Optical and near-infrared integral field spectroscopy of the SCUBA galaxy N2 850.4
Monthly Notices of the Royal Astronomical Society 359:2 (2005) 401-407
Abstract:
We present optical and near-infrared integral field spectroscopy of the SCUBA galaxy SMM J163650.43+405734.5 (ELAIS N2 850.4) at z = 2.385. We combine Lyα and Hα emission line maps and velocity structure with high-resolution HST ACS and NICMOS imaging to probe the complex dynamics of this vigorous starburst galaxy. The imaging data show a complex morphology, consisting of at least three components separated by ∼1 arcsec (8 kpc) in projection. When combined with the Hα velocity field from UKIRT UIST IFU observations we identify two components whose redshifts are coincident with the systemic redshift, measured from previous CO observations, one of which shows signs of AGN activity. A third component is offset by 220 ± 50 km s -1 from the systemic velocity. The total star-formation rate of the whole system (estimated from the narrow-line Hα and uncorrected for reddening) is 340 ± 50 M⊙ yr-1. The Lyα emission mapped by the GMOS IFU covers the complete galaxy and is offset by +270 ± 40 km s-1 from the systemic velocity. This velocity offset is comparable to that seen in rest-frame UV-selected galaxies at similar redshifts and usually interpreted as a starburst-driven wind. The extended structure of the Lyα emission suggests that this wind is not a nuclear phenomenon, but is instead a galactic-scale outflow. Our observations suggest that the vigorous activity in N2 850.4 is arising as a result of an interaction between at least two dynamically-distinct components, resulting in a strong starburst, a starburst-driven wind and actively-fuelled AGN activity. Whilst these observations are based on a single object, our results clearly show the power of combining optical and near-infrared integral field spectroscopy to probe the power sources, masses and metallicities of far-infrared luminous galaxies, as well as understanding the role of AGN- and starburst-driven feedback processes in these high-redshift systems. © 2005 RAS.Spitzer imaging of i′-drop galaxies:: old stars at z≈ 6
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 364:2 (2005) 443-454
CIRPASS: Description, performance and astronomical results
Proceedings of SPIE - The International Society for Optical Engineering 5492:PART 2 (2004) 1135-1144
Abstract:
The Cambridge Infra-red Panoramic Survey Spectrograph (CIRPASS) is described. This near-infrared (MR) spectrograph has been used on the 8m Gemini-South Telescope, the 3.9m Anglo-Australian Telescope (AAT) and the 4.2m William Herschel Telescope (WHT). Its performance in both integral field mode and multi-object mode is discussed and some scientific highlights are presented. A multi-IFU system, which is currently under construction, is also described.The star formation rate of the Universe at z ≈ 6 from the Hubble Ultra-Deep Field
Monthly Notices of the Royal Astronomical Society 355:2 (2004) 374-384
Abstract:
We determine the abundance of i′-band dropouts in the recently released HST/ACS Hubble Ultra-Deep Field (UDF). Because the majority of these sources are likely to be z ≈ 6 galaxies whose flux decrement between the F775W i′-band and F850LP z′-band arises from Lyman-α absorption, the number of detected candidates provides a valuable upper limit to the unextincted star formation rate at this redshift. We demonstrate that the increased depth of UDF enables us to reach an 8 σ limiting magnitude of z′AB = 28.5 (equivalent to 1.5 h10-2 M⊙ yr-1 at z = 6.1, or 0.1 LUV* for the z ≈ 3 U-drop population), permitting us to address earlier ambiguities arising from the unobserved form of the luminosity function. We identify 54 galaxies (and only one star) at zAB′ < 28.5 with (i′ - z′)AB > 1-3 over the deepest 11-arcmin2 portion of the UDF. The characteristic luminosity (L*) is consistent with values observed at z ≈ 3. The faint end slope (α) is less well constrained, but is consistent with only modest evolution. The main change appears to be in the number density (φ*). Specifically, and regardless of possible contamination from cool stars and lower-redshift sources, the UDF data support our previous result that the star formation rate at z ≈ 6 was approximately six times less than at z ≈ 3. This declining comoving star formation rate [0.005 h70 M⊙ yr-1 Mpc-3 at z ≈ 6 at LUV > 0. 1 L* for a Salpeter initial mass function (IMF)] poses an interesting challenge for models which suggest that LUV > 0.1 L* star-forming galaxies at z ≃ 6 reionized the Universe. The short-fall in ionizing photons might be alleviated by galaxies fainter than our limit, or a radically different IMF. Alternatively, the bulk of reionization might have occurred at z ≫ 6.Multi-object near-infrared Hα spectroscopy of z ∼ 1 star-forming galaxies in the Hubble Deep Field North
Monthly Notices of the Royal Astronomical Society 354:1 (2004)