Vertical Disk Structure in HL Tauri

We present the JHK-band high-resolution polarimetric images of the low-mass proto-stellar object HL Tau using the adaptive opticsequipped CIAO instrument on the Subaru telescope. Our polarization images show a butterfly-shaped polarization disk with an ∼0. 9× 3. 0 extension. In the nebula, where polarization vectors are centro-symmetrically aligned, the polarization is as high as P J ∼ 30%, P H ∼ 42%, and P K ∼ 55%. On the other hand, low polarizations of P < 3% in the J, H, and K bands and a low color excess ratio of E J−H /E H−K = 1.1 compared to the standard cloud value of 1.75 are detected towards the central star. We estimated the upper limit of the grain sizes a max to be 0.4 μm in the nebula and > ∼ 0.7 μm in the line of sight towards the central star. Our high-resolution polarimetric data, which spatially resolves the polarization disk, provides us with important information about grain growth in the region close to the central star.

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“…These appearances are consistent with the previously reported images (e.g. Beckwith & Birk 1995;Stapelfeldt et al 1995;Close et al 1997).…”

Section: Observationssupporting

confidence: 93%

Near-infrared multiwavelength imaging polarimetry of the low-mass proto-stellar object HL Tauri

Murakawa¹,

Oya

Pyo

et al. 2008

A&A

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“…Previous estimates of the extinction toward HL Tau suggest A v ~ 22-30 magnitudes (Monin et al 1989;Beckwith & Birk 1995;Stapelfeldt et al 1995, Close et al 1997. The column density from our CO data implies substantially larger values of A V for the same line of sight.…”

Section: Hl Tau's Anomalous Gas/dust Ratiomentioning

confidence: 92%

CO Line Emission and Absorption from the HL Tauri Disk—Where Is All the Dust?

Brittain¹,

Rettig²,

Simon³

et al. 2005

ApJ

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We present high-resolution infrared spectra of HL Tau, a heavily embedded young star. The spectra exhibit broad emission lines of 12 CO gas phase molecules as well as narrow absorption lines of 12 CO, 13 CO, and C 18 O. The broad emission lines of vibrationally-excited 12 CO are dominated by the hot (T~1500 K) inner-disk. The narrow absorption lines of CO are found to originate from the circumstellar gas at a temperature of ~100 K. The 12 CO column density for this cooler material (7.5 ± 0.2 x 10 18 cm -2 ) indicates a large column of absorbing gas along the line of sight. In dense interstellar clouds, this column density of CO gas is associated with A V ~ 52 magnitudes. However, the extinction toward this source (A V~2 3) suggests that there is less dust along the line of sight than inferred from the CO absorption data. We discuss three possibilities for the apparent paucity of dust along the line of sight through the flared disk: 1) the dust extinction has been underestimated due to differences in circumstellar grain properties, such as grain agglomeration; 2) the effect of scattering has been underestimated and the actual extinction is much higher; or (3) the line of sight through the disk is probing a gasrich, dust-depleted region, possibly due to the stratification of gas and dust in a preplanetary disk. Through the analysis of hot ro-vibrational 12 CO line emission, we place strong constraints on grain growth and thermal infrared dust opacity, and separately constrain the enhancement of carbon bearing species in the neighboring molecular envelope. The physical stratification of gas and dust in the HL Tau disk remains a viable explanation for the anomalous gas to dust ratio seen in this system. The measured radial velocity dispersion in the outer disk is consistent with the thermal linewidths of the absorption lines, leaving only a small turbulent component to provide gas-dust mixing.Subject headings: circumstellar matter ---stars: formation ---stars: individual (HL Tau) stars: pre-main-sequence ---planetary systems: formation---planetary systems: protoplanetary disks

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“…In the evolutionary sequence, it is in a transition phase between class I and class II. There is strong extinction towards the central source (A V > 22 mag, Stapelfeldt et al 1995), although the star is detected in the near-infrared (Weintraub et al 1995;Beckwith & Birk 1995). The morphology of the optical and NIR reflection nebula as well as the flat spectral energy distribution of HL Tau can be explained by scattering and thermal emission from an infalling, dusty protostellar envelope typical of Taurus class I sources (Calvet et al 1994).…”

Section: The Class I/ii Transition Protostar Hl Taumentioning

confidence: 97%

Searching for coronal radio emission from protostars using very-long-baseline interferometry

Forbrich

Massi

Ros

et al. 2007

A&A

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Aims. In order to directly study the role of magnetic fields in the immediate vicinity of protostars, we use Very-Long-Baseline Interferometry (VLBI), aiming at the detection of non-thermal centimetric radio emission. This is technically the only possibility to study coronal emission at sub-AU resolution. Methods. We performed VLBI observations of the four nearby protostars HL Tau, LDN 1551 IRS5, EC 95, and YLW 15 in order to look for compact non-thermal centimetric radio emission. For maximum sensitivity, we used the High Sensitivity Array (HSA) where possible, involving the Very Long Baseline Array (VLBA), the phased Very Large Array (VLA), as well as the Arecibo, Green Bank, and Effelsberg radio telescopes. Results. While all four protostars were detected in VLA-only data, only one source (YLW 15 VLA 2) was detected in the VLBI data. The possibility of non-detections due to free-free absorption, possibly depending on source geometry, is considered.

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Vertical Disk Structure in HL Tauri

Cited by 15 publications

References 29 publications

Near-infrared multiwavelength imaging polarimetry of the low-mass proto-stellar object HL Tauri

Near-infrared multiwavelength imaging polarimetry of the low-mass proto-stellar object HL Tauri

CO Line Emission and Absorption from the HL Tauri Disk—Where Is All the Dust?

Searching for coronal radio emission from protostars using very-long-baseline interferometry

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