Near-Infrared Flux Limits for Sgr A* Based on NICMOS Data

Susan Stolovy, Fulvio Melia, Donald Mccarthy, Farhad Yusef-Zadeh

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Images of the central arcsec of the Galaxy at near-infrared(IR) wavelengths reveal a tight stellar cluster, however, no point source exactly coincident with the radio source Sgr A* has been clearly detected in the near-IR. "Contaminating" emission due to overlapping point spread functions (PSFs) from this stellar cluster as well as from the bright IRS16 sources 1-3″ away from Sgr A* makes it difficult to assess directly the near-IR characteristics of Sgr A*. Taking advantage of the stability of the PSF achieved by HST/NICMOS observations, we employ PSF subtraction techniques in order to investigate the true nature of the near-IR emission from Sgr A*. New limits on the maximum possible flux emanating from a point source coincident with Sgr A* are presented at 1.1, 1.45, 1.6, 1.9, and 2.2 μm based on NICMOS data taken at several epochs. These are the faintest reported near-IR flux limits for wavelengths shorter than 2.2 μm. The resulting extinction-corrected .uxes are compared to theoretical models (including both quiescent and flare models) for the spectrum of Sgr A*. We also present NICMOS narrow-band emission line images in Paα where signi.cant stellar PSF residuals have been removed to reveal new diffuse structures in the ionized gas near Sgr A* at two epochs.

Original languageEnglish (US)
Pages (from-to)419-423
Number of pages5
JournalAstronomische Nachrichten
Issue numberSUPPL.1
StatePublished - Sep 2003


  • Black hole
  • Galactic Center
  • Infrared
  • Interstellar medium
  • Sgr A*
  • Stars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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