16 research outputs found
Hosts of Type II Quasars: an HST Study
Type II quasars are luminous Active Galactic Nuclei whose centers are
obscured by large amounts of gas and dust. In this contribution we present
3-band HST images of nine type II quasars with redshifts 0.25<z<0.4 selected
from the Sloan Digital Sky Survey based on their emission line properties. The
intrinsic luminosities of these quasars are thought to be in the range
-24>M_B>-26, but optical obscuration implies that host galaxies can be studied
unencumbered by bright nuclei. Each object has been imaged in three filters
(`red', `green' and `blue') placed between the strong emission lines. The
spectacular, high quality images reveal a wealth of details about the structure
of the host galaxies and their environments. Most galaxies in the sample are
ellipticals, but strong deviations from de Vaucouleurs profiles are found,
especially in the blue band. We argue that most of these deviations are due to
the light from the nucleus scattered off interstellar material in the host
galaxy. This scattered component can make a significant contribution to the
broad-band flux and complicates the analysis of the colors of the stellar
populations in the host galaxy. This extended component can be difficult to
notice in unobscured luminous quasars and may bias the results of host galaxy
studies.Comment: 6 pages including 2 color figures; proceedings of the 'QSO host
galaxies: evolution and environment' conference, Leiden, August 200
The Formation and Evolution of Massive Stellar Clusters in IC 4662
We present a multiwavelength study of the formation of massive stellar
clusters, their emergence from cocoons of gas and dust, and their feedback on
surrounding matter. Using data that span from radio to optical wavelengths,
including Spitzer and Hubble ACS observations, we examine the population of
young star clusters in the central starburst region of the irregular Wolf-Rayet
galaxy IC 4662. We model the radio-to-IR spectral energy distributions of
embedded clusters to determine the properties of their HII regions and dust
cocoons (sizes, masses, densities, temperatures), and use near-IR and optical
data with mid-IR spectroscopy to constrain the properties of the embedded
clusters themselves (mass, age, extinction, excitation, abundance). The two
massive star-formation regions in IC 4662 are excited by stellar populations
with ages of ~ 4 million years and masses of ~ 3 x 10^5 M_sun (assuming a
Kroupa IMF). They have high excitation and sub-solar abundances, and they may
actually be comprised of several massive clusters rather than the single
monolithic massive compact objects known as Super Star Clusters (SSCs). Mid-IR
spectra reveal that these clusters have very high extinctions, A_V ~ 20-25 mag,
and that the dust in IC 4662 is well-mixed with the emitting gas, not in a
foreground screen.Comment: 7 pages, 11 figures, to appear in proceedings of the conference
"Young Massive Star Clusters: Initial Conditions and Environments ", held in
Granada, Spain, September 200
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First Results from the JWST Early Release Science Program Q3D: Powerful Quasar-driven Galactic Scale Outflow at z = 3
Quasar-driven galactic outflows are a major driver of the evolution of massive galaxies. We report observations of a powerful galactic-scale outflow in a z = 3 extremely red and intrinsically luminous (L bol ≃ 5 × 1047erg s−1) quasar SDSSJ1652 + 1728 with the Near-infrared Spectrograph on board JWST. We analyze the kinematics of rest-frame optical emission lines and identify the quasar-driven outflow extending out to ∼10 kpc from the quasar with a velocity offset of (v r = ± 500 km s−1) and high velocity dispersion (FWHM = 700-2400 km s−1). Due to JWST’s unprecedented surface brightness sensitivity in the near-infrared, we unambiguously show that the powerful high velocity outflow in an extremely red quasar encompasses a large swath of the host galaxy’s interstellar medium. Using the kinematics and dynamics of optical emission lines, we estimate the mass outflow rate—in the warm ionized phase alone—to be at least 2300 ± 1400 M ⊙ yr−1. We measure a momentum flux ratio between the outflow and the quasar accretion disk of ∼1 on a kpc scale, indicating that the outflow was likely driven in a relatively high (>1023cm−2) column density environment through radiation pressure on dust grains. We find a coupling efficiency between the bolometric luminosity of the quasar and the outflow of 0.1%, matching the theoretical prediction of the minimum coupling efficiency necessary for negative quasar feedback. The outflow has sufficient energetics to drive the observed turbulence seen in shocked regions of the quasar host galaxy, which are likely directly responsible for prolonging the time that it takes for gas to cool efficiently. © 2024. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]