Spatially resolved properties of the grand-design spiral galaxy UGC 9837: a case for high-redshift 2D observations
K. Viironen, S. F. Sanchez, E. Marmol-Queralto, J. Iglesias-Paramo, D. Mast, R. A. Marino, D. Cristobal-Hornillos, A. Gil de Paz, G. van de Ven, J. Vilchez, L. Wisotzki
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12 pages, 9 figures, accepted for publication in A&A
Context. We carry out a detailed 2D study of the ionised gas in the local universe galaxy UGC9837. In nearby galaxies, like the galaxy in question here, the spatial distribution of the physical properties can be studied in detail, providing benchmarks for galaxy formation models.
Aims. Our aim is to derive detailed and spatially resolved physical properties of the ionised gas of UGC 9837. In addition, we derive an integrated spectrum of the galaxy and study how varying spatial coverage affects the derived integrated properties. We also study how the same properties would be seen if the galaxy was placed at a higher redshift and observed as part of one of the high-z surveys.
Methods. UGC9837 was observed using the PMAS PPAK integral field unit. The spectra are reduced and calibrated and the stellar and ionised components separated. Using strong emission line ratios of the ionised gas, the source of ionisation, the dust extinction, the star formation rate, the electron density and the oxygen abundance derived from a total integrated spectrum, central integrated spectrum and individual fibre spectra are studied. Finally, the same properties are studied in a spectrum whose spatial resolution is degraded to simulate high-z observations.
Results. The spatial distribution of the ionised gas properties is consistent with inside-out growing scenario of galaxies. We also find that lack of spatial coverage would bias the results derived from the integrated spectrum leading, e.g., to an under-estimation of ionisation and over-estimation of metallicity, if only the centre of the galaxy was covered by the spectrum. Our simulation of high-z observations shows that part of the spatial information, such as dust and SFR distribution would be lost while shallower gradients in metallicity and ionisation strength would be detected.
UGC 3995 is an interacting and occulting galaxy pair. UGC 3995B is a foreground face-on spiral and UGC 3995A a bright background spiral with an AGN. We present analysis of the dust in the disc of UGC 3995B based on archival Hubble Space Telescope WFPC2 and PPAK IFU data from the CALIFA survey's first data release. From the HST F606W image, we construct an extinction map by modeling the isophotes of the background galaxy UGC 3995A and the resulting transmission through UGC 3995B. This extinction map of UGC 3995B shows several distinct spiral extinction features. The radial distribution of $A_V$…
We use Herschel PACS and SPIRE observations of the edge-on spiral galaxy UGC 4754, taken as part of the H-ATLAS SDP observations, to investigate the dust energy balance in this galaxy. We build detailed SKIRT radiative models based on SDSS and UKIDSS maps and use these models to predict the far-infrared emission. We find that our radiative transfer model underestimates the observed FIR emission by a factor of two to three. Similar discrepancies have been found for other edge-on spiral galaxies based on IRAS, ISO, and SCUBA data. Thanks to the good sampling of the SED at FIR wavelengths, we can…
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Although relatively common in the local Universe, only one grand-design spiral galaxy has been spectroscopically confirmed to lie at z>2 (HDFX 28; z=2.011), and may prove to be a major merger that simply resembles a spiral in projection. The rarity of spirals has been explained as a result of disks being dynamically 'hot' at z>2 which may instead favor the formation of commonly-observed clumpy structures. Alternatively, current instrumentation may simply not be sensitive enough to detect spiral structures comparable to those in the modern Universe. At redshifts <2, the velocity dispersion of d…
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HII regions in the arms of spiral galaxies are indicators of recent star-forming processes. They may have been caused by the passage of the density wave or simply created by other means near the arms. The study of these regions may give us clues to clarifying the controversy over the existence of a triggering scenario, as proposed in the density wave theory. Using H$α$ direct imaging, we characterize the HII regions from a sample of three grand design galaxies: NGC5457, NGC628 and NGC6946. Broad band images in R and I were used to determine the position of the arms. The HII regions found to be…
We present a detailed and unique mass budget for the high-surface-brightness galaxy UGC 463, showing it is dominated by dark matter (DM) at radii beyond one scale length (h_R) and has a baryonic-to-DM mass ratio of approximately 1:3 within 4.2 h_R. Assuming a constant scale height (h_z, calculated via an empirical oblateness relation), we calculate dynamical disk mass surface densities from stellar kinematics, which provide vertical velocity dispersions after correcting for the shape of the stellar velocity ellipsoid (measured to have sigma_theta/sigma_R=1.04 +/- 0.22 and sigma_z/sigma_R=0.48 …
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Deep, near-infrared JHK-maps were observed for 10 nearby, grand-design, spiral galaxies using HAWK-I/VLT to study the distribution of young stellar clusters in them and thereby determine whether strong spiral perturbations can influence star formation. Complete, magnitude-limited candidate lists of star-forming complexes were obtained by searching within the K-band maps. The properties of the complexes were derived from (H-K)-(J-H) diagrams including the identification of the youngest complexes (i.e. <7 Myr) and the estimation of their extinction. Young stellar clusters with ages <7 Myr have s…
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