Anton M. Koekemoer

Hubble Space Telescope STIS Observations of the Kinematics of Emission-Line Nebulae in Three Compact Steep-Spectrum Radio Sources

We have obtained Hubble Space Telescope Space Telescope Imaging Spectrograph long-slit spectroscopy of the aligned emission-line nebulae in three compact steep-spectrum radio sources: 3C 67, 277.1, and 303.1. We find systematic offsets (~300–500 km s-1) of the emission-line velocities on one or both sides of the radio sources. We also see evidence for broad lines (FWHM ~ 500 km s-1) and complex emission-line profiles. In 3C 303.1 the data are consistent with multiple components and possibly split lines. The amplitude of the velocity variations is not so large as to exclude gravitationally induced motions. However, the complex kinematics, the lack of a signature of Keplerian rotation, and the association of the velocity variations with the radio lobes are consistent with the motions being driven by the expansion of the radio source. These kinematic signatures are consistent with an interaction between the expanding radio lobe and the emission-line clouds in which the clouds have been accelerated to velocities ~300–500 km s-1. Acceleration of the clouds by the bow shock is plausible given the estimated densities in the clouds and the velocities observed in the much smaller compact symmetric objects and with expansion velocities estimated from spectral aging.

3C 236: Radio Source, Interrupted?

We present new Hubble Space Telescope Space Telescope Imaging Spectrograph MAMA near-UV images and archival Wide Field Planetary Camera 2 (WFPC2) V- and R-band images that reveal the presence of four star-forming regions in an arc along the edge of the dust lane in the giant (4 Mpc) radio galaxy 3C 236. Two of the star-forming regions are relatively young, with ages of order ~107 yr, while the other two are older, with ages of order ~108–109 yr, which is comparable to the estimated age of the giant radio source. Based on dynamical and spectral aging arguments, we suggest that the fuel supply to the active galactic nucleus (AGN) was interrupted for ~107 yr and has now been restored, resulting in the formation of the inner 2 kpc–scale radio source. This timescale is similar to that of the age of the youngest of the star-forming regions. We suggest that the transport of gas in the disk is nonsteady and that this produces the multiple episodes of star formation in the disk, as well as the multiple epochs of radio source activity. If the inner radio source and the youngest star-forming region are related by the same event of gas transport, the gas must be transported from the hundreds of parsec scale to the subparsec scale on a timescale of ~107 yr, which is similar to the dynamical timescale of the gas on the hundreds of parsec scale.

Hubble Space Telescope STIS Spectroscopy of the Lyα Emission Line in the Central Dominant Galaxies in A426, A1795, and A2597: Constraints on Clouds in the Intracluster Medium*

We report on HST STIS spectra of the Lyα emission in the central dominant galaxies in three rich clusters of galaxies. We find evidence for a population of clouds in the intracluster medium. We detect 10 Lyα absorption systems toward the nucleus of NGC 1275 with columns of N(H ) ~ 1012-1014 cm-2. These columns would not have been detected in the 21 cm line but are easily detected in the Lyα line. Most of the absorption features are located in the broad wings of the emission line. The detected absorption features are most consistent with associated nuclear absorption systems. There is very little nuclear absorption at the systemic velocity in NGC 1275 [feature 8 contains N(H ) ~ 3 × 1012 cm-2]. This implies that the large columns detected in the 21 cm line toward the parsec-scale radio source avoid the line of sight to the nucleus. This gas may be located in a circumnuclear disk or torus. We detect at least one and possibly two absorption features toward the extended Lyα in A426. We do not detect Lyα absorption toward the extended Lyα emission in A1795 and A2597 with upper limits N(H ) ~ 1013 cm-2 for optically thin absorbers. Our data constrain the covering factor of any high column density gas [N(H ) > 1015 cm-2] in the ICM to be less than 25%. Our results suggest that the lack of observed intermediate-temperature gas is not explained by obscuration. In addition, the low columns of gas on ~100 kpc scales in the ICM suggest that (1) the rate at which cold gas accumulates in the ICM on these scales is very low and (2) the dense nebulae in the central ~10 kpc must have cooled or been deposited in situ.

Black holes : proceedings of the Space Telescope Science Institute Symposium, held in Baltimore, Maryland April 23-26, 2007

Participants Preface Mario Livio and Anton Koekemoer 1. Black holes, entropy, and information G. T. Horowitz 2. Gravitational waves from black-hole mergers J. G. Baker, W. D. Boggs, J. M. Centrella, B. J. Kelley, S. T. McWilliams and J. R. van Meter 3. Out-of-this-world physics: black holes at future colliders G. Landsberg 4. Black holes in globular clusters S. L. W. McMillan 5. Evolution of massive black holes M. Volonteri 6. Supermassive black holes in deep multiwavelength surveys C. M. Urry and E. Treister 7. Black-hole masses from reverberation mapping B. M. Peterson and M. C. Bentz 8. Black-hole masses from gas dynamics F. D. Macchetto 9. Evolution of supermassive black holes A. Muller and G. Hasinger 10. Black-hole masses of distant quasars M. Vestergaard 11. The accretion history of supermassive black holes K. Brand and the NDWFS Bootes Survey Teams 12. Strong field gravity and spin of black holes from broad iron lines A. C. Fabian 13. Birth of massive black-hole binaries M. Colpi, M. Dotti, L. Mayer and S. Kazantzidis 14. Dynamics around supermassive black holes A. Gualandris and D. Merritt 15. Black-hole formation and growth: simulations in general relativity S. L. Shapiro 16. Estimating the spins of stellar-mass black holes J. E. McClintock, R. Narayan and R. Shafee 17. Stellar relaxation processes near the Galactic massive black hole T. Alexander 18. Tidal disruptions of stars by supermassive black holes S. Gezari 19. Where to look for radiatively inefficient accretion flows in low-luminosity AGN M. Chiaberge 20. Making black holes visible: accretion, radiation, and jets J. H. Krolik.

Enabling new science with MAST community contributed data collections

The Mikulski Archive for Space Telescopesb (MAST), a multi-mission archive that hosts science data products for several NASA missions, has since 2003 solicited collections of processed data, termed High-Level Science Products (HLSPs), from investigators with observing and archive science programs. As of early 2018 there were nearly 130 contributed collections, and the growth rate is expected to accelerate with the start of the TESSc and JWSTd missions. While the data volume of all HLSP collections is only about 1% of the total volume hosted by MAST, they have an outsized impact on science. The aggregate downloaded volume for a given HLSP collection is typically about 40 times the collection size, and the citation rates for HLSP collections are significantly higher than that for typical observing programs. Yet hosting HLSPs presents special challenges for long-term archives. It is often problematic to obtain sufficient metadata to specify fully the data products without requiring work from potential contributors that may discourage them from sharing their collections. Historically, preparing an HLSP collection for distribution via MAST has been quite time-consuming and often required substantial interaction with the collection contributors. We are creating a more automated workflow and using new technologies for HLSP collection management to improve collection discoverability, simplify the process for the investigator, ease the burden for MAST staff, and shorten the timeframe for publishing HLSPs. This work will also help MAST staff better assess the impact of HLSP collections on science outcomes for hosted mission data.

Galaxies Unveiled: Rest-frame UV Clumps at 0.5 < z < 1.5

Studies of high redshift galaxies reveal compact sub-galactic regions of star formation, known as ‘clumps’. These ‘clumpy’ galaxies are useful for the study of galactic outskirts by enabling us to examine the radial progression of clumps over large time scales. We use the first deep high resolution NUV image from the Hubble Space Telescope covering intermediate redshifts to explore the implications this radial progression may have on galaxy evolution. From the analysis of 209 clumpy galaxies, we find that higher redshift clumps dominate the outer regions of galactic outskirts. This indicates that clumps may be migrating from the outskirts inward toward their galactic centers.

Quenching of Star-formation Activity of High-redshift Galaxies in Clusters and Field

At local, galaxy properties are well known to be clearly different in different environments. However, it is still an open question how this environment-dependent trend has been shaped. We present the results of our investigation about the evolution of star-formation properties of galaxies over a wide redshift range, from z ~ 2 to z ~ 0.5, focusing its dependence on their stellar mass and environment (Lee et al . 2015 ). In the UKIDSS/UDS region, covering ~2800 square arcmin, we estimated photometric redshifts and stellar population properties, such as stellar masses and star-formation rates, using the deep optical and near-infrared data available in this field. Then, we identified galaxy cluster candidates within the given redshift range. Through the analysis and comparison of star-formation (SF) properties of galaxies in clusters and in field, we found interesting results regarding the evolution of SF properties of galaxies: (1) regardless of redshifts, stellar mass is a key parameter controlling quenching of star formation in galaxies; (2) At z * 10 M ⊙ ) since the star formation in most of high mass galaxies are already quenched at z > 1.

Commission 47: Cosmology

The report that follows gives glimpses into the enormous amount of work in cosmology over the past three years, both in theory and in observations. It is impossible to do justice, within the space allotted, to all the exciting work and some important topics like structure formation could not be covered. Nevertheless, the contributors to different sections have done a conscientious job and I thank them all. Some of them had to step in to fill the gaps at short notice.