Potsdam Multi-Aperture Spectrophotometer Research Articles

LARS XIII: High Angular Resolution 21 cm H i Observations of Lyα Emitting Galaxies

The Lyα emission line is one of the main observables of galaxies at high redshift, but its output depends strongly on the neutral gas distribution and kinematics around the star-forming regions where UV photons are produced. We present observations of Lyα and 21 cm H i emission at comparable scales with the goal to qualitatively investigate how the neutral interstellar medium (ISM) properties impact Lyα transfer in galaxies. We have observed 21 cm H i at the highest possible angular resolution (≈3″ beam) with the Very Large Array in two local galaxies from the Lyman Alpha Reference Sample. We compare these data with Hubble Space Telescope Lyα imaging and spectroscopy, and Multi Unit Spectroscopic Explorer and Potsdam MultiAperture Spectrophotometer ionized gas observations. In LARS08, high-intensity Lyα emission is cospatial with high column density H i where the dust content is the lowest. The Lyα line is strongly redshifted, consistent with a velocity redistribution that allows Lyα escape from a high column density neutral medium with a low dust content. In eLARS01, high-intensity Lyα emission is located in regions of low column density H i, below the H i data sensitivity limit ( < 2 × 1020 cm−2). The perturbed ISM distribution with low column density gas in front of the Lyα emission region plays an important role in the escape. In both galaxies, the faint Lyα emission (∼1×10−16 erg s−1cm−2 arcsec−2) traces intermediate Hα emission regions where H i is found, regardless of the dust content. Dust seems to modulate, but not prevent, the formation of a faint Lyα halo. This study suggests the existence of scaling relations between dust, Hα, H i, and Lyα emission in galaxies.

Keck/OSIRIS IFU Detection of a z ∼ 3 Damped Lyα Host Galaxy∗

Abstract We present Keck/OSIRIS infrared IFU observations of the z = 3.153 sub-DLA DLA2233+131, previously detected in absorption to a background quasar and studied with single-slit spectroscopy and Potsdam Multi Aperture Spectrophotometer integral field spectroscopy (IFU). We used the Laser Guide Star Adaptive Optics and OSIRIS IFU to reduce the point-spread function of the background quasar to FWHM ∼ 0.″15 and marginally resolve extended, foreground DLA emission. We detect emission with a flux erg s−1 cm−2, as well as unresolved and Hβλ4861 emission. Using a composite spectrum over the emission region, we measure dynamical mass M ⊙. We made several estimates of star formation rate (SFR) using and Hβλ4861 emission, and measured a SFR of ∼7.1 − 13.6 M ⊙ yr−1. We map and Hβλ4861 emission and the corresponding velocity fields to search for signs of kinematic structure. These maps allow for a more detailed kinematic analysis than previously possible for this galaxy. While some regions show slightly red and blueshifted emission indicative of potential edge-on disk rotation, the data are insufficient to support this interpretation.

The interstellar medium of dwarf galaxies: new insights from Machine Learning analysis of emission-line spectra

Dwarf galaxies are ideal laboratories to study the physics of the interstellar medium (ISM). Emission lines have been widely used to this aim. Retrieving the full information encoded in the spectra is therefore essential. This can be efficiently and reliably done using Machine Learning (ML) algorithms. Here, we apply the ML code GAME to MUSE (Multi Unit Spectroscopic Explorer) and PMAS (Potsdam Multi Aperture Spectrophotometer) Integral Field Unit (IFU) observations of two nearby Blue Compact Galaxies (BCGs): Henize 2-10 and IZw18. We derive spatially resolved maps of several key ISM physical properties. We find that both galaxies show a remarkably uniform metallicity distribution. Henize 2-10 is a star forming dominated galaxy, with a Star Formation Rate (SFR) of about 1.2 M$_{\odot}$ yr$^{-1}$. Henize 2-10 features dense and dusty ($A_V$ up to 5-7 mag) star forming central sites. We find IZw18 to be very metal-poor ($Z$= 1/20 $Z_{\odot}$). IZw18 has a strong interstellar radiation field, with a large ionization parameter. We also use models of PopIII stars spectral energy distribution as a possible ionizing source for the HeII $\lambda$4686 emission detected in the IZw18 NW component. We find that PopIII stars could provide a significant contribution to the line intensity. The upper limit to the PopIII star formation is 52% of the total IZw18 SFR.

The Lyman alpha reference sample

We present integral field spectroscopic observations with the Potsdam Multi Aperture Spectrophotometer of all 14 galaxies in the $z\sim 0.1$ Lyman Alpha Reference Sample (LARS). We produce 2D line of sight velocity maps and velocity dispersion maps from the Balmer $\alpha$ (H$\alpha$) emission in our data cubes. These maps trace the spectral and spatial properties of the LARS galaxies' intrinsic Ly$\alpha$ radiation field. We show our kinematic maps spatially registered onto the Hubble Space Telescope H$\alpha$ and Lyman $\alpha$ (Ly$\alpha$) images. Only for individual galaxies a causal connection between spatially resolved H$\alpha$ kinematics and Ly$\alpha$ photometry can be conjectured. However, no general trend can be established for the whole sample. Furthermore, we compute non-parametric global kinematical statistics -- intrinsic velocity dispersion $\sigma_0$, shearing velocity $v_\mathrm{shear}$, and the $v_\mathrm{shear}/\sigma_0$ ratio -- from our kinematic maps. In general LARS galaxies are characterised by high intrinsic velocity dispersions (54\,km\,s$^{-1}$ median) and low shearing velocities (65\,km\,s$^{-1}$ median). $v_\mathrm{shear}/\sigma_0$ values range from 0.5 to 3.2 with an average of 1.5. Noteworthy, five galaxies of the sample are dispersion dominated systems with $v_\mathrm{shear}/\sigma_0 <1$ and are thus kinematically similar to turbulent star forming galaxies seen at high redshift. When linking our kinematical statistics to the global LARS Ly$\alpha$ properties, we find that dispersion dominated systems show higher Ly$\alpha$ equivalent widths and higher Ly$\alpha$ escape fractions than systems with $v_\mathrm{shear}/\sigma_0 > 1$. Our result indicates that turbulence in actively star-forming systems is causally connected to interstellar medium conditions that favour an escape of Ly$\alpha$ radiation.

Integral field spectroscopy of H ii regions in M33

Integral field spectroscopy (IFS) is presented for star forming regions in M33. A central area of 300 x 500 pc^2 and the external HII region IC 132, at a galactocentric distance {\sim} 19arcmin (4.69 kpc) were observed with the Potsdam Multi Aperture Spectrophotometer (PMAS) instrument at the 3.5 m telescope of the Calar Alto Hispano- Alem\'an observatory (CAHA). The spectral coverage goes from 3600 A to 1{\mu}m to include from [OII]{\lambda}3727 A to the near infrared lines required for deriving sulphur electron temperature and abundance diagnostics. Local conditions within individual HII regions are presented in the form of emission line fluxes and physical conditions for each spatial resolution element (spaxel) and for segments with similar H{\alpha} surface brightness. A clear dichotomy is observed when comparing the central to outer disc HII regions. While the external HII region has higher electron temperature plus larger H{\beta} equivalent width, size and excitation, the central region has higher extinction and metal content. The dichotomy extends to the BPT diagnostic diagrams that show two orthogonal broad distributions of points. By comparing with pseudo-3D photoionization models we conclude that the bulk observed differences are probably related to a different ionization parameter and metallicity. Wolf-Rayet features are detected in IC 132, and resolved into two concentrations whose integrated spectra were used to estimate the characteristic number of WR stars. No WR features were detected in the central HII regions despite their higher metallicity.

Integral field spectroscopy of selected areas of the Bright bar and Orion-S cloud in the Orion nebula★

We present integral field spectroscopy of two selected zones in the Orion Nebula obtained with the Potsdam Multi-Aperture Spectrophotometer (PMAS), covering the optical spectral range from 3500 to 7200 A and with a spatial resolution of 1". The observed zones are located on the prominent Bright Bar and on the brightest area at the northeast of the Orion South cloud, both containing remarkable ionization fronts. We obtain maps of emission line fluxes and ratios, electron density and temperatures, and chemical abundances. We study the ionization structure and morphology of both fields, which ionization fronts show different inclination angles with respect to the plane of the sky. We find that the maps of electron density, O+/H+ and O/H ratios show a rather similar structure. We interpret this as produced by the strong dependence on density of the [OII] lines used to derive the O+ abundance, and that our nominal values of electron density-derived from the [SII] line ratio-may be slightly higher than the appropriate value for the O+ zone. We measure the faint recombination lines of OII in the field at the northeast of the Orion South cloud allowing us to explore the so-called abundance discrepancy problem. We find a rather constant abundance discrepancy across the field and a mean value similar to that determined in other areas of the Orion Nebula, indicating that the particular physical conditions of this ionization front do not contribute to this discrepancy.

PMAS optical integral field spectroscopy of luminous infrared galaxies

The general properties of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in the local universe are well known since large samples of these objects have been the subject of numerous spectroscopic works. There are, however, relatively few studies of large samples of LIRGs and ULIRGs using integral field spectroscopy (IFS). We analyze optical (3800-7200A) IFS data taken with the Potsdam Multi-Aperture Spectrophotometer (PMAS) of the central few kiloparsecs of 11 LIRGs. To study the stellar populations we fit the optical stellar continuum and the hydrogen recombination lines of selected regions. We analyze the excitation conditions of the gas using the spatially resolved properties of the brightest optical emission lines. The optical continua of the selected regions are well fitted with a combination of evolved (~0.7-10Gyr) and ionizing (1-20Myr) stellar populations. The latter is more obscured than the evolved population, and has visual extinctions in good agreement with those obtained from the Balmer decrement. Except for NGC 7771, there is no clear evidence for an important contribution to the optical light from an intermediate-aged population (~100-500Myr). Even after correcting for the presence of stellar absorption, a large fraction of spaxels with low observed equivalent widths of Halpha in emission still show enhanced [NII]/Halpha and [SII]/Halpha ratios. These ratios are likely to be produced by a combination of photoionization in HII regions and diffuse emission. These regions of enhanced ratios are generally coincident with low surface brightness HII regions and diffuse emission detected in the Halpha and Pa-alpha images. Using the PMAS line ratios and the NICMOS Pa-alpha photometry of HII regions we find that the fraction of diffuse emission in LIRGs varies from galaxy to galaxy, and it is generally less than 60% as found in other starburst galaxies. (Abridged)

Mapping the properties of blue compact dwarf galaxies: integral field spectroscopy with PMAS

(Abridged) We perform integral field spectroscopy of a sample of Blue compact dwarf (BCD) galaxies with the aim of analyzing their morphology, the spatial distribution of some of their physical properties (excitation, extinction, and electron density) and their relationship with the distribution and evolutionary state of the stellar populations. Integral field spectroscopy observations of the sample galaxies were carried out with the Potsdam Multi-Aperture Spectrophotometer (PMAS) at the 3.5 m telescope at Calar Alto Observatory. An area 16 arcsec x 16 arcsec in size was mapped with a spatial sampling of 1 arcsec x 1 arcsec. We obtained data in the 3590-6996 Angstroms spectral range, with a linear dispersion of 3.2 Angstroms per pixel. From these data we built two-dimensional maps of the flux of the most prominent emission lines, of two continuum bands, of the most relevant line ratios, and of the gas velocity field. Integrated spectra of the most prominent star-forming regions and of whole objects within the FOV were used to derive their physical parameters and the gas metal abundances. Six galaxies display the same morphology both in emission line and in continuum maps; only in two objects, Mrk 32 and Tololo 1434+032, the distributions of the ionized gas and of the stars differ considerably. In general the different excitation maps for a same object display the same pattern and trace the star-forming regions, as expected for objects ionized by hot stars; only the outer regions of Mrk 32, I Zw 123 and I Zw 159 display higher [SII]/Halpha values, suggestive of shocks. Six galaxies display an inhomogeneous dust distribution. Regarding the kinematics, Mrk 750, Mrk 206 and I Zw 159 display a clear rotation pattern, while in Mrk 32, Mrk 475 and I Zw 123 the velocity fields are flat.

Integral field spectroscopy of H ii region complexes: the outer disc of NGC 6946

Integral field spectroscopy obtained with the Potsdam Multi-Aperture Spectrophotometer Fiber Package (PPak) and the 3.5-m telescope at the Calar Alto Observatory has been used to study an outer H ii region complex in the well-studied galaxy NGC 6946. This technique provides detailed maps of the region in different emission lines, yielding spatially resolved information about the physical properties of the gas. The configuration was chosen to cover the whole spectrum from 3600 up to 10 000 Å, allowing the measurement of the near-infrared [S iii] lines. We selected four luminous knots to perform a detailed integrated spectroscopic analysis of these structures and of the whole PPak field of view (FOV). For all the knots the electron density has been found to be very similar and below 100 cm−3. The [O iii] electron temperature was measured in knots A, B, C and in the integrated PPak field, and was found to be around 8000 K. The temperatures of [O ii] and [S iii] were estimated in the four cases. The elemental abundances computed from the ‘direct method’ are typical of high-metallicity disc H ii regions, with a mean value of 12+log(O/H) = 8.65, comparable to what has been found in this galaxy by other authors for regions at similar galactocentric distance. Therefore a remarkable abundance uniformity is found despite the different excitations found throughout the nebula. However, due to the quality of the data, the electron temperatures and metallicities obtained have associated errors comparable to the typical dispersion found in empirical calibrations. Wolf–Rayet (WR) features have been detected in three of the knots, leading to a derived total number of WR stars of 125, 22 and 5 for knots A, C and B, respectively. The ratios of the numbers of WR to O stars are consistent with the prediction of Starburst99 for individual bursts with an age about 4 Myr. Knot D, with no WR features, shows weak Hα emission, low excitation and the lowest Hβ equivalent width, all of which points to a more evolved state. The integrated spectrum of the whole PPak FOV shows high excitation and a relatively evolved age that does not correspond to the individual knot evolutionary stages. Some effects associated with the loss of spatial resolution are also evidenced by the higher ionizing temperature that is deduced from the η′ parameter measured in the integrated PPak spectrum with respect to that of the individual knots.

NEW LIGHT IN STAR-FORMING DWARF GALAXIES: THE PMAS INTEGRAL FIELD VIEW OF THE BLUE COMPACT DWARF GALAXY Mrk 409

We present an integral field spectroscopic study of the central 2x2 kpc^2 of the blue compact dwarf galaxy Mrk 409, observed with the Potsdam MultiAperture Spectrophotometer. This study focuses on the morphology, two-dimensional chemical abundance pattern, excitation properties and kinematics of the ionized interstellar medium in the starburst component. We also investigate the nature of the extended ring of ionized gas emission surrounding the bright nuclear starburst region of Mrk 409. PMAS spectra of selected regions along the ring, interpreted with evolutionary and population synthesis models, indicate that their ionized emission is mainly due to a young stellar population with a total mass of ~1.5x10^6 M_sun, which started forming almost coevally ~10 Myr ago. This stellar component is likely confined to the collisional interface of a spherically expanding, starburst-driven super-bubble with denser, swept-up ambient gas, ~600 pc away from the central starburst nucleus. The spectroscopic properties of the latter imply a large extinction (C_H-beta>0.9), and the presence of an additional non-thermal ionization source, most likely a low-luminosity Active Galactic Nucleus. Mrk 409 shows a relatively large oxygen abundance (12+log(O/H)~8.4) and no chemical abundance gradients out to R~600 pc. The ionized gas kinematics displays an overall regular rotation on a northwest-southwest axis, with a maximum velocity of 60 km/s; the total mass inside the star-forming ring is about 1.4x10^9 M_sun.

Mapping the starburst in blue compact dwarf galaxies

<i>Aims. <i/>By means of optical integral field spectroscopy observations, we aim to differentiate and characterize the starburst component in the blue compact dwarf (BCD) galaxy Mrk 1418. In particular we propose to study the stellar and ionized gas morphology, to investigate the ionization mechanism(s) acting in the interstellar medium, and to derive the physical parameters and abundances of the ionized gas.<i>Methods. <i/>Integral field spectroscopy observations of Mrk 1418 were carried out with the Potsdam multi-aperture spectrophotometer (PMAS) at the 3.5 m telescope at Calar Alto Observatory. The central 16″16″ (1.14 1.14 kpc<sup>2<sup/> at the distance of Mrk 1418) were mapped with a spatial sampling of 1″; we took data in the 3590-6996 Å spectral range, with a linear dispersion of 3.2 Å per pixel. The seeing was about 15. From these data we built maps of the most prominent emission lines, namely [O ii], H<i>β<i/>, [O iii], H<i>α<i/>, [N ii], and [S ii], as well as of several continuum bands, plus maps of the main line ratios: [O iii]/H<i>β<i/>, [N ii]/H<i>α<i/>, [S ii]/H<i>α<i/>, and H<i>α<i/>/H<i>β<i/>, and derived the physical parameters and gaseous metal abundances of the different star-forming regions detected in the field of view.<i>Results. <i/>Mrk 1418 shows a distorted morphology both in the continuum and in the ionized gas maps; the current star- formation episode is taking place in five knots, distributed around the nucleus of the galaxy. The interstellar medium surrounding these knots is photo-ionized by stars, with no clear evidence for other excitation mechanisms. The galaxy displays an inhomogeneous dust distribution, with the high H<i>α<i/>/H<i>β<i/> ratio in the central areas indicating a large amount of dust. The oxygen abundances derived for the individual star-forming knots are very similar, suggesting that the ionized interstellar medium is chemically homogeneous in O/H over spatial scales of hundreds of parsecs. This abundance (<i>Z<i/> <i>≈<i/> 0.4 from the empirical calibrations) places Mrk 1418 among the high metallicity BCD group.<i>Conclusions. <i/>These findings show the advantages of IFS when investigating the properties of such complex objects as BCDs, with an asymmetric star-forming component. Only a bidimensional mapping of their central regions allows approaching such questions as the star formation processes in BCDs, the star-forming history of the individual starburst knots, or the abundance gradients.

The interplay between ionized gas and massive stars in the HII galaxy IIZw70: integral field spectroscopy with PMAS

We performed an integral field spectroscopic study for the HII galaxy IIZw70 in order to investigate the interplay between its ionized interstellar medium (ISM) and the massive star formation (SF). Observations were taken in the optical spectral range (3700-6800 A) with the Potsdam Multi-Aperture Spectrophotometer (PMAS) attached to the 3.5 m telescope at CAHA. We created and analysed maps of spatially distributed emission-lines, continuum emission and properties of the ionized ISM (e.g. physical-chemical conditions, dust extinction, kinematics). We investigated the relation of these properties to the spatial distribution and evolutionary stage of the massive stars. For the first time we have detected the presence of Wolf-Rayet (WR) stars in this galaxy. The peak of the ionized gas emission coincides with the location of the WR bump. The region of the galaxy with lower dust extinction corresponds to the region that shows the lowest values of velocity dispersion and radial velocity. The overall picture suggests that the ISM of this region is being disrupted via photoionization and stellar winds, leading to a spatial decoupling between gas+stars and dust clouds. The bulk of dust appears to be located at the boundaries of the region occupied by the probable ionizing cluster. We also found that this region is associated to the nebular emission in HeII4686 and to the intensity maximum of most emission lines. This indicates that the hard ionizing radiation responsible for the HeII4686 nebular emission can be related to the youngest stars. Within $\sim$ 0.4 x 0.3 kpc^2 in the central burst, we derived O/H using direct determinations of Te[OIII]. We found abundances in the range 12+log(O/H)=7.65-8.05, yielding an error-weighted mean of 12+log(O/H)=7.86 $\pm$0.05.

PMAS: The Potsdam Multi‐Aperture Spectrophotometer. II. The Wide Integral Field Unit PPak

ABSTRACTPPak is a new fiber‐based integral field unit (IFU) developed at the Astrophysical Institute of Potsdam and implemented as a module into the existing Potsdam Multi‐Aperture Spectrophotometer (PMAS) spectrograph. The purpose of PPak is to provide an extended field of view with a large light‐collecting power for each spatial element, as well as an adequate spectral resolution. The PPak system consists of a fiber bundle with 331 object fibers, 36 sky fibers, and 15 calibration fibers. The object and sky fibers collect the light from the focal plane behind a focal reducer lens. The object fibers of PPak, each 2 .″7 in diameter, provide a contiguous hexagonal field of view of 74″ × 64″ on the sky, with a filling factor of 60%. The operational wavelength range is from 400 to 900 nm. The PPak IFU, together with the PMAS spectrograph, are intended for the study of extended, low surface brightness objects, offering an optimization of total light‐collecting power and spectral resolution. This paper describes the instrument design, the assembly, integration, and tests, the commissioning and operational procedures, and presents the measured performance at the telescope.

Abundances and kinematics of a candidate sub-damped Lymanα galaxy toward PHL 1226

The spectrum of the quasar PHL 1226 is known to have a strong Mg II and sub-damped Lyman-alpha (sub-DLA) absorption line system with N(HI)=(5+/-2)*10^19 cm^-2 at z=0.1602. Using integral field spectra from the Potsdam Multi Aperture Spectrophotometer (PMAS) we investigate a galaxy at an impact parameter of 6".4 which is most probably responsible for the absorption lines. A fainter galaxy at a similar redshift and a slightly larger distance from the QSO is known to exist, but we assume that the absorption is caused by the more nearby galaxy. From optical Balmer lines we estimate an intrinsic reddening consistent with 0, and a moderate star formation rate of 0.5 M_sun yr^-1, is inferred from the Halpha luminosity. Using nebular emission line ratios we find a solar oxygen abundance 12+log(O/H)=8.7+/-0.1 and a solar nitrogen to oxygen abundance ratio log(N/O)=-1.0+/-0.2. This abundance is larger than those of all known sub-DLA systems derived from analyses of metal absorption lines in quasar spectra. On the other hand, the properties are compatible with the most metal rich galaxies responsible for strong Mg II absorption systems. These two categories can be reconciled if we assume an abundance gradient similar to local galaxies. Under that assumption we predict abundances 12+log(O/H)=7.1 and log(N/O)=-1.9 for the sub-DLA cloud, which is similar to high redshift DLA and sub-DLA systems. We find evidence for a rotational velocity of ~200 km s^-1 over a length of ~7 kpc. From the geometry and kinematics of the galaxy we estimate that the absorbing cloud does not belong to a rotating disk, but could originate in a rotating halo.

Integral field spectroscopy of extended Ly$\mathsf{\alpha}$ emission from the DLA galaxy in Q2233+131

This paper presents observations of an extended Lyman-alpha emission nebula surrounding the galaxy responsible for the Damped Lyman-alpha Absorption (DLA) line in the spectrum of the quasar Q2233+131. With the Potsdam Multi Aperture Spectrophotometer (PMAS) we measure the properties of the extended Ly-alpha emission in an area of 3"* 5" having a total line flux of (2.8+/-0.3)*10^{-16} erg cm-2 s-1, which at redshift z=3.15 corresponds to a luminosity of (2.4 -0.2/+0.3)*10^{43} erg s-1 and a size of 23 times 38 kpc. The location of the emission is spatially coincident with the previously detected DLA galaxy, but extends significantly beyond its limb. We argue that the Ly-alpha emission is likely to be caused by an outflow from the DLA galaxy, presumably powered by star formation. In the case of negligible dust extinction, the Ly-alpha luminosity indicates a star-formation rate of 19+/-10 solar masses per year consistent with that derived from the UV continuum flux from the parent galaxy. The wind velocity indicated by the integral field spectra is of the order of several hundred km s-1. We find no indication of emission originating in a rotating disk.

Integral field spectrophotometry of gravitationally lensed QSOs with PMAS

AbstractWe present spatially resolved spectrophotometric observations of multiply imaged QSOs, using the Potsdam Multi‐Aperture Spectrophotometer (PMAS), with the intention to search for spectral differences between components indicative of either microlensing or dust extinction. For the quadruple QSO HE 0435–1223 we find that the continuum shapes are indistinguishable, therefore differential extinction is negligible. The equivalent widths of the broad emission lines are however significantly different, and we argue that this is most likely due to microlensing. Contrariwise, the two components of the well‐known object UM 673 have virtually identical emission line properties, but the continuum slopes differ significantly and indicate different dust extinction along both lines of sight. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Integral field observations of damped Lyman‐α galaxies

AbstractWe report preliminary results from a targeted investigation on quasars containing damped Lyman‐α absorption (DLA) lines as well strong metal absorption lines, carried out with the Potsdam Multi Aperture Spectrophotometer (PMAS). We search for line‐emitting objects at the same redshift as the absorption lines and close to the line of sight of the QSOs. We have observed and detected the already confirmed absorbing galaxies in Q2233+131 (zabs = 3.15) and Q0151+045 (zabs=0.168), while failing to find spectral signatures for the z = 0.091 absorber in Q0738+313. From the Q2233+131 DLA galaxy, we have detected extended Lyα emission from an area of 3″ ×5″. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Integral-field spectrophotometry of the quadruple QSO HE 0435-1223: Evidence for microlensing

We present the first spatially resolved spectroscopic observations of the recently discovered quadruple QSO and gravitational lens HE 0435 1223. Using the Potsdam Multi-Aperture Spectrophotometer (PMAS), we show that all four QSO components have very similar but not identical spectra. In particular, the spectral slopes of components A, B, and D are indistinguishable, implying that extinction due to dust plays no major role in the lensing galaxy. While also the emission line profiles are identical within the error bars, as expected from lensing, the equivalent widths show significant di erences between components. Most likely, microlensing is responsible for this phenomenon. This is also consistent with the fact that component D, which shows the highest relative continuum level, has brightened by 0.07 mag since Dec. 2001. We find that the emission line flux ratios between the components are in better agreement with simple lens models than broad band or continuum measurements, but that the discrepancies between model and data are still unacceptably large. Finally, we present a detection of the lensing galaxy, although this is close to the limits of the data. Comparing with a model galaxy spectrum, we obtain a redshift estimate of zlens= 0:44 0:02.

Integral field spectroscopy of SN 2002er with PMAS

We present observations of the Type Ia supernova SN 2002er during the brightening phase. The observations were performed with the Potsdam Multi Aperture Spectrophotometer (PMAS) integral field instrument. Due to the 8"*8", field of view of the spectrograph an accurate background subtraction was possible. Results from analyses of the evolution of absorption features in comparisons with other SNe show that SN 2002er is a fairly bright Type Ia supernova with a peak brightness of M_B=-19.6+-0.1.

Ultra-Deep Optical Spectroscopy with PMAS. Using the Nod-and-Shuffle Technique

PMAS, the Potsdam Multi-Aperture Spectrophotometer, is a new integral field spectrograph in the optical, which is optimized for good transmission and high image quality from 350 nm to 1 μm. We present our plan to implement a CCD charge-shuffle mode to allow for beam switching with a very high degree of sky subtraction accuracy for faint object 3-D spectroscopy.