Hyunjin Jeong

The SAURON project – XVI. On the sources of ionization for the gas in elliptical and lenticular galaxies

Following our study on the incidence, morphology and kinematics of the ionised gas in early-type galaxies we now address the question of what is powering the observed nebular

The SAURON project - XIII. SAURON-GALEX study of early-type galaxies: the ultraviolet colour-magnitude relations and Fundamental Planes

We present Galaxy Evolution Explorer (GALEX) far (FUV) and near (NUV) ultraviolet imaging of 34 nearby early-type galaxies from the SAURON representative sample of 48 E/S0 galaxies, all of which have ground-based optical imaging from the MDM Observatory. The surface brightness profiles of nine galaxies (≈ 26 per cent) show regions with blue UV−optical colours sug

The SAURON project – XIX. Optical and near-infrared scaling relations of nearby elliptical, lenticular and Sa galaxies

We present ground-based MDM Observatory V-band and Spitzer/InfraRed Array Camera 3.6-mu m-band photometric observations of the 72 representative galaxies of the SAURON survey. Galaxies in our sample probe the elliptical E, lenticular S0 and spiral Sa populations in the nearby Universe, both in field and cluster environments. We perform aperture photometry to derive homogeneous structural quantities. In combination with the SAURON stellar velocity dispersion measured within an effective radius (sigma(e)), this allows us to explore the location of our galaxies in the colour-magnitude, colour-sigma(e), Kormendy, Faber-Jackson and Fundamental Plane scaling relations. We investigate the dependence of these relations on our recent kinematical classification of early-type galaxies (i.e. slow/fast rotators) and the stellar populations. Slow rotator and fast rotator E/S0 galaxies do not populate distinct locations in the scaling relations, although slow rotators display a smaller intrinsic scatter. We find that Sa galaxies deviate from the colour-magnitude and colour-sigma(e) relations due to the presence of dust, while the E/S0 galaxies define tight relations. Surprisingly, extremely young objects do not display the bluest (V - [3.6]) colours in our sample, as is usually the case in optical colours. This can be understood in the context of the large contribution of thermally pulsing asymptotic giant branch stars to the infrared, even for young populations, resulting in a very tight (V - [3.6])-sigma(e) relation that in turn allows us to define a strong correlation between metallicity and se. Many Sa galaxies appear to follow the Fundamental Plane defined by E/S0 galaxies. Galaxies that appear offset from the relations correspond mostly to objects with extremely young populations, with signs of ongoing, extended star formation. We correct for this effect in the Fundamental Plane, by replacing luminosity with stellar mass using an estimate of the stellar mass-to-light ratio, so that all galaxies are part of a tight, single relation. The new estimated coefficients are consistent in both photometric bands and suggest that differences in stellar populations account for about half of the observed tilt with respect to the virial prediction. After these corrections, the slow rotator family shows almost no intrinsic scatter around the best-fitting Fundamental Plane. The use of a velocity dispersion within a small aperture (e. g. R-e/8) in the Fundamental Plane results in an increase of around 15 per cent in the intrinsic scatter and an average 10 per cent decrease in the tilt away from the virial relation.

The SAURON project

Using far-ultraviolet (FUV) and near-ultraviolet (NUV) photometry from guest investigator programmes on the Galaxy Evolution Explorer (GALEX) satellite, optical photometry from the MDM Observatory and optical integral-field spectroscopy from SAURON, we explore the UV–line-strength relations of the 48 nearby early-type galaxies in the SAURON sample. Identical apertures are used for all quantities, avoiding aperture mismatch. We show that galaxies with purely old stellar populations show well-defined correlations of the integrated FUV −V and FUV − NUV colours with the integrated Mg b and Hβ absorption line-strength indices, strongest for FUV − NUV. Correlations with the NUV −V colour, Fe5015 index and stellar velocity dispersion σ are much weaker. These correlations put stringent constraints on the origin of the UV-upturn phenomenon in early-type galaxies and highlight its dependence on age and metallicity. In particular, despite recent debate, we recover the negative correlation between FUV −V colour and Mg line strength originally publicized by Burstein et al., which we refer to as the ‘Burstein relation’, suggesting a positive dependence of the UV upturn on metallicity. We argue that the scatter in the correlations is real and present mild evidence that a strong UV excess is preferentially present in slow-rotating galaxies. We also demonstrate that most outliers in the correlations are galaxies with current or recent star formation, some at very low levels. We believe that this sensitivity to weak star formation, afforded by the deep and varied data available for the SAURON sample, explains why our results are occasionally at odds with other recent but shallower surveys. This is supported by the analysis of a large, carefully crafted sample of more distant early-type galaxies from the Sloan Digital Sky Survey (SDSS), more easily comparable with current and future large surveys.

Molecular gas and star formation in the red-sequence counter-rotating disc galaxy NGC 4550

We present observations of the CO(1-0) emission in the central 750 pc (10 arcsec) of the counter-rotating disc galaxy NGC 4550, obtained at the Institut de Radioastronomie Millimetrique (IRAM) Plateau de Bure Interferometer. Very little molecular gas is detected, only 1 ×10 7 M ⊙ , and its distribution is lopsided, with twice as much molecular gas observed at positive relative velocities than at negative relative velocities. The velocity gradient in the CO(1-0) emission shows that the molecular gas rotates like the thicker of the two stellar discs, which is an unexpected alignment of rotations if the thinner disc was formed by a major gas accretion event. However, a simulation shows that the gas rotating like the thicker disc naturally results from the coplanar merger of two counter-rotating disc galaxies, demonstrating the feasibility of this scenario for the formation of NGC 4550. We investigate various star formation tracers to determine whether the molecular gas in NGC 4550 is currently forming stars. Ultraviolet (UV) imaging data and optical absorption line strengths both suggest a recent star formation episode; the best-fitting two-population model to the UV-optical colours yields a mass of young stars of 5.9×10 7 M ⊙ with an age of 280 Myr. The best information on the current star formation rate is a far-infrared-based upper limit of only 0.02 M ⊙ yr -1 . We are thus witnessing NGC 4550 either in a dip within a bursty star formation period or during a more continuous low-level star formation episode.

The SAURON project - XVIII : The integrated UV-line-strength relations of early-type galaxies

Using far-ultraviolet (FUV) and near-ultraviolet (NUV) photometry from guest investigator programmes on the Galaxy Evolution Explorer (GALEX) satellite, optical photometry from the MDM Observatory and optical integral-field spectroscopy from SAURON, we explore the UV–line-strength relations of the 48 nearby early-type galaxies in the SAURON sample. Identical apertures are used for all quantities, avoiding aperture mismatch. We show that galaxies with purely old stellar populations show well-defined correlations of the integrated FUV −V and FUV − NUV colours with the integrated Mg b and Hβ absorption line-strength indices, strongest for FUV − NUV. Correlations with the NUV −V colour, Fe5015 index and stellar velocity dispersion σ are much weaker. These correlations put stringent constraints on the origin of the UV-upturn phenomenon in early-type galaxies and highlight its dependence on age and metallicity. In particular, despite recent debate, we recover the negative correlation between FUV −V colour and Mg line strength originally publicized by Burstein et al., which we refer to as the ‘Burstein relation’, suggesting a positive dependence of the UV upturn on metallicity. We argue that the scatter in the correlations is real and present mild evidence that a strong UV excess is preferentially present in slow-rotating galaxies. We also demonstrate that most outliers in the correlations are galaxies with current or recent star formation, some at very low levels. We believe that this sensitivity to weak star formation, afforded by the deep and varied data available for the SAURON sample, explains why our results are occasionally at odds with other recent but shallower surveys. This is supported by the analysis of a large, carefully crafted sample of more distant early-type galaxies from the Sloan Digital Sky Survey (SDSS), more easily comparable with current and future large surveys.

Henoch-Schönlein purpura nephritis with nephrotic-range proteinuria: histological regression possibly associated with cyclosporin A and steroid treatment.

Objective: To clarify the therapeutic role of cyclosporin A (CyA) for patients with Henoch–Schönlein purpura nephritis (HSPN) showing nephrotic‐range proteinuria. Methods: The clinical and histological findings of eight children (7.7±3.8 years), who were treated with CyA and prednisolone, were evaluated retrospectively. All underwent a renal biopsy before therapy, and six of the eight patients received a follow‐up biopsy after therapy. Results: The histological grade of the International Study of Kidney Disease in Children (ISKDC) was improved in all six patients who received a follow‐up biopsy (pre‐therapy, four grade IIIa and two grade IIIb; post‐therapy, one grade I and five grade II) and it was statistically significant (p = 0.031). The activity index was significantly decreased after therapy (8.3±1.6 vs. 3.5±1.5, p = 0.031), and the chronicity index (0.5±0.5 vs. 0.7±1.0) and tubulointerstitial (TI) scores (1.5±1.3 vs. 0.8±1.6) did not change. There was a reduction in proteinuria from 3.2±2.3 to 0.1±0.1 g/m2/day (p = 0.008) and renal function remained normal in all patients after therapy. However, one patient showed CyA‐induced nephrotoxicity at a second biopsy. After an average follow‐up period of 3.8 years, six patients showed normal urine and renal function, and two showed minor urinary abnormalities. Conclusion: This study suggests that CyA therapy is effective in reducing proteinuria, which is a known risk factor for the development of renal insufficiency in HSPN and may regress the renal pathology in patients with nephrotic‐range proteinuria.

The SAMI Galaxy Survey: revisiting galaxy classification through high-order stellar kinematics

Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h_3 (~skewness) and h_4 (~kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using two-dimensional integral field data from the SAMI Galaxy Survey. Proxies for the spin parameter (λ_(R_e)) and ellipticity (e_e) are used to separate fast and slow rotators; there exists a good correspondence to regular and non-regular rotators, respectively, as also seen in earlier studies. We confirm that regular rotators show a strong h_3 versus V/σ anti-correlation, whereas quasi-regular and non-regular rotators show a more vertical relation in h_3 and V/σ. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h_3 versus V/σ signatures. Within the SAMI Galaxy Survey, we identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow rotators, whereas Classes 2–5 correspond to fast rotators. We find that galaxies with similar λ_(R_e) - e_e values can show distinctly different h_3 - V/σ signatures. Class 5 objects are previously unidentified fast rotators that show a weak h_3 versus V/σ anti-correlation. From simulations, these objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h_3 versus V/σ as evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.

Role of mesangial fibrinogen deposition in the pathogenesis of crescentic Henoch-Schönlein nephritis in children

Aims: To clarify the role of mesangial fibrinogen deposition in crescentic Henoch-Schönlein nephritis (HSN). Methods: A retrospective analysis of 21 children with HSN treated with immunosuppressants. Serial renal biopsies were performed before and after treatment. They were divided into two groups according to the immunofluorescent course of fibrinogen deposition: group I (n = 9), no or decreased deposition; group II (n = 12), persistent or increased deposition. Results: There were no differences between the two groups in renal manifestations or laboratory and histological findings at presentation. However, the activity index after immunosuppressive treatment was significantly decreased in group I (mean, 7.9 (SEM, 0.7) v 2.9 (0.4); p = 0.008) and unchanged in group II (mean, 6.8 (SEM, 0.3) v 6.0 (2.1)). The chronicity index was unchanged in group I, but increased in group II (mean, 0.8 (SEM, 0.3) v 1.8 (0.3); p = 0.02). Univariate analysis revealed that the only factor significantly related to persistent or increased fibrinogen deposition was age more than 9 years (p = 0.03). Furthermore, the intensity of fibrinogen deposition at the second biopsy correlated positively with the age at onset (R2 = 0.306; p = 0.009) and changes in the percentage of crescents (post-treatment crescents (%) minus pretreatment crescents (%)) correlated positively with the intensity of fibrinogen deposition at the second biopsy (R2 = 0.193; p = 0.046). Conclusions: This study indicates that fibrinogen deposition has an important role to play in renal injury of crescentic HSN and reflects persistent severe histological activity.

Tidal Dwarf Galaxies around a Post-Merger Galaxy, NGC 4922

One possible channel for the formation of dwarf galaxies involves birth in the tidal tails of interacting galaxies. We report the detection of a bright UV tidal tail and several young tidal dwarf galaxy (TDG) candidates in the post-merger galaxy NGC 4922 in the Coma cluster. Based on a two-component population model (combining young and old stellar populations), we find that the light of tidal tail predominantly comes from young stars (a few Myr old). The Galaxy Evolution Explorer ultraviolet data played a critical role in the parameter (age and mass) estimation. Our stellar mass estimates of the TDG candidates are ~10^(6–7) M_☉, typical for dwarf galaxies.