arXiv subjects

Martin Haas

Publications and source records attributed to Martin Haas.

At least 37 records · Page 2Linked to original sources

arXiv2018

Simultaneous H alpha and dust reverberation mapping of 3C120: Testing the bowl-shaped torus geometry

At the Universitaetssternwarte Bochum near Cerro Armazones we have monitored the Seyfert-1 galaxy 3C 120 between September 2014 and March 2015 in BVRI and a narrow band filter covering the redshifted H alpha line; in addition we obtained a single con-temporary spectrum with FAST at Mt. Hopkins. Compared to earlier epochs 3C 120 is about a factor of three brighter, allowing us to study the shape of the broad line region (BLR) and the dust torus in a high luminosity phase. The analysis of the light curves yields that the dust echo is rather sharp and symmetric in contrast to the more complex broad H alpha BLR echo. We investigate how far this supports an optically thick bowl-shaped BLR and dust torus geometry as proposed by Kawaguchi & Mori (2010) and Goad et al. (2012). The comparison with several parameterizations of these models supports the following geometry: the BLR clouds lie inside the bowl closely above the bowl rim, up to a half covering angle 0 deg < theta < 40 deg (measured against the equatorial plane). Then the BLR is spread over many isodelay surfaces, yielding a smeared and structured echo as observed. Furthermore, if the BLR clouds shield the bottom of the bowl rim against radiation from the nucleus, the hot dust emission comes essentially from the top edge of the bowl (40 deg < theta < 45 deg). Then, for small inclinations as for 3C120, the top dust edge forms a ring which largely coincides with a narrow range of isodelay surfaces, yielding the observed sharp dust echo. The scale height of the BLR increases with radial distance from the black hole. This leads to luminosity dependent foreshortening effects of the lag. We discuss implications and possible corrections of the foreshortening for the black hole mass determination and consequences for the lag (size) - luminosity relationships and the difference to interferometric torus sizes.

astro-ph.GA↗

arXiv2017

Starburst-driven superwinds in quasar host galaxies

During five decades astronomers have been puzzled by the presence of strong absorption features including metal lines, observed in the optical and ultraviolet spectra of quasars, signalling in- and outflowing gas winds with relative velocities up to several thousands of km/sec. In particular the location of these winds - close to the quasar, further out in its host galaxy, or in its direct environment - and the possible impact on their surroundings have been issues of intense discussion and uncertainty. Using our Herschel Space Observatory data, we report a tendency for this so-called associated metal absorption to occur along with prodigious star formation in the quasar host galaxy, indicating that the two phenomena are likely to be interrelated, that the gas winds likely occur on the kiloparsec scale and would then have a strong impact on the interstellar medium of the galaxy. This correlation moreover would imply that the unusually high cold dust luminosities in these quasars are connected with ongoing star formation. Given that we find no correlation with the AGN strength, the wind feedback which we establish in these radio-loud objects is most likely associated with their host star formation rather than with their black hole accretion.

astro-ph.GA↗

arXiv2016

Star formation in 3CR radio galaxies and quasars at z < 1

Using the Herschel Space Observatory we have observed a representative sample of 87 powerful 3CR sources at redshift z < 1. The far-infrared (FIR, 70-500 micron) photometry is combined with mid-infrared (MIR) photometry from the Wide-Field Infrared Survey Explorer (WISE) and catalogued data to analyse the complete spectral energy distributions (SEDs) of each object from optical to radio wavelength. To disentangle the contributions of different components, the SEDs are fitted with a set of templates to derive the luminosities of host galaxy starlight, dust torus emission powered by active galactic nuclei (AGN) and cool dust heated by stars. The level of emission from relativistic jets is also estimated, in order to isolate the thermal host galaxy contribution. The new data are in line with the orientation-based unification of high-excitation radio-loud AGN, in that the dust torus becomes optically thin longwards of 30 micron. The low excitation radio galaxies and the MIR weak sources represent MIR- and FIR-faint AGN population different from the high-excitation MIR-bright objects; it remains an open question whether they are at a later evolutionary state or an intrinsically different population. The derived luminosities for host starlight and dust heated by star formation are converted to stellar masses and star formation rates (SFR). The host-normalized SFR of the bulk of the 3CR sources is low when compared to other galaxy populations at the same epoch. Estimates of the dust mass yield a 1--100 times lower dust/stellar mass ratio than for the Milky Way, indicating that these 3CR hosts have very low levels of interstellar matter explaining the low level of star formation. Less than 10% of the 3CR sources show levels of star formation above those of the main sequence of star forming galaxies.

astro-ph.GA↗

arXiv2015

The stability of the optical flux variation gradient for 3C120

New $B$- and $V$-band monitoring in 2014 $-$ 2015 reveals that the Seyfert 1 Galaxy, 3C120, has brightened by a magnitude of $1.4$, compared to our campaign that took place in 2009 $-$ 2010. This allowed us to check for the debated luminosity and time-dependent color variations claimed for SDSS quasars. For our 3C120 data, we find that the $B/V$ flux ratio of the variable component in the bright epoch is indistinguishable from the faint one. We do not find any color variability on different timescales ranging from about $1$ to $1800$ days. We suggest that the luminosity and time-dependent color variability is an artifact caused by analyzing the data in magnitudes instead of fluxes. The flux variation gradients of both epochs yield consistent estimates of the host galaxy contribution to our 7.5" aperture. These results confirm that the optical flux variation gradient method works well for Seyfert galaxies.

astro-ph.GA↗

arXiv2014

3C 220.3: a radio galaxy lensing a submillimeter galaxy

Herschel Space Observatory photometry and extensive multiwavelength followup have revealed that the powerful radio galaxy 3C 220.3 at z=0.685 acts as a gravitational lens for a background submillimeter galaxy (SMG) at z=2.221. At an observed wavelength of 1mm, the SMG is lensed into three distinct images. In the observed near infrared, these images are connected by an arc of 1.8" radius forming an Einstein half-ring centered near the radio galaxy. In visible light, only the arc is apparent. 3C 220.3 is the only known instance of strong galaxy-scale lensing by a powerful radio galaxy not located in a galaxy cluster and therefore it offers the potential to probe the dark matter content of the radio galaxy host. Lens modeling rejects a single lens, but two lenses centered on the radio galaxy host A and a companion B, separated by 1.5", provide a fit consistent with all data and reveal faint candidates for the predicted fourth and fifth images. The model does not require an extended common dark matter halo, consistent with the absence of extended bright X-ray emission on our Chandra image. The projected dark matter fractions within the Einstein radii of A (1.02") and B (0.61") are about 0.4 +/- 0.3 and 0.55 +/- 0.3. The mass to i-band light ratios of A and B, M/L ~ 8 +/- 4 Msun/Lsun, appear comparable to those of radio-quiet lensing galaxies at the same redshift in the CASTLES, LSD, and SL2S samples. The lensed SMG is extremely bright with observed f(250um) = 440mJy owing to a magnification factor mu~10. The SMG spectrum shows luminous, narrow CIV 154.9nm emission, revealing that the SMG houses a hidden quasar in addition to a violent starburst. Multicolor image reconstruction of the SMG indicates a bipolar morphology of the emitted ultraviolet (UV) light suggestive of cones through which UV light escapes a dust-enshrouded nucleus.

astro-ph.GA↗

arXiv2013

The substellar content of the ONC

The Substellar Initial Mass Function (SIMF) of many star-forming regions is still poorly known but the detailed knowledge of its shape will help to distinguish among the substellar formation theories. The Orion Nebula Cluster (ONC) is one of the most extensively studied star forming regions. We here present deep, wide-field JHK observations of the ONC taken with HAWK-I@VLT. These observations extend the IMF into the brown dwarf and free-floating planetary mass regime with unprecedented sensitivity. To obtain a clean sample of ONC members, we exclude potential background sources with the help of CO extinction maps. Masses are assigned by means of evolutionary tracks in the H vs. J-H Color-Magnitude Diagram (CMD). Besides the well known stellar peak at ~0.25 M_sun we find a pronounced second peak at ~0.04 M_sun in the SIMF and indications for a third rise in the free-floating planetary mass regime.

astro-ph.SR↗

arXiv2013

Revealing the heavily obscured AGN population of High Redshift 3CRR Sources with Chandra X-ray Observations

Chandra observations of a complete, flux-limited sample of 38 high-redshift (1 0) indicating obscuration (log N_H ~ 22-24 cm^-2). These properties and the correlation between obscuration and radio core-fraction are consistent with orientation-dependent obscuration as in Unification models. About half the NLRGs have soft X-ray hardness ratios and/or high [OIII] emission line to X-ray luminosity ratio suggesting obscuration by Compton thick (CT) material so that scattered nuclear or extended X-ray emission dominates (as in NGC1068). The ratios of unobscured to Compton-thin (10^{22}< N_H(int) < 1.5 x 10^{24} cm^-2) to CT (N_H(int) > 1.5 x 10^{24} cm^-2) is 2.5:1.4:1 in this high luminosity, radio-selected sample. The obscured fraction is 0.5, higher than is typically reported for AGN at comparable luminosities from multi-wavelength surveys (0.1-0.3). Assuming random nuclear orientation, the unobscured half-opening angle of the disk/wind/torus structure is ~ 60deg and the obscuring material covers 30deg of which ~ 12deg is Compton thick. The multi-wavelength properties reveal that many NLRGs have intrinsic absorption 10-1000x higher than indicated by their X-ray hardness ratios, and their true L_X values are ~10--100x larger than the hardness-ratio absorption corrections would indicate.

astro-ph.CO↗

arXiv2013

The extended narrow-line region of two type-I quasi-stellar objects

We investigate the narrow-line region (NLR) of two radio-quiet QSOs, PG1012+008 and PG1307+085, using high signal-to-noise spatially resolved long-slit spectra obtained with FORS1 at the Very Large Telescope. Although the emission is dominated by the point-spread function of the nuclear source, we are able to detect extended NLR emission out to several kpc scales in both QSOs by subtracting the scaled central spectrum from outer spectra. In contrast to the nuclear spectrum, which shows a prominent blue wing and a broad line profile of the [O III] line, the extended emission reveals no clear signs of large scale outflows. Exploiting the wide wavelength range, we determine the radial change of the gas properties in the NLR, i.e., gas temperature, density, and ionization parameter, and compare them with those of Seyfert galaxies and type-II QSOs. The QSOs have higher nuclear temperature and lower electron density than Seyferts, but show no significant difference compared to type-II QSOs, while the ionization parameter decreases with radial distance, similar to the case of Seyfert galaxies. For PG1012+008, we determine the stellar velocity dispersion of the host galaxy. Combined with the black hole mass, we find that the luminous radio-quiet QSO follows the local M_BH-sigma* relation of active galactic nuclei.

astro-ph.CO↗

arXiv2012

Extreme host galaxy growth in powerful early-epoch radio galaxies

During the first half of the universe's age, a heyday of star-formation must have occurred because many massive galaxies are in place after that epoch in cosmic history. Our observations with the revolutionary Herschel Space Observatory reveal vigorous optically obscured star-formation in the ultra-massive hosts of many powerful high-redshift 3C quasars and radio galaxies. This symbiotic occurrence of star-formation and black hole driven activity is in marked contrast to recent results dealing with Herschel observations of X-ray selected active galaxies. Three archetypal radio galaxies, at redshifts 1.132,1.575, and 2.474 are presented here, with inferred star-formation rates of hundreds of solar masses per year. A series of spectacular coeval AGN/starburst events may have formed these ultra-massive galaxies and their massive central black holes during their relatively short lifetimes.

astro-ph.CO↗

arXiv2012

Toward Understanding the Origin of Turbulence in Molecular Clouds: Small Scale Structures as Units of Dynamical Multi-Phase Interstellar Medium

In order to investigate the origin of the interstellar turbulence, detailed observations in the CO J=1--0 and 3--2 lines have been carried out in an interacting region of a molecular cloud with an HII region. As a result, several 1,000 to 10,000 AU scale cloudlets with small velocity dispersion are detected, whose systemic velocities have a relatively large scatter of a few km/s. It is suggested that the cloud is composed of small-scale dense and cold structures and their overlapping effect makes it appear to be a turbulent entity as a whole. This picture strongly supports the two-phase model of turbulent medium driven by thermal instability proposed previously. On the surface of the present cloud, the turbulence is likely to be driven by thermal instability following ionization shock compression and UV irradiation. Those small scale structures with line width of ~ 0.6 km/s have a relatively high CO line ratio of J=3--2 to 1--0, 1 < R(3-2/1-0) < 2. The large velocity gradient analysis implies that the 0.6 km/s width component cloudlets have an average density of 10^{3-4} cm^{-3}, which is relatively high at cloud edges, but their masses are only < 0.05 M_{sun}.

astro-ph.GA↗

arXiv2011

Chandra X-ray Observations of the redshift 1.53, radio-loud quasar: 3C 270.1

Chandra X-ray observations of the high redshift (z =1.532) radio-loud quasar 3C270.1 in 2008 February show the nucleus to have a power-law spectrum, Gamma = 1.66 +/- 0.08, typical of a radio-loud quasar, and a marginally-detected Fe Kalpha emission line. The data also reveal extended X-ray emission, about half of which is associated with the radio emission from this source. The southern emission is co-spatial with the radio lobe and peaks at the position of the double radio hotspot. Modeling this hotspot including Spitzer upper limits rules out synchrotron emission from a single power-law population of electrons, favoring inverse-Compton emission with a field of ~11nT, roughly a third of the equipartition value. The northern emission is concentrated close to the location of a 40 deg. bend where the radio jet is presumed to encounter external material. It can be explained by inverse Compton emission involving Cosmic Microwave Background photons with a field of ~3nT, roughly a factor of nine below the equipartition value. The remaining, more diffuse X-ray emission is harder (HR=-0.09 +/- 0.22). With only 22.8+/-5.6 counts, the spectral form cannot be constrained. Assuming thermal emission with a temperature of 4 keV yields an estimate for the luminosity of 1.8E44 erg/s, consistent with the luminosity-temperature relation of lower-redshift clusters. However deeper Chandra X-ray observations are required to delineate the spatial distribution, and better constrain the spectrum of the diffuse emission to verify that we have detected X-ray emission from a high-redshift cluster.

astro-ph.HE↗

arXiv2011

Megamaser detection and nuclear obscuration in Seyfert galaxies

We revisit the relation between H2O maser detection rate and nuclear obscuration for a sample of 114 Seyfert galaxies, drawn from the CfA, 12um and IRAS F25/F60 catalogs. These sources have mid-infrared spectra from the Spitzer Space Telescope and they are searched for X-ray and [O III], 5007Angstrom fluxes from the literature. We use the strength of the [O IV], 25.9um emission line as tracer for the intrinsic AGN strength. After normalization by [O IV] the observed X-ray flux provides information about X-ray absorption. The distribution of X-ray / [O IV] flux ratios is significantly different for masers and non-masers: The maser detected Seyfert-2s (Sy 1.8-2.0) populate a distinct X-ray / [O IV] range which is, on average, about a factor four lower than the range of Seyfert-2 non-masers and about a factor of ten lower than the range of Seyfert-1s (Sy 1.0-1.5). Non-masers are almost equally distributed over the entire X-ray / [O IV] range. This provides evidence that high nuclear obscuration plays a crucial role for the probability of maser detection. Furthermore, after normalization with [O IV], we find a similar but weaker trend for the distribution of the maser detection rate with the absorption of the 7um dust continuum. This suggests that the obscuration of the 7 um continuum occurs on larger spatial scales than that of the X-rays. Hence, in the AGN unified model, at moderate deviation from edge-on, the 7um dust absorption may occur without proportionate X-ray absorption. The absorption of [O III] appears unrelated to maser detections. The failure to detect masers in obscured AGN is most likely due to insufficient observational sensitivity.

astro-ph.CO↗

arXiv2010

Tracing the sites of obscured star formation in the Antennae galaxies with Herschel-PACS

FIR imaging of interacting galaxies allows locating even hidden sites of star formation and measuring of the relative strength of nuclear and extra-nuclear star formation. We want to resolve the star-forming sites in the nearby system of the Antennae. Thanks to the unprecedented sharpness and depth of the PACS camera onboard ESA's Herschel Space Observatory, it is possible for the first time to achieve a complete assessment of individual star-forming knots in the FIR with scan maps at 70, 100, and 160 um. We used clump extraction photometry and SED diagnostics to derive the properties related to star-forming activity. The PACS 70, 100, and 160 um maps trace the knotty structure of the most recent star formation along an arc between the two nuclei in the overlap area. The resolution of the starburst knots and additional multi-wavelength data allow their individual star formation history and state to be analysed. In particular, the brightest knot in the mid-infrared (K1), east of the southern nucleus, exhibits the highest activity by far in terms of dust heating and star formation rate, efficiency, and density. With only 2 kpc in diameter, this area has a 10-1000 um luminosity, which is as high as that of our Milky Way. It shows the highest deficiency in radio emission in the radio-to-FIR luminosity ratio and a lack of X-ray emission, classifying it as a very young complex. The brightest 100 and 160 um emission region (K2), which is close to the collision front and consists of 3 knots, also shows a high star formation density and efficiency and lack of X-ray emission in its most obscured part, but an excess in the radio-to-FIR luminosity ratio. This suggests a young stage, too, but different conditions in its interstellar medium. Our results provide important checkpoints for numerical simulations of interacting galaxies when modelling the star formation and stellar feedback.

astro-ph.CO↗

arXiv2009

Polycyclic aromatic hydrocarbon selected galaxies

Polycyclic aromatic hydrocarbon (PAH) emission has been found in both starbursts and modestly starforming galaxies, but the relation between starforming activity and PAH luminosity is still a matter of debate. The different correlation degrees could be caused by the variety of optical and far-infrared sample selection criteria. In order to obtain a census of the typical properties of PAH emitting galaxies, we here study moderately distant galaxies which have been selected by their PAH emission. Combining the ISOCAM Parallel Survey at 6.7 micron with 2MASS we have colour-selected a sample of 120 candidates for strong PAH emission. We obtained optical and mid-infrared spectra of 75 and 19 sources, respectively, and analysed IRAS-ADDSCANs and available Spitzer 3.6-160 micron photometry. The Spitzer spectra exhibit clear PAH features and corroborate that our photometric selection criteria trace the PAH emission of galaxies fairly well. The optical spectra show emission lines, at median redshift z~0.1, as well as Hdelta and CaII absorption, indicating ongoing starformation as well as post-starbursts. The mid- and far-infrared spectral energy distributions (SEDs) provide evidence for a broad range of far-infrared (FIR) luminosities, but in general the dust is colder than for starburst galaxies like M82. For most galaxies the monocromatic luminosity peaks at about equal height at optical, 6.7 micron (PAH) and FIR wavelengths. In about 15% of the sources the FIR luminosity exceeds the optical and PAH energy output by about a factor 5-10 despite the cool dust temperature; in these galaxies a large dust mass of 10^8 - 10^9 M_sun is inferred.

astro-ph.CO↗

arXiv2009

Clustering of red galaxies around the z=1.53 quasar 3C270.1

In the paradigm of hierarchical galaxy formation, luminous radio galaxies mark mass assembly peaks that should contain clusters of galaxies. Observations of the z=1.53 quasar 3C270.1 with the Spitzer Space Telescope at 3.6-24 micron and with the 6.5-m MMT in the z'- and Y-bands allow detection of potential cluster members via photometric redshifts. Compared with nearby control fields, there is an excess of 11 extremely red objects (EROs) at 1.33 < z_phot < 1.73, consistent with a proto-cluster around the quasar. The spectral energy distributions (SEDs) of 3/4 of the EROs are better fitted with passive elliptical galaxies than withdust-reddened starbursts, and of four sources well-detected on an archival HST snapshot image, all have undisturbed morphologies. However, one ERO, not covered by the HST image, is a double source with 0.8" separation on the z' image and a marginal (2sigma) 24 micron detection indicating a dust-enshrouded starburst. The EROs are more luminous than L* (H = -23.6 AB mag at z=1.5).

astro-ph.GA↗

arXiv2007

VISIR/VLT mid-infrared imaging of Seyfert nuclei: Nuclear dust emission and the Seyfert-2 dichotomy

Half of the Seyfert-2 galaxies escaped detection of broad lines in their polarised spectra observed so far. Some authors have suspected that these non-HBLRs contain real Sy2 nuclei without intrinsic broad line region hidden behind a dust torus. If this were true, then their nuclear structure would fundamentally differ from that of Sy2s with polarised broad lines: in particular, they would not be explained by orientation-based AGN unification. Further arguments for two physically different Sy2 populations have been derived from the warm and cool IRAS F25/F60 ratios. These ratios, however, refer to the entire host galaxies and are unsuitable to conclusively establish the absence of a nuclear dust torus. Instead, a study of the Seyfert-2 dichotomy should be performed on the basis of nuclear properties only. Here we present the first comparison between [OIII] 5007A and mid-infrared imaging at matching spatial resolution. Exploring the Seyfert-2 dichotomy we find that the distributions of nuclear mid-infrared/[OIII] luminosity ratios are indistinguishable for Sy1s and Sy2s with and without detected polarised broad lines and irrespective of having warm or cool IRAS F25/F60 ratios. We find no evidence for the existence of a population of real Sy2s with a deficit of nuclear dust emission. Our results suggest 1) that all Seyfert nuclei possess the same physical structure including the putative dust torus and 2) that the cool IRAS colours are caused by a low contrast of AGN to host galaxy. Then the Seyfert-2 dichotomy is explained in part by unification of non-HBLRs with narrow-line Sy1s and to a larger rate by observational biases caused by a low AGN/host contrast and/or an unfavourable scattering geometry.

astro-ph↗

arXiv2007

Two-Loop Effects and Current Status of the 4He+ Lamb Shift

We report on recent progress in the treatment of two-loop binding corrections to the Lamb shift, with a special emphasis on S and P states. We use these and other results in order to infer an updated theoretical value of the Lamb shift in 4He+.

physics.atom-ph↗

arXiv2006

Unification of 3CR Radio Galaxies and Quasars

We have observed seven powerful FR2 radiogalaxies and seven quasars with the Spitzer IRS. Both samples are comparable in both, redshift range and isotropic 178 Hz luminosity. Both samples are found to have similar distributions in the luminosity ratios of Mid-IR high- and low-excitation lines ([NeV]/[NeII]), and of Mid-IR high-excitation line to radio power ratio ([NeV]/P_178MHz). However, the MIR/FIR ratio is generally higher for quasars. We further observed Silicate features at 10 and 18micron in emission. In our sample only quasars show emission features, while silicate absorption is seen only in the radio galaxies. These observations are all in agreement with unification schemes that explain both groups as the same class of objects seen under different orientation angles.

astro-ph↗