DWARFS GOBBLING DWARFS: A STELLAR TIDAL STREAM AROUND NGC 4449 AND HIERARCHICAL GALAXY FORMATION ON SMALL SCALES

Journal Article · Sun Apr 01 04:00:00 EDT 2012 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/748/2/L24· OSTI ID:22047933

Martinez-Delgado, David; Rix, Hans-Walter; Maccio, Andrea V ^[1]; Romanowsky, Aaron J; Arnold, Jacob A; Brodie, Jean P ^[2]; Jay Gabany, R ^[3]; Annibali, Francesca ^[4]; Fliri, Juergen ^[5]; Zibetti, Stefano ^[6]; Van der Marel, Roeland P; Aloisi, Alessandra ^[7]; Chonis, Taylor S ^[8]; Carballo-Bello, Julio A ^[9]; Gallego-Laborda, J ^[10]; Merrifield, Michael R ^[11]

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1. Max-Planck-Institut fuer Astronomy, Heidelberg (Germany)
2. UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
3. Black Bird Observatory, Mayhill, New Mexico (United States)
4. Osservatorio Astronomico di Bologna, INAF, Via Ranzani 1, I-40127 Bologna (Italy)
5. LERMA, CNRS UMR 8112, Observatoire de Paris, 61 Avenue de l'Observatoire, F-75014 Paris (France)
6. Dark Cosmology Centre, Niels Bohr Institute-University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)
7. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
8. Department of Astronomy, University of Texas at Austin, Texas (United States)
9. Instituto de Astrofisica de Canarias, Tenerife (Spain)
10. Fosca Nit Observatory, Montsec Astronomical Park, Ager (Spain)
11. School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

A candidate diffuse stellar substructure was previously reported in the halo of the nearby dwarf starburst galaxy NGC 4449 by Karachentsev et al. We map and analyze this feature using a unique combination of deep integrated-light images from the BlackBird 0.5 m telescope, and high-resolution wide-field images from the 8 m Subaru Telescope, which resolve the nebulosity into a stream of red giant branch stars, and confirm its physical association with NGC 4449. The properties of the stream imply a massive dwarf spheroidal progenitor, which after complete disruption will deposit an amount of stellar mass that is comparable to the existing stellar halo of the main galaxy. The stellar mass ratio between the two galaxies is {approx}1:50, while the indirectly measured dynamical mass ratio, when including dark matter, may be {approx}1:10-1:5. This system may thus represent a 'stealth' merger, where an infalling satellite galaxy is nearly undetectable by conventional means, yet has a substantial dynamical influence on its host galaxy. This singular discovery also suggests that satellite accretion can play a significant role in building up the stellar halos of low-mass galaxies, and possibly in triggering their starbursts.

• OSTI ID: 22047933
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 748; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
GALAXIES
GIANT STARS
IMAGES
MASS
NONLUMINOUS MATTER
RESOLUTION
SATELLITES
STAR ACCRETION
TELESCOPES
VISIBLE RADIATION