Skip to main content
Home

Navigation Menu

  • Back
  • About
    • Back
    • About

      Contact Us

      Business Address
      5241 Broad Branch Rd. NW

      Washington , DC 20015
      United States place Map
      Call Us (202) 387-640
    • Who We Are
      • Back
      • Leadership
      • Board & Advisory Committee
      • Financial Stewardship
      • Awards & Accolades
      • History
    • Connect with Us
      • Back
      • Outreach & Education
      • Newsletter
      • Yearbook
    • Working at Carnegie
      • Back
      • Applications Open: Postdoctoral Fellowships

    Contact Us

    Business Address
    5241 Broad Branch Rd. NW

    Washington , DC 20015
    United States place Map
    Call Us (202) 387-6400
  • Research
    • Back
    • Research Areas & Topics
    • Research Areas & Topics
      • Back
      • Research Areas
      • From genomes to ecosystems and from planets to the cosmos, Carnegie Science is an incubator for cutting-edge, interdisciplinary research.
      • Astronomy & Astrophysics
        • Back
        • Astronomy & Astrophysics
        • Astrophysical Theory
        • Cosmology
        • Distant Galaxies
        • Milky Way & Stellar Evolution
        • Planet Formation & Evolution
        • Solar System & Exoplanets
        • Telescope Instrumentation
        • Transient & Compact Objects
      • Earth Science
        • Back
        • Earth Science
        • Experimental Petrology
        • Geochemistry
        • Geophysics & Geodynamics
        • Mineralogy & Mineral Physics
      • Ecology
        • Back
        • Ecology
        • Atmospheric Science & Energy
        • Adaptation to Climate Change
        • Water Quality & Scarcity
      • Genetics & Developmental Biology
        • Back
        • Genetics & Developmental Biology
        • Adaptation to Climate Change
        • Developmental Biology & Human Health
        • Genomics
        • Model Organism Development
        • Nested Ecosystems
        • Symbiosis
      • Matter at Extreme States
        • Back
        • Matter at Extreme States
        • Extreme Environments
        • Extreme Materials
        • Mineralogy & Mineral Physics
      • Planetary Science
        • Back
        • Planetary Science
        • Astrobiology
        • Cosmochemistry
        • Mineralogy & Mineral Physics
        • Planet Formation & Evolution
        • Solar System & Exoplanets
      • Plant Science
        • Back
        • Plant Science
        • Adaptation to Climate Change
        • Nested Ecosystems
        • Photosynthesis
        • Symbiosis
    • Divisions
      • Back
      • Divisions
      • Biosphere Sciences & Engineering
        • Back
        • Biosphere Sciences & Engineering
        • About

          Contact Us

          Business Address
          5241 Broad Branch Rd. NW

          Washington , DC 20015
          United States place Map
          Call Us (202) 387-640
        • Research
        • Culture
      • Earth & Planets Laboratory
        • Back
        • Earth & Planets Laboratory
        • About

          Contact Us

          Business Address
          5241 Broad Branch Rd. NW

          Washington , DC 20015
          United States place Map
          Call Us (202) 387-640
        • Research
        • Culture
        • Campus
      • Observatories
        • Back
        • Observatories
        • About

          Contact Us

          Business Address
          5241 Broad Branch Rd. NW

          Washington , DC 20015
          United States place Map
          Call Us (202) 387-640
        • Research
        • Culture
        • Campus
    • Instrumentation
      • Back
      • Instrumentation
      • Our Telescopes
        • Back
        • Our Telescopes
        • Magellan Telescopes
        • Swope Telescope
        • du Pont Telescope
      • Observatories Machine Shop
      • EPL Research Facilities
      • EPL Machine Shop
      • Mass Spectrometry Facility
      • Advanced Imaging Facility
  • People
    • Back
    • People
      Observatory Staff

      Featured Staff Member

      Staff Member

      Staff Member

      Professional Title

      Learn More
      Observatory Staff

      Search For

    • Search All People
      • Back
      • Staff Scientists
      • Leadership
      • Biosphere Science & Engineering People
      • Earth & Planets Laboratory People
      • Observatories People
    Observatory Staff
    Dr. Margaret McFall-Ngai
    Senior Staff Scientist

    Featured Staff Member

    Dr. Margaret McFall-Ngai

    Senior Staff Scientist

    Learn More
    Observatory Staff
    Dr. Margaret McFall-Ngai
    Senior Staff Scientist

    Microbiome specialist Margaret McFall-Ngai’s research focuses on the beneficial relationships between animals and bacteria, including the establishment and maintenance of symbiosis, the evolution of these interactions, and their impact on the animal’s health.

    Search For

    Search All Staff
  • Events
    • Back
    • Events
    • Search All Events
      • Back
      • Public Events
      • Biosphere Science & Engineering Events
      • Earth & Planets Laboratory Events
      • Observatories Events

    Upcoming Events

    Events

    Events

    2005_DTM_NASAEnceladusTigerStripes
    Public Program

    Neighborhood Lecture Series Program With Dr. Caleb Scharf

    Dr. Caleb Scharf

    November 6

    6:30pm EST

    Two people look at each other
    Public Program

    Face Value: How the Brain Shapes Human Connection

    Nancy Kanwisher

    October 29

    6:30pm EDT

    Open House Background
    Public Program

    Earth & Planets Laboratory Open House

    Earth & Planets Laboratory

    October 25

    1:00pm EDT

  • News
    • Back
    • News
    • Search All News
      • Back
      • Biosphere Science & Engineering News
      • Earth & Planets Laboratory News
      • Observatories News
      • Carnegie Science News
    News

    Recent News

    News

    News and updates from across Carnegie Science.
    Read all News
    Images from the night of 2025 SC79’s discovery showing its motion relative to background stars. Photographs courtesy of Scott S. Sheppard.
    Breaking News
    October 16, 2025

    Fast-moving asteroid found in Sun’s glare

    Stars in space
    Breaking News
    September 30, 2025

    Vote for Carnegie Science’s 2025 Holiday Card

    Artist's conception of moon-forming environment. Credit: NASA, ESA, CSA, STScI, Gabriele Cugno (University of Zürich, NCCR PlanetS), Sierra Grant (Carnegie Institution for Science), Joseph Olmsted (STScI), Leah Hustak (STScI)
    Breaking News
    September 29, 2025

    Astronomers get first-ever peek into a gas giant’s moon-forming environment

  • Donate
    • Back
    • Donate
      - ,

    • Make a Donation
      • Back
      • Support Scientific Research
      • The Impact of Your Gift
      • Carnegie Champions
      • Planned Giving
    Jo Ann Eder

    I feel passionately about the power of nonprofits to bolster healthy communities.

    - Jo Ann Eder , Astronomer and Alumna

    Header Text

    Postdoctoral alumna Jo Ann Eder is committed to making the world a better place by supporting organizations, like Carnegie, that create and foster STEM learning opportunities for all. 

    Learn more arrow_forward
  • Home

Abstract
We determine the quantitative morphology and star formation properties of galaxies in six nearby X-ray-detected, poor groups using multiobject spectroscopy and wide-field R imaging. The mean recessional velocities of the galaxy groups range from 2843 to 7558 km s(-1). Each group has 15-38 confirmed members ranging in luminosity from dwarfs to giants (-13.7 greater than or equal to M-R - 5 log h greater than or equal to -21.9). We measure structural parameters for each galaxy by fitting a PSF-convolved, two-component model to their surface brightness profiles. To compare the samples directly, we fade, smooth, and rebin each galaxy image so that we effectively observe each galaxy at the same redshift (9000 km s(-1)) and physical resolution (0.87 h(-1) kpc). The structural parameters are combined with [O II] measurements to test for correlations between morphological characteristics and current star formation in these galaxies. We compare results for the groups to a sample of field galaxies. We find that : (1) Galaxies spanning a wide range in morphological type and luminosity are fit well by a de Vaucouleurs bulge with exponential disk profile. (2) Morphologically classifying these nearby group galaxies by their bulge fraction (B/T) is fairly robust on average, even when their redshift has increased by up to a factor of 4 and the effective resolution of the images is degraded by up to a factor of 5. (3) The fraction of bulge-dominated systems in these groups is higher than in the field (similar to 50% versus similar to 20%). (4) The fraction of bulge-dominated systems in groups decreases with increasing radius, similar to the morphology-radius (similar to density) relation observed in galaxy clusters. (5) Current star formation in group galaxies is correlated with significant morphological asymmetry for disk-dominated systems (B/T <0.4). (6) The group galaxies that are most disk dominated (B/T <0.2) are less star forming and asymmetric on average than their counterparts in the field.
View Full Publication open_in_new
Abstract
We determine the quantitative morphology and star formation properties of galaxies in six nearby X-ray-detected, poor groups using multiobject spectroscopy and wide-field R imaging. The mean recessional velocities of the galaxy groups range from 2843 to 7558 km s(-1). Each group has 15-38 confirmed members ranging in luminosity from dwarfs to giants (-13.7 greater than or equal to M-R - 5 log h greater than or equal to -21.9). We measure structural parameters for each galaxy by fitting a PSF-convolved, two-component model to their surface brightness profiles. To compare the samples directly, we fade, smooth, and rebin each galaxy image so that we effectively observe each galaxy at the same redshift (9000 km s(-1)) and physical resolution (0.87 h(-1) kpc). The structural parameters are combined with [O II] measurements to test for correlations between morphological characteristics and current star formation in these galaxies. We compare results for the groups to a sample of field galaxies. We find that : (1) Galaxies spanning a wide range in morphological type and luminosity are fit well by a de Vaucouleurs bulge with exponential disk profile. (2) Morphologically classifying these nearby group galaxies by their bulge fraction (B/T) is fairly robust on average, even when their redshift has increased by up to a factor of 4 and the effective resolution of the images is degraded by up to a factor of 5. (3) The fraction of bulge-dominated systems in these groups is higher than in the field (similar to 50% versus similar to 20%). (4) The fraction of bulge-dominated systems in groups decreases with increasing radius, similar to the morphology-radius (similar to density) relation observed in galaxy clusters. (5) Current star formation in group galaxies is correlated with significant morphological asymmetry for disk-dominated systems (B/T <0.4). (6) The group galaxies that are most disk dominated (B/T <0.2) are less star forming and asymmetric on average than their counterparts in the field.
View Full Publication open_in_new
Abstract
Based on observations of the Seyfert nucleus in NGC 1068 with ASCA, RXTE, and BeppoSAX, we report the discovery of a are (increase in flux by a factor of similar to1.6) in the 6.7 keV Fe K line component between observations obtained 4 months apart, with no significant change in the other (6.21, 6.4, and 6.97 keV) Fe Kalpha line components. During this time, the continuum flux decreased by similar to20%. The RXTE spectrum requires an Fe K absorption edge near 8.6 keV (Fe XXIII-XXV). The spectral data indicate that the 2-10 keV continuum emission is dominated (similar to2/3 of the luminosity) by reflection from a previously unidentified region of warm, ionized gas located less than or similar to0.2 pc from the AGN. The remaining similar to1/3 of the observed X-ray emission is reflected from optically thick, neutral gas. The coronal gas in the inner narrow-line region and/or the cold gas at the inner surface of the obscuring "torus" are possible cold reflectors. The inferred properties of the warm reflector are size (diameter) less than or similar to0.2 pc, gas density ngreater than or similar to10(5.5) cm(-3), ionization parameter xiapproximate to10(3.5) ergs cm s(-1), and covering fraction 0.003(L-0/10(43.5) ergs s(-1))(-1) <(&UOmega;/4π)<0.024(L-0/10(43.5) ergs s(-1))(-1), where L-0 is the intrinsic 2-10 keV X-ray luminosity of the AGN. We suggest that the warm reflector gas is the source of the ( variable) 6.7 keV Fe line emission and the 6.97 keV Fe line emission. The 6.7 keV line are is assumed to be due to an increase in the emissivity of the warm reflector gas from a decrease (by 20%-30%) in L-0. The properties of the warm reflector are most consistent with an intrinsically X-ray weak AGN with L(0)approximate to10(43.0) ergs s(-1). The optical and UV emission that scatters from the warm reflector into our line of sight is required to suffer strong extinction, which can be reconciled if the line of sight skims the outer surface of the torus. Thermal brems-strahlung radio emission from the warm reflector may be detectable in Very Long Baseline Array radio maps of the NGC 1068 nucleus.
View Full Publication open_in_new
Abstract
Based on observations of the Seyfert nucleus in NGC 1068 with ASCA, RXTE, and BeppoSAX, we report the discovery of a are (increase in flux by a factor of similar to1.6) in the 6.7 keV Fe K line component between observations obtained 4 months apart, with no significant change in the other (6.21, 6.4, and 6.97 keV) Fe Kalpha line components. During this time, the continuum flux decreased by similar to20%. The RXTE spectrum requires an Fe K absorption edge near 8.6 keV (Fe XXIII-XXV). The spectral data indicate that the 2-10 keV continuum emission is dominated (similar to2/3 of the luminosity) by reflection from a previously unidentified region of warm, ionized gas located less than or similar to0.2 pc from the AGN. The remaining similar to1/3 of the observed X-ray emission is reflected from optically thick, neutral gas. The coronal gas in the inner narrow-line region and/or the cold gas at the inner surface of the obscuring "torus" are possible cold reflectors. The inferred properties of the warm reflector are size (diameter) less than or similar to0.2 pc, gas density ngreater than or similar to10(5.5) cm(-3), ionization parameter xiapproximate to10(3.5) ergs cm s(-1), and covering fraction 0.003(L-0/10(43.5) ergs s(-1))(-1) <(&UOmega;/4π)<0.024(L-0/10(43.5) ergs s(-1))(-1), where L-0 is the intrinsic 2-10 keV X-ray luminosity of the AGN. We suggest that the warm reflector gas is the source of the ( variable) 6.7 keV Fe line emission and the 6.97 keV Fe line emission. The 6.7 keV line are is assumed to be due to an increase in the emissivity of the warm reflector gas from a decrease (by 20%-30%) in L-0. The properties of the warm reflector are most consistent with an intrinsically X-ray weak AGN with L(0)approximate to10(43.0) ergs s(-1). The optical and UV emission that scatters from the warm reflector into our line of sight is required to suffer strong extinction, which can be reconciled if the line of sight skims the outer surface of the torus. Thermal brems-strahlung radio emission from the warm reflector may be detectable in Very Long Baseline Array radio maps of the NGC 1068 nucleus.
View Full Publication open_in_new
Abstract
Based on observations of the Seyfert nucleus in NGC 1068 with ASCA, RXTE, and BeppoSAX, we report the discovery of a are (increase in flux by a factor of similar to1.6) in the 6.7 keV Fe K line component between observations obtained 4 months apart, with no significant change in the other (6.21, 6.4, and 6.97 keV) Fe Kalpha line components. During this time, the continuum flux decreased by similar to20%. The RXTE spectrum requires an Fe K absorption edge near 8.6 keV (Fe XXIII-XXV). The spectral data indicate that the 2-10 keV continuum emission is dominated (similar to2/3 of the luminosity) by reflection from a previously unidentified region of warm, ionized gas located less than or similar to0.2 pc from the AGN. The remaining similar to1/3 of the observed X-ray emission is reflected from optically thick, neutral gas. The coronal gas in the inner narrow-line region and/or the cold gas at the inner surface of the obscuring "torus" are possible cold reflectors. The inferred properties of the warm reflector are size (diameter) less than or similar to0.2 pc, gas density ngreater than or similar to10(5.5) cm(-3), ionization parameter xiapproximate to10(3.5) ergs cm s(-1), and covering fraction 0.003(L-0/10(43.5) ergs s(-1))(-1) <(&UOmega;/4π)<0.024(L-0/10(43.5) ergs s(-1))(-1), where L-0 is the intrinsic 2-10 keV X-ray luminosity of the AGN. We suggest that the warm reflector gas is the source of the ( variable) 6.7 keV Fe line emission and the 6.97 keV Fe line emission. The 6.7 keV line are is assumed to be due to an increase in the emissivity of the warm reflector gas from a decrease (by 20%-30%) in L-0. The properties of the warm reflector are most consistent with an intrinsically X-ray weak AGN with L(0)approximate to10(43.0) ergs s(-1). The optical and UV emission that scatters from the warm reflector into our line of sight is required to suffer strong extinction, which can be reconciled if the line of sight skims the outer surface of the torus. Thermal brems-strahlung radio emission from the warm reflector may be detectable in Very Long Baseline Array radio maps of the NGC 1068 nucleus.
View Full Publication open_in_new
Abstract
A search was conducted for a hot intragroup medium in 109 low-redshift galaxy groups observed with the ROSAT PSPC. Evidence for diffuse, extended X-ray emission is found in at least 61 groups. Approximately one-third of these detections have not been previously reported in the literature. Most of the groups are detected out to less than half of the virial radius with ROSAT. Although some spiral-rich groups do contain an intragroup medium, diffuse emission is restricted to groups that contain at least one early-type galaxy.
View Full Publication open_in_new
Abstract
A search was conducted for a hot intragroup medium in 109 low-redshift galaxy groups observed with the ROSAT PSPC. Evidence for diffuse, extended X-ray emission is found in at least 61 groups. Approximately one-third of these detections have not been previously reported in the literature. Most of the groups are detected out to less than half of the virial radius with ROSAT. Although some spiral-rich groups do contain an intragroup medium, diffuse emission is restricted to groups that contain at least one early-type galaxy.
View Full Publication open_in_new
Abstract
A search was conducted for a hot intragroup medium in 109 low-redshift galaxy groups observed with the ROSAT PSPC. Evidence for diffuse, extended X-ray emission is found in at least 61 groups. Approximately one-third of these detections have not been previously reported in the literature. Most of the groups are detected out to less than half of the virial radius with ROSAT. Although some spiral-rich groups do contain an intragroup medium, diffuse emission is restricted to groups that contain at least one early-type galaxy.
View Full Publication open_in_new
Abstract
A search was conducted for a hot intragroup medium in 109 low-redshift galaxy groups observed with the ROSAT PSPC. Evidence for diffuse, extended X-ray emission is found in at least 61 groups. Approximately one-third of these detections have not been previously reported in the literature. Most of the groups are detected out to less than half of the virial radius with ROSAT. Although some spiral-rich groups do contain an intragroup medium, diffuse emission is restricted to groups that contain at least one early-type galaxy.
View Full Publication open_in_new
Abstract
The detailed morphology of the interstellar medium (ISM) in the central kiloparsec of galaxies is controlled by pressure and gravitation. The combination of these forces shapes both circumnuclear star formation and the growth of the central, supermassive black hole. We present visible and near-infrared Hubble Space Telescope images and color maps of 123 nearby galaxies that show the distribution of the cold ISM, as traced by dust, with excellent spatial resolution. These observations reveal that nuclear dust spirals are found in the majority of active and inactive galaxies and they possess a wide range in coherence, symmetry, and pitch angle. We have used this large sample to develop a classification system for circumnuclear dust structures. In spite of the heterogeneous nature of the complete sample, we only find symmetric, two-arm nuclear dust spirals in galaxies with large-scale bars, and these dust lanes clearly connect to dust lanes along the leading edges of the large-scale bars. Not all dust lanes along large-scale bars form two-arm spirals, however, and several instead end in nuclear rings. We find that tightly wound, or low pitch angle, nuclear dust spirals are more common in unbarred galaxies than barred galaxies. Finally, the extended narrow-line region in several of the active galaxies is well resolved. The connection between the ionized gas and circumnuclear dust lanes in four of these galaxies provides additional evidence that a significant fraction of their extended narrow-line region is ambient gas photoionized in situ by the active nucleus. In a future paper we will use our classification system for circumnuclear dust to identify differences between active and inactive galaxies, as well as barred and unbarred galaxies, in well-matched subsamples of these data.
View Full Publication open_in_new

Pagination

  • Previous page chevron_left
  • …
  • Page 395
  • Page 396
  • Page 397
  • Page 398
  • Current page 399
  • Page 400
  • Page 401
  • Page 402
  • Page 403
  • …
  • Next page chevron_right
Subscribe to

Get the latest

Subscribe to our newsletters.

Privacy Policy
Home
  • Instagram instagram
  • Twitter twitter
  • Youtube youtube
  • Facebook facebook

Science

  • Biosphere Sciences & Engineering
  • Earth & Planets Laboratory
  • Observatories
  • Research Areas

Legal

  • Financial Statements
  • Conflict of Interest Policy
  • Privacy Policy

Careers

  • Working at Carnegie
  • Scientific and Technical Jobs
  • Administrative & Support Jobs
  • Postdoctoral Program
  • Carnegie Connect (For Employees)

Contact Us

  • Contact Administration
  • Media Contacts

Business Address

5241 Broad Branch Rd. NW

Washington, DC 20015

place Map

© Copyright Carnegie Science 2025