NGC 1700

NGC 1700 is an elliptical galaxy that formed after the merger of at least two galaxies. The galaxy has boxy isophotes and has two broad tidal tails or plumes extending towards the north-west and south-east of the galaxy for about 165 arcseconds, which corresponds to {{convert|41,000|pc|ly}} at the distance of the galaxy. A faint shell system is visible in the central 25 arcseconds of the galaxy.{{cite journal |last1=Forbes |first1=D. A. |last2=Thomson |first2=R. C. |title=Shells and isophotal distortions in elliptical galaxies |journal=Monthly Notices of the Royal Astronomical Society |date=15 February 1992 |volume=254 |issue=4 |pages=723–728 |doi=10.1093/mnras/254.4.723|doi-access=free }} Chaotic dust clouds have been observed within two arcseconds from the centre of the galaxy. They lie at an angle of 45 degrees with respect to the major axis of the galaxy.{{cite journal |last1=Whitmore |first1=Bradley C. |last2=Miller |first2=Bryan W. |last3=Schweizer |first3=Francois |last4=Fall |first4=S. Michael |title=Hubble Space Telescope Observations of Two Dynamically Young Elliptical Galaxies |journal=The Astronomical Journal |date=November 1997 |volume=114 |pages=1797 |doi=10.1086/118607|bibcode=1997AJ....114.1797W }} The presence of two symmetrical tails indicates that the galaxy was formed from two spiral galaxies, or possibly a spiral galaxy and an elliptical galaxy. Based on the morphology of the tails, Brown estimated in 2000 the merger took place 3.2 ± 1.5 billion years ago,{{cite journal |last1=Brown |first1=Richard J. N. |last2=Forbes |first2=Duncan A. |last3=Kissler-Patig |first3=Markus |last4=Brodie |first4=Jean P. |title=Imaging of the protoelliptical NGC 1700 and its globular cluster system |journal=Monthly Notices of the Royal Astronomical Society |date=September 2000 |volume=317 |issue=2 |pages=406–420 |doi=10.1046/j.1365-8711.2000.03595.x|doi-access=free |arxiv=astro-ph/0004019 |bibcode=2000MNRAS.317..406B }} while Schweizer and Seitzer estimated in 1992 it took place 6 billion years ago.{{cite journal |last1=Schweizer |first1=Francois |last2=Seitzer |first2=Patrick |title=Correlations between UBV colors and fine structure in E and S0 galaxies - A first attempt at dating ancient merger events |journal=The Astronomical Journal |date=September 1992 |volume=104 |pages=1039 |doi=10.1086/116296}}

File:NGC 1700- Giant X-Ray Disk Sheds Light On Galactic Merger (2002-n1700 - n1700 xray).jpg

Observations of the galaxy by the Chandra X-ray Observatory revealed the presence of an extended disk of hot gas with a diameter of 90,000 light years glowing in X-rays. Upon discovery, it was the largest disk of hot gas known.{{cite web |title=NGC 1700: Giant X-Ray Disk Sheds Light On Galactic Merger |url=https://chandra.cfa.harvard.edu/photo/2002/n1700/ |date= 18 December 2002 |website=chandra.cfa.harvard.edu |access-date=10 February 2025}} The disk appears flattened at the outer parts of the galaxy, indicating it is rotating. The temperature of the gas is estimated to be 0.47 ± 0.03 keV. The hot gas disk was accreted during the merger and given the gas cooling rate, the merger took place 3 billion years ago. The rotation implies it continues to carry its initial momentum.{{cite journal |last1=Statler |first1=Thomas S. |last2=McNamara |first2=Brian R. |title=A 15 Kiloparsec X-Ray Disk in the Elliptical Galaxy NGC 1700 |journal=The Astrophysical Journal |date=20 December 2002 |volume=581 |issue=2 |pages=1032–1038 |doi=10.1086/344362|arxiv=astro-ph/0208379 |bibcode=2002ApJ...581.1032S }}

The Hubble Space Telescope found 146 globular clusters in NGC 1700. The globular clusters with an apparent magnitude brighter than 24.5 show a twin peak distribution in color, at V−I=0.85 ± 0.05 and V−I=1.15 ± 0.05, which were also present in images taken by the Keck Observatory, where 312 globular clusters were detected. The blue population has similar color to the globular clusters in Milky Way and is representative of old metal-poor clusters, while the red population has higher metallicity, higher than the solar one, and is younger, with an estimated age of 2.5 to 5 billion years by Brown et al, while Trancho et al estimated an age of 1.7 ± 0.8 billion years for the younger clusters.{{cite journal |last1=Trancho |first1=Gelys |last2=Miller |first2=Bryan W. |last3=Schweizer |first3=François |last4=Burdett |first4=Daniel P. |last5=Palamara |first5=David |title=Intermediate-Age Globular Clusters in Four Galaxy Merger Remnants |journal=The Astrophysical Journal |date=14 July 2014 |volume=790 |issue=2 |pages=122 |doi=10.1088/0004-637X/790/2/122|arxiv=1408.0750 |bibcode=2014ApJ...790..122T }}

The stellar population in the core of the galaxy is younger than the rest of the galaxy, having an estimated age of about 6 billion years. The stars in the core are rotating at the opposite direction as the rest of the galaxy, and the core is characterised as kinematically decoupled. It is possible this characteristic is the result of the accretion of a smaller counter-rotating companion galaxy in an event separate from that which created the tidal tails.{{cite journal |last1=Kleineberg |first1=K. |last2=Sánchez-Blázquez |first2=P. |last3=Vazdekis |first3=A. |title=Evidence of a Distinct Stellar Population in the Counterrotating Core of NGC 1700 |journal=The Astrophysical Journal |date=10 May 2011 |volume=732 |issue=2 |pages=L33 |doi=10.1088/2041-8205/732/2/L33|arxiv=1103.3797 |bibcode=2011ApJ...732L..33K }} Statler et al estimated that the merger which resulted in the kinematically decoupled core took place 2 to 4 billion years ago.{{cite journal |last1=Statler |first1=Thomas S. |last2=Smecker-Hane |first2=Tammy |last3=Cecil |first3=Gerald N. |title=The Post-Merger Elliptical NGC 1700: Stellar Kinematic Fields to Four Effective Radii |journal=The Astronomical Journal |date=April 1996 |volume=111 |pages=1512 |doi=10.1086/117893|arxiv=astro-ph/9512076 |bibcode=1996AJ....111.1512S }} In the centre of the galaxy lies a supermassive black hole whose mass is estimated to be about 425 million {{solar mass}} based on the bulge mass-black hole mass relation.{{cite journal |last1=Chen |first1=Xian |last2=Liu |first2=F. K. |last3=Magorrian |first3=John |title=Tidal Disruption of Stellar Objects by Hard Supermassive Black Hole Binaries |journal=The Astrophysical Journal |date=20 March 2008 |volume=676 |issue=1 |pages=54–69 |doi=10.1086/527412|arxiv=0712.0246 |bibcode=2008ApJ...676...54C }}

NGC 1700 belongs to a galaxy group known as LGG 123. Other members of the group include the galaxies NGC 1729, NGC 1741, IC 2102, and IC 399.{{cite journal |last1=Garcia |first1=A. M. |title=General study of group membership. II. Determination of nearby groups. |journal=Astronomy and Astrophysics Supplement Series |date=1 July 1993 |volume=100 |pages=47–90 |url=https://cdsarc.cds.unistra.fr/ftp/J/A+AS/100/47/table2.dat |bibcode= 1993A&AS..100...47G |issn=0365-0138|bibcode-access=free}} NGC 1699 lies at a projected distance of 6.5 arcminutes.{{cite journal |last1=de Vaucouleurs |first1=G. |last2=de Vaucouleurs |first2=A. |last3=Corwin |first3=J. R. |title=Second reference catalogue of bright galaxies |journal=Second Reference Catalogue of Bright Galaxies |date=1 January 1976 |volume=1976 |pages=0 |bibcode=1976RC2...C......0D |url=https://ui.adsabs.harvard.edu/abs/1976RC2...C......0D/abstract}}

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• [http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NGC%201700 NGC 1700 on SIMBAD]

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{{Eridanus (constellation)}}

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Category:Elliptical galaxies

Category:Shell galaxies

Category:Galaxy mergers

Category:Eridanus (constellation)

1700

16386

Category:Discoveries by William Herschel

Category:Astronomical objects discovered in 1785