High-order Balmer Absorption Lines Research Articles

The supergiant optical counterpart of ULX P13 in NGC 7793

AbstractWe have identified the optical counterpart of the ULX source P13 in the nearby spiral galaxy NGC 7793. The object is a V ∼ 20.5 mag star, ten times brighter than any other established counterpart of a ULX in nearby galaxies. Medium resolution optical spectroscopy carried out in 2008 and 2009 with the ESO‐VLT reveals the presence of narrow high order Balmer, He I and Mg II absorption lines indicating a late B‐type supergiant companion star with mass between 10 and 20 M⊙. Stellar Hβ and He II λ 4686 Å emission lines are also seen superposed on the photospheric spectrum. We detect different patterns of radial velocity variations from the emission and absorption lines over a time interval of one month. The velocity of the high order Balmer absorption lines changes by ∼100 km s–1 while the Hβ and He II λ 4686 Å emission components vary by about the same amount but with a different phasing. Assuming that the observed velocity changes trace the motion of the mass‐donor star and of the X‐ray source implies a mass of the accreting black hole in the range of 3 to 100 M⊙ with a most probable value of ∼10 to 20 M⊙. We expect an orbital period in the range of 20 to 40 days based on the low density of the supergiant star. P13 is likely in a short‐lived, and thus rare high X‐ray luminosity evolutionary state associated with the ascension of the donor star onto the supergiant stage (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Kinematics and Principal Component Analysis from IFU Spectroscopy of the Post-Starburst Quasar SDSS J0210–0903

We present 2-D mapping and analysis of the gaseous kinematics of the inner 7″ × 5″ of one of nearest (z = 0.0414) and brightest post-starburst quasars (PSQ) by using spectra obtained with the Integral Field Unit (IFU) of the Gemini Multi-Object Spectrograph on the Gemini North Telescope (Allington-Smith et al. 2002). Such quasars are broad-lined AGNs that also show the Balmer jumps and the high-order Balmer absorption lines from A stars typical of massive post-starburst populations of a few hundred Myrs (Brotherton et al. 2007). From measurements of the emission-line profiles, we constructed two-dimensional maps for the flux distributions, line ratios, radial velocities and gas velocity dispersions for the Hβ and [Oiii] emitting gas, similar to those of previous studies by our group (e.g., Barbosa et al. 2009).

The stellar populations of low-luminosity active galactic nuclei - III. Spatially resolved spectral properties

In a recently completed survey of the stellar population properties of low-ionization nuclear emission-line regions (LINERs) and LINER/H II transition objects (TOs), we have identified a numerous class of galactic nuclei which stand out because of their conspicuous 10 8-9 yr populations, traced by high-order Balmer absorption lines and other stellar indices. These objects are called 'young-TOs', because they all have TO-like emission-line ratios. In this paper we extend this previous work, which concentrated on the nuclear properties, by investigating the radial variations of spectral properties in low-luminosity active galactic nuclei (LLAGNs). Our analysis is based on high signal-to-noise ratio (S/N) long-slit spectra in the 3500-5500 A interval for a sample of 47 galaxies. The data probe distances of typically up to 850 pc from the nucleus with a resolution of ∼100 pc (∼1 arcsec) and S/N ∼30. Stellar population gradients are mapped by the radial profiles of absorption-line equivalent widths and continuum colours along the slit. These variations are further analysed by means of a decomposition of each spectrum in terms of template galaxies representative of very young (≤10 7 yr), intermediate age (10 8-9 yr) and old (10 10 yr) stellar populations. This study reveals that young-TOs also differ from old-TOs and old-LINERs in terms of the spatial distributions of their stellar populations and dust. Specifically, our main findings are as follows. (i) Significant stellar population gradients are found almost exclusively in young-TOs. (ii) The intermediate age population of young-TOs, although heavily concentrated in the nucleus, reaches distances of up to a few hundred pc from the nucleus. Nevertheless, the half width at half-maximum of its brightness profile is more typically 100 pc or less. (iii) Objects with predominantly old stellar populations present spatially homogeneous spectra, be they LINERs or TOs. (iv) Young-TOs have much more dust in their central regions than other LLAGNs. (v) The B-band luminosities of the central ≤1 Gyr population in young-TOs are within an order of magnitude of M B = -15, implying masses of the order of ∼10 7 -10 8 M ○. . This population was 10-100 times more luminous in its formation epoch, at which time young massive stars would have completely outshone any active nucleus, unless the AGN too was brighter in the past.

The Stellar Populations of Low‐Luminosity Active Galactic Nuclei. I. Ground‐based Observations

(Abridge): We present a spectroscopic study of the stellar populations of Low Luminosity AGN (LLAGN). Our main goal is to determine whether the stars who live in the innermost (100 pc-scale) regions of these galaxies are in some way related to the emission line properties, which would imply a link between the stellar population and the ionization mechanism. High signal to noise, ground based long-slit spectra in the 3500--5500 A interval were collected for 60 galaxies.Our main findings are: (1) Few LLAGN have a detectable young (< 10 Myr) starburst component, indicating that very massive stars do not contribute significantly to the optical continuum. In particular, no features due to Wolf-Rayet stars were convincingly detected. (2) High Order Balmer absorption lines of HI (HOBLs), on the other hand, are detected in 40% of LLAGN. These features, which are strongest in 100 Myr--1 Gyr intermediate age stellar populations, are accompanied by diluted metal absorption lines and bluer colors than other objects in the sample. (3) These intermediate age populations are very common (50 %) in LLAGN with relatively weak [OI] emission, but rare (10 %) in LLAGN with stronger [OI]. This is intriguing since LLAGN with weak [OI] have been previously hypothesized to be ``transition objects'' in which both an AGN and young stars contribute to the emission-line excitation. Massive stars, if present, are completely outshone by intermediate age and old stars in the optical. This happens in at least a couple of objects where independent UV spectroscopy detects young starbursts not seen in the optical. (4) Objects with predominantly old stars span the whole range of [OI]/Halpha values, but (5) sources with significant young and/or intermediate age populations are nearly all (90%) weak [OI] emitters.

Nuclear Starburst Activity in the Seyfert 2 Galaxy NGC 2273

We present spectrophotometric results of the Seyfert 2 galaxy NGC 2273. The presence of high-order Balmer absorption lines (H8, H9, H10) and weak equivalent widths of CaII K λ3933, CN λ4200, G-band λ4300 and MgIb λ5173 clearly indicate recent star-forming activity in the nuclear region. Using a simple stellar population synthesis model, we find that for the best fit, the contributions of a power-law featureless continuum, an intermediate-age (∼ 108 yr) and an old (> 109 yr) stellar population to the total light at the reference normalization wavelength are 10.0%, 33.4% and 56.6%, respectively. The existence of recent starburst activity is also consistent with its high far-infrared luminosity (log LFIR/L☉ = 9.9), its infrared color indexes [α(25, 60) = −1.81 and α(60, 100)= −0.79, typical values for Seyfert galaxies with circumnuclear starburst], and its q-value (2.23, ratio of infrared to radio flux, very similar to that of normal spirals and starburst galaxies). Byrd et al. have suggested that NGC 2273 might have interacted with NGC 2273B in less than 109 yr ago, so the starburst activity in this galaxy could have been triggered by tidal interaction, as indicated in recent numerical simulations.

The nuclear starburst activity in the Seyfert 2 galaxy NGC 7679

We present our recent spectrophotometric results of the infrared luminous Seyfert galaxy NGC 7679. We find compelling evidence of the presence of a recent nuclear starburst, revealed by the observations of a) the spectral features of high order Balmer absorption lines, b) the weak equivalent widths for CaIIK $\lambda$3933, CN $\lambda$4200, G-band $\lambda$4300 and MgIb $\lambda$5173, and c) the suggested UV stellar wind resonance lines (N V $\lambda$1240, Si IV $\lambda$1400 and C IV $\lambda$1550) in the IUE spectrum. Using the simple stellar population synthesis model, we find that in the nuclear 2 $\times$ 2 region, the contributions from the old, intermediate and young components are 21.7%, 42.9% and 35.4%, respectively. These nuclear starburst activities might be triggered by the close encounter with NGC 7682, as suggested by recent numerical simulations.

A Spectacular Poststarburst Quasar

We report the discovery of a spectacular "poststarburst quasar" UN J1025-0040 (B = 19; z = 0.634). The optical spectrum is a chimera, displaying the broad Mg II λ2800 emission line and strong blue continuum characteristic of quasars, but is dominated in the red by a large Balmer jump and prominent high-order Balmer absorption lines indicative of a substantial young stellar population at similar redshift. Stellar synthesis population models show that the stellar component is consistent with a 400 Myr old instantaneous starburst with a mass of ≲1011 M☉. A deep, Ks-band image taken in ~05 seeing shows a point source surrounded by asymmetric extended fuzz. Approximately 70% of the light is unresolved, the majority of which is expected to be emitted by the starburst. While starbursts and galaxy interactions have been previously associated with quasars, no quasar ever before has been seen with such an extremely luminous young stellar population.

Discovery of a Radio-loud/Radio-quiet Binary Quasar

We report the discovery of a small-separation quasar pair (z=0.586, O=18.4, 19.2, and a separation of 23) associated with the radio source FIRST J164311.3+315618 (S1400=120 mJy). The spectrum of the brighter quasar (A) has a much stronger narrow emission line spectrum than the other (B), and it also has stronger Balmer lines relative to the continuum. The continuum ratio of the spectra is flat in the blue (λobs<6000 A) at about 2.1 but falls to 1.5 at longer wavelengths. A K' image shows two unresolved sources with a flux ratio of 1.3. The different colors appear to result from the contribution of the host galaxy of B, which is evident from Ca II and high-order Balmer absorption lines that are indicative of a substantial young stellar population. New 3.6 cm VLA observations show that the compact radio source is coincident with quasar A (B is only marginally detected). We rule out the lensing hypothesis because the optical flux ratio is A/B≈1.5-2, while the radio flux ratio is A/B40, and conclude that this system is a binary. Moreover, the radio-loud quasar is a compact, steep spectrum source. FIRST J164311.3+315618A, B is the lowest redshift and smallest separation binary quasar yet identified.

1608+656: A Gravitationally Lensed PostStarburst Radio Galaxy

The gravitational lens system 1608+656 displays four flat-spectrum, pointlike components that are the images of the unresolved core of a double-lobed radio source. The lensing mass is a galaxy at z = 0.630. New spectra of this system enable us to determine a conclusive redshift of 1.394 for the lensed object. The spectra show prominent high-order Balmer absorption lines and Mg II absorption. These lines, and the absence of [O II] emission, indicate that this is a poststarburst or E + A galaxy. It is unique among lensed objects in not being a quasar and among E + A galaxies in having the highest known redshift. Even allowing for lens magnification, the lensed object is a very luminous galaxy, with an absolute magnitude, M(r) = -22.8 mag. The deconvolved infrared image indicates that the galaxy may be slightly resolved. The radio luminosity density of the lobes is L_(1.4) = 5.78 × 10^(25) W Hz^(-1), which puts the source on the boundary between FR I and FR II radio galaxies. Together with the redshift for the lens and a satisfactory mass model, the determination of the lensed object redshift makes this system an excellent candidate for measuring H_0.

Long-Slit Spectroscopy of IC 5135 and NGC 4388

The nucleus of the peculiar Sa galaxy IC 5135 has strong emission lines whose relative intensities resemble those of Seyfert 2 galaxies (Phillips, Charles, and Baldwin 1983). However, the galaxy exhibits relative line intensities such as [O III] λ5007/Hβ = 6.5 and He II λ4686/Hβ = 0.17 that are considerably smaller than typical Seyfert 2 values of 11 and 0.3, respectively (Koski 1978). New, high-resolution spectra (FWHM ≈ 2Å) obtained at Las Campanas Observatory reveal that the Hβ emission-line profile actually consists of a relatively strong, narrow component (FWHM ≈ 250 km s−1) superposed on a much weaker, broad base (FWHM ≈ 1000 km s−1; Fig. 1). A similar two-component profile is evident in [O I] λ6300, whose narrow core probably comes from circumnuclear H II regions that produce little [O III] and He II emission. The strong, high-order Balmer absorption lines are consistent with the presence of a young stellar population in the nucleus.

The massive unseen companion of X Persei - Emission contamination in the Balmer lines

view Abstract Citations (26) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The massive unseen companion of X Persei : emission contamination in the Balmer lines. Penrod, G. D. ; Vogt, S. S. Abstract X Per is the optical counterpart of the pulsating X-ray source 4U 0352 + 30. Although nearly all observations of this system are consistent with a relatively simple model consisting of a normal O93-B0e star with a neutron star companion in a distant orbit, Hutchings et al. (1974) reported large-amplitude radial velocity variations with a 580-day period in the high-order Balmer absorption lines, which, if interpreted as orbital motion, imply the existence of a massive (more than 30 solar mass) unseen compansion, probably a black hole. High-quality Reticon spectra of the high-order Balmer lines have been obtained which show that the 'radial velocity' variations reported by Hutchings et al. are spurious and are caused by asymmetric and variable emission components hiding in the absorption profiles. This result eliminates the necessity for postulating a massive, unseen secondary or tertiary star. All observed aspects of X Per now seem consistent with the Be + neutron star binary scenario. A previously reported 22.4-hr periodicity in the X-ray flux is explained in terms of nonradial g-mode pulsations of the Be star, which modulate the star's wind, and, hence, the accretion rate onto the neutron star. Publication: The Astrophysical Journal Pub Date: December 1985 DOI: 10.1086/163730 Bibcode: 1985ApJ...299..653P Keywords: Astronomical Spectroscopy; B Stars; Balmer Series; Black Holes (Astronomy); Companion Stars; Neutron Stars; X Ray Sources; Radial Velocity; Spectrum Analysis; Stellar Spectra; Astrophysics full text sources ADS | data products SIMBAD (1)