Terzan 7

Globular cluster
name = Terzan 7


caption = Terzan7 by Hubble Space Telescope; 3.5′ view
credit = NASA/STScI/WikiSky
epoch = J2000
class =
constellation = Sagittarius
ra = RA|19|17|43.70cite web
title=SIMBAD Astronomical Database
work=Results for Terzan 7
url=http://simbad.u-strasbg.fr/Simbad
accessdate=2008-01-27]
dec = DEC|-34|39|27.0
dist_ly = 75.7 klycitation
title = Terzan 7 @ seds
url = http://www.seds.org/~spider/spider/MWGC/ter07.html]
dist_pc = 23.2 kpc
appmag_v = 12.0
size_v = 7′.3
mass_kg =
mass_msol =
radius_ly = 160 lyRef_label|A|a|none
v_hb = 17.76citation
last1 = Wilson
first1 = Barbara
year = 1995
date = July 2 1995
title = Obscure Globulars
url = http://www.astronomy-mall.com/Adventures.In.Deep.Space/obscure.htm]
age = 7.5 Gyrcitation
last1 = Geisler
first1 = Doug
last2 = Wallerstein
first2 = George
last3 = Smith
first3 = Verne V.
last4 = Casetti-Dinescu
first4 = Dana I.
title = Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo
year = 2007
date = September 2007
journal = The Publications of the Astronomical Society of the Pacific
volume = 119
issue = 859
page = 939-961
url = http://adsabs.harvard.edu/abs/2007PASP..119..939G]
notes = young extragalactic globular
names = Ter 7, GCl 109.1

Terzan 7 is a sparse and young globular cluster that is believed to have originated in the Sagittarius Dwarf Elliptical Galaxy (Sag DEG) and is physically associated with it. It is relatively metal rich with [Fe/H] = -0.6citation
last1 = Sbordone
first1 = L.
last2 = Bonifacio
first2 = P.
last3 = Marconi
first3 = G.
last4 = Buonanno
first4 = R.
last5 = Zaggia
first5 = S.
title = Family ties: Abundances in Terzan 7, a Sgr dSph globular cluster
year = 2005
date = July 3 2005
journal = Astronomy and Astrophysics
volume = 437
issue = 3
page = 905-910
url = http://adsabs.harvard.edu/abs/2005A%26A...437..905S] and an estimated age of 7.5 Gyr. Terzan 7 has low levels of nickel ( [Ni/Fe] =-0.2) which supports its membership in the Sag DEG system since it has a similar chemical signature.citation
last1 = Sbordone
first1 = L.
last2 = Bonifacio
first2 = P.
last3 = Marconi
first3 = G.
last4 = Buonanno
first4 = R.
year = 2004
title = Chemical abundances in Terzan 7
journal = Memorie della Societa Astronomica Italiana
volume = 75
page = 396
url = http://adsabs.harvard.edu/abs/2004MmSAI..75..396S] It has a rich population of blue stragglers that are strongly concentrated toward the center of Terzan 7.citation
last1 = Held
first1 = Enrico V.
last2 = Rosenberg
first2 = Alfred
last3 = Saviane
first3 = Ivo
last4 = Momany
first4 = Yazan
title = The Globular Cluster Terzan 7 in the Sagittarius Dwarf Spheroidal Galaxy
journal = Extragalactic Star Clusters, IAU Symposium 207
location = Pucon, Chile
date = March 12-16, 2001
year = 2001
editor1last = Geisler
editor1first = D.
editor2last = Grebel
editor2first = E.K.
editor3last = Minniti
editor3first = D.
publication-date = 2002
journal = Astronomical Society of the Pacific
publication-place = San Francisco
page = 165
url = http://adsabs.harvard.edu/abs/2002IAUS..207..165H] It has an average luminosity distribution of M_v = -5.05.citation
last1 = van den Bergh
first1 = Sidney
authorlink1 = Sidney van den Bergh
year = 2007
date = July 2007
title = The Luminosity Distribution of Globular Clusters in Dwarf Galaxies
journal = The Astronomical Journal
volume = 134
issue = 1
page = 344-345
url = http://adsabs.harvard.edu/abs/2007AJ....134..344V] It has a half-light radius (R_h) = 6.5pc.citation
last1 = van den Bergh
first1 = Sidney
authorlink1 = Sidney van den Bergh
title = Young Globular Clusters and Dwarf Spheroidals
year = 2000
date = February 2000
journal = The Astrophysical Journal
volume = 530
issue = 2
page = 777-782
url = http://adsabs.harvard.edu/abs/2000ApJ...530..777V]

History

Terzan 7 was the brighest of six globulars discovered by the Frenchcitation
title = A tour of obscure summer globular clusters
last1 = Gottlieb
first1 = Steve
title =
journal = Sky and Telescope
volume = 100
issue = 2
issn = 00376604
page = 112
year = 2000
date = August 1 2000] astronomer Agop Terzan in 1968.citation
last1 = Terzan
first1 = Agop
year = 1968
title = Six nouveaux amas stellaires (Terzan 3-8) dans la region DU centre de la Voie lactee et les constellations DU Scorpion et DU Sagittaire.
journal = C.R. Acad. Sci.
issue = Ser. B
volume = 267
page = 1245-1248
url = http://adsabs.harvard.edu/abs/1968CRASB.267.1245T]

Young globular

Nearly all globular clusters of the Milky Way's galactic halo formed at the same time (12-15 Gyr). Even the far situated NGC 2419 (~100 kpc from galactic center) has a similar age. This trend also applies to the age of globulars found in the Large Magellanic Cloud and Fornax Dwarf (~140 kpc from galactic center). However, a few globulars seem to be significantly younger than the rest; these include Palomar 1, Palomar 3, Palomar 4, Palomar 12, Palomar 14, Ruprecht 106, IC 4499, Arp 2, Eridanus, Fornax 4, and Terzan 7. In particular, the ones associated with the Sag DEG appear to have formed more recently. The data suggests that all the present outer halo globulars may have originally formed in dwarf spheroidals.

Hierarchical galaxy formation

Alternatively, a hierarchical galaxy formation model is hypothesized under which a portion, possibly large, of the Milky Way's globular clusters would have originated in the accretion of other dwarf spheroidals like Sag DEG. The best candidate for this idea is Palomar 12.citation
last1 = Briley
first1 = Michael M.
last2 = Martell
first2 = S.
last3 = Smith
first3 = G. H.
title = The Homogeneity of Light Elements in the Sagittarius Elliptical Dwarf Galaxy Globular Clusters Terzan 7 and Arp 2
year = 2007
date = December 2007
journal = American Astronomical Society, AAS Meeting #211, #58.31
url = http://adsabs.harvard.edu/abs/2007AAS...211.5831B]

Notes

1. Note_label|A|a|none75.7 kly × tan( 7′.3 / 2 ) = 160 ly. radius

References