# Posts Tagged spectro

## Recent Postings from spectro

### Short dynamic fibrils in sunspot chromospheres

Sunspot chromospheres display vigorous oscillatory signature when observed in chromospheric diagnostics like the strong Ca II lines and H-alpha. New high-resolution sunspot observations from the Swedish 1-m Solar Telescope show the ubiquitous presence of small-scale periodic jet-like features that move up and down. This phenomenon has not been described before. Their typical width is about 0.3 arcsec and they display clear parabolic trajectories in space-time diagrams. The maximum extension of the top of the jets is lowest in the umbra, a few 100 km, and progressively longer further away from the umbra in the penumbra, with the longest more than 1000 km. These jets resemble dynamic fibrils found in plage regions but at smaller extensions. LTE inversion of spectro-polarimetric Ca II 8542 observations enabled for a comparison of the magnetic field inclination and the properties of these short jets. We find that the most extended of these jets also have longer periods and tend to be located in regions with more horizontal magnetic fields. This is a direct observational confirmation of the mechanism of long-period waves propagating along inclined magnetic fields into the solar chromosphere. This mechanism was identified earlier as the driver of dynamic fibrils in plage, part of the mottles in quiet Sun, and type I spicules at the limb. The sunspot dynamic fibrils that we report here represent a new class of manifestation of this mechanism. They are not the same as the transient penumbral and umbral micro-jets reported earlier.

### A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255: I. C IV absorption variability

Broad Absorption Lines indicate gas outflows with velocities from thousands km/s to about 0.2 the speed of light, which may be present in all quasars and may play a major role in the evolution of the host galaxy. The variability of absorption patterns can provide informations on changes of the density and velocity distributions of the absorbing gas and its ionization status. We collected 23 photometrical and spectro-photometrical observations at the 1.82m Telescope of the Asiago Observatory since 2003, plus other 5 spectra from the literature. We analysed the evolution in time of the equivalent width of the broad absorption feature and two narrow absorption systems, the correlation among them and with the R band magnitude. We performed a structure function analysis of the equivalent width variations. We present an unprecedented monitoring of a broad absorption line quasar based on 28 epochs in 14 years. The shape of broad absorption feature shows a relative stability, while its equivalent width slowly declines until it sharply increases during 2011. In the same time the R magnitude stays almost constant until it sharply increases during 2011. The equivalent width of the narrow absorption redwards of the systemic redshift only shows a decline. The broad absorption behaviour suggests changes of the ionisation status as the main cause of variability. We show for the first time a correlation of this variability with the R band flux. The different behaviour of the narrow absorption system might be due to recombination time delay. The structure function of the absorption variability has a slope comparable with typical optical variability of quasars. This is consistent with variations of the 200 A ionising flux originating in the inner part of the accretion disk.

### DIGIT: Herschel and Spitzer spectro-imaging of SMM3 and SMM4 in Serpens

We report on spectro-imaging observations employing Spitzer IRS and Herschel PACS, aiming to constrain the physical conditions around SMM3 and SMM4 in Serpens. The combined power of both instruments provides an almost complete wavelength coverage between 5 and 200 micron at an angular resolution of 10". We detect line emission from all major molecular (H2, CO, H2O and OH) and many atomic ([OI], [CII], [FeII], [SiII] and [SI]) coolants. Line emission tends to peak at distances of 10 – 20" from the protostellar sources, at positions of known outflow shocks. The only exception is [CII] which likely traces a PDR excited from the neighboring source SMM6. Excitation analysis indicates that H2 and CO originate from gas at two distinct rotational temperatures of 300 K and 1000 K, while H2O and OH emission corresponds to rotational temperatures of 100 – 200 K. The morphological and physical association between CO and H2 suggests a common excitation mechanism which allows direct comparisons between the two molecules. The CO/H2 abundance ratio varies from 10^-5 in the warm gas up to 10^-4 in the hotter regions. The occurrence of J-shocks is suggested by the strong atomic/ionic (except for [CII]) emission as well as a number of line ratio diagnostics. Both C- and J-shocks can account for the observed molecular emission, however J-shocks are strongly advocated by the atomic emission and provide simpler and more homogeneous solutions for CO and H2. C-shocks describe better the emission from H2O and OH. The variations in the CO/H2 abundance ratio for gas at different temperatures can be interpreted by their reformation rates in dissociative J-type shocks, or the simultaneous influence of both C and J shocks.

### VLT/X-Shooter Near-Infrared Spectroscopy and HST Imaging of Gravitationally-Lensed z~2 Compact Quiescent Galaxies

Quiescent massive galaxies at z~2 are thought to be the progenitors of present-day massive ellipticals. Observations revealed them to be extraordinarily compact. The determination of stellar ages, star formation rates and dust properties via spectroscopic measurements has up to now only been feasible for the most luminous and massive specimens (~3x M*). Here we present a spectroscopic study of two near-infrared selected galaxies which are close to the characteristic stellar mass M* (~0.9x M* and ~1.3x M*) and whose observed brightness has been boosted by the gravitational lensing effect. We measure the redshifts of the two galaxies to be z=1.71\pm0.02 and z=2.15\pm0.01. By fitting stellar population synthesis models to their spectro-photometric SEDs we determine their ages to be 2.4^{+0.8}_{-0.6} Gyr and 1.7\pm0.3 Gyr, respectively, which implies that the two galaxies have higher mass-to-light ratios than most quiescent z~2 galaxies in other studies. We find no direct evidence for active star-formation or AGN activity in either of the two galaxies, based on the non-detection of emission lines. Based on the derived redshifts and stellar ages we estimate the formation redshifts to be z=4.3^{+3.4}_{-1.2} and z=4.3^{+1.0}_{-0.6}, respectively. We use the increased spatial resolution due to the gravitational lensing to derive constraints on the morphology. Fitting Sersic profiles to the de-lensed images of the two galaxies confirms their compactness, with one of them being spheroid-like, and the other providing the first confirmation of a passive lenticular galaxy at a spectroscopically derived redshift z~2.

### VLT/X-Shooter Near-Infrared Spectroscopy and HST Imaging of Gravitationally-Lensed z~2 Compact Quiescent Galaxies [Replacement]

Quiescent massive galaxies at z~2 are thought to be the progenitors of present-day massive ellipticals. Observations revealed them to be extraordinarily compact. The determination of stellar ages, star formation rates and dust properties via spectroscopic measurements has up to now only been feasible for the most luminous and massive specimens (~3x M*). Here we present a spectroscopic study of two near-infrared selected galaxies which are close to the characteristic stellar mass M* (~0.9x M* and ~1.3x M*) and whose observed brightness has been boosted by the gravitational lensing effect. We measure the redshifts of the two galaxies to be z=1.71\pm0.02 and z=2.15\pm0.01. By fitting stellar population synthesis models to their spectro-photometric SEDs we determine their ages to be 2.4^{+0.8}_{-0.6} Gyr and 1.7\pm0.3 Gyr, respectively, which implies that the two galaxies have higher mass-to-light ratios than most quiescent z~2 galaxies in other studies. We find no direct evidence for active star-formation or AGN activity in either of the two galaxies, based on the non-detection of emission lines. Based on the derived redshifts and stellar ages we estimate the formation redshifts to be z=4.3^{+3.4}_{-1.2} and z=4.3^{+1.0}_{-0.6}, respectively. We use the increased spatial resolution due to the gravitational lensing to derive constraints on the morphology. Fitting Sersic profiles to the de-lensed images of the two galaxies confirms their compactness, with one of them being spheroid-like, and the other providing the first confirmation of a passive lenticular galaxy at a spectroscopically derived redshift z~2.

### Magnetic field strength distribution of magnetic bright points inferred from filtergrams and spectro-polarimetric data

Small scale magnetic fields can be observed on the Sun in G-band filtergrams as MBPs (magnetic bright points) or identified in spectro-polarimetric measurements due to enhanced signals of Stokes profiles. These magnetic fields and their dynamics play a crucial role in understanding the coronal heating problem and also in surface dynamo models. MBPs can theoretically be described to evolve out of a patch of a solar photospheric magnetic field with values below the equipartition field strength by the so-called convective collapse model. After the collapse, the magnetic field of MBPs reaches a higher stable magnetic field level. The magnetic field strength distribution of small scale magnetic fields as seen by MBPs is inferred. Furthermore, we want to test the model of convective collapse and the theoretically predicted stable value of about 1300 G. We used four different data sets of high-resolution Hinode/SOT observations that were recorded simultaneously with the broadband filter device (G-band, Ca II-H) and the spectro-polarimeter. To derive the magnetic field strength distribution of these small scale features, the spectropolarimeter (SP) data sets were treated by the Merlin inversion code. The four data sets comprise different solar surface types: active regions (a sunspot group and a region with pores), as well as quiet Sun. In all four cases the obtained magnetic field strength distribution of MBPs is similar and shows peaks around 1300 G. This agrees well with the theoretical prediction of the convective collapse model. The resulting magnetic field strength distribution can be fitted in each case by a model consisting of log-normal components. The important parameters, such as geometrical mean value and multiplicative standard deviation, are similar in all data sets, only the relative weighting of the components is different.

### Using head-tail galaxies to constrain the intracluster magnetic field: an in-depth study of PKS J0334-3900

We present a multi-wavelength study of the radio galaxy PKS J0334-3900 at the centre of Abell 3135. The spectro-polarimetric radio observations are combined with spectroscopic optical and X-ray data to illustrate the use of Head-Tail radio galaxies to reveal properties of the intracluster medium. ATCA observations at 1.4, 2.5, 4.6 & 8.6 GHz are presented with a detailed analysis of the morphology and spectral indices giving physical parameters to constrain the dynamical history of the galaxy. Using these constraints we produce a simulation of PKS J0334-3900. We find that this Head-Tail morphology can be induced via a combination of orbital motion due to a binary companion and relative motion through the ICM. New Chandra images of A3135 are presented from which we obtain a cluster electron density of n_(e,0) = (1.06 +/- 0.11 x 10^(-3) cm^(-3), a global temperature of 2.4 ^(+0.51)_(-0.38) keV and a lower limit to the radio jet power of PKS J0334-3900 of 1.6 x 10^(44) erg/s. A new redshift analysis of the cluster from available spectroscopic data shows A3135 to be comprised of galaxies with 0.058 < z < 0.066 and gives a new mean cluster redshift of 0.06228 +/- 0.00015. We also uncovered a background subgroup between 0.066 < z < 0.070. Stokes Q and U data of Abell 3135 were used to obtain rotation measure values along the line of sight to PKS J0334-3900. Using our simulation we are able to infer the distance between the jets to be 154 +/- 16 kpc, which when combined with the difference in vector-averaged rotation measure between the jets provides a novel new way to estimate the average magnetic field within a cluster. A lower limit to the cluster B-field was calculated to be 0.28 +/- 0.03 micro Gauss. We show observations of Head-Tail galaxies can be used to infer information on the cluster environment, showing them to be an important class of objects in next generation all sky surveys.

### Using head-tail galaxies to constrain the intracluster magnetic field: an in-depth study of PKS J0334-3900 [Replacement]

We present a multi-wavelength study of the radio galaxy PKS J0334-3900 at the centre of Abell 3135. The spectro-polarimetric radio observations are combined with spectroscopic optical and X-ray data to illustrate the use of Head-Tail radio galaxies to reveal properties of the intracluster medium. ATCA observations at 1.4, 2.5, 4.6 & 8.6 GHz are presented with a detailed analysis of the morphology and spectral indices giving physical parameters to constrain the dynamical history of the galaxy. Using these constraints we produce a simulation of PKS J0334-3900. We find that this Head-Tail morphology can be induced via a combination of orbital motion due to a binary companion and relative motion through the ICM. New Chandra images of A3135 are presented from which we obtain a cluster electron density of n_(e,0) = (1.06 +/- 0.11 x 10^(-3) cm^(-3), a global temperature of 2.4 ^(+0.51)_(-0.38) keV and a lower limit to the radio jet power of PKS J0334-3900 of 1.6 x 10^(44) erg/s. A new redshift analysis of the cluster from available spectroscopic data shows A3135 to be comprised of galaxies with 0.058 < z < 0.066 and gives a new mean cluster redshift of 0.06228 +/- 0.00015. We also uncovered a background subgroup between 0.066 < z < 0.070. Stokes Q and U data of Abell 3135 were used to obtain rotation measure values along the line of sight to PKS J0334-3900. Using our simulation we are able to infer the distance between the jets to be 154 +/- 16 kpc, which when combined with the difference in rotation measure between the jets provides a novel new way to estimate the average magnetic field within a cluster. A lower limit to the cluster B-field was calculated to be 0.09 +/- 0.03 micro Gauss. We show observations of Head-Tail galaxies can be used to infer information on the cluster environment, showing them to be an important class of objects in next generation all sky surveys.

### Kappa Fornaci, a triple radio-star

Bright and nearby (22pc) solar-type dwarf Kappa Fornaci (HIP 11072) is a triple system. The close pair of M-type dwarfs Ba,Bb with a tentative period of 3.7 days moves around the main component A on a 26-year orbit. The mass of the "dark companion" Ba+Bb is comparable to the mass of A, causing large motion of the photo-center. The combined spectro-interferometric orbit of AB is derived and the relative photometry of the components A and B is given. A weak signature of Ba and Bb is detected in the high-resolution spectra by cross-correlation and by variable emission in the Bahlmer hydrogen lines. The activity of the M-dwarfs, manifested by a previously detected radio-flare, is likely maintained by synchronization with their tight orbit. We discuss the frequency of similar hidden triple systems, methods of their detection, and the implications for multiple-star statistics.

### A Comparison Between Nonlinear Force-Free Field and Potential Field Models Using Full-Disk SDO/HMI Magnetogram

Measurements of magnetic fields and electric currents in the pre-eruptive corona are crucial to study solar eruptive phenomena, like flare and coronal mass ejections(CMEs). However, spectro-polarimetric measurements of certain photospheric lines permit a determination of the vector magnetic field at the photosphere. Thus, substantial collection of magnetograms relate to the photospheric surface field only. Numerical modeling is carried out by applying state-of-the-art nonlinear force-free field (NLFFF) reconstruction. Cartesian nonlinear force-free field (NLFFF) codes are not well suited for larger domains, since the spherical nature of the solar surface cannot be neglected when the field of view is large. One of the most significant results of Solar Dynamic Observatory (SDO) mission to date has been repeated observations of large, almost global scale events in which large scale connection between active regions may play fundamental role. Therefore, it appears prudent to implement a NLFFF procedure in spherical geometry for use when large scale boundary data are available, such as from the Helioseismic and Magnetic Imager (HMI) on board SDO. In this work, we model the coronal magnetic field above multiple active regions with the help of a potential field and a NLFFF extrapolation codes in a full-disk using HMI data as a boundary conditions. We compare projections of the resulting magnetic field lines solutions with full-disk coronal images from the Atmospheric Imaging Assembly (SDO/AIA) for both models. This study has found that the NLFFF model reconstructs the magnetic configuration better than the potential field model. We have concluded that much of trans-equatorial loops connecting the two solar hemispheres are current-free.

### A Comparison Between Nonlinear Force-Free Field and Potential Field Models Using Full-Disk SDO/HMI Magnetogram [Replacement]

Measurements of magnetic fields and electric currents in the pre-eruptive corona are crucial to study solar eruptive phenomena, like flare and coronal mass ejections(CMEs). However, spectro-polarimetric measurements of certain photospheric lines permit a determination of the vector magnetic field at the photosphere. Thus, substantial collection of magnetograms relate to the photospheric surface field only. Numerical modeling is carried out by applying state-of-the-art nonlinear force-free field (NLFFF) reconstruction. Cartesian nonlinear force-free field (NLFFF) codes are not well suited for larger domains, since the spherical nature of the solar surface cannot be neglected when the field of view is large. One of the most significant results of Solar Dynamic Observatory (SDO) mission to date has been repeated observations of large, almost global scale events in which large scale connection between active regions may play fundamental role. Therefore, it appears prudent to implement a NLFFF procedure in spherical geometry for use when large scale boundary data are available, such as from the Helioseismic and Magnetic Imager (HMI) on board SDO. In this work, we model the coronal magnetic field above multiple active regions with the help of a potential field and a NLFFF extrapolation codes in a full-disk using HMI data as a boundary conditions. We compare projections of the resulting magnetic field lines solutions with full-disk coronal images from the Atmospheric Imaging Assembly (SDO/AIA) for both models. This study has found that the NLFFF model reconstructs the magnetic configuration better than the potential field model. We have concluded that much of trans-equatorial loops connecting the two solar hemispheres are current-free.

### Constraining mass ratio and extinction in the FU Orionis binary system with infrared integral field spectroscopy

We report low resolution near infrared spectroscopic observations of the eruptive star FU Orionis using the Integral Field Spectrograph Project 1640 installed at the Palomar Hale telescope. This work focuses on elucidating the nature of the faint source, located 0.5" south of FU Ori, and identified in 2003 as FU Ori S. We first use our observations in conjunction with published data to demonstrate that the two stars are indeed physically associated and form a true binary pair. We then proceed to extract J and H band spectro-photometry using the damped LOCI algorithm, a reduction method tailored for high contrast science with IFS. This is the first communication reporting the high accuracy of this technique, pioneered by the Project 1640 team, on a faint astronomical source. We use our low resolution near infrared spectrum in conjunction with 10.2 micron interferometric data to constrain the infrared excess of FU Ori S. We then focus on estimating the bulk physical properties of FU Ori S. Our models lead to estimates of an object heavily reddened, A_V =8-12, with an effective temperature of ~ 4000-6500 K . Finally we put these results in the context of the FU Ori N-S system and argue that our analysis provides evidence that FU Ori S might be the more massive component of this binary system

### Probing local density inhomogeneities in the circumstellar disk of a Be star using the new spectro-astrometry mode at the Keck interferometer

We report on the successful science verification phase of a new observing mode at the Keck interferometer, which provides a line-spread function width and sampling of 150km/s at K’-band, at a current limiting magnitude of K’~7mag with spatial resolution of lam/2B ~2.7mas and a measured differential phase stability of unprecedented precision (3mrad at K=5mag, which represents 3uas on sky or a centroiding precision of 10^-3). The scientific potential of this mode is demonstrated by the presented observations of the circumstellar disk of the evolved Be-star 48Lib. In addition to indirect methods such as multi-wavelength spectroscopy and polaritmetry, the here described spectro-interferometric astrometry provides a new tool to directly constrain the radial density structure in the disk. We resolve for the first time several Pfund emission lines, in addition to BrGam, in a single interferometric spectrum, and with adequate spatial and spectral resolution and precision to analyze the radial disk structure in 48Lib. The data suggest that the continuum and Pf-emission originates in significantly more compact regions, inside of the BrGam emission zone. Thus, spectro-interferometric astrometry opens the opportunity to directly connect the different observed line profiles of BrGam and Pfund in the total and correlated flux to different disk radii. The gravitational potential of a rotationally flattened Be star is expected to induce a one-armed density perturbation in the circumstellar disk. Such a slowly rotating disk oscillation has been used to explain the well known periodic V/R spectral profile variability in these stars, as well as the observed V/R cycle phase shifts between different disk emission lines. The differential line properties and linear constraints set by our data lend support to the existence of a radius-dependent disk density perturbation.

### The 2008-2009 outburst of the young binary system Z CMa unraveled by interferometry with high spectral resolution

Z CMa is a young binary system consisting of an Herbig primary and a FU Ori companion. Both components seem to be surrounded by active accretion disks and a jet was associated to the Herbig B0. In Nov. 2008, K. Grankin discovered that Z CMa was exhibiting an outburst with an amplitude larger than any photometric variations recorded in the last 25 years. To study the innermost regions in which the outburst occurs and understand its origin, we have observed both binary components with AMBER/VLTI across the Br{\gamma} emission line in Dec. 2009 in medium and high spectral resolution modes. Our observations show that the Herbig Be, responsible for the increase of luminosity, also produces a strong Br{\gamma} emission, and they allow us to disentangle from various origins by locating the emission at each velocities through the line. Considering a model of a Keplerian disk alone fails at reproducing the asymmetric spectro-astrometric measurements, suggesting a major contribution from an outflow.