ﻻ يوجد ملخص باللغة العربية
We conducted systematic observations of the HI Br-alpha line (4.05 micron) and the polycyclic aromatic hydrocarbon (PAH) feature (3.3 micron) in 50 nearby (z<0.3) ultraluminous infrared galaxies (ULIRGs) with AKARI. The Br-alpha line is predicted to be the brightest among the HI lines under high dust-extinction conditions (A_V>15 mag). The Br-alpha line traces ionizing photons from OB stars and so is used as an indicator of star formation on the assumption of the initial mass function. We detected the Br-alpha line in 33 ULIRGs. The luminosity of the line (L_BrA) correlates well with that of the 3.3 micron PAH emission (L_3.3). Thus we utilize L_3.3 as an indicator of star formation in fainter objects where the Br-alpha line is undetected. The mean L_BrA/L_IR ratio in LINERs/Seyferts is significantly lower than that in HII galaxies. This difference is reconfirmed with the L_3.3/L_IR ratio in the larger sample (46 galaxies). Using the ratios, we estimate that the contribution of starburst in LINERs/Seyferts is ~67%, and active galactic nuclei contribute to the remaining ~33%. However, comparing the number of ionizing photons, Q_BrA, derived from L_BrA with that, Q_IR, expected from star formation rate required to explain L_IR, we find that the mean Q_BrA/Q_IR ratio is only 55.5+/-7.5% even in HII galaxies which are thought to be energized by pure starburst. This deficit of ionizing photons traced by the Br-alpha line is significant even taking heavy dust extinction into consideration. We propose that dust within HII regions absorbs a significant fraction of ionizing photons.
We present a new catalog of 118 Ultraluminous Infrared Galaxies (ULIRGs) and one Hyperluminous Infrared Galaxy (HLIRG) by crossmatching AKARI all-sky survey with the Sloan Digital Sky Survey Data Release 10 (SDSS DR10) and the Final Data Release of t
We report on the results of systematic infrared 2.5-5 micron spectroscopy of 45 nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.3 using IRC onboard the AKARI satellite. This paper investigates whether the luminosities of these ULIRGs are dom
With the Infrared Camera on board AKARI, we carried out near-infrared (2.5-5.0 micron) spectroscopy of the central kiloparsec region of the barred spiral galaxy, NGC1097, categorized as Seyfert 1 with a circumnuclear starburst ring. Our observations
We present Keck-MOSFIRE H and K spectra for a sample of 24 candidate quiescent galaxies (QGs) at 3<z<4, identified from UVJ colors and photometric redshifts in the ZFOURGE and 3DHST surveys. We obtain spectroscopic redshifts for half of the sample, u
We present low resolution near-infrared spectroscopy of an unbiased sample of 24 ultraluminous infrared galaxies (ULIRGs), selected from samples previously observed spectroscopically in the mid-infrared with the Infrared Space Observatory (ISO). Qual