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Papers by Kayhan Gültekin

Monthly Notices of the Royal Astronomical Society, 2015

Nature, 2012

All massive galaxies likely have supermassive black holes at their centers, and the masses of the... more All massive galaxies likely have supermassive black holes at their centers, and the masses of the black holes are known to correlate with properties of the host galaxy bulge component 1 . Several explanations have been proposed for the existence of these locallyestablished empirical relationships; they include the non-causal, statistical process of galaxy-galaxy merging 2 , direct feedback between the black hole and its host galaxy 3 , or galaxy-galaxy merging and the subsequent violent relaxation and dissipation 4 . The empirical scaling relations are thus important for distinguishing between various theoretical models of galaxy evolution 5, 6 , and they further form the basis for all black hole mass measurements at large distances. In particular, observations have shown that the mass of the black hole is typically 0.1% of the stellar bulge mass of the galaxy 7, 8 . The small galaxy NGC 4486B currently has the largest published fraction of its mass in a black hole at 11 per cent 1, 9 . Here we report observations of the stellar kinematics of NGC 1277, which is a compact, disky galaxy with a mass of 1.2 × 10 11 M . From the data, we determine that the mass of the central black hole is 1.7 × 10 10 M , or 59% its bulge mass. Five other compact galaxies have properties similar to NGC 1277 and therefore may also contain over-sized black holes. It is not yet known if these galaxies represent a tail of a distribution, or if disk-dominated galaxies fail to follow the normal black hole mass scaling relations 4, 10 .

The Astrophysical Journal, 2000

We present sub-arcsecond thermal infrared imaging of HD 98800, a young quadruple system composed ... more We present sub-arcsecond thermal infrared imaging of HD 98800, a young quadruple system composed of a pair of low-mass spectroscopic binaries separated by 0.8 ′′ (38 AU), each with a K-dwarf primary. Images at wavelengths ranging from 5 to 24.5 µm show unequivocally that the optically fainter binary, HD 98800B, is the sole source of a comparatively large infrared excess upon which a silicate emission feature is superposed. The excess is detected only at wavelengths of 7.9 µm and longer, peaks at 25 µm, and has a best-fit black-body temperature of 150 K, indicating that most of the dust lies at distances greater than the orbital separation of the spectroscopic binary. We estimate the radial extent of the dust with a disk model that approximates radiation from the spectroscopic binary as a single source of equivalent luminosity. Given the data, the most-likely values of disk properties in the ranges considered are R in = 5.0 ± 2.5 AU, ∆R = 13 ± 8 AU, λ 0 = 2 +4 −1.5 µm, γ = 0 ± 2.5, and σ total = 16 ± 3 AU 2 , where R in is the inner radius, ∆R is the radial extent of the disk, λ 0 is the effective grain size, γ is the radial power-law exponent of the optical depth, τ , and σ total is the total cross-section of the grains. The range of implied disk masses is 0.001-0.1 times that of the moon. These results show that, for a wide range of possible disk properties, a circumbinary disk is far more likely than a narrow ring.

Monthly Notices of the Royal Astronomical Society, 2015

Nature, 2012

All massive galaxies likely have supermassive black holes at their centers, and the masses of the... more All massive galaxies likely have supermassive black holes at their centers, and the masses of the black holes are known to correlate with properties of the host galaxy bulge component 1 . Several explanations have been proposed for the existence of these locallyestablished empirical relationships; they include the non-causal, statistical process of galaxy-galaxy merging 2 , direct feedback between the black hole and its host galaxy 3 , or galaxy-galaxy merging and the subsequent violent relaxation and dissipation 4 . The empirical scaling relations are thus important for distinguishing between various theoretical models of galaxy evolution 5, 6 , and they further form the basis for all black hole mass measurements at large distances. In particular, observations have shown that the mass of the black hole is typically 0.1% of the stellar bulge mass of the galaxy 7, 8 . The small galaxy NGC 4486B currently has the largest published fraction of its mass in a black hole at 11 per cent 1, 9 . Here we report observations of the stellar kinematics of NGC 1277, which is a compact, disky galaxy with a mass of 1.2 × 10 11 M . From the data, we determine that the mass of the central black hole is 1.7 × 10 10 M , or 59% its bulge mass. Five other compact galaxies have properties similar to NGC 1277 and therefore may also contain over-sized black holes. It is not yet known if these galaxies represent a tail of a distribution, or if disk-dominated galaxies fail to follow the normal black hole mass scaling relations 4, 10 .

The Astrophysical Journal, 2000

We present sub-arcsecond thermal infrared imaging of HD 98800, a young quadruple system composed ... more We present sub-arcsecond thermal infrared imaging of HD 98800, a young quadruple system composed of a pair of low-mass spectroscopic binaries separated by 0.8 ′′ (38 AU), each with a K-dwarf primary. Images at wavelengths ranging from 5 to 24.5 µm show unequivocally that the optically fainter binary, HD 98800B, is the sole source of a comparatively large infrared excess upon which a silicate emission feature is superposed. The excess is detected only at wavelengths of 7.9 µm and longer, peaks at 25 µm, and has a best-fit black-body temperature of 150 K, indicating that most of the dust lies at distances greater than the orbital separation of the spectroscopic binary. We estimate the radial extent of the dust with a disk model that approximates radiation from the spectroscopic binary as a single source of equivalent luminosity. Given the data, the most-likely values of disk properties in the ranges considered are R in = 5.0 ± 2.5 AU, ∆R = 13 ± 8 AU, λ 0 = 2 +4 −1.5 µm, γ = 0 ± 2.5, and σ total = 16 ± 3 AU 2 , where R in is the inner radius, ∆R is the radial extent of the disk, λ 0 is the effective grain size, γ is the radial power-law exponent of the optical depth, τ , and σ total is the total cross-section of the grains. The range of implied disk masses is 0.001-0.1 times that of the moon. These results show that, for a wide range of possible disk properties, a circumbinary disk is far more likely than a narrow ring.