpret this as evidence that the ISM in the sample galaxies is, on average, highly inhomogeneous and that the transport of Lyα photons is primarily controlled by the ISM geometry rather than by the amount of dust. If the ISM geometry is mainly the result of the energy release from the star formation activity, we speculate that a similar phenomenology was also present at high redshifts. As the median of the absolute value of Walpha_ in our sample is relatively large, the line can be efficiently used to measure the redshifts of primeval galaxy candidates at redshifts 2 <~ z <~ 7 via optical spectroscopy with the 10 m class telescopes.

  8. A Luminosity Function of Ly(alpha)-Emitting Galaxies at Z [Approx. Equal to] 4.5(Sup 1),(Sup 2)

    NASA Technical Reports Server (NTRS)

    Dawson, Steve; Rhoads, James E.; Malhotra, Sangeeta; Stern, Daniel; Wang, JunXian; Dey, Arjun; Spinrad, Hyron; Jannuzi, Buell T.

    2007-01-01

    We present a catalog of 59 z [approx. equal to] 4:5 Ly(alpha)-emitting galaxies spectroscopically confirmed in a campaign of Keck DEIMOS follow-up observations to candidates selected in the Large Are (LALA) narrowband imaging survey.We targeted 97 candidates for spectroscopic follow-up; by accounting for the variety of conditions under which we performed spectroscopy, we estimate a selection reliability of approx.76%. Together with our previous sample of Keck LRIS confirmations, the 59 sources confirmed herein bring the total catalog to 73 spectroscopically confirmed z [approx. equal to] 4:5 Ly(alpha)- emitting galaxies in the [approx. equal to] 0.7 deg(exp 2) covered by the LALA imaging. As with the Keck LRIS sample, we find that a nonnegligible fraction of the co rest-frame equivalent widths (W(sub lambda)(sup rest)) that exceed the maximum predicted for normal stellar populations: 17%-31%(93%confidence) of the detected galaxies show (W(sub lambda)(sup rest)) 12%-27% (90% confidence) show (W(sub lambda)(sup rest)) > 240 A. We construct a luminosity function of z [approx. equal to] 4.5 Ly(alpha) emission lines for comparison to Ly(alpha) luminosity function < 6.6. We find no significant evidence for Ly(alpha) luminosity function evolution from z [approx. equal to] 3 to z [approx. equal to] 6. This result supports the conclusion that the intergalactic me largely reionized from the local universe out to z [approx. equal to] 6.5. It is somewhat at odds with the pronounced drop in the cosmic star formation rate density recently measured between z approx. 3 an z approx. 6 in continuum-selected Lyman-break galaxies, and therefore potentially sheds light on the relationship between the two populations.

  9. The discovery of six Ly{alpha} emitters near a radio galaxy at z {approx} 5.2

    SciTech Connect

    Venemans, B P; Rottgering, H A; Overzier, R A; Miley, G K; De Breuck, C; Kurk, J D; van Breugel, W; Carilli, C L; Ford, H; Heckman, T; McCarthy, P; Pentericci, L

    2004-09-15

    The authors present the results of narrow-band and broad-band imaging with the Very Large Telescope of the field surrounding the radio galaxy TN J0924-2201 at z = 5.2. 14 candidate Ly{alpha} emitters with an observed equivalent width of at least 124 {angstrom} were detected. Spectroscopy of 8 of these objects revealed 6 having redshifts similar to that of the radio galaxy. The density of emitters near the radio galaxy is a factor 3-4 higher than in the field, and comparable to the density of Ly{alpha} emitters in the protocluster 1338-1942 at z = 4.1. The Ly{alpha} emitters near TN J0924-2201 could therefore be part of a structure that will evolve into a 10{sup 15} M{sub {circle_dot}} cluster. These observations confirm that substantial clustering of Ly{alpha} emitters occur at z > 5 and strengthen the idea that radio galaxies in the early Universe pinpoint regions of high density.

  10. CONSTRAINING STELLAR PROPERTIES OF INTERVENING DAMPED Ly{alpha} AND Mg II ABSORBING GALAXIES TOWARD GRB 050730

    SciTech Connect

    Minowa, Y.; Okoshi, K.; Kobayashi, N.; Takami, H.

    2012-09-15

    We performed multiband deep imaging of the field around GRB 050730 to identify the host galaxies of intervening absorbers, which consist of a damped Ly{alpha} absorption (DLA) system at z{sub abs} = 3.564, a sub-DLA system at z{sub abs} = 3.022, and strong Mg II absorption systems at z{sub abs} = 1.773 and 2.253. Our observations were performed after the gamma-ray burst afterglow had disappeared. Thus, our imaging survey has a higher sensitivity to the host galaxies of the intervening absorbers than the normal imaging surveys in the direction of QSOs, for which the QSO glare tends to hide the foreground galaxies. In this deep imaging survey, we could not detect any unambiguous candidates for the host galaxies of the intervening absorbers. Using the 3{sigma} upper limit of the flux in the optical to mid-infrared observing bands, which corresponds to the UV to optical bands in the rest frame of the intervening absorbers, we constrained the star formation rates and stellar masses of the hosts. We estimated the star formation rates for the intervening absorbers to be {approx}< 2.5 M{sub Sun} yr{sup -1} for z > 3 DLAs and {approx}< 1.0 M{sub Sun} yr{sup -1} for z {approx} 2 Mg II systems. Their stellar masses are estimated to be several times 10{sup 9} M{sub Sun} or smaller for all intervening galaxies. These properties are comparable to dwarf galaxies, rather than the massive star-forming galaxies commonly seen in the z > 2 galaxy surveys based on emission-line selection or color selection.

  11. SPECTROSCOPIC CONFIRMATION OF THREE z-DROPOUT GALAXIES AT z = 6.844-7.213: DEMOGRAPHICS OF Ly{alpha} EMISSION IN z {approx} 7 GALAXIES

    SciTech Connect

    Ono, Yoshiaki; Shimasaku, Kazuhiro; Nakajima, Kimihiko; Ouchi, Masami; Mobasher, Bahram; Nayyeri, Hooshang; Dickinson, Mark; Kartaltepe, Jeyhan S.; Penner, Kyle; Weiner, Benjamin J.; Stern, Daniel; Kashikawa, Nobunari; Spinrad, Hyron

    2012-01-10

    We present the results of our ultra-deep Keck/DEIMOS spectroscopy of z-dropout galaxies in the Subaru Deep Field and Great Observatories Origins Deep Survey's northern field. For 3 out of 11 objects, we detect an emission line at {approx}1 {mu}m with a signal-to-noise ratio of {approx}10. The lines show asymmetric profiles with high weighted skewness values, consistent with being Ly{alpha}, yielding redshifts of z = 7.213, 6.965, and 6.844. Specifically, we confirm the z = 7.213 object in two independent DEIMOS runs with different spectroscopic configurations. The z = 6.965 object is a known Ly{alpha} emitter, IOK-1, for which our improved spectrum at a higher resolution yields a robust skewness measurement. The three z-dropouts have Ly{alpha} fluxes of 3 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} and rest-frame equivalent widths EW{sup Ly{alpha}}{sub 0} = 33-43 A. Based on the largest spectroscopic sample of 43 z-dropouts, which is the combination of our and previous data, we find that the fraction of Ly{alpha}-emitting galaxies (EW{sup Ly{alpha}}{sub 0} > 25 A) is low at z {approx} 7; 17% {+-} 10% and 24% {+-} 12% for bright (M{sub UV} {approx_equal} -21) and faint (M{sub UV} {approx_equal} -19.5) galaxies, respectively. The fractions of Ly{alpha}-emitting galaxies drop from z {approx} 6 to 7 and the amplitude of the drop is larger for faint galaxies than for bright galaxies. These two pieces of evidence would indicate that the neutral hydrogen fraction of the intergalactic medium increases from z {approx} 6 to 7 and that the reionization proceeds from high- to low-density environments, as suggested by an inside-out reionization model.

  12. FORMATION OF METAL-POOR GLOBULAR CLUSTERS IN Ly{alpha} EMITTING GALAXIES IN THE EARLY UNIVERSE

    SciTech Connect

    Elmegreen, Bruce G.; Malhotra, Sangeeta; Rhoads, James

    2012-09-20

    The size, mass, luminosity, and space density of Ly{alpha} emitting (LAE) galaxies observed at intermediate to high redshift agree with expectations for the properties of galaxies that formed metal-poor halo globular clusters (GCs). The low metallicity of these clusters is the result of their formation in low-mass galaxies. Metal-poor GCs could enter spiral galaxies along with their dwarf galaxy hosts, unlike metal-rich GCs, which form in the spirals themselves. Considering an initial GC mass larger than the current mass to account for multiple stellar populations, and considering the additional clusters that are likely to form with massive clusters, we estimate that each GC with a mass today greater than 2 Multiplication-Sign 10{sup 5} M{sub Sun} was likely to have formed among a total stellar mass {approx}> 3 Multiplication-Sign 10{sup 7} M{sub Sun }, a molecular mass {approx}> 10{sup 9} M{sub Sun }, and 10{sup 7} to 10{sup 9} M{sub Sun} of older stars, depending on the relative gas fraction. The star formation rate would have been several M{sub Sun} yr{sup -1} lasting for {approx}10{sup 7} yr, and the Ly{alpha} luminosity would have been {approx}> 10{sup 42} erg s{sup -1}. Integrating the LAE galaxy luminosity function above this minimum, considering the average escape probability for Ly{alpha} photons (25%), and then dividing by the probability that a dwarf galaxy is observed in the LAE phase (0.4%), we find agreement between the comoving space density of LAEs and the average space density of metal-poor GCs today. The local galaxy WLM, with its early starburst and old GC, could be an LAE remnant that did not get into a galaxy halo because of its remote location.

  13. PROBING THE INTERGALACTIC MEDIUM/GALAXY CONNECTION. V. ON THE ORIGIN OF Ly{alpha} AND O VI ABSORPTION AT z < 0.2

    SciTech Connect

    Prochaska, J. Xavier; Chen, H.-W.; Mulchaey, J.; Cooksey, K. E-mail: bjw@as.arizona.edu E-mail: mulchaey@obs.carnegiescience.edu

    2011-10-20

    We analyze the association of galaxies with Ly{alpha} and O VI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z{sub em} = 0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho} = 300 h{sup -1}{sub 72} kpc: 33/37 of our L > 0.01 L* galaxies show Ly{alpha} equivalent width W{sup Ly{alpha}} {>=} 50 mA. Galaxies of all luminosity L > 0.01 L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at {approx}10{sup 10.5{+-}0.3} M{sub sun} for a constant N{sub H} = 10{sup 19} cm{sup -2}. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W{sup Ly{alpha}} > 300 mA) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W{sup Ly{alpha}} = 30-300 mA occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of {approx}400 h{sup -1}{sub 72} kpc. Regarding O VI, we observe a near unity covering fraction to {rho} = 200 h{sup -1}{sub 72} kpc for L > 0.1 L* galaxies and to {rho} = 300 h{sup -1}{sub 72} kpc for sub-L* (0.1 L* < L < L*) galaxies. Similar to our Ly{alpha} results, stronger O VI systems (W{sup 1031} > 70 mA) arise in the virialized halos of L > 0.1 L* galaxies. Unlike Ly{alpha}, the weaker O VI systems (W{sup 1031} {approx} 30 mA) arise in the extended CGM of sub-L* galaxies. The majority of O VI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L {approx} 0.3 L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.

  14. PRESENT-DAY DESCENDANTS OF z = 3 Ly{alpha}-EMITTING GALAXIES IN THE MILLENNIUM-II HALO MERGER TREES

    SciTech Connect

    Walker-Soler, Jean P.; Gawiser, Eric; Bond, Nicholas A.; Padilla, Nelson; Francke, Harold

    2012-06-20

    Using the Millennium-II Simulation dark matter sub-halo merger histories, we created mock catalogs of Ly{alpha}-emitting (LAE) galaxies at z = 3.1 to study the properties of their descendants. Several models were created by selecting the sub-halos to match the number density and typical dark matter mass determined from observations of these galaxies. We used mass-based and age-based selection criteria to study their effects on descendant populations at z {approx_equal} 2, 1, and 0. For the models that best represent LAEs at z = 3.1, the z = 0 descendants have a median dark matter halo mass of 10{sup 12.7} M{sub Sun }, with a wide scatter in masses (50% between 10{sup 11.8} and 10{sup 13.7} M{sub Sun }). Our study differentiated between central and satellite sub-halos and found that {approx}55% of z = 0 descendants are central sub-halos with M{sub Median} {approx} 10{sup 12}. This confirms that central z = 0 descendants of z = 3.1 LAEs have halo masses typical of L*-type galaxies. The satellite sub-halos reside in group/cluster environments with dark matter masses around 10{sup 14} M{sub Sun }. The median descendant mass is robust to various methods of age determination, but it could vary by a factor of five due to current observational uncertainties in the clustering of LAEs used to determine their typical z = 3.1 dark matter mass.

  15. INFERENCES ON THE DISTRIBUTION OF Ly{alpha} EMISSION OF z {approx} 7 AND z {approx} 8 GALAXIES

    SciTech Connect

    Treu, Tommaso; Auger, Matthew W.; Trenti, Michele; Stiavelli, Massimo; Bradley, Larry D.

    2012-03-01

    Spectroscopic confirmation of galaxies at z {approx} 7 and above has been extremely difficult, owing to a drop in intensity of Ly{alpha} emission in comparison with samples at z {approx} 6. This crucial finding could potentially signal the ending of cosmic reionization. However, it is based on small data sets, often incomplete and heterogeneous in nature. We introduce a flexible Bayesian framework, useful to interpret such evidence. Within this framework, we implement two simple phenomenological models: a smooth one where the distribution of Ly{alpha} is attenuated by a factor {epsilon}{sub s} with respect to z {approx} 6 and a patchy one where a fraction {epsilon}{sub p} is absorbed/non-emitted while the rest is unabsorbed. From a compilation of 39 observed z {approx} 7 galaxies, we find {epsilon}{sub s} = 0.69 {+-} 0.12 and {epsilon}{sub p} = 0.66 {+-} 0.16. The models can be used to compute fractions of emitters above any equivalent width W. For W > 25 A, we find X{sup 25}{sub z=7} = 0.37 {+-} 0.11 (0.14 {+-} 0.06) for galaxies fainter (brighter) than M{sub UV} = -20.25 for the patchy model, consistent with previous work, but with smaller uncertainties by virtue of our full use of the data. At z {approx} 8 we combine new deep (5{sigma} flux limit 10{sup -17} erg s{sup -1} cm{sup -2}) Keck/NIRSPEC observations of a bright Y-dropout identified by our Brightest of Reionization Galaxies Survey, with those of three objects from the literature and find that the inference is inconclusive. We compute predictions for future near-infrared spectroscopic surveys and show that it is challenging but feasible to constrain the distribution of Ly{alpha} emitters at z {approx} 8 and distinguish between models.

  16. EVOLUTION IN THE CONTINUUM MORPHOLOGICAL PROPERTIES OF Ly{alpha}-EMITTING GALAXIES FROM z = 3.1 TO z = 2.1

    SciTech Connect

    Bond, Nicholas A.; Gawiser, Eric; Guaita, Lucia; Padilla, Nelson; Gronwall, Caryl; Ciardullo, Robin; Lai, Kamson

    2012-07-10

    We present a rest-frame ultraviolet morphological analysis of 108 z {approx_equal} 2.1 Ly{alpha} emitters (LAEs) in the Extended Chandra Deep Field South and compare it to a similar sample of 171 LAEs at z {approx_equal} 3.1. Using Hubble Space Telescope images from the Galaxy Evolution from Morphology and SEDs survey, Great Observatories Origins Deep Survey, and Hubble Ultradeep Field, we measure size and photometric component distributions, where photometric components are defined as distinct clumps of UV-continuum emission. At both redshifts, >80% of LAEs have observed half-light radii <2 kpc, but the median half-light radius rises from 0.95 {+-} 0.04 kpc at z 3.1 to 1.41 {+-} 0.14 kpc at z = 2.1. A similar evolution is seen in the sizes of individual rest-UV components, but there is no evidence for evolution in the number of multi-component systems. In the z = 2.1 sample, we see clear correlations between the size of an LAE and other physical properties derived from its spectral energy distribution (SED). LAEs are found to be larger for galaxies with higher stellar mass, star formation rate, and dust obscuration, but there is no evidence for a trend between equivalent width and half-light radius at either redshift. The presence of these correlations suggests that a wide range of objects are being selected by LAE surveys at z {approx} 2, including a significant fraction of objects for which a massive and moderately extended population of old stars underlies the young starburst giving rise to the Ly{alpha} emission.

  17. He II lambda 1640/lambda 4686 and Ly-alpha/H-beta ratios in the extraordinary Seyfert galaxy Markarian 359

    NASA Technical Reports Server (NTRS)

    Macalpine, G. M.; Davidson, K.; Gull, T. R.; Wu, C.-C.

    1985-01-01

    The exceptionally narrow-lined Seyfert 1 galaxy Mrk 359 is ideally suited for determining reddening via the He II lambda 1640/lambda 4686 emission-line ratio. Here the validity of He II lines as a reddening indicator for quasars and Seyfert galaxies is reexamined and confirmed in the context of the most complete photoionization models available. In addition, lambda 1640 equivalent width measurements are shown to support previous contentions of substantial differences between observed and intrinsic quasar far-ultraviolet continua. Then IUE satellite and ground-based spectral data are presented, with the surprising result that both the lambda 1640/lambda 4686 and Ly-alpha/H-beta ratios do not differ greatly from case B recombination values in Mrk 359. This object is only slightly reddened, and it shows no evidence for extended, high-optical-depth H(+)/H(0) transition regions in the line-emitting gas. The very narrow lines and lack of deep transition regions and/or reddening may be related. In addition, Mrk 359 has low luminosity compared with most other Seyfert 1 galaxies, measured emission lines suggest an unusually high ionization parameter, and there is a hint of low nitrogen abundance. Further work is needed to examine possible relationships among all these peculiar properties.

  18. The Evolution of Ly-alpha Emitting Galaxies Between z = 2.1 and z = 3.l

    NASA Technical Reports Server (NTRS)

    Ciardullo, Robin; Gronwall,Caryl; Wolf, Christopher; McCathran, Emily; Bond, Nicholas A.; Gawiser, Eric; Guaita, Lucia; Feldmeier, John J.; Treister, Ezequiel; Padilla, Nelson; Francke, Harold; Matkovic, Ana; Altmann, Martin; Herrera, David

    2011-01-01

    We describe the results of a new, wide-field survey for z= 3.1 Ly-alpha emission-line galaxies (LAEs) in the Extended Chandra Deep Field South (ECDF-S). By using a nearly top-hat 5010 Angstrom filter and complementary broadband photometry from the MUSYC survey, we identify a complete sample of 141 objects with monochromatic fluxes brighter than 2.4E-17 ergs/cm^2/s and observers-frame equivalent widths greater than 80 Angstroms (i.e., 20 Angstroms in the rest-frame of Ly-alpha). The bright-end of this dataset is dominated by x-ray sources and foreground objects with GALEX detections, but when these interlopers are removed, we are still left with a sample of 130 LAE candidates, 39 of which have spectroscopic confirmations. This sample overlaps the set of objects found in an earlier ECDF-S survey, but due to our filter's redder bandpass, it also includes 68 previously uncataloged sources. We confirm earlier measurements of the z=3.1 LAE emission-line luminosity function, and show that an apparent anti-correlation between equivalent width and continuum brightness is likely due to the effect of correlated errors in our heteroskedastic dataset. Finally, we compare the properties of z=3.1 LAEs to LAEs found at z=2.1. We show that in the approximately 1 Gyr after z approximately 3, the LAE luminosity function evolved significantly, with L * fading by approximately 0.4 mag, the number density of sources with L greater than 1.5E42 ergs/s declining by approximately 50%, and the equivalent width scalelength contracting from 70^{+7}_{-5} Angstroms to 50^{+9}_{-6} Angstroms. When combined with literature results, our observations demonstrate that over the redshift range z approximately 0 to z approximately 4, LAEs contain less than approximately 10% of the star-formation rate density of the universe.

  19. STATISTICS OF 207 Ly{alpha} EMITTERS AT A REDSHIFT NEAR 7: CONSTRAINTS ON REIONIZATION AND GALAXY FORMATION MODELS

    SciTech Connect

    Ouchi, Masami; Ota, Kazuaki; Shimasaku, Kazuhiro; Yoshida, Makiko; Ono, Yoshiaki; Okamura, Sadanori; Furusawa, Hisanori; Kashikawa, Nobunari; Iye, Masanori; Kodama, Tadayuki; Saito, Tomoki; Akiyama, Masayuki; Yamada, Toru; Simpson, Chris; Yoshida, Michitoshi

    2010-11-01

    We present the Ly{alpha} luminosity function (LF), clustering measurements, and Ly{alpha} line profiles based on the largest sample to date of 207 Ly{alpha} emitters (LAEs) at z = 6.6 on the 1 deg{sup 2} sky of Subaru/XMM-Newton Deep Survey field. Our z = 6.6 Ly{alpha} LF including cosmic variance estimates yields the best-fit Schechter parameters of {phi}* = 8.5{sup +3.0}{sub -2.2} x 10{sup -4} Mpc{sup -3} and L*{sub Ly{alpha}} = 4.4{sup +0.6}{sub -0.6} x 10{sup 42} erg s{sup -1} with a fixed {alpha} = -1.5, and indicates a decrease from z = 5.7 at the {approx}>90% confidence level. However, this decrease is not large, only {approx_equal}30% in Ly{alpha} luminosity, which is too small to have been identified in the previous studies. A clustering signal of z = 6.6 LAEs is detected for the first time. We obtain the correlation length of r{sub 0}= 2-5 h {sup -1}{sub 100} Mpc and a bias of b= 3-6, and find no significant boost of clustering amplitude by reionization at z = 6.6. The average hosting dark halo mass inferred from clustering is 10{sup 10}-10{sup 11} M{sub sun}, and a duty cycle of LAE population is roughly {approx}1%, albeit with large uncertainties. The average of our high-quality Keck/DEIMOS spectra shows an FWHM velocity width of 251 {+-} 16 km s{sup -1}. We find no large evolution of the Ly{alpha} line profile from z = 5.7 to 6.6, and no anti-correlation between Ly{alpha} luminosity and line width at z = 6.6. The combination of various reionization models and our observational results about the LF, clustering, and line profile indicates that there would exist a small decrease of the intergalactic medium's (IGM's) Ly{alpha} transmission owing to reionization, but that the hydrogen IGM is not highly neutral at z = 6.6. Our neutral-hydrogen fraction constraint implies that the major reionization process took place at z {approx}> 7.

  20. PHYSICAL PROPERTIES OF SPECTROSCOPICALLY CONFIRMED GALAXIES AT z {>=} 6. II. MORPHOLOGY OF THE REST-FRAME UV CONTINUUM AND Ly{alpha} EMISSION

    SciTech Connect

    Jiang Linhua; Windhorst, Rogier A.; Cohen, Seth H.; Mechtley, Matthew; Egami, Eiichi; Fan Xiaohui; Dave, Romeel; Finlator, Kristian; Kashikawa, Nobunari; Ouchi, Masami; Shimasaku, Kazuhiro

    2013-08-20

    We present a detailed structural and morphological study of a large sample of spectroscopically confirmed galaxies at z {>=} 6 using deep Hubble Space Telescope (HST) near-IR broad-band images and Subaru Telescope optical narrow-band images. The galaxy sample consists of 51 Ly{alpha} emitters (LAEs) at z {approx_equal} 5.7, 6.5, and 7.0, and 16 Lyman break galaxies (LBGs) at 5.9 {<=} z {<=} 6.5. These galaxies exhibit a wide range of rest-frame UV continuum morphology in the HST images, from compact features to multiple component systems. The fraction of merging/interacting galaxies reaches 40%-50% at the brightest end of M{sub 1500} {<=} -20.5 mag. The intrinsic half-light radii r{sub hl,in}, after correcting for point-spread function (PSF) broadening, are roughly between r{sub hl,in} {approx_equal} 0.''05 (0.3 kpc) and 0.''3 (1.7 kpc) at M{sub 1500} {<=} -19.5 mag. The median r{sub hl,in} value is 0.''16 ({approx}0.9 kpc). This is consistent with the sizes of bright LAEs and LBGs at z {>=} 6 found in previous studies. In addition, more luminous galaxies tend to be larger and exhibit a weak size-luminosity relation, r{sub hl,in}{proportional_to}L {sup 0.14} at M{sub 1500} {<=} -19.5 mag. The slope of 0.14 is significantly flatter than those in fainter LBG samples. We discuss the morphology of z {>=} 6 galaxies with nonparametric methods, including the concentration, asymmetry, and smoothness system and the Gini and M{sub 20} parameters, and demonstrate their validity through simulations. We search for extended Ly{alpha} emission halos around LAEs at z {approx_equal} 5.7 and 6.5 by stacking a number of narrow-band images. We do not find evidence of extended Ly{alpha} halos predicted by cosmological simulations. Such halos, if they exist, could be weaker than predicted. Finally, we investigate positional misalignment between the UV continuum and Ly{alpha} emissions in LAEs. While the two positions are generally consistent, several merging galaxies show significant

  1. PHYSICAL PROPERTIES OF SPECTROSCOPICALLY CONFIRMED GALAXIES AT z {>=} 6. I. BASIC CHARACTERISTICS OF THE REST-FRAME UV CONTINUUM AND Ly{alpha} EMISSION

    SciTech Connect

    Jiang Linhua; Mechtley, Matthew; Cohen, Seth H.; Windhorst, Rogier A.; Egami, Eiichi; Fan Xiaohui; Dave, Romeel; Finlator, Kristian; Kashikawa, Nobunari; Ouchi, Masami; Shimasaku, Kazuhiro

    2013-08-01

    We present deep Hubble Space Telescope near-IR and Spitzer mid-IR observations of a large sample of spectroscopically confirmed galaxies at z {>=} 6. The sample consists of 51 Ly{alpha} emitters (LAEs) at z {approx_equal} 5.7, 6.5, and 7.0, and 16 Lyman break galaxies (LBGs) at 5.9 {<=} z {<=} 6.5. The near-IR images were mostly obtained with WFC3 in the F125W and F160W bands, and the mid-IR images were obtained with IRAC in the 3.6 {mu}m and 4.5 {mu}m bands. Our galaxies also have deep optical imaging data from Subaru Suprime-Cam. We utilize the multi-band data and secure redshifts to derive their rest-frame UV properties. These galaxies have steep UV-continuum slopes roughly between {beta} {approx_equal} -1.5 and -3.5, with an average value of {beta} {approx_equal} -2.3, slightly steeper than the slopes of LBGs in previous studies. The slope shows little dependence on UV-continuum luminosity except for a few of the brightest galaxies. We find a statistically significant excess of galaxies with slopes around {beta} {approx_equal} -3, suggesting the existence of very young stellar populations with extremely low metallicity and dust content. Our galaxies have moderately strong rest-frame Ly{alpha} equivalent width (EW) in a range of {approx}10 to {approx}200 A. The star formation rates are also moderate, from a few to a few tens of solar masses per year. The LAEs and LBGs in this sample share many common properties, implying that LAEs represent a subset of LBGs with strong Ly{alpha} emission. Finally, the comparison of the UV luminosity functions between LAEs and LBGs suggests that there exists a substantial population of faint galaxies with weak Ly{alpha} emission (EW < 20 A) that could be the dominant contribution to the total ionizing flux at z {>=} 6.

  2. GAS KINEMATICS IN Ly{alpha} NEBULAE

    SciTech Connect

    Yang Yujin; Jahnke, Knud; Zabludoff, Ann; Eisenstein, Daniel; Dave, Romeel; Shectman, Stephen A.; Kelson, Daniel D.

    2011-07-10

    Exploring the origin of Ly{alpha} nebulae ('blobs') at high redshift requires measurements of their gas kinematics that are impossible with only the resonant, optically thick Ly{alpha} line. To define gas motions relative to the systemic velocity of the blob, the Ly{alpha} line must be compared with an optically thin line like H{alpha} {lambda}6563, which is not much altered by radiative transfer effects and is more concentrated about the galaxies embedded in the nebula's core. We obtain optical and near-IR (NIR) spectra of the two brightest Ly{alpha} blobs (CDFS-LAB01 and CDFS-LAB02) from the Yang et al. sample using the Magellan/Magellan Echellette Spectrograph optical and Very Large Telescope/SINFONI NIR spectrographs. Both the Ly{alpha} and H{alpha} lines confirm that these blobs lie at the survey redshift, z {approx} 2.3. Within each blob, we detect several H{alpha} sources, which roughly correspond to galaxies seen in Hubble Space Telescope rest-frame UV images. The H{alpha} detections show that these galaxies have large internal velocity dispersions ({sigma}{sub v} = 130-190 km s{sup -1}) and that, in the one system (LAB01), where we can reliably extract profiles for two H{alpha} sources, their velocity difference is {Delta}v {approx} 440 km s{sup -1}. The presence of multiple galaxies within the blobs, and those galaxies' large velocity dispersions and large relative motion, is consistent with our previous finding that Ly{alpha} blobs inhabit massive dark matter halos that will evolve into those typical of present-day rich clusters and that the embedded galaxies may eventually become brightest cluster galaxies. To determine whether the gas near the embedded galaxies is predominantly infalling or outflowing, we compare the Ly{alpha} and H{alpha} line centers, finding that Ly{alpha} is not offset ({Delta}v{sub Ly{alpha}} = +0 km s{sup -1}) in LAB01 and redshifted by only +230 km s{sup -1} in LAB02. These offsets are small compared to those of Lyman break

  3. AN ATLAS OF z = 5.7 AND z = 6.5 Ly{alpha} EMITTERS ,

    SciTech Connect

    Hu, E. M.; Cowie, L. L.; Barger, A. J.; Capak, P.; Kakazu, Y.; Trouille, L. E-mail: cowie@ifa.hawaii.ed E-mail: trouille@astro.wisc.ed E-mail: kakazu@astro.caltech.ed

    2010-12-10

    We present an atlas of 88 z {approx} 5.7 and 30 z {approx} 6.5 Ly{alpha} emitters obtained from a wide-field narrowband survey. We combined deep narrowband imaging in 120 A bandpass filters centered at 8150 A and 9140 A with deep BVRIz broadband imaging to select high-redshift galaxy candidates over an area of 4180 arcmin{sup 2}. The goal was to obtain a uniform selection of comparable depth over the seven targeted fields in the two filters. For the GOODS-North region of the Hubble Deep Field-North field, we also selected candidates using a 120 A filter centered at 9210 A. We made spectroscopic observations with Keck DEIMOS of nearly all the candidates to obtain the final sample of Ly{alpha} emitters. At the 3.3 A resolution of the DEIMOS observations the asymmetric profile for Ly{alpha} emission can be clearly seen in the spectra of nearly all the galaxies. We show that the spectral profiles are surprisingly similar for many of the galaxies and that the composite spectral profiles are nearly identical at z = 5.7 and z = 6.5. We analyze the distributions of line widths and Ly{alpha} equivalent widths and find that the lines are marginally narrower at the higher redshift, with median values of 0.77 A at z = 6.5 and 0.92 A at z = 5.7. The line widths have a dependence on the Ly{alpha} luminosity of the form {approx}L {sup 0.3}{sub {alpha}}. We compare the surface densities and the luminosity functions at the two redshifts and find that there is a multiplicative factor of two decrease in the number density of bright Ly{alpha} emitters from z = 5.7 to z = 6.5, while the characteristic luminosity is unchanged.

  4. A Search For Multiple Images of QSOs Seen Through Damped Ly-alpha Absorbers

    NASA Astrophysics Data System (ADS)

    Falco, Emilio

    1996-07-01

    We propose to obtain high-resolution images of a sample of QSOs with strong damped Ly-alpha absorption in their spectra. The observations would determine whether these QSOs are multiply imaged by gravitational lensing. It is widely believed that damped Ly-alpha absorption occurs in HI disks of spiral galaxies. Gravitational lensing is then inevitable for lines of sight passing close to the centers of these systems. For typical spiral galaxies, the resulting image separation is expected to be in the range 0.1''-0.5'' and can only be detected with HST at optical wavelengths. Because the neutral -hydrogen column density increases on average towards the center of galaxies, strong Ly-alpha absorption provides an efficient ``flag'' for gravitationally lensed QSOs with small image separations. Bartelmann & Loeb {1995, ApJ, in press} have shown that the frequency of multiple images is enhanced by 1-2 orders of magnitude in samples of QSOs with strong damped Ly-alpha absorption {N_ HI> 10^21 cm^-2}, compared to the overall QSO population. For this proposal, we have selected those QSOs most likely to exhibit gravitational lensing, from the published list of QSOs with damped Ly-alpha absorption. If lensing is found in this QSO sample, it will have important cosmological implications. First, it will confirm the association of damped Ly-alpha systems with galactic potential wells. Second, the magnification bias associated with lensing would make the appearance of damped systems more likely, and therefore affect estimates of the neutral-hydrogen fraction in the Universe {Bartelmann & Loeb 1995}. Third, the cosmological history of HI is linked to the process of galaxy formation and evolution {Lanzetta, Wolfe, & Turnshek 1995, ApJ, 440, 435}. Finally, the lensing frequency provides a sensitive probe of the cosmological constant.

  5. STELLAR POPULATIONS OF Ly{alpha} EMITTERS AT z {approx} 6-7: CONSTRAINTS ON THE ESCAPE FRACTION OF IONIZING PHOTONS FROM GALAXY BUILDING BLOCKS

    SciTech Connect

    Ono, Yoshiaki; Shimasaku, Kazuhiro; Okamura, Sadanori; Masami Ouchi; Dunlop, James; Farrah, Duncan; McLure, Ross

    2010-12-01

    We investigate the stellar populations of Ly{alpha} emitters (LAEs) at z = 5.7 and 6.6 in a 0.65 deg{sup 2} sky of the Subaru/XMM-Newton Deep Survey (SXDS) Field, using deep images taken with the Subaru/Suprime-Cam, United Kingdom Infrared Telescope/Wide Field Infrared Camera, and Spitzer/Infrared Array Camera (IRAC). We produce stacked multiband images at each redshift from 165 (z = 5.7) and 91 (z = 6.6) IRAC-undetected objects to derive typical spectral energy distributions (SEDs) of z {approx} 6-7 LAEs for the first time. The stacked LAEs have as blue UV continua as the Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) z-dropout galaxies of similar M{sub UV}, with a spectral slope {beta} {approx} -3, but at the same time they have red UV-to-optical colors with detection in the 3.6 {mu}m band. Using SED fitting we find that the stacked LAEs have low stellar masses of {approx}(3-10) x 10{sup 7} M{sub sun}, very young ages of {approx}1-3 Myr, negligible dust extinction, and strong nebular emission from the ionized interstellar medium, although the z = 6.6 object is fitted similarly well with high-mass models without nebular emission; inclusion of nebular emission reproduces the red UV-to-optical colors while keeping the UV colors sufficiently blue. We infer that typical LAEs at z {approx} 6-7 are building blocks of galaxies seen at lower redshifts. We find a tentative decrease in the Ly{alpha} escape fraction from z = 5.7 to 6.6, which may imply an increase in the intergalactic medium neutral fraction. From the minimum contribution of nebular emission required to fit the observed SEDs, we place an upper limit on the escape fraction of ionizing photons of f {sup ion}{sub esc} {approx} 0.6 at z = 5.7 and {approx}0.9 at z = 6.6. We also compare the stellar populations of our LAEs with those of stacked HST/WFC3 z-dropout galaxies.

  6. THE HETDEX PILOT SURVEY. II. THE EVOLUTION OF THE Ly{alpha} ESCAPE FRACTION FROM THE ULTRAVIOLET SLOPE AND LUMINOSITY FUNCTION OF 1.9 < z < 3.8 LAEs

    SciTech Connect

    Blanc, Guillermo A.; Adams, Joshua J.; Gebhardt, Karl; Hao Lei; Fry, Alexander B.; Jeong, Donghui; Komatsu, Eiichiro; Murphy, Jeremy D.; Hill, Gary J.; Drory, Niv; Bender, Ralf; Hopp, Ulrich; Kelzenberg, Ralf; Ciardullo, Robin; Gronwall, Caryl; Schneider, Donald P.; Finkelstein, Steven L.; Gawiser, Eric; MacQueen, Phillip; Roth, Martin M.

    2011-07-20

    We study the escape of Ly{alpha} photons from Ly{alpha} emitting galaxies (LAEs) and the overall galaxy population using a sample of 99 LAEs at 1.9 < z < 3.8 detected through integral-field spectroscopy of blank fields by The Hobby Eberly Telescope Dark Energy Experiment Pilot Survey. For 89 LAEs with broadband counterparts we measure ultraviolet (UV) luminosities and UV slopes, and estimate E(B - V) under the assumption of a constant intrinsic UV slope for LAEs. These quantities are used to estimate dust-corrected star formation rates (SFRs). Comparison between the observed Ly{alpha} luminosity and that predicted by the dust-corrected SFR yields the Ly{alpha} escape fraction. We also measure the Ly{alpha} luminosity function and luminosity density ({rho}{sub Ly{alpha}}) at 2 < z < 4. Using this and other measurements from the literature at 0.3 < z < 7.7 we trace the redshift evolution of {rho}{sub Ly{alpha}.} We compare it to the expectations from the star formation history of the universe and characterize the evolution of the Ly{alpha} escape fraction of galaxies. LAEs at 2 < z < 4 selected down to a luminosity limit of L(Ly{alpha}) > (3-6) x 10{sup 42} erg s{sup -1} (0.25-0.5 L*), have a mean (E(B - V)) = 0.13 {+-} 0.01, implying an attenuation of {approx}70% in the UV. They show a median UV uncorrected SFR = 11 M{sub sun} yr{sup -1}, dust-corrected SFR = 34 M{sub sun} yr{sup -1}, and Ly{alpha} equivalent widths (EWs) which are consistent with normal stellar populations. We measure a median Ly{alpha} escape fraction of 29%, with a large scatter and values ranging from a few percent to 100%. The Ly{alpha} escape fraction in LAEs correlates with E(B - V) in a way that is expected if Ly{alpha} photons suffer from similar amounts of dust extinction as UV continuum photons. This result implies that a strong enhancement of the Ly{alpha} EW with dust, due to a clumpy multi-phase interstellar medium (ISM), is not a common process in LAEs at these redshifts. It also

  7. Directly Imaging Damped Ly-Alpha Galaxies at Redshifts Greater Than 2. III: The Star Formation Rates of Neutral Gas Reservoirs at Redshifts of Approximately 2.7

    NASA Technical Reports Server (NTRS)

    Fumagalli, Michele; OMeara, John M.; Prochaska, J. Xavier; Rafelski, Marc; Kanekar, Nissim

    2014-01-01

    We present results from a survey designed to probe the star formation properties of 32 damped Ly alpha systems (DLAs) at redshifts of approximately 2.7. By using the "double-DLA" technique that eliminates the glare of the bright background quasars, we directly measure the rest-frame FUV flux from DLAs and their neighbouring galaxies. At the position of the absorbing gas, we place stringent constraints on the unobscured star formation rates (SFRs) of DLAs to 2 sigma limits of psi less than 0.09-0.27 solar mass yr(exp -1), corresponding to SFR surface densities sigma(sub sfr) less than 10(exp -2.6)-10(exp -1.5) solar mass yr(exp -1) kpc(exp -2). The implications of these limits for the star formation law, metal enrichment, and cooling rates of DLAs are examined. By studying the distribution of impact parameters as a function of SFRs for all the galaxies detected around these DLAs, we place new direct constraints on the bright end of the UV luminosity function of DLA hosts. We find that less than or equal to 13% of the hosts have psi greater than or equal to 2 solar mass yr(exp -1) at impact parameters b(sub dla) less than or equal to (psi/solar mass yr(exp -1))(exp 0.8) + 6 kpc, differently from current samples of confirmed DLA galaxies. Our observations also disfavor a scenario in which the majority of DLAs arise from bright LBGs at distances 20 less than or equal to b(sub dla) less than 100 kpc. These new findings corroborate a picture in which DLAs do not originate from highly star forming systems that are coincident with the absorbers, and instead suggest that DLAs are associated with faint, possibly isolated, star-forming galaxies. Potential shortcomings of this scenario and future strategies for further investigation are discussed.

  8. Ly{alpha} EMISSION FROM HIGH-REDSHIFT SOURCES IN COSMOS

    SciTech Connect

    Mallery, Ryan P.; Mobasher, Bahram; Hemmati, Shoubaneh; Capak, Peter; Kakazu, Yuko; Masters, Dan; Scoville, Nick; Scarlata, Claudia; Salvato, Mara; McCracken, Henry

    2012-12-01

    We investigate spectroscopically measured Ly{alpha} equivalent widths (EWs) and escape fractions of 244 sources of which 95 are Lyman break galaxies (LBGs) and 106 Lyman alpha emitters (LAEs) at z {approx} 4.2, z {approx} 4.8, and z {approx} 5.6 selected from intermediate and narrowband observations. The sources were selected from the Cosmic Evolution Survey and observed with the DEIMOS spectrograph. We find that the distribution of EWs shows no evolution with redshift for both the LBG selected sources and the intermediate/narrowband LAEs. We also find that the Ly{alpha} escape fraction of intermediate/narrowband LAEs is on average higher and has a larger variation than the escape fraction of LBG selected sources. The escape fraction does not show a dependence with redshift. Similar to what has been found for LAEs at low redshifts, the sources with the highest extinctions show the lowest escape fractions. The range of escape fractions increases with decreasing extinction. This is evidence that the dust extinction is the most important factor affecting the escape of Ly{alpha} photons, but at low extinctions other factors, such as the H I covering fraction and gas kinematics, can be just as effective at inhibiting the escape of Ly{alpha} photons.

  9. Nearby Galaxy Filaments and the Ly-alpha Forest: Confronting Simulations and the UV Background with Observations

    NASA Astrophysics Data System (ADS)

    Wakker, Bart P.; Hernandez, Audra K.; French, David M.; Kim, Tae-Sun; Oppenheimer, Benjamin D.; Savage, Blair D.

    2015-11-01

    Simulations of the formation of large-scale structures predict that dark matter, low density highly ionized gas, and galaxies form 10 to 40 Mpc scale filaments. These structures are easily recognized in the distribution of galaxies. Here we use Lyα absorption lines to study the gas in 30 × 6 Mpc filament at cz ˜ 3500 km s-1, defined using a new catalog of nearby (cz < 10,000 km s-1) galaxies, which is complete down to a luminosity of about 0.05 L* for the region of space analyzed here. Using Hubble Space Telescope spectra of 24 active galactic nuclei, we sample the gas in this filament. All of our sightlines pass outside the virial radius of any known filament galaxy. Within 500 kpc of the filament axis the detection rate is ˜80%, but no detections are seen more than 2.1 Mpc from the filament axis. The width of the Lyα lines correlates with filament impact parameter and the four BLAs in our sample occur within 400 kpc of the filament axis, indicating increased temperature and/or turbulence. Comparing to simulations, we find that the recent Haardt & Madau extragalactic ionizing background predicts a factor of 3-5 too few ionizing photons. Using a more intense radiation field matches the hydrogen density profile within 2.1 Mpc of the filament axis, but the simulations still overpredict the detection rate between 2.1 and 5 Mpc from the axis. The baryonic mass inside filament galaxies is 1.4 × 1013 M⊙, while the mass of filament gas outside galaxy halos is found to be 5.2 × {10}13 {M}⊙ . Based on observations taken by 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, Incorporated, under NASA contract NAS5-26555.

  10. NEW RESULTS FROM THE MAGELLAN IMACS SPECTROSCOPIC Ly{alpha} SURVEY: NICMOS OBSERVATIONS OF Ly{alpha} EMITTERS AT z = 5.7

    SciTech Connect

    Henry, Alaina L.; Martin, Crystal L.; Dressler, Alan; McCarthy, Patrick; Sawicki, Marcin

    2010-08-10

    We present NICMOS J {sub 110} (rest-frame 1200-2100 A) observations of the three z = 5.7 Ly{alpha} emitters discovered in the blind multislit spectroscopic survey by Martin et al. These images confirm the presence of the two sources that were previously only seen in spectroscopic observations. The third source, which is undetected in our J {sub 110} observations, has been detected in narrowband imaging of the Cosmic Origins Survey, so our non-detection implies a rest-frame equivalent width >146 A (3{sigma}). The two J {sub 110}-detected sources have more modest rest-frame equivalent widths of 30-40 A, but all three are typical of high-redshift Ly{alpha} emitters. In addition, the J {sub 110}-detected sources have UV luminosities that are within a factor of 2 of L*{sub UV}, and sizes that appear compact (r {sub hl{approx}} 0.''15) in our NIC2 images-consistent with a redshift of 5.7. We use these UV-continuum and Ly{alpha} measurements to estimate the i {sub 775}-z {sub 850} colors of these galaxies and show that at least one and possibly all three would be missed by the i-dropout Lyman break galaxy selection. These observations help demonstrate the utility of multislit narrowband spectroscopy as a technique for finding faint emission-line galaxies.

  11. HUBBLE SPACE TELESCOPE IMAGING OF Ly{alpha} EMISSION AT z {approx} 4.4

    SciTech Connect

    Finkelstein, Steven L.; Finkelstein, Keely D.; Cohen, Seth H.; Windhorst, Rogier A.; Malhotra, Sangeeta; Rhoads, James E.; Ryan, Russell E.; Hathi, Nimish P.; McCarthy, Patrick J.; Anderson, Jay; Grogin, Norman A.; Koekemoer, Anton M.; Mutchler, Max; Bond, Howard E.; O'Connell, Robert W.; Balick, Bruce; Calzetti, Daniela; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.

    2011-07-01

    We present the highest redshift detections of resolved Ly{alpha} emission, using Hubble Space Telescope (HST)/Advanced Camera for Surveys F658N narrowband-imaging data taken in parallel with the Wide Field Camera 3 Early Release Science program in the GOODS Chandra Deep Field-South. We detect Ly{alpha} emission from three spectroscopically confirmed z = 4.4 Ly{alpha} emitting galaxies (LAEs), more than doubling the sample of LAEs with resolved Ly{alpha} emission. Comparing the light distribution between the rest-frame ultraviolet continuum and narrowband images, we investigate the escape of Ly{alpha} photons at high redshift. While our data do not support a positional offset between the Ly{alpha} and rest-frame ultraviolet (UV) continuum emission, the half-light radius in one out of the three galaxies is significantly (>1{sigma}) larger in Ly{alpha} than in the rest-frame UV continuum. Stacking the three LAEs in both the narrowband and UV continuum images, we find that the Ly{alpha} light appears larger than the rest-frame UV at 4.2{sigma} significance. This Ly{alpha} flux detected with HST is a factor of 4-10 less than observed in similar filters from the ground. These results together imply that the Ly{alpha} emission is not strictly confined to its indigenous star-forming regions. Rather, for at least one object the Ly{alpha} emission is more extended, with the missing HST flux possibly existing in a diffuse outer halo. This suggests that the radiative transfer of Ly{alpha} photons in high-redshift LAEs is complicated, with the interstellar-medium geometry and/or outflows playing a significant role in galaxies at these redshifts.

  12. The solar Ly-alpha line profile

    NASA Technical Reports Server (NTRS)

    Woods, Thomas N.; Rottman, Gary J.; White, O. R.; Fontenla, Juan; Avrett, E. H.

    1995-01-01

    Solar Ly-alpha irradiance measurements from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) on the Upper Atmosphere Research Satellite (UARS) have been made since 1991 October with a spectral resolution of 0.1 nm. The uniqueness of the small molecular oxygen cross section near Ly-alpha permits the Ly-alpha radiation to penetrate much deeper into the atmosphere than the other emissions near Ly-alpha. We have taken advantage of this phenomenon by performing solar occultation experiments near the Ly-alpha to evaluate precisely the instrument scattered light contribution. After correcting for scattered light, the broad wings of the solar Ly-alpha line can be extracted out to 5 nm from line center with a typical accuracy of +/-20%. The variability in the Ly-alpha wings near 2 nm from line center is about one-half that of the Ly-alpha core emission, defined within 0.1 nm from line center. These Ly-alpha profile measurements are found to be consistent with the Skylab radiance measurements and theoretical models of the Ly-alpha line profiles computed using partial redistribution of photons in the source function.

  13. Spectral Energy Distribution Fitting of Hetdex Pilot Survey Ly-alpha Emitters in Cosmos and Goods-N

    NASA Technical Reports Server (NTRS)

    Hagen, Alex; Ciardullo, Robin; Cronwall, Caryl; Acquaviva, Viviana; Bridge, Joanna; Zeimann, Gregory R.; Blanc, Guillermo; Bond, Nicholas; Finkelstein, Steven L.; Song, Mimi; Gawiser, Eric; Fox, Derek B.; Gebhardt, Henry; Malz, A. I; Schneider, Donald P.; Drory, Niv; Gebhardt, Karl; Hill, Gary J.

    2014-01-01

    We use broadband photometry extending from the rest-frame UV to the near-IR to fit the individual spectral energy distributions of 63 bright (L(Ly-alpha) greater than 10(exp 43) erg s(exp -1) Ly-alpha emitting galaxies (LAEs) in the redshift range 1.9 less than z less than 3.6. We find that these LAEs are quite heterogeneous, with stellar masses that span over three orders of magnitude, from 7.5 greater than logM/solar mass less than 10.5. Moreover, although most LAEs have small amounts of extinction, some high-mass objects have stellar reddenings as large as E(B - V ) is approximately 0.4. Interestingly, in dusty objects the optical depths for Ly-alpha and the UV continuum are always similar, indicating that Lya photons are not undergoing many scatters before escaping their galaxy. In contrast, the ratio of optical depths in low-reddening systems can vary widely, illustrating the diverse nature of the systems. Finally, we show that in the star-formation-rate-log-mass diagram, our LAEs fall above the "main-sequence" defined by z is approximately 3 continuum selected star-forming galaxies. In this respect, they are similar to submillimeter-selected galaxies, although most LAEs have much lower mass.

  14. FILAMENTARY LARGE-SCALE STRUCTURE TRACED BY SIX Ly{alpha} BLOBS AT z = 2.3

    SciTech Connect

    Erb, Dawn K.; Bogosavljevic, Milan; Steidel, Charles C.

    2011-10-10

    Extended nebulae of Ly{alpha} emission ('Ly{alpha} blobs') are known to be associated with overdense regions at high redshift. Here we present six large Ly{alpha} blobs in a previously known protocluster with galaxy overdensity {delta} {approx} 7 at z = 2.3; this is the richest field of giant Ly{alpha} blobs detected to date. The blobs have linear sizes of {approx}> 100 kpc and Ly{alpha} luminosities of {approx}10{sup 43} erg s{sup -1}. The positions of the blobs define two linear filaments with an extent of at least 12 comoving Mpc; these filaments intersect at the center of one of the blobs. Measurement of the position angles of the blobs indicates that five of the six are aligned with these filaments to within {approx}10{sup 0}, suggesting a connection between the physical processes powering extended Ly{alpha} emission and those driving structure on larger scales.

  15. THE LUMINOSITY FUNCTION OF Ly{alpha} EMITTERS AT REDSHIFT z = 7.7

    SciTech Connect

    Tilvi, Vithal; Rhoads, James E.; Hibon, Pascale; Malhotra, Sangeeta; Wang Junxian; Veilleux, Sylvain; Swaters, Rob; Krug, Hannah; Probst, Ron; Dickinson, Mark; Finkelstein, Steven L.

    2010-10-01

    Ly{alpha} emission lines should be attenuated in a neutral intergalactic medium. Therefore, the visibility of Ly{alpha} emitters at high redshifts can serve as a valuable probe of reionization at about the 50% level. We present an imaging search for z = 7.7 Ly{alpha} emitting galaxies using an ultra-narrowband filter (filter width = 9 A) on the NEWFIRM imager at the Kitt Peak National Observatory. We found four candidate Ly{alpha} emitters in a survey volume of 1.4x10{sup 4} Mpc{sup 3}, with a line flux brighter than 6 x 10{sup -18} erg cm{sup -2} s{sup -1} (5{sigma} in 2'' aperture). We also performed a detailed Monte Carlo simulation incorporating the instrumental effects to estimate the expected number of Ly{alpha} emitters in our survey and found that we should expect to detect one Ly{alpha} emitter, assuming a non-evolving Ly{alpha} luminosity function (LF) between z = 6.5 and z = 7.7. Even if one of the present candidates is spectroscopically confirmed as a z {approx} 8 Ly{alpha} emitter, it would indicate that there is no significant evolution of the Ly{alpha} LF from z = 3.1 to z {approx} 8. While firm conclusions would need both spectroscopic confirmations and larger surveys to boost the number counts of galaxies, we successfully demonstrate the feasibility of sensitive near-infrared (1.06 {mu}m) narrowband searches using custom filters designed to avoid the OH emission lines that make up most of the sky background.

  16. HUBBLE SPACE TELESCOPE NARROWBAND SEARCH FOR EXTENDED Ly{alpha} EMISSION AROUND TWO z > 6 QUASARS

    SciTech Connect

    Decarli, Roberto; Walter, Fabian; Yang Yujin; Hennawi, Joseph F.; Rix, Hans-Walter; Venemans, Bram P.; Carilli, Chris L.; Fan Xiahoui; Kurk, Jaron; Riechers, Dominik; Strauss, Michael A.

    2012-09-10

    We search for extended Ly{alpha} emission around two z > 6 quasars, SDSS J1030+0524 (z = 6.309) and SDSS J1148+5251 (z = 6.419) using Wide Field Camera 3 narrowband filters on board the Hubble Space Telescope. For each quasar, we collected two deep, narrowband images, one sampling the Ly{alpha} line+continuum at the quasar redshifts and one of the continuum emission redward of the line. After carefully modeling the point-spread function, we find no evidence for extended Ly{alpha} emission. These observations set 2{sigma} limits of L(Ly{alpha}, extended) <3.2 Multiplication-Sign 10{sup 44} erg s{sup -1} for J1030+0524 and L(Ly{alpha}, extended) <2.5 Multiplication-Sign 10{sup 44} erg s{sup -1} for J1148+5251. Given the star formation rates typically inferred from (rest-frame) far-infrared measurements of z {approx} 6 quasars, these limits are well below the intrinsic bright Ly{alpha} emission expected from the recombination of gas photoionized by the quasars or by the star formation in the host galaxies, and point toward significant Ly{alpha} suppression or dust attenuation. However, small extinction values have been observed along the line of sight to the nuclei, thus reddening has to be coupled with other mechanisms for Ly{alpha} suppression (e.g., resonance scattering). No Ly{alpha} emitting companions are found, down to a 5{sigma} sensitivity of {approx}1 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} arcsec{sup -2} (surface brightness) and {approx}5 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} (assuming point sources).

  17. Magnetic fields in damped Ly-alpha systems

    NASA Technical Reports Server (NTRS)

    Wolfe, A. M.; Lanzetta, K. M.; Oren, A. L.

    1992-01-01

    The probability of Faraday rotation in various types of metal-line absorbers is computed by combining the incidence of Faraday rotation in a sample of radio-selected QSOs with the incidence of foreground metal-line absorption. The sample is divided into subsets with and without damped Ly-alpha absorption. The probability of Faraday rotation is significantly higher in the damped subset. The probability is higher in the damped subset than in nondamped subsets selected on the basis of Mg II or C IV absorption. From evidence linking damped systems to the progenitors of galactic disks and the Mg II systems to the progenitors of galactic halos, it is concluded that magnetic fields were significantly higher in protogalactic disks than in protogalactic halos. It is estimated that the B fields in two damped Ly-alpha systems with z of about 2 are a few micro-Gauss.

  18. Evolution in the Continuum Morphological Properties of Ly alpha-Emitting Galaxies from Z=3.1 to Z=2.1

    NASA Technical Reports Server (NTRS)

    Bond, Nicholas A.; Gawiser, Eric; Guaita, Lucia; Padilla, Nelson; Gronwall, Chile Caryl; Ciardullo, Robin; Lai, Kamson

    2011-01-01

    We present a rest-frame ultraviolet morphological analysis of 108 z = 2.1 Lyman Alpha Emitters (LAEs) in the Extended Chandra Deep Field South (ECDF-S) and compare it to a similar sample of 171 LAEs at z = 3.1 . Using Hubble Space Telescope (HST) images taken as part of the Galaxy Evolution From Morphology and SEDs survey, Great Observatories Origins Deep Survey, and Hubble Ultradeep Field surveys, we measure the size and photometric component distributions, where photo- metric components are defined as distinct clumps of UV-continuum emission. At both redshifts, the majority of LAEs have observed half-light radii < 2 kpc, but the median half-light radius rises from 0.97 kpc at z = 3.1 to 1.41 kpc at z = 2.1. A similar evolution is seen in the sizes of individual rest-UV components, but there is no evidence for evolution in the number of mUlti-component systems. In the z = 2.1 LAE sample, we see clear correlations between the LAE size and other physical properties derived from its SED. LAEs are found to be larger for galaxies with larger stellar mass, larger star formation rate, and larger dust obscuration, but there is no evidence for a trend between equivalent width and half-light radius at either redshift. The presence of these correlations suggests that a wide range of objects are being selected by LAE surveys at that redshift, including a significant fraction of objects for which a massive and moderately extended population of old stars underlies the young starburst giving rise to the Lya emission.

  19. Ly{alpha} RADIATIVE TRANSFER IN COSMOLOGICAL SIMULATIONS USING ADAPTIVE MESH REFINEMENT

    SciTech Connect

    Laursen, Peter; Razoumov, Alexei O.; Sommer-Larsen, Jesper E-mail: razoumov@ap.smu.ca

    2009-05-01

    A numerical code for solving various Ly{alpha} radiative transfer (RT) problems is presented. The code is suitable for an arbitrary, three-dimensional distribution of Ly{alpha} emissivity, gas temperature, density, and velocity field. Capable of handling Ly{alpha} RT in an adaptively refined grid-based structure, it enables detailed investigation of the effects of clumpiness of the interstellar (or intergalactic) medium. The code is tested against various geometrically and physically idealized configurations for which analytical solutions exist, and subsequently applied to three different simulated high-resolution 'Lyman-break galaxies', extracted from high-resolution cosmological simulations at redshift z = 3.6. Proper treatment of the Ly{alpha} scattering reveals a diversity of surface brightness (SB) and line profiles. Specifically, for a given galaxy the maximum observed SB can vary by an order of magnitude, and the total flux by a factor of 3-6, depending on the viewing angle. This may provide an explanation for differences in observed properties of high-redshift galaxies, and in particular a possible physical link between Lyman-break galaxies and regular Ly{alpha} emitters.

  20. INTENSITY MAPPING OF Ly{alpha} EMISSION DURING THE EPOCH OF REIONIZATION

    SciTech Connect

    Silva, Marta B.; Santos, Mario G.; Gong, Yan; Cooray, Asantha; Bock, James

    2013-02-15

    We calculate the absolute intensity and anisotropies of the Ly{alpha} radiation field present during the epoch of reionization. We consider emission from both galaxies and the intergalactic medium (IGM) and take into account the main contributions to the production of Ly{alpha} photons: recombinations, collisions, continuum emission from galaxies, and scattering of Lyn photons in the IGM. We find that the emission from individual galaxies dominates over the IGM with a total Ly{alpha} intensity (times frequency) of about (1.43-3.57) Multiplication-Sign 10{sup -8} erg s{sup -1} cm{sup -2} sr{sup -1} at a redshift of 7. This intensity level is low, so it is unlikely that the Ly{alpha} background during reionization can be established by an experiment aiming at an absolute background light measurement. Instead, we consider Ly{alpha} intensity mapping with the aim of measuring the anisotropy power spectrum that has rms fluctuations at the level of 1 Multiplication-Sign 10{sup -16} [erg s{sup -1} cm{sup -2} sr{sup -1}]{sup 2} at a few Mpc scales. These anisotropies could be measured with a spectrometer at near-IR wavelengths from 0.9 to 1.4 {mu}m with fields in the order of 0.5 to 1 deg{sup 2}. We recommend that existing ground-based programs using narrowband filters also pursue intensity fluctuations to study statistics on the spatial distribution of faint Ly{alpha} emitters. We also discuss the cross-correlation signal with 21 cm experiments that probe H I in the IGM during reionization. A dedicated sub-orbital or space-based Ly{alpha} intensity mapping experiment could provide a viable complimentary approach to probe reionization, when compared to 21 cm experiments, and is likely within experimental reach.

  1. X-RAY CONSTRAINTS ON THE Ly{alpha} ESCAPE FRACTION

    SciTech Connect

    Zheng Zhenya; Wang Junxian; Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, Steven L.; Gawiser, Eric; Gronwall, Caryl; Ciardullo, Robin; Guaita, Lucia; Nilsson, Kim K.

    2012-02-10

    We have co-added the X-ray flux of all known Ly{alpha} emitters (LAEs) in the 4 Ms Chandra Deep Field South (CDF-S) region, achieving the tightest upper limits yet on the X-ray to Ly{alpha} ratio. We use the X-ray data to place sensitive upper limits on the average unobscured star formation rate (SFR{sub X}) in these galaxies. A very small fraction of Ly{alpha} galaxies in the field are individually detected in the X-rays, implying a low fraction of active galactic nucleus activity. After excluding the few X-ray-detected LAEs, we stack the undetected LAEs located in the 4 Ms CDF-S data and 250 ks Extended CDF-S (ECDF-S) data, and compute a 1{sigma} upper limit on SFR{sub X} < 1.6, 14, 28, 28, 140, 440, 880 M{sub Sun} yr{sup -1} for LAEs located at z {approx} 0.3 and z = 2.1, 3.1, 3.2, 4.5, 5.7, and 6.5, respectively. The upper limit of SFR{sub X} in LAEs can be then compared to SFR{sub Ly{alpha}} derived from Ly{alpha} line and thus can constrain on the Ly{alpha} escape fraction (f{sup Esc}{sub Ly{alpha}}). The f{sup Esc}{sub Ly{alpha}} from X-ray at z {approx} 0.3 is substantially larger than that from UV or H{alpha}. Three X-ray-detected LAE galaxies at z {approx} 0.3 show f{sup Esc}{sub Ly{alpha}} {approx} 3%-22%, and the average Ly{alpha} escape fraction from stacking the X-ray-undetected LAEs show f{sup Esc}{sub Ly{alpha}} > 28% at 3{sigma} significance level at the same redshift. We derive a lower limit on f{sup Esc}{sub Ly{alpha}} > 14% (84% confidence level, 1{sigma} lower limit) for LAEs at redshift z {approx} 2.1 and z {approx} 3.1-3.2. At z > 4, the current LAE samples are not of sufficient size to constrain SFR{sub X} well. By averaging all the LAEs at z > 2, the X-ray non-detection constrains f{sup Esc}{sub Ly{alpha}} > 17% (84% confidence level, 1{sigma} lower limit), and rejects f{sup Esc}{sub Ly{alpha}} < 5.7% at the 99.87% confidence level from 2.1 < z < 6.5.

  2. THE FAINT-END SLOPE OF THE REDSHIFT 5.7 Ly{alpha} LUMINOSITY FUNCTION

    SciTech Connect

    Henry, Alaina L.; Martin, Crystal L.; Dressler, Alan; McCarthy, Patrick; Sawicki, Marcin

    2012-01-10

    Using new Keck DEIMOS spectroscopy, we examine the origin of the steep number counts of ultra-faint emission-line galaxies recently reported by Dressler et al. We confirm six Ly{alpha} emitters (LAEs), three of which have significant asymmetric line profiles with prominent wings extending 300-400 km s{sup -1} redward of the peak emission. With these six LAEs, we revise our previous estimate of the number of faint LAEs in the Dressler et al. survey. Combining these data with the density of bright LAEs in the Cosmic Evolution Survey and Subaru Deep Field provides the best constraints to date on the redshift 5.7 LAE luminosity function (LF). Schechter function parameters, {phi}* = 4.5 Multiplication-Sign 10{sup -4} Mpc{sup -3}, L* = 9.1 Multiplication-Sign 10{sup 42} erg s{sup -1}, and {alpha} = -1.70, are estimated using a maximum likelihood technique with a model for slit-losses. To place this result in the context of the UV-selected galaxy population, we investigate how various parameterizations of the Ly{alpha} equivalent width distribution, along with the measured UV-continuum LF, affect shape and normalization of the Ly{alpha} LF. The nominal model, which uses z {approx} 6 equivalent widths from the literature, falls short of the observed space density of LAEs at the bright end, possibly indicating a need for higher equivalent widths. This parameterization of the equivalent width distribution implies that as many as 50% of our faintest LAEs should have M{sub UV} > -18.0, rendering them undetectable in even the deepest Hubble Space Telescope surveys at this redshift. Hence, ultra-deep emission-line surveys find some of the faintest galaxies ever observed at the end of the reionization epoch. Such faint galaxies likely enrich the intergalactic medium with metals and maintain its ionized state in the post-reionization era. Observations of these objects provide a glimpse of the building blocks of present-day galaxies at an early time.

  3. A Ly{alpha} EMITTER WITH AN EXTREMELY LARGE REST-FRAME EQUIVALENT WIDTH OF {approx}900 A AT z = 6.5: A CANDIDATE POPULATION III-DOMINATED GALAXY?

    SciTech Connect

    Kashikawa, Nobunari; Hayashi, Masao; Iye, Masanori; Nagao, Tohru; Ota, Kazuaki; Toshikawa, Jun; Ishizaki, Yoshifumi; Shibuya, Takatoshi; Egami, Eiichi; Jiang, Linhua; Ly, Chun; Malkan, Matthew A.; Matsuda, Yuichi; Shimasaku, Kazuhiro; Taniguchi, Yoshiaki; Shioya, Yasuhiro

    2012-12-20

    We have identified a very interesting Ly{alpha} emitter (LAE), whose Ly{alpha} emission line has an extremely large observed equivalent width of EW{sub 0} = 436{sup +422}{sub -{sub 149}} A, which corresponds to an extraordinarily large intrinsic rest-frame equivalent width of EW{sup int}{sub 0} = 872{sup +844}{sub -{sub 298}} A after the average intergalactic absorption correction. The object was spectroscopically confirmed to be a real LAE by its apparent asymmetric Ly{alpha} line profile detected at z = 6.538. The continuum emission of the object was definitely detected in our deep z'-band image; thus, its EW{sub 0} was reliably determined. Follow-up deep near-infrared spectroscopy revealed emission lines of neither He II {lambda}1640 as an apparent signature of Population III (Pop III) nor C IV {lambda}1549 as proof of an active nucleus. No detection of the short-lived He II {lambda}1640 line is not necessarily inconsistent with the interpretation that the underlying stellar population of the object is dominated by Pop III. We found that the observed extremely large EW{sub 0} of the Ly{alpha} emission and the upper limit on the EW{sub 0} of the He II {lambda}1640 emission can be explained by population synthesis models favoring a very young age less than 2-4 Myr and massive metal-poor (Z < 10{sup -5}) or even metal-free stars. The observed large EW{sub 0} of Ly{alpha} is insufficiently explained by Population I/II synthesis models with Z {>=} 10{sup -3}. However, we cannot conclusively rule out the possibility that this object is composed of a normal stellar population with a clumpy dust distribution, which could enhance the Ly{alpha} EW{sub 0}, though its significance is still unclear.

  4. Extended Ly-alpha emission associated with 3C 294

    NASA Technical Reports Server (NTRS)

    Mccarthy, Patrick J.; Spinrad, Hyron; Dickinson, Mark; Van Breugel, Wil; Liebert, James; Djorgovski, S.; Eisenhardt, Peter

    1990-01-01

    Optical, IR, and radio observations of the powerful radio source 3C 294, which is surrounded by a large cloud of ionized gas, are presented. The galaxy is faint in the rest-frame UV, yet has a near-IR luminosity that is typical of radio galaxies at redshifts of order two. In contrast to the large extent of the ionized gas, the K-band image is quite compact. The emission-line cloud is closely aligned with the radio source axis and has an ionization state indicative of ionization by a nonstellar source. The velocity field of the gas has both large ordered motions and large turbulent components. The total mass required to keep the gas bound to the system is comparable to present-day massive galaxies and their halos. The velocity fields of the high-ionization lines are systematically different from Ly-alpha in a manner that is not easily understood.

  5. PROFILES OF Ly{alpha} EMISSION LINES OF THE EMITTERS AT z = 3.1

    SciTech Connect

    Yamada, T.; Morimoto, N.; Matsuda, Y.; Kousai, K.; Hayashino, T.; Umemura, M.

    2012-05-20

    We present the results of the observations of the Ly{alpha} line profiles of 91 emission-line galaxies at z = 3.1 with a spectral resolution of {lambda}/{delta}{lambda}(FWHM) Almost-Equal-To 1700 or 180 km s{sup -1}. A significant fraction of {approx}50% of the observed objects show the characteristic double peaks in their Ly{alpha} profile. The red peak is much stronger than the blue one for most of the cases. The red peaks themselves also show weak but significant asymmetry and their widths are correlated with the velocity separation of the red and the blue peaks. This implies that the peaks are not isolated multiple components with different velocities but parts of a single line that are modified by the absorption and/or scattering by the associated neutral hydrogen gas. The characteristic profile can be naturally explained by scattering in the expanding shell of the neutral hydrogen surrounding the Ly{alpha} emitting region while the attenuation by the intergalactic medium should also be considered. Our results suggest that the star formation in these Ly{alpha} emitters are dominated by young burst-like events that produce the intrinsic Ly{alpha} emission as well as the gas outflow.

  6. AVERAGE METALLICITY AND STAR FORMATION RATE OF Ly{alpha} EMITTERS PROBED BY A TRIPLE NARROWBAND SURVEY

    SciTech Connect

    Nakajima, Kimihiko; Shimasaku, Kazuhiro; Ono, Yoshiaki; Okamura, Sadanori; Ouchi, Masami; Lee, Janice C.; Ly, Chun; Foucaud, Sebastien; Dale, Daniel A.; Salim, Samir; Finn, Rose; Almaini, Omar

    2012-01-20

    We present the average metallicity and star formation rate (SFR) of Ly{alpha} emitters (LAEs) measured from our large-area survey with three narrowband (NB) filters covering the Ly{alpha}, [O II]{lambda}3727, and H{alpha}+[N II] lines of LAEs at z = 2.2. We select 919 z = 2.2 LAEs from Subaru/Suprime-Cam NB data in conjunction with Magellan/IMACS spectroscopy. Of these LAEs, 561 and 105 are observed with KPNO/NEWFIRM near-infrared NB filters whose central wavelengths are matched to redshifted [O II] and H{alpha} nebular lines, respectively. By stacking the near-infrared images of the LAEs, we successfully obtain average nebular-line fluxes of LAEs, the majority of which are too faint to be identified individually by NB imaging or deep spectroscopy. The stacked object has an H{alpha} luminosity of 1.7 Multiplication-Sign 10{sup 42} erg s{sup -1} corresponding to an SFR of 14 M{sub Sun} yr{sup -1}. We place, for the first time, a firm lower limit to the average metallicity of LAEs of Z {approx}> 0.09 Z{sub Sun} (2{sigma}) based on the [O II]/(H{alpha}+[N II]) index together with photoionization models and empirical relations. This lower limit of metallicity rules out the hypothesis that LAEs, so far observed at z {approx} 2, are extremely metal-poor (Z < 2 Multiplication-Sign 10{sup -2} Z{sub Sun }) galaxies at the 4{sigma} level. This limit is higher than a simple extrapolation of the observed mass-metallicity relation of z {approx} 2 UV-selected galaxies toward lower masses (5 Multiplication-Sign 10{sup 8} M{sub Sun }), but roughly consistent with a recently proposed fundamental mass-metallicity relation when the LAEs' relatively low SFR is taken into account. The H{alpha} and Ly{alpha} luminosities of our NB-selected LAEs indicate that the escape fraction of Ly{alpha} photons is {approx}12%-30%, much higher than the values derived for other galaxy populations at z {approx} 2.

  7. GAS MOTION STUDY OF Ly{alpha} EMITTERS AT z {approx} 2 USING FUV AND OPTICAL SPECTRAL LINES {sup ,}

    SciTech Connect

    Hashimoto, Takuya; Shimasaku, Kazuhiro; Nakajima, Kimihiko; Ouchi, Masami; Ono, Yoshiaki; Rauch, Michael; Janice Lee; Okamura, Sadanori

    2013-03-01

    We present the results of Magellan/MMIRS and Keck/NIRSPEC spectroscopy for five Ly{alpha} emitters (LAEs) at z {approx_equal} 2.2 for which high-resolution FUV spectra from Magellan/MagE are available. We detect nebular emission lines including H{alpha} on the individual basis and low-ionization interstellar (LIS) absorption lines in a stacked FUV spectrum, and measure average offset velocities of the Ly{alpha} line, {Delta}v {sub Ly{alpha}}, and LIS absorption lines, {Delta}v {sub abs}, with respect to the systemic velocity defined by the nebular lines. For a sample of eight z {approx} 2-3 LAEs without active galactic nucleus from our study and the literature, we obtain {Delta}v {sub Ly{alpha}} = 175 {+-} 35 km s{sup -1}, which is significantly smaller than that of Lyman-break Galaxies (LBGs), {Delta}v {sub Ly{alpha}} {approx_equal} 400 km s{sup -1}. The stacked FUV spectrum gives {Delta}v {sub abs} = -179 {+-} 73 km s{sup -1}, comparable to that of LBGs. These positive {Delta}v {sub Ly{alpha}} and negative {Delta}v {sub abs} suggest that LAEs also have outflows. In contrast to LBGs, however, the LAEs' {Delta}v {sub Ly{alpha}} is as small as |{Delta}v {sub abs}|, suggesting low neutral hydrogen column densities. Such a low column density with a small number of resonant scattering may cause the observed strong Ly{alpha} emission of LAEs. We find an anti-correlation between Ly{alpha} equivalent width (EW) and {Delta}v {sub Ly{alpha}} in a compilation of LAE and LBG samples. Although its physical origin is not clear, this anti-correlation result appears to challenge the hypothesis that a strong outflow, by means of a reduced number of resonant scattering, produces a large EW. If LAEs at z > 6 have similarly small {Delta}v {sub Ly{alpha}} values, constraints on the reionization history derived from the Ly{alpha} transmissivity may need to be revised.

  8. A NEW POPULATION OF HIGH-z, DUSTY Ly{alpha} EMITTERS AND BLOBS DISCOVERED BY WISE: FEEDBACK CAUGHT IN THE ACT?

    SciTech Connect

    Bridge, Carrie R.; Blain, Andrew; Borys, Colin J. K.; Griffith, Roger L.; Tsai, Chao-Wei; Petty, Sara; Farrah, Duncan; Benford, Dominic; Eisenhardt, Peter; Stern, Daniel; Wu Jingwen; Jarrett, Tom; Lonsdale, Carol; Stanford, Spencer A.; Wright, Edward L.

    2013-06-01

    By combining data from the NASA Wide-field Infrared Survey Explorer (WISE) mission with optical spectroscopy from the W. M. Keck telescope, we discover a mid-IR color criterion that yields a 78% success rate in identifying rare, typically radio-quiet, 1.6 {approx}< z {approx}< 4.6 dusty Ly{alpha} emitters (LAEs). Of these, at least 37% have emission extended on scales of 30-100 kpc and are considered Ly{alpha} ''blobs'' (LABs). The objects have a surface density of only {approx}0.1 deg{sup -2}, making them rare enough that they have been largely missed in deep, small area surveys. We measured spectroscopic redshifts for 92 of these galaxies, and find that the LAEs (LABs) have a median redshift of 2.3 (2.5). The WISE photometry coupled with data from Herschel (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) reveals that these galaxies are in the Hyper Luminous IR galaxy regime (L{sub IR} {approx}> 10{sup 13}-10{sup 14} L{sub Sun }) and have warm colors. They are typically more luminous and warmer than other dusty, z {approx} 2 populations such as submillimeter-selected galaxies and dust-obscured galaxies. These traits are commonly associated with the dust being illuminated by intense active galactic nucleus activity. We hypothesize that the combination of spatially extended Ly{alpha}, large amounts of warm IR-luminous dust, and rarity (implying a short-lived phase) can be explained if the galaxies are undergoing brief, intense ''feedback'' transforming them from an extreme dusty starburst/QSO into a mature galaxy.

  9. ON THE (NON-)ENHANCEMENT OF THE Ly{alpha} EQUIVALENT WIDTH BY A MULTIPHASE INTERSTELLAR MEDIUM

    SciTech Connect

    Laursen, Peter; Duval, Florent; Oestlin, Goeran

    2013-04-01

    It has been suggested that radiative transfer effects may explain the unusually high equivalent widths (EWs) of the Ly{alpha} line, observed occasionally from starburst galaxies, especially at high redshifts. If the dust is locked up inside high-density clouds dispersed in an empty intercloud medium, the Ly{alpha} photons could scatter off of the surfaces of the clouds, effectively having their journey confined to the dustless medium. The continuum radiation, on the other hand, does not scatter, and would thus be subject to absorption inside the clouds. This scenario is routinely invoked when Ly{alpha} EWs higher than what is expected theoretically are observed, although the ideal conditions under which the results are derived usually are not considered. Here we systematically examine the relevant physical parameters in this idealized framework, testing whether any astrophysically realistic scenarios may lead to such an effect. It is found that although clumpiness indeed facilitates the escape of Ly{alpha}, it is highly unlikely that any real interstellar media should result in a preferential escape of Ly{alpha} over continuum radiation. Other possible causes are discussed, and it is concluded that the observed high EWs are more likely to be caused by cooling radiation from cold accretion and/or anisotropic escape of the Ly{alpha} radiation.

  10. Clearings in Ly-alpha forests

    NASA Astrophysics Data System (ADS)

    Kovner, Israel; Rees, Martin J.

    1989-10-01

    At sufficient resolution, QSO spectra can be examined for patches of reduced H I column density in Ly-alpha clouds. Statistics of these clearings can constrain the fraction of the ionizing background contributed by compact sources and (possibly) their lifetimes and beaming. This is demonstrated first in a simple Euclidean setup and then in a model which takes into account the expansion of the universe and the cosmological evolution of the factors involved. The expected number of clearings in a Ly-alpha forest extending back to the formation epoch of compact sources of ionizing radiation (CSIRs) is about 1/4, if the CSIRs are important ionizing agents, and if the transience of CSIRs is unimportant. The particular properties of the CSIR population, e.g., their luminosity function, have little importance. However, expected number of clearings can be much larger if the CSIR lifetimes are short compared to the light crossing times of the domains of dominance, or if the CSIRs turned on sharply at a time when the ionization rate due to competing processes was low.

  11. WARM GAS IN THE VIRGO CLUSTER. I. DISTRIBUTION OF Ly{alpha} ABSORBERS

    SciTech Connect

    Yoon, Joo Heon; Putman, Mary E.; Bryan, Greg L.; Thom, Christopher; Chen, Hsiao-Wen

    2012-08-01

    The first systematic study of the warm gas (T = 10{sup 4-5} K) distribution across a galaxy cluster is presented using multiple background QSOs in and around the Virgo Cluster. We detect 25 Ly{alpha} absorbers (N{sub HI} = 10{sup 13.1-15.4} cm{sup -2}) in the Virgo velocity range toward 9 of 12 QSO sightlines observed with the Cosmic Origin Spectrograph, with a cluster impact parameter range of 0.36-1.65 Mpc (0.23-1.05 R{sub vir}). Including 18 Ly{alpha} absorbers previously detected by STIS or GHRS toward 7 of 11 background QSOs in and around the Virgo Cluster, we establish a sample of 43 absorbers toward a total of 23 background probes for studying the incidence of Ly{alpha} absorbers in and around the Virgo Cluster. With these absorbers, we find (1) warm gas is predominantly in the outskirts of the cluster and avoids the X-ray-detected hot intracluster medium (ICM). Also, Ly{alpha} absorption strength increases with cluster impact parameter. (2) Ly{alpha}-absorbing warm gas traces cold H I-emitting gas in the substructures of the Virgo Cluster. (3) Including the absorbers associated with the surrounding substructures, the warm gas covering fraction (100% for N{sub HI} > 10{sup 13.1} cm{sup -2}) is in agreement with cosmological simulations. We speculate that the observed warm gas is part of large-scale gas flows feeding the cluster both in the ICM and galaxies.

  12. Uranian H Ly-alpha emission - The interstellar wind source

    NASA Technical Reports Server (NTRS)

    Yelle, R. V.; Sandel, B. R.

    1986-01-01

    IUE observation of Uranian emissions in hydrogen Lyman alpha (H Ly-alpha) over the past four years have recently been summarized by Clarke et al. (1985). Over this time period they find an average H Ly-alpha brightness of 1260 R which they estimate is composed of 200 R of solar scattered radiation and 1060 R from a collisional source. A third component, not considered by previous authors, is the reflection of H Ly-alpha emissions from the interstellar wind. Hydrogen in the interstellar wind forms an extended source of H Ly-alpha whose importance relative to the solar flux increases with distance from the sun. The present paper demonstrates that scattering of interstellar H Ly-alpha is more important than scattering of solar H Ly-alpha for reasonable values of H column abundance and, in fact, may make up 10-40 percent of the observed signal. Large H column abundances are still required to explain the H Ly-alpha brightness solely on the basis of resonant scattering; therefore it is likely that the emissions are due in part to collisional sources and in part to the scattering of interstellar H Ly-alpha with solar scattering playing a minor role.

  13. Survey for z>3 damped Ly alpha absorption systems: the evolution of neutral gas

    NASA Technical Reports Server (NTRS)

    Storrie-Lombardi, L. J.; Wolfe, A. M.

    2000-01-01

    We have completed spectroscopic observations using LRIS on the Keck 1 telescope of 30 very high redshift quasars, 11 selected for the presence of damped Ly alpha absorption systems and 19 with redshifts z>3.5 not previously surveyed for absorption systems.

  14. COMPLETING THE CENSUS OF Ly{alpha} EMITTERS AT THE REIONIZATION EPOCH

    SciTech Connect

    Kashikawa, Nobunari; Iye, Masanori; Shimasaku, Kazuhiro; Okamura, Sadanori; Matsuda, Yuichi; Egami, Eiichi; Jiang, Linhua; Nagao, Tohru; Taniguchi, Yoshiaki; Shioya, Yasuhiro; Ouchi, Masami; Ota, Kazuaki; Malkan, Matthew A.; Hattori, Takashi; Ly, Chun; Furusawa, Hisanori; Shibuya, Takatoshi; Ishizaki, Yoshifumi; Toshikawa, Jun

    2011-06-20

    We carried out extended spectroscopic confirmations of Ly{alpha} emitters (LAEs) at z = 6.5 and 5.7 in the Subaru Deep Field. Now, the total number of spectroscopically confirmed LAEs is 45 and 54 at z = 6.5 and 5.7, respectively, and at least 81% (70%) of our photometric candidates at z = 6.5 (5.7) have been spectroscopically identified as real LAEs. We made careful measurements of the Ly{alpha} luminosity, both photometrically and spectroscopically, to accurately determine the Ly{alpha} and rest-UV luminosity functions (LFs). The substantially improved evaluation of the Ly{alpha} LF at z = 6.5 shows an apparent deficit from z = 5.7 at least at the bright end, and a possible decline even at the faint end, though small uncertainties remain. The rest-UV LFs at z = 6.5 and 5.7 are in good agreement, at least at the bright end, in clear contrast to the differences seen in the Ly{alpha} LF. These results imply an increase in the neutral fraction of the intergalactic medium from z = 5.7 to 6.5. The rest-frame equivalent width (EW{sub 0}) distribution at z = 6.5 seems to be systematically smaller than z = 5.7, and it shows an extended tail toward larger EW{sub 0}. The bright end of the rest-UV LF can be reproduced from the observed Ly{alpha} LF and a reasonable EW{sub 0}-UV luminosity relation. Integrating this rest-UV LF provides the first measurement of the contribution of LAEs to the photon budget required for reionization. The derived UV LF suggests that the fractional contribution of LAEs to the photon budget among Lyman break galaxies significantly increases toward faint magnitudes. Low-luminosity LAEs could dominate the ionizing photon budget, though this inference depends strongly on the uncertain faint-end slope of the Ly{alpha} LF.

  15. THE PROPAGATION OF Ly{alpha} IN EVOLVING PROTOPLANETARY DISKS

    SciTech Connect

    Bethell, Thomas J.; Bergin, Edwin A.

    2011-10-01

    We study the role resonant scattering plays in the transport of Ly{alpha} photons in accreting protoplanetary disk systems subject to varying degrees of dust settling. While the intrinsic stellar far-UV (FUV) spectrum of accreting T Tauri systems may already be dominated by a strong, broad Ly{alpha} line ({approx}80% of the FUV luminosity), we find that resonant scattering further enhances the Ly{alpha} density in the deep molecular layers of the disk. Ly{alpha} is scattered downward efficiently by the photodissociated atomic hydrogen layer that exists above the molecular disk. In contrast, FUV-continuum photons pass unimpeded through the photodissociation layer and (forward-)scatter inefficiently off dust grains. Using detailed, adaptive grid Monte Carlo radiative transfer simulations we show that the resulting Ly{alpha}/FUV-continuum photon density ratio is strongly stratified; FUV-continuum-dominated in the photodissociation layer and Ly{alpha}-dominated field in the molecular disk. The enhancement is greatest in the interior of the disk (r {approx} 1 AU) but is also observed in the outer disk (r {approx} 100 AU). The majority of the total disk mass is shown to be increasingly Ly{alpha} dominated as dust settles toward the midplane.

  16. The Local Ly(alpha) Forest: Association of Clouds with Superclusters and Voids

    NASA Technical Reports Server (NTRS)

    Stocke, John T.; Shull, J. Michael; Penton, Steve; Donahue, Megan; Carilli, Chris

    1995-01-01

    The Goddard High Resolution Spectrograph aboard the Hubble Space Telescope was used with the G160M grating to obtain high-resolution (6.2 A) spectra of three very bright active galactic nuclei located behind voids in the nearby distribution of bright galaxies (i.e., CfA and Arecibo redshift survey regions). A total of eight definite (greater than or equal to 4 sigma) Ly(alpha) absorption lines were discovered ranging in equivalent width from 26 to 240 mA at Galactocentric velocities 1740-7740 km/s. Of these eight systems, we locate seven in supercluster structures and one, in the sight line of Mrk 501 at 7740 km/s, in a void. In addition, one of two tentative (3-4 sigma) Ly(alpha) absorption lines are found in voids. Thus, the voids are not entirely devoid of matter, and not all Ly(alpha) clouds are associated with galaxies. Also, since the path lengths through voids and superclusters probed by our observations thus far are nearly equal, there is some statistical evidence that the Ly(alpha) clouds avoid the voids. The nearest galaxy neighbors to these absorbing clouds are 0.45-5.9 Mpc away, too far to be physically associated by most models. The lower equivalent width absorption lines (W(sub lambda) less than or equal to 100 mA) are consistent with random locations with respect to galaxies and may be truly intergalactic, similar to the bulk of the Ly(alpha) forest seen at high z. These results on local Ly(alpha) clouds are in full agreement with those found by Morris et al. (1993) for the 3C 273 sight line but are different from the results for higher equivalent width systems where closer cloud-galaxy associations were found by Lanzetta et al. (1994). Pencil-beam optical and 21 cm radio line observations of the area of sky surrounding Mrk 501 fail to find faint galaxies near the velocities of the Ly(alpha) clouds in that sight line. Specifically, for the 'void absorption' system at 7740 km/s, we find no galaxy at comparable redshift to the absorber within 100 h

  17. THE LINE POLARIZATION WITHIN A GIANT Ly{alpha} NEBULA

    SciTech Connect

    Prescott, Moire K. M.; Smith, Paul S.; Schmidt, Gary D.; Dey, Arjun

    2011-04-01

    Recent theoretical work has suggested that Ly{alpha} nebulae could be substantially polarized in the Ly{alpha} emission line, depending on the geometry, kinematics, and powering mechanism at work. Polarization observations can therefore provide a useful constraint on the source of ionization in these systems. In this Letter, we present the first Ly{alpha} polarization measurements for a giant Ly{alpha} nebula at z{approx} 2.656. We do not detect any significant linear polarization of the Ly{alpha} emission: P{sub Ly{alpha}} = 2.6% {+-} 2.8% (corrected for statistical bias) within a single large aperture. The current data also do not show evidence for the radial polarization gradient predicted by some theoretical models. These results rule out singly scattered Ly{alpha} (e.g., from the nearby active galactic nucleus, AGN) and may be inconsistent with some models of backscattering in a spherical outflow. However, the effects of seeing, diminished signal-to-noise ratio, and angle averaging within radial bins make it difficult to put strong constraints on the radial polarization profile. The current constraints may be consistent with higher density outflow models, spherically symmetric infall models, photoionization by star formation within the nebula or the nearby AGN, resonant scattering, or non-spherically symmetric cold accretion (i.e., along filaments). Higher signal-to-noise ratio data probing to higher spatial resolution will allow us to harness the full diagnostic power of polarization observations in distinguishing between theoretical models of giant Ly{alpha} nebulae.

  18. DISCOVERY OF A GIANT Ly{alpha} EMITTER NEAR THE REIONIZATION EPOCH

    SciTech Connect

    Ouchi, Masami; McCarthy, Patrick J.; Momcheva, Ivelina; Dressler, Alan; Ono, Yoshiaki; Shimasaku, Kazuhiro; Okamura, Sadanori; Hayashi, Masao; Egami, Eiichi; Saito, Tomoki; Oguri, Masamune; Farrah, Duncan; Kashikawa, Nobunari; Iye, Masanori; Nakanishi, Kouichiro; Furusawa, Hisanori; Akiyama, Masayuki; Dunlop, James S.; Mortier, Angela M. J.; Cirasuolo, Michele

    2009-05-10

    We report the discovery of a giant Ly{alpha} emitter (LAE) with a Spitzer/Infrared Array Camera (IRAC) counterpart near the reionization epoch at z = 6.595. The giant LAE is found from the extensive 1 deg{sup 2} Subaru narrowband survey for z = 6.6 LAEs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and subsequently identified by deep spectroscopy of Keck/DEIMOS and Magellan/IMACS. Among our 207 LAE candidates, this LAE is not only the brightest narrowband object with L(Ly{alpha}) = 3.9 {+-} 0.2 x 10{sup 43} erg s{sup -1} in our survey volume of 10{sup 6} Mpc{sup 3}, but also a spatially extended Ly{alpha} nebula with the largest isophotal area whose major axis is at least {approx_equal}3''. This object is more likely to be a large Ly{alpha} nebula with a size of {approx}>17 kpc than to be a strongly lensed galaxy by a foreground object. Our Keck spectrum with medium-high spectral and spatial resolutions suggests that the velocity width is v {sub FWHM} = 251 {+-} 21 km s{sup -1}, and that the line-center velocity changes by {approx_equal}60 km s{sup -1} in a 10 kpc range. The stellar mass and star formation rate are estimated to be 0.9-5.0 x 10{sup 10} M {sub sun} and >34 M {sub sun} yr{sup -1}, respectively, from the combination of deep optical to infrared images of Subaru, UKIDSS-Ultra Deep Survey, and Spitzer/IRAC. Although the nature of this object is not yet clearly understood, this could be an important object for studying cooling clouds accreting onto a massive halo, or forming-massive galaxies with significant outflows contributing to cosmic reionization and metal enrichment of intergalactic medium.

  19. THE DISCOVERY OF A LARGE Ly{alpha}+He II NEBULA AT z {approx} 1.67: A CANDIDATE LOW METALLICITY REGION?

    SciTech Connect

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T. E-mail: dey@noao.edu

    2009-09-01

    We have discovered a {approx}45 kpc Ly{alpha} nebula (or Ly{alpha} 'blob') at z {approx} 1.67 which exhibits strong, spatially extended He II emission and very weak C IV and C III] emission. This is the first spatially extended Ly{alpha}+He II emitter observed and the lowest redshift Ly{alpha} blob yet found. Strong Ly{alpha} and He II{lambda}1640 emission in the absence of metal lines has been proposed as a unique observational signature of primordial galaxy formation (e.g., from gravitational cooling radiation or Population III star formation), but no convincing examples of spatially extended Ly{alpha}+He II emitters have surfaced either in Ly{alpha}-emitting galaxy surveys at high redshifts (z > 4) or in studies of Ly{alpha} nebulae at lower redshifts. From comparisons with photoionization models, we find that the observed line ratios in this nebula are consistent with low metallicity gas (Z {approx}< 10{sup -2}-10{sup -3} Z{sub sun}), but that this conclusion depends on the unknown ionization parameter of the system. The large He II equivalent width ({approx}37 {+-} 10 A) and the large He II/Ly{alpha} ratio (0.12 {+-} 0.04) suggest that the cloud is being illuminated by a hard ionizing continuum, either an active galactic nucleus (AGN) or very low metallicity stars, or perhaps powered by gravitational cooling radiation. Thus far there is no obvious sign of a powerful AGN in or near the system, so in order to power the nebula while remaining hidden from view even in the mid-infrared, the AGN would need to be heavily obscured. Despite the strong Ly{alpha}+He II emission, it is not yet clear what is the dominant power source for this nebula. The system therefore serves as an instructive example of how the complexities of true astrophysical sources will complicate matters when attempting to use a strong Ly{alpha}+He II signature as a unique tracer of primordial galaxy formation.

  20. SPECTROSCOPIC CONFIRMATION OF FAINT LYMAN BREAK GALAXIES NEAR REDSHIFT FIVE IN THE HUBBLE ULTRA DEEP FIELD

    SciTech Connect

    Rhoads, James E.; Malhotra, Sangeeta; Cohen, Seth; Grogin, Norman; Hathi, Nimish; Ryan, Russell; Straughn, Amber; Windhorst, Rogier A. Pirzkal, Norbert; Xu Chun; Koekemoer, Anton; Panagia, Nino; Dickinson, Mark; Ferreras, Ignacio; Gronwall, Caryl; Kuemmel, Martin; Walsh, Jeremy; Meurer, Gerhardt; Pasquali, Anna; Yan, H.-J.

    2009-05-20

    We present the faintest spectroscopically confirmed sample of z {approx} 5 Lyman break galaxies (LBGs) to date. The sample is based on slitless grism spectra of the Hubble Ultra Deep Field region from the Grism ACS Program for Extragalactic Science (GRAPES) and Probing Evolution and Reionization Spectroscopically (PEARS) projects, using the G800L grism on the Hubble Space Telescope Advanced Camera for Surveys. We report here confirmations of 39 galaxies, preselected as candidate LBGs using photometric selection criteria. We compare a 'traditional' V-dropout selection, based on the work of Giavalisco et al., to a more liberal one (with V - i > 0.9), and find that the traditional criteria are about 64% complete and 81% reliable. We also study the Ly{alpha} emission properties of our sample. We find that Ly{alpha} emission is detected in {approx}1/4 of the sample, and that the liberal V-dropout color selection includes {approx}55% of previously published line-selected Ly{alpha} sources. Finally, we examine our stacked two-dimensional spectra. We demonstrate that strong, spatially extended ({approx}1'') Ly{alpha} emission is not a generic property of these LBGs, but that a modest extension of the Ly{alpha} photosphere (compared to the starlight) may be present in those galaxies with prominent Ly{alpha} emission.

  1. RADIATIVE TRANSFER MODELING OF Ly{alpha} EMITTERS. I. STATISTICS OF SPECTRA AND LUMINOSITY

    SciTech Connect

    Zheng Zheng; Cen Renyue; Trac, Hy; Miralda-Escude, Jordi

    2010-06-10

    We combine a cosmological reionization simulation with box size of 100 h {sup -1} Mpc on a side and a Monte Carlo Ly{alpha} radiative transfer code to model Ly{alpha} Emitters (LAEs) at z {approx} 5.7. The model introduces Ly{alpha} radiative transfer as the single factor for transforming the intrinsic Ly{alpha} emission properties into the observed ones. Spatial diffusion of Ly{alpha} photons from radiative transfer results in extended Ly{alpha} emission and only the central part with high surface brightness can be observed. Because of radiative transfer, the appearance of LAEs depends on density and velocity structures in circumgalactic and intergalactic media as well as the viewing angle, which leads to a broad distribution of apparent (observed) Ly{alpha} luminosity for a given intrinsic Ly{alpha} luminosity. Radiative transfer also causes frequency diffusion of Ly{alpha} photons. The resultant Ly{alpha} line is asymmetric with a red tail. The peak of the Ly{alpha} line shifts toward longer wavelength and the shift is anti-correlated with the apparent-to-intrinsic Ly{alpha} luminosity ratio. The simple radiative transfer model provides a new framework for studying LAEs. It is able to explain an array of observed properties of z {approx} 5.7 LAEs in Ouchi et al., producing Ly{alpha} spectra, morphology, and apparent Ly{alpha} luminosity function (LF) similar to those seen in observation. The broad distribution of apparent Ly{alpha} luminosity at fixed UV luminosity provides a natural explanation for the observed UV LF, especially the turnover toward the low luminosity end. The model also reproduces the observed distribution of Ly{alpha} equivalent width (EW) and explains the deficit of UV bright, high EW sources. Because of the broad distribution of the apparent-to-intrinsic Ly{alpha} luminosity ratio, the model predicts effective duty cycles and Ly{alpha} escape fractions for LAEs.

  2. THE FUNDAMENTAL PLANE OF DAMPED Ly{alpha} SYSTEMS

    SciTech Connect

    Neeleman, Marcel; Wolfe, Arthur M.; Prochaska, J. Xavier

    2013-05-20

    Using a sample of 100 H I-selected damped Ly{alpha} (DLA) systems, observed with the High Resolution Echelle Spectrometer on the Keck I telescope, we present evidence that the scatter in the well-studied correlation between the redshift and metallicity of a DLA is largely due to the existence of a mass-metallicity relationship at each redshift. To describe the fundamental relations that exist between redshift, metallicity, and mass, we use a fundamental plane description, which is described by the following equation: [M/H] = (- 1.9 {+-} 0.5) + (0.74 {+-} 0.21) {center_dot} log {Delta}v{sub 90} - (0.32 {+-} 0.06) {center_dot} z. Here, we assert that the velocity width, {Delta}v{sub 90}, which is defined as the velocity interval containing 90% of the integrated optical depth, traces the mass of the underlying dark matter halo. This description provides two significant improvements over the individual descriptions of the mass-metallicity correlation and metallicity-redshift correlation. Firstly, the fundamental equation reduces the scatter around both relationships by about 20%, providing a more stringent constraint on numerical simulations modeling DLAs. Secondly, it confirms that the dark matter halos that host DLAs satisfy a mass-metallicity relationship at each redshift between redshifts 2 through 5.

  3. Ly{alpha} EMITTERS AT z = 7 IN THE SUBARU/XMM-NEWTON DEEP SURVEY FIELD: PHOTOMETRIC CANDIDATES AND LUMINOSITY FUNCTION

    SciTech Connect

    Ota, Kazuaki; Ouchi, Masami; Iye, Masanori; Kashikawa, Nobunari; Kobayashi, Masakazu A. R.; Morokuma, Tomoki; Furusawa, Hisanori; Shimasaku, Kazuhiro; Totani, Tomonori; Nagashima, Masahiro; Harayama, Atsushi; Kodaka, Natsuki; Tajitsu, Akito; Hattori, Takashi

    2010-10-10

    We conducted a deep narrowband NB973 (FWHM = 200 A centered at 9755 A) survey of z = 7 Ly{alpha} emitters (LAEs) in the Subaru/XMM-Newton Deep Survey Field, using the fully depleted CCDs newly installed on the Subaru Telescope Suprime-Cam, which is twice more sensitive to z = 7 Ly{alpha} at {approx}1 {mu}m than the previous CCDs. Reaching the depth 0.5 mag deeper than our previous survey in the Subaru Deep Field that led to the discovery of a z = 6.96 LAE, we detected three probable z = 7 LAE candidates. Even if all the candidates are real, the Ly{alpha} luminosity function (LF) at z = 7 shows a significant deficit from the LF at z = 5.7 determined by previous surveys. The LAE number and Ly{alpha} luminosity densities at z = 7 are {approx}7.7%-54% and {approx}5.5%-39%, respectively, of those at z = 5.7, to the Ly{alpha} line luminosity limit of L(Ly{alpha}) {approx}> 9.2 x 10{sup 42} erg s{sup -1}. This could be due to evolution of the LAE population at these epochs as a recent galaxy evolution model predicts that the LAE modestly evolves from z = 5.7 to 7. However, even after correcting for this effect of galaxy evolution on the decrease in LAE number density, the z = 7 Ly{alpha} LF still shows a deficit from z = 5.7 LF. This might reflect the attenuation of Ly{alpha} emission by neutral hydrogen remaining at the epoch of reionization and suggests that reionization of the universe might not be complete yet at z = 7. If we attribute the density deficit to reionization, the intergalactic medium transmission for Ly{alpha} photons at z = 7 would be 0.4 {<=} T {sup IGM}{sub Ly{alpha} {<=}} 1, supporting the possible higher neutral fraction at the earlier epochs at z > 6 suggested by the previous surveys of z = 5.7-7 LAEs, z {approx} 6 quasars, and z > 6 gamma-ray bursts.

  4. PROBING PRIMORDIAL MAGNETIC FIELDS USING Ly{alpha} CLOUDS

    SciTech Connect

    Pandey, Kanhaiya L.; Sethi, Shiv K.

    2013-01-01

    From previous studies of the effect of primordial magnetic fields on early structure formation, we know that the presence of primordial magnetic fields during early structure formation could induce more perturbations at small scales (at present 1-10 h {sup -1} Mpc) as compared to the usual {Lambda}CDM theory. Matter power spectra over these scales are effectively probed by cosmological observables such as shear correlation and Ly{alpha} clouds. In this paper we discuss the implications of primordial magnetic fields on the distribution of Ly{alpha} clouds. We simulate the line-of-sight density fluctuation including the contribution coming from the primordial magnetic fields. We compute the evolution of Ly{alpha} opacity for this case and compare our theoretical estimates of Ly{alpha} opacity with the existing data to constrain the parameters of the primordial magnetic fields. We also discuss the case when the two density fields are correlated. Our analysis yields an upper bound of roughly 0.3-0.6 nG on the magnetic field strength for a range of nearly scale-invariant models, corresponding to a magnetic field power spectrum index n {approx_equal} -3.

  5. THE LYMAN ALPHA MORPHOLOGY OF LOCAL STARBURST GALAXIES: RELEASE OF CALIBRATED IMAGES

    SciTech Connect

    Oestlin, Goeran; Hayes, Matthew; Kunth, Daniel; Atek, Hakim; Mas-Hesse, J. Miguel; Leitherer, Claus; Petrosian, Artashes E-mail: matthew.hayes@unige.ch

    2009-09-15

    We present reduced and calibrated high resolution Lyman-alpha (Ly{alpha}) images for a sample of six local star-forming galaxies. Targets were selected to represent a range in luminosity and metallicity and to include both known Ly{alpha} emitters and nonemitters. Far ultraviolet imaging was carried out with the Solar Blind Channel of the Advanced Camera for Surveys on the Hubble Space Telescope (HST) in the F122M (Ly{alpha} online) and F140LP (continuum) filters. The resulting Ly{alpha} images are the product of careful modeling of both the stellar and nebular continua, facilitated by supporting HST imaging at {lambda} {approx} 2200, 3300, 4400, 5500, H{alpha}, and 8000 A, combined with Starburst 99 evolutionary synthesis models, and prescriptions for dust extinction on the continuum. In all, the resulting morphologies in Ly{alpha}, H{alpha}, and UV continuum are qualitatively very different and we show that the bulk of Ly{alpha} emerges in a diffuse component resulting from resonant scattering events. Ly{alpha} escape fractions, computed from integrated H{alpha} luminosities and recombination theory, are found never to exceed 14%. Internal dust extinction is estimated in each pixel and used to correct Ly{alpha} fluxes. However, the extinction corrections are far too small (by factors from 2.6 to infinity) to reconcile the emerging global Ly{alpha} luminosities with standard recombination predictions. Surprisingly, when comparing the global equivalent widths of Ly{alpha} and H{alpha}, the two quantities appear to be anticorrelated, which may be due to the evolution of mechanical feedback from the starburst. This calls for caution in the interpretation of Ly{alpha} observations in terms of star formation rates. The images presented have a physical resolution 3 orders of magnitude better than attainable at high redshifts from the ground with current instrumentation and our images may therefore serve as useful templates for comparing with observations and modeling of

  6. HUBBLE/COS OBSERVATIONS OF THE Ly{alpha} FOREST TOWARD THE BL Lac OBJECT 1ES 1553+113

    SciTech Connect

    Danforth, Charles W.; Keeney, Brian A.; Stocke, John T.; Shull, J. Michael; Yao Yangsen

    2010-09-01

    We present new moderate-resolution, far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 1ES 1553+113 covering the wavelength range 1135 A < {lambda} < 1795 A. The data show a smooth continuum with a wealth of narrow (b < 100 km s{sup -1}) absorption features arising in the interstellar medium and intergalactic medium. These features include 41 Ly{alpha} absorbers at 0 < z{sub abs} < 0.43, 14 of which are detected in multiple Lyman lines and 6 of which show absorption in one or more metal lines. We analyze a metal-rich triplet ({Delta}cz {approx} 1000 km s{sup -1}) of Ly{alpha} absorbers at z{sub abs} {approx} 0.188 in which O VI, N V, and C III absorption is detected. Silicon ions (Si III, Si IV) are not detected to fairly strong upper limits and we use the measured Si III/C III upper limit to derive an abundance limit (C/Si) {>=} 4(C/Si){sub sun} for the strongest component of the absorber complex. Galaxy redshift surveys show a number of massive galaxies at approximately the same redshift as this absorption complex, suggesting that it arises in a large-scale galaxy filament. As one of the brightest extragalactic X-ray and {gamma}-ray sources, 1ES 1553+113 is of great interest to the high-energy astrophysics community. With no intrinsic emission or absorption features, 1ES 1553+113 has no direct redshift determination. We use intervening Ly{alpha} absorbers to place a direct limit on the redshift: z{sub em}>0.395 based on a confirmed Ly{alpha}+O VI absorber and z{sub em}>0.433 based on a single-line detection of Ly{alpha}. The current COS data are only sensitive to Ly{alpha} absorbers at z < 0.47, but we present statistical arguments that z{sub em} {approx}< 0.58 (at a 1{sigma} confidence limit) based on the non-detection of any Ly{beta} absorbers at z>0.4.

  7. PHYSICAL PROPERTIES OF Ly{alpha} EMITTERS AT z {approx} 0.3 FROM UV-TO-FIR MEASUREMENTS

    SciTech Connect

    Oteo, I.; Bongiovanni, A.; Perez Garcia, A. M.; Cepa, J.; Pintos-Castro, I.; Ederoclite, A.; Sanchez-Portal, M.; Altieri, B.; Perez-Martinez, R.; Andreani, P.; Aussel, H.; Daddi, E.; Elbaz, D.; Le Floc'h, E.; Cimatti, A.; and others

    2012-06-01

    The analysis of the physical properties of low-redshift Ly{alpha} emitters (LAEs) can provide clues in the study of their high-redshift analogs. At z {approx} 0.3, LAEs are bright enough to be detected over almost the entire electromagnetic spectrum and it is possible to carry out a more precise and complete study than at higher redshifts. In this work, we examine the UV and IR emission, dust attenuation, star formation rate (SFR), and morphology of a sample of 23 GALEX-discovered star-forming LAEs at z {approx} 0.3 with direct UV (GALEX), optical (ACS), and FIR (PACS and MIPS) data. Using the same UV and IR limiting luminosities, we find that LAEs at z {approx} 0.3 tend to be less dusty, have slightly higher total SFRs, have bluer UV continuum slopes, and are much smaller than other galaxies that do not exhibit Ly{alpha} emission in their spectrum (non-LAEs). These results suggest that at z {approx} 0.3, Ly{alpha} photons tend to escape from small galaxies with low dust attenuation. Regarding their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and morphology represent the most noticeable difference between LAEs and non-LAEs at z {approx} 0.3. Furthermore, the comparison of our results with those obtained at higher redshifts indicates either that the Ly{alpha} technique picks up different kind of galaxies at different redshifts or that the physical properties of LAEs are evolving with redshift.

  8. CHEMICAL ENRICHMENT IN THE CARBON-ENHANCED DAMPED Ly{alpha} SYSTEM BY POPULATION III SUPERNOVAE

    SciTech Connect

    Kobayashi, Chiaki; Tominaga, Nozomu; Nomoto, Ken'ichi

    2011-04-01

    We show that the recently observed elemental abundance pattern of the carbon-rich metal-poor damped Ly{alpha} (DLA) system is in excellent agreement with the nucleosynthesis yields of faint core-collapse supernovae of primordial stars. The observed abundance pattern is not consistent with the nucleosynthesis yields of pair-instability supernovae. The DLA abundance pattern is very similar to that of carbon-rich extremely metal-poor (EMP) stars, and the contributions from low-mass stars and/or binary effects should be very small in DLAs. This suggests that chemical enrichment by the first stars in the first galaxies is driven by core-collapse supernovae from {approx}20 to 50 M{sub sun} stars and also supports the supernova scenario as the enrichment source of EMP stars in the Milky Way Galaxy.

  9. STRONG FIELD-TO-FIELD VARIATION OF Ly{alpha} NEBULAE POPULATIONS AT z {approx_equal} 2.3

    SciTech Connect

    Yang Yujin; Zabludoff, Ann; Eisenstein, Daniel; Dave, Romeel E-mail: azabludoff@as.arizona.ed E-mail: rad@as.arizona.ed

    2010-08-20

    Understanding the nature of distant Ly{alpha} nebulae, aka 'blobs', and connecting them to their present-day descendants requires constraining their number density, clustering, and large-scale environment. To measure these basic quantities, we conduct a deep narrowband imaging survey in four different fields, Chandra Deep Field South (CDFS), Chandra Deep Field North (CDFN), and two COSMOS subfields, for a total survey area of 1.2 deg{sup 2}. We discover 25 blobs at z = 2.3 with Ly{alpha} luminosities of L{sub Ly{alpha}=} (0.7-8) x 10{sup 43} erg s{sup -1} and isophotal areas of A{sub iso} = 10-60 {open_square}arcsec. The transition from compact Ly{alpha} emitters (LAEs; A{sub iso} {approx} a few {open_square}arcsec ) to extended Ly{alpha} blobs (A {sub iso} > 10 {open_square}arcsec) is continuous, suggesting a single family perhaps governed by similar emission mechanisms. Surprisingly, most blobs (16/25) are in one survey field, the CDFS. The six brightest, largest blobs with L {sub Ly{alpha} {approx}}> 1.5x10{sup 43} erg s{sup -1} and A{sub iso} > 16 {open_square}arcsec lie only in the CDFS. These large, bright blobs have a field-to-field variance of {sigma} {sub v} {approx}> 1.5 (150%) about their number density n {approx}1.0{sup +1.8}{sub -0.6}x 10{sup -5} Mpc{sup -3}. This variance is large, significantly higher than that of unresolved LAEs ({sigma} {sub v} {approx} 0.3 or 30%), and can adversely affect comparisons of blob number densities and luminosity functions (LFs) among different surveys. Our deep, blind survey allows us to construct a reliable blob LF. We compare the statistics of our blobs with dark matter halos in a 1 h {sup -1} Gpc cosmological N-body simulation. At z = 2.3, n implies that each bright, large blob could occupy a halo of M{sub halo} {approx}>10{sup 13} M{sub sun} if most halos have detectable blobs. The predicted variance in n is consistent with that observed and corresponds to a bias of {approx}7. Blob halos lie at the high end of the

  10. ASYMMETRIC ABSORPTION PROFILES OF Ly{alpha} AND Ly{beta} IN DAMPED Ly{alpha} SYSTEMS

    SciTech Connect

    Lee, Hee-Won

    2013-08-01

    Damped Ly{alpha} systems observed in the quasar spectra are characterized by a high neutral hydrogen column density, N{sub HI} > 2 x 10{sup 20} cm{sup -2}. The absorption wing profiles are often fitted using the Voigt function due to the fact that the scattering cross section near the resonant line center is approximately described by the Lorentzian function. Since a hydrogen atom has infinitely many p states that participate in the electric dipole interaction, the cross section starts to deviate from the Lorentzian in an asymmetric way in the line wing regions. We investigate this asymmetry in the absorption line profiles around Ly{alpha} and Ly{beta} as a function of the neutral hydrogen column density N{sub HI}. In terms of {Delta}{lambda} {identical_to} {lambda} - {lambda}{sub {alpha}}, we expand the Kramers-Heisenberg formula around Ly{alpha} to find {sigma}({lambda}) {approx_equal} (0.5f{sub 12}){sup 2}{sigma}{sub T}({Delta}{lambda}/{lambda}{sub {alpha}}){sup -2}[1 + 3.792({Delta}{lambda}/{lambda}{sub {alpha}})], where f{sub 12} and {sigma}{sub T} are the oscillator strength of Ly{alpha} and the Thomson scattering cross section, respectively. In terms of {Delta}{lambda}{sub 2} {identical_to} {lambda} - {lambda}{sub {beta}} in the vicinity of Ly{beta}, the total scattering cross section, given as the sum of cross sections for Rayleigh and Raman scattering, is shown to be {sigma}({lambda}) {approx_equal} {sigma}{sub T}(0.5f{sub 13}){sup 2}(1 + R{sub 0})({Delta}{lambda}{sub 2}/{lambda}{sub {beta}}){sup -2}[1 - 24.68({Delta}{lambda}{sub 2}/{lambda}{sub {beta}})] with f{sub 13} and the factor R{sub 0} = 0.1342 being the oscillator strength for Ly{beta} and the ratio of the Raman cross section to Rayleigh cross section, respectively. A redward asymmetry develops around Ly{alpha}, whereas a blue asymmetry is obtained for Ly{beta}. The absorption center shifts are found to be almost proportional to the neutral hydrogen column density.

  11. KECK SPECTROSCOPY OF FAINT 3>z>7 LYMAN BREAK GALAXIES: A HIGH FRACTION OF LINE EMITTERS AT REDSHIFT SIX

    SciTech Connect

    Stark, Daniel P.; Ellis, Richard S.; Ouchi, Masami

    2011-02-10

    As Ly{alpha} photons are scattered by neutral hydrogen, a change with redshift in the Ly{alpha} equivalent width (EW) distribution of distant galaxies offers a promising probe of the degree of ionization in the intergalactic medium and hence when cosmic reionization ended. This simple test is complicated by the fact that Ly{alpha} emission can also be affected by variations in the kinematics and dust content of the host galaxies. In the first paper in this series, we demonstrated both a luminosity- and redshift-dependent trend in the fraction of Ly{alpha} emitters seen within color-selected 'Lyman break' galaxies (LBGs) over the range 3 < z < 6; lower luminosity galaxies and those at higher redshift show an increased likelihood of strong emission. Here, we present the results from 12.5 hr exposures with the Keck DEIMOS spectrograph focused primarily on LBGs at z {approx_equal} 6 which enable us to confirm the redshift dependence of line emission more robustly and to higher redshift than was hitherto possible. We find that 54% {+-} 11% of faint z {approx_equal} 6 LBGs show strong (W{sub Ly{alpha},0}>25 A) emission, an increase of 55% from a sample of similarly luminous z {approx_equal} 4 galaxies. With a total sample of 74 z {approx_equal} 6 LBGs, we determine the luminosity-dependent Ly{alpha} EW distribution. Assuming continuity in these trends to the new population of z {approx_equal} 7 sources located with the Hubble WFC3/IR camera, we predict that unless the neutral fraction rises in the intervening 200 Myr, the success rate for spectroscopic confirmation using Ly{alpha} emission should be high.

  12. PANORAMIC SURVEY OF Ly{alpha} EMITTERS AT z = 3.1

    SciTech Connect

    Yamada, T.; Nakamura, Y.; Morimoto, N.; Matsuda, Y.; Hayashino, T.; Yamauchi, R.; Kousai, K.; Umemura, M.

    2012-04-15

    We present the results of the extensive narrowband survey of Ly{alpha} emission-line objects at z = 3.1 in the 1.38 deg{sup 2} area surrounding the high-density region of star-forming galaxies at z = 3.09 in the SSA22 field, as well as in the 1.04 deg{sup 2} area of the three separated general blank fields. In total, of 2161 Ly{alpha} emitters, there are 1394 in the SSA22 fields and 767 in the general fields detected at the narrowband AB magnitude limit of 25.73, which corresponds to the line flux of Almost-Equal-To 1.8 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} or the luminosity of Almost-Equal-To 1.5 Multiplication-Sign 10{sup 42} erg s{sup -1} at z = 3.1, above the observed equivalent-width threshold, Almost-Equal-To 190 A. The average surface number density of the emitters at z = 3.1 in the general fields above the thresholds is 0.20 {+-} 0.01 arcmin{sup -2}. The SSA22 high-density region at z = 3.09, whose peak local density is six times that of the average, is found to be the most prominent outstanding structure in the whole surveyed area and is firmly identified as a robust 'protocluster'. We also compared the overdensity of the 100 arcmin{sup 2} and 700 arcmin{sup 2} areas which contain the protocluster with the expected fluctuation of the dark matter as well as those of the model galaxies in cosmological simulations. We found that the peak height values of the overdensity are 8-10 and 3-4 times the expected standard deviations for the counts of Ly{alpha} emitters at z = 3.1 in the corresponding volume, respectively. We conclude that the structure at z = 3.09 in the SSA22 field is a very significant and rare density peak up to the scale of Almost-Equal-To 60 Mpc.

  13. A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. II. SPECTROSCOPIC CONFIRMATION

    SciTech Connect

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T.

    2013-01-01

    Using a systematic broadband search technique, we have carried out a survey for large Ly{alpha} nebulae (or Ly{alpha} {sup b}lobs{sup )} at 2 {approx}< z {approx}< 3 within 8.5 deg{sup 2} of the NOAO Deep Wide-Field Survey Booetes field, corresponding to a total survey comoving volume of Almost-Equal-To 10{sup 8} h {sup -3} {sub 70} Mpc{sup 3}. Here, we present our spectroscopic observations of candidate giant Ly{alpha} nebulae. Of 26 candidates targeted, 5 were confirmed to have Ly{alpha} emission at 1.7 {approx}< z {approx}< 2.7, 4 of which were new discoveries. The confirmed Ly{alpha} nebulae span a range of Ly{alpha} equivalent widths, colors, sizes, and line ratios, and most show spatially extended continuum emission. The remaining candidates did not reveal any strong emission lines, but instead exhibit featureless, diffuse, blue continuum spectra. Their nature remains mysterious, but we speculate that some of these might be Ly{alpha} nebulae lying within the redshift desert (i.e., 1.2 {approx}< z {approx}< 1.6). Our spectroscopic follow-up confirms the power of using deep broadband imaging to search for the bright end of the Ly{alpha} nebula population across enormous comoving volumes.

  14. Ly(alpha) Photolysis in the Primitive Solar Nebula

    NASA Astrophysics Data System (ADS)

    Gladstone, G. Randall

    1998-01-01

    This is the final report for the third year of work on this project. Our proposal was to quantitatively investigate the importance of photochemistry in the solar nebula. In the generally accepted theory for the chemical evolution of the primitive solar nebula, Prinn and Fegley argued that photochemistry is unimportant, and that thermochemistry controls the relative abundances of molecular species throughout the planet-forming region. They provided useful estimates of the chemical energy available to the solar nebula from a variety of sources, and established that even the small photolysis rate due to starlight is more important than the photolysis rate from direct sunlight (although small, the UV flux from starlight could have processed a non-negligible fraction of the solar nebula. The reason for this is that the opacity of the disk was so large that direct sunlight could only penetrate to 0.1 AU or so, despite the expectation that the protosun, if comparable to a T-Tauri star, would be emitting up to 104 more H I Ly(alpha) photons than the current sun. We developed a Monte Carlo resonance fine radiative transfer code, capable of accurately calculating the radiation field of H I Ly(alpha), He I 584 A, and He II 304 A emissions throughout the nebula and the nearby interstellar medium in which it is embedded. We applied the code to two appropriate models of the primitive solar nebula. Our model provided the photolysis rates of various species over the entire surface layer of the nebula, and from this we evaluated the importance of UV photochemistry due to backscattered solar UV resonance line emissions on different parts of the nebula. The results discussed below were presented.

  15. Ly(alpha) Photolysis in the Primitive Solar Nebula

    NASA Technical Reports Server (NTRS)

    Gladstone, G. Randall

    1998-01-01

    This is the final report for the third year of work on this project. Our proposal was to quantitatively investigate the importance of photochemistry in the solar nebula. In the generally accepted theory for the chemical evolution of the primitive solar nebula, Prinn and Fegley argued that photochemistry is unimportant, and that thermochemistry controls the relative abundances of molecular species throughout the planet-forming region. They provided useful estimates of the chemical energy available to the solar nebula from a variety of sources, and established that even the small photolysis rate due to starlight is more important than the photolysis rate from direct sunlight (although small, the UV flux from starlight could have processed a non-negligible fraction of the solar nebula. The reason for this is that the opacity of the disk was so large that direct sunlight could only penetrate to 0.1 AU or so, despite the expectation that the protosun, if comparable to a T-Tauri star, would be emitting up to 10(exp 4) more H I Ly(alpha) photons than the current sun. We developed a Monte Carlo resonance fine radiative transfer code, capable of accurately calculating the radiation field of H I Ly(alpha), He I 584 A, and He II 304 A emissions throughout the nebula and the nearby interstellar medium in which it is embedded. We applied the code to two appropriate models of the primitive solar nebula. Our model provided the photolysis rates of various species over the entire surface layer of the nebula, and from this we evaluated the importance of UV photochemistry due to backscattered solar UV resonance line emissions on different parts of the nebula. The results discussed below were presented.

  16. Ly{alpha} DOMINANCE OF THE CLASSICAL T TAURI FAR-ULTRAVIOLET RADIATION FIELD

    SciTech Connect

    Schindhelm, Eric; France, Kevin; Brown, Alexander; Herczeg, Gregory J.; Bergin, Edwin; Yang Hao; Brown, Joanna M.; Linsky, Jeffrey L.; Valenti, Jeff

    2012-09-01

    Far-ultraviolet (FUV) radiation plays an important role in determining chemical abundances in protoplanetary disks. H I Lyman {alpha} (Ly{alpha}) is suspected to be the dominant component of the FUV emission from Classical T Tauri Stars (CTTSs), but is difficult to measure directly due to circumstellar and interstellar H I absorption. To better characterize the intrinsic Ly{alpha} radiation, we present FUV spectra of 14 CTTSs taken with the Hubble Space Telescope Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph instruments. H{sub 2} fluorescence, commonly seen in the spectra of CTTSs, is excited by Ly{alpha} photons, providing an indirect measure of the Ly{alpha} flux incident upon the warm disk surface. We use observed H{sub 2} progression fluxes to reconstruct the CTTS Ly{alpha} profiles. The Ly{alpha} flux correlates with total measured FUV flux, in agreement with an accretion-related source of FUV emission. With a geometry-independent analysis, we confirm that in accreting T Tauri systems Ly{alpha} radiation dominates the FUV flux ({approx}1150 A -1700 A). In the systems surveyed this one line comprises 70%-90% of the total FUV flux.

  17. COMPUTING INTRINSIC LY{alpha} FLUXES OF F5 V TO M5 V STARS

    SciTech Connect

    Linsky, Jeffrey L.; France, Kevin; Ayres, Tom

    2013-04-01

    The Ly{alpha} emission line dominates the far-ultraviolet spectra of late-type stars and is a major source for photodissociation of important molecules including H{sub 2}O, CH{sub 4}, and CO{sub 2} in exoplanet atmospheres. The incident flux in this line illuminating an exoplanet's atmosphere cannot be measured directly as neutral hydrogen in the interstellar medium (ISM) attenuates most of the flux reaching the Earth. Reconstruction of the intrinsic Ly{alpha} line has been accomplished for a limited number of nearby stars, but is not feasible for distant or faint host stars. We identify correlations connecting the intrinsic Ly{alpha} flux with the flux in other emission lines formed in the stellar chromosphere, and find that these correlations depend only gradually on the flux in the other lines. These correlations, which are based on Hubble Space Telescope spectra, reconstructed Ly{alpha} line fluxes, and irradiance spectra of the quiet and active Sun, are required for photochemical models of exoplanet atmospheres when intrinsic Ly{alpha} fluxes are not available. We find a tight correlation of the intrinsic Ly{alpha} flux with stellar X-ray flux for F5 V to K5 V stars, but much larger dispersion for M stars. We also show that knowledge of the stellar effective temperature and rotation rate can provide reasonably accurate estimates of the Ly{alpha} flux for G and K stars, and less accurate estimates for cooler stars.

  18. CHARACTERIZATION OF THE DISTRIBUTION OF THE Ly{alpha} EMITTERS IN THE 53W002 FIELD AT z = 2.4

    SciTech Connect

    Mawatari, K.; Yamada, T.; Nakamura, Y.; Hayashino, T.; Matsuda, Y.

    2012-11-10

    We present the results of our wide-field narrowband imaging of the field around the radio galaxy 53W002 at z = 2.390 with Subaru/Suprime-Cam. A custom-made filter, NB413, centered at 4140 A with a width of 83 A is used to observe the 31' Multiplication-Sign 24' area around the radio galaxy. We detected 204 Ly{alpha} emitters (LAEs) at z = 2.4 with a rest-frame equivalent width larger than 25 A to the depth of 26 AB mag (in NB413). The entire LAE population in the 53W002 field has an average number density and distributions of equivalent width and size that are similar to those of other fields at z {approx} 2. We identify a significant high-density region (53W002F-HDR) that spreads over Almost-Equal-To 5' Multiplication-Sign 4' near 53W002, where the LAE number density is nearly four times as large as the average of the entire field. Using the probability distribution function of density fluctuation, we evaluate the rareness probability of 53W002F-HDR to be 0.9{sup +2.4} {sub -0.62}%, which corresponds to a moderately rich structure. No notable environmental dependency at the comoving scale of 10 Mpc is found for the distributions of the Ly{alpha} equivalent width and luminosity in the field. We also detected four Ly{alpha} blobs, one of which is newly discovered. They are all located in the rims of high-density regions. The biased location and unique morphologies in Ly{alpha} suggest that galaxy interaction plays a key role in their formation.

  19. RESOLVING THE OPTICAL EMISSION LINES OF Ly{alpha} BLOB ''B1'' AT z = 2.38: ANOTHER HIDDEN QUASAR

    SciTech Connect

    Overzier, R. A.; Nesvadba, N. P. H.; Dijkstra, M.; Hatch, N. A.; Lehnert, M. D.; Villar-Martin, M.; Wilman, R. J.; Zirm, A. W.

    2013-07-10

    We have used the SINFONI near-infrared integral field unit on the Very Large Telescope to resolve the optical emission line structure of one of the brightest (L{sub Ly{alpha}} Almost-Equal-To 10{sup 44} erg s{sup -1}) and nearest (z Almost-Equal-To 2.38) of all Ly{alpha} blobs (LABs). The target, known in the literature as object {sup B}1{sup ,} lies at a redshift where the main optical emission lines are accessible in the observed near-infrared. We detect luminous [O III] {lambda}{lambda}4959, 5007 and H{alpha} emission with a spatial extent of at least 32 Multiplication-Sign 40 kpc (4'' Multiplication-Sign 5''). The dominant optical emission line component shows relatively broad lines (600-800 km s{sup -1}, FWHM) and line ratios consistent with active galactic nucleus (AGN) photoionization. The new evidence for AGN photoionization, combined with previously detected C IV and luminous, warm infrared emission, suggest that B1 is the site of a hidden quasar. This is confirmed by the fact that [O II] is relatively weak compared with [O III] (extinction-corrected [O III]/[O II] of about 3.8), which is indicative of a high, Seyfert-like ionization parameter. From the extinction-corrected [O III] luminosity we infer a bolometric AGN luminosity of {approx}3 Multiplication-Sign 10{sup 46} erg s{sup -1}, and further conclude that the obscured AGN may be Compton-thick given existing X-ray limits. The large line widths observed are consistent with clouds moving within the narrow-line region of a luminous QSO. The AGN scenario is capable of producing sufficient ionizing photons to power the Ly{alpha}, even in the presence of dust. By performing a census of similar objects in the literature, we find that virtually all luminous LABs harbor obscured quasars. Based on simple duty-cycle arguments, we conclude that AGNs are the main drivers of the Ly{alpha} in LABs rather than the gravitational heating and subsequent cooling suggested by cold stream models. We also conclude that the

  20. A SEARCH FOR OXYGEN IN THE LOW-DENSITY Ly{alpha} FOREST USING THE SLOAN DIGITAL SKY SURVEY

    SciTech Connect

    Pieri, Matthew M.; Frank, Stephan; Mathur, Smita; Weinberg, David H.; York, Donald G.; Oppenheimer, Benjamin D.

    2010-06-20

    We use 2167 Sloan Digital Sky Survey quasar spectra to search for low-density oxygen in the intergalactic medium (IGM). Oxygen absorption is detected on a pixel-by-pixel basis by its correlation with Ly{alpha} forest absorption. We have developed a novel locally calibrated pixel (LCP) search method that uses adjacent regions of the spectrum to calibrate interlopers and spectral artifacts, which would otherwise limit the measurement of O VI absorption. Despite the challenges presented by searching for weak O VI within the Ly{alpha} forest in spectra of moderate resolution and signal-to-noise, we find a highly significant detection of absorption by oxygen at 2.7 < z < 3.2 (the null hypothesis has a {chi}{sup 2} = 80 for nine data points). We interpret our results using synthetic spectra generated from a log-normal density field assuming a mixed quasar-galaxy photoionizing background and that it dominates the ionization fraction of detected O VI. The LCP search data can be fit by a constant metallicity model with [O/H] = -2.15{sup +0.07}{sub -0.09} but also by models in which low-density regions are unenriched and higher density regions have a higher metallicity. The density-dependent enrichment model by Aguirre et al. is also an acceptable fit. All our successful models have similar mass-weighted oxygen abundance, corresponding to [(O/H){sub MW}] = -2.45 {+-} 0.06. This result can be used to find the cosmic oxygen density in the Ly{alpha} forest, {Omega}{sub Oxy,IGM} = 1.4({+-}0.2) x 10{sup -6} {approx} 3 x 10{sup -4{Omega}}{sub b}. This is the tightest constraint on the mass-weighted mean oxygen abundance and the cosmic oxygen density in the Ly{alpha} forest to date and indicates that it contains {approx}16% of the total expected metal production by star formation up to z = 3.

  1. THE BOSS Ly{alpha} FOREST SAMPLE FROM SDSS DATA RELEASE 9

    SciTech Connect

    Lee, Khee-Gan; Bailey, Stephen; Carithers, William; Schlegel, David J.; Bartsch, Leslie E.; Dawson, Kyle S.; Bolton, Adam S.; Kirkby, David; Margala, Daniel; Blomqvist, Michael; Lundgren, Britt; Palanque-Delabrouille, Nathalie; Yeche, Christophe; Borde, Arnaud; Weinberg, David H.; Aubourg, Eric; Bautista, Julian; and others

    2013-03-15

    We present the BOSS Lyman-{alpha} (Ly{alpha}) Forest Sample from SDSS Data Release 9, comprising 54,468 quasar spectra with z{sub qso} > 2.15 suitable for Ly{alpha} forest analysis. This data set probes the intergalactic medium with absorption redshifts 2.0 < z{sub {alpha}} < 5.7 over an area of 3275 deg{sup 2}, and encompasses an approximate comoving volume of 20 h {sup -3} Gpc{sup 3}. With each spectrum, we have included several products designed to aid in Ly{alpha} forest analysis: improved sky masks that flag pixels where data may be unreliable, corrections for known biases in the pipeline estimated noise, masks for the cores of damped Ly{alpha} systems and corrections for their wings, and estimates of the unabsorbed continua so that the observed flux can be converted to a fractional transmission. The continua are derived using a principal component fit to the quasar spectrum redward of rest-frame Ly{alpha} ({lambda} > 1216 A), extrapolated into the forest region and normalized by a linear function to fit the expected evolution of the Ly{alpha} forest mean flux. The estimated continuum errors are {approx}< 5% rms. We also discuss possible systematics arising from uncertain spectrophotometry and artifacts in the flux calibration; global corrections for the latter are provided. Our sample provides a convenient starting point for users to analyze clustering in BOSS Ly{alpha} forest data, and it provides a fiducial data set that can be used to compare results from different analyses of baryon acoustic oscillations in the Ly{alpha} forest. The full data set is available from the SDSS-III DR9 Web site.

  2. An IUE survey of interstellar H I Ly alpha absorption. 1: Column densities

    NASA Technical Reports Server (NTRS)

    Diplas, Athanassios; Savage, Blair D.

    1994-01-01

    We measure Galactic interstellar neutral hydrogen column densities by analyzing archival interstellar Ly alpha absorption line data toward 554 B2 and hotter stars observed at high resolution with the IUE satellite. This study more than doubles the number of lines of sight with measures of N(H I) based on Ly alpha. We have included the scattered light background correction algorithm of Bianchi and Bohlin in our data reduction. We use the correlation between the Balmer discontinuity (c sub 1) index and the stellar Ly alpha absorption in order to assess the effects of stellar Ly alpha contamination. Approximately 40% of the B stars with measured (c sub 1) index, exhibit serious stellar Ly alpha contamination. One table contains the derived values of the interstellar N(H I) for 393 stars with at most small amounts of stellar contamination. Another lists the observed values of total N(H I) for 161 stars with suspected stellar Ly alpha contamination and/or uncertain stellar parameters.

  3. THE FIRST SYSTEMATIC SURVEY FOR Ly{alpha} EMITTERS AT z = 7.3 WITH RED-SENSITIVE SUBARU/SUPRIME-CAM

    SciTech Connect

    Shibuya, Takatoshi; Kashikawa, Nobunari; Iye, Masanori; Ota, Kazuaki; Ouchi, Masami; Furusawa, Hisanori; Shimasaku, Kazuhiro; Hattori, Takashi

    2012-06-20

    We have performed deep imaging surveys for Ly{alpha} emitters (LAEs) at redshift {approx}7.3 in two blank fields, the Subaru Deep Field (SDF) and the Subaru/XMM-Newton Deep survey Field (SXDF), using the Subaru/Suprime-Cam equipped with new red-sensitive CCDs and a new narrowband filter, NB1006 ({lambda}{sub c} = 10052 Angstrom-Sign , FWHM {Delta}{lambda} = 214 A). We identified four objects as LAE candidates that exhibit luminosity excess in NB1006. By carrying out deep follow-up spectroscopy for three of them using Subaru/FOCAS and Keck/DEIMOS, a definitively asymmetric emission line is detected for one of them, SXDF-NB1006-2. Assuming this line is Ly{alpha}, this object is an LAE at z = 7.215 which has a luminosity of 1.2{sup +1.5}{sub -0.6} Multiplication-Sign 10{sup 43} erg s{sup -1} and a weighted skewness S{sub {omega}} = 4.90 {+-} 0.86. Another object, SDF-NB1006-2, shows variable photometry and is thus probably a quasar (QSO) or an active galactic nucleus. It shows an asymmetric emission line at 10076 A which may be due to either Ly{alpha} at z = 7.288 or [O II] at z = 1.703. The third object, SDF-NB1006-1, is likely a galaxy with temporal luminosity enhancement associated with a supernova explosion, as the brightness of this object varies between the observed epochs. Its spectrum does not show any emission lines. The inferred decrease in the number density of LAEs toward higher redshift is n{sup z={sup {sup 7.3}{sub Ly{alpha}}}}/n{sub Ly{alpha}}{sup z={sup {sup 5.7}}} = 0.05{sup +0.11}{sub -0.05} from z = 5.7 to 7.3 down to L{sup Ly{alpha}} = 1.0 Multiplication-Sign 10{sup 43} erg s{sup -1}. The present result is consistent with the interpretation in previous studies that the neutral hydrogen fraction is rapidly increasing from z = 5.7 to 7.3.

  4. FIRST SPECTROSCOPIC EVIDENCE FOR HIGH IONIZATION STATE AND LOW OXYGEN ABUNDANCE IN Ly{alpha} EMITTERS ,

    SciTech Connect

    Nakajima, Kimihiko; Shimasaku, Kazuhiro; Hashimoto, Takuya; Ono, Yoshiaki; Ouchi, Masami; Lee, Janice C.

    2013-05-20

    We present results from Keck/NIRSPEC and Magellan/MMIRS follow-up spectroscopy of Ly{alpha} emitters (LAEs) at z = 2.2 identified in our Subaru narrowband survey. We successfully detect H{alpha} emission from seven LAEs, and perform a detailed analysis of six LAEs free from active galactic nucleus activity, two out of which, CDFS-3865 and COSMOS-30679, have [O II] and [O III] line detections. They are the first [O II]-detected LAEs at high-z, and their [O III]/[O II] ratios and R23-indices provide the first simultaneous determinations of ionization parameter and oxygen abundance for LAEs. CDFS-3865 has a very high ionization parameter (q{sub ion}=2.5{sup +1.7}{sub -0.8} Multiplication-Sign 10{sup 8} cm s{sup -1}) and a low oxygen abundance (12+ log (O/H)=7.84{sup +0.24}{sub -0.25}) in contrast with moderate values of other high-z galaxies such as Lyman break galaxies (LBGs). COSMOS-30679 also possesses a relatively high ionization parameter (q{sub ion}=8{sup +10}{sub -4} Multiplication-Sign 10{sup 7} cm s{sup -1}) and a low oxygen abundance (12+ log (O/H)=8.18{sup +0.28}{sub -0.28}). Both LAEs appear to fall below the mass-metallicity relation of z {approx} 2 LBGs. Similarly, a low metallicity of 12 + log (O/H) < 8.4 is independently indicated for typical LAEs from a composite spectrum and the [N II]/H{alpha} index. Such high ionization parameters and low oxygen abundances can be found in local star-forming galaxies, but this extreme local population occupies only {approx}0.06% of the Sloan Digital Sky Survey spectroscopic galaxy sample with a number density {approx}100 times smaller than that of LAEs. With their high ionization parameters and low oxygen abundances, LAEs would represent an early stage of galaxy formation dominated by massive stars in compact star-forming regions. High-q{sub ion} galaxies like LAEs would produce ionizing photons efficiently with a high escape fraction achieved by density-bounded H II regions, which would significantly contribute to

  5. A Ly{alpha} HALO AROUND A QUASAR AT REDSHIFT z = 6.4

    SciTech Connect

    Willott, Chris J.; Chet, Savironi; Hutchings, John B.; Bergeron, Jacqueline

    2011-12-15

    We present long-slit spectroscopic data that reveal extended Ly{alpha} emission around the z = 6.417 radio-quiet quasar CFHQS J2329-0301. The Ly{alpha} emission is extended over 15 kpc and has a luminosity of >8 Multiplication-Sign 10{sup 36} W, comparable to the most luminous Ly{alpha} halos known. The emission has complex kinematics, in part due to foreground absorption, which only partly covers the extended nebula. The velocity ranges from -500 km s{sup -1} to +500 km s{sup -1}, with a peak remarkably close to the systemic velocity identified by broad Mg II emission of the quasar. There is no evidence for infall or outflow of the halo gas. We speculate that the Ly{alpha} emission mechanism is recombination after quasar photoionization of gas sitting within a high-mass dark matter halo. The immense Ly{alpha} luminosity indicates a higher covering factor of cold gas compared with typical radio-quiet quasars at lower redshift.

  6. ASSEMBLY OF MASSIVE GALAXIES IN A HIGH-z PROTOCLUSTER

    SciTech Connect

    Uchimoto, Yuka K.; Yamada, Toru; Kubo, Mariko; Ichikawa, Takashi; Akiyama, Masayuki; Kajisawa, Masaru; Matsuda, Yuichi; Hayashino, Tomoki; Konishi, Masahiro; Nishimura, Tetsuo; Omata, Koji; Tanaka, Ichi; Suzuki, Ryuji; Tokoku, Chihiro; Yoshikawa, Tomohiro

    2012-05-10

    We present the results of wide-field deep JHK imaging of the SSA22 field using the MOIRCS instrument equipped with the Subaru telescope. The observed field is 112 arcmin{sup 2} in area, which covers the z = 3.1 protocluster characterized by the overdensities of Ly{alpha} emitters (LAEs) and Ly{alpha} blobs (LABs). The 5{sigma} limiting magnitude is K{sub AB} = 24.3. We extract the potential protocluster members from the K-selected sample by using the multi-band photometric-redshift selection as well as the simple color cut for distant red galaxies (DRGs; J - K{sub AB} > 1.4). The surface number density of DRGs in our observed fields shows clear excess compared with those in the blank fields, and the location of the densest area whose projected overdensity is twice the average coincides with the large-scale density peak of LAEs. We also found that K-band counterparts with z{sub phot} {approx_equal} 3.1 are detected for 75% (15/20) of the LABs within their Ly{alpha} halo, and the 40% (8/20) of LABs have multiple components, which gives a direct evidence of the hierarchical multiple merging in galaxy formation. The stellar mass of LABs correlates with their luminosity, isophotal area, and the Ly{alpha} velocity widths, implying that the physical scale and the dynamical motion of Ly{alpha} emission are closely related to their previous star formation activities. Highly dust-obscured galaxies such as hyper extremely red objects (J - K{sub AB} > 2.1) and plausible K-band counterparts of submillimeter sources are also populated in the high-density region.

  7. Measurement of the Relative Intensity of the Ly-(alpha) Lines in Fe 25+

    SciTech Connect

    Wong, K L; Beiersdorfer, P; Reed, K J; Osterheld, A L

    2002-06-18

    The intensity of the polarized Ly-{alpha}{sub 1} (2p{sub 3/2} {yields} 1s{sub 1/2}) transition has been measured relative to that of the unpolarized Ly-{alpha}{sub 2} (2p{sub 1/2} {yields} 1s{sub 1/2}) transition in Fe{sup 25+}. The measurements were made with the Livermore electron beam ion trap EBIT-II for beam energies from threshold to 2.5 times threshold. The results are compared to the corresponding intensity ratio predicted using excitation cross sections from distorted-wave calculations, which includes polarization, the M1(2s{sub 1/2} {yields} 1s{sub 1/2}) transition, and cascade contributions. Discrepancies are found that tend to confirm a recent report of a measurement of the Ly-{alpha} lines in Ti{sup 21+} performed on the Tokyo electron beam ion trap.

  8. X-RAY PROPERTIES OF THE z {approx} 4.5 Ly{alpha} EMITTERS IN THE CHANDRA DEEP FIELD SOUTH REGION

    SciTech Connect

    Zheng, Z. Y.; Wang, J. X.; Finkelstein, S. L.; Finkelstein, K. D.; Malhotra, S.; Rhoads, J. E. E-mail: jxw@ustc.edu.c

    2010-07-20

    We report the first X-ray detection of Ly{alpha} emitters (LAEs) at redshift z {approx} 4.5. One source (J033127.2-274247) is detected in the Extended Chandra Deep Field-South (ECDF-S) X-ray data and has been spectroscopically confirmed as a z = 4.48 quasar with L{sub X} = 4.2 x 10{sup 44} erg s{sup -1}. The single detection gives an Ly{alpha} quasar density of {approx} 2.7{sup +6.2} {sub -2.2} x 10{sup -6} Mpc{sup -3}, consistent with the X-ray luminosity function of quasars. Another 22 LAEs in the central Chandra Deep Field-South region are not detected individually, but their co-added counts yield an S/N = 2.4 (p = 99.83%) detection at soft band, with an effective exposure time of {approx}36 Ms. Further analysis of the equivalent width (EW) distribution shows that all the signals come from 12 LAE candidates with EW{sub rest}< 400 A and 2 of them contribute about half of the signal. From follow-up spectroscopic observations, we find that one of the two is a low-redshift emission-line galaxy, and the other is a Lyman break galaxy at z = 4.4 with little or no Ly{alpha} emission. Excluding these two and combined with ECDF-S data, we derive a 3{sigma} upper limit on the average X-ray flux of F {sub 0.5-2.0keV} < 1.6 x 10{sup -18} erg cm{sup -2} s{sup -1}, which corresponds to an average luminosity of (L {sub 0.5-2keV}) <2.4 x 10{sup 42} erg s{sup -1} for z {approx} 4.5 LAEs. If the average X-ray emission is due to star formation, it corresponds to a star formation rate (SFR) of <180-530 M {sub sun} yr{sup -1}. We use this SFR {sub X} as an upper limit of the unobscured SFR to constrain the escape fraction of Ly{alpha} photons and find a lower limit of f{sub esc,Ly{alpha}} > 3%-10%. However, our upper limit on the SFR {sub X} is {approx}7 times larger than the upper limit on SFR {sub X} on z {approx} 3.1 LAEs in the same field and at least 30 times higher than the SFR estimated from Ly{alpha} emission. From the average X-ray-to-Ly{alpha} line ratio, we estimate that

  9. CHEMISTRY OF A PROTOPLANETARY DISK WITH GRAIN SETTLING AND Ly{alpha} RADIATION

    SciTech Connect

    Fogel, Jeffrey K. J.; Bethell, Thomas J.; Bergin, Edwin A.; Calvet, Nuria; Semenov, Dmitry E-mail: tbethell@umich.edu E-mail: ncalvet@umich.edu

    2011-01-01

    We present results from a model of the chemical evolution of protoplanetary disks. In our models, we directly calculate the changing propagation and penetration of a high energy radiation field with Ly{alpha} radiation included. We also explore the effect on our models of including dust grain settling. We find that, in agreement with earlier studies, the evolution of dust grains plays a large role in determining how deep the UV radiation penetrates into the disk. Significant grain settling at the midplane leads to much smaller freeze-out regions and a correspondingly larger molecular layer, which leads to an increase in column density for molecular species such as CO, CN, and SO. The inclusion of Ly{alpha} radiation impacts the disk chemistry through specific species that have large photodissociation cross sections at 1216 A. These include HCN, NH{sub 3}, and CH{sub 4}, for which the column densities are decreased by an order of magnitude or more due to the presence of Ly{alpha} radiation in the UV spectrum. A few species, such as CO{sub 2} and SO, are enhanced by the presence of Ly{alpha} radiation, but rarely by more than a factor of a few.

  10. THE HANLE EFFECT OF Ly{alpha} IN A MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR TRANSITION REGION

    SciTech Connect

    Stepan, J.; Trujillo Bueno, J.; Carlsson, M.; Leenaarts, J.

    2012-10-20

    In order to understand the heating of the solar corona it is crucial to obtain empirical information on the magnetic field in its lower boundary (the transition region). To this end, we need to measure and model the linear polarization produced by scattering processes in strong UV lines, such as the hydrogen Ly{alpha} line. The interpretation of the observed Stokes profiles will require taking into account that the outer solar atmosphere is highly structured and dynamic, and that the height of the transition region may well vary from one place in the atmosphere to another. Here, we report on the Ly{alpha} scattering polarization signals we have calculated in a realistic model of an enhanced network region, resulting from a state-of-the-art radiation magnetohydrodynamic simulation. This model is characterized by spatially complex variations of the physical quantities at transition region heights. The results of our investigation lead us to emphasize that scattering processes in the upper solar chromosphere should indeed produce measurable linear polarization in Ly{alpha}. More importantly, we show that via the Hanle effect the model's magnetic field produces significant changes in the emergent Q/I and U/I profiles. Therefore, we argue that by measuring the polarization signals produced by scattering processes and the Hanle effect in Ly{alpha} and contrasting them with those computed in increasingly realistic atmospheric models, we should be able to decipher the magnetic, thermal, and dynamic structure of the upper chromosphere and transition region of the Sun.

  11. A DEEP SEARCH FOR CO J = 2-1 EMISSION FROM A Ly{alpha} BLOB AT z {approx} 6.595

    SciTech Connect

    Wagg, Jeff; Kanekar, Nissim

    2012-06-01

    We have used the Green Bank Telescope to carry out a deep search for redshifted CO J = 2-1 line emission from an extended (>17 kpc) Ly{alpha} blob (LAB), 'Himiko', at z {approx} 6.595. Our non-detection of CO J = 2-1 emission places the strong 3{sigma} upper limit of L'{sub CO} < 1.8 Multiplication-Sign 10{sup 10} Multiplication-Sign ({Delta}V/250){sup 1/2} K km s{sup -1} pc{sup 2} on the CO line luminosity. This is comparable to the best current limits on the CO line luminosity in LABs at z {approx} 3 and lower-luminosity Ly{alpha} emitters at z {approx}> 6.5. High-z LABs appear to have lower CO line luminosities than the host galaxies of luminous quasars and submillimeter galaxies at similar redshifts, despite their high stellar mass. Although the CO-to-H{sub 2} conversion factor is uncertain for galaxies in the early universe, we assume X{sub CO} = 0.8 M{sub Sun} (K km s{sup -1} pc{sup 2}){sup -1} to obtain the limit M(H{sub 2}) <1.4 Multiplication-Sign 10{sup 10} M{sub Sun} on Himiko's molecular gas mass; this is a factor of {approx}> 2.5 lower than the stellar mass in the z {approx} 6.595 LAB.

  12. LOGNORMAL INTENSITY DISTRIBUTION OF THE FAR-ULTRAVIOLET CONTINUUM BACKGROUND SHORTWARD OF Ly{alpha}

    SciTech Connect

    Seon, Kwang-Il

    2013-07-20

    The diffuse far-ultraviolet (FUV) continuum radiation 'longward' of Ly{alpha} (1216 A) is well known to correlate with the dust emission at 100 {mu}m. However, it has been claimed that the FUV continuum background 'shortward' of Ly{alpha} shows very weak or no correlation with the 100 {mu}m emission. In this paper, the observational data of the diffuse FUV radiation by the Far Ultraviolet Spectroscopic Explorer (FUSE) are reexamined in order to investigate the correlation between the diffuse FUV radiation shortward of Ly{alpha} and the 100 {mu}m emission. Large fluctuations were confirmed in the linear-linear correlation plots, but good correlations were found in the log-log plots. The large fluctuations in the linear-linear plots, and thus poor correlations, between the FUV and 100 {mu}m intensities were attributed to the lognormal property of the FUV intensity distribution. The standard deviation of the intensity distribution of the FUV radiation shortward of Ly{alpha} was found to be {sigma}{sub logI} = 0.16-0.25. The result is consistent with that obtained not only for the FUV radiation longward of 1216 A but also with the dust column density measurements of various molecular clouds. This implies that most of the diffuse FUV radiation shortward of Ly{alpha} is dust-scattered light in the turbulent interstellar medium. The diffuse FUV data obtained from the Voyager missions were also investigated. However, much wider random fluctuations were found compared with the FUSE data, which is most likely due to the systematic difficulties in data reduction of the Voyager data.

  13. Monitoring Ly-Alpha Emission From the Blazar 3C 279

    NASA Technical Reports Server (NTRS)

    Koratkar, Anuradha; Pian, Elena; Urry, C. Megan; Pesce, Joseph E.

    1998-01-01

    The blazar 3C 279 is well studied and shows frequent large continuum flares from radio to gamma-ray wavelengths. There have been a number of multiwavelength observations of 3C 279, and hence there are extensive ultraviolet data for this object available in the UV archives. In this paper we present Ly-alpha emission line measurements for 3C 279 using all the archival IUE SWP spectra from 1988 to 1996 and all archival Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) G190H spectra from 1992 to 1996. Individual archival IUE spectra of 3C 279 show weak Ly-alpha emission at approximately 1868 A (z = 0.536), which is easily seen in the co-added data. The Ly-alpha emission is observed in all the HST/FOS spectra. The strength of Ly-alpha is nearly constant (approximately 5 x 10(exp -14) erg/sq cm.s), while the 1750 A continuum varies by a factor of approximately 50, from approximately 0.6 to 31.6 x 10(exp -15) ergs/sq cm.s.A. The behavior of the Ly-alpha emission line flux and continuum flux is similar to that of the only other well observed blazar, 3C 273, which shows constant line flux while the continuum varies by a factor of approximately 3. This near-constancy of emission-line flux in the two best-studied blazars suggests that the highly variable beamed continuum is not a significant source of photoionization for the gas. Some other source, such as thermal emission from an accretion disk, must be providing a significant fraction of the photoionizing flux in these objects. The large amplitude variability seen at gamma-ray energies must be due to changes in the energetic electrons in the jet rather than changes in the external photon field.

  14. CONSTRAINTS ON HYPERLUMINOUS QSO LIFETIMES VIA FLUORESCENT Ly{alpha} EMITTERS AT Z {approx_equal} 2.7

    SciTech Connect

    Trainor, Ryan; Steidel, Charles C.

    2013-09-20

    We present observations of a population of Ly{alpha} emitters (LAEs) exhibiting fluorescent emission via the reprocessing of ionizing radiation from nearby hyperluminous QSOs. These LAEs are part of a survey at redshifts 2.5 < z < 2.9 combining narrow-band photometric selection and spectroscopic follow-up to characterize the emission mechanisms, physical properties, and three-dimensional locations of the emitters with respect to their nearby hyperluminous QSOs. These data allow us to probe the radiation field, and thus the radiative history, of the QSOs, and we determine that most of the eight QSOs in our sample have been active and of comparable luminosity for a time 1 Myr {approx}< t{sub Q} {approx}< 20 Myr. Furthermore, we find that the ionizing QSO emission must have an opening angle {theta} {approx} 30 Degree-Sign or larger relative to the line of sight.

  15. A GRAVITATIONAL LENS MODEL FOR THE Ly{alpha} EMITTER LAE 221724+001716 AT z = 3.1 IN THE SSA 22 FIELD {sup ,}

    SciTech Connect

    Nakahiro, Y.; Kajisawa, M.; Tanaka, A. R.; Hamada, K.; Taniguchi, Y.; Shioya, Y.; Kobayashi, M. A. R.; Inoue, A. K.; Iwata, I.; Matsuda, Y.; Hayashino, T.

    2013-04-01

    During the course of our Lyman continuum imaging survey, we found that the spectroscopically confirmed Ly{alpha} emitter LAE 221724+001716 at z = 3.10 in the SSA 22 field shows strong Lyman continuum emission ({lambda}{sub rest} {approx} 900 A) that escapes from this galaxy. However, another recent spectroscopic survey revealed that the supposed Lyman continuum emission could arise from a foreground galaxy at z = 1.76 if the emission line newly detected from the galaxy at {lambda}{sub obs} Almost-Equal-To 3360 A is Ly{alpha}. If this is the case, as the angular separation between these two galaxies is very small ( Almost-Equal-To 0.''6), LAE 221724+001716 at z = 3.10 could be amplified by the gravitational lensing caused by this intervening galaxy. Here we present a possible gravitational lens model for the system of LAE 221724+001716. First, we estimate the stellar mass of the intervening galaxy as M{sub *} {approx} 3.5 Multiplication-Sign 10{sup 9} M{sub Sun} from its UV luminosity and {approx}3.0 Multiplication-Sign 10{sup 7}-2.4 Multiplication-Sign 10{sup 9} M{sub Sun} through the spectral energy distribution fitting. Then, we find that the gravitational magnification factor ranges from 1.01 to 1.16 using the so-called singular isothermal sphere model for strong lensing. While LAE 221724+001716 is the first system of an LAE-LAE lensing reported so far, the estimated magnification factor is not so significant because the stellar mass of the intervening galaxy is small.

  16. THE CURIOUS CASE OF Ly{alpha} EMITTERS: GROWING YOUNGER FROM z {approx} 3 to z {approx} 2?

    SciTech Connect

    Acquaviva, Viviana; Vargas, Carlos; Gawiser, Eric; Guaita, Lucia

    2012-06-01

    Ly{alpha} emitting (LAE) galaxies are thought to be progenitors of present-day L* galaxies. Clustering analyses have suggested that LAEs at z {approx} 3 might evolve into LAEs at z {approx} 2, but it is unclear whether the physical nature of these galaxies is compatible with this hypothesis. Several groups have investigated the properties of LAEs using spectral energy distribution (SED) fitting, but direct comparison of their results is complicated by inconsistencies in the treatment of the data and in the assumptions made in modeling the stellar populations, which are degenerate with the effects of galaxy evolution. By using the same data analysis pipeline and SED fitting software on two stacked samples of LAEs at z = 3.1 and z = 2.1, and by eliminating several systematic uncertainties that might cause a discrepancy, we determine that the physical properties of these two samples of galaxies are dramatically different. LAEs at z = 3.1 are found to be old (age {approx}1 Gyr) and metal-poor (Z < 0.2 Z{sub Sun }), while LAEs at z = 2.1 appear to be young (age {approx}50 Myr) and metal-rich (Z > Z{sub Sun }). The difference in the observed stellar ages makes it very unlikely that z 3.1 LAEs evolve directly into z = 2.1 LAEs. Larger samples of galaxies, studies of individual objects, and spectroscopic measurements of metallicity at these redshifts are needed to confirm this picture, which is difficult to reconcile with the effects of 1 Gyr of cosmological evolution.

  17. A Faraday rotation search for magnetic fields in quasar damped Ly alpha absorption systems

    NASA Technical Reports Server (NTRS)

    Oren, Abraham L.; Wolfe, Arthur M.

    1995-01-01

    We present the results of a Faraday rotation survey of 61 radio-bright QSOs conducted at the National Radio Astronomy Observatory (NRAO) Very Large Array (VLA). The Galactic contribution to the Faraday rotation is estimated and subtracted to determine the extragalactic rotation measure (RRM) for each source. Eleven of these QSOs are known to exhibit damped Ly alpha absorption. The rate of incidence of significant Faraday rotation of these 11 sources is compared to the remaining 50 and is found to be higher at the 99.8% confidence level. However, as this is based upon only two detections of Faraday rotation in the damped Ly alpha sample, the result is only tentative. If the two detections in the damped Ly alpha sample are dug to the absorbing systems, then the inferred rotation measure induced by these systems is roughly 250 rad/sq m. The two detections were for the two lowest redshift absorbers in the sample. We find that a rotation measure of 250 rad/sq m would have gone undetected for any other absorber in the damped Ly alpha sample due to the 1/(1 + 2) squared dilution of the observed RRM with redshift. Thus the data are consistent with, but do not prove, the hypothesis that Faraday rotation is a generic property of damped Ly alpha absorbers. We do not confirm the suggestion that the amplitude of RRMs increases with redshift. Rather, the data are consistent with no redshift evolution. We find that the uncertainty in the estimation of the Galactic rotation measure (GRM) is a more serious problem than previously realized for extra-galactic Faraday rotation studies of QSO absorbers. A careful analysis of current methods for estimating GRM indicate that it can be determined to an accuracy of about 15 - 20 rad/sq m. Previous studies underestimated this uncertainty by more than a factor of 2. Due to this uncertainty, rotation measures such as we suspect are associated with damped Ly alpha absorption systems can only be detected at redshifts less than z approximately

  18. EFFECT OF DUST ON Ly{alpha} PHOTON TRANSFER IN AN OPTICALLY THICK HALO

    SciTech Connect

    Yang Yang; Shu Chiwang; Roy, Ishani; Fang Lizhi

    2011-10-01

    We investigate the effects of dust on Ly{alpha} photons emergent from an optically thick medium by solving the integro-differential equation of radiative transfer of resonant photons. To solve the differential equations numerically, we use the weighted essentially non-oscillatory method. Although the effects of dust on radiative transfer are well known, the resonant scattering of Ly{alpha} photons makes the problem non-trivial. For instance, if the medium has an optical depth of dust absorption and scattering of {tau}{sub a} >> 1, {tau} >> 1, and {tau} >> {tau}{sub a}, the effective absorption optical depth in a random walk scenario would be equal to {radical}({tau}{sub a}({tau}{sub a}+{tau})). We show, however, that for a resonant scattering at frequency {nu}{sub 0}, the effective absorption optical depth would be even larger than {tau}({nu}{sub 0}). If the cross section of dust scattering and absorption is frequency-independent, the double-peaked structure of the frequency profile given by the resonant scattering is basically dust-independent. That is, dust causes neither narrowing nor widening of the width of the double-peaked profile. One more result is that the timescales of the Ly{alpha} photon transfer in an optically thick halo are also basically independent of the dust scattering, even when the scattering is anisotropic. This is because those timescales are mainly determined by the transfer in the frequency space, while dust scattering, either isotropic or anisotropic, does not affect the behavior of the transfer in the frequency space when the cross section of scattering is wavelength-independent. This result does not support the speculation that dust will lead to the smoothing of the brightness distribution of a Ly{alpha} photon source with an optically thick halo.

  19. NEUTRAL HYDROGEN OPTICAL DEPTH NEAR STAR-FORMING GALAXIES AT z Almost-Equal-To 2.4 IN THE KECK BARYONIC STRUCTURE SURVEY

    SciTech Connect

    Rakic, Olivera; Schaye, Joop; Steidel, Charles C.; Rudie, Gwen C.

    2012-06-01

    We study the interface between galaxies and the intergalactic medium by measuring the absorption by neutral hydrogen in the vicinity of star-forming galaxies at z Almost-Equal-To 2.4. Our sample consists of 679 rest-frame UV-selected galaxies with spectroscopic redshifts that have impact parameters <2 (proper) Mpc to the line of sight of one of the 15 bright, background QSOs and that fall within the redshift range of its Ly{alpha} forest. We present the first two-dimensional maps of the absorption around galaxies, plotting the median Ly{alpha} pixel optical depth as a function of transverse and line-of-sight separation from galaxies. The Ly{alpha} optical depths are measured using an automatic algorithm that takes advantage of all available Lyman series lines. The median optical depth, and hence the median density of atomic hydrogen, drops by more than an order of magnitude around 100 kpc, which is similar to the virial radius of the halos thought to host the galaxies. The median remains enhanced, at the >3{sigma} level, out to at least 2.8 Mpc (i.e., >9 comoving Mpc), but the scatter at a given distance is large compared with the median excess optical depth, suggesting that the gas is clumpy. Within 100 (200) kpc, and over {+-}165 km s{sup -1}, the covering fraction of gas with Ly{alpha} optical depth greater than unity is 100{sup +0}{sub -32}% (66% {+-} 16%). Absorbers with {tau}{sub Ly{alpha}} > 0.1 are typically closer to galaxies than random. The mean galaxy overdensity around absorbers increases with the optical depth and also as the length scale over which the galaxy overdensity is evaluated is decreased. Absorbers with {tau}{sub Ly{alpha}} {approx} 1 reside in regions where the galaxy number density is close to the cosmic mean on scales {>=}0.25 Mpc. We clearly detect two types of redshift space anisotropies. On scales <200 km s{sup -1}, or <1 Mpc, the absorption is stronger along the line of sight than in the transverse direction. This 'finger of God

  20. CHEMICAL ENRICHMENT OF DAMPED Ly{alpha} SYSTEMS AS A DIRECT CONSTRAINT ON POPULATION III STAR FORMATION

    SciTech Connect

    Kulkarni, Girish; Hennawi, Joseph F.; Rollinde, Emmanuel; Vangioni, Elisabeth

    2013-08-01

    Observations of damped Ly{alpha} absorbers (DLAs) can be used to measure gas-phase metallicities at large cosmological look-back times with high precision. Furthermore, relative abundances can still be measured accurately deep into the reionization epoch (z > 6) using transitions redward of Ly{alpha}, even though Gunn-Peterson absorption precludes measurement of neutral hydrogen. In this paper, we study the chemical evolution of DLAs using a model for the coupled evolution of galaxies and the intergalactic medium (IGM), which is constrained by a variety of observations. Our goal is to explore the influence of Population III stars on the abundance patterns of DLAs to determine the degree to which abundance measurements can discriminate between different Population III stellar initial mass functions (IMFs). We include effects, such as inflows onto galaxies due to cosmological accretion and outflows from galaxies due to supernova feedback. A distinct feature of our model is that it self-consistently calculates the effect of Population III star formation on the reionization of an inhomogeneous IGM, thus allowing us to calculate the thermal evolution of the IGM and implement photoionization feedback on low-mass galaxy formation. We find that if the critical metallicity of Population III to II/I transition is {approx}< 10{sup -4} Z{sub Sun }, then the cosmic Population III star formation rate drops to zero for z < 8. Nevertheless, at high redshift (z {approx} 6), chemical signatures of Population III stars remain in low-mass galaxies (halo mass {approx}< 10{sup 9} M{sub Sun }). This is because photoionization feedback suppresses star formation in these galaxies until relatively low redshift (z {approx} 10), and the chemical record of their initial generation of Population III stars is retained. We model DLAs as these low-mass galaxies, and assign to them a mass-dependent H I absorption cross-section in order to predict the expected distribution of DLA abundance ratios

  1. High-redshift Insights from Low-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Hayes, Matthew; Östlin, Göran; Schaerer, Daniel; Mas-Hesse, J. Miguel; Melinder, Jens; Verhamme, Anne; Orlitova, Ivana; Cannon, John M.; Herenz, E. Christian; Adamo, Angela

    2015-08-01

    I will summarize results from an extensive multi-wavelength observational campaign to dissect local star-forming galaxies. The Lyman alpha Reference Sample, LARS, comprises ~55 local systems, selected in various ways (FUV luminosity, IR luminosity, H-alpha EW) to provide the closest analogues systems for galaxies that are routinely discovered in high-z surveys and dominate cosmic star formation at various epochs beyond z of 1. The data-set is complete with 8 band HST imaging (5 broadband, plus H-alpha, H-beta, and Ly-alpha narrowbands), HST/COS ultraviolet spectroscopy, direct HI measurements from 21 cm interferometry (GMRT and J-VLA), optical integral field spectroscopy (CAHA/PMAS or VLT/MUSE), far IR emission lines (Herschel or SOFIA), and more.For this talk I will focus on kinematic measurements in warm-ionized, warm-neutral, and cold-neutral interstellar media. I will discuss feedback from massive stars, and how local gas kinematics and ionization states is connected to the properties of the massive stellar population. I will also discuss the extended halos of Ly-alpha that arise when large HI envelopes scatter the radiation produced by recombinations in the HII. I will quantify the extents of Ly-alpha scattering halos, and contrast these with direct observations of HI, HII, and metal lines to show how the halos arise under certain conditions in the ionized and neutral media. With results from low-z galaxies in place I will discuss the validity of using Ly-alpha and UV absorption lines for measuring the properties of gas in the circumgalactic medium of high-z galaxies.

  2. Confirmation of a Steep Luminosity Function for Ly alpha Emitters at z 5.7: a Major Component of Reionization

    NASA Technical Reports Server (NTRS)

    Dressler, Alan; Henry, Alaina L.; Martin, Crystal L.; Sawicki, Marcin; McCarthy, Patrick; Villaneuva, Edward

    2014-01-01

    We report the first direct and robust measurement of the faint-end slope of the Ly-alpha emitter (LAE) luminosity function at z = 5.7. Candidate LAEs from a low-spectral-resolution blind search with IMACS on Magellan- Baade were targeted at higher resolution to distinguish high redshift LAEs from foreground galaxies. All but 2 of our 42 single-emission-line systems are fainter than F = 2.0×10(exp-17) ergs s(exp-1) cm(exp-2), making these the faintest emission-lines observed for a z = 5.7 sample with known completeness, an essential property for determining the faint end slope of the LAE luminosity function. We find 13 LAEs as compared to 29 foreground galaxies, in very good agreement with the modeled foreground counts predicted in Dressler et al. (2011a) that had been used to estimate a faint-end slope of alpha = -2.0 for the LAE luminosity function. A 32% LAE fraction, LAE/(LAE+foreground) within the flux interval F = 2-20 × 10(exp-18) ergs s(exp-1) cm(exp-2) constrains the faint end slope of the luminosity function to -1.95 greater than alpha greater than -2.35 (1 delta). We show how this steep LF should provide, to the limit of our observations, more than 20% of the flux necessary to maintain ionization at z = 5.7, with a factor-of-ten extrapolation in flux reaching more than 55%. We suggest that this bodes well for a comparable contribution by similar, low-mass star forming galaxies at higher-redshift - within the reionization epoch at z greater than approximately 7, only 250 Myr earlier - and that such systems provide a substantial, if not dominant, contribution to the late-stage reionization of the IGM.

  3. MEAN-FLUX-REGULATED PRINCIPAL COMPONENT ANALYSIS CONTINUUM FITTING OF SLOAN DIGITAL SKY SURVEY Ly{alpha} FOREST SPECTRA

    SciTech Connect

    Lee, Khee-Gan; Spergel, David N.; Suzuki, Nao

    2012-02-15

    Continuum fitting is an important aspect of Ly{alpha} forest science, since errors in the derived optical depths scale with the fractional continuum error. However, traditional methods of estimating continua in noisy and moderate-resolution spectra (e.g., Sloan Digital Sky Survey, SDSS; S/N {approx}< 10 pixel{sup -1} and R {approx} 2000), such as power-law extrapolation or dividing by the mean spectrum, achieve no better than {approx}15% rms accuracy. To improve on this, we introduce mean-flux-regulated principal component analysis (MF-PCA) continuum fitting. In this technique, PCA fitting is carried out redward of the quasar Ly{alpha} line in order to provide a prediction for the shape of the Ly{alpha} forest continuum. The slope and amplitude of this continuum prediction is then corrected using external constraints for the Ly{alpha} forest mean flux. This requires prior knowledge of the mean flux, (F), but significantly improves the accuracy of the flux transmission, F {identical_to} exp (- {tau}), estimated from each pixel. From tests on mock spectra, we find that MF-PCA reduces the errors to 8% rms in S/N {approx} 2 spectra, and <5% rms in spectra with S/N {approx}> 5. The residual Fourier power in the continuum is decreased by a factor of a few in comparison with dividing by the mean continuum, enabling Ly{alpha} flux power spectrum measurements to be extended to {approx}2 Multiplication-Sign larger scales. Using this new technique, we make available continuum fits for 12,069 z > 2.3 Ly{alpha} forest spectra from SDSS Data Release 7 for use by the community. This technique is also applicable to future releases of the ongoing Baryon Oscillations Spectroscopic Survey, which obtains spectra for {approx}150, 000 Ly{alpha} forest spectra at low signal-to-noise (S/N {approx} 2).

  4. SEARCHING FOR z {approx} 7.7 Ly{alpha} EMITTERS IN THE COSMOS FIELD WITH NEWFIRM

    SciTech Connect

    Krug, Hannah B.; Veilleux, Sylvain; Tilvi, Vithal; Malhotra, Sangeeta; Rhoads, James; Hibon, Pascale; Swaters, Rob

    2012-02-01

    The study of Ly{alpha} emission in the high-redshift universe is a useful probe of the epoch of reionization, as the Ly{alpha} line should be attenuated by the intergalactic medium (IGM) at low to moderate neutral hydrogen fractions. Here we present the results of a deep and wide imaging search for Ly{alpha} emitters in the Cosmological Evolution Survey field. We have used two ultra-narrowband filters (filter width of {approx}8-9 A) on the NOAO Extremely Wide-Field Infrared Mosaic camera, installed on the Mayall 4 m telescope at Kitt Peak National Observatory, in order to isolate Ly{alpha} emitters at z = 7.7; such ultra-narrowband imaging searches have proved to be excellent at detecting Ly{alpha} emitters. We found 5{sigma} detections of four candidate Ly{alpha} emitters in a survey volume of 2.8 Multiplication-Sign 10{sup 4} Mpc{sup 3} (total survey area {approx}760 arcmin{sup 2}). Each candidate has a line flux greater than 8 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2}. Using these results to construct a luminosity function and comparing to previously established Ly{alpha} luminosity functions at z = 5.7 and z = 6.5, we find no conclusive evidence for evolution of the luminosity function between z = 5.7 and z = 7.7. Statistical Monte Carlo simulations suggest that half of these candidates are real z = 7.7 targets, and spectroscopic follow-up will be required to verify the redshift of these candidates. However, our results are consistent with no strong evolution in the neutral hydrogen fraction of the IGM between z = 5.7 and z = 7.7, even if only one or two of the z = 7.7 candidates are spectroscopically confirmed.

  5. METALLICITY EVOLUTION OF DAMPED Ly{alpha} SYSTEMS OUT TO z {approx} 5

    SciTech Connect

    Rafelski, Marc; Wolfe, Arthur M.; Neeleman, Marcel; Mendez, Alexander J.; Prochaska, J. Xavier

    2012-08-20

    We present chemical abundance measurements for 47 damped Ly{alpha} (DLA) systems, 30 at z > 4, observed with the Echellette Spectrograph and Imager and the High Resolution Echelle Spectrometer on the Keck telescopes. H I column densities of the DLAs are measured with Voigt profile fits to the Ly{alpha} profiles, and we find an increased number of false DLA identifications with Sloan Digital Sky Survey at z > 4 due to the increased density of the Ly{alpha} forest. Ionic column densities are determined using the apparent optical depth method, and we combine our new metallicity measurements with 195 from previous surveys to determine the evolution of the cosmic metallicity of neutral gas. We find the metallicity of DLAs decreases with increasing redshift, improving the significance of the trend and extending it to higher redshifts, with a linear fit of -0.22 {+-} 0.03 dex per unit redshift from z = 0.09-5.06. The metallicity 'floor' of Almost-Equal-To 1/600 solar continues out to z {approx} 5, despite our sensitivity for finding DLAs with much lower metallicities. However, this floor is not statistically different from a steep tail to the distribution. We also find that the intrinsic scatter of metallicity among DLAs of {approx}0.5 dex continues out to z {approx} 5. In addition, the metallicity distribution and the {alpha}/Fe ratios of z > 2 DLAs are consistent with being drawn from the same parent population with those of halo stars. It is therefore possible that the halo stars in the Milky Way formed out of gas that commonly exhibits DLA absorption at z > 2.

  6. CONSTRAINTS ON QUASAR LIFETIMES AND BEAMING FROM THE He II Ly{alpha} FOREST

    SciTech Connect

    Furlanetto, Steven R.; Lidz, Adam

    2011-07-10

    We show that comparisons of He II Ly{alpha} forest lines of sight to nearby quasar populations can strongly constrain the lifetimes and emission geometry of quasars. By comparing the He II and H I Ly{alpha} forests along a particular line of sight, one can trace fluctuations in the hardness of the radiation field (which are driven by fluctuations in the He II ionization rate). Because this high-energy background is highly variable-thanks to the rarity of the bright quasars that dominate it and the relatively short attenuation lengths of these photons-it is straightforward to associate features in the radiation field with their source quasars. Here we quantify how finite lifetimes and beamed emission geometries affect these expectations. Finite lifetimes induce a time delay that displaces the observed radiation peak relative to the quasar. For beamed emission, geometry dictates that sources invisible to the observer can still create a peak in the radiation field. We show that both these models produce substantial populations of 'bare' peaks (without an associated quasar) for reasonable parameter values (lifetimes {approx}10{sup 6}-10{sup 8} yr and beaming angles {approx}< 90 deg.). A comparison to existing quasar surveys along two He II Ly{alpha} forest lines of sight rules out isotropic emission and infinite lifetime at high confidence; they can be accommodated either by moderate beaming or lifetimes {approx}10{sup 7}-10{sup 8} yr. We also show that the distribution of radial displacements between peaks and their quasars can unambiguously distinguish these two models, although larger statistical samples are needed.

  7. THRESHOLD PROBABILITY FUNCTIONS AND THERMAL INHOMOGENEITIES IN THE Ly{alpha} FOREST

    SciTech Connect

    Lee, Khee-Gan; Spergel, David N. E-mail: dns@astro.princeton.edu

    2011-06-10

    We introduce to astrophysics the threshold probability functions S{sub 2}, C{sub 2}, and D{sub 2} first derived by Torquato et al., which effectively samples the flux probability distribution function (PDF) of the Ly{alpha} forest at different spatial scales. These statistics are tested on mock Ly{alpha} forest spectra based on various toy models for He II reionization, with homogeneous models with various temperature-density relations as well as models with temperature inhomogeneities. These mock samples have systematics and noise added to simulate the latest Sloan Digital Sky Survey Data Release 7 (SDSS DR7) data. We find that the flux PDF from SDSS DR7 can be used to constrain the temperature-density relation {gamma} (where T{proportional_to}(1 + {Delta}){sup {gamma}-1}) of the intergalactic medium (IGM) at z = 2.5 to a precision of {Delta}{gamma} = 0.2 at {approx}4{sigma} confidence. The flux PDF is degenerate to temperature inhomogeneities in the IGM arising from He II reionization, but we find S{sub 2} can detect these inhomogeneities at {approx}3{sigma}, with the assumption that the flux continuum of the Ly{alpha} forest can be determined to 9% accuracy, approximately the error from current fitting methods. If the flux continuum can be determined to 3% accuracy, then S{sub 2} is capable of constraining the characteristic scale of temperature inhomogeneities, with {approx}4{sigma} differentiation between toy models with hot bubble radii of 50 h{sup -1} Mpc and 25 h{sup -1} Mpc.

  8. BROAD Ly{alpha} EMISSION FROM THREE NEARBY BL LACERTAE OBJECTS

    SciTech Connect

    Stocke, John T.; Danforth, Charles W.; Perlman, Eric S. E-mail: stocke@casa.colorado.edu

    2011-05-10

    We present far-UV HST/COS spectra of four nearby BL Lac objects. BL Lac spectra are dominated by a smooth, power-law continuum which arises in a relativistic jet. However, the spectra are not necessarily featureless; weak, broad- and/or narrow-line emission is sometimes seen in high-quality optical spectra. We present detections of Ly{alpha} emission in HST/COS spectra of Mrk 421 (z = 0.030) and PKS 2005-489 (z = 0.071) as well as an archival HST/GHRS observation of Mrk 501 (z = 0.0337). Archival HST/STIS observations of PKS 2155-304 (z = 0.116) show no Ly{alpha} emission to a very low upper limit. Using the assumption that the broad-line region (BLR) clouds are symmetrically placed around the active galactic nucleus (AGN), we use these measured Ly{alpha} emission features to constrain either the relativistic {Gamma} values for the ionizing continuum produced by the jet (in the ionization-bounded case) or the mass of warm gas (in the density-bounded case). While realistic {Gamma} values can be obtained for all four cases, the values for Mrk 421 and PKS 2155-304 are high enough to suggest that covering factors of BLR clouds of {approx}1%-2% might be required to provide consistency with earlier values of Doppler boosting and viewing angles suggested for this class of BL Lacs. This discrepancy also exists in the case of M 87, where the amount of Doppler boosting in our direction is expected to be minimal, again suggestive of a small covering factor of BLR clouds. If, as these small covering factors might suggest, the assumptions of a density-bounded model could be more correct, then the observed Ly{alpha} luminosities require that BL Lac/FR 1 nuclei possess very little warm gas (10{sup -4} to 10{sup -5} M{sub sun}) as suggested by Guilbert et al. If these clouds are in pressure balance with a hotter ({approx}10{sup 6} K) gas, the BLR contains too little mass to power the AGN by accretion alone.

  9. Lyman alpha radiation in external galaxies

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Mckee, Christopher F.

    1990-01-01

    The Ly alpha line of atomic hydrogen is often a luminous component of the radiation emitted by distant galaxies. Except for those galaxies which have a substantial central source of non-stellar ionizing radiation, most of the Ly alpha radiation emitted by galaxies is generated within regions of the interstellar medium which are photoionized by starlight. Conversely, much of the energy radiated by photoionized regions is carried by the Ly alpha line. Only hot, massive stars are capable of ionizing hydrogen in the interstellar medium which surrounds them, and because such stars are necessarily short-lived, Ly alpha emission traces regions of active star formation. Researchers argue that the strength of the Ly alpha emission observed from external galaxies may be used to estimate quantitatively the dust content of the emitting region, while the Ly alpha line profile is sensitive to the presence of shock waves. Interstellar dust particles and shock waves are intimately associated with the process of star formation in two senses. First, both dust particles and shock waves owe their existence to stellar activity; second, they may both serve as agents which facilitate the formation of stars, shocks by triggering gravitational instabilities in the interstellar gas that they compress, and dust by shielding star-forming molecular clouds from the ionizing and dissociative effects of external UV radiation. By using Ly alpha observations as a probe of the dust content in diffuse gas at high redshift, we might hope to learn about the earliest epochs of star formation.

  10. The Dust-to-Gas Ratio in the Damped Ly alpha Clouds Towards the Gravitationally Lensed QSO 0957+561

    NASA Technical Reports Server (NTRS)

    Zuo, Lin; Beaver, E. A.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Lyons, R. W.

    1997-01-01

    We present HST/FOS spectra of the two bright images (A and B) of the gravitationally lensed QSO 0957+561 in the wavelength range 2200-3300 A. We find that the absorption system (Z(sub abs)) = 1.3911) near z(sub em) is a weak, damped Ly alpha system with strong Ly alpha absorption lines seen in both images. However, the H(I) column densities are different, with the line of sight to image A intersecting a larger column density. The continuum shapes of the two spectra differ in the sense that the flux level of image A increases more slowly toward shorter wavelengths than that of image B. We explain this as the result of differential reddening by dust grains in the damped Ly alpha absorber. A direct outcome of this explanation is a determination of the dust-to-gas ratio, k, in the damped Ly alpha system. We derive k = 0.55 + 0.18 for a simple 1/lambda extinction law and k = 0.31 + 0.10 for the Galactic extinction curve. For gravitationally lensed systems with damped Ly alpha absorbers, our method is a powerful tool for determining the values and dispersion of k, and the shapes of extinction curves, especially in the FUV and EUV regions. We compare our results with previous work.

  11. SYSTEMATIC CONTINUUM ERRORS IN THE Ly{alpha} FOREST AND THE MEASURED TEMPERATURE-DENSITY RELATION

    SciTech Connect

    Lee, Khee-Gan

    2012-07-10

    Continuum fitting uncertainties are a major source of error in estimates of the temperature-density relation (usually parameterized as a power-law, T {proportional_to} {Delta}{sup {gamma}-1}) of the intergalactic medium through the flux probability distribution function (PDF) of the Ly{alpha} forest. Using a simple order-of-magnitude calculation, we show that few percent-level systematic errors in the placement of the quasar continuum due to, e.g., a uniform low-absorption Gunn-Peterson component could lead to errors in {gamma} of the order of unity. This is quantified further using a simple semi-analytic model of the Ly{alpha} forest flux PDF. We find that under(over)estimates in the continuum level can lead to a lower (higher) measured value of {gamma}. By fitting models to mock data realizations generated with current observational errors, we find that continuum errors can cause a systematic bias in the estimated temperature-density relation of ({delta}({gamma})) Almost-Equal-To -0.1, while the error is increased to {sigma}{sub {gamma}} Almost-Equal-To 0.2 compared to {sigma}{sub {gamma}} Almost-Equal-To 0.1 in the absence of continuum errors.

  12. Effects of excitation laser wavelength on Ly-{alpha} and He-{alpha} line emission from nitrogen plasmas

    SciTech Connect

    Harilal, S. S.; Miloshevsky, G. V.; Sizyuk, T.; Hassanein, A.

    2013-01-15

    Laser-produced nitrogen plasmas emitting radiation at 2.48 nm (Ly-{alpha}) and 2.88 nm (He-{alpha}) are considered potential efficient sources for water-window (WW) microscopy. The atomic and optical properties of nitrogen plasma and influence of the laser wavelength on the line emission in the WW range are investigated. It is found that the optimal temperatures for maximum emission from Ly-{alpha} and He-{alpha} spectral lines are 40-60 eV and 80-100 eV, respectively. The WW line emission and the conversion efficiency (CE) are estimated for three distinct Nd:YAG laser wavelengths (1064 nm, 532 nm, and 266 nm). The calculated CEs are compared with experimentally observed CE values. It is found that 1064 nm wavelength provides the highest CE from laser to Ly-{alpha} and He-{alpha} radiation.

  13. SEARCH FOR z {approx} 6.96 Ly{alpha} EMITTERS WITH MAGELLAN/IMACS IN THE COSMOS FIELD

    SciTech Connect

    Hibon, P.; Malhotra, S.; Rhoads, J.; Willott, C.

    2011-11-10

    We report a search for z {approx} 6.96 Ly{alpha} emitters (LAEs) using a narrowband filter, centered at 9680 A with the Inamori-Magellan Area Camera and Spectrograph instrument on the Magellan telescope at Las Campanas Observatory. We obtain a sample of six LAE candidates of luminosity {approx}10{sup 42} erg s{sup -1} in a total area of 465 arcmin{sup 2} corresponding to a comoving volume of {approx}72,000 Mpc{sup 3}. From this result, we derive a Ly{alpha} luminosity function (LF) at z {approx} 6.96 and compare our sample with the only z {approx} 6.96 LAE spectroscopically confirmed to date. We find no evolution between the z = 5.7 and z {approx} 7 Ly{alpha} LFs if a majority of our candidates are confirmed. Spectroscopic confirmation for this sample will enable more robust conclusions.

  14. THE REST-FRAME ULTRAVIOLET SPECTRA OF UV-SELECTED ACTIVE GALACTIC NUCLEI AT z {approx} 2-3

    SciTech Connect

    Hainline, Kevin N.; Shapley, Alice E.; Greene, Jenny E.; Steidel, Charles C.

    2011-05-20

    We present new results for a sample of 33 narrow-lined UV-selected active galactic nuclei (AGNs), identified in the course of a spectroscopic survey for star-forming galaxies at z {approx} 2-3. The rest-frame UV composite spectrum for our AGN sample shows several emission lines characteristic of AGNs, as well as interstellar absorption features detected in star-forming Lyman break galaxies (LBGs). We report a detection of N IV] {lambda}1486, which has been observed in high-redshift radio galaxies, as well as in rare optically selected quasars. The UV continuum slope of the composite spectrum is significantly redder than that of a sample of non-AGN UV-selected star-forming galaxies. Blueshifted Si IV absorption provides evidence for outflowing highly ionized gas in these objects at speeds of {approx}10{sup 3} km s{sup -1}, quantitatively different from what is seen in the outflows of non-AGN LBGs. Grouping the individual AGNs by parameters such as the Ly{alpha} equivalent width, redshift, and UV continuum magnitude allows for an analysis of the major spectroscopic trends within the sample. Stronger Ly{alpha} emission is coupled with weaker low-ionization absorption, which is similar to what is seen in the non-AGN LBGs, and highlights the role that cool interstellar gas plays in the escape of Ly{alpha} photons. However, the AGN composite does not show the same trends between Ly{alpha} strength and extinction seen in the non-AGN LBGs. These results represent the first such comparison at high redshift between star-forming galaxies and similar galaxies that host AGN activity.

  15. The Influence of the Photoionizing Radiation Spectrum on Metal-Line Ratios in Ly(alpha) Forest Clouds

    NASA Technical Reports Server (NTRS)

    Giroux, Mark L.; Shull, J. Michael

    1997-01-01

    Recent measurements of Si IV/C IV ratios in the high-redshift Ly(alpha) forest (Songaila & Cowie, AJ, 112, 335 (1996a); Savaglio et at., A&A (in press) (1997)) have opened a new window on chemical enrichment and the first generations of stars. However, the derivation of accurate Si/C abundances requires reliable ionization corrections, which are strongly dependent on the spectral shape of the metagalactic ionizing background and on the 'local effects' of hot stars in nearby galaxies. Recent models have assumed power-law quasar ionizing backgrounds plus a decrement at 4 Ryd to account for He II attenuation in intervening clouds. However, we show that realistic ionizing backgrounds based on cosmological radiative transfer models produce more complex ionizing spectra between 1-5 Ryd that are critical to interpreting ions of Si and C. We also make a preliminary investigation of the effects of He II ionization front nonoverlap. Because the attenuation and reemission by intervening clouds enhance Si IV relative to C the observed high Si IV/C IV ratios do not require an unrealistic Si overproduction (Si/C greater than or equal to 3 (Si/C)(solar mass)). If the ionizing spectrum is dominated by 'local effects' from massive stars, even larger Si IV/C IV ratios are possible. However, unless stellar radiation dominates quasars by more than a factor of 10, we confirm the evidence for some Si overproduction by massive stars; values Si/C approx. 2(Si/C)(solar mass) fit the measurements better than solar abundances. Ultimately, an adequate interpretation of the ratios of C IV, Si IV, and C II may require hot, collisionally ionized gas in a multiphase medium.

  16. The ultraviolet spectra of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Keel, William C.; Windhorst, Rogier A.

    1991-01-01

    New and archival IUE SWP spectra are reported for nine nearby radio galaxies (V is less than 15 mag), together with optical emissionlike data for these galaxies as well as a number of candidates with weaker line emission. Both their UV line and continuum properties, as well as their UV and UV-optical line ratios, are examined. Ly-alpha emission is found to be common among local radio galaxies, at modest luminosities (typically 10 exp 41-42 erg/s). No apparent relation is found between L(Ly-alpha) and radio power for the nearby radio galaxies alone. The Ly-alpha/H-alpha ratio in low power nearby radio galaxies is 2-5 times lower than the prediction for case B recombination. The destruction of Ly-alpha photons by grains during resonant scattering can explain the observed deficiency for reasonable metallicities. The nearby radio galaxies have in general a small C IV/Ly-alpha ratio (less than 0.1). Comparison of the C IV and Ly-alpha strengths with those in luminous AGN suggests that most of the UV continuum comes from the stellar population, and not from the AGN.

  17. LARGE-SCALE FLUCTUATIONS IN THE He II Ly{alpha} FOREST AND He II REIONIZATION

    SciTech Connect

    Furlanetto, Steven R.; Dixon, Keri L.

    2010-05-01

    We examine large-scale fluctuations in the He II Ly{alpha} forest transmission during and after He II reionization. We use a simple Monte Carlo model to distribute quasars throughout a large volume and compute the resulting radiation field along one-dimensional skewers. In agreement with previous studies, we find that the rarity of these sources induces order unity fluctuations in the mean optical depth after reionization, even when averaged over large segments ({approx}10-100Mpc across). We compare our models to existing data along five He II Ly{alpha} forest lines of sight spanning z {approx} 2-3.2. The large cosmic variance contained in our model plausibly explains many of the observed fluctuations at z {approx_lt} 2.5. But our models cannot accommodate the large fluctuations toward high optical depths on {approx}30Mpc scales observed at z {approx} 2.7-2.9, and the measured optical depths ({tau}{sub eff} {approx_gt} 4) at z>2.9 are difficult to explain with a smoothly evolving mean radiation field. In order to better understand these data, we construct a toy model of He II reionization, in which we assume that regions with the smallest radiation fields in a post-reionization universe (or farthest from strong ionizing sources) are completely dark during reionization. The observed fluctuations fit much more comfortably into this model, and we therefore argue that, according to present data, He II reionization does not complete until z {approx_lt} 2.9.

  18. DEEP LBT/LUCI SPECTROSCOPY OF AN Ly{alpha} EMITTER CANDIDATE AT z {approx_equal} 7.7

    SciTech Connect

    Jiang Linhua; Bian Fuyan; Fan Xiaohui; McGreer, Ian D.; Stark, Daniel P.; Clement, Benjamin; Egami, Eiichi; Krug, Hannah B.

    2013-07-01

    We present deep spectroscopic observations of an Ly{alpha} emitter (LAE) candidate at z {approx_equal} 7.7 using the infrared spectrograph LUCI on the 2 Multiplication-Sign 8.4 m Large Binocular Telescope (LBT). The candidate is the brightest among the four z {approx_equal} 7.7 LAE candidates found in a narrowband imaging survey by Krug et al. Our spectroscopic data include a total of 7.5 hr of integration with LBT/LUCI and are deep enough to significantly (3.2{sigma}-4.9{sigma}) detect the Ly{alpha} emission line of this candidate based on its Ly{alpha} flux 1.2 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} estimated from the narrowband photometry. However, we do not find any convincing signal at the expected position of its Ly{alpha} emission line, suggesting that this source is not an LAE at z {approx_equal} 7.7. The non-detection in this work, together with the previous studies of z {approx_equal} 7.7 LAEs, puts a strong constraint on the bright-end Ly{alpha} luminosity function (LF) at z {approx_equal} 7.7. We find a rapid evolution of the Ly{alpha} LF from z {approx_equal} 6.5 to 7.7: the upper limit of the z {approx_equal} 7.7 LF is more than five times lower than the z {approx_equal} 6.5 LF at the bright end (f{>=} 1.0 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} or L{>=} 6.9 Multiplication-Sign 10{sup 42} erg s{sup -1}). This is likely caused by an increasing neutral fraction in the intergalactic medium that substantially attenuates Ly{alpha} emission at z {approx_equal} 7.7.

  19. THE HETDEX PILOT SURVEY. I. SURVEY DESIGN, PERFORMANCE, AND CATALOG OF EMISSION-LINE GALAXIES

    SciTech Connect

    Adams, Joshua J.; Blanc, Guillermo A.; Gebhardt, Karl; Hao, Lei; Byun, Joyce; Fry, Alex; Jeong, Donghui; Komatsu, Eiichiro; Hill, Gary J.; Cornell, Mark E.; MacQueen, Phillip J.; Drory, Niv; Bender, Ralf; Hopp, Ulrich; Kelzenberg, Ralf; Ciardullo, Robin; Gronwall, Caryl; Finkelstein, Steven L.; Gawiser, Eric; Kelz, Andreas

    2011-01-15

    We present a catalog of emission-line galaxies selected solely by their emission-line fluxes using a wide-field integral field spectrograph. This work is partially motivated as a pilot survey for the upcoming Hobby-Eberly Telescope Dark Energy Experiment. We describe the observations, reductions, detections, redshift classifications, line fluxes, and counterpart information for 397 emission-line galaxies detected over 169 {open_square}' with a 3500-5800 A bandpass under 5 A full-width-half-maximum (FWHM) spectral resolution. The survey's best sensitivity for unresolved objects under photometric conditions is between 4 and 20x 10{sup -17} erg s{sup -1} cm{sup -2} depending on the wavelength, and Ly{alpha} luminosities between 3 x 10{sup 42} and 6 x 10{sup 42} erg s{sup -1} are detectable. This survey method complements narrowband and color-selection techniques in the search of high-redshift galaxies with its different selection properties and large volume probed. The four survey fields within the COSMOS, GOODS-N, MUNICS, and XMM-LSS areas are rich with existing, complementary data. We find 105 galaxies via their high-redshift Ly{alpha} emission at 1.9 < z < 3.8, and the majority of the remainder objects are low-redshift [O II]3727 emitters at z < 0.56. The classification between low- and high-redshift objects depends on rest-frame equivalent width (EW), as well as other indicators, where available. Based on matches to X-ray catalogs, the active galactic nuclei fraction among the Ly{alpha} emitters is 6%. We also analyze the survey's completeness and contamination properties through simulations. We find five high-z, highly significant, resolved objects with FWHM sizes >44 {open_square}' which appear to be extended Ly{alpha} nebulae. We also find three high-z objects with rest-frame Ly{alpha} EW above the level believed to be achievable with normal star formation, EW{sub 0}>240 A. Future papers will investigate the physical properties of this sample.

  20. COS-GTO: QSO Absorbers, Galaxies and Large-scale Structures in the Local Universe.

    NASA Astrophysics Data System (ADS)

    Green, James

    2009-07-01

    This is a program to probe the large scale structure of baryons in the universe, including addressing questions of baryon fraction, physical conditions and relationships between absorbers and large-scale structures of galaxies. Besides these specific goals, this proposed GTO program also probes a large enough total path length in Ly alpha and OVI to add significantly to what STIS/FUSE has already observed. Several Galactic High Velocity Cloud Complexes also are probed by these sightlines, particularly the M Complex. The total path length of this proposed program for Ly alpha large-scale structure surveys is delta_z 5.5. We have selected a variety of targets to address these questions, under the following subcategories:1. Target 8 bright BL Lac objects to search for low contrast Ly alpha absorbers from the warm-hot interstellar medium {WHIM}. Science drivers: What are physical conditions and extent of warm-hot IGM in the current epoch? Can we discover metal-poor WHIM using very broad Ly alpha lines? What is the number density of such lines {dN/dz} and what is their relationship if any with tentative Chandra detections of even hotter gas?2. Ly alpha cloud sizes: The targets are a bright AGN pair which yield tangential distance separations of 100-500 kpc at z=0.01-0.05, where galaxy surveys are excellent. This pair has two filaments and two voids in this distance range. Science drivers: What are the characteristic sizes of Ly alpha absorbers, weak metal-line absorbers and absorbers in voids? Better size determinations will tighten current estimates of the baryon content of the photoionzed IGM .3. Probes of starburst outflows: The targets are bright AGN, <= 100 kpc in projection out of the minor axis of nearby starburst galaxies. Science drivers: Outflowing, unbound winds have been implicated as a primary mechanism to enrich the IGM in mass, metals and energy. But do starburst winds from massive galaxies escape the galaxy's gravitational potential? If so, what is the

  1. PHOTODESORPTION OF SOLID CO{sub 2} BY LY{alpha}

    SciTech Connect

    Bahr, D. A.; Baragiola, R. A.

    2012-12-10

    We measured desorption of atoms and molecules from films of solid carbon dioxide in an ultrahigh vacuum from 6 to 60 K under irradiation with Ly{alpha} (121.6 nm, 10.2 eV) photons, an important process in the balance between gas phase and condensed molecules in the interstellar medium. The measurements use microgravimetry and mass spectrometry during irradiation and temperature programmed desorption after irradiation. At low photon fluences, the desorption flux consists mainly of O atoms and, after {approx}10{sup 17} photons cm{sup -2}, it is dominated by CO with smaller amount of O{sub 2}, C, and CO{sub 2}, with the presence of O{sub 2} indicating solid-state chemical reactions. At high fluences (up to 10{sup 18} photons cm{sup -2}){sub ,} the desorption yields saturate at values much higher than in previous studies. The yields (molecules/photon), derived assuming stoichiometric desorption, reach 0.014 at 6 K, growing to {approx}0.2 at 50 and 60 K. Warming the films during irradiation gives rise to pressure spikes that suggest desorption of trapped species in pores or at defects, possibly assisted by radical-induced reactions. Such an effect could be significant for radiation-processed CO{sub 2}-coated interstellar grains that are heated by, i.e., cosmic ray impacts or grain-grain collisions. We discuss the experiments considering photochemical mechanisms and compare them to the results of ion irradiation.

  2. Copernicus observations of Ly-alpha and Mg II emission from HR 1099 /V711 Tauri/ and UX Ari

    NASA Technical Reports Server (NTRS)

    Weiler, E. J.

    1978-01-01

    Ultraviolet observations of two RS CVn binaries obtained with Copernicus are described. High-resolution (0.05 A) U1 observations indicate that both HR 1099 and UX Ari display broad Ly-alpha emission. The Ly-alpha emission strength from HR 1099 is variable and seems to be correlated with orbital phase, while the UX Ari results indicate no significant variation. Moderate resolution (0.51 A) V2 scans of both systems show variable Mg II h and k emission-line profiles which usually matched the velocity of the more active star in each binary. Additionally, displaced emission components were seen at velocities of up to + or - 250 km/s, indicative of high-velocity gas motions. The radial velocities of these emission features from HR 1099 are marginally correlated with orbital phase. Highly active and variable chromospheric phenomena are found to be the most consistent explanation of these results.

  3. SEARCH FOR z {approx} 7 Ly{alpha} EMITTERS WITH THE SUPRIME-CAM AT THE SUBARU TELESCOPE

    SciTech Connect

    Hibon, P.; Kashikawa, N.; Iye, M.; Shibuya, T.; Willott, C.

    2012-01-10

    We report a search for z = 7 Ly{alpha} emitters (LAEs) using a custom-made narrowband filter centered at 9755 A with the Suprime-Cam instrument installed at the Subaru telescope. We observed two different fields and obtained two samples of seven LAEs, of which four are robust in each field. We cover the luminosity range of 9.10{sup 42}-2.10{sup 43} erg s{sup -1} in comoving volumes of {approx}4 Multiplication-Sign 10{sup 5} and 4.3 Multiplication-Sign 10{sup 5} Mpc{sup 3}. From this result, we derived possible z {approx} 7 Ly{alpha} luminosity functions for the full samples and for a subsample of four objects in each field. We do not observe, in each case, any strong evolution between the z = 6.5 and z {approx} 7 Ly{alpha} luminosity functions. Spectroscopic confirmation for these candidate samples is required to establish a definitive measure of the luminosity function at z {approx} 7.

  4. Ly-alpha and white light observations of a CME during the Spartan 201-1 mission

    NASA Technical Reports Server (NTRS)

    Hassler, Don M.; Strachan, Leonard; Gardner, L. D.; Kohl, J. L.; Guhathakurta, Madhulika; Fisher, Richard R.; Strong, K.

    1994-01-01

    A coronal mass ejection (CME) near a large active region on the west limb was observed with the white light coronograph (WLC) and ultraviolet coronal spectrometer (UVCS) on the Spartan 201 satellite at 9:42 UT on 12 Apr. 1993. Soft X-ray images of the region below the CME were obtained out to 1.7 solar radii with the soft X-ray telescope (SXT) on Yohkoh. After the event, the formation of a new helmet streamer could be seen in the polarized brightness (pB) images from the Mk III coronograph at Mauna Loa. The CME was observed from Spartan 201 in two different pB images obtained 14 min apart using the WLC, and was observed moving through the field-of-view of the UVCS integrated intensity slit. Ly-alpha intensities in the same region of the corona were obtained one orbit earlier (prior to the CME) using the Ly-alpha profile slit of the UVCS. These are the first Ly-alpha observations of a CME and may help constrain models of the electron temperature on CME's.

  5. A MEASUREMENT OF SMALL-SCALE STRUCTURE IN THE 2.2 {<=} z {<=} 4.2 Ly{alpha} FOREST

    SciTech Connect

    Lidz, Adam; Faucher-Giguere, Claude-Andre; McQuinn, Matthew; Zaldarriaga, Matias; Hernquist, Lars; Dutta, Suvendra; Dall'Aglio, Aldo; Fechner, Cora

    2010-07-20

    The amplitude of fluctuations in the Ly{alpha} forest on small spatial scales is sensitive to the temperature of the intergalactic medium (IGM) and its spatial fluctuations. The temperature of the IGM and its spatial variations contain important information about hydrogen and helium reionization. We present a new measurement of the small-scale structure in the Ly{alpha} forest from 40 high resolution, high signal-to-noise ratio, VLT spectra for absorbing gas at redshifts between 2.2 {<=} z {<=} 4.2. We convolve each Ly{alpha} forest spectrum with a suitably chosen Morlet wavelet filter, which allows us to extract the amount of small-scale structure in the forest as a function of position across each spectrum. We monitor contamination from metal line absorbers. We present a first comparison of these measurements with high-resolution hydrodynamic simulations of the Ly{alpha} forest that track more than 2 billion particles. This comparison suggests that the IGM temperature close to the cosmic mean density (T {sub 0}) peaks at a redshift near z = 3.4, at which point it is greater than 20, 000 K at {approx}>2{sigma} confidence. The temperature at lower redshift is consistent with the fall-off expected from adiabatic cooling (T {sub 0} {proportional_to} (1 + z){sup 2}), after the peak temperature is reached near z = 3.4. In our highest redshift bin, centered around z = 4.2, the results favor a temperature of T {sub 0} = 15-20, 000 K. However, owing mostly to uncertainties in the mean transmitted flux at this redshift, a cooler IGM model with T {sub 0} = 10, 000 K is only disfavored at the 2{sigma} level here, although such cool IGM models are strongly discrepant with the z {approx} 3-3.4 measurement. We do not detect large spatial fluctuations in the IGM temperature at any redshift covered by our data set. The simplest interpretation of our measurements is that He II reionization completes sometime near z {approx} 3.4, although statistical uncertainties are still large

  6. PHOTOMETRIC PROPERTIES OF Ly{alpha} EMITTERS AT z {approx} 4.86 IN THE COSMOS 2 SQUARE DEGREE FIELD

    SciTech Connect

    Shioya, Y.; Taniguchi, Y.; Nagao, T.; Saito, T.; Trump, J.; Sasaki, S. S.; Ideue, Y.; Nakajima, A.; Matsuoka, K.; Murayama, T.; Scoville, N. Z.; Capak, P.; Ellis, R. S.; Sanders, D. B.; Kartaltepe, J.; Mobasher, B.; Aussel, H.; Koekemoer, A.; Carilli, C.; Garilli, B.

    2009-05-01

    We present results of a survey for Ly{alpha} emitters at z {approx} 4.86 based on optical narrowband ({lambda} {sub c} = 7126 A, {delta}{lambda} = 73 A) and broadband (B, V, r', i', and z') observations of the Cosmic Evolution Survey field using Suprime-Cam on the Subaru Telescope. We find 79 Ly{alpha} emitter (LAE) candidates at z {approx} 4.86 over a contiguous survey area of 1.83 deg{sup 2}, down to the Ly{alpha} line flux of 1.47 x 10{sup -17} erg s{sup -1} cm{sup -2}. We obtain the Ly{alpha} luminosity function with a best-fit Schechter parameters of log L* = 42.9{sup +0.5} {sub -0.3} erg s{sup -1} and {phi}* = 1.2{sup +8.0} {sub -1.1} x 10{sup -4} Mpc{sup -3} for {alpha} = -1.5 (fixed). The two-point correlation function for our LAE sample is {xi}(r) = (r/4.4{sup +5.7} {sub -2.9} Mpc){sup -1.90{+-}}{sup 0.22}. In order to investigate the field-to-field variations of the properties of Ly{alpha} emitters, we divide the survey area into nine tiles of 0.{sup 0}5 x 0.{sup 0}5 each. We find that the number density varies with a factor of {approx_equal}2 from field to field with high statistical significance. However, we find no significant field-to-field variance when we divide the field into four tiles with 0.{sup 0}7 x 0.{sup 0}7 each. We conclude that at least 0.5 deg{sup 2} survey area is required to derive averaged properties of LAEs at z {approx} 5, and our survey field is wide enough to overcome the cosmic variance.

  7. THE ANGULAR DISTRIBUTION OF Ly{alpha} RESONANT PHOTONS EMERGING FROM AN OPTICALLY THICK MEDIUM

    SciTech Connect

    Yang Yang; Shu Chiwang; Roy, Ishani; Fang Lizhi

    2013-07-20

    We investigate the angular distribution of Ly{alpha} photons scattering or emerging from an optically thick medium. Since the evolution of specific intensity I in frequency space and angular space are coupled with each other, we first develop the WENO numerical solver to find the time-dependent solutions of the integro-differential equation of I in frequency and angular space simultaneously. We first show that the solutions with the Eddington approximation, which assume that I is linearly dependent on the angular variable {mu}, yield similar frequency profiles of the photon flux as those without the Eddington approximation. However, the solutions of the {mu} distribution evolution are significantly different from those given by the Eddington approximation. First, the angular distribution of I is found to be substantially dependent on the frequency of the photons. For photons with the resonant frequency {nu}{sub 0}, I contains only a linear term of {mu}. For photons with frequencies at the double peaks of the flux, the {mu}-distribution is highly anisotropic; most photons are emitted radially forward. Moreover, either at {nu}{sub 0} or at the double peaks, the {mu} distributions actually are independent of the initial {mu} distribution of photons of the source. This is because the photons with frequencies either at {nu}{sub 0} or the double peaks undergo the process of forgetting their initial conditions due to resonant scattering. We also show that the optically thick medium is a collimator of photons at the double peaks. Photons from the double peaks form a forward beam with a very small opening angle.

  8. SPECTROSCOPIC CONFIRMATION OF z {approx} 7 LYMAN BREAK GALAXIES: PROBING THE EARLIEST GALAXIES AND THE EPOCH OF REIONIZATION

    SciTech Connect

    Pentericci, L.; Fontana, A.; Castellano, M.; Grazian, A.; Boutsia, K.; Giallongo, E.; Maiolino, R.; Paris, D.; Santini, P.; Vanzella, E.; Cristiani, S.; Dijkstra, M.; Dickinson, M.; Giavalisco, M.; Moorwood, A.

    2011-12-20

    We present the final results from our ultra-deep spectroscopic campaign with FORS2 at the ESO Very Large Telescope (VLT) for the confirmation of z {approx_equal} 7 'z-band dropout' candidates selected from our VLT/Hawk-I imaging survey over three independent fields. In particular, we report on two newly discovered galaxies at redshift {approx}6.7 in the New Technology Telescope Deep Field. Both galaxies show an Ly{alpha} emission line with rest-frame equivalent widths (EWs) of the order of 15-20 A and luminosities of (2-4) Multiplication-Sign 10{sup 42} erg s{sup -1}. We also present the results of ultra-deep observations of a sample of i-dropout galaxies, from which we set a solid upper limit on the fraction of interlopers. Out of the 20 z-dropouts observed we confirm 5 galaxies at 6.6 < z < 7.1. This is systematically below the expectations drawn on the basis of lower redshift observations: in particular, there is a significant lack of objects with intermediate Ly{alpha} EWs (between 20 and 55 A). We conclude that the observed trend for the rising fraction of Ly{alpha} emission in Lyman break galaxies from z {approx} 3 to z {approx} 6 is most probably reversed from z {approx} 6 to z {approx} 7. Explaining the observed rapid change in the Ly{alpha} emitter fraction among the dropout population with reionization requires a fast evolution of the neutral fraction of hydrogen in the universe. Assuming that the universe is completely ionized at z = 6 and adopting a set of semi-analytical models, we find that our data require a change of the neutral hydrogen fraction of the order of {Delta}{chi}{sub H{sub i}}{approx}0.6 in a time {Delta}z {approx} 1, provided that the escape fraction does not increase dramatically over the same redshift interval.

  9. HI Selected Galaxies in SDSS

    NASA Astrophysics Data System (ADS)

    West, A. A.; Dalcanton, J. J.; Garcia-Appadoo, D. A.; Disney, M. J.; SDSS Collaboration

    2004-05-01

    We present an analysis of the properties of HI selected galaxies that fall within both the HI Parkes All Sky Survey (HIPASS) and the Sloan Digital Sky Survey (SDSS). By comparing optical properties derived from SDSS with the HI properties from HIPASS, we are able to observe relationships between the cool gas and the stellar populations. We investigate how various physical parameters such as color, morphology, gas fraction, baryonic mass, dynamical mass, and surface brightness correlate with each other. This provides an important sample that can be used to study the factors that play a role in star formation efficiency. This study also allows us to compare the differences between HI and optically selected samples.

  10. KECK SPECTROSCOPY OF FAINT 3 < z < 7 LYMAN BREAK GALAXIES. III. THE MEAN ULTRAVIOLET SPECTRUM AT z {approx_equal} 4

    SciTech Connect

    Jones, Tucker; Ellis, Richard S.; Stark, Daniel P.

    2012-05-20

    We present and discuss the mean rest-frame ultraviolet spectrum for a sample of 81 Lyman break galaxies (LBGs) selected to be B-band dropouts at z {approx_equal} 4. The sample is mostly drawn from our ongoing Keck/DEIMOS survey in the GOODS fields and augmented with archival Very Large Telescope data. In general, we find similar spectroscopic trends to those found in earlier surveys of LBGs at z = 3. Specifically, low-ionization absorption lines which trace neutral outflowing gas are weaker in galaxies with stronger Ly{alpha} emission, bluer UV spectral slopes, lower stellar masses, lower UV luminosities, and smaller half-light radii. This is consistent with a physical picture whereby star formation drives outflows of neutral gas which scatter Ly{alpha} and produce strong low-ionization absorption lines, while increasing galaxy stellar mass, size, metallicity, and dust content. Typical galaxies are thus expected to have stronger Ly{alpha} emission and weaker low-ionization absorption at earlier times, and we indeed find somewhat weaker low-ionization absorption at higher redshifts. In conjunction with earlier results from our survey, we argue that the reduced low-ionization absorption is likely caused by lower covering fraction and/or velocity range of outflowing neutral gas at earlier epochs. Although low-ionization absorption decreases at higher redshift, fine-structure emission lines are stronger, suggesting a greater concentration of neutral gas at small galactocentric radius ({approx}< 5 kpc). Our continuing survey will enable us to extend these diagnostics more reliably to higher redshift and determine the implications for the escape fraction of ionizing photons which governs the role of early galaxies in cosmic reionization.

  11. A SUPER-DAMPED Ly{alpha} QUASI-STELLAR OBJECT ABSORBER AT z = 2.2

    SciTech Connect

    Kulkarni, Varsha P.; Som, Debopam; Meiring, Joseph; Peroux, Celine; York, Donald G.; Khare, Pushpa; Lauroesch, James T.

    2012-04-20

    We report the discovery of a 'super-damped' Ly{alpha} absorber at z{sub abs} = 2.2068 toward quasi-stellar object (QSO) Q1135-0010 in the Sloan Digital Sky Survey (SDSS) and follow-up Very Large Telescope (VLT) UVES spectroscopy. A Voigt profile fit to the damped Ly{alpha} (DLA) line indicates log N{sub Hi}= 22.05 {+-} 0.1. This is the second QSO DLA discovered to date with such high N{sub Hi}. We derive element abundances [Si/H] = -1.10 {+-} 0.10, [Zn/H] = -1.06 {+-} 0.10, [Cr/H] = -1.55 {+-} 0.10, [Ni/H] = -1.60 {+-} 0.10, [Fe/H] = -1.76 {+-} 0.10, [Ti/H] = -1.69 {+-} 0.11, [P/H] = -0.93 {+-} 0.23, and [Cu/H] = -0.75 {+-} 0.14. Our data indicate detection of Ly{alpha} emission in the DLA trough, implying a star formation rate (SFR) of {approx}10 M{sub Sun} yr{sup -1} in the absence of dust attenuation. C II* {lambda}1336 absorption is also detected, suggesting SFR surface density -2

  12. THE HANLE EFFECT OF THE HYDROGEN Ly{alpha} LINE FOR PROBING THE MAGNETISM OF THE SOLAR TRANSITION REGION

    SciTech Connect

    Trujillo Bueno, Javier; Stepan, JirI; Casini, Roberto E-mail: stepan@iac.es

    2011-09-01

    We present some theoretical predictions concerning the amplitude and magnetic sensitivity of the linear-polarization signals produced by scattering processes in the hydrogen Ly{alpha} line of the solar transition region. To this end, we have calculated the atomic-level polarization (population imbalances and quantum coherences) induced by anisotropic radiation pumping in semiempirical and hydrodynamical models of the solar atmosphere, taking into account radiative transfer and the Hanle effect caused by the presence of organized and random magnetic fields. The line-center amplitudes of the emergent linear-polarization signals are found to vary typically between 0.1% and 1%, depending on the scattering geometry and the strength and orientation of the magnetic field. The results shown here encourage the development of UV polarimeters for sounding rockets and space telescopes with the aim of opening up a diagnostic window for magnetic field measurements in the upper chromosphere and transition region of the Sun.

  13. The Local LY alpha Forest: Association of Clouds with Superclusters and Voids

    NASA Astrophysics Data System (ADS)

    Stocke, John T.; Shull, J. Michael; Penton, Steve; Donahue, Megan; Carilli, Chris

    1995-09-01

    The Goddard High Resolution Spectrograph aboard the Hubble Space Telescope was used with the G160M grating to obtain high-resolution (0.2 Å) spectra of three very bright active galactic nuclei located behind voids in the nearby distribution of bright galaxies (i.e., CfA and Arecibo redshift survey regions). A total of eight definite (≥ 4 σ) Lyα absorption lines were discovered ranging in equivalent width from 26 to 240 mÅ at Galactocentric velocities 1740-7740 km 5-1 Of these eight systems, we locate seven in supercluster structures and one, in the sight line of Mrk 501 at 7740 km s-1, in a void. In addition, one of two tentative (3-4 σ) Lyα absorption lines are found in voids. Thus, the voids are not entirely devoid of matter, and not all Lyα clouds are associated with galaxies. Also, since the path lengths through voids and superclusters probed by our observations thus far are nearly equal, there is some statistical evidence that the Lyα clouds avoid the voids. The nearest galaxy neighbors to these absorbing clouds are 0.45-5.9 Mpc away, too far to be physically associated by most models. The lower equivalent width absorption lines (Wλ ≤ 100 mÅ) are consistent with random locations with respect to galaxies and may be truly intergalactic, similar to the bulk of the Lyα forest seen at high z. These results on local Lyα clouds are in full agreement with those found by Morris et al. (1993) for the 3C 273 sight line but are different from the results for higher equivalent width systems where closer cloud-galaxy associations were found by Lanzetta et al. (1994). Pencil-beam optical and 21 cm radio line observations of the area of sky surrounding Mrk 501 fail to find faint galaxies near the velocities of the Lyα clouds in that sight line. Specifically, for the "void absorption" system at 7740 km s-1, we find no galaxy at comparable redshift to the absorber within 100 h-175 kpc (H0 = 75 h75 km s-1 Mpc-1) with an absolute magnitude of B ≤ -16 and no

  14. THE Ly{alpha} LINES OF H I AND He II: A DIFFERENTIAL HANLE EFFECT FOR EXPLORING THE MAGNETISM OF THE SOLAR TRANSITION REGION

    SciTech Connect

    Trujillo Bueno, Javier; Stepan, Jiri; Belluzzi, Luca E-mail: stepan@iac.es

    2012-02-10

    The Ly{alpha} line of He II at 304 Angstrom-Sign is one of the spectral lines of choice for EUV channels of narrowband imagers on board space telescopes, which provide spectacular intensity images of the outer solar atmosphere. Since the magnetic field information is encoded in the polarization of the spectral line radiation, it is important to investigate whether the He II line radiation from the solar disk can be polarized, along with its magnetic sensitivity. Here we report some theoretical predictions concerning the linear polarization signals produced by scattering processes in this strong emission line of the solar transition region, taking into account radiative transfer and the Hanle effect caused by the presence of organized and random magnetic fields. We find that the fractional polarization amplitudes are significant ({approx}1%), even when considering the wavelength-integrated signals. Interestingly, the scattering polarization of the Ly{alpha} line of He II starts to be sensitive to the Hanle effect for magnetic strengths B {approx}> 100 G (i.e., for magnetic strengths of the order of and larger than the Hanle saturation field of the hydrogen Ly{alpha} line at 1216 Angstrom-Sign ). We therefore propose simultaneous observations of the scattering polarization in both Ly{alpha} lines to facilitate magnetic field measurements in the upper solar chromosphere. Even the development of a narrowband imaging polarimeter for the He II 304 Angstrom-Sign line alone would be already of great diagnostic value for probing the solar transition region.

  15. Lyman Alpha Emitting Galaxies at 2 < z < 3: Towards a Calibrated Probe of Dark Energy

    SciTech Connect

    Caryl Gronwall

    2012-12-03

    The goal of this project was to establish the physical properties of Ly{alpha} emitting galaxies from redshifts of 2 to 3 in order to better calibrate the use of LAEs as probes of the large scale structure of the universe for upcoming dark energy experiments, such as the Hobby Eberly Telescope Dark Energy Experiment (HETDEX). We have obtained narrow-band imaging of the Extended Chandra Deep Field South (ECDF-S) in two different narrow-band filters centered at Ly{alpha} at z=2.1 and 3.1. The resulting of samples of LAEs were used to determine the LAE luminosity function, equivalent width distribution and clustering properties (bias) of LAEs at these redshifts. While the results from the ECDF-S appear robust, they are based on a single field. To explore the effects of cosmic variance and galaxy environment on the physical properties of LAEs, we have also obtained narrow-band data at both redshifts (z = 2:1 and 3:1) in three additional fields (SDSS 1030+-05, the Extended Hubble Deep Field South, and CW 1255+01). The narrow-band imaging data has been reduced and LAE catalogs are being generated. We have calculated preliminary luminosity functions, equivalent width distributions, and clustering properties. We have also obtained follow-up spectroscopy in the optical (using VLT/FORS) and in the near-infrared (using Magellan/MMIRS). Since individual LAEs have too little S/N to enable meaningful fits for stellar population parameters, our previous work has analyzed stacked Spectral Energy Distributions (SEDs). SED fitting was performed on several subsets of LAEs selected by their rest-UV luminosity, UV spectral slope, Ly alpha luminosity, Equivalent Width, or rest-optical (IRAC) luminosity.

  16. Metal Abundances and Physical Conditions in Two Damped LY alpha Systems toward HS 1946+7658

    NASA Astrophysics Data System (ADS)

    Lu, Limin; Savage, Blair D.; Tripp, Todd M.; Meyer, David M.

    1995-07-01

    Quasar metal absorption systems represent some of the best opportunities to study the properties and evolution of galaxies at high red shifts. We present a study of metal abundances and physical conditions in two damped Lyα systems at z = 2.8443 and z = 1.7382 toward the quasar HS 1946 + 7658. The analyses are based on a high-resolution (FWHM = 20 km s-1), high signal-to-noise ratio (40-80 per resolution element) spectrum of the quasar. Ion column densities are determined from a combination of profile fitting and the apparent optical depth method. Special efforts are exercised to minimize the effects of the line saturation problem. We also incorporate recently improved oscillator strengths for a number of important transitions. The z = 2.8443 system is found to have an absolute Fe metallicity of 2.4-2.6 dex below solar, where the large range mainly reflects uncertainties in the ionization corrections. The absolute metallicity of the z = 1.7382 system cannot be determined because its H I column density is unknown. We find an apparent overabundance of Si to Fe relative to their solar ratio by about a factor of 2 in both systems. We also find an overabundance of Si to Al relative to solar by a factor of 3 in the z = 2.8443 system, and an underabundance of Mn to Fe relative to solar by a factor of 3 in the z = 1.7382 system. Photoionization calculations suggest that these abundance ratios are not likely to be significantly biased by ionization effects. More likely, either these ratios represent the intrinsic abundance ratios in the gas, or the gas actually has solar relative abundances with the observed abundance patterns being produced by dust depletion effects. However, the apparent underabundance of Mn to Fe relative to solar argues against the latter interpretation. Interestingly, the observed relative abundance patterns are similar to those seen in Galactic low-metallicity stars, and they can be explained by theories of heavy-element nucleosynthesis in the early

  17. A SEARCH FOR C II 158 {mu}m LINE EMISSION IN HCM 6A, A Ly{alpha} EMITTER AT z = 6.56

    SciTech Connect

    Kanekar, Nissim; Wagg, Jeff; Chary, Ranga Ram; Carilli, Christopher L.

    2013-07-10

    We report a Plateau de Bure Interferometer search for C II 158 {mu}m emission from HCM 6A, a lensed Ly{alpha} emitter (LAE) at z = 6.56. Our non-detections of C II 158 {mu}m line emission and 1.2 mm radio continuum emission yield 3{sigma} limits of L{sub CII} < 6.4 x 10{sup 7} x ({Delta}V/100 km s{sup -1}){sup 1/2} L{sub Sun} for the C II 158 {mu}m line luminosity and S{sub 1.2mm} < 0.68 mJy for the 1.2 mm flux density. The local conversion factor between L{sub CII} and the star formation rate (SFR) yields an SFR < 4.7 M{sub Sun} yr{sup -1}, Almost-Equal-To 2 times lower than that inferred from the ultraviolet (UV) continuum, suggesting that the local factor may not be applicable in high-z LAEs. The non-detection of 1.2 mm continuum emission yields a total SFR < 28 M{sub Sun} yr{sup -1}; any obscured star formation is thus within a factor of two of the visible star formation. Our best-fit model to the rest-frame UV/optical spectral energy distribution of HCM 6A yields a stellar mass of 1.3 Multiplication-Sign 10{sup 9} M{sub Sun} and an SFR of Almost-Equal-To 10 M{sub Sun} yr{sup -1}, with negligible dust obscuration. We fortuitously detect CO J = 3-2 emission from a z = 0.375 galaxy in the foreground cluster A370, and obtain a CO line luminosity of L'(CO) > (8.95 {+-} 0.79) Multiplication-Sign 10{sup 8} K km s{sup -1} pc{sup 2} and a molecular gas mass of M(H{sub 2}) > (4.12 {+-} 0.36) Multiplication-Sign 10{sup 9} M{sub Sun }, for a CO-to-H{sub 2} conversion factor of 4.6 M{sub Sun} (K km s{sup -1} pc{sup 2}){sup -1}.

  18. METALLICITIES, DUST, AND MOLECULAR CONTENT OF A QSO-DAMPED Ly{alpha} SYSTEM REACHING log N(H I) = 22: AN ANALOG TO GRB-DLAs

    SciTech Connect

    Guimaraes, R.; Noterdaeme, P.; Petitjean, P.; Ledoux, C.; Srianand, R.; Rahmani, H.; Lopez, S.

    2012-06-15

    We present the elemental abundance and H{sub 2} content measurements of a damped Ly{alpha} (DLA) system with an extremely large H I column density, log N(H I) (cm{sup -2}) = 22.0 {+-} 0.10, at z{sub abs} = 3.287 toward the QSO SDSS J081634+144612. We measure column densities of H{sub 2}, C I, C I*, Zn II, Fe II, Cr II, Ni II, and Si II from a high signal-to-noise and high spectral resolution VLT-UVES spectrum. The overall metallicity of the system is [Zn/H] = -1.10 {+-} 0.10 relative to solar. Two molecular hydrogen absorption components are seen at z = 3.28667 and 3.28742 (a velocity separation of Almost-Equal-To 52 km s{sup -1}) in rotational levels up to J = 3. We derive a total H{sub 2} column density of log N(H{sub 2}) (cm{sup -2}) = 18.66 and a mean molecular fraction of f = 2N(H{sub 2})/[2N(H{sub 2}) + N(H I)] = 10{sup -3.04{+-}0.37}, typical of known H{sub 2}-bearing DLA systems. From the observed abundance ratios we conclude that dust is present in the interstellar medium of this galaxy, with an enhanced abundance in the H{sub 2}-bearing clouds. However, the total amount of dust along the line of sight is not large and does not produce any significant reddening of the background QSO. The physical conditions in the H{sub 2}-bearing clouds are constrained directly from the column densities of H{sub 2} in different rotational levels, C I and C I*. The kinetic temperature is found to be T Almost-Equal-To 75 K and the particle density lies in the range n{sub H} = 50-80 cm{sup -3}. The neutral hydrogen column density of this DLA is similar to the mean H I column density of DLAs observed at the redshift of {gamma}-ray bursts (GRBs). We explore the relationship between GRB-DLAs and the high column density end of QSO-DLAs finding that the properties (metallicity and depletion) of DLAs with log N(H I) > 21.5 in the two populations do not appear to be significantly different.

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

    SciTech Connect

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

    2012-01-10

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

  20. PROBING HIGH-REDSHIFT GALAXY FORMATION AT THE HIGHEST LUMINOSITIES: NEW INSIGHTS FROM DEIMOS SPECTROSCOPY

    SciTech Connect

    Lee, Kyoung-Soo; Dey, Arjun; Cooper, Michael C.; Reddy, Naveen; Jannuzi, Buell T.

    2013-07-01

    We present Keck DEIMOS spectroscopic observations of the most UV-luminous star-forming galaxies at redshifts 3.2 < z < 4.6. Our sample, selected in the Booetes field of the NOAO Deep Wide-Field Survey, contains galaxies with luminosities of L* {approx}< L{sub UV} {approx}< 7 L* and is one of the largest samples to date of the most UV-luminous galaxies at these redshifts. Our spectroscopic data confirm 41 candidates as star-forming galaxies at 3.2 < z < 4.6 and validate the relatively clean selection of the photometric candidates with a contamination rate of 11%-28%. We find that the fraction of Ly{alpha} emitting galaxies increases with decreasing UV luminosity. None of the 12 galaxies with M{sub UV} < -22 (i.e., L{sub UV} > 3 L*) exhibit strong Ly{alpha} emission. We find strong evidence of large-scale outflows, transporting the neutral/ionized gas in the interstellar medium away from the galaxy. Galaxies exhibiting both interstellar absorption and Ly{alpha} emission lines show a significant offset between the two features, with a relative velocity of 200-1150 km s{sup -1}. We find tentative evidence that this measure of the outflow velocity increases with UV luminosity and/or stellar mass. The luminosity- and mass-dependent outflow strengths suggest that the efficiency of feedback and enrichment of the surrounding medium depend on these galaxy parameters. We also stack the individual spectra to construct composite spectra of the absorption-line-only and Ly{alpha}-emitting subsets of the UV luminous galaxies at z {approx_equal} 3.7. The composite spectra are very similar to those of lower-redshift and lower-luminosity Lyman break galaxy (LBG) samples, but with some subtle differences. Analyses of the composite spectra suggest that the UV luminous LBGs at z {approx_equal} 3.7 may have a higher covering fraction of absorbing gas, and may be older (or have had more prolonged star formation histories) than their lower-redshift and lower-luminosity counterparts. In

  1. H Ly-alpha transmittance of thin foils of C, Si/C, and Al/C for keV particle detectors

    NASA Technical Reports Server (NTRS)

    Drake, V. A.; Sandel, B. R.; Jenkins, D. G.; Hsieh, K. C.

    1992-01-01

    A class of instruments designed for remote sensing of space plasmas by measuring energetic neutral atoms (ENA) uses a thin foil as both a signal generator and a light shield. An ENA imager must look directly at the ENA source region, which is also usually an intense source of H Ly-alpha (1216 A) photons. It is desirable to minimize the energy threshold for ENA detectors, at the same time maximizing the blocking of H Ly-alpha. Optimizing filter design to meet these two contrary requirements has led us to measure the transmittance of thin C, Si/C, and Al/C foils at H Ly-alpha. Our results indicate that (1) transmittance of less than 0.0007 can be achieved with 7 micro-g/sq cm Si on 1.7 micro-g/sq cm C; (2) an Si/C composite foil with a thin carbon layer is more effective in blocking UV radiation while having the lowest energy threshold of all the foils measured; and (3) transmittance of Si/C foils of known Si and C thicknesses cannot be accurately predicted, but must be measured.

  2. HST/COS SPECTRA OF DF Tau AND V4046 Sgr: FIRST DETECTION OF MOLECULAR HYDROGEN ABSORPTION AGAINST THE Ly{alpha} EMISSION LINE

    SciTech Connect

    Yang Hao; Linsky, Jeffrey L.; France, Kevin E-mail: jlinsky@jilau1.colorado.edu

    2011-03-20

    We report the first detection of molecular hydrogen (H{sub 2}) absorption in the Ly{alpha} emission line profiles of two classical T Tauri stars (CTTSs), DF Tau and V4046 Sgr, observed by the Hubble Space Telescope/Cosmic Origins Spectrograph. This absorption is the energy source for many of the Lyman-band H{sub 2} fluorescent lines commonly seen in the far-ultraviolet spectra of CTTSs. We find that the absorbed energy in the H{sub 2} pumping transitions from a portion of the Ly{alpha} line significantly differ from the amount of energy in the resulting fluorescent emission. By assuming additional absorption in the H I Ly{alpha} profile along our light of sight, we can correct the H{sub 2} absorption/emission ratios so that they are close to unity. The required H I absorption for DF Tau is at a velocity close to the radial velocity of the star, consistent with H I absorption in the edge-on disk and interstellar medium. For V4046 Sgr, a nearly face-on system, the required absorption is between +100 km s{sup -1} and +290 km s{sup -1}, most likely resulting from H I gas in the accretion columns falling onto the star.

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

    SciTech Connect

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

    2012-06-20

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

  4. HI Selected Galaxies in the SDSS

    NASA Astrophysics Data System (ADS)

    West, Andrew A.; Garcia-Appadoo, Diego A.; Dalcanton, Julianne J.; Disney, Mike J.

    2005-04-01

    We present preliminary results from a study of HI selected galaxies that fall within both the HI Parkes All Sky Survey (HIPASS) and the Sloan Digital Sky Survey (SDSS). By comparing the optical properties derived from the SDSS 5-band photometry with the HI properties from HIPASS, we are able to probe the relationship between the stellar populations and the neutral gas over a range of Hubble types. Our HIPASS/SDSS catalog provides a uniform, homogeneous data set that can be used to investigate the factors that contribute to star formation on global scales. In addition, the construction of this catalog has led to a set of tools to aid in the analysis of large nearby galaxies in the SDSS. We have identified a significant group of low surface brightness (LSB) galaxies, not included in most SDSS studies. A preliminary comparison of the integrated colors of these LSB galaxies with population synthesis models reveals that many of these galaxies are not well described by simple models of star formation. Further work is needed to constrain the star formation histories of these objects.

  5. Low redshift star-forming galaxies: What can they teach us about primeval galaxies?

    NASA Technical Reports Server (NTRS)

    Calzetti, D.; Kinney, A. L.

    1993-01-01

    The analysis of the UV plus optical spectra of three star-forming galaxies, Mrk 496, Mrk 357, TOL1924-416, obtained by matching the size of the optical aperture with that of IUE, has given unexpected results. These can be summarized as follows: (1) the dereddened Ly(alpha)/H(beta) ratios are consistent with the prediction of case B recombination for nebular emission, within the uncertainties; (2) the decrease of the Ly(alpha)/H(beta) ratio with increasing metallicities is not confirmed in our three objects, although the sample is too small to consider this result definitive. The first result is surprising, mainly because at least the two Markarian galaxies have a large enough H1 content to markedly increase the optical depth for the Ly(alpha) photons and to trigger their absorption by dust. This finding can probably be explained as an effect of the inhomogeneous distribution of gas and dust within the galaxies. On the basis of these results, we conclude that the detection of the Ly(alpha) emission line in searching for primeval galaxies (PG's) can be still considered a valid technique.

  6. STIS Observations of the Ly\\Alpha Bright Jet Associated with the Herbig Ae Star HD163296

    NASA Technical Reports Server (NTRS)

    Devine, David; Grady, C. A.; Woodgate, B.; Palunas, P.; Linsky, J. L.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We present follow-up HST/Space Telescope Imaging Spectrograph (STIS) observations of the Ly-alpha bright jet associated with the near-ZAMS Herbig Ae star HD163296. The proper motions and radial velocities of the knots in the flow are consistent with a collimated outflow inclined by 40 deg relative to the plane of the sky with a flow velocity that varies from 350 to 500 km/s along the jet. A new knot is visible in the jet at a projected distance of 0.33 arcsec (40 AU) from the central star. The knot has a dynamical age of only seven months, making it the youngest HH knot ever observed. We did not detect any emission from the counterjet within 2.5 arcsec of the source, which is consistent with absorption due to a uniform 450 AU radius disk tilted at 50 deg relative to the line of sight. We also present observations made with the Goddard Fabry-Perot Imager which show additional, more distant knots along the blue and red shifted outflow lobes, and discuss the collimation of the jet and implications for a magnetosphere associated with HD 163296. Support for this study was provided by HST STIS GTO funding through support to the NOAO, in response to the NASA A/O OSSA-4-84 through the Hubble Space Telescope Project at GSFC, as well as NASA grant NRA-98-03-UVG-O11. NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation. Data analysis facilities were provided by the Laboratory for Astronomy & Solar Physics, NASA/GSFC.

  7. The {ital b} Distribution and the Velocity Structure of Absorption Peaks in the Ly{alpha} Forest

    SciTech Connect

    Hui, L.

    1999-06-01

    A theory is developed that relates the observed {ital b} parameter of a Ly{alpha} absorption line to the velocity curvature of the corresponding peak in the optical depth fluctuation. Its relation to the traditional interpretation of {ital b} as the thermal broadening width is discussed. It is demonstrated that, independent of the details of the cosmological model, the differential {ital b} distribution has a high-{ital b} asymptote of dN/db{proportional_to}b{sup {minus}m}, where m{ge}5, when we make the reasonable assumption that low-curvature fluctuations are statistically favored over high-curvature ones. There in general always exist lines much broader than the thermal width. We develop a linear perturbative analysis of the optical depth fluctuation, which yields a single-parameter prediction for the full {ital b} distribution. In addition to exhibiting the high-velocity tail, it qualitatively explains the observed sharp low-{ital b} cutoff{emdash}a simple reflection of the fact that high-curvature fluctuations are relatively rare. Although the existence of the high-{ital b} asymptote, which is independent of the validity of the linear expansion, is consistent with the observed {ital b} distribution, a detailed comparison of the linear prediction with six observational data sets indicates that higher order corrections are not negligible. The perturbative analysis nonetheless offers valuable insights into the dependence of the {ital b} distribution on cosmological parameters such as {Omega} and the power spectrum. A key parameter is the effective smoothing scale of the optical depth fluctuation, which is in turn determined by three scales: the thermal broadening width, the baryon smoothing scale (approximately the Jeans scale), and the observation/simulation resolution. The first two are determined by reionization history, but are comparable in general, whereas the third varies by about an order of magnitude in current hydrodynamic simulations. Studies with non

  8. A Comprehensive Spectroscopic Survey of z > 4 Galaxies in CANDELS

    NASA Astrophysics Data System (ADS)

    Papovich, Casey; McLure, Ross; Dickinson, Mark; Almaini, Omar; Bowler, Rebecca; Cirasuolo, Michele; Curtis-Lake, Emma; Dunlop, James; Faber, Sandra; Fazio, Giovanni; Ferguson, Harry; Fontana, Adriano; Finkelstein, Steven; Giavalisco, Mauro; Mobasher, Bahram; Pentericci, Laura; Salmon, Brett; Stark, Daniel; Tilvi, Vithal

    2012-08-01

    The basic statistical properties of galaxies at 4selected samples (e.g., Lyman-break galaxies). Making substantive progress now requires deep spectroscopy of these galaxies to deliver redshifts, stellar masses and star-formation rates (SFRs) accurate enough to test theoretical evolutionary paths of individual galaxies. We propose to obtain GMOS spectra of a magnitude limited, H(AB)<26.5, sample of 4.0galaxies in the UDS and COSMOS CANDELS fields: these are two fields with very deep HST and Spitzer data over the largest areas. Our principal science goal is to measure redshifts of > 200 galaxies at 42, while theory predicts it should decline with decreasing redshift. We will refute (or confirm) this emerging contradiction. Our second main science goal is to measure accurately the evolving frequency of Ly-alpha emission in these galaxies as a measure of the rising cosmic hydrogen neutral fraction at increasing redshift. This is a resubmission of a 2011B proposal, which was highly ranked but not schedulable in the queue. It was recommended we reapply, requesting classical time, which we do here.

  9. Multi-wavelength properties of submillimeter-selected galaxies

    NASA Astrophysics Data System (ADS)

    Hainline, Laura Jeannine

    The resolution of the cosmic far-infrared background at long wavelengths has uncovered a population of high-redshift, highly infrared-luminous galaxies that indicate that a significant amount of highly obscured star formation occurred in the early history of the Universe, which has not been taken into account in studies of the cosmic star formation and mass assembly histories. Since such studies are important tests of hierarchical galaxy formation models in a cold dark matter- dominated universe, it is vital that the contribution of these luminous submillimeter-selected galaxies to the buildup of stellar mass in the Universe be understood and included when testing galaxy formation models. Progress in understanding the nature of submillimeter-selected galaxies has been slow, however, due to the faintness of the population outside of the submillimeter bands and the coarse resolution of the single-dish submillimeter surveys in which the galaxies were discovered. The slow progress has at least two important consequences: (1) there is still much that is unknown about submillimeterselected galaxies at all wavelengths, so the properties of and evolutionary predictions for the population are often inferred by making analogies to local galaxies of similar luminosity and assuming the high-redshift galaxies represent a uniform population of galaxies; and (2) the relationships of the submillimeter-selected galaxies to other high-redshift galaxy populations selected at other wavelengths remain poorly understood.In this work we capitalize on recently-available observing resources of the Spitzer Space Telescope, at near- and mid-infrared wavelengths, and the Green Bank Telescope, at 1 cm, to improve the characterization of the largest representative sample of submillimeter-selected galaxies with spectroscopic redshifts. We combine our new data with data from the literature at a variety of wavelengths to place new constraints on the fundamental properties of gas mass, stellar mass

  10. COS-GTO: QSO Absorbers, Galaxies and Large-scale Structures in the Local Universe Part 2

    NASA Astrophysics Data System (ADS)

    Green, James

    2010-09-01

    This is a program to probe the large scale structure of baryons in the universe, including addressing questions of baryon fraction, physical conditions and relationships between absorbers and large-scale structures of galaxies. Besides these specific goals, this proposed GTO program also probes a large enough total path length in Ly alpha and OVI to add significantly to what STIS/FUSE has already observed. Several Galactic High Velocity Cloud Complexes also are probed by these sightlines, particularly the M Complex. The total path length of this proposed program for Ly alpha large-scale structure surveys is delta_z 5.5. We have selected a variety of targets to address these questions, under the following subcategories:1. Target 8 bright BL Lac objects to search for low contrast Ly alpha absorbers from the warm-hot interstellar medium {WHIM}. Science drivers: What are physical conditions and extent of warm-hot IGM in the current epoch? Can we discover metal-poor WHIM using very broad Ly alpha lines? What is the number density of such lines {dN/dz} and what is their relationship if any with tentative Chandra detections of even hotter gas?2. Ly alpha cloud sizes: The targets are a bright AGN pair which yield tangential distance separations of 100-500 kpc at z=0.01-0.05, where galaxy surveys are excellent. This pair has two filaments and two voids in this distance range. Science drivers: What are the characteristic sizes of Ly alpha absorbers, weak metal-line absorbers and absorbers in voids? Better size determinations will tighten current estimates of the baryon content of the photoionzed IGM .3. Probes of starburst outflows: The targets are bright AGN, <= 100 kpc in projection out of the minor axis of nearby starburst galaxies. Science drivers: Outflowing, unbound winds have been implicated as a primary mechanism to enrich the IGM in mass, metals and energy. But do starburst winds from massive galaxies escape the galaxy's gravitational potential? If so, what is the

  11. The 8 Coincidences of Galaxy Photometry - Selection Effects

    NASA Astrophysics Data System (ADS)

    Disney, M. J.; Phillipps, S.

    When the photometric properties of significant numbers of galaxies are compared, eight remarkable coincidences turn up. No convincing explanation for these have appeared so far. However, it may be that they can all be explained through a single powerful selection effect which brings into prominence only galaxies of certain favourable surface brightnesses. If that is the case, then our current understanding of galaxy populations is a delusion, and there must be many more galaxies about than we presently assume.

  12. How absorption selected galaxies trace the general high-redshift galaxy population

    NASA Astrophysics Data System (ADS)

    Christensen, Lise

    2015-08-01

    Strong absorption lines seen in quasar spectra arise when the lines of sight to the quasars intersect intervening galaxies. The associated metal absorption lines from the strongest absorption lines, the damped Lyman alpha absorbers (DLAs), allow us to trace the metallicity of galaxies back to redshifts z>5. Typical metallicities range from 0.1-100% solar metallicities with a huge scatter at any given redshift. Understanding the nature of galaxies that host DLAs is one strategy to probe the early phase and origin of stars in the outskirts of present-day galaxy disks.The search for emission from the elusive high-redshift DLA galaxies has reached a mature state now that we have determined how to best identify the absorbing galaxies. From a growing number of emission-line detections from DLA galaxies at redshifts ranging between 0.1 and 3, we can analyse galaxies in both absorption and emission, and probe the gas-phase metallicities in the outskirts and halos of the galaxies.By combining information for galaxies seen in emission and absorption, I will show that there is a relation between DLA metallicities and the host galaxy luminosities similar to the well-known the mass-metallicity relation for luminosity selected galaxies. This implies that DLA galaxies are drawn from the general population of low- to intermediate mass galaxies. We can determine a metallicity gradient in the extended halo of the galaxies out to ~40 kpc, and this allows us to reproduce observed galaxy correlation functions derived from conventional samples of luminosity selected galaxies.

  13. Low redshift Lyman alpha absorption lines and the dark matter halos of disk galaxies

    NASA Technical Reports Server (NTRS)

    Maloney, Philip

    1993-01-01

    Recent observations using the Hubble Space Telescope of the z = 0.156 QSO 3C 273 have discovered a surprisingly large number of Ly-alpha absorption lines. In particular, Morris et al. found 9 certain and 7 possible Ly-alpha lines with equivalent widths above 25 mA. This is much larger (by a factor of 5-10) than the number expected from extrapolation of the high-redshift behavior of the Ly-alpha forest. Within the context of pressure-confined models for the Ly-alpha clouds, this behavior can be understood if the ionizing background declines sharply between z is approximately 2 and z is approximately 0. However, this requires that the ionizing photon flux drop as rapidly as the QSO volume emissivity; moreover, the absorbers must have a space density n(sub O) is approximately 2.6(N/10)h/((D/100 kpc)(sup 2)) Mpc(sup -3) where D is the present-day diameter of the absorbers. It is somewhat surprising that such necessarily fragile objects could have survived in such numbers to the present day. It is shown that it is plausible that the atomic hydrogen extents of spiral and irregular galaxies are large enough to produce the observed number of Ly-alpha absorption lines toward 3C 273, and that the neutral column densities and doppler b-values expected under these conditions fall in the range found by Morris et al. (1991).

  14. Baryon content and dynamic state of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Wang, D.

    2016-06-01

    We are carrying out a panchromatic observing program to study the baryon content and dynamic state of galaxy clusters. In this talk, I will present results primarily from XMM-Newton observations of optically-selected clusters in the redshift range of 0.1-0.4. These clusters are selected because of their fortuitous alignment with background far-UV-bright QSOs, which thus allows for Ly-alpha and O VI absorption line spectroscopy with HST/COS, probing physical processes of the evolving intracluster medium, freshly accreted from the intergalactic medium and/or stripped out of individual galaxies, as well as the gaseous halos of individual cluster galaxies. Interestingly, such clusters tend to be dynamically young and often consist of merging subcluster pairs at similar redshifts. These subclusters themselves typically show substantial substructures, including strongly distorted radio lobes, as well as large position offsets between the diffuse X-ray centroids and the brightest galaxies. A comparison of the hot gas and stellar masses of each cluster with the expected cosmological baryonic mass fraction indicates a significant room for other gas components. I will also briefly examine the limitations of both optically and X-ray selected clusters, as well as how they may be used in a complementary fashion.

  15. Properties of an H I-selected galaxy sample

    NASA Technical Reports Server (NTRS)

    Szomoru, Arpad; Guhathakurta, Puragra; Van Gorkom, Jacqueline H.; Knapen, Johan H.; Weinberg, David H.; Fruchter, Andrew S.

    1994-01-01

    We analyze the properties of a sample of galaxies identified in a 21cm, H I-line survey of selected areas in the Perseus-Pisces supercluster and its foreground void. Twelve fields were observed in the supercluster, five of them (target fields) centered on optically bright galaxies, and the other seven (blank fields) selected to contain no bright galaxies within 45 min. of their centers. We detected nine previously uncatalogued, gas-rich galaxies, six of them in the target fields. We also detected H I from seven previously catalogued galaxies in these fields. Observations in the void covered the same volume as the 12 supercluster fields at the same H I-mass sensitivity, but no objects were detected. Combining out H I data with optical broadband and H alpha imaging, we conclude that the properties of H I-selected galaxies do not differ substantially from those of late-type galaxies found in optical surveys. In particular, the galaxies in our sample do not appear to be unusually faint for their H I mass, or for their circular velocity. We find tentative evidence for a connection between optical surface brightness and degree of isolation, in the sense that low surface brightness galaxies tend to be more isolated. The previously catalogued, optically bright galaxies in our survey volume dominate the total H I mass density and cross section; the uncatalogued galaxies contribute only approximately 19 percent of the mass and approximately 12 percent of the cross section. Thus, existing estimates of the density and cross section of neutral hydrogen, most of which are based on optically selected galaxy samples, are probably accurate. Such estimates can be used to compare the nearby universe to the high-redshift universe probed by quasar absorption lines.

  16. A search for molecular hydrogen and dust in the z = 2. 796 damped Ly-alpha absorber toward Q1337+113

    SciTech Connect

    Lanzetta, K.M.; Wolfe, A.M.; Turnshek, D.A.; Space Telescope Science Institute, Baltimore, MD )

    1989-09-01

    Spectroscopic and spectrophotometric observations and analyses are presented with the aim of ascertaining the presence of molecular hydrogen and dust in the damped Ly-alpha absorber toward Q1337+113. These observations are not sensitive to dust abundances. It is found that the abundance ratios of the metal elements are consistent with solar values, and that the C exp 0 column density is at least 200 times lower than for the H II region toward Zeta Oph. These results are consistent with a lack of dust in the absorber. A model of the equilibrium abundance of H2 is constructed, and the observed limit to the fractional H2 abundance is found capable of placing an independent upper limit on the dust content of the absorber at less than one-third the Galactic value. 58 refs.

  17. The theory of QSO absorption line systems and their relationship to the galaxies

    NASA Technical Reports Server (NTRS)

    Charlton, Jane

    1993-01-01

    The fundamental goal of this effort is to paint a picture of what the Ly-alpha forest clouds are and how they are distributed in space. Progress during the first phase of this program involved development of the 'Cheshire Cat Model' of Ly-alpha clouds in which systems over a large range of column densities are produced by disks with somewhat smaller column densities than those of normal galaxies. A prediction of the slab model of Ly-alpha clouds was confirmed by a new observational result, and the comparison of models to the new data allowed an estimate of the pressure of the intergalactic medium. This result should be forthcoming in pre-print form within the next month. The various results will now be described in more detail.

  18. The SAMI Galaxy Survey: instrument specification and target selection

    NASA Astrophysics Data System (ADS)

    Bryant, J. J.; Owers, M. S.; Robotham, A. S. G.; Croom, S. M.; Driver, S. P.; Drinkwater, M. J.; Lorente, N. P. F.; Cortese, L.; Scott, N.; Colless, M.; Schaefer, A.; Taylor, E. N.; Konstantopoulos, I. S.; Allen, J. T.; Baldry, I.; Barnes, L.; Bauer, A. E.; Bland-Hawthorn, J.; Bloom, J. V.; Brooks, A. M.; Brough, S.; Cecil, G.; Couch, W.; Croton, D.; Davies, R.; Ellis, S.; Fogarty, L. M. R.; Foster, C.; Glazebrook, K.; Goodwin, M.; Green, A.; Gunawardhana, M. L.; Hampton, E.; Ho, I.-T.; Hopkins, A. M.; Kewley, L.; Lawrence, J. S.; Leon-Saval, S. G.; Leslie, S.; McElroy, R.; Lewis, G.; Liske, J.; López-Sánchez, Á. R.; Mahajan, S.; Medling, A. M.; Metcalfe, N.; Meyer, M.; Mould, J.; Obreschkow, D.; O'Toole, S.; Pracy, M.; Richards, S. N.; Shanks, T.; Sharp, R.; Sweet, S. M.; Thomas, A. D.; Tonini, C.; Walcher, C. J.

    2015-03-01

    The SAMI Galaxy Survey will observe 3400 galaxies with the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) on the Anglo-Australian Telescope in a 3-yr survey which began in 2013. We present the throughput of the SAMI system, the science basis and specifications for the target selection, the survey observation plan and the combined properties of the selected galaxies. The survey includes four volume-limited galaxy samples based on cuts in a proxy for stellar mass, along with low-stellar-mass dwarf galaxies all selected from the Galaxy And Mass Assembly (GAMA) survey. The GAMA regions were selected because of the vast array of ancillary data available, including ultraviolet through to radio bands. These fields are on the celestial equator at 9, 12 and 14.5 h, and cover a total of 144 deg2 (in GAMA-I). Higher density environments are also included with the addition of eight clusters. The clusters have spectroscopy from 2-degree Field Galaxy Redshift Survey (2dFGRS) and Sloan Digital Sky Survey (SDSS) and photometry in regions covered by the SDSS and/or VLT Survey Telescope/ATLAS. The aim is to cover a broad range in stellar mass and environment, and therefore the primary survey targets cover redshifts 0.004 < z < 0.095, magnitudes rpet < 19.4, stellar masses 107-1012 M⊙, and environments from isolated field galaxies through groups to clusters of ˜1015 M⊙.

  19. A GREEN BANK TELESCOPE SURVEY FOR H I 21 cm ABSORPTION IN THE DISKS AND HALOS OF LOW-REDSHIFT GALAXIES

    SciTech Connect

    Borthakur, Sanchayeeta; Tripp, Todd M.; Yun, Min S.; Meiring, Joseph D.; Bowen, David V.; York, Donald G.; Momjian, Emmanuel

    2011-01-20

    We present an H I 21 cm absorption survey with the Green Bank Telescope (GBT) of galaxy-quasar pairs selected by combining galaxy data from the Sloan Digital Sky Survey (SDSS) and radio sources from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. Our sample consists of 23 sight lines through 15 low-redshift foreground galaxy-background quasar pairs with impact parameters ranging from 1.7 kpc up to 86.7 kpc. We detected one absorber in the GBT survey from the foreground dwarf galaxy, GQ1042+0747, at an impact parameter of 1.7 kpc and another possible absorber in our follow-up Very Large Array (VLA) imaging of the nearby foreground galaxy UGC 7408. The line widths of both absorbers are narrow (FWHM of 3.6 and 4.8km s{sup -1}). The absorbers have sub-damped Ly{alpha} column densities, and most likely originate in the disk gas of the foreground galaxies. We also detected H I emission from three foreground galaxies including UGC 7408. Although our sample contains both blue and red galaxies, the two H I absorbers as well as the H I emissions are associated with blue galaxies. We discuss the physical conditions in the 21 cm absorbers and some drawbacks of the large GBT beam for this type of survey.

  20. The gaseous extent of galaxies and the origin of Lyman-alpha absorption systems: A survey of galaxies in the fields of Hubble Space Telescope spectroscopic target QSOs

    NASA Technical Reports Server (NTRS)

    Lanzetta, Kenneth M.; Bowen, David B.; Tytler, David; Webb, John K.

    1995-01-01

    We present initial results of an imaging and spectroscopic survey of faint galaxies in fields of Hubble Space Telescope (HST) spectroscopic target QSOs. The primary objectives of the survey are (1) to determine the incidence, extent, and covering factor of extended gaseous envelopes of luminous galaxies and (2) to determine the fraction of Ly(alpha) absorption systems that arise in luminous galaxies. The goal of the survey is to identify in each field under construction all objects with apparent r-band magnitudes satisfying r less than 21.5 within angular distances to the QSOs satisfying 0 less thyan 1.3'. The current observations cover six fields and are 37% complete to the goal ofthe survey. These observations identify 46 galaxies at redshifts spanning z = 0.0700-0.5526 and at impact parameters to the QSOs spanning rho = 16.6-346.9/h kpc. Of these galaxies, 11 are coincident in redshift with absorption systems and 21 do not give rise to absorption to within sensitive upper limits. Nine galaxies are coincident in redshift with 'Ly(alpha)-forest' absorption systems that show Ly(alpha) absorption but no corresponding metal-line absorption, and two galaxies are coincident in redshift with C IV absorption systems that show both Ly(alpha) and C IV absorption. Various lines of evidence demonstrate that the coincident galaxies are responsible for the corresponding absorption systems and are not present as the result of chance coincidence or merely spatial correlated with the absorption systems. The most important evidence is that there exists a statistical anti-correlation between Ly(aplha) rest-frame equivalent width and the impact parameter. Each of five galaxies with rho = 70-160/h kpc give rise to Ly(alpha) absorption, and just one of nine galaxies with rho greater than 70-160/h kpc gives rise to Ly(alpha) absorption. At least eight of 23 Ly(alpha) absorption systyems arise in galaxies. On the basis of these results we reach the following conclusions: (1) At z less

  1. Multi-color imaging of selected southern interacting galaxies

    NASA Technical Reports Server (NTRS)

    Smith, Eric P.; Hintzen, Paul

    1990-01-01

    The authors present preliminary results from a study of selected Arp-Madore Southern Hemisphere peculiar galaxies. Broadband charge coupled device (CCD) images (BVRI) of a subset of these galaxies allow us to study each galaxy's optical morphology, color, and (in a crude manner) degree of nuclear activity, and to compare them with similar data we possess on other active galaxies. Many of these galaxies have optical morphologies closely resembling those of powerful radio galaxies (Smith and Heckman 1989), yet their radio emission is unremarkable. Accurate positions for subsequent spectroscopic studies have been determined along with broad band photometry and morphology studies. Detailed observations of these comparatively bright, low-redshift, well-resolved interacting systems should aid our understanding of the role interactions play in triggering galaxy activity. This work is the initial effort in a long term project to study the role played by the dynamics of the interaction in the production and manifestations of activity in galaxies, and the frequency of galaxy mergers.

  2. TRACING GALAXIES THROUGH COSMIC TIME WITH NUMBER DENSITY SELECTION

    SciTech Connect

    Leja, Joel; Van Dokkum, Pieter; Franx, Marijn

    2013-03-20

    A central challenge in observational studies of galaxy formation is how to associate progenitor galaxies with their descendants at lower redshifts. One promising approach is to link galaxies at fixed number density rather than fixed luminosity or mass. This method is effective if stellar mass rank order is broadly conserved through cosmic time. In this paper, we use the Guo et al. semi-analytical model to analyze under what circumstances this assumption is valid in the context of a cosmological simulation. Specifically, we select progenitor galaxies at a constant number density and compare the stellar mass evolution of their descendants to the evolution at a constant number density. The median stellar mass of the descendants increases by a factor of four (0.6 dex) from z = 3 to z = 0. Constant number density selection reproduces this to within 40% (0.15 dex) over a wide range of number densities. We show that the discrepancy primarily results from scatter in the stellar mass growth rates and merging. After applying simple, observationally based corrections for these processes, the discrepancy is reduced to 12% (0.05 dex). We conclude that number density selection can be used to predict the median descendant mass of high-redshift progenitor galaxies. The main uncertainty in this study is that semi-analytical models do not reproduce the observed mass evolution of galaxies, which makes the quantitative aggregate effects of star formation, merging, and quenching on the rank order of galaxies somewhat uncertain.

  3. Ultraviolet and optical spectra of broadline radio galaxies

    NASA Technical Reports Server (NTRS)

    Crenshaw, D. Michael; Peterson, Bradley M.; Wagner, R. Mark

    1988-01-01

    Near-simultaneous ultraviolet and optical spectra of three broadline radio galaxies (3C 382, 3C 445, and PKS 2349-014) have been obtained, and the emission lines of Ly-alpha, H-beta, and H-alpha have been deconvolved into narrow and broad components; published fluxes for 3C 390.3 are also included in this study. Although the broad Ly-alpha/H-beta ratios in these objects cover a large range (1.2-22.3), there is no evidence that these ratios are intrinsically different from those of Seyfert 1 galaxies or quasars. Thus, in general, the higher H-alpha/H-beta ratios in these broadline radio galaxies cannot entirely be due to additional reddening of the broadline region. However, in the specific case of 3C 445, there is evidence that the nonstellar continuum and broadline region are highly reddened.

  4. SUBMILLIMETER FOLLOW-UP OF WISE-SELECTED HYPERLUMINOUS GALAXIES

    SciTech Connect

    Wu Jingwen; Eisenhardt, Peter R. M.; Stern, Daniel; Assef, Roberto; Tsai, Chao-Wei; Cutri, Roc; Griffith, Roger; Jarrett, Thomas; Sayers, Jack; Bridge, Carrie; Benford, Dominic; Blain, Andrew; Petty, Sara; Lake, Sean; Bussmann, Shane; Comerford, Julia M.; Evans, Neal J. II; Lonsdale, Carol; Rho, Jeonghee; Stanford, S. Adam; and others

    2012-09-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare ({approx}1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 {mu}m, yet are clearly detected at 12 and 22 {mu}m. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 {mu}m, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 {mu}m, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10{sup 13} L{sub Sun }. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  5. Submillimeter Follow-Up of WISE-Selected Hyperluminous Galaxies

    NASA Technical Reports Server (NTRS)

    Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R.; Stern, Daniel; Petty, Sara; Assef, Roberto; Bussmann, Shane; Comerford, Julia M.; Cutri, Roc; Evans, Neal J., II; Griffith, Roger; Jarrett, Thomas; Lake, Sean; Lonsdale, Carol; Rho, Jeonghee; Stanford, S. Adam; Weiner, Benjamin; Wright, Edward L.; Yan, Lin

    2012-01-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (approx.1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 microns, yet are clearly detected at 12 and 22 microns. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 microns, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 microns, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature.We estimate their dust temperatures to be 60 C120 K using a single-temperature model. Their infrared luminosities are well over 10(exp 13) Stellar Luminosity. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe.We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  6. Submillimeter Follow-up of Wise-Selected Hyperluminous Galaxies

    NASA Technical Reports Server (NTRS)

    Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R. M.; Stern, Daniel; Petty, Sara; Assef, Roberto; Bussmann, Shane; Comerford, Julia M.; Cutri, Roc; Evans, Neal J., II; Griffith, Roger; Jarrett, Thomas; Lake, Sean; Lonsdale, Carol; Rho, Jeonghee; Stanford, S. Adam

    2013-01-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (approximately 1000 all-sky) population of galaxies at high redshift (peaks at zeta = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 micrometers, yet are clearly detected at 12 and 22 micrometers. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (zeta greater than 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 micrometers, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 micrometers, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature.We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10(exp 13) solar luminosity. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe.We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  7. THE SCATTERING POLARIZATION OF THE Ly{alpha} LINES OF H I AND He II TAKING INTO ACCOUNT PARTIAL FREQUENCY REDISTRIBUTION AND J-STATE INTERFERENCE EFFECTS

    SciTech Connect

    Belluzzi, Luca; Trujillo Bueno, Javier; Stepan, Jiri

    2012-08-10

    Recent theoretical investigations have pointed out that the cores of the Ly{alpha} lines of H I and He II should show measurable scattering polarization signals when observing the solar disk, and that the magnetic sensitivity, through the Hanle effect, of such linear polarization signals is suitable for exploring the magnetism of the solar transition region. Such investigations were carried out in the limit of complete frequency redistribution (CRD) and neglecting quantum interference between the two upper J-levels of each line. Here we relax both approximations and show that the joint action of partial frequency redistribution and J-state interference produces much more complex fractional linear polarization (Q/I) profiles, with large amplitudes in their wings. Such wing polarization signals turn out to be very sensitive to the temperature structure of the atmospheric model, so that they can be exploited for constraining the thermal properties of the solar chromosphere. Finally, we show that the approximation of CRD without J-state interference is however suitable for estimating the amplitude of the linear polarization signals in the core of the lines, where the Hanle effect operates.

  8. Evolution of Balmer jump selected galaxies in the ALHAMBRA survey

    NASA Astrophysics Data System (ADS)

    Troncoso Iribarren, P.; Infante, L.; Padilla, N.; Lacerna, I.; Garcia, S.; Orsi, A.; Muñoz Arancibia, A.; Moustakas, J.; Cristóbal-Hornillos, D.; Moles, M.; Fernández-Soto, A.; Martínez, V. J.; Cerviño, M.; Alfaro, E. J.; Ascaso, B.; Arnalte-Mur, P.; Nieves-Seoane, L.; Benítez, N.

    2016-04-01

    Context. Samples of star-forming galaxies at different redshifts have been traditionally selected via color techniques. The ALHAMBRA survey was designed to perform a uniform cosmic tomography of the Universe, and we here exploit it to trace the evolution of these galaxies. Aims: Our objective is to use the homogeneous optical coverage of the ALHAMBRA filter system to select samples of star-forming galaxies at different epochs of the Universe and study their properties. Methods: We present a new color-selection technique, based on the models of spectral evolution convolved with the ALHAMBRA bands and the redshifted position of the Balmer jump to select star-forming galaxies in the redshift range 0.5 galaxies are dubbed Balmer-jump Galaxies (BJGs). We applied the iSEDfit Bayesian approach to fit each detailed spectral energy distribution and determined star-formation rate (SFR), stellar mass, age, and absolute magnitudes. The mass of the halos in which these samples reside were found through a clustering analysis. Results: Five volume-limited BJG subsamples with different mean redshifts are found to reside in halos of median masses ~1012.5 ± 0.2 M⊙ slightly increasing toward z = 0.5. This increment is similar to numerical simulations results, which suggests that we trace the evolution of an evolving population of halos as they grow to reach a mass of ~1012.7 ± 0.1 at z = 0.5. The likely progenitors of our samples at z ~ 3 are Lyman-break galaxies, which at z ~ 2 would evolve into star-forming BzK galaxies, and their descendants in the local Universe are galaxies with luminosities of 1-3 L∗. Hence, this allows us to follow the putative evolution of the SFR, stellar mass, and age of these galaxies. Conclusions: From z ~ 1.0 to z ~ 0.5, the stellar mass of the volume-limited BJG samples changes almost not at all with redshift, suggesting that major mergers play a minor role in the evolution of these galaxies. The SFR evolution accounts for the small

  9. Are dusty galaxies blue? Insights on UV attenuation from dust-selected galaxies

    SciTech Connect

    Casey, C. M.; Cooray, A.; Scoville, N. Z.; Sanders, D. B.; Lee, N.; Finkelstein, S. L.; Capak, P.; Conley, A.; De Zotti, G.; Farrah, D.; Fu, H.; Le Floc'h, E.; Ilbert, O.; Ivison, R. J.; Takeuchi, T. T.

    2014-12-01

    Galaxies' rest-frame ultraviolet (UV) properties are often used to directly infer the degree to which dust obscuration affects the measurement of star formation rates (SFRs). While much recent work has focused on calibrating dust attenuation in galaxies selected at rest-frame ultraviolet wavelengths, locally and at high-z, here we investigate attenuation in dusty, star forming galaxies (DSFGs) selected at far-infrared wavelengths. By combining multiwavelength coverage across 0.15-500 μm in the COSMOS field, in particular making use of Herschel imaging, and a rich data set on local galaxies, we find an empirical variation in the relationship between the rest-frame UV slope (β) and the ratio of infrared-to-ultraviolet emission (L {sub IR}/L {sub UV} ≡ IRX) as a function of infrared luminosity, or total SFR. Both locally and at high-z, galaxies above SFR ≳ 50 M {sub ☉} yr{sup –1} deviate from the nominal IRX-β relation toward bluer colors by a factor proportional to their increasing IR luminosity. We also estimate contamination rates of DSFGs on high-z dropout searches of <<1% at z ≲ 4-10, providing independent verification that contamination from very dusty foreground galaxies is low in Lyman-break galaxy searches. Overall, our results are consistent with the physical interpretation that DSFGs, e.g., galaxies with >50 M {sub ☉} yr{sup –1}, are dominated at all epochs by short-lived, extreme burst events, producing many young O and B stars that are primarily, yet not entirely, enshrouded in thick dust cocoons. The blue rest-frame UV slopes of DSFGs are inconsistent with the suggestion that most DSFGs at z ∼ 2 exhibit steady-state star formation in secular disks.

  10. Selecting background galaxies in weak-lensing analysis of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Formicola, I.; Radovich, M.; Meneghetti, M.; Mazzotta, P.; Grado, A.; Giocoli, C.

    2016-05-01

    In this paper, we present a new method to select the faint, background galaxies used to derive the mass of galaxy clusters by weak lensing. The method is based on the simultaneous analysis of the shear signal, that should be consistent with zero for the foreground, unlensed galaxies, and of the colours of the galaxies: photometric data from the COSMic evOlution Survey are used to train the colour selection. In order to validate this methodology, we test it against a set of state-of-the-art image simulations of mock galaxy clusters in different redshift [0.23-0.45] and mass [0.5-1.55 × 1015 M⊙] ranges, mimicking medium-deep multicolour imaging observations [e.g. Subaru, Large Binocular Telescope]. The performance of our method in terms of contamination by unlensed sources is comparable to a selection based on photometric redshifts, which however requires a good spectral coverage and is thus much more observationally demanding. The application of our method to simulations gives an average ratio between estimated and true masses of ˜0.98 ± 0.09. As a further test, we finally apply our method to real data, and compare our results with other weak-lensing mass estimates in the literature: for this purpose, we choose the cluster Abell 2219 (z = 0.228), for which multiband (BVRi) data are publicly available.

  11. HI Selected Galaxies from the SDSS and HIPASS

    NASA Astrophysics Data System (ADS)

    West, A. A.; Garcia-Appadoo, D. A.; Dalcanton, J. J.; Rockosi, C. M.; Disney, M. J.

    2004-12-01

    We present results from a study of HI selected galaxies that fall within both the HI Parkes All Sky Survey (HIPASS) and the Sloan Digital Sky Survey (SDSS). By comparing the optical properties derived from the SDSS 5-band photometry with the HI properties from HIPASS, we are able to probe the relationship between the stellar populations and the neutral gas over a range of Hubble types. Our HIPASS/SDSS catalog provides a uniform, homogeneous data set that can be used to investigate the factors that contribute to star formation on global scales. The HI selection has allowed us to identify a significant group of low surface brightness galaxies, not included in most SDSS studies. In addition, the construction of this catalog has led to a set of tools to aid in the analysis of large nearby galaxies in the SDSS.

  12. BRIGHT Lights, BIG City: Massive Galaxies, Giant Ly-A Nebulae, and Proto-Clusters

    SciTech Connect

    van Breugel, W; Reuland, M; de Vries, W; Stanford, A; Dey, A; Kurk, J; Venemans, B; Rottgering, H; Miley, G; De Breuck, C; Dopita, M; Sutherland, R; Bland-Hawthorn, J

    2002-08-01

    High redshift radio galaxies are great cosmological tools for pinpointing the most massive objects in the early Universe: massive forming galaxies, active super-massive black holes and proto-clusters. They report on deep narrow-band imaging and spectroscopic observations of several z > 2 radio galaxy fields to investigate the nature of giant Ly-{alpha} nebulae centered on the galaxies and to search for over-dense regions around them. They discuss the possible implications for our understanding of the formation and evolution of massive galaxies and galaxy clusters.

  13. Star formation rates in isolated galaxies selected from the Two-Micron All-Sky Survey

    NASA Astrophysics Data System (ADS)

    Melnyk, O.; Karachentseva, V.; Karachentsev, I.

    2015-08-01

    We have considered the star formation properties of 1616 isolated galaxies from the 2MASS XSC (Extended Source Catalog) selected sample (2MIG) with the far-ultraviolet GALEX magnitudes. This sample was then compared with corresponding properties of isolated galaxies from the Local Orphan Galaxies (LOG) catalogue and paired galaxies. We found that different selection algorithms define different populations of isolated galaxies. The population of the LOG catalogue, selected from non-clustered galaxies in the Local Supercluster volume, mostly consists of low-mass spiral and late-type galaxies. The specific star formation rate (SSFR) upper limit in isolated and paired galaxies does not exceed the value of ˜dex(-9.4). This is probably common for galaxies of differing activity and environment (at least at z < 0.06). The fractions of quenched galaxies are nearly twice as high in the paired galaxy sample as in the 2MIG isolated galaxy sample. From the behaviour of (S)SFR versus M* relations we deduced that the characteristic value influencing evolutionary processes is the galaxy mass. However, the environmental influence is notable: paired massive galaxies with logM* > 11.5 have higher (S)SFR than isolated galaxies. Our results suggest that the environment helps to trigger the star formation in the highest mass galaxies. We found that the fraction of AGN in the paired sample is only a little higher than in our isolated galaxy sample. We assume that AGN phenomenon is probably defined by secular galaxy evolution.

  14. Infrared Color Selection of Massive Galaxies at z > 3

    NASA Astrophysics Data System (ADS)

    Wang, T.; Elbaz, D.; Schreiber, C.; Pannella, M.; Shu, X.; Willner, S. P.; Ashby, M. L. N.; Huang, J.-S.; Fontana, A.; Dekel, A.; Daddi, E.; Ferguson, H. C.; Dunlop, J.; Ciesla, L.; Koekemoer, A. M.; Giavalisco, M.; Boutsia, K.; Finkelstein, S.; Juneau, S.; Barro, G.; Koo, D. C.; Michałowski, M. J.; Orellana, G.; Lu, Y.; Castellano, M.; Bourne, N.; Buitrago, F.; Santini, P.; Faber, S. M.; Hathi, N.; Lucas, R. A.; Pérez-González, P. G.

    2016-01-01

    We introduce a new color selection technique to identify high-redshift, massive galaxies that are systematically missed by Lyman-break selection. The new selection is based on the H160 (H) and Infrared Array Camera (IRAC) 4.5 μm bands, specifically H-[4.5]\\gt 2.25 mag. These galaxies, called “HIEROs,” include two major populations that can be separated with an additional J - H color. The populations are massive and dusty star-forming galaxies at z\\gt 3 ({JH}-{blue}) and extremely dusty galaxies at z≲ 3 ({JH}-{red}). The 350 arcmin2 of the GOODS-North and GOODS-South fields with the deepest Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) near-infrared and IRAC data contain as many as 285 HIEROs down to [4.5]\\lt 24 mag. Inclusion of the most extreme HIEROs, not even detected in the H band, makes this selection particularly complete for the identification of massive high-redshift galaxies. We focus here primarily on {JH}-{blue} (z\\gt 3) HIEROs, which have a median photometric redshift < z> ˜ 4.4 and stellar mass {M}*˜ {10}10.6 {M}⊙ and are much fainter in the rest-frame UV than similarly massive Lyman-break galaxies (LBGs). Their star formation rates (SFRs), derived from their stacked infrared spectral energy distributions (SEDs), reach ˜240 {M}⊙ yr-1, leading to a specific SFR, {{sSFR}}\\equiv {{SFR}}/{M}*˜ 4.2 Gyr-1, suggesting that the sSFRs for massive galaxies continue to grow at z\\gt 2 but at a lower growth rate than from z = 0 to z = 2. With a median half-light radius of 2 kpc, including ˜ 20% as compact as quiescent (QS) galaxies at similar redshifts, {JH}-{blue} HIEROs represent perfect star-forming progenitors of the most massive ({M}*≳ {10}11.2 {M}⊙ ) compact QS galaxies at z˜ 3 and have the right number density. HIEROs make up ˜ 60% of all galaxies with {M}*\\gt {10}10.5 {M}⊙ identified at z\\gt 3 from their photometric redshifts. This is five times more than LBGs with nearly no overlap between the two populations

  15. Spatial density fluctuations and selection effects in galaxy redshift surveys

    SciTech Connect

    Labini, Francesco Sylos; Tekhanovich, Daniil; Baryshev, Yurij V. E-mail: d.tekhanovich@spbu.ru

    2014-07-01

    One of the main problems of observational cosmology is to determine the range in which a reliable measurement of galaxy correlations is possible. This corresponds to determining the shape of the correlation function, its possible evolution with redshift and the size and amplitude of large scale structures. Different selection effects, inevitably entering in any observation, introduce important constraints in the measurement of correlations. In the context of galaxy redshift surveys selection effects can be caused by observational techniques and strategies and by implicit assumptions used in the data analysis. Generally all these effects are taken into account by using pair-counting algorithms to measure two-point correlations. We review these methods stressing that they are based on the a-priori assumption that galaxy distribution is spatially homogeneous inside a given sample. We show that, when this assumption is not satisfied by the data, results of the correlation analysis are affected by finite size effects. In order to quantify these effects, we introduce a new method based on the computation of the gradient of galaxy counts along tiny cylinders. We show, by using artificial homogeneous and inhomogeneous point distributions, that this method identifies redshift dependent selection effects and disentangles them from the presence of large scale density fluctuations. We then apply this new method to several redshift catalogs and we find evidence that galaxy distribution, in those samples where selection effects are small enough, is characterized by power-law correlations with exponent γ=0.9 up to 20 Mpc/h followed by a change of slope that, in the range 20–100 Mpc/h, corresponds to a power-law exponent γ=0.25. Whether a crossover to spatial uniformity occurs at ∼ 100 Mpc/h or larger scales cannot be clarified by the present data.

  16. EXTREME EMISSION-LINE GALAXIES IN CANDELS: BROADBAND-SELECTED, STARBURSTING DWARF GALAXIES AT z > 1

    SciTech Connect

    Van der Wel, A.; Rix, H.-W.; Jahnke, K.; Straughn, A. N.; Finkelstein, S. L.; Salmon, B. W.; Koekemoer, A. M.; Ferguson, H. C.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D. C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Dickinson, M.; De Mello, D. F.; and others

    2011-12-01

    We identify an abundant population of extreme emission-line galaxies (EELGs) at redshift z {approx} 1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). Sixty-nine EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broadband magnitudes. Supported by spectroscopic confirmation of strong [O III] emission lines-with rest-frame equivalent widths {approx}1000 A-in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with {approx}10{sup 8} M{sub Sun} in stellar mass, undergoing an enormous starburst phase with M{sub *}/ M-dot{sub *} of only {approx}15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the comoving number density (3.7 Multiplication-Sign 10{sup -4} Mpc{sup -3}) can produce in {approx}4 Gyr much of the stellar mass density that is presently contained in 10{sup 8}-10{sup 9} M{sub Sun} dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z > 1.

  17. THE ALFALFA H I ABSORPTION PILOT SURVEY: A WIDE-AREA BLIND DAMPED Ly{alpha} SYSTEM SURVEY OF THE LOCAL UNIVERSE

    SciTech Connect

    Darling, Jeremy; Macdonald, Erin P.; Haynes, Martha P.; Giovanelli, Riccardo E-mail: e.macdonald@physics.gla.ac.uk E-mail: riccardo@astro.cornell.edu

    2011-11-20

    We present the results of a pilot survey for neutral hydrogen (H I) 21 cm absorption in the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFALFA) Survey. This project is a wide-area 'blind' search for H I absorption in the local universe, spanning -650 km s{sup -1} < cz < 17, 500 km s{sup -1} and covering 517.0 deg{sup 2} (7% of the full ALFALFA survey). The survey is sensitive to H I absorption lines stronger than 7.7 mJy (8983 radio sources) and is 90% complete for lines stronger than 11.0 mJy (7296 sources). The total redshift interval sensitive to all damped Ly{alpha} (DLA) systems (N{sub H{sub i}}{>=}2 Multiplication-Sign 10{sup 20} cm{sup -2}) is {Delta}z = 7.0 (129 objects, assuming T{sub s} = 100 K and covering fraction unity); for super-DLAs (N{sub H{sub i}}{>=}2 Multiplication-Sign 10{sup 21} cm{sup -2}) it is {Delta}z = 128.2 (2353 objects). We re-detect the intrinsic H I absorption line in UGC 6081 but detect no intervening absorption line systems. We compute a 95% confidence upper limit on the column density frequency distribution function f(N{sub H{sub i}},X) spanning four orders of magnitude in column density, 10{sup 19} (T{sub s} /100 K) (1/f) cm{sup -2}

  18. A METAL-STRONG AND DUST-RICH DAMPED Ly{alpha} ABSORPTION SYSTEM TOWARD THE QUASAR SDSS J115705.52+615521.7

    SciTech Connect

    Wang Jianguo; Ge Jian; Hamann, Fred; Xavier Prochaska, J.

    2012-11-20

    We report the discovery of an unusual, extremely dust-rich and metal-strong damped Ly{alpha} absorption system (DLA) at a redshift z{sub a} = 2.4596 toward the quasar SDSS J115705.52+615521.7 with an emission-line redshift z{sub e} = 2.5125. The quasar spectrum, taken in the Sloan Digital Sky Survey, shows a very red color and a number of metal absorption lines, including C II, Al II, Si II, Fe II, and Zn II, which are confirmed and further characterized by follow-up spectroscopy made with the Multiple Mirror Telescope. Its neutral hydrogen column density N {sub HI} = 10{sup 21.8{+-}0.2} cm{sup -2} is among the highest values measured in quasar DLAs. The measured metal column density is N {sub ZnII} Almost-Equal-To 10{sup 13.8} cm{sup -2}, which is about 1.5 times larger than the largest value in any previously observed quasar DLAs. We derive the extinction curve of the dusty DLA using a new technique, which is an analog of the 'pair method' widely used to measure extinction curves in the Milky Way (MW). The best-fit curve is an MW-like law with a significant broad feature centered around 2175 A in the rest frame of the absorber. The measured extinction A{sub V} Almost-Equal-To 0.92 mag is unprecedentedly high in quasar DLAs. After applying an extinction correction, the i-band absolute magnitude of the quasar is as high as M{sub i} Almost-Equal-To -29.4 mag, placing it as one of the most luminous quasars ever known. The large gas-phase relative abundance of [Zn/Fe] Almost-Equal-To 1.0 indicates that metals are heavily depleted onto dust grains in the absorber. The dust depletion level is between that of the warm and cool clouds in the MW. This discovery is suggestive of the existence of a rare yet important population of dust-rich DLAs with both high metallicities and high column densities, which may have significant impact on the measurement of the cosmic evolution of neutral gas mass density and metallicity.

  19. Intergalactic Hydrogen Clouds at Low Redshift: Connections to Voids and Dwarf Galaxies

    NASA Technical Reports Server (NTRS)

    Shull, J. Michael; Stocke, John T.; Penton, Steve

    1996-01-01

    We provide new post-COSTAR data on one sightline (Mrk 421) and updated data from another (I Zw 1) from our Hubble Space Telescope (HST) survey of intergalactic Ly(alpha) clouds located along sightlines to four bright quasars passing through well-mapped galaxy voids (16000 km/s pathlength) and superclusters (18000 km/s). We report two more definite detections of low-redshift Ly(alpha) clouds in voids: one at 3047 km/s (heliocentric) toward Mrk 421 and a second just beyond the Local Supercluster at 2861 km/s toward I Zw 1, confirming our earlier discovery of Ly(alpha) absorption clouds in voids (Stocke et al., ApJ, 451, 24). We have now identified ten definite and one probable low-redshift neutral hydrogen absorption clouds toward four targets, a frequency of approximately one absorber every 3400 km/s above 10(exp 12.7/sq cm column density. Of these ten absorption systems, three lie within voids; the probable absorber also lies in a void. Thus, the tendency of Ly(alpha) absorbers to 'avoid the voids' is not as clear as we found previously. If the Ly(alpha) clouds are approximated as homogeneous spheres of 100 kpc radius, their masses are approximately 10(exp 9)solar mass (about 0.01 times that of bright L* galaxies) and they are 40 times more numerous, comparable to the density of dwarf galaxies and of low-mass halos in numerical CDM simulations. The Ly(alpha) clouds contribute a fraction Omega(sub cl)approximately equals 0.003/h(sub 75) to the closure density of the universe, comparable to that of luminous matter. These clouds probably require a substantial amount of nonbaryonic dark matter for gravitational binding. They may represent extended haloes of low-mass protogalaxies which have not experienced significant star formation or low-mass dwarf galaxies whose star formation ceased long ago, but blew out significant gaseous material.

  20. Complex Investigation of SBS Galaxies in Seven Selected Fields

    NASA Astrophysics Data System (ADS)

    Hakopian, Susanna

    2014-07-01

    It is known that the main criterion for the selection of active objects in the First Byurakan, otherwise Markarian survey was the presence of signs of UV-excess in their low-dispersion spectra. Using the presence of emission lines as the second criteria became real during the Second Byurakan survey because of its improved technique. Extended (not stellated) objects, selected with the use of this criterion, made the main part of the separate sample of SBS galaxies. Originally, this sample included 1286 objects, selected in 65 fields of the survey (16 square degree each), to which, with the help of other sources than the survey, there were later added some objects. We studied a subsample of SBS galaxies in seven selected fields (the deepest according to the V/Vmax criterion), including about the third of the whole sample. The first, already completed phase of this program was started with carrying out a follow-up slit spectroscopy of all, about 500 objects, based on observations with long-slit spectrographs with 6m telescope of SAO Russia and 2.6.m telescope of Byurakan. As a result redshifts were determined, as well as spectral classification was made for all of objects, using the scheme adapted to the spectral material. Besides other, obtained data allowed us to estimate the efficiency of used criteria for the selection of galaxies of different classes of starformation and nuclear activity along the full scale of the apparent magnitudes, including close to the limit values (18.5 < m pg < 19.5), etc. The fact that the total area of seven fields as the total number of objects in them comparable with these values for the survey as a whole, allows us to extrapolate the results to the whole sample of galaxies as an upper estimate. The second stage is to conduct detailed studies of individual galaxies in the first place, the most interesting in terms of morphology. They are based on panoramic spectroscopy obtained from observations at 6 m telescope of Russia and 2.6m

  1. Tuning target selection algorithms to improve galaxy redshift estimates

    NASA Astrophysics Data System (ADS)

    Hoyle, Ben; Paech, Kerstin; Rau, Markus Michael; Seitz, Stella; Weller, Jochen

    2016-06-01

    We showcase machine learning (ML) inspired target selection algorithms to determine which of all potential targets should be selected first for spectroscopic follow-up. Efficient target selection can improve the ML redshift uncertainties as calculated on an independent sample, while requiring less targets to be observed. We compare seven different ML targeting algorithms with the Sloan Digital Sky Survey (SDSS) target order, and with a random targeting algorithm. The ML inspired algorithms are constructed iteratively by estimating which of the remaining target galaxies will be most difficult for the ML methods to accurately estimate redshifts using the previously observed data. This is performed by predicting the expected redshift error and redshift offset (or bias) of all of the remaining target galaxies. We find that the predicted values of bias and error are accurate to better than 10-30 per cent of the true values, even with only limited training sample sizes. We construct a hypothetical follow-up survey and find that some of the ML targeting algorithms are able to obtain the same redshift predictive power with 2-3 times less observing time, as compared to that of the SDSS, or random, target selection algorithms. The reduction in the required follow-up resources could allow for a change to the follow-up strategy, for example by obtaining deeper spectroscopy, which could improve ML redshift estimates for deeper test data.

  2. A LINK TO THE PAST: USING MARKOV CHAIN MONTE CARLO FITTING TO CONSTRAIN FUNDAMENTAL PARAMETERS OF HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Pirzkal, N.; Rothberg, B.; Koekemoer, Anton; Nilsson, Kim K.; Finkelstein, S.; Malhotra, Sangeeta; Rhoads, James

    2012-04-01

    We have developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 < z < 8) galaxies. Our approach uses an implementation of Bayesian based Markov Chain Monte Carlo that we have dubbed '{pi}MC{sup 2}'. It allows us to compare observations to arbitrarily complex models and to compute 95% credible intervals that provide robust constraints for the model parameters. The work is presented in two sections. In the first, we test {pi}MC{sup 2} using simulated SEDs to not only confirm the recovery of the known inputs but to assess the limitations of the method and identify potential hazards of SED fitting when applied specifically to high-redshift (z > 4) galaxies. In the second part of the paper we apply {pi}MC{sup 2} to thirty-three 4 < z < 8 objects, including the spectroscopically confirmed Grism ACS Program for Extragalactic Science Ly{alpha} sample (4 < z < 6), supplemented by newly obtained Hubble Space Telescope/WFC3 near-IR observations, and several recently reported broadband selected z > 6 galaxies. Using {pi}MC{sup 2}, we are able to constrain the stellar mass of these objects and in some cases their stellar age and find no evidence that any of these sources formed at a redshift larger than z = 8, a time when the universe was Almost-Equal-To 0.6 Gyr old.

  3. GRB 130606A AS A PROBE OF THE INTERGALACTIC MEDIUM AND THE INTERSTELLAR MEDIUM IN A STAR-FORMING GALAXY IN THE FIRST Gyr AFTER THE BIG BANG

    SciTech Connect

    Chornock, Ryan; Berger, Edo; Lunnan, Ragnhild; Drout, Maria R.; Fong Wenfai; Laskar, Tanmoy; Fox, Derek B.; Roth, Katherine C.

    2013-09-01

    We present high signal-to-noise ratio Gemini and MMT spectroscopy of the optical afterglow of the gamma-ray burst (GRB) 130606A at redshift z = 5.913, discovered by Swift. This is the first high-redshift GRB afterglow to have spectra of comparable quality to those of z Almost-Equal-To 6 quasars. The data exhibit a smooth continuum at near-infrared wavelengths that is sharply cut off blueward of 8410 A due to absorption from Ly{alpha} at redshift z Almost-Equal-To 5.91, with some flux transmitted through the Ly{alpha} forest between 7000 and 7800 A. We use column densities inferred from metal absorption lines to constrain the metallicity of the host galaxy between a lower limit of [Si/H] {approx}> -1.7 and an upper limit of [S/H] {approx}< -0.5 set by the non-detection of S II absorption. We demonstrate consistency between the dramatic evolution in the transmission fraction of Ly{alpha} seen in this spectrum over the redshift range z = 4.9-5.85 with that previously measured from observations of high-redshift quasars. There is an extended redshift interval of {Delta}z = 0.12 in the Ly{alpha} forest at z = 5.77 with no detected transmission, leading to a 3{sigma} upper limit on the mean Ly{alpha} transmission fraction of {approx}<0.2% (or {tau}{sub GP}{sup eff} (Ly{alpha}) > 6.4). This is comparable to the lowest-redshift Gunn-Peterson troughs found in quasar spectra. Some Ly{beta} and Ly{gamma} transmission is detected in this redshift window, indicating that it is not completely opaque, and hence that the intergalactic medium (IGM) is nonetheless mostly ionized at these redshifts. We set a 2{sigma} upper limit of 0.11 on the neutral fraction of the IGM at the redshift of the GRB from the lack of a Ly{alpha} red damping wing, assuming a model with a constant neutral density. GRB 130606A thus for the first time realizes the promise of GRBs as probes of the first galaxies and cosmic reionization.

  4. A HST/WFC3-IR MORPHOLOGICAL SURVEY OF GALAXIES AT z = 1.5-3.6. II. THE RELATION BETWEEN MORPHOLOGY AND GAS-PHASE KINEMATICS

    SciTech Connect

    Law, David R.; Steidel, Charles C.; Shapley, Alice E.; Nagy, Sarah R.; Reddy, Naveen A.; Erb, Dawn K. E-mail: ccs@astro.caltech.edu E-mail: snagy@ucla.edu

    2012-11-01

    We analyze rest-frame optical morphologies and gas-phase kinematics as traced by rest-frame far-UV and optical spectra for a sample of 204 star-forming galaxies in the redshift range z {approx} 2-3 drawn from the Keck Baryonic Structure Survey. We find that spectroscopic properties and gas-phase kinematics are closely linked to morphology: compact galaxies with semimajor axis radii r {approx}< 2 kpc are substantially more likely than their larger counterparts to exhibit Ly{alpha} in emission. Although Ly{alpha} emission strength varies widely within galaxies of a given morphological type, all but one of 19 galaxies with Ly{alpha} equivalent width W {sub Ly{alpha}} > 20 A have compact and/or multiple-component morphologies with r {<=} 2.5 kpc. The velocity structure of absorption lines in the galactic continuum spectra also varies as a function of morphology. Galaxies of all morphological types drive similarly strong outflows (as traced by the blue wing of interstellar absorption line features), but the outflows of larger galaxies are less highly ionized and exhibit larger optical depth at the systemic redshift that may correspond to a decreasing efficiency of feedback in evacuating gas from the galaxy. This v {approx} 0 km s{sup -1} gas is responsible both for shifting the mean absorption line redshift and attenuating W {sub Ly{alpha}} (via a longer resonant scattering path) in galaxies with larger rest-optical half-light radii. In contrast to galaxies at lower redshifts, there is no evidence for a correlation between outflow velocity and inclination, suggesting that outflows from these puffy and irregular systems may be poorly collimated. Our observations are broadly consistent with theoretical models of inside-out growth of galaxies in the young universe, in which typical z {approx} 2-3 star-forming galaxies are predominantly unstable, dispersion-dominated, systems fueled by rapid gas accretion that later form extended rotationally supported disks when stabilized

  5. THE CLUSTERING CHARACTERISTICS OF H I-SELECTED GALAXIES FROM THE 40% ALFALFA SURVEY

    SciTech Connect

    Martin, Ann M.; Giovanelli, Riccardo; Haynes, Martha P.; Guzzo, Luigi E-mail: riccardo@astro.cornell.edu E-mail: luigi.guzzo@brera.inaf.it

    2012-05-01

    The 40% Arecibo Legacy Fast ALFA survey catalog ({alpha}.40) of {approx}10,150 H I-selected galaxies is used to analyze the clustering properties of gas-rich galaxies. By employing the Landy-Szalay estimator and a full covariance analysis for the two-point galaxy-galaxy correlation function, we obtain the real-space correlation function and model it as a power law, {xi}(r) = (r/r{sub 0}){sup -{gamma}}, on scales <10 h{sup -1} Mpc. As the largest sample of blindly H I-selected galaxies to date, {alpha}.40 provides detailed understanding of the clustering of this population. We find {gamma} = 1.51 {+-} 0.09 and r{sub 0} = 3.3 + 0.3, -0.2 h{sup -1} Mpc, reinforcing the understanding that gas-rich galaxies represent the most weakly clustered galaxy population known; we also observe a departure from a pure power-law shape at intermediate scales, as predicted in {Lambda}CDM halo occupation distribution models. Furthermore, we measure the bias parameter for the {alpha}.40 galaxy sample and find that H I galaxies are severely antibiased on small scales, but only weakly antibiased on large scales. The robust measurement of the correlation function for gas-rich galaxies obtained via the {alpha}.40 sample constrains models of the distribution of H I in simulated galaxies, and will be employed to better understand the role of gas in environmentally dependent galaxy evolution.

  6. 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

  7. A MULTIBAND STUDY OF THE GALAXY POPULATIONS OF THE FIRST FOUR SUNYAEV-ZEL'DOVICH EFFECT SELECTED GALAXY CLUSTERS

    SciTech Connect

    Zenteno, A.; Mohr, J. J.; Andersson, K.; Bazin, G.; Liu, J.; Song, J.; Desai, S.; Ngeow, C.-C.; Armstrong, R.; Barkhouse, W. A.; Allam, S. S.; Buckley-Geer, E. J.; Lin, H.; Benson, B. A.; High, F. W.; Bertin, E.; Brodwin, M.; Hansen, S. M.; Lin, Y.-T.; Rest, A.

    2011-06-10

    We present first results of an examination of the optical properties of the galaxy populations in Sunyaev-Zel'dovich Effect (SZE) selected galaxy clusters. Using clusters selected by the South Pole Telescope survey and deep multiband optical data from the Blanco Cosmology Survey, we measure the radial profile, the luminosity function (LF), the blue fraction, and the halo occupation number (HON) of the galaxy populations of these four clusters with redshifts ranging from 0.3 to 1. Our goal is to understand whether there are differences among the galaxy populations of these SZE-selected clusters and previously studied clusters selected in the optical and the X-ray. The radial distributions of galaxies in the four systems are consistent with Navarro-Frenk-White profiles with a galaxy concentration of 3 to 6. We show that the characteristic luminosities in griz bands are consistent with passively evolving populations emerging from a single burst at redshift z = 3. The faint-end power-law slope of the LF is found to be on average {alpha} {approx} -1.2 in griz. HONs (to m* + 2) for these systems appear to be consistent with those based on X-ray-selected clusters. The blue fraction estimated to 0.36 L*, for the three lower redshift systems, suggests an increase with redshift, although with the current sample the uncertainties are still large. Overall, this pilot study of the first four clusters provides no evidence that the galaxy populations in these systems differ significantly from those in previously studied cluster populations selected in the X-ray or the optical.

  8. 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.

  9. H I-SELECTED GALAXIES IN THE SLOAN DIGITAL SKY SURVEY. II. THE COLORS OF GAS-RICH GALAXIES

    SciTech Connect

    West, Andrew A.; Garcia-Appadoo, Diego A.; Dalcanton, Julianne J.; Ivezic, Zeljko; Disney, Mike J.; Rockosi, Constance M.

    2009-09-15

    We utilize color information for an H I-selected sample of 195 galaxies to explore the star formation histories and physical conditions that produce the observed colors. We show that the H I selection creates a significant offset toward bluer colors that can be explained by enhanced recent bursts of star formation. There is also no obvious color bimodality, because the H I selection restricts the sample to bluer, actively star-forming systems, diminishing the importance of the red sequence. Rising star formation rates are still required to explain the colors of galaxies bluer than g - r< 0.3. We also demonstrate that the colors of the bluest galaxies in our sample are dominated by emission lines and that stellar population synthesis models alone (without emission lines) are not adequate for reproducing many of the galaxy colors. These emission lines produce large changes in the r - i colors but leave the g - r color largely unchanged. In addition, we find an increase in the dispersion of galaxy colors at low masses that may be the result of a change in the star formation process in low-mass galaxies.

  10. H I-Selected Galaxies in the Sloan Digital Sky Survey. II. The Colors of Gas-Rich Galaxies

    NASA Astrophysics Data System (ADS)

    West, Andrew A.; Garcia-Appadoo, Diego A.; Dalcanton, Julianne J.; Disney, Mike J.; Rockosi, Constance M.; Ivezić, Željko

    2009-09-01

    We utilize color information for an H I-selected sample of 195 galaxies to explore the star formation histories and physical conditions that produce the observed colors. We show that the H I selection creates a significant offset toward bluer colors that can be explained by enhanced recent bursts of star formation. There is also no obvious color bimodality, because the H I selection restricts the sample to bluer, actively star-forming systems, diminishing the importance of the red sequence. Rising star formation rates are still required to explain the colors of galaxies bluer than g - r< 0.3. We also demonstrate that the colors of the bluest galaxies in our sample are dominated by emission lines and that stellar population synthesis models alone (without emission lines) are not adequate for reproducing many of the galaxy colors. These emission lines produce large changes in the r - i colors but leave the g - r color largely unchanged. In addition, we find an increase in the dispersion of galaxy colors at low masses that may be the result of a change in the star formation process in low-mass galaxies.

  11. Beyond MACS: A Snapshot Survey of the Most Massive Clusters of Galaxies at z>0.5

    NASA Astrophysics Data System (ADS)

    Ebeling, Harald

    2014-10-01

    X-ray luminous galaxy clusters at z>0.3 play a pivotal role for a wealth of extragalactic and cosmological research topics, and SNAPshot observations of these systems are ideally suited to identify the most promising cluster targets for further, in-depth study. The power of this approach was demonstrated impressively by ACS/WFC3 SNAPshots of 81 MACS clusters at z>0.3 obtained by us in previous Cycles (28 of them in all of F606W, F814W, F110W, and F140W). Based on these data, the CLASH MCT program selected 16 out of 25 of their targets to be MACS clusters. The central role of X-ray luminous clusters in particular for gravitational-lensing work is further underlined by the fact that all but one of the six most powerful cluster lenses selected for in-depth study by the HST Frontier Fields initiative are MACS detections.We here propose to extend our spectacularly successful SNAPshot survey of the most X-ray luminous distant clusters to a redshift-mass regime that is poorly sampled by any other project. Targeting only extremely massive clusters at z>0.5 from the X-ray selected eMACS sample, the proposed program will (a) identify the most powerful gravitational telescopes at yet higher redshift for the next generation of in-depth studies of the distant Universe with HST and JWST, (b) provide constraints on the mass distribution within these extreme systems, (c) help improve our understanding of the physical nature of galaxy-galaxy and galaxy-gas interactions in cluster cores, and (d) unveil Distant Red Galaxies as well as z>6 Ly-alpha emitters as F814W dropouts.Acknowledging the broad community interest in our sample we waive our data rights for these observations.

  12. A REFINED ESTIMATE OF THE IONIZING EMISSIVITY FROM GALAXIES AT z {approx_equal} 3: SPECTROSCOPIC FOLLOW-UP IN THE SSA22a FIELD

    SciTech Connect

    Nestor, Daniel B.; Shapley, Alice E.; Kornei, Katherine A.; Steidel, Charles C.; Siana, Brian

    2013-03-01

    We investigate the contribution of star-forming galaxies to the ionizing background at z {approx} 3, building on previous work based on narrowband (NB3640) imaging in the SSA22a field. We use new Keck/LRIS spectra of Lyman break galaxies (LBGs) and narrowband-selected Ly{alpha} emitters (LAEs) to measure redshifts for 16 LBGs and 87 LAEs at z > 3.055, such that our NB3640 imaging probes the Lyman-continuum (LyC) region. When we include the existing set of spectroscopically confirmed LBGs, our total sample with z > 3.055 consists of 41 LBGs and 91 LAEs, of which 9 LBGs and 20 LAEs are detected in our NB3640 image. With our combined imaging and spectroscopic data sets, we critically investigate the origin of NB3640 emission for detected LBGs and LAEs. We remove from our samples three LBGs and three LAEs with spectroscopic evidence of contamination of their NB3640 flux by foreground galaxies and statistically model the effects of additional, unidentified foreground contaminants. The resulting contamination and LyC-detection rates, respectively, are 62% {+-} 13% and 8% {+-} 3% for our LBG sample, and 47% {+-} 10% and 12% {+-} 2% for our LAE sample. The corresponding ratios of non-ionizing UV to LyC flux density, corrected for intergalactic medium (IGM) attenuation, are 18.0{sup +34.8} {sub -7.4} for LBGs and 3.7{sup +2.5} {sub -1.1} for LAEs. We use these ratios to estimate the total contribution of star-forming galaxies to the ionizing background and the hydrogen photoionization rate in the IGM, finding values larger than, but consistent with, those measured in the Ly{alpha} forest. Finally, the measured UV to LyC flux-density ratios imply model-dependent LyC escape fractions of f {sup LyC} {sub esc} {approx} 5%-7% for our LBG sample and f {sup LyC} {sub esc} {approx} 10%-30% for our fainter LAE sample.

  13. Metal enriched gaseous halos around distant radio galaxies: Clues to feedback in galaxy formation

    SciTech Connect

    Reuland, M; van Breugel, W; de Vries, W; Dopita, A; Dey, A; Miley, G; Rottgering, H; Venemans, B; Stanford, S A; Lacy, M; Spinrad, H; Dawson, S; Stern, D; Bunker, A

    2006-08-01

    We present the results of an optical and near-IR spectroscopic study of giant nebular emission line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07 and B2 0902+34. Previous deep narrow band Ly{alpha} imaging had revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s{sup -1}, and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions >1000 km s{sup -1}. The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of {approx} 60 kpc along the radio-axis. The dynamical structures traced in the Ly{alpha} line are, in most cases, closely echoed in the Carbon and Oxygen lines. This shows that the Ly{alpha} line is produced in a highly clumped medium of small filling factor, and can therefore be used as a tracer of the dynamics of HzRGs. We conclude that these HzRGs are undergoing a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming 'red and dead' Elliptical galaxies.

  14. A Study of the Stellar Population in Selected SO Galaxies

    NASA Technical Reports Server (NTRS)

    Perez, M.; Danks, A.

    1997-01-01

    The goal of this program was to observe at least two SO galaxies with abnormal colors in the blue and clear optical signatures of dust and gas. The galaxies NGC 2217 and NGC 1808 were observed at least in one of the IUE cameras (1200-200 and 2000-3200 A) during the 13th episode, using the 4 US1 shifts assigned to this program. The galaxy NGC 2217 had been found to be part of a subgroup of SO galaxies with external gas rotating in retrograde motion with respect to the stars. This galaxy is a face-on object with indications of large amount of gas, quite rare for a SO galaxy. We observed this object on three different occasions with IUE at different positions of the large aperture (spacecraft roll angle) with respect to the nuclear region. These exposures allowed us to take full advantage of the spatial resolution of IUE by mapping nuclear and bulge region of this galaxy. We found that the data point to a marginally earlier stellar population toward the central region. The UV light as a whole is dominated by a late-type stellar population of principally G and K stars. The almost face-on view of this galaxy appears optically thick to UV light. It is conceivable that in analogy to out own Galaxy, the stellar populations weakly detected in NGC 2217, are mostly halo and late-type stars in the center with an increasing contribution of dust and early stellar populations (so far undetected) as we move outward along the faint spiral arms. This result is contrary to our initial expectation, since the counterrotating gas does not appear to be enhancing star formation in this galaxy. Even more interesting were the observations of NGC 1808; galaxy which has been classified, with a handful of other objects, both as a starburst and Seyfert galaxy. Attachment: 'The White-Dwarf Companions of 56 Persei and HR 3643.'

  15. The environment of x ray selected BL Lacs: Host galaxies and galaxy clustering

    NASA Technical Reports Server (NTRS)

    Wurtz, Ron; Stocke, John T.; Ellingson, Erica; Yee, Howard K. C.

    1993-01-01

    Using the Canada-France-Hawaii Telescope, we have imaged a complete, flux-limited sample of Einstein Medium Sensitivity Survey BL Lacertae objects in order to study the properties of BL Lac host galaxies and to use quantitative methods to determine the richness of their galaxy cluster environments.

  16. Cosmology and astrophysics from relaxed galaxy clusters - I. Sample selection

    NASA Astrophysics Data System (ADS)

    Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn; Schmidt, Robert W.; von der Linden, Anja; Urban, Ondrej

    2015-05-01

    This is the first in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here we present a new, automated method for identifying relaxed clusters based on their morphologies in X-ray imaging data. While broadly similar to others in the literature, the morphological quantities that we measure are specifically designed to provide a fair basis for comparison across a range of data quality and cluster redshifts, to be robust against missing data due to point source masks and gaps between detectors, and to avoid strong assumptions about the cosmological background and cluster masses. Based on three morphological indicators - symmetry, peakiness, and alignment - we develop the symmetry-peakiness-alignment (SPA) criterion for relaxation. This analysis was applied to a large sample of cluster observations from the Chandra and ROSAT archives. Of the 361 clusters which received the SPA treatment, 57 (16 per cent) were subsequently found to be relaxed according to our criterion. We compare our measurements to similar estimators in the literature, as well as projected ellipticity and other image measures, and comment on trends in the relaxed cluster fraction with redshift, temperature, and survey selection method. Code implementing our morphological analysis will be made available on the web (http://www.slac.stanford.edu/amantz/work/morph14/).

  17. Ultra-flat galaxies selected from RFGC catalog. II. Orbital estimates of halo masses

    NASA Astrophysics Data System (ADS)

    Karachentsev, I. D.; Karachentseva, V. E.; Kudrya, Yu. N.

    2016-04-01

    We used the Revised Flat Galaxy Catalog (RFGC) to select 817 ultra-flat (UF) edge-on disk galaxies with blue and red apparent axial ratios of ( a/ b)B > 10.0 and ( a/ b)R > 8.5. The sample covering the whole sky, except the Milky Way zone, contains 490 UF galaxies with measured radial velocities. Our inspection of the neighboring galaxies around them revealed only 30 companions with radial velocity difference of | ΔV |< 500 kms-1 inside the projected separation of R p < 250 kpc. Wherein, the wider area around the UF galaxy within R p < 750 kpc contains no other neighbors brighter than the UF galaxy itself in the same velocity span. The resulting sample galaxies mostly belong to the morphological types Sc, Scd, Sd. They have a moderate rotation velocity curve amplitude of about 120 km s-1 and a moderate K-band luminosity of about 1010 L ⊙. The median difference of radial velocities of their companions is 87 km s-1, yielding the median orbital mass estimate of about 5 × 1011 M ⊙. Excluding six probable non-isolated pairs, we obtained a typical halo-mass-to-stellar-mass of UF galaxies of about 30, what is almost the same one as in the principal spiral galaxies, like M31 and M81 in the nearest groups. We also note that ultra-flat galaxies look two times less "dusty" than other spirals of the same luminosity.

  18. On the Nature of the First Galaxies Selected at 350 Micrometers

    NASA Technical Reports Server (NTRS)

    Khan, Sophia A.; Chanial, Pierre F.; Willner, S. P.; Pearson, Chris P.; Ashby, M. L. N.; Benford, Dominic J.; Clements, David L.; Dye, Simon; Farrah, Duncan; Fazio, G. G.; Huang, J. S.; Lebouteiller, V.; Le Floc'H, Emeric; Mainetti, Gabriele; Harvey Moseley, S.; Negrello, Mattia; Serjeant, Stephen; Shafer, Richard A.; Staguhn, Johannes; Sumner, Timothy J.; Vaccari, Mattia

    2009-01-01

    We present constraints on the nature of the first galaxies selected at 350 micrometers. The sample includes galaxies discovered in the deepest blank-field survey at 350 micrometers (in the Bo6tes Deep Field) and also later serendipitous detections in the Lockman Hole. In determining multiwavelength identifications, the 350 lam position and map resolution of the second generation Submillimeter High Angular Resolution Camera are critical, especially in the cases where multiple radio sources exist and the 24 micrometer counterparts are unresolved. Spectral energy distribution templates are fitted to identified counterparts, and the sample is found to comprise IR-luminous galaxies at 1 < z < 3 predominantly powered by star formation. The first spectrum of a 350 micrometer selected galaxy provides an additional confirmation, showing prominent dust grain features typically associated with star-forming galaxies. Compared to submillimeter galaxies selected at 850 and 1100 micrometers, galaxies selected at 350 micrometers have a similar range of far-infrared color temperatures. However, no 350 micrometer selected sources are reliably detected at 850 or 1100 micrometers. Galaxies in our sample with redshifts 1 < z < 2 show a tight correlation between the far- and mid-infrared flux densities, but galaxies at higher redshifts show a large dispersion in their mid- to far-infrared colors. This implies a limit to which the mid-IR emission traces the far-IR emission in star-forming galaxies. The 350 micrometer flux densities (15 < S(sub 350) < 40 mJy) place these objects near the Herschel/SPIRE 350 micrometer confusion threshold, with the lower limit on the star formation rate density suggesting the bulk of the 350 micrometers contribution will come from less luminous infrared sources and normal galaxies. Therefore, the nature of the dominant source of the 350 micrometers background-star-forming galaxies in the epoch of peak star formation in the universe-could be more effectively

  19. The role of galaxy interaction in the SFR-M {sub *} relation: characterizing morphological properties of Herschel-selected galaxies at 0.2 < z < 1.5

    SciTech Connect

    Hung, Chao-Ling; Sanders, D. B.; Casey, C. M.; Lee, N.; Barnes, J. E.; Koss, M.; Larson, K. L.; Lockhart, K.; Man, A. W. S.; Mann, A. W.; Capak, P.; Kartaltepe, J. S.; Le Floc'h, E.; Riguccini, L.; Scoville, N.; Symeonidis, M.

    2013-12-01

    Galaxy interactions/mergers have been shown to dominate the population of IR-luminous galaxies (L {sub IR} ≳ 10{sup 11.6} L {sub ☉}) in the local universe (z ≲ 0.25). Recent studies based on the relation between galaxies' star formation rates and stellar mass (the SFR-M {sub *} relation or the {sup g}alaxy main sequence{sup )} have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy main sequence. Since the typical SFR at a given M {sub *} increases with redshift, the existence of the galaxy main sequence implies that massive, IR-luminous galaxies at high z may not necessarily be driven by galaxy interactions. We examine the role of galaxy interactions in the SFR-M {sub *} relation by carrying out a morphological analysis of 2084 Herschel-selected galaxies at 0.2 < z < 1.5 in the COSMOS field. Using a detailed visual classification scheme, we show that the fraction of 'disk galaxies' decreases and the fraction of 'irregular' galaxies increases systematically with increasing L {sub IR} out to z ≲ 1.5 and z ≲ 1.0, respectively. At L {sub IR} >10{sup 11.5} L {sub ☉}, ≳ 50% of the objects show evident features of strongly interacting/merger systems, where this percentage is similar to the studies of local IR-luminous galaxies. The fraction of interacting/merger systems also systematically increases with the deviation from the SFR-M {sub *} relation, supporting the view that galaxies falling above the main sequence are more dominated by mergers than the main-sequence galaxies. Meanwhile, we find that ≳ 18% of massive IR-luminous 'main-sequence galaxies' are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model.

  20. A LYMAN BREAK GALAXY IN THE EPOCH OF REIONIZATION FROM HUBBLE SPACE TELESCOPE GRISM SPECTROSCOPY

    SciTech Connect

    Rhoads, James E.; Malhotra, Sangeeta; Cohen, Seth; Zheng Zhenya; Stern, Daniel; Dickinson, Mark; Pirzkal, Norbert; Grogin, Norman; Koekemoer, Anton; Peth, Michael A.; Spinrad, Hyron; Reddy, Naveen; Hathi, Nimish; Budavari, Tamas; Ferreras, Ignacio; Gardner, Jonathan P.; Gronwall, Caryl; Haiman, Zoltan; Kuemmel, Martin; Meurer, Gerhardt; and others

    2013-08-10

    We present observations of a luminous galaxy at z = 6.573-the end of the reionization epoch-which has been spectroscopically confirmed twice. The first spectroscopic confirmation comes from slitless Hubble Space Telescope Advanced Camera for Surveys grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically), which show a dramatic continuum break in the spectrum at rest frame 1216 A. The second confirmation is done with Keck + DEIMOS. The continuum is not clearly detected with ground-based spectra, but high wavelength resolution enables the Ly{alpha} emission line profile to be determined. We compare the line profile to composite line profiles at z = 4.5. The Ly{alpha} line profile shows no signature of a damping wing attenuation, confirming that the intergalactic gas is ionized at z = 6.57. Spectra of Lyman breaks at yet higher redshifts will be possible using comparably deep observations with IR-sensitive grisms, even at redshifts where Ly{alpha} is too attenuated by the neutral intergalactic medium to be detectable using traditional spectroscopy from the ground.

  1. H I-SELECTED GALAXIES AS A PROBE OF QUASAR ABSORPTION SYSTEMS

    SciTech Connect

    Okoshi, Katsuya; Nagashima, Masahiro; Gouda, Naoteru; Minowa, Yousuke

    2010-02-20

    We investigate the properties of H I-rich galaxies detected in blind radio surveys within the hierarchical structure formation scenario using a semianalytic model of galaxy formation. By drawing a detailed comparison between the properties of H I-selected galaxies and H I absorption systems, we argue a link between the local galaxy population and quasar absorption systems, particularly for damped Lyalpha absorption (DLA) systems and sub-DLA systems. First, we evaluate how many H I-selected galaxies exhibit H I column densities as high as those of DLA systems. We find that H I-selected galaxies with H I masses M{sub H{sub I}} {approx}> 10{sup 8} M{sub sun} have gaseous disks that produce H I column densities comparable to those of DLA systems. We conclude that DLA galaxies where the H I column densities are as high as those of DLA systems, contribute significantly to the population of H I-selected galaxies at M{sub H{sub I}} {approx}> 10{sup 8} M{sub sun}. Second, we find that star formation rates (SFRs) correlate tightly with H I masses (M{sub H{sub I}}) rather than B- (and J-) band luminosities: SFR {proportional_to} M {sup alpha}{sub H{sub I}}, alpha = 1.25-1.40 for 10{sup 6} <= M{sub H{sub I}}/M{sub sun} <= 10{sup 11}. In the low-mass range M{sub H{sub I}} {approx}< 10{sup 8} M{sub sun}, sub-DLA galaxies replace DLA galaxies as the dominant population. The number fraction of sub-DLA galaxies relative to galaxies reaches 40%-60% for M{sub H{sub I}} {approx} 10{sup 8} M{sub sun} and 30%-80% for M{sub H{sub I}} {approx} 10{sup 7} M{sub sun}. The H I-selected galaxies at M{sub H{sub I}} {approx} 10{sup 7} M{sub sun} are a strong probe of sub-DLA systems that place stringent constraints on galaxy formation and evolution.

  2. Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1

    NASA Technical Reports Server (NTRS)

    VanDerWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D.; Ferguson, H. C.; Scarlata, C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Kocevski, D. D.; Lai, K.; Grogin, N. A.; Rodney, S. A.; Lee, K.-S.; Guo, Y.

    2011-01-01

    We identify an abundant population of extreme emission line galaxies at redshift z=1.6 - 1.8 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared, broad-band fluxes. Supported by spectroscopic confirmation of strong [OIII] emission lines - with equivalent widths approximately 1000A - in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are dwarf galaxies with approximately 10(exp 8) solar mass in stellar mass, undergoing an enormous star-burst phase with M*/M* of only approximately 10 Myr. The star formation activity and the co-moving number density (3.7 x 10(exp -4) Mpc(exp -3)) imply that strong, short-lived bursts play a significant, perhaps even dominant role in the formation and evolution of dwarf galaxies at z greater than 1. The observed star formation activity can produce in less than 5 Gyr the same amount of stellar mass density as is presently contained in dwarf galaxies. Therefore, our observations provide a strong indication that the stellar populations of present-day dwarf galaxies formed mainly in strong, short-lived bursts, mostly at z greater than 1.

  3. Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1

    NASA Technical Reports Server (NTRS)

    vanderWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D. C.; Ferguson, H. C.; Scarlata, C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Dickinson, M.; Jahnke, K.; Salmon, B. W.; deMello, D. F.; Kkocevski, D. D.; Lai, K.; Grogin, N. A.; Rodney, S. A.; Guo, Yicheng

    2012-01-01

    We identify an abundant population of extreme emission line galaxies (EELGs) at redshift z approx. 1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broad-band magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission lines . with rest-frame equivalent widths approx. 1000A in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with approx.10(exp 8) Solar Mass in stellar mass, undergoing an enormous starburst phase with M*/M* of only approx. 15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the co-moving number density (3.7x10(exp -4) Mpc(sup -3) can produce in approx.4 Gyr much of the stellar mass density that is presently contained in 10(exp 8) - 10(exp 9) Solar Mass dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z > 1.

  4. 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.

  5. Host Galaxy Properties of the Swift BAT Ultra Hard X-Ray Selected AGN

    NASA Technical Reports Server (NTRS)

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa M.; Baumgartner, Wayne; Tueller, Jack; Gehrels, Neil; Valencic, Lynne

    2011-01-01

    We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift Burst Alert Telescope (BAT) sample. The BAT AGN host galaxies have intermediate optical colors (u -- r and g -- r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGN in massive galaxies (log Stellar Mass >10.5) have a 5 to 10 times higher rate of spiral morphologies than in SDSS AGN or inactive galaxies. We also see enhanced far-IR emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGN are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGN have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] Lambda 5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGN in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as whole. In agreement with the Unified Model of AGN, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGN suggest that host galaxy morphology is related to the activation and fueling of local AGN.

  6. HOST GALAXY PROPERTIES OF THE SWIFT BAT ULTRA HARD X-RAY SELECTED ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa M.; Baumgartner, Wayne; Tueller, Jack; Gehrels, Neil; Valencic, Lynne

    2011-10-01

    We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) active galactic nucleus (AGN) with host galaxy optical data to date, with 185 nearby (z < 0.05), moderate luminosity AGNs from the Swift BAT sample. The BAT AGN host galaxies have intermediate optical colors (u - r and g - r) that are bluer than a comparison sample of inactive galaxies and optically selected AGNs from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGNs are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGNs in massive galaxies (log M{sub *} >10.5) have a 5-10 times higher rate of spiral morphologies than in SDSS AGNs or inactive galaxies. We also see enhanced far-infrared emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGNs are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGNs have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] {lambda}5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGNs in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as a whole. In agreement with the unified model of AGNs, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGNs suggest that host galaxy morphology is related to the activation and fueling of local AGN.

  7. The effect of surface brightness dimming in the selection of high-z galaxies

    SciTech Connect

    Calvi, V.; Stiavelli, M.; Bradley, L.; Pizzella, A.; Kim, S.

    2014-12-01

    Cosmological surface brightness (SB) dimming of the form (1 + z){sup –4} affects all sources. The strong dependence of SB dimming on redshift z suggests the presence of a selection bias when searching for high-z galaxies, i.e., we tend to detect only those galaxies with a high SB. However, unresolved knots of emission are not affected by SB dimming, thus providing a way to test the clumpiness of high-z galaxies. Our strategy relies on the comparison of the total flux detected for the same source in surveys characterized by different depth. For all galaxies, deeper images permit the better investigation of low-SB features. Cosmological SB dimming makes these low-SB features hard to detect when going to higher and higher redshifts. We used the GOODS and HUDF Hubble Space Telescope legacy data sets to study the effect of SB dimming on low-SB features of high-z galaxies and compare it to the prediction for smooth sources. We selected a sample of Lyman-break galaxies at z ∼ 4 (i.e., B {sub 435}-band dropouts) detected in all of the data sets and found no significant trend when comparing the total magnitudes measured from images with different depth. Through Monte Carlo simulations we derived the expected trend for galaxies with different SB profiles. The comparison to the data hints at a compact distribution for most of the rest-frame ultraviolet light emitted from high-z galaxies.

  8. The Effect of Surface Brightness Dimming in the Selection of High-z Galaxies

    NASA Astrophysics Data System (ADS)

    Calvi, V.; Stiavelli, M.; Bradley, L.; Pizzella, A.; Kim, S.

    2014-12-01

    Cosmological surface brightness (SB) dimming of the form (1 + z)-4 affects all sources. The strong dependence of SB dimming on redshift z suggests the presence of a selection bias when searching for high-z galaxies, i.e., we tend to detect only those galaxies with a high SB. However, unresolved knots of emission are not affected by SB dimming, thus providing a way to test the clumpiness of high-z galaxies. Our strategy relies on the comparison of the total flux detected for the same source in surveys characterized by different depth. For all galaxies, deeper images permit the better investigation of low-SB features. Cosmological SB dimming makes these low-SB features hard to detect when going to higher and higher redshifts. We used the GOODS and HUDF Hubble Space Telescope legacy data sets to study the effect of SB dimming on low-SB features of high-z galaxies and compare it to the prediction for smooth sources. We selected a sample of Lyman-break galaxies at z ~ 4 (i.e., B 435-band dropouts) detected in all of the data sets and found no significant trend when comparing the total magnitudes measured from images with different depth. Through Monte Carlo simulations we derived the expected trend for galaxies with different SB profiles. The comparison to the data hints at a compact distribution for most of the rest-frame ultraviolet light emitted from high-z galaxies.

  9. Far-infrared properties of optically-selected quasars and Seyfert galaxies

    NASA Technical Reports Server (NTRS)

    Edelson, R. A.; Malkan, M. A.

    1987-01-01

    Pointed IRAS observations and ground based observations are used to determine the infrared properties of optically selected galaxies and quasars. The use of complete, unbiased, optically selected samples means that statistical tests can be applied to probe the underlying properties of active galactic nuclei (AGNs). The near infrared to millimeter spectral energy distributions (SEDs) were studied of the CfA Seyfert galaxies, a well defined, unbiased sample of 25 Type 1 and 23 Type 2 Seyfert galaxies selected by optical spectroscopy. Data given show strong trends in the infrared SEDs. Strong evidence is also given that the infrared spectra of Seyfert 2 galaxies are dominated by thermal emission from warm dust, while nonthermal emission is more important in the spectra of quasars and luminous Seyfert 1 nuclei.

  10. CALIFA: a diameter-selected sample for an integral field spectroscopy galaxy survey

    NASA Astrophysics Data System (ADS)

    Walcher, C. J.; Wisotzki, L.; Bekeraité, S.; Husemann, B.; Iglesias-Páramo, J.; Backsmann, N.; Barrera Ballesteros, J.; Catalán-Torrecilla, C.; Cortijo, C.; del Olmo, A.; Garcia Lorenzo, B.; Falcón-Barroso, J.; Jilkova, L.; Kalinova, V.; Mast, D.; Marino, R. A.; Méndez-Abreu, J.; Pasquali, A.; Sánchez, S. F.; Trager, S.; Zibetti, S.; Aguerri, J. A. L.; Alves, J.; Bland-Hawthorn, J.; Boselli, A.; Castillo Morales, A.; Cid Fernandes, R.; Flores, H.; Galbany, L.; Gallazzi, A.; García-Benito, R.; Gil de Paz, A.; González-Delgado, R. M.; Jahnke, K.; Jungwiert, B.; Kehrig, C.; Lyubenova, M.; Márquez Perez, I.; Masegosa, J.; Monreal Ibero, A.; Pérez, E.; Quirrenbach, A.; Rosales-Ortega, F. F.; Roth, M. M.; Sanchez-Blazquez, P.; Spekkens, K.; Tundo, E.; van de Ven, G.; Verheijen, M. A. W.; Vilchez, J. V.; Ziegler, B.

    2014-09-01

    We describe and discuss the selection procedure and statistical properties of the galaxy sample used by the Calar Alto Legacy Integral Field Area (CALIFA) survey, a public legacy survey of 600 galaxies using integral field spectroscopy. The CALIFA "mother sample" was selected from the Sloan Digital Sky Survey (SDSS) DR7 photometric catalogue to include all galaxies with an r-band isophotal major axis between 45'' and 79.2'' and with a redshift 0.005 < z < 0.03. The mother sample contains 939 objects, 600 of which will be observed in the course of the CALIFA survey. The selection of targets for observations is based solely on visibility and thus keeps the statistical properties of the mother sample. By comparison with a large set of SDSS galaxies, we find that the CALIFA sample is representative of galaxies over a luminosity range of -19 > Mr > -23.1 and over a stellar mass range between 109.7 and 1011.4 M⊙. In particular, within these ranges, the diameter selection does not lead to any significant bias against - or in favour of - intrinsically large or small galaxies. Only below luminosities of Mr = -19 (or stellar masses <109.7 M⊙) is there a prevalence of galaxies with larger isophotal sizes, especially of nearly edge-on late-type galaxies, but such galaxies form <10% of the full sample. We estimate volume-corrected distribution functions in luminosities and sizes and show that these are statistically fully compatible with estimates from the full SDSS when accounting for large-scale structure. For full characterization of the sample, we also present a number of value-added quantities determined for the galaxies in the CALIFA sample. These include consistent multi-band photometry based on growth curve analyses; stellar masses; distances and quantities derived from these; morphological classifications; and an overview of available multi-wavelength photometric measurements. We also explore different ways of characterizing the environments of CALIFA galaxies

  11. Automated Selection of Metal-Poor Stars in the Galaxy

    NASA Astrophysics Data System (ADS)

    Rhee, Jaehyon

    2000-08-01

    In this thesis I have developed algorithms for the efficient reduction and analysis of a large set of objective-prism data, and for the reliable selection of extremely metal-poor candidate stars in the Galaxy. Automated computer scans of the 308 photographic plates in the HK objective-prism / interference-filter survey of Beers and colleagues have been carried out with the Automatic Plate Measuring (APM) machine in Cambridge, England. Highly automated software tools have been developed in order to identify useful spectra and remove unusable spectra, to locate the positions of the Ca II H (3969 Å) and K (3933 Å) absorption lines, and to construct approximate continua. Equivalent widths of the Ca II H and K lines were then measured directly from these reduced spectra. A subset of 294,039 spectra from 87 of the HK survey plates (located within approximately 30 degrees of the South Galactic Pole) were extracted. Of these, 221,670 (75.4%) proved to be useful for subsequent analysis. I have explored new methodology, making use of an Artificial Neural Network (ANN) analysis approach, in order to select extremely metal-poor star candidates with high efficiency. The ANNs were trained to predict metallicity, [Fe/H], and to classify stars into 6 groups separated by temperature and metal abundance, based on two accurately measured parameters -- the de-reddened broadband (B-V)0 color for known HK survey stars with available photometric information, and the equivalent width of the Ca II K line in an 18 Å band, the K18 index, as measured from follow-up medium-resolution spectroscopy taken during the course of the HK survey. When provided with accurate input data, the trained networks were able to estimate [Fe/H] and to determine the class with high accuracy (with a robust estimated one-sigma scatter of SBI = 0.13 dex, and an overall correction rate of 91%). The ANN approach was then used in order to recover information on the K18 index and (B-V)0 color directly from the APM

  12. Selection and Physical Properties of High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Fang, G. W.

    2014-09-01

    Extremely Red Objects (EROs) and BzKs continue to attract considerable interest. It has been suggested that they may be the direct progenitors of present-day massive E/S0 galaxies, and can provide crucial constraints on the current galaxy formation and evolution models. Therefore, the key question is to measure the relative fraction of OGs (old galaxies) and DGs (young, and dusty starburst galaxies) in the sample of EROs. Many groups have been currently investigating the fractions of these two ERO populations using a variety of observational approaches, but the fraction of OGs and DGs from different surveys is different. In the meantime, a number of observations suggest that the epoch of z˜2 also plays an important role in galaxy formation and evolution for various reasons: the cosmic star formation rate density (SFRD) begins to drop at z˜2 from a flat plateau at higher redshifts; the morphological type mix of field galaxies changes remarkably at z˜2; the number density of QSOs has a peak at z˜2; and about 50% to 70% of the stellar mass assembly of galaxies took place in the redshift range 1galaxies at z˜2 in the AEGIS field, and (3) the mid-infrared spectroscopy and multi-wavelength study of ultraluminous infrared galaxies (ULIRGs) at z˜2 in the AEGIS field. Chapter 1 gives a brief review on the research progresses of EROs at z˜1, BzKs at z˜2, and ULIRGs at z˜2, respectively. In Chapter 2 we present a quantitative study of the classification of EROs in the UDF and COSMOS field. Our sample includes 5264 (COSMOS, K_{Vega} ≤19.2) and 24 EROs (UDF, K_{Vega}≤22.0) with (i-K)_{AB}≥2.45. Using the fitting method of spectral energy distribution (SED), [3.6]-[8.0] color, and the nonparametric measures of galaxy morphology, we classify EROs into two classes: DGs and OGs. We find

  13. SHELS: OPTICAL SPECTRAL PROPERTIES OF WISE 22 {mu}m SELECTED GALAXIES

    SciTech Connect

    Hwang, Ho Seong; Geller, Margaret J.; Kurtz, Michael J.; Fabricant, Daniel G.; Dell'Antonio, Ian P. E-mail: mgeller@cfa.harvard.edu E-mail: dfabricant@cfa.harvard.edu

    2012-10-10

    We use a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), covering a 4 deg{sup 2} region of a deep imaging survey, the Deep Lens Survey (DLS), to study the optical spectral properties of Wide-field Infrared Survey Explorer (WISE) 22 {mu}m selected galaxies. Among 507 WISE 22 {mu}m selected sources with (S/N){sub 22{mu}m} {>=} 3 ( Almost-Equal-To S{sub 22{mu}m} {approx}> 2.5 mJy), we identify the optical counterparts of 481 sources ({approx}98%) at R < 25.2 in the very deep, DLS R-band source catalog. Among them, 337 galaxies at R < 21 have SHELS spectroscopic data. Most of these objects are at z < 0.8. The infrared (IR) luminosities are in the range 4.5 Multiplication-Sign 10{sup 8}(L{sub Sun }) {approx}< L{sub IR} {approx}< 5.4 Multiplication-Sign 10{sup 12}(L{sub Sun }). Most 22 {mu}m selected galaxies are dusty star-forming galaxies with a small (<1.5) 4000 A break. The stacked spectra of the 22 {mu}m selected galaxies binned in IR luminosity show that the strength of the [O III] line relative to H{beta} grows with increasing IR luminosity. The optical spectra of the 22 {mu}m selected galaxies also show that there are some ({approx}2.8%) unusual galaxies with very strong [Ne III] {lambda}3869, 3968 emission lines that require hard ionizing radiation such as active galactic nuclei (AGNs) or extremely young massive stars. The specific star formation rates (sSFRs) derived from the 3.6 and 22 {mu}m flux densities are enhanced if the 22 {mu}m selected galaxies have close late-type neighbors. The sSFR distribution of the 22 {mu}m selected galaxies containing AGNs is similar to the distribution for star-forming galaxies without AGNs. We identify 48 dust-obscured galaxy candidates with large ({approx}> 1000) mid-IR to optical flux density ratio. The combination of deep photometric and spectroscopic data with WISE data suggests that WISE can probe the universe to z {approx} 2.

  14. Clustering of the AKARI NEP deep field 24 μm selected galaxies

    NASA Astrophysics Data System (ADS)

    Solarz, A.; Pollo, A.; Takeuchi, T. T.; Małek, K.; Matsuhara, H.; White, G. J.; Pȩpiak, A.; Goto, T.; Wada, T.; Oyabu, S.; Takagi, T.; Ohyama, Y.; Pearson, C. P.; Hanami, H.; Ishigaki, T.; Malkan, M.

    2015-10-01

    Aims: We present a method of selection of 24 μm galaxies from the AKARI north ecliptic pole (NEP) deep field down to 150 μJy and measurements of their two-point correlation function. We aim to associate various 24 μm selected galaxy populations with present day galaxies and to investigate the impact of their environment on the direction of their subsequent evolution. Methods: We discuss using of Support Vector Machines (SVM) algorithm applied to infrared photometric data to perform star-galaxy separation, in which we achieve an accuracy higher than 80%. The photometric redshift information, obtained through the CIGALE code, is used to explore the redshift dependence of the correlation function parameter (r0) as well as the linear bias evolution. This parameter relates galaxy distribution to the one of the underlying dark matter. We connect the investigated sources to their potential local descendants through a simplified model of the clustering evolution without interactions. Results: We observe two different populations of star-forming galaxies, at zmed ~ 0.25, zmed ~ 0.9. Measurements of total infrared luminosities (LTIR) show that the sample at zmed ~ 0.25 is composed mostly of local star-forming galaxies, while the sample at zmed ~ 0.9 is composed of luminous infrared galaxies (LIRGs) with LTIR ~ 1011.62 L⊙. We find that dark halo mass is not necessarily correlated with the LTIR: for subsamples with LTIR = 1011.15 L⊙ at zmed ~ 0.7 we observe a higher clustering length (r0 = 6.21 ± 0.78[ h-1Mpc ]) than for a subsample with mean LTIR = 1011.84 L⊙ at zmed ~ 1.1 (r0 = 5.86 ± 0.69h-1Mpc). We find that galaxies at zmed ~ 0.9 can be ancestors of present day L∗ early type galaxies, which exhibit a very high r0 ~ 8h-1 Mpc.

  15. Ultra-flat galaxies selected from RFGC catalog. I. The sample properties

    NASA Astrophysics Data System (ADS)

    Karachentseva, V. E.; Kudrya, Yu. N.; Karachentsev, I. D.; Makarov, D. I.; Melnyk, O. V.

    2016-01-01

    We used the Revised Flat Galaxy Catalog (RFGC) to create a sample of ultra-flat galaxies (UFG) covering the whole northern and southern sky apart from theMilkyWay zone. It contains 817 spiral galaxies seen edge-on, selected into theUFG sample according to their apparent axial ratios ( a/b) B ≥ 10.0 and ( a/b) R ≥ 8.53 in the blue and red bands, respectively. Within this basic sample we fixed an exemplary sample of 441 UFG galaxies having the radial velocities of V LG < 10000 km s-1, Galactic latitude of | b |> 10° and the blue angular diameter of a B > 1.'0. According to the Schmidt test the exemplary sample of 441 galaxies is characterized by about (80-90)% completeness, what is quite enough to study different properties of the ultra-flat galaxies. We found that more than 3/4 of UFGs have the morphological types within the narrow range of T = 7± 1, i.e. the thinnest stellar disks occur among the Scd, Sd, and Sdm types. The average surface brightness of UFG galaxies tends to diminish towards the flattest bulge-less galaxies. Regularly shaped disks without signs of asymmetrymake up about 2/3 both among all the RFGC galaxies, and the UFG sample objects. About 60% of ultra-flat galaxies can be referred to dynamically isolated objects, while 30% of them probably belong to the scattered associations (filaments, walls), and only about 10% of them are dynamically dominating galaxies with respect to their neighbours.

  16. A SPITZER-SELECTED GALAXY CLUSTER AT z = 1.62

    SciTech Connect

    Papovich, C.; Finkelstein, K. D.; Finkelstein, S. L.; Tran, K.-V.; Momcheva, I.; McCarthy, P.; Willmer, C. N. A.; Rieke, M.; Sivanandam, S.; Brodwin, M.; Dunlop, J. S.; McLure, R. J.; Farrah, D.; Khan, S. A.; Lotz, J.; Rudnick, G.; Pacaud, F.; Pierre, M.

    2010-06-20

    We report the discovery of a galaxy cluster at z = 1.62 located in the Spitzer Wide-Area Infrared Extragalactic survey XMM-LSS field. This structure was selected solely as an overdensity of galaxies with red Spitzer/Infrared Array Camera colors, satisfying ([3.6] - [4.5]){sub AB}> - 0.1 mag. Photometric redshifts derived from the Subaru XMM Deep Survey (BViz bands), the UKIRT Infrared Deep Survey-Ultra-Deep Survey (UKIDSS-UDS, JK bands), and from the Spitzer Public UDS survey (3.6-8.0 {mu}m) show that this cluster corresponds to a surface density of galaxies at z {approx} 1.6 that is >20{sigma} above the mean at this redshift. We obtained optical spectroscopic observations of galaxies in the cluster region using IMACS on the Magellan telescope. We measured redshifts for seven galaxies in the range z = 1.62-1.63 within 2.8 arcmin (<1.4 Mpc) of the astrometric center of the cluster. A posteriori analysis of the XMM data in this field reveal a weak (4{sigma}) detection in the [0.5-2 keV] band compatible with the expected thermal emission from such a cluster. The color-magnitude diagram of the galaxies in this cluster shows a prominent red sequence, dominated by a population of red galaxies with (z - J)>1.7 mag. The photometric-redshift probability distributions for the red galaxies are strongly peaked at z = 1.62, coincident with the spectroscopically confirmed galaxies. The rest-frame (U - B) color and scatter of galaxies on the red sequence are consistent with a mean luminosity-weighted age of 1.2 {+-} 0.1 Gyr, yielding a formation redshift z-bar{sub f}=2.35{+-}0.10, and corresponding to the last significant star formation period in these galaxies.

  17. Selections from 2015: Discovery of Diffuse Galaxies in the Coma Cluster

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-12-01

    Editors Note:In these last two weeks of 2015, well be looking at a few selections from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma ClusterPublished January 2015Main takeaway:Using the Dragonfly Telephoto Array, a team led by Pieter van Dokkum (Yale University) discovered 47 ultra-diffuse galaxies in the Coma galaxy cluster. These galaxies are very large, with half-light (effective) radii of 1.54.6 kpc, similar to that of the Milky Ways disk. But their stellar masses are a factor of 1000 lower than the Milky Ways, and theyre accordingly much dimmer.Plot of the effective radius versus the central surface brightness for the ultra-diffuse Coma cluster galaxies (red markers). These galaxies are similar in size to the Milky Ways disk (blue), but significantly dimmer. [Van Dokkum et al. 2015]Why its interesting:These galaxies make up an odd population. Why are their stellar masses so low? The authors posit that these objects may be failed galaxies that lost their gas after having formed their first generation of stars. Adding to the intrigue, the authors find that in order for these galaxies to hold themselves together at their current distance from the cluster core, they must have a whopping dark-matter fraction of 98%.About the discovery:These ultra-diffuse galaxies were actually discovered entirely by accident. Van Dokkum and collaborators observed the Coma cluster in a project to measure properties of the intra-cluster light and look for streams and tidal features. Surprisingly, their images revealed these faint, uncataloged galaxies.CitationPieter G. van Dokkum et al 2015 ApJ 798 L45. doi:10.1088/2041-8205/798/2/L45

  18. The featureless continua and hydrogen lines of Seyfert 2 galaxies

    NASA Technical Reports Server (NTRS)

    Kinney, A. L.; Antonucci, R. R. J.; Ward, M. J.; Wilson, A. S.; Whittle, M.

    1991-01-01

    Optical and ultraviolet spectra taken in similar sized large apertures for 15 Seyfert 2 galaxies are presented. Measurements of emission-line strengths of Ly-alpha, H-alpha, and H-beta are used together with measurements of the ultraviolet slopes to estimate the ratio of recombination photons to ionizing photons. The photon ratios indicate that the ionizing continuum is being emitted anisotropically for at least six of the eight objects with UV slope measurements. The median value of the UV slope is indistinguishable from the UV slope of Seyfert 1 galaxies. This result suggests that in the occultation/reflection picture of Seyfert nuclei, the reflecting particles are free electrons and not dust. Previous observations of variability in Mrk 477 are verified, and it is shown that this galaxy exhibits characteristics of both Seyfert 1 and Seyfert 2 galaxies.

  19. METALLICITIES OF EMISSION-LINE GALAXIES FROM HST ACS PEARS AND HST WFC3 ERS GRISM SPECTROSCOPY AT 0.6 < z < 2.4

    SciTech Connect

    Xia Lifang; Malhotra, Sangeeta; Rhoads, James; Cohen, Seth; Windhorst, Rogier A.; Pirzkal, Nor; Straughn, Amber; Finkelstein, Steven; Kuntschner, Harald; Kuemmel, Martin; Walsh, Jeremy; O'Connell, Robert

    2012-07-15

    Galaxies selected on the basis of their emission-line strength show low metallicities, regardless of their redshifts. We conclude this from a sample of faint galaxies at redshifts between 0.6 < z < 2.4, selected by their prominent emission lines in low-resolution grism spectra in the optical with the Advanced Camera for Surveys on the Hubble Space Telescope and in the near-infrared using Wide-Field Camera 3. Using a sample of 11 emission-line galaxies at 0.6 < z < 2.4 with luminosities of -22 {approx}< M{sub B} {approx}< -19 which have [O II], H{beta}, and [O III] line flux measurements from the combination of two grism spectral surveys, we use the R23 method to derive the gas-phase oxygen abundances: 7.5 < 12 + log (O/H) < 8.5. The galaxy stellar masses are derived using Bayesian-based Markov Chain Monte Carlo ({pi}MC{sup 2}) fitting of their spectral energy distribution, and span the mass range 8.1 < log (M{sub *}/M{sub Sun} ) < 10.1. These galaxies show mass-metallicity (M-Z) and luminosity-metallicity (L-Z) relations, which are offset by -0.6 dex in metallicity at given absolute magnitude and stellar mass relative to the local Sloan Digital Sky Survey galaxies, as well as continuum-selected DEEP2 samples at similar redshifts. The emission-line-selected galaxies most resemble the local 'green peas' galaxies and Ly{alpha} galaxies at z {approx_equal} 0.3 and z {approx_equal} 2.3 in the M-Z and L-Z relations and their morphologies. The G - M{sub 20} morphology analysis shows that 10 out of 11 show disturbed morphology, even as the star-forming regions are compact. These galaxies may be intrinsically metal poor, being at early stages of formation, or the low metallicities may be due to gas infall and accretion due to mergers.

  20. THE DWARF STARBURST HOST GALAXY OF A TYPE Ia SUPERNOVA AT z = 1.55 FROM CANDELS

    SciTech Connect

    Frederiksen, Teddy F.; Hjorth, Jens; Maund, Justyn R.; Rodney, Steven A.; Riess, Adam G.; Dahlen, Tomas; Mobasher, Bahram

    2012-12-01

    We present VLT/X-shooter observations of a high-redshift, Type Ia supernova (SN Ia) host galaxy, discovered with HST/WFC3 as part of the CANDELS Supernova project. The galaxy exhibits strong emission lines of Ly{alpha}, [O II], H{beta}, [O III], and H{alpha} at z = 1.54992{sup +0.00008} {sub -0.00004}. From the emission-line fluxes and spectral energy distribution fitting of broadband photometry we rule out activity from an active galactic nucleus and characterize the host galaxy as a young, low-mass, metal-poor, starburst galaxy with low intrinsic extinction and high Ly{alpha} escape fraction. The host galaxy stands out in terms of the star formation, stellar mass, and metallicity compared to its lower redshift counterparts, mainly because of its high specific star formation rate. If valid for a larger sample of high-redshift SN Ia host galaxies, such changes in the host galaxy properties with redshift are of interest because of the potential impact on the use of SN Ia as standard candles in cosmology.

  1. THE ABUNDANCE OF STAR-FORMING GALAXIES IN THE REDSHIFT RANGE 8.5-12: NEW RESULTS FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN

    SciTech Connect

    Ellis, Richard S.; Schenker, Matthew A.; McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Rogers, Alexander B.; Curtis-Lake, Emma; Cirasuolo, Michele; Robertson, Brant E.; Schneider, Evan; Stark, Daniel P.; Ono, Yoshiaki; Ouchi, Masami; Koekemoer, Anton; Charlot, Stephane; Furlanetto, Steven R.

    2013-01-20

    We present the results of the deepest search to date for star-forming galaxies beyond a redshift z {approx_equal} 8.5 utilizing a new sequence of near-infrared Wide-Field Camera 3 (WFC3/IR) images of the Hubble Ultra Deep Field (UDF). This 'UDF12' campaign completed in 2012 September doubles the earlier exposures with WFC3/IR in this field and quadruples the exposure in the key F105W filter used to locate such distant galaxies. Combined with additional imaging in the F140W filter, the fidelity of high-redshift candidates is greatly improved. Using spectral energy distribution fitting techniques on objects selected from a deep multi-band near-infrared stack, we find seven promising z > 8.5 candidates. As none of the previously claimed UDF candidates with 8.5 < z < 10 are confirmed by our deeper multi-band imaging, our campaign has transformed the measured abundance of galaxies in this redshift range. Although we recover the candidate UDFj-39546284 (previously proposed at z = 10.3), it is undetected in the newly added F140W image, implying that it lies at z = 11.9 or is an intense emission line galaxy at z {approx_equal} 2.4. Although no physically plausible model can explain the required line intensity given the lack of Ly{alpha} or broadband UV signal, without an infrared spectrum we cannot rule out an exotic interloper. Regardless, our robust z {approx_equal} 8.5-10 sample demonstrates a luminosity density that continues the smooth decline observed over 6 < z < 8. Such continuity has important implications for models of cosmic reionization and future searches for z >10 galaxies with James Webb Space Telescope.

  2. Radio observations of a hard X-ray selected sample of active galaxies

    NASA Technical Reports Server (NTRS)

    Unger, S. W.; Lawrence, A.; Wilson, A. S.; Elvis, M.; Wright, A. E.

    1987-01-01

    Radio observations of a hard X-ray selected sample of active galaxies obtained with the VLA and Parkes radio telescopes are discussed, and the ratio of the radio to X-ray flux density is used to determine the degree of radio-loudness of the galaxies. A continuous distribution of the degree of radio loudness is found amongst the sample galaxies, and no evidence for distinct radio-quiet and radio-loud populations is noted. The X-ray and radio luminosity is shown to be nonlinearly correlated, with the radio-loud objects all having high X-ray luminosity.

  3. Galaxy formation and the origin of the ionizing flux at large redshift

    NASA Technical Reports Server (NTRS)

    Songaila, A.; Cowie, L. L.; Lilly, S. J.

    1990-01-01

    The absence of any continuous Ly-alpha opacity from the intergalactic medium at z = 3-4.5 can be understood if a significant population of star-forming galaxies is present at these redshifts. It is shown that such galaxies can be present within the galaxy populations at B = 22 to 27. The expected ionization produced during galaxy formation is analyzed in terms of highly model-independent metal production arguments and it is concluded that (if such galaxies are dust-free and transparent to ionizing photons) then at least 4(H0/50 km/s Mpc)-cubed percent of galaxy formation would have to have occurred in this redshift range.

  4. 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.

  5. CIII] Emission in z=5.7 Galaxies: A Pathfinder for Galaxy Spectroscopy in the Reionization Era

    NASA Astrophysics Data System (ADS)

    Fan, Xiaohui

    2014-10-01

    The last few years has witnessed a rapid increase in the detections of galaxies at z>7, at the end of the reionization era. However, as a result of the increasing attenuation of Ly alpha emission by the partially neutral IGM at this redshift, it is becoming clear that the traditional means of redshift confirmation is bound for limited success; this presents a major challenge to galaxy spectroscopy as we probe deeper into the reionization era with JWST and ELTs. Through our survey of reionization-era analog galaxies at z~2, we find that low metallicity, low luminosity galaxies exhibit strong CIII]1909 nebular emission lines. If, as is expected, CIII] remains strong at high redshift, the line can be used as a powerful alternative to Ly alpha in spectroscopy of reionization-era galaxies. To explore this possibility, we will carry out deep HST WFC3/IR F128N narrow-band imaging of a sample of 8 galaxies at z=5.7 in two fields. At this redshift, the CIII] line is fortuitously located within the F128N passband, allowing detection of CIII] in this sample of spectroscopically confirmed galaxies, reaching a flux limit beyond what is possible with current ground-based observations. Combining the F128N narrow-band imaging with broad-band observations, we will reliably measure the CIII] flux for the brighter objects in our sample (J<~26), and measure or strongly constrain the stacked CIII] flux for fainter objects (J~27). This program will provide the first statistical sample of CIII] emission in galaxies close to the end of reionization. Success in this venture would usher in a new era of redshift confirmation at z>7, guiding the strategy of such programs on future major facilities.

  6. H I-SELECTED GALAXIES IN THE SLOAN DIGITAL SKY SURVEY. I. OPTICAL DATA

    SciTech Connect

    West, Andrew A.; Garcia-Appadoo, Diego A.; Dalcanton, Julianne J.; Ivezic, Zeljko; Bentz, Misty C.; Disney, Mike J.; Rockosi, Constance M.

    2010-02-15

    We present the optical data for 195 H I-selected galaxies that fall within both the Sloan Digital Sky Survey (SDSS) and the Parkes Equatorial Survey (ES). The photometric quantities have been independently recomputed for our sample using a new photometric pipeline optimized for large galaxies, thus correcting for SDSS's limited reliability for automatic photometry of angularly large or low surface brightness (LSB) galaxies. We outline the magnitude of the uncertainty in the SDSS catalog-level photometry and derive a quantitative method for correcting the over-sky subtraction in the SDSS photometric pipeline. The main thrust of this paper is to present the ES/SDSS sample and discuss the methods behind the improved photometry, which will be used in future scientific analysis. We present the overall optical properties of the sample and briefly compare to a volume-limited, optically selected sample. Compared to the optically selected SDSS sample (in the similar volume), H I-selected galaxies are bluer and more luminous (fewer dwarf ellipticals and more star formation). However, compared to typical SDSS galaxy studies, which have their own selection effect, our sample is bluer, fainter, and less massive.

  7. H I-Selected Galaxies in the Sloan Digital Sky Survey. I. Optical Data

    NASA Astrophysics Data System (ADS)

    West, Andrew A.; Garcia-Appadoo, Diego A.; Dalcanton, Julianne J.; Disney, Mike J.; Rockosi, Constance M.; Ivezić, Željko; Bentz, Misty C.; Brinkmann, J.

    2010-02-01

    We present the optical data for 195 H I-selected galaxies that fall within both the Sloan Digital Sky Survey (SDSS) and the Parkes Equatorial Survey (ES). The photometric quantities have been independently recomputed for our sample using a new photometric pipeline optimized for large galaxies, thus correcting for SDSS's limited reliability for automatic photometry of angularly large or low surface brightness (LSB) galaxies. We outline the magnitude of the uncertainty in the SDSS catalog-level photometry and derive a quantitative method for correcting the over-sky subtraction in the SDSS photometric pipeline. The main thrust of this paper is to present the ES/SDSS sample and discuss the methods behind the improved photometry, which will be used in future scientific analysis. We present the overall optical properties of the sample and briefly compare to a volume-limited, optically selected sample. Compared to the optically selected SDSS sample (in the similar volume), H I-selected galaxies are bluer and more luminous (fewer dwarf ellipticals and more star formation). However, compared to typical SDSS galaxy studies, which have their own selection effect, our sample is bluer, fainter, and less massive.

  8. Galaxy density profiles and shapes - II. Selection biases in strong lensing surveys

    NASA Astrophysics Data System (ADS)

    Mandelbaum, Rachel; van de Ven, Glenn; Keeton, Charles R.

    2009-09-01

    Many current and future astronomical surveys will rely on samples of strong gravitational lens systems to draw conclusions about galaxy mass distributions. We use a new strong lensing pipeline (presented in Paper I of this series) to explore selection biases that may cause the population of strong lensing systems to differ from the general galaxy population. Our focus is on point-source lensing by early-type galaxies with two mass components (stellar and dark matter) that have a variety of density profiles and shapes motivated by observational and theoretical studies of galaxy properties. We seek not only to quantify but also to understand the physics behind selection biases related to: galaxy mass, orientation and shape; dark matter profile parameters such as inner slope and concentration; and adiabatic contraction. We study how all of these properties affect the lensing Einstein radius, total cross-section, quad/double ratio and image separation distribution, with a flexible treatment of magnification bias to mimic different survey strategies. We present our results for two families of density profiles: cusped and deprojected Sérsic models. While we use fixed lens and source redshifts for most of the analysis, we show that the results are applicable to other redshift combinations, and we also explore the physics of how our results change for very different redshifts. We find significant (factors of several) selection biases with mass; orientation, for a given galaxy shape at fixed mass; cusped dark matter profile inner slope and concentration; concentration of the stellar and dark matter deprojected Sérsic models. Interestingly, the intrinsic shape of a galaxy does not strongly influence its lensing cross-section when we average over viewing angles. Our results are an important first step towards understanding how strong lens systems relate to the general galaxy population.

  9. IRAS observations of optically selected galaxies. I - The properties of the UGC redshift sample

    NASA Technical Reports Server (NTRS)

    Bothun, Gregory D.; Lonsdale, Carol J.; Rice, Walter

    1989-01-01

    The FIR properties of more than 2400 optically selected galaxies in the Uppsala General Catalog are examined. The galaxies were detected by IRAS at 60 and 100 microns and have measured redshifts. A simple radiative transfer model is presented to study the nature of dust-heating sources. It is shown that for many normal disk galaxies, dust heated by old disk stars competes with dust heated by UV photons from newly formed stars. It is found that the 60-micron/100-micron flux density ratio may be used as an indicator of the dominant dust-heating source. Scaling relations with galaxy size and mass are presented which make it possible to estimate the contributions of any cirrus-like component to the total FIR luminosity.

  10. ACTIVE GALACTIC NUCLEI SELECTED FROM GALEX SPECTROSCOPY: THE IONIZING SOURCE SPECTRUM AT z {approx} 1 ,

    SciTech Connect

    Barger, Amy J.; Cowie, Lennox L. E-mail: cowie@ifa.hawaii.ed

    2010-08-01

    We use a complete sample of Ly{alpha}-emission-line-selected active galactic nuclei (AGNs) obtained from nine deep blank fields observed with the grism spectrographs on the Galaxy Evolution Explorer (GALEX) satellite to measure the normalization and the spectral shape of the AGN contribution to the ionizing background (rest-frame wavelengths 700-900 A) at z {approx} 1. Our sample consists of 139 sources selected in the redshift range z = 0.65-1.25 in the near-ultraviolet (NUV; 2371 A central wavelength) channel. The area covered is 8.2 deg{sup 2} to a NUV magnitude of 20.5 (AB) and 0.92 deg{sup 2} at the faintest magnitude limit of 21.8. The GALEX AGN luminosity function agrees well with those obtained using optical and X-ray AGN samples, and the measured redshift evolution of the ionizing volume emissivity is similar to that previously obtained by measuring the GALEX far-ultraviolet (FUV; 1528 A central wavelength) magnitudes of an X-ray-selected sample. For the first time, we are able to construct the shape of the ionizing background at z {approx} 1 in a fully self-consistent way.

  11. OCCUPATION OF X-RAY-SELECTED GALAXY GROUPS BY X-RAY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Allevato, V.; Finoguenov, A.; Hasinger, G.; Cappelluti, N.; Miyaji, T.; Salvato, M.; Brusa, M.; Zamorani, G.; Gilli, R.; George, M. R.; Tanaka, M.; Silverman, J.; Civano, F.; Elvis, M.; Shankar, F.

    2012-10-10

    We present the first direct measurement of the mean halo occupation distribution (HOD) of X-ray-selected active galactic nuclei (AGNs) in the COSMOS field at z {<=} 1, based on the association of 41 XMM and 17 C-COSMOS AGNs with member galaxies of 189 X-ray-detected galaxy groups from XMM-Newton and Chandra data. We model the mean AGN occupation in the halo mass range log M{sub 200} [M{sub Sun }] = 13-14.5 with a rolling-off power law with the best-fit index {alpha} = 0.06(- 0.22; 0.36) and normalization parameter f{sub a} 0.05(0.04; 0.06). We find the mean HOD of AGNs among central galaxies to be modeled by a softened step function at log M{sub h} > log M{sub min} = 12.75(12.10, 12.95) M{sub Sun} while for the satellite AGN HOD we find a preference for an increasing AGN fraction with M{sub h} , suggesting that the average number of AGNs in satellite galaxies grows slower ({alpha}{sub s} < 0.6) than the linear proportion ({alpha}{sub s} = 1) observed for the satellite HOD of samples of galaxies. We present an estimate of the projected autocorrelation function (ACF) of galaxy groups over the range of r{sub p} = 0.1-40 h {sup -1} Mpc at (z) = 0.5. We use the large-scale clustering signal to verify the agreement between the group bias estimated by using the observed galaxy groups ACF and the value derived from the group mass estimates. We perform a measurement of the projected AGN-galaxy-group cross-correlation function, excluding from the analysis AGNs that are within galaxy groups and we model the two-halo term of the clustering signal with the mean AGN HOD based on our results.

  12. Resolved spectroscopy of adolescent and infant galaxies (1 < z < 10)

    NASA Astrophysics Data System (ADS)

    Wright, Shelley; IRIS Science Team

    2014-07-01

    The combination of integral field spectroscopy (IFS) and adaptive optics (AO) on TMT will be revolutionary in studying the distant universe. The high angular resolution exploited by an AO system with this large aperture will be essential for studying high-redshift (1 < z < 5) galaxies' kinematics and chemical abundance histories. At even greater distances, TMT will be essential for conducting follow-up spectroscopy of Ly-alpha emission from first lights galaxies (6 < z < 10) and determining their kinematics and morphologies. I will present simulations and sensitivity calculations for high-z and first light galaxies using the diffraction-limited instrument IRIS coupled with NFIRAOS. I will put these simulations in context with current IFS+AO high-z observations and future capabilities with JWST.

  13. Soft Gamma-ray selected radio galaxies: favouring giant size discovery

    NASA Astrophysics Data System (ADS)

    Panessa, Francesca; Bassani, Loredana

    2016-07-01

    Using the recent INTEGRAL/IBIS and Swift/BAT surveys we have extracted a sample of radio galaxies selected in the soft gamma-ray band. The sample consists of known and candidate radio galaxies. The sample extraction criteria will be presented and its general properties outlined. In particular we provide strong evidence that this soft gamma-ray selection favours the discovery of large size radio objects, otherwise known as Giant Radio Galaxies or GRG. The main reasons and/or conditions leading to the formation of these sources are still unclear and this result suggests that they maybe related to exceptional internal properties of the source central engine, like a high jet power or a long activity time. Broad band analysis of new GRG, discovered during this work, will also be presented.

  14. a Snapshot Survey of X-Ray Selected Central Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Edge, Alastair

    1999-07-01

    Central cluster galaxies are the most massive stellar systems known and have been used as standard candles for many decades. Only recently have central cluster galaxies been recognised to exhibit a wide variety of small scale {<100 pc} features that can only be reliably detected with HST resolution. The most intriguing of these are dust lanes which have been detected in many central cluster galaxies. Dust is not expected to survive long in the hostile cluster environment unless shielded by the ISM of a disk galaxy or very dense clouds of cold gas. WFPC2 snapshot images of a representative subset of the central cluster galaxies from an X-ray selected cluster sample would provide important constraints on the formation and evolution of dust in cluster cores that cannot be obtained from ground-based observations. In addition, these images will allow the AGN component, the frequency of multiple nuclei, and the amount of massive-star formation in central cluster galaxies to be ass es sed. The proposed HST observatio ns would also provide high-resolution images of previously unresolved gravitational arcs in the most massive clusters in our sample resulting in constraints on the shape of the gravitational potential of these systems. This project will complement our extensive multi-frequency work on this sample that includes optical spectroscopy and photometry, VLA and X-ray images for the majority of the 210 targets.

  15. The Mg II line profile in the Seyfert galaxy NGC 4151: A new outflowing component

    NASA Technical Reports Server (NTRS)

    Leech, Kieron J.; Penston, M. V.; Snijders, M. A. J.; Gull, T.

    1986-01-01

    The Mg II 2795, 2802A doublet in the Seyfert galaxy NGC 4151 was examined to search for velocity systems in absorption and emission. Evidence for a narrow, outflowing absorption system in Mg II having a velocity of +825 km/sec relative to the Sun, -165 km/sec relative to the systemic velocity of NGC 4151 is presented. This feature is not present in Ly alpha or C IV and possible explanations for this are considered. For the Mg II and C IV lines a model decomposition of the line profile is shown.

  16. The Mg II line profile in the Seyfert galaxy NGC 4151 - A new outflowing component

    NASA Technical Reports Server (NTRS)

    Leech, Kieron J.; Penston, M. V.; Snijders, M. A. J.; Gull, T. R.

    1987-01-01

    This paper examines the Mg II 2795-2802 A doublet in the Seyfert galaxy NGC 4151 at a higher resolution than has previously been used, searching for velocity systems in absorption and emission. Evidence is presented for a new, narrow, outflowing absorption system in Mg II having a velocity of 825 km/s relative to the sun, and -165 km/s relative to the systemic velocity of NGC 4151. This feature is not present in Ly-alpha or C IV and possible explanations for this are considered. For the Mg II and C IV lines, a model decomposition of the line profile is presented.

  17. Cold streams: detectability, relation to structure and characteristics

    NASA Astrophysics Data System (ADS)

    Goerdt, Tobias

    2015-02-01

    Cold gas streaming along the dark-matter filaments of the cosmic web is predicted to be the major provider of resources for disc buildup and star formation in massive galaxies in the early universe. We use hydrodynamical simulations to study to what extent these cold streams are traceable in the extended circum-galactic environment of galaxies via Ly alpha emission, Ly alpha absorption and selected low ionisation metal absorption lines. We predict the strength of the absorption signal produced by the streams and find that it is consistent with observations in high redshift galaxies. The characteristics of the Ly alpha emission of our simulated galaxies are similar in luminosity, morphology and extent to the observed Ly alpha blobs, with distinct kinematic features. We analyse the characteristics of the cold streams in simulations and present scaling relations for the amount of infall, its velocity, distribution and its clumpiness and compare our findings with observations.

  18. The Tully-Fisher Relation and its Residuals for a Broadly Selected Sample of Galaxies

    NASA Astrophysics Data System (ADS)

    Pizagno, James; Prada, Francisco; Weinberg, David H.; Rix, Hans-Walter; Pogge, Richard W.; Grebel, Eva K.; Harbeck, Daniel; Blanton, Michael; Brinkmann, J.; Gunn, James E.

    2007-09-01

    We measure the relation between galaxy luminosity and disk circular velocity (the Tully-Fisher [TF] relation), in the g, r, i, and z bands, for a broadly selected sample of galaxies from the Sloan Digital Sky Survey, with the goal of providing well-defined observational constraints for theoretical models of galaxy formation. The input sample of 234 galaxies has a roughly flat distribution of absolute magnitudes in the range -18.5 > Mr > -22, and our only morphological selection is an isophotal axis ratio cut b/a < 0.6 to allow accurate inclination corrections. Long-slit spectroscopy from the Calar Alto and MDM observatories yields usable Hα rotation curves for 162 galaxies (69%), with a representative color and morphology distribution. We define circular velocities V80 by evaluating the rotation curve at the radius containing 80% of the i-band light. Observational errors, including estimated distance errors due to peculiar velocities, are small compared to the intrinsic scatter of the TF relation. The slope of the forward TF relation steepens from -5.5 ± 0.2 mag (log10 km s-1)-1 in the g band to -6.6 ± 0.2 mag (log10 km s-1)-1 in the z band. The intrinsic scatter is σ approx 0.4 mag in all bands, and residuals from either the forward or inverse relations have an approximately Gaussian distribution. We discuss how Malmquist-type biases may affect the observed slope, intercept, and scatter. The scatter is not dominated by rare outliers or by any particular class of galaxies, although it drops slightly, to σ approx 0.36 mag, if we restrict the sample to nearly bulgeless systems. Correlations of TF residuals with other galaxy properties are weak: bluer galaxies are significantly brighter than average in the g-band TF relation but only marginally brighter in the i band; more concentrated (earlier type) galaxies are slightly fainter than average, and the TF residual is virtually independent of half-light radius, contrary to the trend expected for gravitationally

  19. 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.

  20. SPECTROSCOPY OF LUMINOUS z > 7 GALAXY CANDIDATES AND SOURCES OF CONTAMINATION IN z > 7 GALAXY SEARCHES

    SciTech Connect

    Capak, P.; Jullo, E.; Mobasher, B.; Scoville, N. Z.; Salvato, M.; McCracken, H.; Ilbert, O.; Menendez-Delmestre, K.; Aussel, H.; LeFloch, E.; Carilli, C.; Civano, F.; Elvis, M.; Giavalisco, M.; Kartaltepe, J.; Sanders, D. B.; Leauthaud, A.; Koekemoer, A. M.; Kneib, J.-P.; Schinnerer, E.

    2011-04-01

    We present three bright z{sup +}-dropout candidates selected from deep near-infrared (NIR) imaging of the COSMOS 2 deg{sup 2} field. All three objects match the 0.8-8 {mu}m colors of other published z > 7 candidates but are 3 mag brighter, facilitating further study. Deep spectroscopy of two of the candidates covering 0.64-1.02 {mu}m with Keck-DEIMOS and all three covering 0.94-1.10 {mu}m and 1.52-1.80 {mu}m with Keck-NIRSPEC detects weak spectral features tentatively identified as Ly{alpha} at z = 6.95 and z = 7.69 in two of the objects. The third object is placed at z {approx} 1.6 based on a 24 {mu}m and weak optical detection. A comparison with the spectral energy distributions of known z < 7 galaxies, including objects with strong spectral lines, large extinction, and large systematic uncertainties in the photometry, yields no objects with similar colors. However, the {lambda} > 1 {mu}m properties of all three objects can be matched to optically detected sources with photometric redshifts at z {approx} 1.8, so the non-detection in the i {sup +} and z {sup +} bands is the primary factor which favors a z > 7 solution. If any of these objects are at z {approx} 7, the bright end of the luminosity function is significantly higher at z > 7 than suggested by previous studies, but consistent within the statistical uncertainty and the dark matter halo distribution. If these objects are at low redshift, the Lyman break selection must be contaminated by a previously unknown population of low-redshift objects with very strong breaks in their broadband spectral energy distributions and blue NIR colors. The implications of this result on luminosity function evolution at high redshift are discussed. We show that the primary limitation of z > 7 galaxy searches with broad filters is the depth of the available optical data.

  1. Spitzer Imaging of Strongly lensed Herschel-selected Dusty Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Ma, Brian; Cooray, Asantha; Calanog, J. A.; Nayyeri, H.; Timmons, N.; Casey, C.; Baes, M.; Chapman, S.; Dannerbauer, H.; da Cunha, E.; De Zotti, G.; Dunne, L.; Farrah, D.; Fu, Hai; Gonzalez-Nuevo, J.; Magdis, G.; Michałowski, M. J.; Oteo, I.; Riechers, D. A.; Scott, D.; Smith, M. W. L.; Wang, L.; Wardlow, J.; Vaccari, M.; Viaene, S.; Vieira, J. D.

    2015-11-01

    We present the rest-frame optical spectral energy distribution (SED) and stellar masses of six Herschel-selected gravitationally lensed dusty, star-forming galaxies (DSFGs) at 1 < z < 3. These galaxies were first identified with Herschel/SPIRE imaging data from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). The targets were observed with Spitzer/IRAC at 3.6 and 4.5 μm. Due to the spatial resolution of the IRAC observations at the level of 2″, the lensing features of a background DSFG in the near-infrared are blended with the flux from the foreground lensing galaxy in the IRAC imaging data. We make use of higher resolution Hubble/WFC3 or Keck/NIRC2 Adaptive Optics imaging data to fit light profiles of the foreground lensing galaxy (or galaxies) as a way to model the foreground components, in order to successfully disentangle the foreground lens and background source flux densities in the IRAC images. The flux density measurements at 3.6 and 4.5 μm, once combined with Hubble/WFC3 and Keck/NIRC2 data, provide important constraints on the rest-frame optical SED of the Herschel-selected lensed DSFGs. We model the combined UV- to millimeter-wavelength SEDs to establish the stellar mass, dust mass, star formation rate, visual extinction, and other parameters for each of these Herschel-selected DSFGs. These systems have inferred stellar masses in the range 8 × 1010-4 × 1011 M⊙ and star formation rates of around 100 M⊙ yr-1. This puts these lensed submillimeter systems well above the SFR-M* relation observed for normal star-forming galaxies at similar redshifts. The high values of SFR inferred for these systems are consistent with a major merger-driven scenario for star formation.

  2. Optical Selection of Star-forming Galaxies at Redshifts 1 < z < 3

    NASA Astrophysics Data System (ADS)

    Adelberger, Kurt L.; Steidel, Charles C.; Shapley, Alice E.; Hunt, Matthew P.; Erb, Dawn K.; Reddy, Naveen A.; Pettini, Max

    2004-05-01

    Few galaxies have been found between the redshift ranges z<~1 probed by magnitude-limited surveys and z>~3 probed by Lyman break surveys. Comparison of galaxy samples at lower and higher redshift suggests that large numbers of stars were born and the Hubble sequence began to take shape at the intermediate redshifts 1galaxies throughout this important but unexplored redshift range. All the strategies are based on selecting galaxies for spectroscopy on the basis of their colors in ground-based images taken through a small number of optical filters: GRi for redshifts 0.85galaxies at 1galaxies that satisfy our color selection criteria. Our methodology is described in detail, allowing readers to devise analogous selection criteria for other optical filter systems. Based in part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and NASA and was made possible by a gift from the W. M. Keck Foundation.

  3. THE STAR FORMATION HISTORIES OF z {approx} 2 DUST-OBSCURED GALAXIES AND SUBMILLIMETER-SELECTED GALAXIES

    SciTech Connect

    Bussmann, R. S.; Dey, Arjun; Jannuzi, B. T.; Armus, L.; Desai, V.; Soifer, B. T.; Brown, M. J. I.; Gonzalez, A. H.; Melbourne, J.

    2012-01-10

    The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z {approx} 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M{sub *}) of two populations of Spitzer-selected ULIRGs that have extremely red R - [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6 {mu}m associated with stellar emission ({sup b}ump DOGs{sup )}, while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ({sup p}ower-law DOGs{sup )}. We measure M{sub *} by applying Charlot and Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M{sub *} values for SMGs, bump DOGs, and power-law DOGs are log(M{sub *}/M{sub Sun }) = 10.42{sup +0.42}{sub -0.36}, 10.62{sup +0.36}{sub -0.32}, and 10.71{sup +0.40}{sub -0.34}, respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z {approx} 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5 dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z {approx} 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M{sub *}, a situation that arises more naturally in major mergers than in smooth accretion-powered systems.

  4. Comparison of X-ray and optically selected galaxy clusters in the XXL-N field

    NASA Astrophysics Data System (ADS)

    Alis, Sinan; Pacaud, Florian; Pierre, Marguerite; Benoist, Christophe; Maurogordato, Sophie; Clerc, Nicolas; Faccioli, Lorenzo; Sadibekova, Tatyana

    2016-07-01

    Optically selected clusters from the CFHTLS and X-ray selected clusters from the intersecting XXL Survey are compared. We first compare the properties of the ˜100 galaxy clusters common to both catalogues in the redshift range of 0.1 < z < 1.2. Then we focus on the properties of the missed clusters on both sides and stress the impact of AGN contamination in this comparison. Finally scaling relations involving optical and X-ray quantities will be presented.

  5. The Properties of Radio Selected Galaxies in HIPASS/HIJASS and SDSS

    NASA Astrophysics Data System (ADS)

    Garcia-Appadoo, D. A.; Kilborn, V. A.; West, A. A.; Dalcanton, J. J.; Disney, M. J.

    2004-06-01

    We present a preliminary analysis of the properties of HI selected galaxies selected from the HIPASS and HIJASS surveys and that fall within the SDSS. From SDSS photometry in the early data release (EDR), we have obtained optical properties such as color, morphology, surface brightness and size. By comparing these with the HI properties derived from HIPASS/HIJASS, we are able to find relationships between the cool gas and the current generation of stars.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  7. A Spitzer-Selected Galaxy Cluster at z=1.62

    NASA Astrophysics Data System (ADS)

    Papovich, Casey J.; Momcheva, I.; Willmer, C. N. A.; Finkelstein, K. D.; Finkelstein, S. L.; Brodwin, M.; Dunlop, J. S.; Farrah, D.; Khan, S.; Lotz, J.; McCarthy, P.; McLure, R. J.; Rieke, M.; Rudnick, G.; Sivanadam, S.; Tran, K.

    2010-01-01

    We report the discovery of a galaxy cluster at z=1.62, located in the XMM-LSS field. This cluster candidate was originally selected as an overdensity of sources with red Spitzer/IRAC colors, satisfying [3.6] - [4.5] > -0.1 AB mag, within the Spitzer Wide-Area Infrared Extragalactic (SWIRE) survey covering 9 square degrees in this field. Photometric redshifts derived from Subaru XMM Deep Survey (BViz-bands), UKIRT Infrared Deep Survey--Ultra-Deep Survey (UKIDSS-UDS, JK-bands), and from the Spitzer Public UDS survey (SpUDS, 3.6-8.0 micron) for the galaxies in and around this cluster show that this structure corresponds to a galaxy surface density of sources at z=1.6 that is >20-sigma times the mean surface density at this redshift. We obtained spectroscopic observations of galaxies in cluster using Magellan/IMACS, and measure redshifts for six galaxies in the range z=1.62-1.65, all within 1.4 arcmin of the cluster center, which corresponds to a radius of 0.5 h-1 Mpc. We measured spectroscopic redshifts for three additional sources with z=1.61-1.63 within 1.4-2.8 arcmin (0.5-1 h-1 Mpc). The cluster appears to be dominated by red galaxies, with (z - J) > 1.7 mag. The photometric redshift distributions for the brightest red galaxies are centrally peaked at z=1.62, coincident with the spectroscopically confirmed galaxies. The J versus z-J color magnitude diagram of the galaxies in this cluster shows a strong red-sequence, which includes the dominant population of red galaxies. The intercept of the red-sequence is consistent with a stellar population formed at z=3 with passive evolution, implying that most of the stellar mass in this cluster formed at that epoch. We will summarize our plans to continue the study of this cluster, and our continuing survey to identify and study other high-redshift clusters. Support for this work was provided by NASA through an award issued by JPL/Caltech.

  8. Properties of H I-selected Galaxies: The Contribution of Gas-rich, LSB Galaxies to the Local Universe

    NASA Astrophysics Data System (ADS)

    García-Appadoo, D. A.; West, A. A.; Dalcanton, J. J.; Disney, M. J.

    2008-06-01

    Understanding the relationship between neutral hydrogen (H I) and stars in the interstellar medium of galaxies is integral to the study of galaxy evolution. Because stellar populations in galaxies form from collapsed clouds of hydrogen, we can naively claim that galaxies with few stars and large quantities of gas must be less ``evolved'' than those with little gas and many stars, and that galaxies evolve by converting their gas into stars. To first order this description is valid; we know that galaxies with large stellar populations must have once had fewer stars and more gas.

  9. Multi-wavelength seds of Herschel-selected galaxies in the cosmos field

    SciTech Connect

    Lee, Nicholas; Sanders, D. B.; Casey, Caitlin M.; Hung, Chao-Ling; Scoville, N. Z.; Capak, Peter; Bock, J.; Le Floc'h, Emeric; Aussel, Hervé; Ilbert, Olivier; Kartaltepe, Jeyhan S.; Roseboom, Isaac; Oliver, S. J.; Salvato, Mara; Aravena, M.; Berta, S.; Riguccini, L.; Symeonidis, M.

    2013-12-01

    We combine Herschel Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging Receiver maps of the full 2 deg{sup 2} Cosmic Evolution Survey (COSMOS) field with existing multi-wavelength data to obtain template and model-independent optical-to-far-infrared spectral energy distributions (SEDs) for 4218 Herschel-selected sources with log(L {sub IR}/L {sub ☉}) = 9.4-13.6 and z = 0.02-3.54. Median SEDs are created by binning the optical to far-infrared (FIR) bands available in COSMOS as a function of infrared luminosity. Herschel probes rest-frame wavelengths where the bulk of the infrared radiation is emitted, allowing us to more accurately determine fundamental dust properties of our sample of infrared luminous galaxies. We find that the SED peak wavelength (λ{sub peak}) decreases and the dust mass (M {sub dust}) increases with increasing total infrared luminosity (L {sub IR}). In the lowest infrared luminosity galaxies (log(L {sub IR}/L {sub ☉}) = 10.0-11.5), we see evidence of polycyclic aromatic hydrocarbon (PAH) features (λ ∼ 7-9 μm), while in the highest infrared luminosity galaxies (L {sub IR} > 10{sup 12} L {sub ☉}) we see an increasing contribution of hot dust and/or power-law emission, consistent with the presence of heating from an active galactic nucleus (AGN). We study the relationship between stellar mass and star formation rate of our sample of infrared luminous galaxies and find no evidence that Herschel-selected galaxies follow the SFR/M {sub *} 'main sequence' as previously determined from studies of optically selected, star-forming galaxies. Finally, we compare the mid-infrared to FIR properties of our infrared luminous galaxies using the previously defined diagnostic, IR8 ≡ L {sub IR}/L {sub 8}, and find that galaxies with L {sub IR} ≳ 10{sup 11.3} L {sub ☉} tend to systematically lie above (× 3-5) the IR8 'infrared main sequence', suggesting either suppressed PAH emission or an increasing contribution from

  10. The Swift Gamma-Ray Burst Host Galaxy Legacy Survey. I. Sample Selection and Redshift Distribution

    NASA Astrophysics Data System (ADS)

    Perley, D. A.; Krühler, T.; Schulze, S.; de Ugarte Postigo, A.; Hjorth, J.; Berger, E.; Cenko, S. B.; Chary, R.; Cucchiara, A.; Ellis, R.; Fong, W.; Fynbo, J. P. U.; Gorosabel, J.; Greiner, J.; Jakobsson, P.; Kim, S.; Laskar, T.; Levan, A. J.; Michałowski, M. J.; Milvang-Jensen, B.; Tanvir, N. R.; Thöne, C. C.; Wiersema, K.

    2016-01-01

    We introduce the Swift Gamma-Ray Burst Host Galaxy Legacy Survey (“SHOALS”), a multi-observatory high-redshift galaxy survey targeting the largest unbiased sample of long-duration gamma-ray burst (GRB) hosts yet assembled (119 in total). We describe the motivations of the survey and the development of our selection criteria, including an assessment of the impact of various observability metrics on the success rate of afterglow-based redshift measurement. We briefly outline our host galaxy observational program, consisting of deep Spitzer/IRAC imaging of every field supplemented by similarly deep, multicolor optical/near-IR photometry, plus spectroscopy of events without preexisting redshifts. Our optimized selection cuts combined with host galaxy follow-up have so far enabled redshift measurements for 110 targets (92%) and placed upper limits on all but one of the remainder. About 20% of GRBs in the sample are heavily dust obscured, and at most 2% originate from z\\gt 5.5. Using this sample, we estimate the redshift-dependent GRB rate density, showing it to peak at z∼ 2.5 and fall by at least an order of magnitude toward low (z = 0) redshift, while declining more gradually toward high (z∼ 7) redshift. This behavior is consistent with a progenitor whose formation efficiency varies modestly over cosmic history. Our survey will permit the most detailed examination to date of the connection between the GRB host population and general star-forming galaxies, directly measure evolution in the host population over cosmic time and discern its causes, and provide new constraints on the fraction of cosmic star formation occurring in undetectable galaxies at all redshifts.

  11. THE MASS-DEPENDENT CLUSTERING HISTORY OF K-SELECTED GALAXIES AT z < 4 IN THE SXDS/UDS FIELD

    SciTech Connect

    Furusawa, Junko; Sekiguchi, Kazuhiro; Takata, Tadafumi; Furusawa, Hisanori; Shimasaku, Kazuhiro; Simpson, Chris; Akiyama, Masayuki

    2011-02-01

    We investigate mass-dependent galaxy evolution based on a large sample of (more than 50,000) K-band selected galaxies in a multi-wavelength catalog of the Subaru/XMM-Newton Deep Survey and the UKIRT Infrared Deep Sky Survey/Ultra Deep Survey. We employ optical to near-infrared photometry to determine photometric redshifts of these galaxies. Then, we estimate the stellar mass of our sample galaxies using a standard fitting procedure as we used for estimation of the photometric redshift. From the sample galaxies, we obtain the stellar mass function of galaxies and the cosmic stellar mass density up to z {approx} 4. Our results are consistent with previous studies and we find a considerable number of low-mass galaxies (M{sub *} {approx} 10{sup 10.5}) at the redshift range 3 < z < 4. By combining stellar masses and spatial distributions of galaxies derived from a large number of galaxies in the contiguous wide and deep field, we examine properties of the mass-dependent clustering of galaxies. The correlation functions of our sample galaxies show clear evolution and they connect to that in the local universe consistently. Also, we find that the massive galaxies show strong clustering throughout our studied redshift range. The correlation length of massive galaxies rapidly decreases from z = 4 to 2. The mass of dark halos hosting the intermediate-mass value galaxies changes from high (10{sup 14} M{sub sun}) to low (10{sup 13} M{sub sun}) with decreasing redshift at around z {approx} 2. We also find some high-mass density regions of massive galaxies at 1.4 {<=} z < 2.5 in our sample. These concentrations of massive galaxies may be candidate progenitors of the present-day clusters of galaxies. At this redshift range, massive star-forming galaxies are the dominant population making up the structures and the passively evolving galaxies show stronger clustering and they may have formed earlier than those star-forming galaxies.

  12. The star formation history of mass-selected galaxies from the VIDEO survey

    NASA Astrophysics Data System (ADS)

    Zwart, Jonathan T. L.; Jarvis, Matt J.; Deane, Roger P.; Bonfield, David G.; Knowles, Kenda; Madhanpall, Nikhita; Rahmani, Hadi; Smith, Daniel J. B.

    2014-04-01

    We measure star formation rates (SFRs) and specific SFRs (SSFRs) of Ks -selected galaxies from the VISTA Deep Extragalactic Observations survey by stacking 1.4 GHz Very Large Array data. We split the sample, which spans 0 < z < 3 and stellar masses 108.0 < M*/M⊙ < 1011.5, into elliptical, irregular or starburst galaxies based on their spectral energy distributions. We find that SSFR falls with stellar mass, in agreement with the `downsizing' paradigm. We consider the dependence of the SSFR-mass slope on redshift: for our full and elliptical samples the slope flattens, but for the irregular and starburst samples the slope is independent of redshift. The rate of SSFR evolution reduces slightly with stellar mass for ellipticals, but irregulars and starbursts co-evolve across stellar masses. Our results for SSFR as a function of stellar mass and redshift are in agreement with those derived from other radio-stacking measurements of mass-selected passive and star-forming galaxies, but inconsistent with those generated from semi-analytic models, which tend to underestimate SFRs and SSFRs. There is a need for deeper high-resolution radio surveys such as those from telescopes like the next-generation MeerKAT in order to probe lower masses at earlier times and to permit direct detections, i.e. to study individual galaxies in detail.

  13. Soft γ-ray selected radio galaxies: favouring giant size discovery

    NASA Astrophysics Data System (ADS)

    Bassani, L.; Venturi, T.; Molina, M.; Malizia, A.; Dallacasa, D.; Panessa, F.; Bazzano, A.; Ubertini, P.

    2016-09-01

    Using the recent INTEGRAL/IBIS and Swift/BAT surveys we have extracted a sample of 64 confirmed plus three candidate radio galaxies selected in the soft gamma-ray band. The sample covers all optical classes and is dominated by objects showing a Fanaroff-Riley type II radio morphology; a large fraction (70 per cent) of the sample is made of `radiative mode' or high-excitation radio galaxies. We measured the source size on images from the NRAO VLA Sky Survey, the Faint Images of the Radio Sky at twenty-cm and the Sydney University Molonglo Sky Survey images and have compared our findings with data in the literature obtaining a good match. We surprisingly found that the soft gamma-ray selection favours the detection of large size radio galaxies: 60 per cent of objects in the sample have size greater than 0.4 Mpc while around 22 per cent reach dimension above 0.7 Mpc at which point they are classified as giant radio galaxies (GRGs), the largest and most energetic single entities in the Universe. Their fraction among soft gamma-ray selected radio galaxies is significantly larger than typically found in radio surveys, where only a few per cent of objects (1-6 per cent) are GRGs. This may partly be due to observational biases affecting radio surveys more than soft gamma-ray surveys, thus disfavouring the detection of GRGs at lower frequencies. The main reasons and/or conditions leading to the formation of these large radio structures are still unclear with many parameters such as high jet power, long activity time and surrounding environment all playing a role; the first two may be linked to the type of active galactic nucleus discussed in this work and partly explain the high fraction of GRGs found in the present sample. Our result suggests that high energy surveys may be a more efficient way than radio surveys to find these peculiar objects.

  14. The discovery of a young radio galaxy at z = 2.390 - Probing initial star formation at z less than approximately 3.0

    NASA Technical Reports Server (NTRS)

    Windhorst, Rogier A.; Burstein, David; Mathis, Doug F.; Neuschaefer, Lyman W.; Bertola, F.; Buson, L. M.; Koo, David C.; Matthews, Keith; Barthel, Peter D.; Chambers, K. C.

    1991-01-01

    The discovery of a weak radio galaxy from the Leiden Berkeley Deep Survey at a redshift of 2.390 is presented, as well as nine-band photometry for the galaxy and for surrounding objects. The source 53W002 is not variable on the time scales of years. Its rest-frame UV continuum is compared with IUE spectra of various nearby galaxies with relatively recent starbursts, and with nearby AGNs. It is inferred from the C IV/Ly-alpha and N V/Ly-alpha ratios that 53W002 has a Seyfert 1-like AGN, and that the ratios constrain the nonthermal component to about 35 percent of the observed UV continuum. Several independent age estimates yield a consistent value of 0.25-0.32 Gyr. The available data are consistent with 53W002 being a genuinely young galaxy seen at a redshift of 2.390 during its first major starburst. It likely started forming most of its current stars at redshifts between 2.5 and 3.0, suggesting that radio galaxies do not form the bulk of their stars coevally, but start doing so over a lengthy period of cosmic time.

  15. Photometric redshifts and clustering of emission line galaxies selected jointly by DES and eBOSS

    SciTech Connect

    Jouvel, S.; et al.

    2015-09-23

    We present the results of the first test plates of the extended Baryon Oscillation Spectroscopic Survey. This paper focuses on the emission line galaxies (ELG) population targetted from the Dark Energy Survey (DES) photometry. We analyse the success rate, efficiency, redshift distribution, and clustering properties of the targets. From the 9000 spectroscopic redshifts targetted, 4600 have been selected from the DES photometry. The total success rate for redshifts between 0.6 and 1.2 is 71\\% and 68\\% respectively for a bright and faint, on average more distant, samples including redshifts measured from a single strong emission line. We find a mean redshift of 0.8 and 0.87, with 15 and 13\\% of unknown redshifts respectively for the bright and faint samples. In the redshift range 0.6galaxy bias averaged on scales of 1 and 10~Mpc/h of 1.72 \\pm 0.1 for the bright sample and of 1.78 \\pm 0.12 for the faint sample. The error on the galaxy bias have been obtained propagating the errors in the correlation function to the fitted parameters. This redshift evolution for the galaxy bias is in agreement with theoretical expectations for a galaxy population with MB-5\\log h < -21.0. We note that biasing is derived from the galaxy clustering relative to a model for the mass fluctuations. We investigate the quality of the DES photometric redshifts and find that the outlier fraction can be reduced using a comparison between template fitting and neural network, or using a random forest algorithm.

  16. A Detailed Study of Two Optically Selected, High-Redshift Clusters of Galaxies

    NASA Technical Reports Server (NTRS)

    Lubin, Lori M.

    2000-01-01

    We are obtaining detailed X-ray spectral and structural data for two distant, optically-selected clusters of galaxies which are known X-ray emitters, CL1324+3011 at z = 0.76 and CL,1604+4304 at z = 0.90. These observations will allow us to place accurate constraints on the temperature, surface-brightness profile, and mass fraction of the intracluster medium in rich, optically-selected clusters at very high redshift. The two target clusters are the most well-studied systems at z greater than 0.7 in the optical and infrared regimes; therefore, with the addition of the XMM data, we plan to study the specifies of the relationship between the X-ray and optical properties and their implications for galaxy and cluster evolution.

  17. X-RAY SELECTED AGN HOST GALAXIES ARE SIMILAR TO INACTIVE GALAXIES OUT TO z = 3: RESULTS FROM CANDELS/CDF-S

    SciTech Connect

    Rosario, D. J.; Wuyts, S.; Nandra, K.; Mozena, M.; Faber, S. M.; Koo, D. C.; Koekemoer, A.; Ferguson, H.; Grogin, N.; McGrath, E.; Hathi, N. P.; Dekel, A.; Donley, J.; Dunlop, J. S.; Giavalisco, M.; Guo, Y.; Kocevski, D. D.; Laird, E.; Rangel, C.; Newman, J.; and others

    2013-01-20

    We use multi-band spatially resolved photometry from the Cosmic Assembly Near-IR Deep Legacy Survey in the 4 Ms Chandra Deep Field-South to explore the nuclear and extended colors, color gradients, and stellar populations of the host galaxies of X-ray selected active galactic nuclei (AGNs) out to z = 3. Based on a study of their central light, we develop X-ray based criteria to exclude objects with strong AGN contamination. We use stellar masses from the FIREWORKS database to understand and account for stellar mass selection effects and carefully study, for the first time, the resolved host galaxy properties of AGNs at z {approx} 2 in their rest-frame optical light without substantial nuclear contamination. AGN hosts span a sizable range of stellar masses, colors, and color gradients at these redshifts. Their colors, color gradients, and stellar population properties are very similar to inactive galaxies of the same stellar mass. At z {approx} 1, we find a slightly narrower range in host colors compared to inactive galaxies, as well as hints of more recent star formation. These differences are weaker or non-existent among AGN hosts at z {approx} 2. We discuss the importance of AGN-driven feedback in the quenching of galaxies at z {approx}> 1 and speculate on possible evolution in the relationship between black hole accretion and the host galaxy toward high redshifts.

  18. Selections from 2015: EGSY8p7, the Galaxy Far, Far Away

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-12-01

    Editors Note:In these last two weeks of 2015, well be looking at a few selections from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.Ly Emission from a Luminous z = 8.68 Galaxy: Implications for Galaxies as Tracers of Cosmic ReionizationPublished August 2015Main takeaway:A team led by Adi Zitrin (Hubble Fellow at California Institute of Technology) detected Ly emission in the bright galaxy EGSY8p7 using the MOSFIRE spectrograph at Keck Observatory. From this emission line, they calculated that the galaxy has an astonishing redshift of z=8.68.Why its interesting:This spectroscopic confirmation crowned EGSY8p7 as the record-holder for the farthest-known (and therefore oldest) galaxy. Its redshift shattered the previous record, a galaxy at z=7.73.Why its even more interesting than that:Spectroscopic detection of emission in EGSY8p7 with MOSFIRE. The black line is the raw data; the red line shows the best-fit model to the data. [Zitrin et al. 2015]Based on our understanding of how the universe evolved, the detection of Ly emission from this galaxy came as a surprise. At EGSY8p7s redshift of 8.68, the universe was still full of clouds of neutral hydrogen that should have absorbed the galaxys Ly emission long before it reached us. So what does it mean that we do see Ly emission from EGSY8p7? The reionization of the universe through which the neutral hydrogen clouds were made transparent may have been a patchy process. In particular, EGSY8p7 might have emitted an unusual amount of ionizing radiation, creating an early ionized bubble around it that allowed the Ly emission to escape.CitationAdi Zitrin et al 2015 ApJ 810 L12. doi:10.1088/2041-8205/810/1/L12

  19. SPECTROSCOPIC CONFIRMATION OF A z = 6.740 GALAXY BEHIND THE BULLET CLUSTER

    SciTech Connect

    Bradac, Marusa; Hall, Nicholas; Vanzella, Eros; Treu, Tommaso; Fontana, Adriano; Gonzalez, Anthony H.; Clowe, Douglas; Zaritsky, Dennis; Clement, Benjamin; Stiavelli, Massimo

    2012-08-10

    We present the first results of our spectroscopic follow-up of 6.5 < z < 10 candidate galaxies behind clusters of galaxies. We report the spectroscopic confirmation of an intrinsically faint Lyman break galaxy (LBG) identified as a z{sub 850LP}-band dropout behind the Bullet Cluster. We detect an emission line at {lambda} = 9412 A at >5{sigma} significance using a 16 hr long exposure with FORS2 VLT. Based on the absence of flux in bluer broadband filters, the blue color of the source, and the absence of additional lines, we identify the line as Ly{alpha} at z = 6.740 {+-} 0.003. The integrated line flux is f = (0.7 {+-} 0.1 {+-} 0.3) Multiplication-Sign 10{sup -17} erg{sup -1} s{sup -1} cm{sup -2} (the uncertainties are due to random and flux calibration errors, respectively) making it the faintest Ly{alpha} flux detected at these redshifts. Given the magnification of {mu} = 3.0 {+-} 0.2 the intrinsic (corrected for lensing) flux is f {sup int} = (0.23 {+-} 0.03 {+-} 0.10 {+-} 0.02) Multiplication-Sign 10{sup -17} erg{sup -1} s{sup -1} cm{sup -2} (additional uncertainty due to magnification), which is {approx}2-3 times fainter than other such measurements in z {approx} 7 galaxies. The intrinsic H{sub 160W}-band magnitude of the object is m{sup int}{sub H{sub 1{sub 6{sub 0{sub W}}}}}=27.57{+-}0.17, corresponding to 0.5 L* for LBGs at these redshifts. The galaxy is one of the two sub-L* LBG galaxies spectroscopically confirmed at these high redshifts (the other is also a lensed z = 7.045 galaxy), making it a valuable probe for the neutral hydrogen fraction in the early universe.

  20. An alma survey of sub-millimeter galaxies in the extended Chandra deep field south: Sub-millimeter properties of color-selected galaxies

    SciTech Connect

    Decarli, R.; Walter, F.; Hodge, J. A.; Rix, H.-W.; Schinnerer, E.; Smail, I.; Swinbank, A. M.; Karim, A.; Simpson, J. M.; Chapman, S.; Coppin, K. E. K.; Cox, P.; Dannerbauer, H.; Greve, T. R.; Ivison, R.; Knudsen, K. K.; Lindroos, L.; Van der Werf, P.; Weiß, A.

    2014-01-10

    We study the sub-millimeter properties of color-selected galaxies via a stacking analysis applied for the first time to interferometric data at sub-millimeter wavelengths. We base our study on 344 GHz ALMA continuum observations of ∼20''-wide fields centered on 86 sub-millimeter sources detected in the LABOCA Extended Chandra Deep Field South (ECDFS) Sub-millimeter Survey. We select various classes of galaxies (K-selected, star-forming sBzK galaxies, extremely red objects, and distant red galaxies) according to their optical/near-infrared fluxes. We find clear, >10σ detections in the stacked images of all these galaxy classes. We include in our stacking analysis Herschel/SPIRE data to constrain the dust spectral energy distribution of these galaxies. We find that their dust emission is well described by a modified blackbody with T {sub dust} ≈ 30 K and β = 1.6 and infrared luminosities of (5-11) × 10{sup 11} L {sub ☉} or implied star formation rates of 75-140 M {sub ☉} yr{sup –1}. We compare our results with those of previous studies based on single-dish observations at 870 μm and find that our flux densities are a factor 2-3 higher than previous estimates. The discrepancy is observed also after removing sources individually detected in ALESS maps. We report a similar discrepancy by repeating our analysis on 1.4 GHz observations of the whole ECDFS. Hence, we find tentative evidence that galaxies that are associated in projected and redshift space with sub-mm bright sources are brighter than the average population. Finally, we put our findings in the context of the cosmic star formation rate density as a function of redshift.

  1. Herschel-ATLAS: the surprising diversity of dust-selected galaxies in the local submillimetre Universe

    NASA Astrophysics Data System (ADS)

    Clark, C. J. R.; Dunne, L.; Gomez, H. L.; Maddox, S.; De Vis, P.; Smith, M. W. L.; Eales, S. A.; Baes, M.; Bendo, G. J.; Bourne, N.; Driver, S. P.; Dye, S.; Furlanetto, C.; Grootes, M. W.; Ivison, R. J.; Schofield, S. P.; Robotham, A. S. G.; Rowlands, K.; Valiante, E.; Vlahakis, C.; van der Werf, P.; Wright, A. H.; de Zotti, G.

    2015-09-01

    We present the properties of the first 250 μm blind sample of nearby galaxies (15 < D < 46 Mpc) containing 42 objects from the Herschel Astrophysical Terahertz Large Area Survey. Herschel's sensitivity probes the faint end of the dust luminosity function for the first time, spanning a range of stellar mass (7.4 < M⋆ < 11.3 log10 M⊙), star formation activity (-11.8 < SSFR < -8.9 log10 yr-1), gas fraction (3-96 per cent), and colour (0.6 < FUV-KS < 7.0 mag). The median cold dust temperature is 14.6 K, colder than in the Herschel Reference Survey (18.5 K) and Planck Early Release Compact Source Catalogue (17.7 K). The mean dust-to-stellar mass ratio in our sample is higher than these surveys by factors of 3.7 and 1.8, with a dust mass volume density of (3.7 ± 0.7) × 105 M⊙ Mpc-3. Counter-intuitively, we find that the more dust rich a galaxy, the lower its UV attenuation. Over half of our dust-selected sample are very blue in FUV-KS colour, with irregular and/or highly flocculent morphology; these galaxies account for only 6 per cent of the sample's stellar mass but contain over 35 per cent of the dust mass. They are the most actively star-forming galaxies in the sample, with the highest gas fractions and lowest UV attenuation. They also appear to be in an early stage of converting their gas into stars, providing valuable insights into the chemical evolution of young galaxies.

  2. AEGIS: The Diversity of Bright Near-IR Selected Distant RedGalaxies

    SciTech Connect

    Conselice, C.J.; Newman, J.A.; Georgakakis, A.; Almaini, O.; Coil, A.L.; Cooper, M.C.; Eisenhardt, P.; Foucaud, S.; Koekemoer, A.; Lotz, J.; Noeske, K.; Weiner, B.; Willmer, C.N.A

    2006-10-13

    We use deep and wide near infrared (NIR) imaging from the Palomar telescope combined with DEEP2 spectroscopy and Hubble Space Telescope (HST) and Chandra Space Telescope imaging to investigate the nature of galaxies that are red in NIR colors. We locate these 'distant red galaxies' (DRGs) through the color cut (J - K){sub vega} > 2.3 over 0.7 deg{sup 2}, where we find 1010 DRG candidates down to K{sub s} = 20.5. We combine 95 high quality spectroscopic redshifts with photometric redshifts from BRIJK photometry to determine the redshift and stellar mass distributions for these systems, and morphological/structural and X-ray properties for 107 DRGs in the Extended Groth Strip. We find that many bright (J - K){sub vega} > 2.3 galaxies with K{sub s} < 20.5 are at redshifts z < 2, with 64% between 1 < z < 2. The stellar mass distributions for these galaxies is broad, ranging from 10{sup 9} - 10{sup 12} M{sub {circle_dot}} , but with most z > 2 systems massive with M{sub *} > 10{sup 11} M{sub {circle_dot}}. HST imaging shows that the structural properties and morphologies of DRGs are also diverse, with the majority elliptical/compact (57%), and the remainder edge-on spirals (7%), and peculiar galaxies (29%). The DRGs at z < 1.4 with high quality spectroscopic redshifts are generally compact, with small half-light radii, and span a range in rest-frame optical properties. The spectral energy distributions for these objects differ from higher redshift DRGs: they are bluer by one magnitude in observed (I - J) color. A pure IR color selection of high redshift populations is not sufficient to identify unique populations, and other colors, or spectroscopic redshifts are needed to produce homogeneous samples.

  3. The Sloan Lens ACS Survey. I. A Large Spectroscopically Selected Sample of Massive Early-Type Lens Galaxies

    NASA Technical Reports Server (NTRS)

    Bolton, Adam S.; Burles, Scott; Koopmans, Leon V. E.; Treu, Tommaso; Moustakas, Leonidas A.

    2006-01-01

    The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple nebular emission lines at a redshift significantly higher than that of the SDSS target galaxy. The SLACS survey is optimized to detect bright early-type lens galaxies with faint lensed sources in order to increase the sample of known gravitational lenses suitable for detailed lensing, photometric, and dynamical modeling. In this paper, the first in a series on the current results of our HST Cycle 13 imaging survey, we present a catalog of 19 newly discovered gravitational lenses, along with nine other observed candidate systems that are either possible lenses, nonlenses, or nondetections. The survey efficiency is thus >=68%. We also present Gemini 8 m and Magellan 6.5 m integral-field spectroscopic data for nine of the SLACS targets, which further support the lensing interpretation. A new method for the effective subtraction of foreground galaxy images to reveal faint background features is presented. We show that the SLACS lens galaxies have colors and ellipticities typical of the spectroscopic parent sample from which they are drawn (SDSS luminous red galaxies and quiescent MAIN sample galaxies), but are somewhat brighter and more centrally concentrated. Several explanations for the latter bias are suggested. The SLACS survey provides the first statistically significant and homogeneously selected sample of bright early-type lens galaxies, furnishing a powerful probe of the structure of early-type galaxies within the half-light radius. The high confirmation rate of lenses in the SLACS survey suggests consideration of spectroscopic lens discovery as an explicit science goal of future spectroscopic galaxy surveys.

  4. GEMINI/GMOS SPECTROSCOPY OF 26 STRONG-LENSING-SELECTED GALAXY CLUSTER CORES

    SciTech Connect

    Bayliss, Matthew B.; Gladders, Michael D.; Koester, Benjamin P.; Hennawi, Joseph F.; Sharon, Keren; Dahle, Haakon; Oguri, Masamune

    2011-03-15

    We present results from a spectroscopic program targeting 26 strong-lensing cluster cores that were visually identified in the Sloan Digital Sky Survey (SDSS) and the Second Red-Sequence Cluster Survey (RCS-2). The 26 galaxy cluster lenses span a redshift range of 0.2 < z < 0.65, and our spectroscopy reveals 69 unique background sources with redshifts as high as z = 5.200. We also identify redshifts for 262 cluster member galaxies and measure the velocity dispersions and dynamical masses for 18 clusters where we have redshifts for N {>=} 10 cluster member galaxies. We account for the expected biases in dynamical masses of strong-lensing-selected clusters as predicted by results from numerical simulations and discuss possible sources of bias in our observations. The median dynamical mass of the 18 clusters with N {>=} 10 spectroscopic cluster members is M {sub Vir} = 7.84 x 10{sup 14} M {sub sun} h {sup -1} {sub 0.7}, which is somewhat higher than predictions for strong-lensing-selected clusters in simulations. The disagreement is not significant considering the large uncertainty in our dynamical data, systematic uncertainties in the velocity dispersion calibration, and limitations of the theoretical modeling. Nevertheless our study represents an important first step toward characterizing large samples of clusters that are identified in a systematic way as systems exhibiting dramatic strong-lensing features.

  5. Search for Hyperluminous Infrared Dust-obscured Galaxies Selected with WISE and SDSS

    NASA Astrophysics Data System (ADS)

    Toba, Y.; Nagao, T.

    2016-03-01

    We aim to search for hyperluminous infrared (IR) galaxies (HyLIRGs) with IR luminosity {L}{{IR}} > 1013 L⊙ by applying the selection method of dust-obscured galaxies (DOGs). They are spatially rare but could correspond to a maximum phase of cosmic star formation (SF) and/or active galactic nucleus (AGN) activity hence, they are a crucial population for understanding the SF and mass assembly history of galaxies. Combining the optical and IR catalogs obtained from the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE), we performed the extensive HyLIRGs survey; we selected 5311 IR-bright DOGs with i - [22] > 7.0 and flux at 22 μm > 3.8 mJy in 14,555 deg2, where i and [22] are i-band and 22 μm AB magnitudes, respectively. Among them, 67 DOGs have reliable spectroscopic redshifts that enable us to estimate their total IR luminosity based on the spectral energy distribution fitting. Consequently, we successfully discovered 24 HyLIRGs among the 67 spectroscopically confirmed DOGs. We found that (i) i - [22] color of IR-bright DOGs correlates with the total IR luminosity and (ii) the surface number density of HyLIRGs is >0.17 deg-2. A large fraction (˜73%) of IR-bright DOGs with i - [22] > 7.5 show {L}{{IR}} > 1013 L⊙, and the DOG criterion we adopted could be independently effective against the “W1W2-dropout method,” based on four WISE bands, for searching hyperluminous IR populations of galaxies.

  6. The SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Luminous Red Galaxy Target Selection

    NASA Astrophysics Data System (ADS)

    Prakash, Abhishek; Licquia, Timothy C.; Newman, Jeffrey A.; Ross, Ashley J.; Myers, Adam D.; Dawson, Kyle S.; Kneib, Jean-Paul; Percival, Will J.; Bautista, Julian E.; Comparat, Johan; Tinker, Jeremy L.; Schlegel, David J.; Tojeiro, Rita; Ho, Shirley; Lang, Dustin; Rao, Sandhya M.; McBride, Cameron K.; Ben Zhu, Guangtun; Brownstein, Joel R.; Bailey, Stephen; Bolton, Adam S.; Delubac, Timothée; Mariappan, Vivek; Blanton, Michael R.; Reid, Beth; Schneider, Donald P.; Seo, Hee-Jong; Carnero Rosell, Aurelio; Prada, Francisco

    2016-06-01

    We describe the algorithm used to select the luminous red galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-field Infrared Survey Explorer. LRG targets are required to meet a set of color selection criteria and have z-band and i-band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (median redshift 0.71). We demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS ancillary programs to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least ∼89% of the target sample yields secure redshift measurements. We also present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reached.

  7. The SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Luminous Red Galaxy Target Selection

    NASA Astrophysics Data System (ADS)

    Prakash, Abhishek; Licquia, Timothy C.; Newman, Jeffrey A.; Ross, Ashley J.; Myers, Adam D.; Dawson, Kyle S.; Kneib, Jean-Paul; Percival, Will J.; Bautista, Julian E.; Comparat, Johan; Tinker, Jeremy L.; Schlegel, David J.; Tojeiro, Rita; Ho, Shirley; Lang, Dustin; Rao, Sandhya M.; McBride, Cameron K.; Ben Zhu, Guangtun; Brownstein, Joel R.; Bailey, Stephen; Bolton, Adam S.; Delubac, Timothée; Mariappan, Vivek; Blanton, Michael R.; Reid, Beth; Schneider, Donald P.; Seo, Hee-Jong; Carnero Rosell, Aurelio; Prada, Francisco

    2016-06-01

    We describe the algorithm used to select the luminous red galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-field Infrared Survey Explorer. LRG targets are required to meet a set of color selection criteria and have z-band and i-band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (median redshift 0.71). We demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS ancillary programs to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least ˜89% of the target sample yields secure redshift measurements. We also present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reached.

  8. ALMA REDSHIFTS OF MILLIMETER-SELECTED GALAXIES FROM THE SPT SURVEY: THE REDSHIFT DISTRIBUTION OF DUSTY STAR-FORMING GALAXIES

    SciTech Connect

    Weiss, A.; De Breuck, C.; Aravena, M.; Biggs, A. D.; Marrone, D. P.; Bothwell, M.; Vieira, J. D.; Bock, J. J.; Aguirre, J. E.; Aird, K. A.; Ashby, M. L. N.; Bayliss, M.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Bethermin, M.; Brodwin, M.; Chapman, S. C.; and others

    2013-04-10

    Using the Atacama Large Millimeter/submillimeter Array, we have conducted a blind redshift survey in the 3 mm atmospheric transmission window for 26 strongly lensed dusty star-forming galaxies (DSFGs) selected with the South Pole Telescope. The sources were selected to have S{sub 1.4{sub mm}} > 20 mJy and a dust-like spectrum and, to remove low-z sources, not have bright radio (S{sub 843{sub MHz}} < 6 mJy) or far-infrared counterparts (S{sub 100{sub {mu}m}} < 1 Jy, S{sub 60{sub {mu}m}} < 200 mJy). We robustly detect 44 line features in our survey, which we identify as redshifted emission lines of {sup 12}CO, {sup 13}CO, C I, H{sub 2}O, and H{sub 2}O{sup +}. We find one or more spectral features in 23 sources yielding a {approx}90% detection rate for this survey; in 12 of these sources we detect multiple lines, while in 11 sources we detect only a single line. For the sources with only one detected line, we break the redshift degeneracy with additional spectroscopic observations if available, or infer the most likely line identification based on photometric data. This yields secure redshifts for {approx}70% of the sample. The three sources with no lines detected are tentatively placed in the redshift desert between 1.7 < z < 2.0. The resulting mean redshift of our sample is z-bar = 3.5. This finding is in contrast to the redshift distribution of radio-identified DSFGs, which have a significantly lower mean redshift of z-bar = 2.3 and for which only 10%-15% of the population is expected to be at z > 3. We discuss the effect of gravitational lensing on the redshift distribution and compare our measured redshift distribution to that of models in the literature.

  9. Ca II AND Na I QUASAR ABSORPTION-LINE SYSTEMS IN AN EMISSION-SELECTED SAMPLE OF SDSS DR7 GALAXY/QUASAR PROJECTIONS. I. SAMPLE SELECTION

    SciTech Connect

    Cherinka, B.; Schulte-Ladbeck, R. E.

    2011-10-15

    The aim of this project is to identify low-redshift host galaxies of quasar absorption-line systems by selecting galaxies that are seen in projection onto quasar sightlines. To this end, we use the Seventh Data Release of the Sloan Digital Sky Survey to construct a parent sample of 97,489 galaxy/quasar projections at impact parameters of up to 100 kpc to the foreground galaxy. We then search the quasar spectra for absorption-line systems of Ca II and Na I within {+-}500 km s{sup -1} of the galaxy's velocity. This yields 92 Ca II and 16 Na I absorption systems. We find that most of the Ca II and Na I systems are sightlines through the Galactic disk, through high-velocity cloud complexes in our halo, or Virgo Cluster sightlines. Placing constraints on the absorption line rest equivalent width significance ({>=}3.0{sigma}), the local standard of rest velocity along the sightline ({>=}345 km s{sup -1}), and the ratio of the impact parameter to the galaxy optical radius ({<=}5.0), we identify four absorption-line systems that are associated with low-redshift galaxies at high confidence, consisting of two Ca II systems (one of which also shows Na I) and two Na I systems. These four systems arise in blue, {approx}L*{sub r} galaxies. Tables of the 108 absorption systems are provided to facilitate future follow-up.

  10. X-Ray-selected Galaxy Groups in Boötes

    NASA Astrophysics Data System (ADS)

    Vajgel, Bruna; Jones, Christine; Lopes, Paulo A. A.; Forman, William R.; Murray, Stephen S.; Goulding, Andrew; Andrade-Santos, Felipe

    2014-10-01

    We present the X-ray and optical properties of the galaxy groups selected in the Chandra X-Boötes survey. We used follow-up Chandra observations to better define the group sample and their X-ray properties. Group redshifts were measured from the AGN and Galaxy Evolution Survey spectroscopic data. We used photometric data from the NOAO Deep Wide Field Survey to estimate the group richness (N gals) and the optical luminosity (L opt). Our final sample comprises 32 systems at z < 1.75 with 14 below z = 0.35. For these 14 systems, we estimate velocity dispersions (σ gr ) and perform a virial analysis to obtain the radii (R 200 and R 500) and total masses (M 200 and M 500) for groups with at least 5 galaxy members. We use the Chandra X-ray observations to derive the X-ray luminosity (LX ). We examine the performance of the group properties σgr, L opt, and LX , as proxies for the group mass. Understanding how well these observables measure the total mass is important to estimate how precisely the cluster/group mass function is determined. Exploring the scaling relations built with the X-Boötes sample and comparing these with samples from the literature, we find a break in the LX -M 500 relation at approximately M 500 = 5 × 1013 M ⊙ (for M 500 > 5 × 1013 M ⊙, M500 \\propto L_X0.61+/- 0.02, while for M 500 <= 5 × 1013 M ⊙, M500 \\propto L_X0.44+/- 0.05). Thus, the mass-luminosity relation for galaxy groups cannot be described by the same power law as galaxy clusters. A possible explanation for this break is the dynamical friction, tidal interactions, and projection effects that reduce the velocity dispersion values of the galaxy groups. By extending the cluster luminosity function to the group regime, we predict the number of groups that new X-ray surveys, particularly eROSITA, will detect. Based on our cluster/group luminosity function estimates, eROSITA will identify ~1800 groups (LX = 1041-1043 erg s-1) within a distance of 200 Mpc. Since groups lie in large

  11. The host galaxies of X-ray selected AGN: feeding and feedback

    NASA Astrophysics Data System (ADS)

    Merloni, A.; Bongiorno, A.

    2014-07-01

    Using the rich multi-band photometry in the COSMOS field we explore the host galaxy properties of a large, complete, sample of X-ray and spectroscopically selected AGN. Based on a two-components fit to their Spectral Energy Distribution, we derive rest-frame magnitudes, colors, stellar masses and star formation rates up to z˜3, and we study the connection between these host galaxy properties, accretion luminosity and obscuration in galactic nuclei across more than 2/3 of the age of the Universe. Although AGN activity and star formation appear to have a common triggering mechanism, we do not find any strong evidence signaling the influence of luminous AGN on the global properties of their host galaxies. Conversely, we found that the central black hole activity have profound effects on the surrounding matter on scales comparable to the gravitational sphere of influence of the black hole. We discuss the implication of our findings for the nature of the long sough-after 'Quasar mode' feedback from AGN.

  12. A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies

    NASA Astrophysics Data System (ADS)

    Dong, Xiao-Bo; Ho, Luis C.; Yuan, Weimin; Wang, Ting-Gui; Fan, Xiaohui; Zhou, Hongyan; Jiang, Ning

    2012-08-01

    We have conducted a systematic search of low-mass black holes (BHs) in active galactic nuclei (AGNs) with broad Hα emission lines, aiming at building a homogeneous sample that is more complete than previous ones for fainter, less highly accreting sources. For this purpose, we developed a set of elaborate, automated selection procedures and applied it uniformly to the Fourth Data Release of the Sloan Digital Sky Survey. Special attention is given to AGN-galaxy spectral decomposition and emission-line deblending. We define a sample of 309 type 1 AGNs with BH masses in the range 8 × 104-2 × 106 M ⊙ (with a median of 1.2 × 106 M ⊙), using the virial mass estimator based on the broad Hα line. About half of our sample of low-mass BHs differs from that of Greene & Ho, with 61 of them discovered here for the first time. Our new sample picks up more AGNs with low accretion rates: the Eddington ratios of the present sample range from <~ 0.01 to ~1, with 30% below 0.1. This suggests that a significant fraction of low-mass BHs in the local universe are accreting at low rates. The host galaxies of the low-mass BHs have luminosities similar to those of L* field galaxies, optical colors of Sbc spirals, and stellar spectral features consistent with a continuous star formation history with a mean stellar age of less than 1 Gyr.

  13. KAT-7 observations of an unbiased sample of mass-selected galaxy clusters

    NASA Astrophysics Data System (ADS)

    Bernardi, G.; Venturi, T.; Cassano, R.; Dallacasa, D.; Brunetti, G.; Cuciti, V.; Johnston-Hollitt, M.; Oozeer, N.; Parekh, V.; Smirnov, O. M.

    2016-02-01

    The presence of megaparsec-scale radio haloes in galaxy clusters has already been established by many observations over the last two decades. The emerging explanation for the formation of these giant sources of diffuse synchrotron radio emission is that they trace turbulent regions in the intracluster medium, where particles are trapped and accelerated during cluster mergers. Our current observational knowledge is, however, mainly limited to massive systems. Here we present observations of a sample of 14 mass-selected galaxy clusters, i.e. M500 > 4 × 1014 M⊙, in the Southern hemisphere, aimed to study the occurrence of radio haloes in low-mass clusters and test the correlation between the radio halo power at 1.4 GHz P1.4 and the cluster mass M500. Our observations were performed with the 7-element Karoo Array Telescope at 1.86 GHz. We found three candidates to host diffuse cluster-scale emission and derived upper limits at the level of 0.6-1.9 × 1024 Watt Hz-1 for ˜50 per cent of the clusters in the sample, significantly increasing the number of clusters with radio halo information in the considered mass range. Our results confirm that bright radio haloes in less massive galaxy clusters are statistically rare.

  14. AEGIS: The Diversity of Bright Near-IR-selected Distant Red Galaxies

    NASA Astrophysics Data System (ADS)

    Conselice, C. J.; Newman, J. A.; Georgakakis, A.; Almaini, O.; Coil, A. L.; Cooper, M. C.; Eisenhardt, P.; Foucaud, S.; Koekemoer, A.; Lotz, J.; Noeske, K.; Weiner, B.; Willmer, C. N. A.

    2007-05-01

    We use deep and wide near-infrared (NIR) imaging from the Palomar telescope combined with DEEP2 spectroscopy and HST and Chandra imaging to investigate the nature of galaxies that are red in NIR colors. We locate these ``distant red galaxies'' (DRGs) through the color cut (J-K)Vega>2.3 over 0.7 deg2, where we find 1010 DRG candidates down to Ks=20.5. We combine 95 high-quality spectroscopic redshifts with photometric redshifts from BRIJK photometry to determine the redshift and stellar mass distributions for these systems, and the morphological/structural and X-ray properties for 107 DRGs in the Extended Groth Strip. We find that many bright (J-K)Vega>2.3 galaxies with Ks<20.5 are at redshifts z<2, with 64% in the range 1galaxies are broad, ranging from 109 to 1012 Msolar, but with most z>2 systems being massive with M*>1011 Msolar. HST imaging shows that the structural properties and morphologies of DRGs are also diverse, with the majority elliptical/compact (57%) and the remainder edge-on spiral (7%) and peculiar (29%). The DRGs at z<1.4 with high-quality spectroscopic redshifts are generally compact, with small half-light radii, and span a range in rest-frame optical properties. The spectral energy distribution for the DRGs at z<1.4 differs from higher redshift DRGs: they are bluer by 1 mag in observed (I-J) color. A pure IR color selection of high-redshift populations is not sufficient to identify unique populations, and other colors or spectroscopic redshifts are needed to produce homogeneous samples.

  15. Occurrence of radio halos in galaxy clusters. Insight from a mass-selected sample

    NASA Astrophysics Data System (ADS)

    Cuciti, V.; Cassano, R.; Brunetti, G.; Dallacasa, D.; Kale, R.; Ettori, S.; Venturi, T.

    2015-08-01

    Context. Giant radio halos (RH) are diffuse Mpc-scale synchrotron sources detected in some massive and merging galaxy clusters. An unbiased study of the statistical properties of RHs is crucial to constraining their origin and evolution. Aims: We investigate the occurrence of RHs and its dependence on the cluster mass in a Sunyaev-Zel'dovich (SZ)-selected sample of galaxy clusters, which is nearly a mass-selected sample. Moreover, we analyse the connection between RHs and merging clusters. Methods: We selected from the Planck SZ catalogue clusters with M ≥ 6 × 1014M⊙ at z = 0.08-0.33 and we searched for the presence of RHs using the NVSS for z < 0.2 and the GMRT RH survey (GRHS) and its extension (EGRHS) for 0.2 < z < 0.33. We used archival Chandra X-ray data to derive information on the dynamical status of the clusters. Results: We confirm that RH clusters are merging systems while the majority of clusters without RH are relaxed, thus supporting the idea that mergers play a fundamental role in the generation of RHs. We find evidence for an increase in the fraction of clusters with RHs with the cluster mass and this is in line with expectations derived on the basis of the turbulence re-acceleration scenario. Finally, we discuss the effect of the incompleteness of our sample on this result.

  16. THE AzTEC/SMA INTERFEROMETRIC IMAGING SURVEY OF SUBMILLIMETER-SELECTED HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Younger, Joshua D.; Fazio, Giovanni G.; Huang Jiasheng; Ashby, Matthew L. N.; Gurwell, Mark A.; Petitpas, Glen R.; Wilner, David J.; Yun, Min S.; Wilson, Grant W.; Scott, Kimberly S.; Austermann, Jason; Perera, Thushara; Peck, Alison B.; Hughes, David H.; Aretxaga, Itziar; Kim, Sungeun; Lowenthal, James D.

    2009-10-10

    We present results from a continuing interferometric survey of high-redshift submillimeter galaxies (SMGs) with the Submillimeter Array, including high-resolution (beam size approx2 arcsec) imaging of eight additional AzTEC 1.1 mm selected sources in the COSMOS field, for which we obtain six reliable (peak signal-to-noise ratio (S/N) >5 or peak S/N >4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N >4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric follow up. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology-including the nature of SMGs with multiple radio counterparts and constraints on the physical scale of the far infrared-of the sample, and (3) find additional evidence for a population of extremely luminous, radio-dim SMGs that peaks at higher redshift than previous, radio-selected samples. In particular, the presence of such a population of high-redshift sources has important consequences for models of galaxy formation-which struggle to account for such objects even under liberal assumptions-and dust production models given the limited time since the big bang.

  17. The Properties of Radio Selected Galaxies in HIPASS/HIJASS and SDSS

    NASA Astrophysics Data System (ADS)

    Garcia-Appadoo, D.; West, A.; Disney, M.; Dalcanton, J.; Kilborn, V.

    2005-06-01

    We present a preliminary analysis of the properties of HI selected galaxies that fall within the HIPASS and HIJASS neutral hydrogen surveys, and the optical SDSS region. From SDSS photometry, we have obtained optical properties such as colour, morphology, surface brightness and size. SDSS spectra yield rough properties of the ISM such as metallicity, SFR, and extinction. By comparing these with the HI properties derived from HIPASS/HIJASS, we are able to find relationships between the cool gas (which has the potential to make stars), and the current generation of stars.

  18. Host galaxy colour gradients and accretion disc obscuration in AEGIS z ~ 1 X-ray-selected active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Pierce, C. M.; Lotz, J. M.; Salim, S.; Laird, E. S.; Coil, A. L.; Bundy, K.; Willmer, C. N. A.; Rosario, D. J. V.; Primack, J. R.; Faber, S. M.

    2010-10-01

    We describe the effect of active galactic nucleus (AGN) light on host galaxy optical and UV-optical colours, as determined from X-ray-selected AGN host galaxies at z ~ 1, and compare the AGN host galaxy colours to those of a control sample matched to the AGN sample in both redshift and stellar mass. We identify as X-ray-selected AGNs 8.7+4-3 per cent of the red-sequence control galaxies, 9.8 +/- 3 per cent of the blue-cloud control galaxies and 14.7+4-3 per cent of the green-valley control galaxies. The nuclear colours of AGN hosts are generally bluer than their outer colours, while the control galaxies exhibit redder nuclei. AGNs in blue-cloud host galaxies experience less X-ray obscuration, while AGNs in red-sequence hosts have more, which is the reverse of what is expected from general considerations of the interstellar medium. Outer and integrated colours of AGN hosts generally agree with the control galaxies, regardless of X-ray obscuration, but the nuclear colours of unobscured AGNs are typically much bluer, especially for X-ray luminous objects. Visible point sources are seen in many of these, indicating that the nuclear colours have been contaminated by AGN light and that obscuration of the X-ray radiation and visible light are therefore highly correlated. Red AGN hosts are typically slightly bluer than red-sequence control galaxies, which suggests that their stellar populations are slightly younger. We compare these colour data to current models of AGN formation. The unexpected trend of less X-ray obscuration in blue-cloud galaxies and more in red-sequence galaxies is problematic for all AGN feedback models, in which gas and dust is thought to be removed as star formation shuts down. A second class of models involving radiative instabilities in hot gas is more promising for red-sequence AGNs but predicts a larger number of point sources in red-sequence AGNs than is observed. Regardless, it appears that multiple AGN models are necessary to explain the

  19. A 21 Centimeter Absorber Identified with a Spiral Galaxy: Hubble Space Telescope Faint Object Spectrograph and Wide-Field Camera Observations of 3CR 196

    NASA Technical Reports Server (NTRS)

    Cohen, Ross D.; Beaver, E. A.; Diplas, Athanassios; Junkkarinen, Vesa T.; Barlow, Thomas A.; Lyons, Ronald W.

    1996-01-01

    We present imaging and spectroscopy of the quasar 3CR 196 (z(sub e) = 0.871), which has 21 cm and optical absorption at z(sub a) = 0.437. We observed the region of Ly alpha absorption in 3CR 196 at z(sub a) = 0.437 with the Faint Object Spectrograph on the Hubble Space Telescope. This region of the spectrum is complicated because of the presence of a Lyman limit and strong lines from a z(sub a) approx. z(sub e) system. We conclude that there is Ly alpha absorption with an H I column density greater than 2.7 x 10(exp 19) cm(exp -2) and most probably 1.5 x 10(exp 20) cm(exp -2). Based on the existence of the high H I column density along both the optical and radio lines of sight, separated by more than 15 kpc, we conclude that the Ly alpha absorption must arise in a system comparable in size to the gaseous disks of spiral galaxies. A barred spiral galaxy, previously reported as a diffuse object in the recent work of Boisse and Boulade, can be seen near the quasar in an image taken at 0.1 resolution with the Wide Field Planetary Camera 2 on the HST. If this galaxy is at the absorption redshift, the luminosity is approximately L(sub *) and any H I disk should extend in front of the optical quasar and radio lobes of 3CR 196, giving rise to both the Ly alpha and 21 cm absorption. In the z(sub a) approx. z(sub e) system we detect Lyman lines and the Lyman limit, as well as high ion absorption lines of C III, N V, S VI, and O VI. This absorption probably only partially covers the emission-line region. The ionization parameter is approximately 0.1. Conditions in this region may be similar to those in broad absorption line QSOs.

  20. A Census of Optical and Near-Infrared Selected Star-forming and Passively Evolving Galaxies at Redshift z ~ 2

    NASA Astrophysics Data System (ADS)

    Reddy, Naveen A.; Erb, Dawn K.; Steidel, Charles C.; Shapley, Alice E.; Adelberger, Kurt L.; Pettini, Max

    2005-11-01

    Using the extensive multiwavelength data in the GOODS-North field, including our ground-based rest-frame UV spectroscopy and near-IR imaging, we construct and draw comparisons between samples of optical and near-IR selected star-forming and passively evolving galaxies at redshifts 1.4<~z<~2.6. We find overlap at the 70%-80% level in samples of z~2 star-forming galaxies selected by their optical (UnGR) and near-IR (BzK) colors when subjected to common K-band limits. Deep Chandra data indicate a ~25% AGN fraction among near-IR selected objects, much of which occurs among near-IR bright objects (Ks<20 Vega). Using X-rays as a proxy for the bolometric star formation rate (SFR) and stacking the X-ray emission for the remaining (non-AGN) galaxies, we find that the SFR distributions of UnGR, BzK, and J-Ks>2.3 galaxies (i.e., distant red galaxies; DRGs) are very similar as a function of Ks, with Ks<20 galaxies having ~120 Msolar yr-1, a factor of 2-3 higher than those with Ks>20.5. The absence of X-ray emission from the reddest DRGs and BzK galaxies with (z-K)AB>~3 indicates that they must have declining star formation histories to explain their red colors and low SFRs. While the M/L ratio of passively evolving galaxies may be larger on average, the Spitzer IRAC data indicate that their inferred stellar masses do not exceed the range spanned by optically selected galaxies, suggesting that the disparity in current SFR may not indicate a fundamental difference between optical and near-IR selected massive galaxies (M*>1011 Msolar). We consider the contribution of optical, near-IR, and submillimeter selected galaxies to the star formation rate density (SFRD) at z~2, taking into account sample overlap. The SFRD in the interval 1.4<~z<~2.6 of UnGR and BzK galaxies to Ks=22 and DRGs to Ks=21 is ~0.10+/-0.02 Msolar yr-1 Mpc-3. Optically selected galaxies to R=25.5 and Ks=22.0 account for ~70% of this total. Greater than 80% of radio-selected submillimeter galaxies to S850

  1. High redshift galaxies in the ALHAMBRA survey . I. Selection method and number counts based on redshift PDFs

    NASA Astrophysics Data System (ADS)

    Viironen, K.; Marín-Franch, A.; López-Sanjuan, C.; Varela, J.; Chaves-Montero, J.; Cristóbal-Hornillos, D.; Molino, A.; Fernández-Soto, A.; Vilella-Rojo, G.; Ascaso, B.; Cenarro, A. J.; Cerviño, M.; Cepa, J.; Ederoclite, A.; Márquez, I.; Masegosa, J.; Moles, M.; Oteo, I.; Pović, M.; Aguerri, J. A. L.; Alfaro, E.; Aparicio-Villegas, T.; Benítez, N.; Broadhurst, T.; Cabrera-Caño, J.; Castander, J. F.; Del Olmo, A.; González Delgado, R. M.; Husillos, C.; Infante, L.; Martínez, V. J.; Perea, J.; Prada, F.; Quintana, J. M.

    2015-04-01

    Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so-called dropout technique or Ly-α selection. However, the availability of multifilter data now allows the dropout selections to be replaced by direct methods based on photometric redshifts. In this paper we present the methodology to select and study the population of high redshift galaxies in the ALHAMBRA survey data. Aims: Our aim is to develop a less biased methodology than the traditional dropout technique to study the high redshift galaxies in ALHAMBRA and other multifilter data. Thanks to the wide area ALHAMBRA covers, we especially aim at contributing to the study of the brightest, least frequent, high redshift galaxies. Methods: The methodology is based on redshift probability distribution functions (zPDFs). It is shown how a clean galaxy sample can be obtained by selecting the galaxies with high integrated probability of being within a given redshift interval. However, reaching both a complete and clean sample with this method is challenging. Hence, a method to derive statistical properties by summing the zPDFs of all the galaxies in the redshift bin of interest is introduced. Results: Using this methodology we derive the galaxy rest frame UV number counts in five redshift bins centred at z = 2.5,3.0,3.5,4.0, and 4.5, being complete up to the limiting magnitude at mUV(AB) = 24, where mUV refers to the first ALHAMBRA filter redwards of the Ly-α line. With the wide field ALHAMBRA data we especially contribute to the study of the brightest ends of these counts, accurately sampling the surface densities down to mUV(AB) = 21-22. Conclusions: We show that using the zPDFs it is easy to select a very clean sample of high redshift galaxies. We also show that it is better to do statistical analysis of the properties of galaxies using a probabilistic approach, which takes into account both the incompleteness and contamination issues in a

  2. The Multiwavelength Survey by Yale-Chile (MUSYC): Deep Near-Infrared Imaging and the Selection of Distant Galaxies

    NASA Astrophysics Data System (ADS)

    Quadri, Ryan; Marchesini, Danilo; van Dokkum, Pieter; Gawiser, Eric; Franx, Marijn; Lira, Paulina; Rudnick, Gregory; Urry, C. Megan; Maza, José; Kriek, Mariska; Barrientos, L. Felipe; Blanc, Guillermo A.; Castander, Francisco J.; Christlein, Daniel; Coppi, Paolo S.; Hall, Patrick B.; Herrera, David; Infante, Leopoldo; Taylor, Edward N.; Treister, Ezequiel; Willis, Jon P.

    2007-09-01

    We present deep near-infrared JHK imaging of four 10' × 10' fields. The observations were carried out as part of the Multiwavelength Survey by Yale-Chile (MUSYC) with ISPI on the CTIO 4 m telescope. The typical point-source limiting depths are J ~ 22.5, H ~ 21.5, and K ~ 21 (5 σ Vega). The effective seeing in the final images is ~1.0″. We combine these data with MUSYC UBVRIz imaging to create K-selected catalogs that are unique for their uniform size, depth, filter coverage, and image quality. We investigate the rest-frame optical colors and photometric redshifts of galaxies that are selected using common color selection techniques, including distant red galaxies (DRGs), star-forming and passive BzKs, and the rest-frame UV-selected BM, BX, and Lyman break galaxies (LBGs). These techniques are effective at isolating large samples of high-redshift galaxies, but none provide complete or uniform samples across the targeted redshift ranges. The DRG and BM/BX/LBG criteria identify populations of red and blue galaxies, respectively, as they were designed to do. The star-forming BzKs have a very wide redshift distribution, extending down to z ~ 1, a wide range of colors, and may include galaxies with very low specific star formation rates. In comparison, the passive BzKs are fewer in number, have a different distribution of K magnitudes, and have a somewhat different redshift distribution. By combining either the DRG and BM/BX/LBG criteria, or the star-forming and passive BzK criteria, it appears possible to define a reasonably complete sample of galaxies to our flux limit over specific redshift ranges. However, the redshift dependence of both the completeness and sampled range of rest-frame colors poses an ultimate limit to the usefulness of these techniques.

  3. Low-redshift Lyman-alpha absorption lines and the dark matter halos of disk galaxies

    NASA Technical Reports Server (NTRS)

    Maloney, Philip

    1992-01-01

    Ultraviolet observations of the low-redshift quasar 3C 273 using the Hubble Space Telescope have revealed many more Lyman-alpha absorption lines than would be expected from extrapolation of the absorption systems seen toward QSOs at z about 2. It is shown here that these absorption lines can plausibly be produced by gas at large radii in the disks of spiral and irregular galaxies; the gas is confined by the dark matter halos and ionized and heated by the extragalactic radiation field. This scenario does not require the extragalactic ionizing radiation field to decline as rapidly with decreasing z as the QSO emissivity. Observations of Ly-alpha absorption through the halos of known galaxies at low redshift will constrain both the extragalactic background and the properties of galactic halos.

  4. Galaxies in x-ray selected clusters and groups in Dark Energy Survey data. I. Stellar mass growth of bright central galaxies since z ~ 1.2

    DOE PAGESBeta

    Zhang, Y.; Miller, C.; McKay, T.; Rooney, P.; Evrard, A. E.; Romer, A. K.; R. Perfecto; Song, J.; Desai, S.; Mohr, J.; et al

    2016-01-14

    Here, using the science verification data of the Dark Energy Survey for a new sample of 106 X-ray selected clusters and groups, we study the stellar mass growth of bright central galaxies (BCGs) since redshift z ~ 1.2. Compared with the expectation in a semi-analytical model applied to the Millennium Simulation, the observed BCGs become under-massive/under-luminous with decreasing redshift.

  5. BLOX: the Bonn lensing, optical, and X-ray selected galaxy clusters. I. Cluster catalog construction

    NASA Astrophysics Data System (ADS)

    Dietrich, J. P.; Erben, T.; Lamer, G.; Schneider, P.; Schwope, A.; Hartlap, J.; Maturi, M.

    2007-08-01

    The mass function of galaxy clusters is an important cosmological probe. Differences in the selection method could potentially lead to biases when determining the mass function. From the optical and X-ray data of the XMM-Newton Follow-Up Survey, we obtained a sample of galaxy cluster candidates using weak gravitational lensing, the optical Postman matched filter method, and a search for extended X-ray sources. We developed our weak-lensing search criteria by testing the performance of the aperture mass statistic on realistic ray-tracing simulations matching our survey parameters and by comparing two filter functions. We find that the dominant noise source for our survey is shape noise at almost all significance levels and that spurious cluster detections due to projections of large-scale structures are negligible, except possibly for highly significantly detected peaks. Our full cluster catalog has 155 cluster candidates, 116 found with the Postman matched filter, 59 extended X-ray sources, and 31 shear selected potential clusters. Most of these cluster candidates were not previously known. The present catalog will be a solid foundation for studying possible selection effects in either method. Based on observations carried out at the European Southern Observatory, La Silla, Chile under program Nos. 170.A-0789, 70.A-0529, 71.A-0110, 072.A-0061, 073.A-0050. The cluster catalogs are only 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/cgi-bin/qcat?J/A+A/470/821

  6. Higher prevalence of X-ray selected AGN in intermediate-age galaxies up to z ˜ 1

    NASA Astrophysics Data System (ADS)

    Hernán-Caballero, Antonio; Alonso-Herrero, Almudena; Pérez-González, Pablo G.; Barro, Guillermo; Aird, James; Ferreras, Ignacio; Cava, Antonio; Cardiel, Nicolás; Esquej, Pilar; Gallego, Jesús; Nandra, Kirpal; Rodríguez-Zaurín, Javier

    2014-10-01

    We analyse the stellar populations in the host galaxies of 53 X-ray selected optically dull active galactic nuclei (AGN) at 0.34 < z < 1.07 with ultradeep (mAB = 26.5, 3σ) optical medium-band (R ˜ 50) photometry from the Survey for High-z Absorption Red and Dead Sources (SHARDS). The spectral resolution of SHARDS allows us to consistently measure the strength of the 4000 Å break, Dn(4000), a reliable age indicator for stellar populations. We confirm that most X-ray selected moderate-luminosity AGN (LX < 1044 erg s-1) are hosted by massive galaxies (typically M* >1010.5 M⊙) and that the observed fraction of galaxies hosting an AGN increases with the stellar mass. A careful selection of random control samples of inactive galaxies allows us to remove the stellar mass and redshift dependences of the AGN fraction to explore trends with several stellar age indicators. We find no significant differences in the distribution of the rest-frame U - V colour for AGN hosts and inactive galaxies, in agreement with previous results. However, we find significantly shallower 4000 Å breaks in AGN hosts, indicative of younger stellar populations. With the help of a model-independent determination of the extinction, we obtain extinction-corrected U - V colours and light-weighted average stellar ages. We find that AGN hosts have younger stellar populations and higher extinction compared to inactive galaxies with the same stellar mass and at the same redshift. We find a highly significant excess of AGN hosts with Dn(4000) ˜ 1.4 and light-weighted average stellar ages of 300-500 Myr, as well as a deficit of AGN in intrinsic red galaxies. We interpret failure in recognizing these trends in previous studies as a consequence of the balancing effect in observed colours of the age-extinction degeneracy.

  7. LENS MODELS OF HERSCHEL-SELECTED GALAXIES FROM HIGH-RESOLUTION NEAR-IR OBSERVATIONS

    SciTech Connect

    Calanog, J. A.; Cooray, A.; Ma, B.; Casey, C. M.; Fu, Hai; Wardlow, J.; Amber, S.; Baker, A. J.; Baes, M.; Bock, J.; Bourne, N.; Dye, S.; Bussmann, R. S.; Chapman, S. C.; Clements, D. L.; Conley, A.; Dannerbauer, H.; Dunne, L.; Eales, S.; and others

    2014-12-20

    We present Keck-Adaptive Optics and Hubble Space Telescope high resolution near-infrared (IR) imaging for 500 μm bright candidate lensing systems identified by the Herschel Multi-tiered Extragalactic Survey and Herschel Astrophysical Terahertz Large Area Survey. Out of 87 candidates with near-IR imaging, 15 (∼17%) display clear near-IR lensing morphologies. We present near-IR lens models to reconstruct and recover basic rest-frame optical morphological properties of the background galaxies from 12 new systems. Sources with the largest near-IR magnification factors also tend to be the most compact, consistent with the size bias predicted from simulations and previous lensing models for submillimeter galaxies (SMGs). For four new sources that also have high-resolution submillimeter maps, we test for differential lensing between the stellar and dust components and find that the 880 μm magnification factor (μ{sub 880}) is ∼1.5 times higher than the near-IR magnification factor (μ{sub NIR}), on average. We also find that the stellar emission is ∼2 times more extended in size than dust. The rest-frame optical properties of our sample of Herschel-selected lensed SMGs are consistent with those of unlensed SMGs, which suggests that the two populations are similar.

  8. VizieR Online Data Catalog: PM-selected stars of Hercules galaxy (Fabrizio+, 2014)

    NASA Astrophysics Data System (ADS)

    Fabrizio, M.; Raimondo, G.; Brocato, E.; Bellini, A.; Libralato, M.; Testa, V.; Cantiello, M.; Musella, I.; Clementini, G.; Carini, R.; Marconi, M.; Piotto, G.; Ripepi, V.; Buonanno, R.; Sani, E.; Speziali, R.

    2014-08-01

    Discovered in the last decade as overdensities of resolved stars, the ultra-faint dwarfs (UFDs) are among the least luminous, most dark-matter dominated, and most metal-poor galaxies known today. They appear as sparse, loose objects with high mass-to-light ratios. Hercules is the prototype of the UFD galaxies. To date, there are still no firm constraints on its total luminosity due to the difficulty of disentangling Hercules bona-fide stars from the severe Galactic field contamination. To better constrain Hercules properties, we aim at removing foreground and background contaminants in the galaxy field using the proper motions of the Milky Way stars and the colour-colour diagram. We have obtained images of Hercules in the rSloan , BBessel and Uspec bands with the Large Binocular Telescope (LBT) and LBC-BIN mode capabilities. The rSloan new dataset combined with data from the LBT archive span a time baseline of about 5yr, allowing us to measure proper motions of stars in the Hercules direction for the first time. The Uspec data along with existing LBT photometry allowed us to use colour-colour diagram to further remove the field contamination. Description: The Hercules ultra-faint dwarf (UFD) galaxy (J2000 position 16:31:02.0+12:47:25.6) was observed with the Large Binocular Camera (LBC) at the LBT located on Mount Graham in Arizona. The LBC is a wide field imager (4 CCDs, 2Kx4.5K pixels each) with a FoV of ~23'x 23' and a resolution of 0.225"/pix. We employed both archival and proprietary data to have the longest available time baseline. File table2 contains the final catalogue of 528 PM-selected sources. From left to right we report: the source identity (Col. 1), right ascension and declination (Col. 2-3), Uspec, BBessel and rSloan magnitudes with their uncertainty (Col. 4-6), displacement with its uncertainty (Col. 7) (1 data file).

  9. Infrared Spectral Energy Distribution Decomposition of WISE-selected, Hyperluminous Hot Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Fan, Lulu; Han, Yunkun; Nikutta, Robert; Drouart, Guillaume; Knudsen, Kirsten K.

    2016-06-01

    We utilize a Bayesian approach to fit the observed mid-IR-to-submillimeter/millimeter spectral energy distributions (SEDs) of 22 WISE-selected and submillimeter-detected, hyperluminous hot dust-obscured galaxies (Hot DOGs), with spectroscopic redshift ranging from 1.7 to 4.6. We compare the Bayesian evidence of a torus plusgraybody (Torus+GB) model with that of a torus-only (Torus) model and find that the Torus+GB model has higher Bayesian evidence for all 22 Hot DOGs than the torus-only model, which presents strong evidence in favor of the Torus+GB model. By adopting the Torus+GB model, we decompose the observed IR SEDs of Hot DOGs into torus and cold dust components. The main results are as follows. (1) Hot DOGs in our submillimeter-detected sample are hyperluminous ({L}{IR}≥slant {10}13{L}ȯ ), with torus emission dominating the IR energy output. However, cold dust emission is non-negligible, contributing on average ˜ 24% of total IR luminosity. (2) Compared to QSO and starburst SED templates, the median SED of Hot DOGs shows the highest luminosity ratio between mid-IR and submillimeter at rest frame, while it is very similar to that of QSOs at ˜ 10{--}50 μ {{m}}, suggesting that the heating sources of Hot DOGs should be buried AGNs. (3) Hot DOGs have high dust temperatures ({T}{dust}˜ 72 K) and high IR luminosity of cold dust. The {T}{dust}{--}{L}{IR} relation of Hot DOGs suggests that the increase in IR luminosity for Hot DOGs is mostly due to the increase of the dust temperature, rather than dust mass. Hot DOGs have lower dust masses than submillimeter galaxies (SMGs) and QSOs within a similar redshift range. Both high IR luminosity of cold dust and relatively low dust mass in Hot DOGs can be expected by their relatively high dust temperatures. (4) Hot DOGs have high dust-covering factors (CFs), which deviate from the previously proposed trend of the dust CF decreasing with increasing bolometric luminosity. Finally, we can reproduce the observed

  10. Infrared Spectral Energy Distribution Decomposition of WISE-selected, Hyperluminous Hot Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Fan, Lulu; Han, Yunkun; Nikutta, Robert; Drouart, Guillaume; Knudsen, Kirsten K.

    2016-06-01

    We utilize a Bayesian approach to fit the observed mid-IR-to-submillimeter/millimeter spectral energy distributions (SEDs) of 22 WISE-selected and submillimeter-detected, hyperluminous hot dust-obscured galaxies (Hot DOGs), with spectroscopic redshift ranging from 1.7 to 4.6. We compare the Bayesian evidence of a torus plusgraybody (Torus+GB) model with that of a torus-only (Torus) model and find that the Torus+GB model has higher Bayesian evidence for all 22 Hot DOGs than the torus-only model, which presents strong evidence in favor of the Torus+GB model. By adopting the Torus+GB model, we decompose the observed IR SEDs of Hot DOGs into torus and cold dust components. The main results are as follows. (1) Hot DOGs in our submillimeter-detected sample are hyperluminous ({L}{IR}≥slant {10}13{L}ȯ ), with torus emission dominating the IR energy output. However, cold dust emission is non-negligible, contributing on average ∼ 24% of total IR luminosity. (2) Compared to QSO and starburst SED templates, the median SED of Hot DOGs shows the highest luminosity ratio between mid-IR and submillimeter at rest frame, while it is very similar to that of QSOs at ∼ 10{--}50 μ {{m}}, suggesting that the heating sources of Hot DOGs should be buried AGNs. (3) Hot DOGs have high dust temperatures ({T}{dust}∼ 72 K) and high IR luminosity of cold dust. The {T}{dust}{--}{L}{IR} relation of Hot DOGs suggests that the increase in IR luminosity for Hot DOGs is mostly due to the increase of the dust temperature, rather than dust mass. Hot DOGs have lower dust masses than submillimeter galaxies (SMGs) and QSOs within a similar redshift range. Both high IR luminosity of cold dust and relatively low dust mass in Hot DOGs can be expected by their relatively high dust temperatures. (4) Hot DOGs have high dust-covering factors (CFs), which deviate from the previously proposed trend of the dust CF decreasing with increasing bolometric luminosity. Finally, we can reproduce the observed

  11. Revised coordinates for 373 selected objects in the Southern Galaxy Catalogue

    NASA Technical Reports Server (NTRS)

    Spellman, Kathleen; Madore, Barry F.; Helou, George

    1989-01-01

    Improved positions have been determined for 373 galaxies listed in the Southern Galaxy Catalogue of Corwin et al. (1985) as having poor coordinates. The revised coordinates are expected to be good to 6 arcsec (rms) in each coordinate.

  12. X-ray-selected galaxy groups in Boötes

    SciTech Connect

    Vajgel, Bruna; Lopes, Paulo A. A.; Jones, Christine; Forman, William R.; Murray, Stephen S.; Goulding, Andrew; Andrade-Santos, Felipe

    2014-10-10

    We present the X-ray and optical properties of the galaxy groups selected in the Chandra X-Boötes survey. We used follow-up Chandra observations to better define the group sample and their X-ray properties. Group redshifts were measured from the AGN and Galaxy Evolution Survey spectroscopic data. We used photometric data from the NOAO Deep Wide Field Survey to estimate the group richness (N {sub gals}) and the optical luminosity (L {sub opt}). Our final sample comprises 32 systems at z < 1.75 with 14 below z = 0.35. For these 14 systems, we estimate velocity dispersions (σ {sub gr}) and perform a virial analysis to obtain the radii (R {sub 200} and R {sub 500}) and total masses (M {sub 200} and M {sub 500}) for groups with at least 5 galaxy members. We use the Chandra X-ray observations to derive the X-ray luminosity (L{sub X} ). We examine the performance of the group properties σ{sub gr}, L {sub opt}, and L{sub X} , as proxies for the group mass. Understanding how well these observables measure the total mass is important to estimate how precisely the cluster/group mass function is determined. Exploring the scaling relations built with the X-Boötes sample and comparing these with samples from the literature, we find a break in the L{sub X} -M {sub 500} relation at approximately M {sub 500} = 5 × 10{sup 13} M {sub ☉} (for M {sub 500} > 5 × 10{sup 13} M {sub ☉}, M{sub 500}∝L{sub X}{sup 0.61±0.02}, while for M {sub 500} ≤ 5 × 10{sup 13} M {sub ☉}, M{sub 500}∝L{sub X}{sup 0.44±0.05}). Thus, the mass-luminosity relation for galaxy groups cannot be described by the same power law as galaxy clusters. A possible explanation for this break is the dynamical friction, tidal interactions, and projection effects that reduce the velocity dispersion values of the galaxy groups. By extending the cluster luminosity function to the group regime, we predict the number of groups that new X-ray surveys, particularly eROSITA, will detect. Based on our cluster

  13. Bulgeless galaxies at intermediate redshift: Sample selection, color properties, and the existence of powerful active galactic nuclei

    SciTech Connect

    Bizzocchi, Luca; Leonardo, Elvira; Grossi, Marco; Afonso, José; Fernandes, Cristina; Retrê, João; Filho, Mercedes E.; Lobo, Catarina; Griffith, Roger L.; Anton, Sonia; Bell, Eric F.; Brinchmann, Jarle; Henriques, Bruno; Messias, Hugo

    2014-02-10

    We present a catalog of bulgeless galaxies, which includes 19,225 objects selected in four of the deepest, largest multi-wavelength data sets available—COSMOS, AEGIS, GEMS, and GOODS—at intermediate redshift (0.4 ≤ z ≤ 1.0). The morphological classification was provided by the Advanced Camera for Surveys General Catalog (ACS-GC), which used publicly available data obtained with the ACS instrument on the Hubble Space Telescope. Rest-frame photometric quantities were derived using kcorrect. We analyze the properties of the sample and the evolution of pure-disk systems with redshift. Very massive [log (M {sub *}/M {sub ☉}) > 10.5] bulgeless galaxies contribute to ∼30% of the total galaxy population number density at z ≥ 0.7, but their number density drops substantially with decreasing redshift. We show that only a negligible fraction of pure disks appear to be quiescent systems, and red sequence bulgeless galaxies show indications of dust-obscured star formation. X-ray catalogs were used to search for X-ray emission within our sample. After visual inspection and detailed parametric morphological fitting we identify 30 active galactic nuclei (AGNs) that reside in galaxies without a classical bulge. The finding of such peculiar objects at intermediate redshift shows that while AGN growth in merger-free systems is a rare event (0.2% AGN hosts in this sample of bulgeless galaxies), it can indeed happen relatively early in the history of the universe.

  14. The Host Galaxy Properties of Variability Selected AGN in the Pan-STARRS1 Medium Deep Survey

    NASA Astrophysics Data System (ADS)

    Heinis, S.; Gezari, S.; Kumar, S.; Burgett, W. S.; Flewelling, H.; Huber, M. E.; Kaiser, N.; Wainscoat, R. J.; Waters, C.

    2016-07-01

    We study the properties of 975 active galactic nuclei (AGNs) selected by variability in the Pan-STARRS1 Medium deep Survey. Using complementary multi-wavelength data from the ultraviolet to the far-infrared, we use spectral energy distribution fitting to determine the AGN and host properties at z < 1 and compare to a well-matched control sample. We confirm the trend previously observed: that the variability amplitude decreases with AGN luminosity, but we also observe that the slope of this relation steepens with wavelength, resulting in a “redder when brighter” trend at low luminosities. Our results show that AGNs are hosted by more massive hosts than control sample galaxies, while the rest frame dust-corrected NUV ‑ r color distribution of AGN hosts is similar to control galaxies. We find a positive correlation between the AGN luminosity and star formation rate (SFR), independent of redshift. AGN hosts populate the entire range of SFRs within and outside of the Main Sequence of star-forming galaxies. Comparing the distribution of AGN hosts and control galaxies, we show that AGN hosts are less likely to be hosted by quiescent galaxies and more likely to be hosted by Main Sequence or starburst galaxies.

  15. The Munich Near-Infrared Cluster Survey - IX. Galaxy evolution to z ~ 2 from optically selected catalogues†‡

    NASA Astrophysics Data System (ADS)

    Feulner, Georg; Goranova, Yuliana; Hopp, Ulrich; Gabasch, Armin; Bender, Ralf; Botzler, Christine S.; Drory, Niv

    2007-06-01

    We present B-, R- and I-band-selected galaxy catalogues based on the Munich Near-Infrared Cluster Survey (MUNICS) which, together with the previously used K-selected sample, serve as an important probe of galaxy evolution in the redshift range 0 <~ z <~ 2. Furthermore, used in comparison they are ideally suited to study selection effects in extragalactic astronomy. The construction of the B-, R- and I-selected photometric catalogues, containing ~9000, ~9000 and ~6000 galaxies, respectively, is described in detail. The catalogues reach 50 per cent completeness limits for point sources of B ~= 24.5 mag, R ~= 23.5 mag and I ~= 22.5 mag and cover an area of about 0.3deg2. Photometric redshifts are derived for all galaxies with an accuracy of δz/(1 + z) ~= 0.057, very similar to the K-selected sample. Galaxy number counts in the B, V, R, I, J and K bands demonstrate the quality of the data set. The rest-frame colour distributions of galaxies at different selection bands and redshifts suggest that the most-massive galaxies have formed the bulk of their stellar population at earlier times and are essentially in place at redshift unity. We investigate the influence of selection band and environment on the specific star formation rate (SSFR). We find that K-band selection indeed comes close to selection in stellar mass, while B-band selection purely selects galaxies in SFR. We use a galaxy group catalogue constructed on the K-band-selected MUNICS sample to study possible differences of the SSFR between the field and the group environment, finding a marginally lower average SSFR in groups as compared to the field, especially at lower redshifts. The field-galaxy luminosity function in the B and R band as derived from the R-selected sample evolves out to z ~= 2 in the sense that the characteristic luminosity increases but the number density decreases. This effect is smaller at longer rest-frame wavelengths and gets more pronounced at shorter wavelengths. Parametrizing the

  16. Selection and mid-infrared spectroscopy of ultraluminous star-forming galaxies at z ∼ 2

    SciTech Connect

    Fang, Guanwen; Kong, Xu; Chen, Yang; Lin, Xuanbin; Huang, Jia-Sheng; Willner, S. P.; Wang, Tao E-mail: jhuang@cfa.harvard.edu

    2014-02-01

    Starting from a sample of 24 μm sources in the Extended Groth Strip, we use 3.6-8 μm color criteria to select ultraluminous infrared galaxies (ULIRGs) at z ∼ 2. Spectroscopy from 20-38 μm of 14 objects verifies their nature and gives their redshifts. Multi-wavelength data for these objects imply stellar masses >10{sup 11} M {sub ☉} and star formation rates ≥410 M {sub ☉} yr{sup –1}. Four objects of this sample observed at 1.6 μm (rest-frame visible) with Hubble Space Telescope/WFC3 show diverse morphologies, suggesting that multiple formation processes create ULIRGs. Of the 14 objects, 4 show signs of active galactic nuclei, but the luminosity appears to be dominated by star formation in all cases.

  17. HST rest-frame optical characteristics of WISE-selected galaxies at z>1.7

    NASA Astrophysics Data System (ADS)

    Petty, Sara M.; Blain, Andrew; Bridge, Carrie; Paine, Jennie; Farrah, Duncan; Jarrett, Tom; Benford, Dominic J.; Eisenhardt, Peter R.; Lake, Sean E.; Lazarova, Mariana; Moustakas, Leonidas A.; Stanford, S. Adam; Tsai, Chao-Wei; Wright, Edward L.; WISE

    2015-01-01

    We present resolved H-band images of 12 Wide-field Infrared Survey Explorer color-selected galaxies with confirmed redshifts 1.8 to 2.7, probing the rest-frame optical at ~1 kpc scales. Our sample was originally selected for HST imaging due to their AGN-like, red WISE colors (Eisenhardt et al. 2012), and includes six with extended Ly-α emission. The latter are thought to be a part of a very rare population of galaxies caught in a short-lived 'blowout phase' which is thought to cause the extended Ly-α emission in blobs (LABs; Bridge, et al. 2013). The environments in the H-band represent a diverse sample, and do not reveal any strong relation with a blowout process without more resolved wavelength coverage. The morphologies appear as multiple interacting nuclei, or a single undisturbed object. We analyze, in detail, two objects, including a discussion on individual components in possible major merger and/or the blowout phase. Also, we analyze the global properties of the sources using the unresolved photometry from WISE and Herschel PACS along with the H-band. Comparisons with dust obscured galaxies (DOGs from Bussman et al. 2009) at the same redshift, reveal color signatures stemming from a different phase of dusty starburst+AGN. Our sample show H-[12] colors 4.8-7.8 with a mean of 6.2. The DOGs are bluer with H-[12] colors 3.9-7.5 and mean of 5.2. The H-[12] v. [12]-[22] colorspace reveals a distinct population: only two DOGs reside on the same region. In addition, the reddest [12]-[22] colors are the bluest in H-[12] for the respective samples. Herschel/PACS "red" (130-210 μm) filter images give a range in flux densities from 0.04-0.1 Jy. These preliminary results indicate a distinct formation stage for dusty starburst+AGN, which play a key role in the continuum of ULIRG properties at high-z.

  18. The Evolution of Early-type Field Galaxies Selected from a NICMOS Map of the Hubble Deep Field North

    SciTech Connect

    Somerville, R; Stanford, S A; Budavari, T; Conselice, C J

    2004-03-03

    The redshift distribution of well-defined samples of distant early-type galaxies offers a means to test the predictions of monolithic and hierarchical galaxy formation scenarios. NICMOS maps of the entire Hubble Deep Field North in the F110W and F160W filters, when combined with the available WFPC2 data, allow us to calculate photometric redshifts and determine the morphological appearance of galaxies at rest-frame optical wavelengths out to z {approx} 2.5. Here we report results for two subsamples of early-type galaxies, defined primarily by their morphologies in the F160W band, which were selected from the NICMOS data down to H{sub 160AB} < 24.0. A primary subsample is defined as the 34 galaxies with early-type galaxy morphologies and early-type galaxy spectral energy distributions. The secondary subsample is defined as those 42 objects which have early-type galaxy morphologies with non-early type galaxy spectral energy distributions. The observed redshift distributions of our two early-type samples do not match that predicted by a monolithic collapse model, which shows an overabundance at z > 1.5. A (V/V{sub max}) test confirms this result. When the effects of passive luminosity evolution are included in the calculation, the mean value of Vmax for the primary sample is 0.22 {+-} 0.05, and 0.31 {+-} 0.04 for all the early-types. A hierarchical formation model better matches the redshift distribution of the HDF-N early-types at z > 1.5, but still does not adequately describe the observed early-types. The hierarchical model predicts significantly bluer colors on average than the observed early-type colors, and underpredicts the observed number of early-types at z {approx} 2. Though the observed redshift distribution of the early-type galaxies in our HDF-NICMOS sample is better matched by a hierarchical galaxy formation model, the reliability of this conclusion is tempered by the restricted sampling area and relatively small number of early-type galaxies selected by

  19. A WIDE AREA SURVEY FOR HIGH-REDSHIFT MASSIVE GALAXIES. II. NEAR-INFRARED SPECTROSCOPY OF BzK-SELECTED MASSIVE STAR-FORMING GALAXIES

    SciTech Connect

    Onodera, Masato; Daddi, Emanuele; Renzini, Alvio; Kong Xu; Cimatti, Andrea; Broadhurst, Tom; Alexander, Dave M.

    2010-05-20

    Results are presented from near-infrared spectroscopic observations of a sample of BzK-selected, massive star-forming galaxies (sBzKs) at 1.5 < z < 2.3 that were obtained with OHS/CISCO at the Subaru telescope and with SINFONI at the Very Large Telescope. Among the 28 sBzKs observed, H{alpha} emission was detected in 14 objects, and for 11 of them the [N II] {lambda}6583 flux was also measured. Multiwavelength photometry was also used to derive stellar masses and extinction parameters, whereas H{alpha} and [N II] emissions have allowed us to estimate star formation rates (SFRs), metallicities, ionization mechanisms, and dynamical masses. In order to enforce agreement between SFRs from H{alpha} with those derived from rest-frame UV and mid-infrared, additional obscuration for the emission lines (that originate in H II regions) was required compared to the extinction derived from the slope of the UV continuum. We have also derived the stellar mass-metallicity relation, as well as the relation between stellar mass and specific SFR (SSFR), and compared them to the results in other studies. At a given stellar mass, the sBzKs appear to have been already enriched to metallicities close to those of local star-forming galaxies of similar mass. The sBzKs presented here tend to have higher metallicities compared to those of UV-selected galaxies, indicating that near-infrared selected galaxies tend to be a chemically more evolved population. The sBzKs show SSFRs that are systematically higher, by up to {approx}2 orders of magnitude, compared to those of local galaxies of the same mass. The empirical correlations between stellar mass and metallicity, and stellar mass and SSFR are then compared with those of evolutionary population synthesis models constructed either with the simple closed-box assumption, or within an infall scenario. Within the assumptions that are built-in such models, it appears that a short timescale for the star formation ({approx_equal}100 Myr) and large

  20. The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: selecting emission line galaxies using the Fisher discriminant

    NASA Astrophysics Data System (ADS)

    Raichoor, A.; Comparat, J.; Delubac, T.; Kneib, J.-P.; Yèche, Ch.; Zou, H.; Abdalla, F. B.; Dawson, K.; de la Macorra, A.; Fan, X.; Fan, Z.; Jiang, Z.; Jing, Y.; Jouvel, S.; Lang, D.; Lesser, M.; Li, C.; Ma, J.; Newman, J. A.; Nie, J.; Palanque-Delabrouille, N.; Percival, W. J.; Prada, F.; Shen, S.; Wang, J.; Wu, Z.; Zhang, T.; Zhou, X.; Zhou, Z.

    2016-01-01

    We present a new selection technique of producing spectroscopic target catalogues for massive spectroscopic surveys for cosmology. This work was conducted in the context of the extended Baryon Oscillation Spectroscopic Survey (eBOSS), which will use ~200 000 emission line galaxies (ELGs) at 0.6 ≤ zspec ≤ 1.0 to obtain a precise baryon acoustic oscillation measurement. Our proposed selection technique is based on optical and near-infrared broad-band filter photometry. We used a training sample to define a quantity, the Fisher discriminant (linear combination of colours), which correlates best with the desired properties of the target: redshift and [Oii] flux. The proposed selections are simply done by applying a cut on magnitudes and this Fisher discriminant. We used public data and dedicated SDSS spectroscopy to quantify the redshift distribution and [Oii] flux of our ELG target selections. We demonstrate that two of our selections fulfil the initial eBOSS/ELG redshift requirements: for a target density of 180 deg-2, ~70% of the selected objects have 0.6 ≤ zspec ≤ 1.0 and only ~1% of those galaxies in the range 0.6 ≤ zspec ≤ 1.0 are expected to have a catastrophic zspec estimate. Additionally, the stacked spectra and stacked deep images for those two selections show characteristic features of star-forming galaxies. The proposed approach using the Fisher discriminant could, however, be used to efficiently select other galaxy populations, based on multi-band photometry, providing that spectroscopic information isavailable. This technique could thus be useful for other future massive spectroscopic surveys such as PFS, DESI, and 4MOST.

  1. Radio haloes in Sunyaev-Zel'dovich-selected clusters of galaxies: the making of a halo?

    NASA Astrophysics Data System (ADS)

    Bonafede, A.; Intema, H.; Brüggen, M.; Vazza, F.; Basu, K.; Sommer, M.; Ebeling, H.; de Gasperin, F.; Röttgering, H. J. A.; van Weeren, R. J.; Cassano, R.

    2015-12-01

    Radio haloes are synchrotron radio sources detected in some massive galaxy clusters. Their size of Mpc indicates that (re)acceleration processes are taking place in the host cluster. X-ray catalogues of galaxy clusters have been used in the past to search for radio haloes and to understand their connection with cluster-cluster mergers and with the thermal component of the intracluster medium. More recently, the Sunyaev-Zel'dovich effect has been proven to be a better route to search for massive clusters in a wider redshift range. With the aim of discovering new radio haloes and understanding their connection with cluster-cluster mergers, we have selected the most massive clusters from the Planck early source catalogue and we have observed with the Giant Metrewave Radio Telescope at 323 MHz those objects for which deep observations were not available. We have discovered new peculiar radio emission in three of the observed clusters, finding (i) a radio halo in the cluster RXCJ0949.8+1708, (ii) extended emission in Abell 1443 that we classify as a radio halo plus a radio relic, with a bright filament embedded in the radio halo, and (iii) low-power radio emission in CIZA J1938.3+5409 that is ten times below the radio-X-ray correlation and represents the first direct detection of the radio emission in the `upper-limit' region of the radio-X-ray diagram. We discuss the properties of these new radio haloes in the framework of theoretical models for the radio emission.

  2. A Survey of Distant Clusters of Galaxies Selected by X-Rays

    NASA Technical Reports Server (NTRS)

    McNamara, Brian

    1997-01-01

    I will discuss the results of a new survey of X-ray selected, distant clusters of galaxies that has been undertaken by our group at.CfA (Vikhlinin, McNamara, Forman, Jones). We have analyzed the inner 17.5 arcminute region of roughly 650 ROSAT PSPC images of high latitude fields to compile a complete, flux-limited sample of clusters with a mean flux limit roughly 20 times more sensitive than the Einstein Medium Sensitivity Survey. The goal of our survey, which presently contains 233 extended X-ray sources, is to study cluster evolution over cosmological timescales. We have obtained optical images for nearly all of the faintest sources using the 1.2 m telescope of the Fred L. Whipple Observatory, and when including POSS images of the brighter sources, we have nearly completed the identification of all of the extended sources. Roughly 80% of the sources were identified as clusters of galaxies. We have measured redshifts for 42 clusters using the MMT, and including additional measurements from the literature, roughly 70 clusters in our catalog have spectroscopic redshifts. Using CCD photometry and spectroscopic redshifts, we have determined a magnitude-redshift relation which will allow redshifts of the remaining clusters in our sample to be determined photometrically to within a delta z over z of roughly ten percent. I will discuss the Log(N)-Log(S) relation for our sample and compare it to other determinations. In addition, I will discuss the evolution of core radii of clusters.

  3. A red envelope around a dominant elliptical galaxy in an X-ray selected poor cluster

    NASA Technical Reports Server (NTRS)

    Maccagni, D.; Garilli, B.; Gioia, I. M.; Maccacaro, T.; Vettolani, G.

    1988-01-01

    A photometric and spectroscopic study of the optical counterpart of the X-ray source 1E 1111.9-3754 has revealed a poor cluster of galaxies dominated by a very luminous giant elliptical. Three-color surface photometry of this galaxy shows that the elliptical body is surrounded by a large envelope with colors redder than the galaxy. The formation of this system in a high velocity dispersion poor cluster is briefly discussed.

  4. Spectrophotometric study in the near-IR of a sample of H alpha-selected galaxies with active star formation at z = 0.84

    NASA Astrophysics Data System (ADS)

    Sánchez de Miguel, A.; Gallego, J.; Villar, V.; Zamorano, J.; Acosta, J.; Pérez-Gonzalez, P. G.; Barro, G.

    2011-11-01

    In this work we present the results of the spectroscopic analysis in the near-infrared J band of a sample of 48 star forming galaxies at z = 0.84. Half of the sample was selected by a narrow-band filter tuned to Hα at that redshift and the other half was selected by photometric redshifts at the same redshift. We provide Hα luminosities and star formation rates for all galaxies at that redshift. We were able to estimate metallicities from [NII]6584 Å for a sub sample of eight galaxies, two of the galaxies were from neckband selection. To analyze their physical properties we have computed their sizes, colors, stellar masses, extinctions and other parameters available in literature and in the Rainbow database. In particular the dependence of the stellar mass with the specific star formation rate and metallicity have been studied and compared with the results of other samples of galaxies at several redshifts. For a fixed mass, the metallicities of our galaxies are compatible than those similar at the local Universe, although with higher dispersion. This fact implies that selection in Hα is less biased than a selection in UV, since it includes galaxies with more evolved populations besides objects dominated by star formation. The comparison of the observed properties with models of evolution leads us to think that z = 0.8 star-forming galaxies have already undergone significant changes and begin to developed in a more passive way.

  5. USING THE 1.6 {mu}m BUMP TO STUDY REST-FRAME NEAR-INFRARED-SELECTED GALAXIES AT REDSHIFT 2

    SciTech Connect

    Sorba, Robert; Sawicki, Marcin

    2010-10-01

    We explore the feasibility and limitations of using the 1.6 {mu}m bump as a photometric redshift indicator and selection technique, and use it to study the rest-frame H-band galaxy luminosity and stellar mass functions (SMFs) at redshift z {approx} 2. We use publicly available Spitzer/IRAC images in the GOODS fields and find that color selection in the IRAC bandpasses alone is comparable in completeness and contamination to BzK selection. We find that the shape of the 1.6 {mu}m bump is robust, and photometric redshifts are not greatly affected by choice of model parameters. Comparison with spectroscopic redshifts shows photometric redshifts to be reliable. We create a rest-frame NIR-selected catalog of galaxies at z {approx} 2 and construct a galaxy SMF. Comparisons with other SMFs at approximately the same redshift but determined using shorter wavelengths show good agreement. This agreement suggests that selection at bluer wavelengths does not miss a significant amount of stellar mass in passive galaxies. Comparison with SMFs at other redshifts shows evidence for the downsizing scenario of galaxy evolution. We conclude by pointing out the potential for using the 1.6 {mu}m bump technique to select high-redshift galaxies with the JWST, whose {lambda}>0.6 {mu}m coverage will not be well suited to selecting galaxies using techniques that require imaging at shorter wavelengths.

  6. Keck Deep Fields. IV. Luminosity-dependent Clustering and Galaxy Downsizing in UV-selected Galaxies at z = 4, 3, and 2

    NASA Astrophysics Data System (ADS)

    Savoy, Jonathan; Sawicki, Marcin; Thompson, David; Sato, Taro

    2011-08-01

    We investigate the luminosity-dependent clustering of rest-frame UV-selected galaxies at z ~ 4, 3, 2.2, and 1.7 in the Keck Deep Fields, which are complete to {R} = 27 and cover 169 arcmin2. We find that at z ~ 4 and 3, UV-bright galaxies cluster more strongly than UV-faint ones, but at z ~ 2.2 and 1.7, the UV-bright galaxies are no longer the most strongly clustered. We derive mass estimates for objects in our sample by comparing our measurements to the predicted clustering of dark matter halos in the Millennium Simulation. From these estimates, we infer relationships between halo mass and star formation rate (SFR), and find that the most massive dark matter halos in our sample host galaxies with high SFRs (M 1700 < -20, or >50 M sun yr-1) at z ~ 3 and 4, moderate SFRs (-20 < M 1700 < -19, or ~20 M sun yr-1) at z ~ 2.2, and lower SFRs (-19 < M 1700 < -18, or ~2 M sun yr-1) at z ~ 1.7. We believe our measurements may provide a new line of evidence for galaxy downsizing by extending that concept from stellar to halo mass. We also find that the objects with blue UV colors in our sample are much more strongly clustered than those with red UV colors, and we propose that this may be due to the presence of the 2175 Å dust absorption bump in more massive halos, which contain the older stellar populations and dust needed to produce the feature. The relatively small area covered by the survey means that the absolute values of the correlation lengths and halo masses we derive are heavily dependent on the "integral constraint" correction, but the uniformly deep coverage across a large-redshift interval allows us to detect several important trends that are independent of this correction. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

  7. KECK DEEP FIELDS. IV. LUMINOSITY-DEPENDENT CLUSTERING AND GALAXY DOWNSIZING IN UV-SELECTED GALAXIES AT z = 4, 3, AND 2

    SciTech Connect

    Savoy, Jonathan; Sawicki, Marcin; Sato, Taro; Thompson, David

    2011-08-20

    We investigate the luminosity-dependent clustering of rest-frame UV-selected galaxies at z {approx} 4, 3, 2.2, and 1.7 in the Keck Deep Fields, which are complete to R = 27 and cover 169 arcmin{sup 2}. We find that at z {approx} 4 and 3, UV-bright galaxies cluster more strongly than UV-faint ones, but at z {approx} 2.2 and 1.7, the UV-bright galaxies are no longer the most strongly clustered. We derive mass estimates for objects in our sample by comparing our measurements to the predicted clustering of dark matter halos in the Millennium Simulation. From these estimates, we infer relationships between halo mass and star formation rate (SFR), and find that the most massive dark matter halos in our sample host galaxies with high SFRs (M{sub 1700} < -20, or >50 M{sub sun} yr{sup -1}) at z {approx} 3 and 4, moderate SFRs (-20 < M{sub 1700} < -19, or {approx}20 M{sub sun} yr{sup -1}) at z {approx} 2.2, and lower SFRs (-19 < M{sub 1700} < -18, or {approx}2 M{sub sun} yr{sup -1}) at z {approx} 1.7. We believe our measurements may provide a new line of evidence for galaxy downsizing by extending that concept from stellar to halo mass. We also find that the objects with blue UV colors in our sample are much more strongly clustered than those with red UV colors, and we propose that this may be due to the presence of the 2175 A dust absorption bump in more massive halos, which contain the older stellar populations and dust needed to produce the feature. The relatively small area covered by the survey means that the absolute values of the correlation lengths and halo masses we derive are heavily dependent on the 'integral constraint' correction, but the uniformly deep coverage across a large-redshift interval allows us to detect several important trends that are independent of this correction.

  8. An IR-Selected Galaxy Cluster at Z=1.41

    SciTech Connect

    Stanford, S A; Eisenhardt, P R; Brodwin, M; Gonzalez, A H; Stern, D; Jannuzi, B; Dey, A; Brown, M I; McKenzie, E; Elston, R

    2006-03-09

    We report the discovery of a galaxy cluster at z = 1.41. ISCS J143809+341419 was found in the Spitzer/IRAC Shallow Survey of the Bootes field in the NOAO Deep Wide-Field Survey carried out by IRAC. The cluster candidate was initially identified as a high density region of objects with photometric redshifts in the range 1.3 < z < 1.5. Optical spectroscopy of a limited number of objects in the region shows that 5 galaxies within a {approx}120 arcsec diameter region lie at z = 1.41 {+-} 0.01. Most of these member galaxies have broad-band colors consistent with the expected spectral energy distribution of a passively-evolving elliptical galaxy formed at high redshift. The redshift of ISCS J143809+341419 is the highest currently known for a spectroscopically-confirmed cluster of galaxies.

  9. ASSEMBLY OF THE RED SEQUENCE IN INFRARED-SELECTED GALAXY CLUSTERS FROM THE IRAC SHALLOW CLUSTER SURVEY

    SciTech Connect

    Snyder, Gregory F.; Brodwin, Mark; Mancone, Conor M.; Gonzalez, Anthony H.; Zeimann, Gregory R.; Stanford, S. A.; Stern, Daniel; Eisenhardt, Peter R. M.; Brown, Michael J. I.; Dey, Arjun; Jannuzi, Buell; Perlmutter, Saul

    2012-09-10

    We present results for the assembly and star formation histories (SFHs) of massive ({approx}L*) red sequence galaxies (RSGs) in 11 spectroscopically confirmed, infrared-selected galaxy clusters at 1.0 < z < 1.5, the precursors to present-day massive clusters with M {approx} 10{sup 15} M{sub Sun }. Using rest-frame optical photometry, we investigate evolution in the color and scatter of the RSG population, comparing with models of possible SFHs. In contrast to studies of central cluster galaxies at lower redshift (z < 1), these data are clearly inconsistent with the continued evolution of stars formed and assembled primarily at a single, much earlier time. Specifically, we find that the colors of massive cluster galaxies at z Almost-Equal-To 1.5 imply that the bulk of star formation occurred at z {approx} 3, whereas by z Almost-Equal-To 1 their colors imply formation at z {approx} 2; therefore these galaxies exhibit approximately the same luminosity-weighted stellar age at 1 < z < 1.5. This likely reflects star formation that occurs over an extended period, the effects of significant progenitor bias, or both. Our results generally indicate that massive cluster galaxy populations began forming a significant mass of stars at z {approx}> 4, contained some red spheroids by z Almost-Equal-To 1.5, and were actively assembling much of their final mass during 1 < z < 2 in the form of younger stars. Qualitatively, the slopes of the cluster color-magnitude relations are consistent with no significant evolution relative to local clusters.

  10. Tidally triggered star formation in gravitationally interacting galaxies and selected work in optical instrumentation

    NASA Astrophysics Data System (ADS)

    Woods, Deborah Freedman

    In the first part of this thesis I present studies of tidally triggered star formation in pairs of gravitationally interacting galaxies. I use spectroscopic and photometric observations of local systems to demonstrate that triggered star formation depends both on intrinsic galaxy properties and on relative properties of the system. Minor galaxy interactions, where the luminosity ratio of the galaxies exceeds about six, produce triggered star formation only in the lower luminosity companion. In interactions between galaxies of similar luminosity, the blue galaxies exhibit tidally triggered star formation, but the red galaxies do not. I measure the strength, frequency, and timescale of gravitational tidal interactions between galaxy pairs in a complete spectroscopic survey at redshifts 0.08 to 0.38. A third of the galaxies with young stellar populations interacting with a companion of similar luminosity experience enhanced star formation activity. However, the most extreme bursts of triggered star formation are rare and short lived. The typical duration for enhanced star formation in interacting galaxies is of order 300 Myr. In the second part of this thesis I describe the development of optical instrumentation in support of large spectroscopic surveys. I analyze the effects of flexure in the Binospec spectrograph, a multi-object spectrograph for the 6.5-meter MMT telescope at Mt. Hopkins, AZ. I design the active flexure control system and the calibration system, two physically distinct systems that together will enable accurate and stable spectro-photometric calibration. Improvements to telescope collimation and mirror support provide additional benefit to spectroscopic surveys through superior image quality and spectrograph efficiency. I design and build a Shack-Hartmann wavefront sensor for the 1.5-meter Tillinghast telescope at Mount Hopkins, AZ. The wavefront sensor and accompanying software serve as valuable tools for measuring and correcting for optical

  11. redMaGiC: selecting luminous red galaxies from the DES Science Verification data

    NASA Astrophysics Data System (ADS)

    Rozo, E.; Rykoff, E. S.; Abate, A.; Bonnett, C.; Crocce, M.; Davis, C.; Hoyle, B.; Leistedt, B.; Peiris, H. V.; Wechsler, R. H.; Abbott, T.; Abdalla, F. B.; Banerji, M.; Bauer, A. H.; Benoit-Lévy, A.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Rosell, A. Carnero; Carollo, D.; Kind, M. Carrasco; Carretero, J.; Castander, F. J.; Childress, M. J.; Cunha, C. E.; D'Andrea, C. B.; Davis, T.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Neto, A. Fausti; Flaugher, B.; Fosalba, P.; Frieman, J.; Gaztanaga, E.; Gerdes, D. W.; Glazebrook, K.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D. J.; Jarvis, M.; Kim, A. G.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Lidman, C.; Lima, M.; Maia, M. A. G.; March, M.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol, R. C.; Nord, B.; O'Neill, C. R.; Ogando, R.; Plazas, A. A.; Romer, A. K.; Roodman, A.; Sako, M.; Sanchez, E.; Santiago, B.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Thaler, J.; Thomas, D.; Uddin, S.; Vikram, V.; Walker, A. R.; Wester, W.; Zhang, Y.; da Costa, L. N.

    2016-09-01

    We introduce redMaGiC, an automated algorithm for selecting Luminous Red Galaxies (LRGs). The algorithm was specifically developed to minimize photometric redshift uncertainties in photometric large-scale structure studies. redMaGiC achieves this by self-training the color-cuts necessary to produce a luminosity-thresholded LRG sample of constant comoving density. We demonstrate that redMaGiC photozs are very nearly as accurate as the best machine-learning based methods, yet they require minimal spectroscopic training, do not suffer from extrapolation biases, and are very nearly Gaussian. We apply our algorithm to Dark Energy Survey (DES) Science Verification (SV) data to produce a redMaGiC catalog sampling the redshift range $z\\in[0.2,0.8]$. Our fiducial sample has a comoving space density of $10^{-3}\\ (h^{-1} Mpc)^{-3}$, and a median photoz bias ($z_{spec}-z_{photo}$) and scatter $(\\sigma_z/(1+z))$ of 0.005 and 0.017 respectively. The corresponding $5\\sigma$ outlier fraction is 1.4%. We also test our algorithm with Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) and Stripe 82 data, and discuss how spectroscopic training can be used to control photoz biases at the 0.1% level.

  12. redMaGiC: Selecting Luminous Red Galaxies from the DES Science Verification Data

    NASA Astrophysics Data System (ADS)

    Rozo, E.; Rykoff, E. S.; Abate, A.; Bonnett, C.; Crocce, M.; Davis, C.; Hoyle, B.; Leistedt, B.; Peiris, H. V.; Wechsler, R. H.; Abbott, T.; Abdalla, F. B.; Banerji, M.; Bauer, A. H.; Benoit-Lévy, A.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Rosell, A. Carnero; Carollo, D.; Kind, M. Carrasco; Carretero, J.; Castander, F. J.; Childress, M. J.; Cunha, C. E.; D'Andrea, C. B.; Davis, T.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Neto, A. Fausti; Flaugher, B.; Fosalba, P.; Frieman, J.; Gaztanaga, E.; Gerdes, D. W.; Glazebrook, K.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D. J.; Jarvis, M.; Kim, A. G.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Lidman, C.; Lima, M.; Maia, M. A. G.; March, M.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol, R. C.; Nord, B.; O'Neill, C. R.; Ogando, R.; Plazas, A. A.; Romer, A. K.; Roodman, A.; Sako, M.; Sanchez, E.; Santiago, B.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Thaler, J.; Thomas, D.; Uddin, S.; Vikram, V.; Walker, A. R.; Wester, W.; Zhang, Y.; da Costa, L. N.

    2016-05-01

    We introduce redMaGiC, an automated algorithm for selecting Luminous Red Galaxies (LRGs). The algorithm was specifically developed to minimize photometric redshift uncertainties in photometric large-scale structure studies. redMaGiC achieves this by self-training the color-cuts necessary to produce a luminosity-thresholded LRG sample of constant comoving density. We demonstrate that redMaGiC photo-zs are very nearly as accurate as the best machine-learning based methods, yet they require minimal spectroscopic training, do not suffer from extrapolation biases, and are very nearly Gaussian. We apply our algorithm to Dark Energy Survey (DES) Science Verification (SV) data to produce a redMaGiC catalog sampling the redshift range z ∈ [0.2, 0.8]. Our fiducial sample has a comoving space density of 10-3 (h-1Mpc)-3, and a median photo-z bias (zspec - zphoto) and scatter (σz/(1 + z)) of 0.005 and 0.017 respectively. The corresponding 5σ outlier fraction is 1.4%. We also test our algorithm with Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) and Stripe 82 data, and discuss how spectroscopic training can be used to control photo-z biases at the 0.1% level.

  13. redMaGiC. Selecting Luminous Red Galaxies from the DES Science Verification Data

    SciTech Connect

    Rozo, E.

    2015-07-20

    We introduce redMaGiC, an automated algorithm for selecting Luminous Red Galaxies (LRGs). The algorithm was developed to minimize photometric redshift uncertainties in photometric large-scale structure studies. redMaGiC achieves this by self-training the color-cuts necessary to produce a luminosity-thresholded LRG sam- ple of constant comoving density. Additionally, we demonstrate that redMaGiC photo-zs are very nearly as accurate as the best machine-learning based methods, yet they require minimal spectroscopic training, do not suffer from extrapolation biases, and are very nearly Gaussian. We apply our algorithm to Dark Energy Survey (DES) Science Verification (SV) data to produce a redMaGiC catalog sampling the redshift range z ϵ [0.2,0.8]. Our fiducial sample has a comoving space density of 10-3 (h-1Mpc)-3, and a median photo-z bias (zspec zphoto) and scatter (σz=(1 + z)) of 0.005 and 0.017 respectively.The corresponding 5σ outlier fraction is 1.4%. We also test our algorithm with Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) and Stripe 82 data, and discuss how spectroscopic training can be used to control photo-z biases at the 0.1% level.

  14. redMaGiC: selecting luminous red galaxies from the DES Science Verification data

    NASA Astrophysics Data System (ADS)

    Rozo, E.; Rykoff, E. S.; Abate, A.; Bonnett, C.; Crocce, M.; Davis, C.; Hoyle, B.; Leistedt, B.; Peiris, H. V.; Wechsler, R. H.; Abbott, T.; Abdalla, F. B.; Banerji, M.; Bauer, A. H.; Benoit-Lévy, A.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Rosell, A. Carnero; Carollo, D.; Kind, M. Carrasco; Carretero, J.; Castander, F. J.; Childress, M. J.; Cunha, C. E.; D'Andrea, C. B.; Davis, T.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Neto, A. Fausti; Flaugher, B.; Fosalba, P.; Frieman, J.; Gaztanaga, E.; Gerdes, D. W.; Glazebrook, K.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D. J.; Jarvis, M.; Kim, A. G.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Lidman, C.; Lima, M.; Maia, M. A. G.; March, M.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol, R. C.; Nord, B.; O'Neill, C. R.; Ogando, R.; Plazas, A. A.; Romer, A. K.; Roodman, A.; Sako, M.; Sanchez, E.; Santiago, B.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Thaler, J.; Thomas, D.; Uddin, S.; Vikram, V.; Walker, A. R.; Wester, W.; Zhang, Y.; da Costa, L. N.

    2016-09-01

    We introduce redMaGiC, an automated algorithm for selecting luminous red galaxies (LRGs). The algorithm was specifically developed to minimize photometric redshift uncertainties in photometric large-scale structure studies. redMaGiC achieves this by self-training the colour cuts necessary to produce a luminosity-thresholded LRG sample of constant comoving density. We demonstrate that redMaGiC photo-zs are very nearly as accurate as the best machine learning-based methods, yet they require minimal spectroscopic training, do not suffer from extrapolation biases, and are very nearly Gaussian. We apply our algorithm to Dark Energy Survey (DES) Science Verification (SV) data to produce a redMaGiC catalogue sampling the redshift range z ∈ [0.2, 0.8]. Our fiducial sample has a comoving space density of 10-3 (h-1 Mpc)-3, and a median photo-z bias (zspec - zphoto) and scatter (σz/(1 + z)) of 0.005 and 0.017, respectively. The corresponding 5σ outlier fraction is 1.4 per cent. We also test our algorithm with Sloan Digital Sky Survey Data Release 8 and Stripe 82 data, and discuss how spectroscopic training can be used to control photo-z biases at the 0.1 per cent level.

  15. A Principle Component Analysis of Galaxy Properties from a Large, Gas-Selected Sample

    DOE PAGESBeta

    Chang, Yu-Yen; Chao, Rikon; Wang, Wei-Hao; Chen, Pisin

    2012-01-01

    Disney emore » t al. (2008) have found a striking correlation among global parameters of H i -selected galaxies and concluded that this is in conflict with the CDM model. Considering the importance of the issue, we reinvestigate the problem using the principal component analysis on a fivefold larger sample and additional near-infrared data. We use databases from the Arecibo Legacy Fast Arecibo L -band Feed Array Survey for the gas properties, the Sloan Digital Sky Survey for the optical properties, and the Two Micron All Sky Survey for the near-infrared properties. We confirm that the parameters are indeed correlated where a single physical parameter can explain 83% of the variations. When color ( g - i ) is included, the first component still dominates but it develops a second principal component. In addition, the near-infrared color ( i - J ) shows an obvious second principal component that might provide evidence of the complex old star formation. Based on our data, we suggest that it is premature to pronounce the failure of the CDM model and it motivates more theoretical work.« less

  16. MOIRCS DEEP SURVEY. VI. NEAR-INFRARED SPECTROSCOPY OF K-SELECTED STAR-FORMING GALAXIES AT z {approx} 2

    SciTech Connect

    Yoshikawa, Tomohiro; Akiyama, Masayuki; Kajisawa, Masaru; Tokoku, Chihiro; Yamada, Toru; Ichikawa, Takashi; Alexander, David M.; Ohta, Kouji; Suzuki, Ryuji; Tanaka, Ichi; Omata, Koji; Nishimura, Tetsuo; Uchimoto, Yuka K.; Konishi, Masahiro; Koekemoer, Anton M.; Brandt, Niel

    2010-07-20

    We present the results of near-infrared multi-object spectroscopic observations for 37 BzK-color-selected star-forming galaxies conducted with MOIRCS on the Subaru Telescope. The sample is drawn from the K{sub s} -band-selected catalog of the MOIRCS Deep Survey in the GOODS-N region. About half of our samples are selected from the publicly available 24 {mu}m-source catalog of the Multiband Imaging Photometer for Spitzer on board the Spitzer Space Telescope. H{alpha} emission lines are detected from 23 galaxies, of which the median redshift is 2.12. We derived the star formation rates (SFRs) from extinction-corrected H{alpha} luminosities. The extinction correction is estimated from the spectral energy distribution (SED) fitting of multiband photometric data covering UV to near-infrared wavelengths. The Balmer decrement of the stacked emission lines shows that the amount of extinction for the ionized gas is larger than that for the stellar continuum. From a comparison of the extinction-corrected H{alpha} luminosity and other SFR indicators, we found that the relation between the dust properties of stellar continuum and ionized gas is different depending on the intrinsic SFR (differential extinction). We compared SFRs estimated from extinction-corrected H{alpha} luminosities with stellar masses estimated from SED fitting. The comparison shows no correlation between SFR and stellar mass. Some galaxies with stellar mass smaller than {approx}10{sup 10} M{sub sun} show SFRs higher than {approx}100 M{sub sun} yr{sup -1}. The specific SFRs (SSFRs) of these galaxies are remarkably high; galaxies which have SSFR higher than {approx}10{sup -8} yr{sup -1} are found in eight of the present sample. From the best-fit parameters of SED fitting for these high-SSFR galaxies, we find that the average age of the stellar population is younger than 100 Myr, which is consistent with the implied high SSFR. The large SFR implies the possibility that the high-SSFR galaxies significantly

  17. Spectroscopic Confirmation of A Radio-Selected Galaxy Overdensity at z = 1.11

    SciTech Connect

    Stanford, S; Stern, D; Holden, B; Spinrad, H

    2004-02-26

    We report the discovery of a galaxy overdensity at z = 1.11 associated with the z = 1.110 high-redshift radio galaxy MG 0442+0202. The group, CL 0442+0202, was found in a near-infrared survey of z > 1 radio galaxies undertaken to identify spatially-coincident regions with a high density of objects red in I - K' color, typical of z > 1 elliptical galaxies. Spectroscopic observations from the Keck I telescope reveal five galaxies within 35'' of MG 0442+0202 at 1.10 < z < 1.11. These member galaxies have broad-band colors and optical spectra consistent with passively-evolving elliptical galaxies formed at high redshift. Archival ROSAT observations reveal a 3{sigma} detection of soft X-ray emission coincident with CL 0442+0202 at a level five times greater than expected for the radio galaxy. These data are suggestive of a rich galaxy cluster and inspired a 45 ks Chandra X-Ray Observatory observation. As expected, the radio galaxy is unresolved to Chandra, but is responsible for approximately half of the observed X-ray flux. The remaining ROSAT flux is resolved into four point sources within 15'' of the radio galaxy, corresponding to a surface density two orders of magnitude higher than average for X-ray sources at these flux levels (S{sub 0.5-2keV} > 5x10{sup -16} ergs cm{sup -2} s{sup -1}). One of these point sources is identified with a radio-quiet, type II quasar at z = 1.863, akin to sources recently reported in deep Chandra surveys. The limit on an extended hot intracluster medium in the Chandra data is S{sub 1-6keV} < 1.9 x 10{sup -15} ergs cm{sup -2} s{sup -1} (3{sigma}, 30'' radius aperture). Though the X-ray observations do not confirm the existence of a massive, bound cluster at z > 1, the success of the optical/near-infrared targeting of early-type systems near the radio galaxy validates searches using radio galaxies as beacons for high-redshift large-scale structure. We interpret CL 0442+0202 to be a massive cluster in the process of formation.

  18. The effect of suprathermal protons on the physical conditions in Seyfert galaxy nuclei II

    NASA Technical Reports Server (NTRS)

    Stoner, R.; Ptak, R.

    1975-01-01

    The radiative transfer of Ly-alpha, Ly-beta, and H-alpha in a hydrogen gas containing dust was considered with application to the nuclear gas in Seyfert galaxies. By neglecting the direct escape of line radiation and by averaging over the gas, the radiation transfer in space is suppressed and the frequency transfer only is considered. The dust degrades the line radiation via frequency-independent absorption, converting the energy to infrared luminosity. The source functions in the lines were solved, using appropriate approximations, in order to determine under what conditions the narrow component of the Balmer line radiation from the gas can be self-absorbed and degraded without similar degradation of the broad component, which originates from the suprathermals themselves. The results are used to find self-consistent values for the temperature and ionization of the gas for various amounts of dust and various concentrations of suprathermal particles.

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

    SciTech Connect

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

    2013-03-01

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

  20. A Statistical Study of Mg II Absorption Selected Galaxies in the SDSS at 0.4

    NASA Astrophysics Data System (ADS)

    Curtis, Brittney; Lundgren, B.

    2014-01-01

    The spectra of distant quasars frequently exhibit absorption features from singly-ionized magnesium (Mg II), which are understood to trace gas outflow and accretion processes in foreground galaxies. Host galaxies of the Mg II absorbing gas are difficult to detect because they are often faint and have small angular separation from the bright background quasar. We have undertaken a statistical study of low redshift ( 0.4) galaxies identified as potential Mg II absorption hosts which are visible in the Sloan Digital Sky Survey (SDSS). Using data from the SDSS DR7, we compiled a census of ~3200 photometrically-identified galaxies within a projected 150 kpc of an Mg II absorbing system. These potential Mg II absorption hosts were then compared to a control sample of galaxies in the foreground of quasars without absorption systems in the same redshift range. We report a positive detection of excess galaxies around the lines of sight to quasars with Mg II absorption systems, extending to ~90 kpc. We present the luminosity distribution of these excess galaxies and compare to previous, smaller studies from the literature. This work was partially supported by the National Science Foundation's REU program through NSF Award AST-1004881 to the University of Wisconsin-Madison.

  1. H I CONTENT AND OPTICAL PROPERTIES OF FIELD GALAXIES FROM THE ALFALFA SURVEY. I. SELECTION OF A CONTROL SAMPLE

    SciTech Connect

    Toribio, M. Carmen; Solanes, Jose M.; Giovanelli, Riccardo; Haynes, Martha P.; Masters, Karen L. E-mail: jm.solanes@ub.edu E-mail: haynes@astro.cornell.edu

    2011-05-10

    We report results from a study of the H I content and stellar properties of nearby galaxies detected by the Arecibo Legacy Fast ALFA blind 21 cm line survey and the Sloan Digital Sky Survey. We consider two declination strips covering a total area of 9 hr x 16 deg in the general direction of the Virgo Cluster. The present analysis focuses on gas-rich galaxies expected to show little or no evidence of interaction with their surroundings. We seek to assemble a control sample suitable for providing absolute measures of the H I content of gaseous objects, as well as to study the relationship between H I emission and widely used optical measures of morphology. From a database which includes more than 15,000 H I detections, we have assembled three samples that could provide adequate H I standards. The most reliable results are obtained with a sample of 5647 sources found in low-density environments, as defined by a nearest neighbor approach. The other two samples contain several hundred relatively isolated galaxies each, as determined from standard isolation algorithms based either on a combination of spectroscopic and photometric information or solely on photometric data. We find that isolated objects are not particularly gas-rich compared to their low-density-environment counterparts, while they suffer from selection bias and span a smaller dynamic range. All this makes them less suitable for defining a reference for H I content. We have explored the optical morphology of gaseous galaxies in quiet environments, finding that, within the volume surveyed, the vast majority of them display unequivocal late-type galaxy features. In contrast, bona fide gas-rich early-type systems account only for a negligible fraction of the 21 cm detections. We argue that H I emission provides the most reliable way to determine the morphological population to which a galaxy belongs. We have also observed that the color distribution of flux-limited samples of optically selected field H I

  2. ARE THE KINEMATICS OF DLAs IN AGREEMENT WITH THEIR ARISING IN THE GAS DISKS OF GALAXIES?

    SciTech Connect

    Zwaan, Martin; Walter, Fabian; Ryan-Weber, Emma; Kennicutt, Robert C. Jr; Brinks, Elias; De Blok, W. J. G.

    2008-12-15

    We demonstrate in this paper that the velocity widths of the neutral gas in damped Ly{alpha} (DLA) systems are inconsistent with these systems originating in gas disks of galaxies, similar to those seen in the local universe. We examine the gas kinematics of local galaxies using the high-quality H I 21 cm data from the H I Nearby Galaxies Survey and make a comparison with the velocity profiles measured in the low-ionization metal lines observed in DLAs at high redshifts. The median velocity width of z = 0 H I gas above the DLA column density limit of N{sub HI} = 2 x 10{sup 20} cm{sup -2} is approximately 30 km s{sup -1}, whereas the typical value in DLAs is a factor of 2 higher. We argue that the gas kinematics at higher redshifts are increasingly influenced by gas that is not participating in ordered rotation in cold disks, but is more likely associated with tidal gas related to galaxy interactions or processes such as superwinds and outflows. An analysis of the H I in the local interacting starburst galaxy M 82 shows that the velocity widths in this galaxy are indeed similar to what is seen in DLAs.

  3. The distribution of emission-line galaxies in selected areas of the sky

    NASA Technical Reports Server (NTRS)

    Moody, J. Ward

    1988-01-01

    The spatial distribution of emission-line galaxies (ELGs) relative to normal galaxies in several areas of the sky is discussed. Current evidence supports the notion that ELGs trace a low-density population in all the surveyed areas with the possible exception of the CfA 'Slice of the Universe' survey. Based on this and other survey data in the north galactic cap, it is suggested that the ELGs inside the Bootes void may actually define the edge of a totally empty volume within an underdense distribution of normal galaxies.

  4. SDSS-III Baryon Oscillation Spectroscopic Survey data release 12: Galaxy target selection and large-scale structure catalogues

    SciTech Connect

    Reid, Beth; Ho, Shirley; Padmanabhan, Nikhil; Percival, Will J.; Tinker, Jeremy; Tojeiro, Rito; White, Marin; Daniel J. Einstein; Maraston, Claudia; Ross, Ashley J.; Sanchez, Ariel G.; Schlegel, David; Sheldon, Erin; Strauss, Michael A.; Thomas, Daniel; Wake, David; Beutler, Florian; Bizyaev, Dmitry; Bolton, Adam S.; Brownstein, Joel R.; Chuang, Chia -Hsun; Dawson, Kyle; Harding, Paul; Kitaura, Francisco -Shu; Leauthaud, Alexie; Masters, Karen; McBride, Cameron K.; More, Surhud; Olmstead, Matthew D.; Oravetz, Daniel; Nuza, Sebastian E.; Pan, Kaike; Parejko, John; Pforr, Janine; Prada, Francisco; Rodriguez-Torres, Sergio; Salazar-Albornoz, Salvador; Samushia, Lado; Schneider, Donald P.; Scoccola, Claudia G.; Simmons, Audrey; Vargas-Magana, Mariana

    2015-11-17

    The Baryon Oscillation Spectroscopic Survey (BOSS), part of the Sloan Digital Sky Survey (SDSS) III project, has provided the largest survey of galaxy redshifts available to date, in terms of both the number of galaxy redshifts measured by a single survey, and the effective cosmological volume covered. Key to analysing the clustering of these data to provide cosmological measurements is understanding the detailed properties of this sample. Potential issues include variations in the target catalogue caused by changes either in the targeting algorithm or properties of the data used, the pattern of spectroscopic observations, the spatial distribution of targets for which redshifts were not obtained, and variations in the target sky density due to observational systematics. We document here the target selection algorithms used to create the galaxy samples that comprise BOSS. We also present the algorithms used to create large-scale structure catalogues for the final Data Release (DR12) samples and the associated random catalogues that quantify the survey mask. The algorithms are an evolution of those used by the BOSS team to construct catalogues from earlier data, and have been designed to accurately quantify the galaxy sample. Furthermore, the code used, designated mksample, is released with this paper.

  5. SDSS-III Baryon Oscillation Spectroscopic Survey data release 12: Galaxy target selection and large-scale structure catalogues

    DOE PAGESBeta

    Reid, Beth; Ho, Shirley; Padmanabhan, Nikhil; Percival, Will J.; Tinker, Jeremy; Tojeiro, Rito; White, Marin; Daniel J. Einstein; Maraston, Claudia; Ross, Ashley J.; et al

    2015-11-17

    The Baryon Oscillation Spectroscopic Survey (BOSS), part of the Sloan Digital Sky Survey (SDSS) III project, has provided the largest survey of galaxy redshifts available to date, in terms of both the number of galaxy redshifts measured by a single survey, and the effective cosmological volume covered. Key to analysing the clustering of these data to provide cosmological measurements is understanding the detailed properties of this sample. Potential issues include variations in the target catalogue caused by changes either in the targeting algorithm or properties of the data used, the pattern of spectroscopic observations, the spatial distribution of targets formore » which redshifts were not obtained, and variations in the target sky density due to observational systematics. We document here the target selection algorithms used to create the galaxy samples that comprise BOSS. We also present the algorithms used to create large-scale structure catalogues for the final Data Release (DR12) samples and the associated random catalogues that quantify the survey mask. The algorithms are an evolution of those used by the BOSS team to construct catalogues from earlier data, and have been designed to accurately quantify the galaxy sample. Furthermore, the code used, designated mksample, is released with this paper.« less

  6. SDSS-III Baryon Oscillation Spectroscopic Survey Data Release 12: galaxy target selection and large-scale structure catalogues

    NASA Astrophysics Data System (ADS)

    Reid, Beth; Ho, Shirley; Padmanabhan, Nikhil; Percival, Will J.; Tinker, Jeremy; Tojeiro, Rita; White, Martin; Eisenstein, Daniel J.; Maraston, Claudia; Ross, Ashley J.; Sánchez, Ariel G.; Schlegel, David; Sheldon, Erin; Strauss, Michael A.; Thomas, Daniel; Wake, David; Beutler, Florian; Bizyaev, Dmitry; Bolton, Adam S.; Brownstein, Joel R.; Chuang, Chia-Hsun; Dawson, Kyle; Harding, Paul; Kitaura, Francisco-Shu; Leauthaud, Alexie; Masters, Karen; McBride, Cameron K.; More, Surhud; Olmstead, Matthew D.; Oravetz, Daniel; Nuza, Sebastián E.; Pan, Kaike; Parejko, John; Pforr, Janine; Prada, Francisco; Rodríguez-Torres, Sergio; Salazar-Albornoz, Salvador; Samushia, Lado; Schneider, Donald P.; Scóccola, Claudia G.; Simmons, Audrey; Vargas-Magana, Mariana

    2016-01-01

    The Baryon Oscillation Spectroscopic Survey (BOSS), part of the Sloan Digital Sky Survey (SDSS) III project, has provided the largest survey of galaxy redshifts available to date, in terms of both the number of galaxy redshifts measured by a single survey, and the effective cosmological volume covered. Key to analysing the clustering of these data to provide cosmological measurements is understanding the detailed properties of this sample. Potential issues include variations in the target catalogue caused by changes either in the targeting algorithm or properties of the data used, the pattern of spectroscopic observations, the spatial distribution of targets for which redshifts were not obtained, and variations in the target sky density due to observational systematics. We document here the target selection algorithms used to create the galaxy samples that comprise BOSS. We also present the algorithms used to create large-scale structure catalogues for the final Data Release (DR12) samples and the associated random catalogues that quantify the survey mask. The algorithms are an evolution of those used by the BOSS team to construct catalogues from earlier data, and have been designed to accurately quantify the galaxy sample. The code used, designated MKSAMPLE, is released with this paper.

  7. The Atacama Cosmology Telescope: dynamical masses for 44 SZ-selected galaxy clusters over 755 square degrees

    NASA Astrophysics Data System (ADS)

    Sifón, Cristóbal; Battaglia, Nick; Hasselfield, Matthew; Menanteau, Felipe; Barrientos, L. Felipe; Bond, J. Richard; Crichton, Devin; Devlin, Mark J.; Dünner, Rolando; Hilton, Matt; Hincks, Adam D.; Hlozek, Renée; Huffenberger, Kevin M.; Hughes, John P.; Infante, Leopoldo; Kosowsky, Arthur; Marsden, Danica; Marriage, Tobias A.; Moodley, Kavilan; Niemack, Michael D.; Page, Lyman A.; Spergel, David N.; Staggs, Suzanne T.; Trac, Hy; Wollack, Edward J.

    2016-09-01

    We present galaxy velocity dispersions and dynamical mass estimates for 44 galaxy clusters selected via the Sunyaev-Zel'dovich (SZ) effect by the Atacama Cosmology Telescope. Dynamical masses for 18 clusters are reported here for the first time. Using N-body simulations, we model the different observing strategies used to measure the velocity dispersions and account for systematic effects resulting from these strategies. We find that the galaxy velocity distributions may be treated as isotropic, and that an aperture correction of up to 7 per cent in the velocity dispersion is required if the spectroscopic galaxy sample is sufficiently concentrated towards the cluster centre. Accounting for the radial profile of the velocity dispersion in simulations enables consistent dynamical mass estimates regardless of the observing strategy. Cluster masses M200 are in the range (1-15) × 1014 M⊙. Comparing with masses estimated from the SZ distortion assuming a gas pressure profile derived from X-ray observations gives a mean SZ-to-dynamical mass ratio of 1.10 ± 0.13, but there is an additional 0.14 systematic uncertainty due to the unknown velocity bias; the statistical uncertainty is dominated by the scatter in the mass-velocity dispersion scaling relation. This ratio is consistent with previous determinations at these mass scales.

  8. The Atacama Cosmology Telescope: Dynamical Masses for 44 SZ-Selected Galaxy Clusters over 755 Square Degrees

    NASA Technical Reports Server (NTRS)

    Sifon, Cristobal; Battaglia, Nick; Hasselfield, Matthew; Menanteau, Felipe; Barrientos, L. Felipe; Bond, J. Richard; Crichton, Devin; Devlin, Mark J.; Dunner, Rolando; Hilton, Matt; Wollack, Edward J.

    2016-01-01

    We present galaxy velocity dispersions and dynamical mass estimates for 44 galaxy clusters selected via the Sunyaev-Zeldovich (SZ) effect by the Atacama Cosmology Telescope. Dynamical masses for 18 clusters are reported here for the first time. Using N-body simulations, we model the different observing strategies used to measure the velocity dispersions and account for systematic effects resulting from these strategies. We find that the galaxy velocity distributions may be treated as isotropic, and that an aperture correction of up to 7 per cent in the velocity dispersion is required if the spectroscopic galaxy sample is sufficiently concentrated towards the cluster centre. Accounting for the radial profile of the velocity dispersion in simulations enables consistent dynamical mass estimates regardless of the observing strategy. Cluster masses M200 are in the range (1 - 15) times 10 (sup 14) Solar Masses. Comparing with masses estimated from the SZ distortion assuming a gas pressure profile derived from X-ray observations gives a mean SZ-to-dynamical mass ratio of 1:10 plus or minus 0:13, but there is an additional 0.14 systematic uncertainty due to the unknown velocity bias; the statistical uncertainty is dominated by the scatter in the mass-velocity dispersion scaling relation. This ratio is consistent with previous determinations at these mass scales.

  9. Dust-obscured star formation and the contribution of galaxies escaping UV/optical color selections at z ~ 2

    NASA Astrophysics Data System (ADS)

    Riguccini, L.; Le Floc'h, E.; Ilbert, O.; Aussel, H.; Salvato, M.; Capak, P.; McCracken, H.; Kartaltepe, J.; Sanders, D.; Scoville, N.

    2011-10-01

    Context. A substantial amount of the stellar mass growth across cosmic time occurred within dust-enshrouded environments. So far, identification of complete samples of distant star-forming galaxies from the short wavelength range has been strongly biased by the effect of dust extinction. Nevertheless, the exact amount of star-forming activity that took place in high-redshift dusty galaxies but that has currently been missed by optical surveys has barely been explored. Aims: Our goal is to determine the number of luminous star-forming galaxies at 1.5 ≲ z ≲ 3 that are potentially missed by the traditional color selection techniques because of dust extinction. We also aim at quantifying the contribution of these sources to the IR luminosity and cosmic star formation density at high redshift. Methods: We based our work on a sample of 24 μm sources brighter than 80 μJy and taken from the Spitzer survey of the COSMOS field. Almost all of these sources have accurate photometric redshifts. We applied to this mid-IR selected sample the BzK and BM/BX criteria, as well as the selections of the IRAC peakers and the Optically-Faint IR-bright (OFIR) galaxies. We analyzed the fraction of sources identified with these techniques. We also computed 8 μm rest-frame luminosity from the 24 μm fluxes of our sources, and considering the relationships between L8 μm and LPaα and between L8 μm and LIR, we derived ρIR and then ρSFR for our MIPS sources. Results: The BzK criterion offers an almost complete (~90%) identification of the 24 μm sources at 1.4 < z < 2.5. In contrast, the BM/BX criterion misses 50% of the MIPS sources. We attribute this bias to the effect of extinction, which reddens the typical colors of galaxies. The contribution of these two selections to the IR luminosity density produced by all the sources brighter than 80 μJy are on the same order. Moreover the criterion based on the presence of a stellar bump in their spectra (IRAC peakers) misses up to 40% of

  10. High levels of absorption in orientation-unbiased, radio-selected 3CR Active Galaxies

    NASA Astrophysics Data System (ADS)

    Wilkes, Belinda J.; Haas, Martin; Barthel, Peter; Leipski, Christian; Kuraszkiewicz, Joanna; Worrall, Diana; Birkinshaw, Mark; Willner, Steven P.

    2014-08-01

    A critical problem in understanding active galaxies (AGN) is the separation of intrinsic physical differences from observed differences that are due to orientation. Obscuration of the active nucleus is anisotropic and strongly frequency dependent leading to complex selection effects for observations in most wavebands. These can only be quantified using a sample that is sufficiently unbiased to test orientation effects. Low-frequency radio emission is one way to select a close-to orientation-unbiased sample, albeit limited to the minority of AGN with strong radio emission.Recent Chandra, Spitzer and Herschel observations combined with multi-wavelength data for a complete sample of high-redshift (1 24.2) = 2.5:1.4:1 in these high-luminosity (log L(0.3-8keV) ~ 44-46) sources. These ratios are consistent with current expectations based on modelingthe Cosmic X-ray Background. A strong correlation with radio orientation constrains the geometry of the obscuring disk/torus to have a ~60 degree opening angle and ~12 degree Compton-thick cross-section. The deduced ~50% obscured fraction of the population contrasts with typical estimates of ~20% obscured in optically- and X-ray-selected high-luminosity samples. Once the primary nuclear emission is obscured, AGN X-ray spectra are frequently dominated by unobscured non-nuclear or scattered nuclear emission which cannot be distinguished from direct nuclear emission with a lower obscuration level unless high quality data is available. As a result, both the level of obscuration and the estimated instrinsic luminosities of highly-obscured AGN are likely to be significantly (*10-1000) underestimated for 25-50% of the population. This may explain the lower obscured fractions reported for optical and X-ray samples which have no independent measure of the AGN

  11. Linear polarization observations in selected celestial zones - the central region of our Galaxy

    SciTech Connect

    Bignell, R.C.; Simard-Normandin, M.; Vallee, J.P.

    1988-07-01

    The Algonquin Radio Observatory and the very large array have been used to obtain the linear polarization integrated over the angular size of a radio galaxy or quasar. All sources are located in a celestial angular zone encompassing the central region of the Galaxy. In addition to the total intensity (Stokes I) flux density, the percentage and position angle of the linear polarization (Stokes Q and U) are obtained for 14 sources at several centimetric wavelengths. 15 references.

  12. Comparing Cool Cores in the Planck SZ Selected Samples of Clusters of Galaxies with Cool Cores in X-ray Selected Cluster Samples

    NASA Astrophysics Data System (ADS)

    Jones, Christine; Santos, Felipe A.; Forman, William R.; Kraft, Ralph P.; Lovisari, Lorenzo; Arnaud, Monique; Mazzotta, Pasquale; Van Weeren, Reinout J.; Churazov, Eugene; Ferrari, Chiara; Borgani, Stefano; Chandra-Planck Collaboration

    2016-06-01

    The Planck mission provided a representative sample of clusters of galaxies over the entire sky. With completed Chandra observations of 165 Planck ESZ and cosmology sample clusters at z<0.35, we can now characterize each cluster in terms of its X-ray luminosity, gas temperature, gas mass, total mass, gas entropy, gas central cooling time, presence of active AGN, gas cavities, radio emission, and cluster morphology. In this presentation we compare the percentages of cool core and non-cool core clusters in the Planck-selected clusters with the percentages in X-ray selected cluster samples. We find a significantly smaller percentage of cool core clusters in the Planck sample than in X-ray selected cluster samples. We will discuss the primary reasons for this smaller percentage of cool-core clusters in the Planck-selected cluster sample than in X-ray-selected samples.

  13. Spitzer 24 Micron Observations of Optical/Near-Infrared-Selected Extremely Red Galaxies: Evidence for Assembly of Massive Galaxies at Z approximately equal to 1-2?

    NASA Technical Reports Server (NTRS)

    Yan, Lin; Choi, Philip I.; Fadda, D.; Marleau, F. R.; Soifer, B. T.; Im, M.; Armus, L.; Frayer, D. T.; Storrie-Lombardi, L. J.; Thompson, D. J.; Teplitz, H. I.; Helou, G.; Appleton, P. N.; Chapman, S.; Fan, F.; Heinrichsen, I.; Lacy, M.; Shupe, D. L.; Squires, G. K.; Surace, J.; Wilson, G.

    2004-01-01

    We carried out direct measurement of the fraction of dusty sources in a sample of extremely red galaxies with (R - Ks) >= 5.3 mag and Ks < 20:2 mag, using 24 micron data from the Spitzer Space Telescope. Combining deep 24 micron Ks- and R-band data over an area of 64 arcmin(sup 2) in ELAIS N1 of the Spitzer First Look Survey (FLS), we find that 50% +/- 6% of our extremely red object (ERO) sample have measurable 24 micron flux above the 3 (sigma) flux limit of 40 (micro)Jy. This flux limit corresponds to a star formation rate (SFR) of 12 solar masses per year 1, much more sensitive than any previous long-wavelength measurement. The 24 micron-detected EROs have 24 micron/2.2 micron and 24 micron/0.7 micron flux ratios consistent with infrared luminous, dusty sources at z >= 1, and are an order of magnitude too red to be explained by an infrared quiescent spiral or a pure old stellar population at any redshift. Some of these 24 micron-detected EROs could be active galactic nuclei; however, the fraction among the whole ERO sample is probably small, 10%-20%, as suggested by deep X-ray observations as well as optical spectroscopy. Keck optical spectroscopy of a sample of similarly selected EROs in the FLS field suggests that most of the EROs in ELAIS N1 are probably at z 1. The mean 24 micron flux (167 (micro)Jy) of the 24 micron-detected ERO sample roughly corresponds to the rest-frame 12 micron luminosity, (nu)L(nu)(12 micron, of 3x10(exp 10)(deg) solar luminosities at z 1. Using the c IRAS (nu)L(nu)(12 (micron) and infrared luminosity LIR(8-1000 (micron), we infer that the (LIR) of the 24 micron- detected EROs is 3 x 10(exp 11) and 1 x 10(exp 12) solar luminosities at z = 1.0 and similar to that of local luminous infrared galaxies (LIRGs) and ultraluminous infrared galaxies (ULIRGs). The corresponding SFR would be roughly 50-170 solar masses per year. If the timescale of this starbursting phase is on the order of 108 yr as inferred for the local LIRGs and ULIRGs, the

  14. MULTIPLE SHOCK STRUCTURES IN A RADIO-SELECTED CLUSTER OF GALAXIES

    SciTech Connect

    Brown, S.; Duesterhoeft, J.; Rudnick, L.

    2011-01-20

    We present a new radio-selected cluster of galaxies, 0217+70, using observations from the Very Large Array and archival optical and X-ray data. The new cluster is one of only seven known that has candidate double peripheral radio relics, and the second of those with a giant radio halo (GRH), as well. It also contains unusual diffuse radio filaments interior to the peripheral relics and a clumpy, elongated X-ray structure. All of these indicate a very actively evolving system, with ongoing accretion and merger activity, illuminating a network of shocks, such as those first seen in numerical simulations. The peripheral relics are most easily understood as outgoing spherical merger shocks with large variations in brightness along them, likely reflecting the inhomogeneities in the shocks' magnetic fields. The interior filaments could be projections of substructures from the sheet-like peripheral shocks or they might be separate structures due to multiple accretion events. ROSAT images show large-scale diffuse X-ray emission coincident with the GRH and additional patchy diffuse emission that suggests a recent merger event. This uniquely rich set of radio shocks and halo offer the possibility, with deeper X-ray and optical data and higher resolution radio observations, of testing the models of how shocks and turbulence couple to the relativistic plasma. The cluster 0217+70 is also overluminous in the radio compared with the empirical radio-X-ray correlation for clusters-the third example of such a system. This new population of diffuse radio emission opens up the possibility of probing low-mass cluster mergers with upcoming deep radio continuum surveys.

  15. CO emissions from optically selected galaxies at z ˜ 0.1-0.2: Tight anti-correlation between molecular gas fraction and 4000 Å break strength

    NASA Astrophysics Data System (ADS)

    Morokuma-Matsui, Kana; Baba, Junichi; Sorai, Kazuo; Kuno, Nario

    2015-06-01

    We performed 12CO(J = 1-0) (hereafter, CO) observations toward 12 normal star-forming galaxies with stellar masses of M⋆ = 1010.6-1011.3 M⊙ at z = 0.1-0.2 with the 45 m telescope at the Nobeyama Radio Observatory. The samples were selected with Dn(4000), that is, the strength of the 4000 Å break, instead of the commonly used far-infrared (FIR) flux. We successfully detected the CO emissions from eight galaxies with signal-to-noise ratio larger than three, demonstrating the effectiveness of the Dn(4000)-based sample selection. For the first time, we find a tight anti-correlation between Dn(4000) and molecular gas fraction (fmol) using literature data of nearby galaxies in which the galaxies with more fuel for star formation have younger stellar populations. We find that our CO-detected galaxies at z ˜ 0.1-0.2 also follow the same relation as nearby galaxies. This implies that the galaxies evolve along this Dn(4000)-fmol relation, and that Dn(4000) seems to be able to be used as a proxy for fmol, which requires many time-consuming observations. Based on the comparison with the model calculation with a population synthesis code, we find that star formation from metal enriched gas and its quenching in the early time are necessary to reproduce galaxies with large Dn(4000) and non-zero gas fraction.

  16. A Hubble Space Telescope Survey of Extended [O III] λ5007 Emission in a Far-Infrared Selected Sample of Seyfert Galaxies: Observations

    NASA Astrophysics Data System (ADS)

    Schmitt, H. R.; Donley, J. L.; Antonucci, R. R. J.; Hutchings, J. B.; Kinney, A. L.

    2003-10-01

    We present a Hubble Space Telescope (HST) survey of extended [O III] emission for a sample of 60 Seyfert galaxies (22 Seyfert 1 galaxies and 38 Seyfert 2 galaxies), selected based on their far-infrared properties. The observations for 42 of these galaxies were done in a snapshot survey with WFPC2. The remaining 18 were obtained from the HST archive, most of which were observed with the same configuration. These observations cover 68% of the objects in the sample defined by Kinney et al. and create a valuable data set for the study of the narrow-line region (NLR) properties of Seyfert galaxies. In this paper, we present the details of the observations, reductions, and measurements. We also discuss the extended structure of individual sources, and the relation of this emission to the radio and host galaxy morphology. We also address how representative the subsample of [O III]-imaged galaxies is of the entire sample, and possible selection effects that may affect this comparison of the properties of Seyfert 1 and Seyfert 2 galaxies. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  17. NEAR-INFRARED SURVEY OF THE GOODS-NORTH FIELD: SEARCH FOR LUMINOUS GALAXY CANDIDATES AT z {approx}> 6.5 {sup ,}

    SciTech Connect

    Hathi, Nimish P.; Mobasher, Bahram; Capak, Peter; Wang, Wei-Hao; Ferguson, Henry C.

    2012-09-20

    We present near-infrared (NIR; J and K{sub s}) survey of the Great Observatories Origins Deep Survey-North (GOODS-N) field. The publicly available imaging data were obtained using the MOIRCS instrument on the 8.2 m Subaru and the WIRCam instrument on the 3.6 m Canada-France-Hawaii Telescope (CFHT). These observations fulfill a serious wavelength gap in the GOODS-N data, i.e., lack of deep NIR observations. We combine the Subaru/MOIRCS and CFHT/WIRCam archival data to generate deep J- and K{sub s}-band images, covering the full GOODS-N field ({approx}169 arcmin{sup 2}) to an AB magnitude limit of {approx}25 mag (3{sigma}). We applied z{sub 850}-band dropout color selection criteria, using the NIR data generated here. We have identified two possible Lyman break galaxy (LBG) candidates at z {approx}> 6.5 with J {approx}< 24.5. The first candidate is a likely LBG at z {approx_equal} 6.5 based on a weak spectral feature tentatively identified as Ly{alpha} line in the deep Keck/DEIMOS spectrum, while the second candidate is a possible LBG at z {approx_equal} 7 based on its photometric redshift. These z{sub 850}-dropout objects, if confirmed, are among the brightest such candidates found so far. At z {approx}> 6.5, their star formation rate is estimated as 100-200 M{sub Sun} yr{sup -1}. If they continue to form stars at this rate, they assemble a stellar mass of {approx}5 Multiplication-Sign 10{sup 10} M{sub Sun} after about 400 million years, becoming the progenitors of massive galaxies observed at z {approx_equal} 5. We study the implication of the z{sub 850}-band dropout candidates discovered here, in constraining the bright end of the luminosity function and understanding the nature of high-redshift galaxies.

  18. Spectral properties of X-ray selected narrow emission line galaxies

    NASA Astrophysics Data System (ADS)

    Romero-Colmenero, E.

    1998-03-01

    This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha~1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for N_H. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law slope of the average NELG is alpha = 0.45 +/- 0.09, whilst that of the AGN is alpha = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (<= 2e-15 ergs cm-2 s-1), thus suggesting that NELGs are important contributors to the residual soft (<2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (alpha~0.4, 1-10 keV) is harder than that of AGN (alpha~1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha~0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to

  19. Spectral properties of x-ray selected narrow emission line galaxies

    NASA Astrophysics Data System (ADS)

    Romero Colmenero, Encarnacion

    This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha ~ 1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for NH. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law spectral slope of the average NELG is S = 0.45 +/- 0.09, whilst that of the AGN is S = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (< 2 x 10-15erg cm-2 s -1), thus suggesting that NELGs are important contributors to the residual soft (< 2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (S ~ 0.4, 1-10 keV) is harder than that of AGN (S ~ 1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha ~ 0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to

  20. A LABOCA Survey of the Extended Chandra Deep Field South—Submillimeter Properties of Near-infrared Selected Galaxies

    NASA Astrophysics Data System (ADS)

    Greve, T. R.; Weiβ, A.; Walter, F.; Smail, I.; Zheng, X. Z.; Knudsen, K. K.; Coppin, K. E. K.; Kovács, A.; Bell, E. F.; de Breuck, C.; Dannerbauer, H.; Dickinson, M.; Gawiser, E.; Lutz, D.; Rix, H.-W.; Schinnerer, E.; Alexander, D.; Bertoldi, F.; Brandt, N.; Chapman, S. C.; Ivison, R. J.; Koekemoer, A. M.; Kreysa, E.; Kurczynski, P.; Menten, K.; Siringo, G.; Swinbank, M.; van der Werf, P.

    2010-08-01

    Using the 330 hr ESO-MPG 870 μm survey of the Extended Chandra Deep Field South (ECDF-S) obtained with the Large Apex BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment (APEX), we have carried out a stacking analysis at submillimeter (submm) wavelengths of a sample of 8266 near-infra-red (near-IR) selected (K vega <= 20) galaxies, including 893 BzK galaxies, 1253 extremely red objects (EROs), and 737 distant red galaxies (DRGs), selected from the Multi-wavelength Survey by Yale-Chile (MUSYC). We measure average 870 μm fluxes of 0.22 ± 0.01 mJy (22.0σ), 0.48 ± 0.04 mJy (12.0σ), 0.39 ± 0.03 mJy (13.0σ), and 0.43 ± 0.04 mJy (10.8σ) for the K vega <= 20, BzK, ERO, and DRG samples, respectively. For the BzK, ERO, and DRG sub-samples, which overlap to some degree and are likely to be at z ~= 1-2, this implies an average far-IR luminosity of ~(1-5) × 1011 Lsun and star formation rate (SFR) of ~20-90 Msun . Splitting the BzK galaxies into star-forming (sBzK) and passive (pBzK) galaxies, the former is significantly detected (0.50 ± 0.04 mJy, 12.5σ) while the latter is only marginally detected (0.34 ± 0.10 mJy, 3.4σ), thus confirming that the sBzK and pBzK criteria to some extent select obscured, star-forming, and truly passive galaxies, respectively. The K vega <= 20 galaxies are found to contribute 7.27 ± 0.34 Jy deg-2 (16.5% ± 5.7%) to the 870 μm extragalactic background light (EBL). sBzK and pBzK galaxies contribute 1.49 ± 0.22 Jy deg-2 (3.4% ± 1.3%) and 0.20 ± 0.14 Jy deg-2 (0.5% ± 0.3%) to the EBL. We present the first delineation of the average submm signal from the K vega <= 20 selected galaxies and their contribution to the submm EBL as a function of (photometric) redshift, and find a decline in the average submm signal (and therefore IR luminosity and SFR) by a factor ~2-3 from z ~ 2 to z ~ 0. This is in line with a cosmic star formation history in which the star formation activity in galaxies increases significantly at z >~ 1. A

  1. Starburst galaxies

    NASA Technical Reports Server (NTRS)

    Weedman, Daniel W.

    1987-01-01

    The infrared properties of star-forming galaxies, primarily as determined by the Infrared Astronomy Satellite (IRAS), are compared to X-ray, optical, and radio properties. Luminosity functions are reviewed and combined with those derived from optically discovered samples using 487 Markarian galaxies with redshifts and published IRAS 60 micron fluxes, and 1074 such galaxies in the Center for Astrophysics redshift survey. It is found that the majority of infrared galaxies which could be detected are low luminosity sources already known from the optical samples, but non-infrared surveys have found only a very small fraction of the highest luminosity sources. Distributions of infrared to optical fluxes and available spectra indicate that the majority of IRAS-selected galaxies are starburst galaxies. Having a census of starburst galaxies and associated dust allow severl important global calculations. The source counts are predicted as a function of flux limits for both infrared and radio fluxes. These galaxies are found to be important radio sources at faint flux limits. Taking the integrated flux to z = 3 indicates that such galaxies are a significant component of the diffuse X-ray background, and could be the the dominant component depending on the nature of the X-ray spectra and source evolution.

  2. VizieR Online Data Catalog: PS1 MDS X-ray selected galaxy clusters (Ebeling+, 2013)

    NASA Astrophysics Data System (ADS)

    Ebeling, H.; Edge, A. C.; Burgett, W. S.; Chambers, K. C.; Hodapp, K. W.; Huber, M. E.; Kaiser, N.; Price, P. A.; Tonry, J. L.

    2014-11-01

    Our strategy for the identification of galaxy clusters at z>0.5 from these data sets is brute force: we select all X-ray sources listed in the RASS BSC and FSC that fall within our study area, and then examine PS1 images in the gP1, rP1, iP1 and zP1 bands in a 5x5arcmin2 region around the X-ray source position. Candidate clusters at intermediate to high redshift (z>~0.3) are readily identifiable as pronounced overdensities of faint, red galaxies. In order to prevent seemingly blank fields from erroneously being classified as potentially very distant clusters, we also query NASA Extragalactic Database (NED) for known celestial objects within 2-arcmin radius of the respective X-ray source, a process that eliminates large numbers of active galactic nuclei (AGN) and quasi-stellar objects (QSOs). (1 data file).

  3. HerMES: The Contribution to the Cosmic Infrared Background from Galaxies Selected by Mass and Redshift

    NASA Astrophysics Data System (ADS)

    Viero, M. P.; Moncelsi, L.; Quadri, R. F.; Arumugam, V.; Assef, R. J.; Béthermin, M.; Bock, J.; Bridge, C.; Casey, C. M.; Conley, A.; Cooray, A.; Farrah, D.; Glenn, J.; Heinis, S.; Ibar, E.; Ikarashi, S.; Ivison, R. J.; Kohno, K.; Marsden, G.; Oliver, S. J.; Roseboom, I. G.; Schulz, B.; Scott, D.; Serra, P.; Vaccari, M.; Vieira, J. D.; Wang, L.; Wardlow, J.; Wilson, G. W.; Yun, M. S.; Zemcov, M.

    2013-12-01

    We quantify the fraction of the cosmic infrared background (CIB) that originates from galaxies identified in the UV/optical/near-infrared by stacking 81,250 (~35.7 arcmin-2) K-selected sources (K AB < 24.0) split according to their rest-frame U - V versus V - J colors into 72,216 star-forming and 9034 quiescent galaxies, on maps from Spitzer/MIPS (24 μm), Herschel/PACS (100, 160 μm), Herschel/SPIRE (250, 350, 500 μm), and AzTEC (1100 μm). The fraction of the CIB resolved by our catalog is (69% ± 15%) at 24 μm, (78% ± 17%) at 70 μm, (58% ± 13%) at 100 μm, (78% ± 18%) at 160 μm, (80% ± 17%) at 250 μm, (69% ± 14%) at 350 μm, (65% ± 12%) at 500 μm, and (45% ± 8%) at 1100 μm. Of that total, about 95% originates from star-forming galaxies, while the remaining 5% is from apparently quiescent galaxies. The CIB at λ <~ 200 μm appears to be sourced predominantly from galaxies at z <~ 1, while at λ >~ 200 μm the bulk originates from 1 <~ z <~ 2. Galaxies with stellar masses log(M/M ⊙) = 9.5-11 are responsible for the majority of the CIB, with those in the log(M/M ⊙) = 9.5-10 bin contributing mostly at λ < 250 μm, and those in the log(M/M ⊙) = 10-11 bin dominating at λ > 350 μm. The contribution from galaxies in the log(M/M ⊙) = 9.0-9.5 (lowest) and log(M/M ⊙) = 11.0-12.0 (highest) stellar-mass bins contribute the least—both of order 5%—although the highest stellar-mass bin is a significant contributor to the luminosity density at z >~ 2. The luminosities of the galaxies responsible for the CIB shifts from combinations of "normal" and luminous infrared galaxies (LIRGs) at λ <~ 160 μm, to LIRGs at 160 <~ λ <~ 500 μm, to finally LIRGs and ultra-luminous infrared galaxies at λ >~ 500 μm. Stacking analyses were performed using SIMSTACK, a novel algorithm designed to account for possible biases in the stacked flux density due to clustering. It is made available to the public at www

  4. HerMES: The contribution to the cosmic infrared background from galaxies selected by mass and redshift

    SciTech Connect

    Viero, M. P.; Moncelsi, L.; Bock, J.; Bridge, C.; Cooray, A.; Quadri, R. F.; Arumugam, V.; Ivison, R. J.; Assef, R. J.; Béthermin, M.; Conley, A.; Glenn, J.; Farrah, D.; Heinis, S.; Ibar, E.; Ikarashi, S.; Kohno, K.; Marsden, G.; Oliver, S. J.; and others

    2013-12-10

    We quantify the fraction of the cosmic infrared background (CIB) that originates from galaxies identified in the UV/optical/near-infrared by stacking 81,250 (∼35.7 arcmin{sup –2}) K-selected sources (K {sub AB} < 24.0) split according to their rest-frame U – V versus V – J colors into 72,216 star-forming and 9034 quiescent galaxies, on maps from Spitzer/MIPS (24 μm), Herschel/PACS (100, 160 μm), Herschel/SPIRE (250, 350, 500 μm), and AzTEC (1100 μm). The fraction of the CIB resolved by our catalog is (69% ± 15%) at 24 μm, (78% ± 17%) at 70 μm, (58% ± 13%) at 100 μm, (78% ± 18%) at 160 μm, (80% ± 17%) at 250 μm, (69% ± 14%) at 350 μm, (65% ± 12%) at 500 μm, and (45% ± 8%) at 1100 μm. Of that total, about 95% originates from star-forming galaxies, while the remaining 5% is from apparently quiescent galaxies. The CIB at λ ≲ 200 μm appears to be sourced predominantly from galaxies at z ≲ 1, while at λ ≳ 200 μm the bulk originates from 1 ≲ z ≲ 2. Galaxies with stellar masses log(M/M {sub ☉}) = 9.5-11 are responsible for the majority of the CIB, with those in the log(M/M {sub ☉}) = 9.5-10 bin contributing mostly at λ < 250 μm, and those in the log(M/M {sub ☉}) = 10-11 bin dominating at λ > 350 μm. The contribution from galaxies in the log(M/M {sub ☉}) = 9.0-9.5 (lowest) and log(M/M {sub ☉}) = 11.0-12.0 (highest) stellar-mass bins contribute the least—both of order 5%—although the highest stellar-mass bin is a significant contributor to the luminosity density at z ≳ 2. The luminosities of the galaxies responsible for the CIB shifts from combinations of 'normal' and luminous infrared galaxies (LIRGs) at λ ≲ 160 μm, to LIRGs at 160 ≲ λ ≲ 500 μm, to finally LIRGs and ultra-luminous infrared galaxies at λ ≳ 500 μm. Stacking analyses were performed using SIMSTACK, a novel algorithm designed to account for possible biases in the stacked flux density due to clustering. It is made available to the public

  5. A STARBURSTING PROTO-CLUSTER IN MAKING ASSOCIATED WITH A RADIO GALAXY AT z = 2.53 DISCOVERED BY H{alpha} IMAGING

    SciTech Connect

    Hayashi, Masao; Kodama, Tadayuki; Tadaki, Ken-ichi; Koyama, Yusei; Tanaka, Ichi

    2012-09-20

    We report a discovery of a proto-cluster in vigorous assembly and hosting strong star-forming activities, associated with a radio galaxy USS 1558-003 at z = 2.53, as traced by wide-field narrow-band H{alpha} imaging with MOIRCS on the Subaru Telescope. We find 68 H{alpha} emitters with dust-uncorrected star formation rates (SFRs) down to 8.6 M{sub Sun} yr{sup -1}. Their spatial distribution indicates that there are three prominent clumps of H{alpha} emitters: one surrounding the radio galaxy, the second located at {approx}1.5 Mpc away to the southwest, and the third located between the two. These contiguous three systems are very likely to merge together in the near future and may grow to a single more massive cluster at a later time. While most H{alpha} emitters reside in the 'blue cloud' on the color-magnitude diagram, some emitters have very red colors with J - K{sub s} > 1.38(AB). Interestingly, such red H{alpha} emitters are located toward the faint end of the red sequence, and they tend to be located in high density clumps. We do not see any statistically significant difference in the distributions of individual SFRs or stellar masses of the H{alpha} emitters between the dense clumps and the other regions, suggesting that this is one of the notable sites where the progenitors of massive galaxies in the present-day clusters were in their vigorous formation phase. Finally, we find that H{alpha} emission of the radio galaxy is fairly extended spatially over {approx}4.''5. However, it is not as widespread as its Ly{alpha} halo, meaning that the Ly{alpha} emission is indeed severely extended by resonant scattering.

  6. HUBBLE SPACE TELESCOPE FAR-ULTRAVIOLET OBSERVATIONS OF BRIGHTEST CLUSTER GALAXIES: THE ROLE OF STAR FORMATION IN COOLING FLOWS AND BCG EVOLUTION

    SciTech Connect

    O'Dea, Kieran P.; Quillen, Alice C.; O'Dea, Christopher P.; Tremblay, Grant R.; Snios, Bradford T.; Baum, Stefi A.; Christiansen, Kevin; Noel-Storr, Jacob; Edge, Alastair C.; Donahue, Megan; Voit, G. Mark

    2010-08-20

    Quillen et al. and O'Dea et al. carried out a Spitzer study of a sample of 62 brightest cluster galaxies (BCGs) from the ROSAT brightest cluster sample, which were chosen based on their elevated H{alpha} flux. We present Hubble Space Telescope Advanced Camera for Surveys far-ultraviolet (FUV) images of the Ly{alpha} and continuum emission of the luminous emission-line nebulae in seven BCGs found to have an infrared (IR) excess. We confirm that the BCGs are actively forming stars which suggests that the IR excess seen in these BCGs is indeed associated with star formation. Our observations are consistent with a scenario in which gas that cools from the intracluster medium fuels the star formation. The FUV continuum emission extends over a region {approx}7-28 kpc (largest linear size) and even larger in Ly{alpha}. The young stellar population required by the FUV observations would produce a significant fraction of the ionizing photons required to power the emission-line nebulae. Star formation rates estimated from the FUV continuum range from {approx}3 to {approx}14 times lower than those estimated from the IR, however, both the Balmer decrements in the central few arcseconds and detection of CO in most of these galaxies imply that there are regions of high extinction that could have absorbed much of the FUV continuum. Analysis of archival Very Large Array observations reveals compact radio sources in all seven BCGs and kpc scale jets in A-1835 and RXJ 2129+00. The four galaxies with archival deep Chandra observations exhibit asymmetric X-ray emission, the peaks of which are offset from the center of the BCG by {approx}10 kpc on average. A low feedback state for the active galactic nucleus could allow increased condensation of the hot gas into the center of the galaxy and the feeding of star formation.

  7. X-ray selected galaxy clusters in the Pan-STARRS Medium Deep Survey

    NASA Astrophysics Data System (ADS)

    Ebeling, H.; Edge, A. C.; Burgett, W. S.; Chambers, K. C.; Hodapp, K. W.; Huber, M. E.; Kaiser, N.; Price, P. A.; Tonry, J. L.

    2013-06-01

    We present the results of a pilot study for the extended Massive Cluster Survey (eMACS), a comprehensive search for distant, X-ray luminous galaxy clusters at z > 0.5. Our pilot study applies the eMACS concept to the 71 deg2 area extended by the 10 fields of the Pan-STARRS1 (PS1) Medium Deep Survey (MDS). Candidate clusters are identified by visual inspection of PS1 images in the g, r, i and z bands in a 5 × 5 arcmin2 region around X-ray sources detected in the ROSAT All-Sky Survey (RASS). To test and optimize the eMACS X-ray selection criteria, our pilot study uses the largest possible RASS data base, i.e. all RASS sources listed in the Bright and Faint Source Catalogues (BSC and FSC) that fall within the MDS footprint. We apply no additional constraints regarding X-ray flux, spectral hardness ratio or photon statistics and lower the redshift threshold to z > 0.3 to extend the probed luminosity range to poorer systems. Scrutiny of PS1/MDS images for 41 BSC and 200 FSC sources combined with dedicated spectroscopic follow-up observations results in a sample of 11 clusters with estimated or spectroscopic redshifts of z > 0.3. In order to assess and quantify the degree of point source contamination of the observed RASS fluxes, we examine archival Chandra data obtained in targeted and serendipitous observations of six of the 11 clusters found. As expected, the diffuse emission from all six systems is contaminated by point sources to some degree, and for half of them active galactic nucleus emission dominates. X-ray follow-up observations will thus be crucial in order to establish robust cluster luminosities for eMACS clusters. Although the small number of distant X-ray luminous clusters in the MDS does not allow us to make firm predictions for the over 20 000 deg2 of extragalactic sky covered by eMACS, the identification of two extremely promising eMACS cluster candidates at z ≳ 0.6 (both yet to be observed with Chandra) in such a small solid angle is encouraging

  8. An empirical study of the relationship between Lyα and UV-selected galaxies: do theorists and observers 'select' the same objects?

    NASA Astrophysics Data System (ADS)

    Dijkstra, Mark; Wyithe, J. Stuart B.

    2012-02-01

    Lyman α emitters (LAEs) are galaxies that have been selected on the basis of a strong Lyα emission line in their spectra. Observational campaigns over the last decade have dramatically increased the sample of known LAEs, which now extends out to z= 7. These discoveries have motivated numerous theoretical studies on the subject, which usually define LAEs in their models based on sharp Lyα luminosity and equivalent width (EW) cuts. While broadly representative, this procedure does not mimic the selection from observational programmes in detail, which instead use cuts in various colour spaces. In this paper, we investigate what implications this disjoint may have for theoretical studies that aim to model the observed population of LAEs. We construct an empirical model for the number density of star-forming galaxies as a function of their ultraviolet (UV) and Lyα luminosity, utilizing measured constraints on the luminosity functions of drop-out galaxies, and their luminosity-dependent probability distribution function of Lyα EW. In particular, we investigate whether the LAE luminosity functions can be reproduced by defining LAEs using a (z-dependent) Lyα luminosity and EW threshold. While we are able to reproduce the observed distribution of Lyα EW among LAEs out to rest-frame EW (REW) ˜ 200Å, we find that our formalism overpredicts both the UV and Lyα luminosity functions of LAEs by a factor of 2-3, and is inconsistent with observations at the ˜95 per cent level. This tension is partially resolved if we assume the Lyα EW distribution of drop-out galaxies to be truncated at REW ≳ 150 Å. However, the overprediction indicates that modelling LAEs with simple REW and luminosity cuts does not accurately mimic observed selection criteria, and can therefore lead to uncertainties in the predicted number density of LAEs. On the other hand, the predicted redshift evolution is not affected. We apply our formalism to drop-out galaxies at z > 6 and predict the

  9. Deep Hubble Space Telescope imaging of a compact radio galaxy at z = 2.390

    NASA Technical Reports Server (NTRS)

    Windhorst, Rogier; Mathis, Douglas F.; Keel, William C.

    1992-01-01

    The radio galaxy with the highest redshift in the Leiden-Berkeley Deep Survey, 53W002, is described and examined in terms of UV profile in relation to an early-type galaxy. The HST WFC images have a resolution of 0.2 arcsec FWHM, and the I- and V-band structures are assessed. The source is elongated in a manner similar to the Ly alpha cloud in V, and the structure is highly compact in I. The present object with a young starburst has very high central UV surface brightnesses relative to nearby luminous early-type galaxies, while the light profiles are similar. The data are concluded to suggest that 53W002 is a young galaxy that has a regular light profile at z = 2.390 even though it has been forming stars since not more than about 0.5 Gyr before z = 2.390. Such a scenario is consistent with concurrent dynamical collapse and star formation in the compact radio galaxy.

  10. VLT Smashes the Record of the Farthest Known Galaxy

    NASA Astrophysics Data System (ADS)

    2004-03-01

    most certainly the Lyman-alpha emission line typical of these objects. This line, which occurs in the laboratory at a wavelength of 0.1216 μm, that is, in the ultraviolet, has been stretched to the near infrared at 1.34 μm, making Abell 1835 IR1916 the first galaxy known to have a redshift as large as 10. The most distant galaxy known to date ESO PR Photo 05a/04 ESO PR Photo 05a/04 ISAAC images of Abell 1835 [Preview - JPEG: 405 x 400 pix - 240k] [Normal - JPEG: 810 x 800 pix - 760k] ESO PR Photo 05b/04 ESO PR Photo 05b/04 Two-dimensional spectra of Abell 1835 IR1936 [Preview - JPEG: 555 x 400 pix - 208k] [Normal - JPEG: 1110 x 800 pix - 570k] Captions: ESO PR Photo 05a/04 shows an ISAAC image in the near-infrared of the core of the lensing cluster Abell 1835 (upper) with the location of the galaxy Abell 1835 IR1916 (white circle). The thumbnail images at the bottom show the images of the remote galaxy in the visible R-band (HST-WPC image) and in the J-, H-, and K-bands. The fact that the galaxy is not detected in the visible image but present in the others - and more so in the H-band - is an indication that this galaxy has a redshift around 10. ESO PR Photo 05b/04 is a reproduction from two-dimensional spectra around the emission line at 1.33745 μm showing the detected emission line of Abell 1835 IR1916 (circle above). If identified as Ly-alpha (0.1216 μm), this leads to a redshift z=10. The line has been observed in two independent spectra corresponding to two different settings of the spectrograph: the right panels show the spectra in the short wavelength setting (centred on 1.315 μm), the long wavelength setting (centred on 1.365 μm), and in the composite, respectively. The line is seen in the dark circles. This is the strongest case for a redshift in excess of the current spectroscopically confirmed record at z=6.6 and the first case of a double-digit redshift. Scaling the age of the Universe to a person's lifetime (80 years, say), the previous confirmed

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  12. UV-CONTINUUM SLOPES AT z {approx} 4-7 FROM THE HUDF09+ERS+CANDELS OBSERVATIONS: DISCOVERY OF A WELL-DEFINED UV COLOR-MAGNITUDE RELATIONSHIP FOR z {>=} 4 STAR-FORMING GALAXIES

    SciTech Connect

    Bouwens, R. J.; Franx, M.; Labbe, I.; Smit, R.; Illingworth, G. D.; Oesch, P.A.; Gonzalez, V.; Magee, D.; Van Dokkum, P.; Carollo, C. M.

    2012-08-01

    Ultra-deep Advanced Camera for Surveys (ACS) and WFC3/IR HUDF+HUDF09 data, along with the wide-area GOODS+ERS+CANDELS data over the CDF-S GOODS field, are used to measure UV colors, expressed as the UV-continuum slope {beta}, of star-forming galaxies over a wide range of luminosity (0.1L*{sub z=3} to 2L*{sub z=3}) at high redshift (z {approx} 7 to z {approx} 4). {beta} is measured using all ACS and WFC3/IR passbands uncontaminated by Ly{alpha} and spectral breaks. Extensive tests show that our {beta} measurements are only subject to minimal biases. Using a different selection procedure, Dunlop et al. recently found large biases in their {beta} measurements. To reconcile these different results, we simulated both approaches and found that {beta} measurements for faint sources are subject to large biases if the same passbands are used both to select the sources and to measure {beta}. High-redshift galaxies show a well-defined rest-frame UV color-magnitude (CM) relationship that becomes systematically bluer toward fainter UV luminosities. No evolution is seen in the slope of the UV CM relationship in the first 1.5 Gyr, though there is a small evolution in the zero point to redder colors from z {approx} 7 to z {approx} 4. This suggests that galaxies are evolving along a well-defined sequence in the L{sub UV}-color ({beta}) plane (a 'star-forming sequence'?). Dust appears to be the principal factor driving changes in the UV color {beta} with luminosity. These new larger {beta} samples lead to improved dust extinction estimates at z {approx} 4-7 and confirm that the extinction is essentially zero at low luminosities and high redshifts. Inclusion of the new dust extinction results leads to (1) excellent agreement between the star formation rate (SFR) density at z {approx} 4-8 and that inferred from the stellar mass density; and (2) to higher specific star formation rates (SSFRs) at z {approx}> 4, suggesting that the SSFR may evolve modestly (by factors of {approx}2) from

  13. Joint scaling properties of Sunyaev-Zel'dovich and optical richness observables in an optically-selected galaxy cluster sample

    NASA Astrophysics Data System (ADS)

    Greer, Christopher Holland

    Galaxy cluster abundance measurements are an important tool used to study the universe as a whole. The advent of multiple large-area galaxy cluster surveys across multiple ensures that cluster measurements will play a key role in understanding the dark energy currently thought to be accelerating the universe. The main systematic limitation at the moment is the understanding of the observable-mass relation. Recent theoretical work has shown that combining samples of clusters from surveys at different wavelengths can mitigate this systematic limitation. Precise measurements of the scatter in the observable-mass relation can lead to further improvements. We present Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of the Sunyaev-Zel'dovich (SZ) signal for 28 galaxy clusters selected from the Sloan Digital Sky Survey (SDSS) maxBCG catalog. This cluster sample represents a complete, volume-limited sample of the richest galaxy clusters in the SDSS between redshifts 0.2 ≥ z ≥ 0.3, as measured by the RedMaPPer algorithm being developed for the Dark Energy Survey (DES; Rykoff et al. 2012). We develop a formalism that uses the cluster abundance in tandem with the galaxy richness measurements from SDSS and the SZ signal measurements from CARMA to calibrate the SZ and optical observable-mass relations. We find that the scatter in richness at fixed mass is σlog λ| M = 0.24+0.09-0.07 using SZ signal calculated by integrating a cluster pressure profile to a radius of 1 Mpc at the redshift of the cluster. We also calculate the SZ signal at R500 and find that the choice of scaling relation used to determined R500 has a non-trivial effect on the constraints of the observable-mass relationship. Finally, we investigate the source of disagreement between the positions of the SZ signal and SDSS Brightest Cluster Galaxies (BCGs). Improvements to the richness calculator that account for blue BCGs in the cores of cool-core X-ray clusters, as well as

  14. Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Lumninous Infrared Galaxy Candidates

    NASA Technical Reports Server (NTRS)

    Griffith, Roger L.; Kirkpatrick, J. Davy; Eisenhardt, Peter R. M.; Gelino, Christopher R.; Cushing, Michael C.; Benford, Dominic; Blain, Andrew; Bridge, Carrie R.; Cohen, Martin; Cutri, Roc M.; Donoso, Emilio; Jarrett, Thomas H.; Lonsdale, Carol; Mace, Gregory; Mainzer, A.; Marsh, Ken; Padgett, Deborah; Petty, Sara; Ressler, Michael E.; Skrutskie, Michael F.; Stanford, Spencer A.; Stern, Daniel; Tsai, Chao-Wei; Wright, Edward L.; Wu, Jingwen

    2012-01-01

    We present Spitzer 3.6 and 4.5 micrometer photometry and positions for a sample of 1510 brown dwarf candidates identified by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. Of these, 166 have been spectroscopically classified as objects with spectral types M(1), L(7), T(146), and Y(12). Sixteen other objects are non-(sub)stellar in nature. The remainder are most likely distant L and T dwarfs lacking spectroscopic verification, other Y dwarf candidates still awaiting follow-up, and assorted other objects whose Spitzer photometry reveals them to be background sources. We present a catalog of Spitzer photometry for all astrophysical sources identified in these fields and use this catalog to identify seven fainter (4.5 m to approximately 17.0 mag) brown dwarf candidates, which are possibly wide-field companions to the original WISE sources. To test this hypothesis, we use a sample of 919 Spitzer observations around WISE-selected high-redshift hyper-luminous infrared galaxy candidates. For this control sample, we find another six brown dwarf candidates, suggesting that the seven companion candidates are not physically associated. In fact, only one of these seven Spitzer brown dwarf candidates has a photometric distance estimate consistent with being a companion to the WISE brown dwarf candidate. Other than this, there is no evidence for any widely separated (greater than 20 AU) ultra-cool binaries. As an adjunct to this paper, we make available a source catalog of 7.33 x 10(exp 5) objects detected in all of these Spitzer follow-up fields for use by the astronomical community. The complete catalog includes the Spitzer 3.6 and 4.5 m photometry, along with positionally matched B and R photometry from USNO-B; J, H, and Ks photometry from Two Micron All-Sky Survey; and W1, W2, W3, and W4 photometry from the WISE all-sky catalog.

  15. A Complete X-ray Selected Sample of Galaxy Clusters from the ROSAT North Ecliptic Pole Survey

    NASA Astrophysics Data System (ADS)

    Mullis, C. R.; Henry, J. P.; Gioia, I. M.

    1997-12-01

    We are using the ROSAT All-Sky Survey observations around the North Ecliptic Pole to construct a complete and unbiased sample of galaxy clusters in order to understand the nature of cluster evolution and determine implications for large scale structure models. Our database is unique in that it is both deep and contiguous. Here we give an update on the survey's progress and discuss a few particularly exciting results. Via optical follow-up, we have secured identifications for nearly 80% of the 465 X-ray sources in the survey area. The cluster sample now consists of 50 objects with redshifts approaching unity. Evidence for large scale structure exists at both low and high redshifts in the NEP survey. A low-z spike in the redshift distribution for NEP clusters is consistent with a previously known supercluster at 0.088. At the other extreme, we recently discovered a very distant cluster at z=0.813 which resembles a filament of galaxies. Such a massive, un-virialized cluster at high-z may be the vision quest of cosmic-web proponents. For this potential protocluster, we present a velocity dispersion analysis of its member galaxies from Keck II observations and a temperature measurement from ASCA data. We construct the cluster X-ray luminosity function at high redshifts, incorporating a rigorous treatment of our survey selection function, and compare it to previous work.

  16. CONSTRAINTS ON THE IONIZING EFFICIENCY OF THE FIRST GALAXIES

    SciTech Connect

    Alvarez, Marcelo A.; Finlator, Kristian; Trenti, Michele

    2012-11-10

    Observations of the Ly{alpha} forest and of high-redshift galaxies at z {approx} 6-10 imply that there were just enough photons to maintain the universe in an ionized state at z {approx} 5-6, indicating a 'photon-starved' end to reionization. The ionizing emissivity must have been larger at earlier times in order to yield the extended reionization history implied by the electron scattering optical depth constraint from Wilkinson Microwave Anisotropy Probe (WMAP). Here we address the possibility that a faint population of galaxies with host halo masses of {approx}10{sup 8-9} M{sub Sun} dominated the ionizing photon budget at redshifts z {approx}> 9, due to their much higher escape fractions. Such faint, early galaxies, would not have formed in ionized regions due to suppression by heating from the UV background, and would therefore not contribute to the ionizing background at z {approx}< 6, after reionization is complete. Our model matches: (1) the low escape fractions observed for high-redshift galaxies, (2) the WMAP constraint of {tau}{sub es} {approx} 0.09, (3) the low values for the UVB at z < 6, and (4) the observed star formation rate density inferred from Lyman break galaxies. A top-heavy initial mass function from Pop III stars is not required in this scenario. We compare our model to recent ones in the literature that were forced to introduce an escape fraction that increases strongly toward high redshift and show that a similar evolution occurs naturally if low-mass galaxies possess high escape fractions.

  17. CO Emissions from Optically Selected Galaxies at z˜0.1-0.2: Tight Anti-Correlation Between Molecular Gas Fraction and 4000 Angstrom Break Strength

    NASA Astrophysics Data System (ADS)

    Morokuma-Matsui, K.; Baba, J.; Sorai, K.; Kuno, N.

    2015-12-01

    We performed 12CO(J=1-0) (hereafter, CO) observations towards 12 normal star-forming galaxies with M⋆=1010.6-1011.3 M⊙ at z=0.1-0.2 with the 45-m telescope at the Nobeyama Radio Observatory (NRO). The samples are selected with Dn(4000) that is a measure of the 4000 Angstrom break strength, instead of commonly used far-infrared (FIR) flux. We detect the CO emissions from 8 galaxies with signal-to-noise ratio (S/N) larger than 3, demonstrating the effectiveness of the Dn(4000)-based sample selection. We find a tight anti-correlation between Dn(4000) and molecular gas fraction (fmol) using literature data of nearby galaxies in which the galaxies with more fuel for star formation have younger stellar populations. CO-detected galaxies at z˜0.1-0.2 also follow the same relation of nearby galaxies, implying 1) the galaxies evolve along this Dn(4000)-fmol relation, and 2) Dn(4000) seems to be used as a proxy for fmol which requires many time-consuming observations1.

  18. THE CIRCUMGALACTIC MEDIUM OF MASSIVE GALAXIES AT z {approx} 3: A TEST FOR STELLAR FEEDBACK, GALACTIC OUTFLOWS, AND COLD STREAMS

    SciTech Connect

    Shen Sijing; Madau, Piero; Prochaska, J. Xavier; Guedes, Javiera; Mayer, Lucio; Wadsley, James

    2013-03-10

    We present new results on the kinematics, thermal and ionization state, and spatial distribution of metal-enriched gas in the circumgalactic medium (CGM) of massive galaxies at redshift {approx}3, using the Eris suite of cosmological hydrodynamic ''zoom-in'' simulations. The reference run adopts a blastwave scheme for supernova feedback that produces large-scale galactic outflows, a star formation recipe based on a high gas density threshold, metal-dependent radiative cooling, and a model for the diffusion of metals and thermal energy. The effect of the local UV radiation field is added in post-processing. The CGM (defined as all gas at R > 0.2 R{sub vir} = 10 kpc, where R{sub vir} is the virial radius) contains multiple phases having a wide range of physical conditions, with more than half of its heavy elements locked in a warm-hot component at T > 10{sup 5} K. Synthetic spectra, generated by drawing sightlines through the CGM, produce interstellar absorption-line strengths of Ly{alpha}, C II, C IV, Si II, and Si IV as a function of the galactocentric impact parameter (scaled to the virial radius) that are in broad agreement with those observed at high redshift by Steidel et al. The covering factor of absorbing material declines less rapidly with impact parameter for Ly{alpha} and C IV compared to C II, Si IV, and Si II, with Ly{alpha} remaining strong (W{sub Ly{alpha}} > 300 mA) to {approx}> 5 R{sub vir} = 250 kpc. Only about one third of all the gas within R{sub vir} is outflowing. The fraction of sightlines within one virial radius that intercept optically thick, N{sub H{sub I}}>10{sup 17.2} cm{sup -2} material is 27%, in agreement with recent observations by Rudie et al. Such optically thick absorption is shown to trace inflowing ''cold'' streams that penetrate deep inside the virial radius. The streams, enriched to metallicities above 0.01 solar by previous episodes of star formation in the main host and in nearby dwarfs, are the origin of strong (N{sub C

  19. An unusual red envelope galaxy in an X-ray selected cluster.

    NASA Astrophysics Data System (ADS)

    Gioia, I. M.; Garilli, B.; Maccacaro, T.; Maccagni, D.; Vettolani, G.; Wolter, A.

    In the process of identifying X-ray sources from the Einstein Observatory Extended Medium Sensitivity Survey, the authors have observed the field of 1E 1111.9-3754. A photometric and spectroscopic study of the optical counterpart of the X-ray source 1E 1111.9-3754 has revealed a poor cluster of galaxies dominated by a very luminous giant elliptical. The galaxy sits at the bottom of the potential well described by the X-ray emitting gas. The presence of such a bright and large galaxy in this cluster can be explained by invoking cannibalism and stripping in this specific environment which may be at the origin of the large, red envelope detected in the Gunn i and r filters. The authors have given the name GREG (Giant Red Envelope Galaxy) to the brightest cluster member of 1E 1111.9-3754. A Hubble constant of 50 km s-1Mpc-1 and q0 = 0 have been used, implying a scale of 3.17 kpc arcsec-1 at GREG's redshift.

  20. Host Galaxy Properties of BAT Hard X-ray Selected AGN

    NASA Astrophysics Data System (ADS)

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa

    2010-07-01

    Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of 246 AGN unaffected by galactic or circumnuclear absorption [1]. Most of the sources in the survey are bright, Seyfert like AGN's with median redshift of 0.03. Of the AGN, 43% are obscured, type II AGN. We obtained 17 nights of imaging of 90 host galaxies of these AGN in 2008 at the Kitt Peak 2.1 m telescope in the SDSS ugriz filters. For the broad line sources we subtracted the AGN contribution using GALFIT. By comparing our sample of AGN to inactive galaxies in the SDSS, we find that AGN are found in the most massive galaxies and are bluer in color than inactive galaxies of comparable stellar mass. We also find a correlation between the point source optical light and hard X-ray luminosity.

  1. Host Galaxy Properties of BAT Hard X-ray Selected AGN

    SciTech Connect

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa

    2010-07-15

    Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of 246 AGN unaffected by galactic or circumnuclear absorption [1]. Most of the sources in the survey are bright, Seyfert like AGN's with median redshift of 0.03. Of the AGN, 43% are obscured, type II AGN. We obtained 17 nights of imaging of 90 host galaxies of these AGN in 2008 at the Kitt Peak 2.1 m telescope in the SDSS ugriz filters. For the broad line sources we subtracted the AGN contribution using GALFIT. By comparing our sample of AGN to inactive galaxies in the SDSS, we find that AGN are found in the most massive galaxies and are bluer in color than inactive galaxies of comparable stellar mass. We also find a correlation between the point source optical light and hard X-ray luminosity.

  2. New Constraints on Galaxy Cluster Evolution from Chandra Observations of SPT-Selected Clusters

    NASA Astrophysics Data System (ADS)

    McDonald, M.

    2014-07-01

    In the past 4 years, the number of known galaxy clusters at z>0.5 has grown by a factor of >5, thanks primarily to Sunyaev Zel'dovich surveys such as Planck, the Atacama Cosmology Telescope, and the South Pole Telescope (SPT). Here, I present several important results from the SPT 2500 deg^2 survey, which has discovered over 500 new galaxy clusters, more than 300 of which are at z>0.5. Using data primarily from the Chandra X-ray Observatory, we determine evolutionary trends in the central cluster galaxy (inner ˜20 kpc), the cluster core (inner ˜100 kpc), and cluster outskirts (>1 Mpc) over the past 8 Gyr, addressing such outstanding issues as the cooling flow problem, the effects of AGN feedback, and subhalo accretion, or clumping, at the virial radius. These studies are providing the most detailed constraints to date on the evolution of galaxy clusters on all physical scales, and will continue to improve with the next generation of surveys already upon us.

  3. A Detailed Analysis of the Multi-Velocity Components of strong HI-selected absorbers in the Halos of z~0.5 Galaxies

    NASA Astrophysics Data System (ADS)

    Vanderhoof, Brittany; Ribaudo, Joseph; Lehner, Nicolas; Howk, J. Christopher

    2016-01-01

    One driving force of galaxy evolution is the presence and circulation of material throughout the extended gaseous environment of a galaxy, the circumgalactic material (CGM). In the Milky Way, high-velocity clouds (HVC) are well studied systems that trace outflows, inflows, and recycled material throughout the CGM. We examine archival QSO spectra from HST/COS in an effort to similarly identify absorption systems with high-velocity absorption relative to the rest-frame of a strong HI-selected absorber in order to dissect the various components and their origins in the halos of z~0.5 galaxies.

  4. HALO GAS AND GALAXY DISK KINEMATICS OF A VOLUME-LIMITED SAMPLE OF Mg II ABSORPTION-SELECTED GALAXIES AT z {approx} 0.1

    SciTech Connect

    Kacprzak, Glenn G.; Cooke, Jeff; Churchill, Christopher W.; Barton, Elizabeth J. E-mail: jcooke@astro.swin.edu.au E-mail: ebarton@uci.edu

    2011-06-01

    We have directly compared Mg II halo gas kinematics to the rotation velocities derived from emission/absorption lines of the associated host galaxies. Our 0.096 {<=} z {<=} 0.148 volume-limited sample comprises 13 {approx}L{sub *} galaxies, with impact parameters of 12-90 kpc from background quasar sight lines, associated with 11 Mg II absorption systems with Mg II equivalent widths 0.3 A {<=} W{sub r} (2796) {<=} 2.3 A. For only 5/13 galaxies, the absorption resides to one side of the galaxy systemic velocity and trends to align with one side of the galaxy rotation curve. The remainder have absorption that spans both sides of the galaxy systemic velocity. These results differ from those at z {approx} 0.5, where 74% of the galaxies have absorption residing to one side of the galaxy systemic velocity. For all the z {approx} 0.1 systems, simple extended disk-like rotation models fail to reproduce the full Mg II velocity spread, implying that other dynamical processes contribute to the Mg II kinematics. In fact 55% of the galaxies are 'counter-rotating' with respect to the bulk of the Mg II absorption. These Mg II host galaxies are isolated, have low star formation rates (SFRs) in their central regions ({approx}< 1 M{sub sun} yr{sup -1}), and SFRs per unit area well below those measured for galaxies with strong winds. The galaxy Na ID (stellar+ISM) and Mg Ib (stellar) absorption line ratios are consistent with a predominately stellar origin, implying kinematically quiescent interstellar media. These facts suggest that the kinematics of the Mg II absorption halos for our sample of galaxies are not influenced by galaxy-galaxy environmental effects, nor by winds intrinsic to the host galaxies. For these low-redshift galaxies, we favor a scenario in which infalling gas accretion provides a gas reservoir for low-to-moderate SFRs and disk/halo processes.

  5. A New Search for Variability-Selected Active Galaxies Within the VST SUDARE-VOICE Survey: The Chandra Deep Field South and the SERVS-SWIRE Area

    NASA Astrophysics Data System (ADS)

    Falocco, S.; De Cicco, D.; Paolillo, M.; Covone, G.; Longo, G.; Grado, A.; Limatola, L.; Vaccari, M.; Botticella, M. T.; Pignata, G.; Cappellaro, E.; Trevese, D.; Vagnetti, F.; Salvato, M.; Radovich, M.; Hsu, L.; Brandt, W. N.; Capaccioli, M.; Napolitano, N.; Baruffolo, A.; Cascone, E.; Schipani, P.

    This work makes use of the VST observations to select variable sources. We use also the IR photometry, SED fitting and X-ray information where available to confirm the nature of the AGN candidates. The IR data, available over the full survey area, allow to confirm the consistency of the variability selection with the IR color selection method, while the detection of variability may prove useful to detect the presence of an AGN in IR selected starburst galaxies.

  6. The active galactic nucleus population in X-ray-selected galaxy groups at 0.5 < Z < 1.1

    SciTech Connect

    Oh, Semyeong; Woo, Jong-Hak; Matsuoka, Kenta; Mulchaey, John S.; Finoguenov, Alexis; Tanaka, Masayuki; Cooper, Michael C.; Ziparo, Felicia; Bauer, Franz E.

    2014-07-20

    We use Chandra data to study the incidence and properties of active galactic nuclei (AGNs) in 16 intermediate redshift (0.5 < z < 1.1) X-ray-selected galaxy groups in the Chandra Deep Field-South. We measure an AGN fraction of f(L{sub X,H}>10{sup 42};M{sub R}<−20)=8.0{sub −2.3}{sup +3.0}% at z-bar ∼0.74, approximately a factor of two higher than the AGN fraction found for rich clusters at comparable redshift. This extends the trend found at low redshift for groups to have higher AGN fractions than clusters. Our estimate of the AGN fraction is also more than a factor of three higher than that of low redshift X-ray-selected groups. Using optical spectra from various surveys, we also constrain the properties of emission-line selected AGNs in these groups. In contrast to the large population of X-ray AGNs (N(L{sub X,{sub H}} > 10{sup 41} erg s{sup –1}) = 25), we find only four emission-line AGNs, three of which are also X-ray bright. Furthermore, most of the X-ray AGNs in our groups are optically dull (i.e., lack strong emission-lines), similar to those found in low redshift X-ray groups and clusters of galaxies. This contrasts with the AGN population found in low redshift optically selected groups which are dominated by emission-line AGNs. The differences between the optically and X-ray-selected AGNs populations in groups are consistent with a scenario where most AGNs in the densest environments are currently in a low accretion state.

  7. The Active Galactic Nucleus Population in X-Ray-selected Galaxy Groups at 0.5 < z < 1.1

    NASA Astrophysics Data System (ADS)

    Oh, Semyeong; Mulchaey, John S.; Woo, Jong-Hak; Finoguenov, Alexis; Tanaka, Masayuki; Cooper, Michael C.; Ziparo, Felicia; Bauer, Franz E.; Matsuoka, Kenta

    2014-07-01

    We use Chandra data to study the incidence and properties of active galactic nuclei (AGNs) in 16 intermediate redshift (0.5 < z < 1.1) X-ray-selected galaxy groups in the Chandra Deep Field-South. We measure an AGN fraction of f(LX,H \\gt 1042;MR < {-20}) = 8.0-2.3+3.0% at \\bar{z} ˜ 0.74, approximately a factor of two higher than the AGN fraction found for rich clusters at comparable redshift. This extends the trend found at low redshift for groups to have higher AGN fractions than clusters. Our estimate of the AGN fraction is also more than a factor of three higher than that of low redshift X-ray-selected groups. Using optical spectra from various surveys, we also constrain the properties of emission-line selected AGNs in these groups. In contrast to the large population of X-ray AGNs (N(L X, H > 1041 erg s-1) = 25), we find only four emission-line AGNs, three of which are also X-ray bright. Furthermore, most of the X-ray AGNs in our groups are optically dull (i.e., lack strong emission-lines), similar to those found in low redshift X-ray groups and clusters of galaxies. This contrasts with the AGN population found in low redshift optically selected groups which are dominated by emission-line AGNs. The differences between the optically and X-ray-selected AGNs populations in groups are consistent with a scenario where most AGNs in the densest environments are currently in a low accretion state.

  8. Rotation of halos in open and closed universes - differentiated merging and natural selection of galaxy types

    SciTech Connect

    Zurek, W.H.; Quinn, P.J.; Salmon, J.K.

    1988-07-01

    Computer simulations are used here to study the properties of galactic halos formed from Gaussian initial density perturbations in both open and closed dark matter universes. It is shown that if galaxies form through gravitational collapse from initial, Gaussian density perturbations, then their luminous parts do not have the original values of either specific angular momentum (ellipticals) or spin parameter lambda (spirals). The rotational properties of a halo depend only weakly on either the halo density or the density of its environment. Variations of the large-scale density of the environment have an expected, dramatic effect on the density of individual halos. Dissipationless merging forces the cores of the merging objects into the core of the merger product. In the process, cores become more bound and lose angular momentum. These findings are extrapolated to propose a model for galaxy formation in which both ellipticals and spirals come into being through mergers. 59 references.

  9. Redshift Survey of Galaxies around a Selected Sample of Compact Groups

    NASA Astrophysics Data System (ADS)

    de Carvalho, Reinaldo R.; Ribeiro, André L. B.; Capelato, Hugo V.; Zepf, Stephen E.

    We report the results of a spectroscopic survey of faint galaxies in the regions surrounding Hickson compact groups. Our sample is composed of 17 groups within 9000 km s-1. The spectra were taken at the prime focus of the Tololo 4 m telescope, using the ARGUS fiber-fed spectrograph. From these observations, redshifts were determined for the faint galaxies previously identified by de Carvalho, Ribeiro, & Zepf in the surroundings of the groups. Statistical methods were applied to the resultant catalog in order to determine the kinematical structure of each group. This analysis confirms the idea that the Hickson sample of compact groups contains a wide variety of projection and dynamical configurations. Our results demonstrate the necessity of new spectroscopic surveys around compact groups in order to assess their complete velocity distribution.

  10. Rest-frame Optical Emission Lines in Far-infrared-selected Galaxies at z < 1.7 from the FMOS-COSMOS Survey

    NASA Astrophysics Data System (ADS)

    Kartaltepe, Jeyhan S.; Sanders, D. B.; Silverman, J. D.; Kashino, D.; Chu, J.; Zahid, H.; Hasinger, G.; Kewley, L.; Matsuoka, K.; Nagao, T.; Riguccini, L.; Salvato, M.; Schawinski, K.; Taniguchi, Y.; Treister, E.; Capak, P.; Daddi, E.; Ohta, K.

    2015-06-01

    We have used FMOS on Subaru to obtain near-infrared spectroscopy of 123 far-infrared-selected galaxies in COSMOS and the key rest-frame optical emission lines. This is the largest sample of infrared galaxies with near-infrared spectroscopy at these redshifts. The far-infrared selection results in a sample of galaxies that are massive systems that span a range of metallicities in comparison with previous optically selected surveys, and thus has a higher active galactic nucleus (AGN) fraction and better samples the AGN branch. We establish the presence of AGNs and starbursts in this sample of (U)LIRGs selected as Herschel-PACS and Spitzer-MIPS detections in two redshift bins (z∼ 0.7 and z∼ 1.5) and test the redshift dependence of diagnostics used to separate AGNs from star formation dominated galaxies. In addition, we construct a low-redshift (z∼ 0.1) comparison sample of infrared-selected galaxies and find that the evolution from z∼ 1.5 to today is consistent with an evolving AGN selection line and a range of ISM conditions and metallicities from the models of Kewley et al. We find that a large fraction of (U)LIRGs are BPT-selected AGNs using their new redshift-dependent classification line. We compare the position of known X-ray-detected AGNs (67 in total) with the BPT selection and find that the new classification line accurately selects most of these objects (\\gt 70%). Furthermore, we identify 35 new (likely obscured) AGNs not selected as such by their X-ray emission. Our results have direct implications for AGN selection at higher redshift with either current (MOSFIRE, KMOS) or future (PFS, MOONS) spectroscopic efforts with near-infrared spectral coverage.

  11. The SCUBA HAlf Degree Extragalactic Survey (SHADES) - V. Submillimetre properties of near-infrared-selected galaxies in the Subaru/XMM -Newton deep field

    NASA Astrophysics Data System (ADS)

    Takagi, T.; Mortier, A. M. J.; Shimasaku, K.; Coppin, K.; Pope, A.; Ivison, R. J.; Hanami, H.; Serjeant, S.; Clements, D. L.; Priddey, R. S.; Dunlop, J. S.; Takata, T.; Aretxaga, I.; Chapman, S. C.; Eales, S. A.; Farrah, D.; Granato, G. L.; Halpern, M.; Hughes, D. H.; van Kampen, E.; Scott, D.; Sekiguchi, K.; Smail, I.; Vaccari, M.

    2007-11-01

    We have studied the submillimetre (submm) properties of the following classes of near-infrared-selected (NIR-selected) massive galaxies at high redshifts: BzK-selected star-forming galaxies (BzKs); distant red galaxies (DRGs); and extremely red objects (EROs). We used the SCUBA HAlf Degree Extragalactic Survey (SHADES), the largest uniform submm survey to date. Partial overlap of SIRIUS/NIR images and SHADES in Subaru/XMM-Newton deep field has allowed us to identify four submm-bright NIR-selected galaxies, which are detected in the mid-IR, 24μ m, and the radio, 1.4GHz. We find that all of our submm-bright NIR-selected galaxies satisfy the BzK selection criteria, i.e. BzK ≡ (z - K)AB - (B - z)AB >= -0.2, except for one galaxy whose B - z and z - K colours are however close to the BzK colour boundary. Two of the submm-bright NIR-selected galaxies satisfy all of the selection criteria we considered, i.e. they belong to the BzK-DRG-ERO overlapping population, or `extremely red' BzKs. Although these extremely red BzKs are rare (0.25 arcmin-2), up to 20 per cent of this population could be submm galaxies. This fraction is significantly higher than that found for other galaxy populations studied here. Via a stacking analysis, we have detected the 850-μ m flux of submm-faint BzKs and EROs in our SCUBA maps. While the contribution of z ~ 2 BzKs to the submm background is about 10-15 per cent and similar to that from EROs typically at z ~ 1, BzKs have a higher fraction (~30 per cent) of submm flux in resolved sources compared with EROs and submm sources as a whole. From the spectral energy distribution (SED) fitting analysis for both submm-bright and submm-faint BzKs, we found no clear signature that submm-bright BzKs are experiencing a specifically luminous evolutionary phase, compared with submm-faint BzKs. An alternative explanation might be that submm-bright BzKs are more massive than submm-faint ones.

  12. Emission-line-selected galaxies at z = 0.6-2 in GOODS South: Stellar masses, SFRs, and large-scale structure

    NASA Astrophysics Data System (ADS)

    Kochiashvili, I.; Møller, P.; Milvang-Jensen, B.; Christensen, L.; Fynbo, J. P. U.; Freudling, W.; Clément, B.; Cuby, J.-G.; Zabl, J.; Zibetti, S.

    2015-08-01

    We have obtained deep NIR narrow and broad (J and Y) band imaging data of the GOODS-South field. The narrow band filter is centered at 1060 nm corresponding to redshifts z = 0.62,1.15,1.85 for the strong emission lines Hα, [Oiii]/Hβ and [Oii], respectively. From those data we extract a well defined sample (M(AB) = 24.8 in the narrow band) of objects with large emission line equivalent widths in the narrow band. Via SED fits to published broad band data we identify which of the three lines we have detected and assign redshifts accordingly. This results in a well defined, strong emission line selected sample of galaxies down to lower masses than can easily be obtained with only continuum flux limited selection techniques. We compare the (SED fitting-derived) main sequence of star-formation (MS) of our sample to previous works and find that it has a steeper slope than that of samples of more massive galaxies. We conclude that the MS steepens at lower (below M⋆ = 109.4M⊙) galaxy masses. We also show that the SFR at any redshift is higher in our sample. We attribute this to the targeted selection of galaxies with large emission line equivalent widths, and conclude that our sample forms the upper boundary of the MS. We briefly investigate and outline how samples with accurate redshifts down to those low stellar masses open a new window to study the formation of large scale structure in the early universe. In particular we report on the detection of a young galaxy cluster at z = 1.85 which features a central massive galaxy which is the candidate of an early stage cD galaxy, and we identify a likely filament mapped out by [Oiii] and Hβ emitting galaxies at z = 1.15. Tables 1 and 2, and Appendix A are available in electronic form at http://www.aanda.org

  13. Predicting Ly-alpha intensities in coronal streamers

    NASA Technical Reports Server (NTRS)

    Noci, Giancarlo; Poletto, Giannina; Suess, Steven T.; Wang, A.-H.; Wu, S. T.

    1992-01-01

    SOHO (Solar and Heliospheric Observatory) UVCS (Ultraviolet Coronagraph Spectrometer) will make long term observations of coronal streamers in UV lines, providing a new tool for the analysis of structures which have been known for decades but are still far from being adequately described. Work to evaluate the Lyman alpha brightness of coronal streamers is reported, adopting the streamer models obtained, via a time dependent numerical relaxation technique. This will yield understanding on the role of geometric versus physical factors in determining the streamer lyman alpha intensity and provide guidelines for UVCS observational operations. Future prospects along this line of research are summarized.

  14. Spot the difference. Impact of different selection criteria on observed properties of passive galaxies in zCOSMOS-20k sample

    NASA Astrophysics Data System (ADS)

    Moresco, M.; Pozzetti, L.; Cimatti, A.; Zamorani, G.; Bolzonella, M.; Lamareille, F.; Mignoli, M.; Zucca, E.; Lilly, S. J.; Carollo, C. M.; Contini, T.; Kneib, J.-P.; Le Fèvre, O.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Bongiorno, A.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Kovač, K.; Le Borgne, J.-F.; Le Brun, V.; Maier, C.; Pelló, R.; Peng, Y.; Perez-Montero, E.; Presotto, V.; Silverman, J. D.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Barnes, L.; Bordoloi, R.; Cappi, A.; Diener, C.; Koekemoer, A. M.; Le Floc'h, E.; López-Sanjuan, C.; McCracken, H. J.; Nair, P.; Oesch, P.; Scarlata, C.; Scoville, N.; Welikala, N.

    2013-10-01

    Aims: We present the analysis of photometric, spectroscopic, and morphological properties for differently selected samples of passive galaxies up to z = 1 extracted from the zCOSMOS-20k spectroscopic survey. This analysis intends toexplore the dependence of galaxy properties on the selection criterion adopted, study the degree of contamination due to star-forming outliers, and provide a comparison between different commonly used selection criteria. This work is a first step to fully investigating the selection effects of passive galaxies for future massive surveys such as Euclid. Methods: We extracted from the zCOSMOS-20k catalog six different samples of passive galaxies, based on morphology (3336 "morphological" early-type galaxies), optical colors (4889 "red-sequence" galaxies and 4882 "red UVJ" galaxies), specific star-formation rate (2937 "quiescent" galaxies), a best fit to the observed spectral energy distribution (2603 "red SED" galaxies), and a criterion that combines morphological, spectroscopic, and photometric information (1530 "red & passive early-type galaxies"). For all the samples, we studied optical and infrared colors, morphological properties, specific star-formation rates (SFRs), and the equivalent widths of the residual emission lines; this analysis was performed as a function of redshift and stellar mass to inspect further possible dependencies. Results: We find that each passive galaxy sample displays a certain level of contamination due to blue/star-forming/nonpassive outliers. The morphological sample is the one that presents the higher percentage of contamination, with ~12-65% (depending on the mass range) of galaxies not located in the red sequence, ~25-80% of galaxies with a specific SFR up to ~25 times higher than the adopted definition of passive, and significant emission lines found in the median stacked spectra, at least for log (M/M⊙) < 10.25. The red & passive ETGs sample is the purest, with a percentage of contamination in color

  15. THE BOSS EMISSION-LINE LENS SURVEY (BELLS). I. A LARGE SPECTROSCOPICALLY SELECTED SAMPLE OF LENS GALAXIES AT REDSHIFT {approx}0.5

    SciTech Connect

    Brownstein, Joel R.; Bolton, Adam S.; Pandey, Parul; Schlegel, David J.; Eisenstein, Daniel J.; Kochanek, Christopher S.; Connolly, Natalia; Maraston, Claudia; Seitz, Stella; Wake, David A.; Wood-Vasey, W. Michael; Brinkmann, Jon; Schneider, Donald P.; Weaver, Benjamin A.

    2012-01-01

    We present a catalog of 25 definite and 11 probable strong galaxy-galaxy gravitational lens systems with lens redshifts 0.4 {approx}< z {approx}< 0.7, discovered spectroscopically by the presence of higher-redshift emission lines within the Baryon Oscillation Spectroscopic Survey (BOSS) of luminous galaxies, and confirmed with high-resolution Hubble Space Telescope (HST) images of 44 candidates. Our survey extends the methodology of the Sloan Lens Advanced Camera for Surveys survey (SLACS) to higher redshift. We describe the details of the BOSS spectroscopic candidate detections, our HST ACS image processing and analysis methods, and our strong gravitational lens modeling procedure. We report BOSS spectroscopic parameters and ACS photometric parameters for all candidates, and mass-distribution parameters for the best-fit singular isothermal ellipsoid models of definite lenses. Our sample to date was selected using only the first six months of BOSS survey-quality spectroscopic data. The full five-year BOSS database should produce a sample of several hundred strong galaxy-galaxy lenses and in combination with SLACS lenses at lower redshift, strongly constrain the redshift evolution of the structure of elliptical, bulge-dominated galaxies as a function of luminosity, stellar mass, and rest-frame color, thereby providing a powerful test for competing theories of galaxy formation and evolution.

  16. Spectroscopic study in the visible and near infrared wavelength of an Hα-selected sample of star-forming galaxies at z = 0.84

    NASA Astrophysics Data System (ADS)

    Sánchez de Miguel, A.; Gallego, J.; Villar, V.; Pérez-González, P. G.; Zamorano, J.; Cardiel, N.; Acosta Pulido, J. A.

    2013-05-01

    In this work we study the physical properties of star-forming galaxies selected in an Hα near-infrared narrow-band survey tuned for redshift z=0.84 (Villar et al. 2008, 2011). Also, we present a sample at z˜1 with mass greater than 10^{10} M_{⊙} with Hα emission. The observations were carried out with WHT/LIRIS (see Sánchez de Miguel et al. 2011, in Highlights of Spanish Astrophysics VI). The rest of the data from the spectra archive of the RAINBOW Cosmological Survey database (Pérez-González et al. 2005, 2008; Barro et al. 2011ab). According to the redshift distribution of these galaxies, 65% of the galaxies are in a redshift range of 0.005. This velocity range corresponds to less than 25% of the effective volume. Which could be indicative of the presence of substructure. A total of 48 galaxies have detected Hα emission and other 12 show [NII]6584. To complete our multi-wavelength sample we found 23 galaxies with Hβ, [OIII]5007 or [OII]3727 detections. Using this photometry from ancillary data we will calculate nebular and stellar extinctions. We have calculated metallicities using the [NII]/Hα ratio and the Pettini & Pagel (2004) calibrations. The metallicity of samples are compatible with the local galaxies. We found that in all the diagnostic diagrams galaxies have similar properties to the local ones, except they are intrinsically brighter for the same equivalent width [OII]3727.

  17. A comparative study of radio halo occurrence in SZ and X-ray selected galaxy cluster samples

    NASA Astrophysics Data System (ADS)

    Sommer, Martin W.; Basu, Kaustuv

    2014-01-01

    We aim at an unbiased census of the radio halo population in galaxy clusters and test whether current low number counts of radio haloes have arisen from selection biases. We construct near-complete samples based on X-ray and Sunyaev-Zel'dovich (SZ) effect cluster catalogues and search for diffuse, extended (Mpc-scale) emission near the cluster centres by analysing data from the National Radio Astronomy Observatory Very Large Array Sky Survey. We remove compact sources using a matched filtering algorithm and model the diffuse emission using two independent methods. The relation between radio halo power at 1.4 GHz and mass observables is modelled using a power law, allowing for a `dropout' population of clusters hosting no radio halo emission. An extensive suite of simulations is used to check for biases in our methods. Our findings suggest that the fraction of targets hosting radio haloes may have to be revised upwards for clusters selected using the SZ effect: while approximately 60 per cent of the X-ray selected targets are found to contain no extended radio emission, in agreement with previous findings, the corresponding fraction in the SZ selected samples is roughly 20 per cent. We propose a simple explanation for this selection difference based on the distinct time evolution of the SZ and X-ray observables during cluster mergers, and a bias towards relaxed, cool-core clusters in the X-ray selection.

  18. Induced star formation and morphological evolution in very high redshift radio galaxies

    SciTech Connect

    van Breugel, W.J.M., LLNL

    1997-10-01

    Near-infrared, sub-arcsecond seeing images obtained with the W M Keck I Telescope of show strong evolution at rest-frame optical wavelengths in the morphologies of high redshift radio galaxies (HzRGs) with 1 9 < z < 4 4 The structures change from large-scale low surface brightness regions surrounding bright, multiple component and often radio-aligned features at z > 3, to much more compact and symmetrical shapes at z < 3 The linear sizes ({approximately} 10 kpc) and luminosities (M{sub B} {approximately} -20 to -22) of the individual components in the z > 3 HzRGs are similar to the total sizes and luminosities of normal, radio-quiet, star forming galaxies seen at z = 3 - 4 `R`-band, 0 1`` resolution images with the Hubble Space Telescope of one of these HzRGs, 4C41 17 at z = 3 800, show that at rest-frame UV wavelengths the galaxy morphology breaks up in even smaller, {approximately} 1 kpc-sized components embedded in a large halo of low suface brightness emission The brightest UV emission is from a radio-aligned, edge-brightened feature (4C41 17.North) downstream from a bright radio knot A narrow-band Ly-{alpha} image, also obtained with HST, shows an arc-shaped Ly-{alpha} feature at this same location, suggestive of a strong jet/cloud collision Deep spectropolarimetric observations with the W M Keck II Telescope of 4C41 17 show that the radio-aligned UV continuum is unpolarized Instead the total light spectrum shows ahsorption lines and P-Cygni type features that are similar to the radio-quiet z = 3 - 4 star forming galaxies This shows that the rest-frame UV light in 4C41 17 is dominated by starlight, not scattered light from a hidden AGN The combined HST and Keck data suggest that the radio--aligned rest-frame UV continuum is probably caused by jet-induced star formation The strong morphological evolution suggests that we see the first evidence for the assemblage of massive ellipticals, the parent population of very powerful radio sources at much lower redshifts

  19. SEARCH FOR GAMMA-RAY EMISSION FROM X-RAY-SELECTED SEYFERT GALAXIES WITH FERMI-LAT

    SciTech Connect

    Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Berenji, B.; Bloom, E. D.; Borgland, A. W.; Buehler, R.; Cameron, R. A.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Ballet, J.; Bastieri, D.; Buson, S.; Bonamente, E.; Brigida, M.; Bruel, P.; and others

    2012-03-10

    We report on a systematic investigation of the {gamma}-ray properties of 120 hard X-ray-selected Seyfert galaxies classified as 'radio-quiet' objects, utilizing the three-year accumulation of Fermi Large Area Telescope (LAT) data. Our sample of Seyfert galaxies is selected using the Swift Burst Alert Telescope 58 month catalog, restricting the analysis to the bright sources with average hard X-ray fluxes F{sub 14-195keV} {>=} 2.5 Multiplication-Sign 10{sup -11} erg cm{sup -2} s{sup -1} at high Galactic latitudes (|b| > 10 Degree-Sign ). In order to remove 'radio-loud' objects from the sample, we use the 'hard X-ray radio loudness parameter', R{sub rX}, defined as the ratio of the total 1.4 GHz radio to 14-195 keV hard X-ray energy fluxes. Among 120 X-ray bright Seyfert galaxies with R{sub rX} <10{sup -4}, we did not find a statistically significant {gamma}-ray excess (TS > 25) positionally coincident with any target Seyferts, with possible exceptions of ESO 323-G077 and NGC 6814. The mean value of the 95% confidence level {gamma}-ray upper limit for the integrated photon flux above 100 MeV from the analyzed Seyferts is {approx_equal} 4 Multiplication-Sign 10{sup -9} photons cm{sup -2} s{sup -1} , and the upper limits derived for several objects reach {approx_equal} 1 Multiplication-Sign 10{sup -9} photons cm{sup -2} s{sup -1} . Our results indicate that no prominent {gamma}-ray emission component related to active galactic nucleus activity is present in the spectra of Seyferts around GeV energies. The Fermi-LAT upper limits derived for our sample probe the ratio of {gamma}-ray to X-ray luminosities L{sub {gamma}}/L{sub X} < 0.1, and even <0.01 in some cases. The obtained results impose novel constraints on the models for high-energy radiation of 'radio-quiet' Seyfert galaxies.

  20. THE MASSIVE AND DISTANT CLUSTERS OF WISE SURVEY. II. INITIAL SPECTROSCOPIC CONFIRMATION OF z ∼ 1 GALAXY CLUSTERS SELECTED FROM 10,000 deg{sup 2}

    SciTech Connect

    Stanford, S. A.; Gonzalez, Anthony H.; Gettings, Daniel P.; Brodwin, Mark; Eisenhardt, Peter R. M.; Stern, Daniel; Wylezalek, Dominika

    2014-08-01

    We present optical and infrared imaging and optical spectroscopy of galaxy clusters which were identified as part of an all-sky search for high-redshift galaxy clusters, the Massive and Distant Clusters of WISE Survey (MaDCoWS). The initial phase of MaDCoWS combined infrared data from the all-sky data release of the Wide-field Infrared Survey Explorer (WISE) with optical data from the Sloan Digital Sky Survey to select probable z ∼ 1 clusters of galaxies over an area of 10,000 deg{sup 2}. Our spectroscopy confirms 19 new clusters at 0.7 < z < 1.3, half of which are at z > 1, demonstrating the viability of using WISE to identify high-redshift galaxy clusters. The next phase of MaDCoWS will use the greater depth of the AllWISE data release to identify even higher redshift cluster candidates.

  1. FINDING {eta} CAR ANALOGS IN NEARBY GALAXIES USING SPITZER. I. CANDIDATE SELECTION

    SciTech Connect

    Khan, Rubab; Stanek, K. Z.; Kochanek, C. S. E-mail: kstanek@astronomy.ohio-state.edu

    2013-04-10

    The late-stage evolution of the most massive stars such as {eta} Carinae is controlled by the effects of mass loss, which may be dominated by poorly understood eruptive mass ejections. Understanding this population is challenging because no true analogs of {eta} Car have been clearly identified in the Milky Way or other galaxies. We utilize Spitzer IRAC images of seven nearby ({approx}< 4 Mpc) galaxies to search for such analogs. We find 34 candidates with a flat or rising mid-IR spectral energy distributions toward longer mid-infrared wavelengths that emit >10{sup 5} L{sub Sun} in the IRAC bands (3.6 to 8.0 {mu}m) and are not known to be background sources. Based on our estimates for the expected number of background sources, we expect that follow-up observations will show that most of these candidates are not dust enshrouded massive stars, with an expectation of only 6 {+-} 6 surviving candidates. Since we would detect true analogs of {eta} Car for roughly 200 years post-eruption, this implies that the rate of eruptions like {eta} Car is less than the core-collapse supernova rate. It is possible, however, that every M > 40 M{sub Sun} star undergoes such eruptions given our initial results. In Paper II we will characterize the candidates through further analysis and follow-up observations, and there is no barrier to increasing the galaxy sample by an order of magnitude. The primary limitation of the present search is that Spitzer's resolution limits us to the shorter wavelength IRAC bands. With the James Webb Space Telescope, such surveys can be carried out at the far more optimal wavelengths of 10-30 {mu}m, allowing identification of {eta} Car analogs for millennia rather than centuries post-eruption.

  2. A Multiwavelength Study of a Sample of 70 μm Selected Galaxies in the COSMOS Field. II. The Role of Mergers in Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Kartaltepe, Jeyhan S.; Sanders, D. B.; Le Floc'h, E.; Frayer, D. T.; Aussel, H.; Arnouts, S.; Ilbert, O.; Salvato, M.; Scoville, N. Z.; Surace, J.; Yan, L.; Capak, P.; Caputi, K.; Carollo, C. M.; Cassata, P.; Civano, F.; Hasinger, G.; Koekemoer, A. M.; Le Fèvre, O.; Lilly, S.; Liu, C. T.; McCracken, H. J.; Schinnerer, E.; Smolčić, V.; Taniguchi, Y.; Thompson, D. J.; Trump, J.; Baldassare, V. F.; Fiorenza, S. L.

    2010-09-01

    We analyze the morphological properties of a large sample of 1503 70 μm selected galaxies in the COSMOS field spanning the redshift range 0.01 < z < 3.5 with a median redshift of 0.5 and an infrared luminosity range of 108 < L IR(8 - 1000 μm)< 1014 L sun with a median luminosity of 1011.4 L sun. In general, these galaxies are massive, with a stellar mass range of 1010-1012 M sun, and luminous, with -25 < M K < -20. We find a strong correlation between the fraction of major mergers and L IR, with the fraction at the highest luminosity (L IR > 1012 L sun) being up to ~50%. We also find that the fraction of spirals drops dramatically with L IR. Minor mergers likely play a role in boosting the infrared luminosity for sources with low luminosities (L IR < 1011.5 L sun). The precise fraction of mergers in any given L IR bin varies by redshift due to sources at z > 1 being difficult to classify and subject to the effects of bandpass shifting; therefore, these numbers can only be considered lower limits. At z < 1, where the morphological classifications are most robust, major mergers clearly dominate the ULIRG population (~50%-80%) and are important for the LIRG population (~25%-40%). At z > 1, the fraction of major mergers is lower, but is at least 30%-40% for ULIRGs. In a comparison of our visual classifications with several automated classification techniques we find general agreement; however, the fraction of identified mergers is underestimated due to automated classification methods being sensitive to only certain timescales of a major merger. Although the general morphological trends agree with what has been observed for local (U)LIRGs, the fraction of major mergers is slightly lower than seen locally. This is in part due to the difficulty of identifying merger signatures at high redshift. The distribution of the U - V color of the galaxies in our sample peaks in the green valley (langU - Vrang = 1.1) with a large spread at bluer and redder colors and with the

  3. RADIO GALAXY FEEDBACK IN X-RAY-SELECTED GROUPS FROM COSMOS: THE EFFECT ON THE INTRACLUSTER MEDIUM

    SciTech Connect

    Giodini, S.; Finoguenov, A.; Boehringer, H.; Pierini, D.; Smolcic, V.; Massey, R.; BIrzan, L.; Zamorani, G.; Oklopcic, A.; Pratt, G. W.; Koekemoer, A. M.; Salvato, M.; Sanders, D. B.; Kartaltepe, J. S.; Thompson, D.

    2010-05-01

    We quantify the importance of the mechanical energy released by radio galaxies inside galaxy groups. We use scaling relations to estimate the mechanical energy released by 16 radio-active galactic nuclei located inside X-ray-detected galaxy groups in the COSMOS field. By comparing this energy output to the host groups' gravitational binding energy, we find that radio galaxies produce sufficient energy to unbind a significant fraction of the intragroup medium. This unbinding effect is negligible in massive galaxy clusters with deeper potential wells. Our results correctly reproduce the breaking of self-similarity observed in the scaling relation between entropy and temperature for galaxy groups.

  4. Low Surface Brightness Galaxies Selected from the 40% Sky Area of the ALFALFA H I Survey. I. Sample and Statistical Properties

    NASA Astrophysics Data System (ADS)

    Du, Wei; Wu, Hong; Lam, Man I.; Zhu, Yinan; Lei, Fengjie; Zhou, Zhimin

    2015-06-01

    The population of low surface brightness (LSB) galaxies, which are objects with central surface brightnesses at least one magnitude fainter than the night sky, is crucial for understanding the extremes of galactic formation and evolution of the universe. As LSB galaxies are mostly rich in gas (H i), the α.40 Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) sample is one of the best survey combinations to select a sample of them in the local universe. Since the sky backgrounds are systematically overestimated for galactic images by the SDSS photometric pipeline, particularly for luminous galaxies or galaxies with extended LSB outskirts, in this paper, we above all estimated the sky backgrounds of SDSS images accurately in both the g and r bands for each galaxy in the α.40 SDSS DR7 sample, using a precise method of sky subtraction. Once subtracting the sky background, we did surface photometry with the Kron elliptical aperture using the SExtractor software and fitted geometric parameters with an exponential profile model using the Galfit software for each galactic image in the α.40 SDSS DR7 sample. Based on the photometric and geometric results, we further calculated the B-band central surface brightness, {{μ }0}(B), for each galaxy and ultimately defined a sample of LSB galaxies consisting of 1129 galaxies with {{μ }0}(B) > 22.5 mag arcsec-2 and the axis ratio b/a > 0.3 from the 12,423 α.40 SDSS DR7 galaxies. This H i-selected sample of LSB galaxies is a relatively unbiased sample of gas-rich and disk-dominated LSB galaxies, which is complete both in H i observation and the optical magnitude within the limit of the SDSS DR7 photometric survey. This LSB galactic sample spans from 22.5 to 28.3 in {{μ }0}(B) with a fraction of 4% fainter than 25.0 mag arcsec-2 in B-band central surface brightness and distributes from -27.0 to -12.3 mag in absolute magnitude in the B band (M(B)), including the 43 faintest galaxies (M(B) > -17.3 mag). This sample is a blue LSB

  5. Low Surface Brightness Galaxies Selected from the 40% Sky Area of the ALFALFA H I Survey. I. Sample and Statistical Properties

    NASA Astrophysics Data System (ADS)

    Du, Wei; Wu, Hong; Lam, Man I.; Zhu, Yinan; Lei, Fengjie; Zhou, Zhimin

    2015-06-01

    The population of low surface brightness (LSB) galaxies, which are objects with central surface brightnesses at least one magnitude fainter than the night sky, is crucial for understanding the extremes of galactic formation and evolution of the universe. As LSB galaxies are mostly rich in gas (H i), the α.40 Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) sample is one of the best survey combinations to select a sample of them in the local universe. Since the sky backgrounds are systematically overestimated for galactic images by the SDSS photometric pipeline, particularly for luminous galaxies or galaxies with extended LSB outskirts, in this paper, we above all estimated the sky backgrounds of SDSS images accurately in both the g and r bands for each galaxy in the α.40 SDSS DR7 sample, using a precise method of sky subtraction. Once subtracting the sky background, we did surface photometry with the Kron elliptical aperture using the SExtractor software and fitted geometric parameters with an exponential profile model using the Galfit software for each galactic image in the α.40 SDSS DR7 sample. Based on the photometric and geometric results, we further calculated the B-band central surface brightness, {{μ }0}(B), for each galaxy and ultimately defined a sample of LSB galaxies consisting of 1129 galaxies with {{μ }0}(B) > 22.5 mag arcsec‑2 and the axis ratio b/a > 0.3 from the 12,423 α.40 SDSS DR7 galaxies. This H i-selected sample of LSB galaxies is a relatively unbiased sample of gas-rich and disk-dominated LSB galaxies, which is complete both in H i observation and the optical magnitude within the limit of the SDSS DR7 photometric survey. This LSB galactic sample spans from 22.5 to 28.3 in {{μ }0}(B) with a fraction of 4% fainter than 25.0 mag arcsec‑2 in B-band central surface brightness and distributes from ‑27.0 to ‑12.3 mag in absolute magnitude in the B band (M(B)), including the 43 faintest galaxies (M(B) > ‑17.3 mag). This sample is

  6. SPIDERS: the spectroscopic follow-up of X-ray selected clusters of galaxies in SDSS-IV

    NASA Astrophysics Data System (ADS)

    Clerc, N.; Merloni, A.; Zhang, Y.-Y.; Finoguenov, A.; Dwelly, T.; Nandra, K.; Collins, C.; Dawson, K.; Kneib, J.-P.; Rozo, E.; Rykoff, E.; Sadibekova, T.; Brownstein, J.; Lin, Y.-T.; Ridl, J.; Salvato, M.; Schwope, A.; Steinmetz, M.; Seo, H.-J.; Tinker, J.

    2016-09-01

    SPIDERS (The SPectroscopic IDentification of eROSITA Sources) is a program dedicated to the homogeneous and complete spectroscopic follow-up of X-ray AGN and galaxy clusters over a large area (˜7500 deg2) of the extragalactic sky. SPIDERS is part of the SDSS-IV project, together with the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) and the Time-Domain Spectroscopic Survey (TDSS). This paper describes the largest project within SPIDERS before the launch of eROSITA: an optical spectroscopic survey of X-ray selected, massive (˜1014 to 1015~M⊙) galaxy clusters discovered in ROSAT and XMM-Newton imaging. The immediate aim is to determine precise (Δz ˜ 0.001) redshifts for 4,000-5,000 of these systems out to z ˜ 0.6. The scientific goal of the program is precision cosmology, using clusters as probes of large-scale structure in the expanding Universe. We present the cluster samples, target selection algorithms and observation strategies. We demonstrate the efficiency of selecting targets using a combination of SDSS imaging data, a robust red-sequence finder and a dedicated prioritization scheme. We describe a set of algorithms and work-flow developed to collate spectra and assign cluster membership, and to deliver catalogues of spectroscopically confirmed clusters. We discuss the relevance of line-of-sight velocity dispersion estimators for the richer systems. We illustrate our techniques by constructing a catalogue of 230 spectroscopically validated clusters (0.031 < z < 0.658), found in pilot observations. We discuss two potential science applications of the SPIDERS sample: the study of the X-ray luminosity-velocity dispersion (LX - σ) relation and the building of stacked phase-space diagrams.

  7. CLUSTERING PROPERTIES OF BzK-SELECTED GALAXIES IN GOODS-N: ENVIRONMENTAL QUENCHING AND TRIGGERING OF STAR FORMATION AT z {approx} 2

    SciTech Connect

    Lin Lihwai; Wang Weihao; Yan, Chi-Hung; Dickinson, Mark; Jian, Hung-Yu; Merson, A. I.; Baugh, C. M.; Helly, John; Lagos, Claudia del P; Scott, Douglas; Meger, Nicole; Foucaud, Sebastien; Yan Haojing; Cheng, Yi-Wen; Guo Yicheng; Pope, Alexandra; Kirsten, Franz; Koo, David C.; Simard, Luc; and others

    2012-09-01

    Using a sample of BzK-selected galaxies at z {approx} 2 identified from the CFHT/WIRCAM near-infrared survey of GOODS-North, we discuss the relation between star formation rate (SFR), specific star formation rate (SSFR), and stellar mass (M{sub *}), and the clustering of galaxies as a function of these parameters. For star-forming galaxies (sBzKs), the UV-based SFR, corrected for extinction, scales with the stellar mass as SFR{proportional_to}M{sup {alpha}}{sub *} with {alpha} = 0.74 {+-} 0.20 down to M{sub *} {approx} 10{sup 9} M{sub Sun }, indicating a weak dependence on the stellar mass of the SFR efficiency, namely, SSFR. We also measure the angular correlation function and hence infer the correlation length for sBzK galaxies as a function of M{sub *}, SFR, and SSFR, as well as K-band apparent magnitude. We show that passive galaxies (pBzKs) are more strongly clustered than sBzK galaxies at a given stellar mass, mirroring the color-density relation seen at lower redshifts. We also find that the correlation length of sBzK galaxies ranges from 4 to 20 h {sup -1} Mpc, being a strong function of M{sub K} , M{sub *}, and SFR. On the other hand, the clustering dependence on SSFR changes abruptly at 2 Multiplication-Sign 10{sup -9} yr{sup -1}, which is the typical value for 'main-sequence' star-forming galaxies at z {approx} 2. We show that the correlation length reaches a minimum at this characteristic value, and is larger for galaxies with both smaller and larger SSFRs; a dichotomy that is only marginally implied from the predictions of the semi-analytical models. Our results suggest that there are two types of environmental effects at work at z {approx} 2. Stronger clustering for relatively quiescent galaxies implies that the environment has started to play a role in quenching star formation. At the same time, stronger clustering for galaxies with elevated SSFRs ({sup s}tarbursts{sup )} might be attributed to an increased efficiency for galaxy interactions and

  8. AN EXPONENTIAL DECLINE AT THE BRIGHT END OF THE z = 6 GALAXY LUMINOSITY FUNCTION

    SciTech Connect

    Willott, Chris J.; McLure, Ross J.; Bruce, Victoria A.; Hibon, Pascale; McCracken, Henry J.; Kneib, Jean-Paul; Ilbert, Olivier; Bonfield, David G.; Jarvis, Matt J.

    2013-01-01

    We present the results of a search for the most luminous star-forming galaxies at redshifts z Almost-Equal-To 6 based on Canada-France-Hawaii Telescope Legacy Survey data. We identify a sample of 40 Lyman break galaxies (LBGs) brighter than magnitude z' = 25.3 across an area of almost 4 deg{sup 2}. Sensitive spectroscopic observations of seven galaxies provide redshifts for four, of which only two have moderate to strong Ly{alpha} emission lines. All four have clear continuum breaks in their spectra. Approximately half of the LBGs are spatially resolved in 0.7 arcsec seeing images, indicating larger sizes than lower luminosity galaxies discovered with the Hubble Space Telescope, possibly due to ongoing mergers. The stacked optical and infrared photometry is consistent with a galaxy model with stellar mass {approx}10{sup 10} M{sub Sun }. There is strong evidence for substantial dust reddening with a best-fit A{sub V} = 0.75 and A{sub V} > 0.48 at 2{sigma} confidence, in contrast to the typical dust-free galaxies of lower luminosity at this epoch. The spatial extent and spectral energy distribution suggest that the most luminous z Almost-Equal-To 6 galaxies are undergoing merger-induced starbursts. The luminosity function of z = 5.9 star-forming galaxies is derived. This agrees well with previous work and shows strong evidence for an exponential decline at the bright end, indicating that the feedback processes that govern the shape of the bright end are occurring effectively at this epoch.

  9. Characterization of SCUBA-2 450 μm and 850 μm selected galaxies in the COSMOS field

    NASA Astrophysics Data System (ADS)

    Casey, Caitlin M.; Chen, Chian-Chou; Cowie, Lennox L.; Barger, Amy J.; Capak, Peter; Ilbert, Olivier; Koss, Michael; Lee, Nicholas; Le Floc'h, Emeric; Sanders, David B.; Williams, Jonathan P.

    2013-12-01

    We present deep 450 μm and 850 μm observations of a large, uniformly covered 394 arcmin2 area in the Cosmic Evolution Survey (COSMOS) field obtained with the SCUBA-2 instrument on the James Clerk Maxwell Telescope (JCMT). We achieve root-mean-square noise values of σ450 = 4.13 mJy and σ850 = 0.80 mJy. The differential and cumulative number counts are presented and compared to similar previous works. Individual point sources are identified at >3.6σ significance, a threshold corresponding to a 3-5 per cent sample contamination rate. We identify 78 sources at 450 μm and 99 at 850 μm, with flux densities S450 = 13-37 mJy and S850 = 2-16 mJy. Only 62-76 per cent of 450 μm sources are 850 μm detected and 61-81 per cent of 850 μm sources are 450 μm detected. The positional uncertainties at 450 μm are small (1-2.5 arcsec) and therefore allow a precise identification of multiwavelength counterparts without reliance on detection at 24 μm or radio wavelengths; we find that only 44 per cent of 450 μm sources and 60 per cent of 850 μm sources have 24 μm or radio counterparts. 450 μm selected galaxies peak at = 1.95 ± 0.19 and 850 μm selected galaxies peak at = 2.16 ± 0.11. The two samples occupy similar parameter space in redshift and luminosity, while their median SED peak wavelengths differ by ˜20-50 μm (translating to ΔTdust = 8-12 K, where 450 μm selected galaxies are warmer). The similarities of the 450 μm and 850 μm populations, yet lack of direct overlap between them, suggests that submillimetre surveys conducted at any single far-infrared wavelength will be significantly incomplete (≳30 per cent) at censusing infrared-luminous star formation at high z.

  10. Herschel observations of a z˜ 2 stellar mass selected galaxy sample drawn from the GOODS NICMOS Survey

    NASA Astrophysics Data System (ADS)

    Hilton, M.; Conselice, C. J.; Roseboom, I. G.; Burgarella, D.; Buat, V.; Berta, S.; Béthermin, M.; Bock, J.; Chapman, S. C.; Clements, D. L.; Conley, A.; Conversi, L.; Cooray, A.; Farrah, D.; Ibar, E.; Magdis, G.; Magnelli, B.; Marsden, G.; Nordon, R.; Oliver, S. J.; Page, M. J.; Popesso, P.; Pozzi, F.; Schulz, B.; Scott, Douglas; Smith, A. J.; Symeonidis, M.; Valtchanov, I.; Viero, M.; Wang, L.; Zemcov, M.

    2012-09-01

    We present a study of the far-infrared (IR) properties of a stellar mass selected sample of 1.5 < z < 3 galaxies with log (M*/M⊙) > 9.5 drawn from the Great Observatories Origins Deep Survey (GOODS) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Survey (GNS), the deepest H-band Hubble Space Telescope survey of its type prior to the installation of Wide Field Camera 3 (WFC3). We use far-IR and submm data from the Photoconductor Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) instruments on-board Herschel, taken from the PACS Evolutionary Probe (PEP) and Herschel Multi-Tiered Extragalactic Survey (HerMES) key projects, respectively. We find a total of 22 GNS galaxies, with median log (M*/M⊙) = 10.8 and z = 2.0, associated with 250 μm sources detected with signal-to-noise ratio (SNR) > 3. We derive mean total IR luminosity log LIR(L⊙) = 12.36 ± 0.05 and corresponding star formation rate (SFR)IR + UV = (280 ± 40) M⊙ yr-1 for these objects, and find them to have mean dust temperature Tdust ≈ 35 K. We find that the SFR derived from the far-IR photometry combined with ultraviolet (UV)-based estimates of unobscured SFR for these galaxies is on average more than a factor of 2 higher than the SFR derived from extinction-corrected UV emission alone, although we note that the IR-based estimate is subject to substantial Malmquist bias. To mitigate the effect of this bias and extend our study to fainter fluxes, we perform a stacking analysis to measure the mean SFR in bins of stellar mass. We obtain detections at the 2-4σ level at SPIRE wavelengths for samples with log (M*/M⊙) > 10. In contrast to the Herschel detected GNS galaxies, we find that estimates of SFRIR + UV for the stacked samples are comparable to those derived from extinction-corrected UV emission, although the uncertainties are large. We find evidence for an increasing fraction of dust obscured star formation with stellar mass, finding SFRIR

  11. UV to IR Luminosities and Dust Attenuation Determined from ~4000 K-selected Galaxies at 1 < z < 3 in the ZFOURGE Survey

    NASA Astrophysics Data System (ADS)

    Forrest, Ben; Tran, Kim-Vy H.; Tomczak, Adam R.; Broussard, Adam; Labbé, Ivo; Papovich, Casey; Kriek, Mariska; Allen, Rebecca J.; Cowley, Michael; Dickinson, Mark; Glazebrook, Karl; van Houdt, Josha; Inami, Hanae; Kacprzak, Glenn G.; Kawinwanichakij, Lalitwadee; Kelson, Daniel; McCarthy, Patrick J.; Monson, Andrew; Morrison, Glenn; Nanayakkara, Themiya; Persson, S. Eric; Quadri, Ryan F.; Spitler, Lee R.; Straatman, Caroline; Tilvi, Vithal

    2016-02-01

    We build a set of composite galaxy spectral energy distributions (SEDs) by de-redshifting and scaling multi-wavelength photometry from galaxies in the ZFOURGE survey, covering the CDFS, COSMOS, and UDS fields. From a sample of ˜4000 Ks-band selected galaxies, we define 38 composite galaxy SEDs that yield continuous low-resolution spectra (R ˜ 45) over the rest-frame range 0.1-4 μm. Additionally, we include far infrared photometry from the Spitzer Space Telescope and the Herschel Space Observatory to characterize the infrared properties of our diverse set of composite SEDs. From these composite SEDs we analyze the rest-frame UVJ colors, as well as the ratio of IR to UV light (IRX) and the UV slope (β) in the IRX-β dust relation at 1 < z < 3. Blue star-forming composite SEDs show IRX and β values consistent with local relations; dusty star-forming galaxies have considerable scatter, as found for local IR bright sources, but on average appear bluer than expected for their IR fluxes. We measure a tight linear relation between rest-frame UVJ colors and dust attenuation for star-forming composites, providing a direct method for estimating dust content from either (U - V) or (V-J) rest-frame colors for star-forming galaxies at intermediate redshifts. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  12. JET PROPERTIES OF GeV-SELECTED RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES AND POSSIBLE CONNECTION TO THEIR DISK AND CORONA

    SciTech Connect

    Sun, Xiao-Na; Lin, Da-Bin; Liang, En-Wei; Zhang, Jin; Xue, Zi-Wei; Zhang, Shuang-Nan

    2015-01-01

    The observed spectral energy distributions of five GeV-selected narrow-line Seyfert 1 (NLS1) galaxies are fitted with a model including the radiation ingredients from the relativistic jet, the accretion disk, and the corona. We compare the properties of these GeV NLS1 galaxies with flat spectrum radio quasars (FSRQs), BL Lacertae objects (BL Lacs), and radio-quiet (RQ) Seyfert galaxies, and explore possible hints for jet-disk/corona connection. Our results show that the radiation physics and the jet properties of the GeV NLS1 galaxies resemble that of FSRQs. The luminosity variations of PMN J0948+0022 and 1H 0323+342 at the GeV band is tightly correlated with the beaming factor (δ), similar to that observed in FSRQ 3C 279. The accretion disk luminosities and the jet powers of the GeV NLS1 galaxies cover both the ranges of FSRQs and BL Lacs. With the detection of bright corona emission in 1H 0323+342, we show that the ratio of the corona luminosity (L {sub corona}) to the accretion disk luminosity (L {sub d}) is marginally within the high end of this ratio distribution for an RQ Seyfert galaxy sample, and the variation of jet luminosity may connect with L {sub corona}. However, it is still unclear whether a system with a high L {sub corona}/L {sub d} ratio prefers to power a jet.

  13. HIGHLY IONIZED PLASMA IN THE HALO OF A LUMINOUS SPIRAL GALAXY NEAR z = 0.225

    SciTech Connect

    Narayanan, Anand; Savage, Blair D.; Wakker, Bart P. E-mail: savage@astro.wisc.ed

    2010-04-01

    We present analyses of the physical conditions in the z(O{sub VI})=0.22496 and z(O{sub VI})=0.22638 multiphase absorption systems detected in the ultraviolet Hubble Space Telescope/STIS and FUSE spectra of the quasar H 1821+643 (m{sub V} = 14.2, z{sub em} = 0.297). Both absorbers are likely associated with the extended halo of a {approx}2L*{sub B} Sbc-Sc galaxy situated at a projected distance of {approx}116 h {sup -1}{sub 71} kpc from the sight line. The z = 0.22496 absorber is detected in C II, C III, C IV, O III, O VI, Si II, Si III, and H I (Ly alpha-Lytheta) at >3sigma significance. The components of Si III and Si II are narrow with implied temperatures of T {approx}< 3 x 10{sup 4} K. The low and intermediate ions in this absorber are consistent with an origin in a T {approx} 10{sup 4} K photoionized gas with [Si/H] and [C/H] of {approx}-0.6 dex. In contrast, the broader O VI absorption is likely produced in collisionally ionized plasma under nonequilibrium conditions. The z(O{sub VI})=0.22638 system has broad Ly alpha (BLA) and C III absorption offset by v = -53 km s{sup -1} from O VI. The H I and C III line widths for the BLA imply T = 1.1 x 10{sup 5} K. For non-equilibrium cooling we obtain [C/H] {approx}-1.5 dex and N(H) = 3.2 x 10{sup 18} cm{sup -2} in the BLA. The O VI, offset from the BLA with no detected H I or C III, is likely collisionally ionized at T {approx} 3 x 10{sup 5} K. From the observed multiphase properties and the proximity to a luminous galaxy, we propose that the z = 0.22496 absorber is an extragalactic analog of a highly ionized Galactic HVC, in which the O VI is produced in transition temperature plasma (T {approx} 10{sup 5} K) at the interface layers between the warm (T < 5 x 10{sup 4} K) HVC gas phase and the hot (T {approx}> 10{sup 6} K) coronal halo of the galaxy. The z = 0.22638 O VI-BLA absorber could be tracing a cooling condensing fragment in the nearby galaxy's hot gaseous halo.

  14. COLOR-MAGNITUDE RELATIONS OF ACTIVE AND NON-ACTIVE GALAXIES IN THE CHANDRA DEEP FIELDS: HIGH-REDSHIFT CONSTRAINTS AND STELLAR-MASS SELECTION EFFECTS

    SciTech Connect

    Xue, Y. Q.; Brandt, W. N.; Luo, B.; Rafferty, D. A.; Schneider, D. P.; Alexander, D. M.; Lehmer, B. D.; Bauer, F. E.; Silverman, J. D.

    2010-09-01

    -mass-matched samples where there is apparent AGN clustering in the CMD and the AGN fraction generally increases as the color becomes redder. We also find, for mass-matched samples, that the star formation rates of AGN hosts are typically a factor of {approx} 2-3 larger than those of non-AGN galaxies at z {approx} 0-1, whereas this difference diminishes at z {approx} 1-3. With mass-selection effects taken into account, we find that almost all of the results obtained in this work can reasonably be explained by two main ingredients, color-mass correlation (i.e., X-ray AGNs preferentially reside in massive galaxies that generally tend to be redder than less-massive galaxies) and passive or secular evolution of galaxies. Our results show that the presence of moderate-luminosity AGN activity does not have a significant effect on the colors of galaxies and thus tightly constrain any effects from moderate-luminosity AGN feedback upon color-magnitude properties over the {approx} 80% of cosmic time during which most of galaxy formation occurred.

  15. Spitzer 24micron Observations of Optical/Near-IR Selected Extremely Red Galaxies: Evidence for Assembly of Massive Galaxies at z approximately 1 - 2?

    NASA Technical Reports Server (NTRS)

    Yan, Lin; Choi, Philip I.; Fadda, D.; Marleau, F. R.; Soifer, B. T.; Im, M.; Armus, L.; Frayer, D. T.; Storrie-Lombardi, L. J.; Thompson, D. J.; Teplitz, H. I.; Helou, G.; Appleton, P. N.; Chapman, S.; Fan, F.; Heinrichsen, I.; Lacy, M.; Shupe, D. L; Squires, G. K.; Surace, J.; G., Wilson

    2004-01-01

    We carried out the direct measurement of the fraction of dusty sources in a sample of extremely red galaxies with (R-K(sub s)) greater than or equal to 5.3 mag and K(sub s) less than 20.2 mag, using from the Spitzer Space Telescope. Combining deep 24 micrometers, K(sub s)- and R-band data over an area of approximately 64 sq.arcmin in the ELAIS N1 field of the Spitzer First Look Survey (FLS), we find that 50 +/- 60% of our ERO sample have measurable 24 micrometer flux above the 3(sigma) flux limit of 40 microns Jy. This flux limit corresponds to a SFR of 12 solar mass/yr at z approximately 1, much mo previous long wavelength measurement. The 24fJ,m-detected EROs have 24-to2.2 and 24-to-0.7micrometr flux ratios consistent with infrared luminous, dusty sources at z approx. 1, and an order of magnitude too red to be explained by an infrared quiescent spiral or a pure old stellar population at any redshift. Some of these 24 micrometer-detected EROs could be AGN, however, the fraction among the whole ERO sample is probably small, 10-20%, as suggested by deep X-ray observations as well as optical spectroscopy. Keck optical spectroscopy of a sample of similarly selected EROs in the FLS field suggests that most of the EROs in ELAIS Nl are probably at z approx. 1.

  16. CO luminosity function from Herschel-selected galaxies and the contribution of AGN

    NASA Astrophysics Data System (ADS)

    Vallini, L.; Gruppioni, C.; Pozzi, F.; Vignali, C.; Zamorani, G.

    2016-02-01

    We derive the carbon monoxide (CO) luminosity function (LF) for different rotational transitions [i.e. (1-0), (3-2), (5-4)] starting from the Herschel LF by Gruppioni et al. and using appropriate LCO-LIR conversions for different galaxy classes. Our predicted LFs fit the data so far available at z ≈ 0 and 2. We compare our results with those obtained by semi-analytical models (SAMs): while we find a good agreement over the whole range of luminosities at z ≈ 0, at z ≈ 1 and z ≈ 2, the tension between our LFs and SAMs in the faint and bright ends increases. We finally discuss the contribution of luminous active galactic nucleus (LX > 1044 erg s- 1) to the bright end of the CO LF concluding that they are too rare to reproduce the actual CO LF at z ≈ 2.

  17. The GOODS-MUSIC sample: a multicolour catalog of near-IR selected galaxies in the GOODS-South field

    NASA Astrophysics Data System (ADS)

    Grazian, A.; Fontana, A.; de Santis, C.; Nonino, M.; Salimbeni, S.; Giallongo, E.; Cristiani, S.; Gallozzi, S.; Vanzella, E.

    2006-04-01

    Aims. We present a high quality multiwavelength (from 0.3 to 8.0 μm) catalog of the large and deep area in the GOODS Southern Field covered by the deep near-IR observations obtained with the ESO VLT. Methods. The catalog is entirely based on public data: in our analysis, we have included the F435W, F606W, F775W and F850LP ACS images, the JHKs VLT data, the Spitzer data provided by IRAC instrument (3.6, 4.5, 5.8 and 8.0 μm), and publicly available U-band data from the 2.2ESO and VLT-VIMOS. We describe in detail the procedures adopted to obtain this multiwavelength catalog. In particular, we developed a specific software for the accurate "PSF-matching" of space and ground-based images of different resolution and depth (ConvPhot), of which we analyse performances and limitations. We have included both z-selected, as well as Ks-selected objects, yielding a unique, self-consistent catalog. The largest fraction of the sample is 90% complete at z≃ 26 or Ks≃ 23.8 (AB scale). Finally, we cross-correlated our data with all the spectroscopic catalogs available to date, assigning a spectroscopic redshift to more than 1000 sources. Results. The final catalog is made up of 14 847 objects, at least 72 of which are known stars, 68 are AGNs, and 928 galaxies with spectroscopic redshift (668 galaxies with reliable redshift determination). We applied our photometric redshift code to this data set, and the comparison with the spectroscopic sample shows that the quality of the resulting photometric redshifts is excellent, with an average scatter of only 0.06. The full catalog, which we named GOODS-MUSIC (MUltiwavelength Southern Infrared Catalog), including the spectroscopic information, is made publicly available, together with the software specifically designed to this end.

  18. An XMM-Newton spectral survey of 12 μm selected galaxies - I. X-ray data

    NASA Astrophysics Data System (ADS)

    Brightman, Murray; Nandra, Kirpal

    2011-05-01

    We present an X-ray spectral analysis of 126 galaxies of the 12 μm galaxy sample. By studying this sample at X-ray wavelengths, we aim to determine the intrinsic power, continuum shape and obscuration level in these sources. We improve upon previous works by the use of superior data in the form of higher signal-to-noise ratio spectra, finer spectral resolution and a broader bandpass from XMM-Newton. We pay particular attention to Compton thick active galactic nucleus (AGN) with the help of new spectral fitting models that we have produced, which are based on Monte Carlo simulations of X-ray radiative transfer, using both a spherical and torus geometry, and taking into account Compton scattering and iron fluorescence. We use this data to show that with a torus geometry, unobscured sightlines can achieve a maximum equivalent width of the Fe Kα line of ˜150 eV, originally shown by Ghisellini et al. In order for this to be exceeded, the line of sight must be obscured with NH > 1023 cm-2, as we show for one case, NGC 3690. We also calculate flux suppression factors from the simulated data, the main conclusion from which is that for NH≥ 1025 cm-2, the X-ray flux is suppressed by a factor of at least 10 in all X-ray bands and at all redshifts, revealing the biases present against these extremely heavily obscured systems inherent in all X-ray surveys. Furthermore, we confirm previous results from Murphy & Yaqoob that show that the reflection fraction determined from slab geometries is underestimated with respect to toroidal geometries. For the 12 μm selected galaxies, we investigate the distribution of X-ray power-law indices, finding that the mean (<Γ>= 1.90+0.05-0.07 and σΓ= 0.31+0.05-0.05) is consistent with previous works, and that the distribution of Γ for obscured and unobscured sources is consistent with the source populations being the same, in general support of unification schemes. We determine a Compton thick fraction for the X-ray AGN in our sample to

  19. Spectral clustering for optical confirmation and redshift estimation of X-ray selected galaxy cluster candidates in the SDSS Stripe 82

    NASA Astrophysics Data System (ADS)

    Mahmoud, E.; Takey, A.; Shoukry, A.

    2016-07-01

    We develop a galaxy cluster finding algorithm based on spectral clustering technique to identify optical counterparts and estimate optical redshifts for X-ray selected cluster candidates. As an application, we run our algorithm on a sample of X-ray cluster candidates selected from the third XMM-Newton serendipitous source catalog (3XMM-DR5) that are located in the Stripe 82 of the Sloan Digital Sky Survey (SDSS). Our method works on galaxies described in the color-magnitude feature space. We begin by examining 45 galaxy clusters with published spectroscopic redshifts in the range of 0.1-0.8 with a median of 0.36. As a result, we are able to identify their optical counterparts and estimate their photometric redshifts, which have a typical accuracy of 0.025 and agree with the published ones. Then, we investigate another 40 X-ray cluster candidates (from the same cluster survey) with no redshift information in the literature and found that 12 candidates are considered as galaxy clusters in the redshift range from 0.29 to 0.76 with a median of 0.57. These systems are newly discovered clusters in X-rays and optical data. Among them 7 clusters have spectroscopic redshifts for at least one member galaxy.

  20. Bright Galaxies at Hubble's Detection Frontier: The redshift z~9-10 BoRG pure-parallel survey

    NASA Astrophysics Data System (ADS)

    Trenti, Michele

    2014-10-01

    Hubble/WFC3 observations transformed our view of early galaxy formation by building reliable samples of galaxies out to redshift z 8, 700 Myr after the Big Bang and hinting at a dramatic evolution in properties at yet earlier times. From z 8 to z 10 { 200Myr} the luminosity density seems to decrease by a factor ten, but bright galaxies may remain relatively common, based on the four z>9 objects detected so far with m_AB<27. To investigate this apparent conundrum, and study the formation of the most massive and luminous galaxies at 500 Myr without being affected by cosmic variance, we propose a random-pointing survey to detect 20+/-5 galaxies at z 9-10 as faint as m_AB=27.1 {5-sigma} at zero prime orbit cost. This request builds on our successful Cycle 17 & 19 Brightest of Reionizing Galaxies {BoRG} Survey, which found the largest sample of L>L* galaxies at z 8. BoRG[z8] demonstrated, by adding constraints from the Ultra Deep Field {UDF}, that the luminosity function follows a Schechter form, as at lower z, but with a steeper faint-end slope, leading to a photon production sufficient to complete reionization. BoRG[z9-10] will similarly complement the UDF and Frontier Fields datasets by imaging 550 arcmin^2 over 120 sightlines in five WFC3 bands {F350LP, F105W, F125W, F140W, F160W}. Besides twenty new catches at z>9, we will double {from 60 to 120} the number of bright z 8 galaxies within reach of spectroscopy, to tighten constraints on Ly-alpha emission and reionization obtained by our BoRG@Keck follow-up. This new public dataset will reveal the connection between massive dark matter halos and formation of first galaxies, and create a legacy of rare targets for JWST

  1. High resolution infrared astronomy satellite observations of a selected spiral galaxy

    NASA Technical Reports Server (NTRS)

    Kulkarni, S. R.

    1991-01-01

    The H I, infrared, CO, H alpha and H beta band observations of M51, the prototypical grand-design spiral galaxy, are used to study the consequences of star formation for the distribution of H I and dust. Using the new Very Large Array (VLA) map of 21 cm emission, the Owens Valley Radio Observatory CO mosaic map, and an H alpha imate, new tests were performed with the idea of Tilanus and Allen that the H I is largely a photodissociation product in star-forming regions. It is confirmed that the H I spiral arms are generally coincident with the H II region arms, and offset downstream from the CO arms. The radial distributions of total gas, H alpha and H I surface density have a simple explanation in the dissociation picture. The distributions also demonstrate how the surface density of H I might be related to the star formation efficiency in molecule-rich galaxies. The large width of the H I regions along the arms compared to that of the giant H II regions can be understood in terms of a simple calculation of the expected size of an H I region associated with a typical giant H II region. The longer lifetime of the stars producing dissociating radiation vs. those producing ionizing radiation and the relatively long molecular formation timescale will also contribute to the greater width of the H I arms if stars are continuously forming on the arms. The lack of detailed coincidence of the H I and H II regions along the inner arms has a variety of possible explanations. Two simple tests were performed to probe the origins of the IRAS emission in M51. First, it was found that the infrared excess (IFE) of M51 is 24, suggesting that a substantial fraction of the infrared emission arises from dust heated by photons which do not originate in massive star-formaing regions. Second, radial cuts through the IRAS bands show that at 12, 25, and 60 microns, the arm-interarm contrast of the IRAS emission is substantially less than that of the H alpha emission, providing further

  2. The large scale structure of the Universe revealed with high redshift emission-line galaxies: implications for future surveys

    NASA Astrophysics Data System (ADS)

    Antonino Orsi, Alvaro

    2015-08-01

    Nebular emission in galaxies trace their star-formation activity within the last 10 Myr or so. Hence, these objects are typically found in the outskirts of massive clusters, where otherwise environmental effects can effectively stop the star formation process. In this talk I discuss the nature of emission-line galaxies (ELGs) and its implications for their clustering properties. To account for the relevant physical ingredients that produce nebul