arXiv subjects

N. P. H. Nesvadba

Publications and source records attributed to N. P. H. Nesvadba.

42 records · Page 3Linked to original sources

arXiv2008

Rotation on sub-kpc scales in the strongly lensed z~3 'arc&core' and implications for high-redshift galaxy dynamics

Strongly lensed galaxies at high redshift provide a unique window into the early universe. We compare the internal kinematics of the strongly lensed Lyman-break galaxy (LBG) 'arc&core' at z=3.2 (the first strongly lensed z~3 LBG with the signs of rotation on sub-kiloparsec scales) with an LBG that is not gravitationally lensed, as well as with a larger sample of actively star-forming galaxies at slightly lower redshifts. All galaxies have deep rest-frame optical integral-field spectroscopy obtained with the VLT. The unlensed galaxies appear to have a larger ratio of random to bulk motion. Field galaxies also have broader lines than strongly lensed LBGs with rest-optical spectroscopy, where spectra were extracted from regions with similar physical size. To ensure observational success, studies of high-redshift galaxy kinematics often focus on bright and luminous targets, and our comparison suggests that this may lead to a serious bias.

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arXiv2007

Integral-field spectroscopy of a Lyman-Break Galaxy at z=3.2: evidence for merging

We present spatially-resolved, rest-frame optical spectroscopy of a z~3 Lyman-break galaxy (LBG), Q0347-383 C5, obtained with SINFONI on the VLT. This galaxy, among the ~10% brightest LBGs, is only the second z~3 LBG observed with an integral-field spectrograph. It was first described by Pettini et al. (2001), who obtained WFPC2 F702W imaging and longslit spectroscopy in the K-band. We find that the emission line morphology is dominated by two unresolved blobs at a projected distance of ~5 kpc with a velocity offset of ~33 km s^-1. Velocity dispersions suggest that each blob has a mass of ~10^10 M_sun. Unlike Pettini et al. (2001), our spectra are deep enough to detect H-beta, and we derive star-formation rates of ~20-40 M_sun yr^-1, and use the H-beta/[OIII] ratio to crudely estimate an oxygen abundance 12+[O/H]=7.9-8.6, which is in the range typically observed for LBGs. We compare the properties of Q0347-383 C5 with what is found for other LBGs, including the gravitationally lensed ``arc+core'' galaxy (Nesvadba et al. 2006), and discuss possible scenarios for the nature of the source, namely disk rotation, a starburst-driven wind, disk fragmentation, and merging of two LBGs. We favor the merging interpretation or bright, extended LBGs like Q0347-383C5, in broad agreement with predicted merger rates from hierarchical models.

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arXiv2007

Compact radio sources and jet-driven AGN feedback in the early Universe: Constraints from integral-field spectroscopy

To investigate the impact of radio jets during the formation epoch of their massive host galaxies, we present an analysis of two massive, log(M_stel/ M_sun)~10.6 and 11.3, compact radio galaxies at z=3.5, TNJ0205+2242 and TNJ0121+1320. Their small radio sizes (R<= 10 kpc) are most likely a sign of youth. We compare their radio properties and gas dynamics with those in well extended radio galaxies at high redshift, which show strong evidence for powerful, jet-driven outflows of significant gas masses (M 10^9-10 M_sun). Our analysis combines rest-frame optical integral-field spectroscopy with existing radio imaging, CO emission line spectra, and rest-frame UV spectroscopy. [OIII]5007 line emission is compact in both galaxies and lies within the region defined by the radio lobes. For TNJ0205+2242, the Ly-alpha profile narrows significantly outside the jet radius, indicating the presence of a quiescent halo. TNJ0121+1320 has two components separated by ~10 kpc and a velocity offset of ~300 km s^-1. If motions are gravitational, this implies a dynamical mass of 2x10^11 M_sun for the more massive, radio-loud component. The dynamical mass, molecular gas mass measured from the CO line emission, and radio luminosity of these two compact radio galaxies imply that compact radio sources may well develop large-scale, energetic outflows as observed in extended radio galaxies, with the potential of removing significant fractions of the ISM from the host galaxy. The absence of luminous emission line gas extending beyond the radio emission in these sources agrees with the observed timescales and outflow rates in extended radio galaxies, and adds further evidence that the energetic, large-scale outflows observed in extended radio sources (Nesvadba et al. 2006) are indeed the result of influence of the radio jet.

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arXiv2006

Intense Star-formation and Feedback at High Redshift: Spatially-resolved Properties of the z=2.6 Submillimeter Galaxy SMMJ14011+0252

We present a detailed analysis of the spatially-resolved properties of the lensed submillimeter galaxy SMMJ14011+0252 at z=2.56, combining deep near-infrared integral-field data obtained with SPIFFI on the VLT with other multi-wavelength data sets. The broad characteristics of SMMJ14011+0252 are in agreement with what is expected for the early evolution of local massive spheroidal galaxies. From continuum and line flux, velocity, and dispersion maps, we measure the kinematics, star-formation rates, gas densities, and extinction for individual subcomponents. The star formation intensity is similar to low-redshift ``maximal starbursts'', while the line fluxes and the dynamics of the emission line gas provide direct evidence for a starburst-driven wind with physical properties very similar to local superwinds. We also find circumstantial evidence for "self-regulated" star formation within J1. The relative velocity of the bluer companion J2 yields a dynamical mass estimate for J1 within about 20 kpc, M_dyn \sim 1\times 10^{11} M_sun. The relative metallicity of J2 is 0.4 dex lower than in J1n/s, suggesting different star formation histories. SED fitting of the continuum peak J1c confirms and substantiates previous suggestions that this component is a z=0.25 interloper. When removing J1c, the stellar continuum and H-alpha line emission appear well aligned spatially in two individual components J1n and J1s, and coincide with two kinematically distinct regions in the velocity map, which might well indicate a merging system. This highlights the close similarity between SMGs and ULIRGs, which are often merger-driven maximal starbursts, and suggests that the intrinsic mechanisms of star-formation and related feedback are similar to low-redshift strongly star-forming systems.

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arXiv2006

Lyman Break Galaxies Under a Microscope: The Small Scale Dynamics and Mass of an Arc in the Cluster 1E0657-56

Using the near-infrared integral-field spectrograph SPIFFI on the VLT, we have studied the spatially-resolved dynamics in the z=3.2 strongly lensed galaxy 1E0657-56 ``arc+core''. The lensing configuration suggests that the high surface brightness ``core'' is the M=20 magnified central 1 kpc of the galaxy (seen at a spatial resolution of about 200 pc in the source plane), whereas the fainter ``arc'' is a more strongly magnified peripheral region of the same galaxy at about a half-light radius, which otherwise appears to be a typical z=3 Lyman break galaxy. The overall shape of the position-velocity diagram resembles the ``rotation curves'' of the inner few kpcs of nearby L* spiral galaxies. The projected velocities rise rapidly to 75 km/s within the core. This implies a dynamical mass of M_dyn = 10^9.3 M_sun within the central kpc, and suggests that in this system the equivalent of the mass of a present-day L* bulge at the same radius was already in place by z>=3. Approximating the circular velocity of the halo by the measured asymptotic velocity of the rotation curve, we estimate a dark matter halo mass of M_halo = 10^11.7 +/- 0.3, in good agreement with large-scale clustering studies of Lyman break galaxies. The baryonic collapse fraction is low compared to actively star-forming ``BX'' and low-redshift galaxies around z=2, perhaps implying comparatively less gas infall to small radii or efficient feedback. Even more speculatively, the high central mass density might indicate highly dissipative gas collapse in very early stages of galaxy evolution, in approximate agreement with what is expected for ``inside-out'' galaxy formation models.

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arXiv2006

Extreme gas kinematics in the z=2.2 powerful radio galaxy MRC1138-262: Evidence for efficient AGN feedback in the early Universe?

To explain the properties of the most massive low-redshift galaxies and the shape of their mass function, recent models of galaxy evolution include strong AGN feedback to complement starburst-driven feedback in massive galaxies. Using the near-infrared integral-field spectrograph SPIFFI on the VLT, we searched for direct evidence for such a feedback in the optical emission line gas around the z=2.16 powerful radio galaxy MRC1138-262, likely a massive galaxy in formation. The kpc-scale kinematics, with FWHMs and relative velocities <= 2400 km/s and nearly spherical spatial distribution, do not resemble large-scale gravitational motion or starburst-driven winds. Order-of-magnitude timescale and energy arguments favor the AGN as the only plausible candidate to accelerate the gas, with a total energy injection of a few x 10^60 ergs or more, necessary to power the outflow, and relatively efficient coupling between radio jet and ISM. Observed outflow properties are in gross agreement with the models, and suggest that AGN winds might have a similar, or perhaps larger, cosmological significance than starburst-driven winds, if MRC1138-262 is indeed archetypal. Moreover, the outflow has the potential to remove significant gas fractions (<= 50%) from a >L* galaxy within a few 10 to 100 Myrs, fast enough to preserve the observed [alpha/Fe] overabundance in massive galaxies at low redshift. Using simple arguments, it appears that feedback like that observed in MRC1138-262 may have sufficient energy to inhibit material from infalling into the dark matter halo and thus regulate galaxy growth as required in some recent models of hierarchical structure formation.

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