ISM/Star formation (12)

High J Lines of CO as Tracers of Low Velocity Turbulent Shocks in Molecular Clouds

Proposal ID: GT2_apon_1

Principal Investigator: Andy Pon

Time: 1.3 hours priority 1

Category: Interstellar Medium/HII regions


Molecular clouds contain supersonic turbulence. Simulations of supersonic turbulence, which include magnetic fields, show that the turbulent energy decays rapidly via shocks. Although these simulations do not explicitly follow how the energy escapes a molecular cloud, shock heated gas will cool through line radiation, thereby altering the resulting molecular spectrum of the cloud. Thus, observations of the dominant molecular coolants provide observable tracers of the turbulent energy dissipation.

We have computed models of low velocity, MHD shocks to determine which molecular species and transitions dominate the cooling and radiative energy release associated with shock cooling. By combining these models with an estimate for the turbulent energy dissipation rate from molecular clouds, we predict the strengths of these shock tracers. We find that the majority of the turbulent energy dissipated is emitted via CO rotational transitions. However, the observed low J transitions from CO in these clouds are dominated by emission from the surface layer PDR and the ambient, cool CO located throughout the cloud. The shock signature is only separable at the higher rotational transitions, J = 5-4 and up, where the emission from shock heated gas becomes dominant. The shock emission at these higher transitions is relatively weak, as these transitions are already past the emission peak of the CO ladder. Thus, to detect this unique turbulent energy dissipation signature, we require Herschel's exceptional sensitivity.

We propose to use HIFI to observe the CO J = 5-4 and 6-5 transitions towards a nearby low mass star forming region, Perseus B1-E, to verify whether shocked gas is actually present in the region. By observing multiple lines, we can determine both the temperature of the shocked gas and the characteristic shock strength. We will therefore be able to observationally constrain the turbulent energy dissipation rate in Perseus B1-E and compare this value against the predictions of supersonic turbulence decay.

Probing the physical conditions of pre-stellar cores on the verge of collapse

Proposal ID: GT2_astutz_2

Principal Investigator: Amelia Stutz

Time: 8.1 hours priority 1

Category: Star Formation/Young Stellar Objects


Low-mass molecular cloud cores are the birthplace of solar-type stars. Therefore, a thorough understanding of star formation requires detailed knowledge of core properties. Submm/mm observations have identified a class of very cold "pre-stellar" cores on the brink of collapse. Isolated cores, which have a relatively simple structure, are ideal laboratories for studying the star formation process; they can be directly compared with simple theoretical predictions, such as MHD simulations of single cores. Although the chemical and dynamical state of these cores has been well characterized by molecular line observations, we still lack a comprehensive understanding of two fundamental physical parameters: temperature and density. The temperature and density structure regulate the dynamical state of the objects, including any possibility for subsequent fragmentation. For the globule CB 244 we demonstrated that Herschel has the unique capability to provide this information. Due to their short free fall times (of order 10^5 years), pre-stellar cores are rare objects; therefore, we carefully target two representative well-studied pre-stellar cores. Molecular line profiles for these objects show clear signatures of infall motions indicating that they are birthplaces of new stars. The low dust temperatures of these sources (5-15 K) imply that the bulk of the emission will emerge at FIR wavelengths. We therefore propose to observe the targeted objects with PACS and SPIRE. Together with near-infrared extinction maps and submillimetre continuum data, we will be able to reconstruct the dust temperature and density maps, breaking the degeneracy with dust opacity properties. In order to disentangle the effects of dust temperature, density, and opacity, fluxes from both sides of the SED peak are required: Herschel is the only mission which can provide these data with the required sensitivity.

The Carbon Budget and Formation Signatures of Molecular Clouds

Proposal ID: GT2_hbeuther_3

Principal Investigator: Henrik Beuther

Time: 4.7 hours priority 1

Category: Interstellar Medium/HII regions


The interstellar medium (ISM) is mainly comprised of ionized, neutral atomic and molecular gas. One of the most important constituents of these phases is carbon in its ionized/neutral/molecular form (C^+, C^0 and CO). However, a coherent analysis of the different phases at adequate spatial resolution (Jeans length ~0.2pc) is lacking. We therefore want to re-evaluate the ISM carbon budget via observing primarily C^+ at 1.9THz, C^0 (at 492GHz), and CO(2-1) with Herschel, APEX and the IRAM 30m at high spatial resolution (11''-13'') for several infrared dark clouds (IRDCs). This proposal is a guaranteed time pilot study for the line of ionized carbon [CII] toward one IRDC that hosts several embedded protostars. We will follow that up in the future with an open time Herschel proposal as well as SOFIA observations. With the combined data of the different carbon phases we can address: (a) How do the relative abundances change with evolutionary stage? (b) Are the different phases mainly excited by internal or external radiation sources? (c) How important are the phase changes for the carbon cooling budget of the ISM? (d) Can we identify cloud formation signatures (e.g., turbulent flows)?

Herschel spectroscopy for very young star-forming cores: excitation, outflows, and dust emissivity

Proposal ID: GT2_hlinz_1

Principal Investigator: Hendrik Linz

Time: 8.0 hours priority 1

Category: Star Formation/Young Stellar Objects


The properties of very young star-forming cores are difficult to trace. Many of their physical parameters still need to be refined observationally, before a meaningful modelling can advance. The Herschel satellite provides access to the wavelength regime where the bulk of emission arises for such objects. We plan to employ the two versatile spectrographs SPIRE-FTS and PACS-Spec in order to scrutinise eleven very young protostars comprising a larger range of masses and luminosities. The selected objects have been revealed as promisinging targets within our Herschel GT project EPoS. Our goals are three-fold: (1) We want to recover emission from molecular species like CO and HCO+ with SPIRE-FTS, which in combination with ground-based data enables an excitation analysis and constraints for line transfer and structure modelling. (2) We want to reveal the slope of the sub-mm continuum emission with FTS low-res spectra, which gives us a handle on the related dust emissivities. This is crucial to lift the degeneracy between column density, temperature, and dust emissivity, which usually renders an interpretation of sub-mm continuum maps ambiguous. (3) With the PACS spectroscopy for a sub-sample of two objects we want to trace the most important cooling lines of oxygen, carbon, and water to assess the thermal budget for these object stages. Of special importance is the measurement of the [OI] 63.2 micron line strength. This line gives a more direct access to the true outflow rate than common CO observations and is thus an important tool to characterise our targets which all are known to drive outflows.

The evolution of Herbig Ae/Be systems: constraining the gas and dust chemistry with herschel spectroscopy.

Proposal ID: GT2_jbouwman_3

Principal Investigator: Jeroen Bouwman

Time: 3.9 hours priority 1

Category: Circumstellar/Debris disks


We propose to PACS and SPIRE spectrographic observations. The observational aim of this proposal is to characterize the emission line spectrum and continuum SED two HAe stars (HD179218 and HD50138) with the SPIRE spectrograph, and to obtain deep, high spectral sampling PACS spectra on 4 selected H2O and CH+ lines.

Unveiling the embedded protostellar population of the Norma cloud

Proposal ID: GT2_mnielboc_1

Principal Investigator: Markus Nielbock

Time: 2.8 hours priority 1

Category: Star Formation/Young Stellar Objects


Dark clouds are condensations of the ISM that are detected as silhouettes against a bright background and are known to be the cradles of forming stars. With this proposal, we aim at observing the low-mass filamentary dark cloud Sandqvist 187/188, also known as the Norma cloud. It hosts a number of low-mass protostellar objects, among which is a FU Ori star (V346 Nor). 1.2 mm continuum observations resulted in detecting 6 embedded sources that appear to be protostellar objects at different evolutionary stages. However additional data, especially at far-IR wavelengths, that are crucial to derive basic physical properties like temperature, luminosity, density and mass were insufficient so far, both in sensitivity and spatial resolution, to construct meaningful source SEDs. In addition, the global properties of the Norma cloud are also not well known. Current estimates of its density and mass are mainly based on millimetre continuum observations assuming a typical and uniform temperature. Therefore, we want to observe the star forming sites in this cloud with PACS and SPIRE imaging. The unique combination of sensitivity and spatial resolution at far-IR wavelengths provided by the Herschel Space Observatory and its instruments will be the key for determining the still badly constrained properties we are eager to obtain. With the proposed observations we want to i) fill the gaps in the SEDs of the embedded objects, ii) constrain their basic properties, iii) derive their evolutionary stage, and iv) construct a census of the star formation activity in the Norma cloud. In addition, we want to investigate the properties of the ISM surrounding these objects. In particular, we are interested in the temperature and density profiles of the dust around the embedded sources that we reconstruct from the sensitive mapping with PACS and SPIRE and subsequent SED modelling.

Tracing the evolution of the interstellar medium from molecular clouds to stars

Proposal ID: GT2_mpestalo_3

Principal Investigator: Michele Pestalozzi

Time: 39.9 hours priority 1

Category: Interstellar Medium/HII regions


The aim of this proposal is to study how the interstellar medium (ISM) changes due to the process of star formation. To do this we intend to perform a spectral survey with PACS and HIFI, scanning along gradients of increasing temperature, density and star formation activity e.g. from the edge of a star forming region to its centre, making sure to include regions of different levels of star formation activity and different clump/core density.

In this way we will be able to directly relate the changes in the ISM to star formation activity. This proposal is complementary to a GT1 proposal ongoing on the same regions with the SPIRE FTS.

Completion of the Gould Belt and HOBYS surveys

Proposal ID: GT2_pandre_5

Principal Investigator: Philippe André

Time: 16.4 hours priority 1

Category: Star Formation/Young Stellar Objects


As demonstrated by the Herschel first highlights, both the Gould Belt and the HOBYS survey have been extremely successful. While the quality of the corresponding Herschel data is generally excellent, we have identified a few coverage or saturation problems which we intend to fix using the additional observations proposed in the present application. These observations will increase the completeness and legacy value of both surveys. We also propose a small extension to the Gould Belt parallel-mode survey of the Taurus complex in order to cover an area which shows faint 'striations' in CO observations. Combined with the existing Taurus data, the proposed extension will allow us to study, within the same cloud, the properties of the whole spectrum of filamentary structures from faint, non-star forming striations to dense star-forming filaments. Likewise, we propose to slightly extend our parallel-mode survey of the Cygnus X region, the most massive and most active star-forming complex targeted by the HOBYS key project, in order to improve the completeness of our census of high-mass protostars/prestellar cores in this important target cloud.

A complete water map of the rho Ophiuchi cloud core A

Proposal ID: GT2_rliseau_1

Principal Investigator: René Liseau

Time: 10.7 hours priority 1

Category: Interstellar Medium/HII regions


Within only a few arcminutes, the nearby rho Oph A cloud core harbours distinctly different physical regions, i.e. gravitationally unstable dense cores, a highly collimated bipolar outflow from a class 0 protostar and photon dominated regions (PDRs) in the cloud surface layers. These regions are also spatially well separated and offer the opportunity to study in great detail the different chemistries at work, i.e. grain surface reactions, shock chemistry and UV-controlled photochemistry, all on the relevant physical scales (< 1e16cm). The different chemistries, in turn, give rise to variations in elemental and molecular abundances, which control the energy balance of the source regions and provide feedback onto the chemistry. Although particular in some respects (detecatable amounts of O2 and H2O2), rho Oph A offers the opportunity to obtain v ital general information regarding the physics and chemistry of star forming regions. We propose the extensions of our water map to include all source regions, most of which were previously not covered, as the currently available map is limited to the outflow. Simultaneously with the two ground state lines of ortho-water at 557 GHz and 1669 GHz, we also obtain the spatial distribution of the ground state line of ammonia and of a higher excitation H2O line, respectively, with HIFI. In addition, to address the still enigmatic oxygen chemistry, we propose a limited map with PACS of the elemental oxygen fine structure lines at 63 and 145 micron. The total observing time amount to 10.7 hours, which is an inexpensive investment for such a valuable Herschel legacy as the proposed program.

A detailed study of the IRAS23385+6053 star forming region

Proposal ID: GT2_smolinar_6

Principal Investigator: Sergio Molinari

Time: 4.6 hours priority 1

Category: Star Formation/Young Stellar Objects


We propose to use the three instrument on board Herschel to carry out a comprehensice study of the star forming region IRAS23385+6053. The region is a well-known template to host an intermediate-high mass young stellar object possibly on the verge of reaching the ZAMS. This massive YSO, detected as a strong peak in the millimeter but unrevealed below 20um, is surrounded by a population of lower mass objects of both intermediate and low mass in different evolutionary stages, and offer ideal conditions to map the star formation history in a typical region. We will determine accurate Spectral Energy Distributions and luminosities for all the compact objects, and will also ascertain if the region is at the crossroads of intense filamentary structure. Spectral maps with PACS will be obtained in [OI] and [CII], and together with other tracers from the SPIRE FTS spectral range we will be in the ideal conditions to obtain a fairly comprehensive and definitive view of the FUV irradiation conditions in the region. This will provide definitive conclusions regarding the evolutionary stage of the different YOSs in the region, enabling to draw a plausible star formation history.

Carbon isotopes in PDRs

Proposal ID: GT2_vossenko_5

Principal Investigator: Volker Ossenkopf

Time: 10.5 hours priority 1

Category: Interstellar Medium/HII regions


We propose to perform deep integrations for a significant detection of the 13CII and 13CI hyperfine transitions towards five PDRs where previous observations showed marginal, inconsistent or particularly puzzling results. These included anomalous hyperfine ratios and strong variations of the fractionation within one source. The observations will measure the absolute C+ fractionation, they will allow to distinguish the effects of isotope-selective photodissociation and chemical fractionation, and constrain the total isotopic ratio of 13C to 12C.

Multiepoch observations of IC 348: Using Far−Infrared Variability to Constrain the Dust Structure in Young Stellar Objects

Proposal ID: GT2_zbalog_2

Principal Investigator: Zoltan Balog

Time: 4.4 hours priority 1

Category: Star Formation/Young Stellar Objects


There is growing evidence that the star formation process is in fact highly dynamic, on timescales from days to centuries. The temporal variability is a new and powerful diagnostic tool to study Young Stellar Objects (YSOs). Depending on the time−scale of the variability in the mid− and far−infrared we can learn about different physical mechanisms shaping their structure and dynamics. Here we propose to extend our near− and mid−infrared study of variable YSOs in the young open cluster IC 348 to the far−infrared (70 and 160 micron) using Herschel/PACS. We will constrain the frequency of far−infrared variability and compare the observed time−dependent behavior with protostellar and disk models to understand its origin. Possible mechanisms include fluctuations in the accretion luminosity, or echoes of inner disk structural changes projected onto the infalling envelope or flared outer disk surface. Our sample in IC348 covers a large part of the evolutionary sequence of YSOs from class I sources to transitional disks. The cadence of the requested observations allow us to study variations on time scales from days to months that could be extended to several years using our Spitzer/MIPS data.

Stars (12)

Mapping the distribution of the crystalline silicate forsterite in the Saturn Nebula (NGC 7009)

Proposal ID: GT2_bdevries_3

Principal Investigator: Ben de Vries

Time: 2.1 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


We propose to observe a 3x3 oversampled map of the Planetary Nebula NGC 7009. The wavelength of the observation is centered on the 69micron band of crystalline silicate forsterite. This observation will strengthen the results obtained for the PN NGC 6543 (GT1_bdevries_1, PI: B.L. de Vries). For NGC 6543 we have already seen that the forsterite is confined to the inner part of the outflow, therefor linked to the denser last mass-loss phase. NGC 7009 is similar to NGC 6543 in size and age. Combining the observations of NGC 7009 with NGC 6543 will help to further investigate the dust-formation in the circumstellar environment of evolved stars and look at the link with mass-loss and possibly binarity. The total observing time is 2.1h

Unraveling the unexpected wind deceleration in the envelopes around evolved stars

Proposal ID: GT2_ldecin_3

Principal Investigator: Leen Decin

Time: 9.9 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


At the end of their lives, low and intermediate mass stars lose a significant fraction of their mass via a copious mass loss through cool, low-velocity winds (v ~ 10 km/s). After several decades of study, the exact mechanisms triggering this mass loss are still not understood in all detail, but it is generally accepted that pulsations and dust formation play a crucial role. Using these two ingredients, the wind acceleration in the envelope surrounding the stars can be predicted. Herschel/HIFI has the unique capability to study the line profiles of many molecules excited in the circumstellar envelopes, hence enabling us to assess the wind velocity profile in evolved stars. While the HIFI data indeed show for some targets an acceleration of the wind, the widths of the lines in 2 oxygen-rich evolved stars are larger for the high-excitation lines compared to the low-excitation ones, suggesting a deceleration of the wind. This wind profile is completely unexpected, and can currently not be explained. However, the current dataset at hand is too scarce and not well sampled in terms of excitation energy levels. We therefore request Herschel/HIFI observing time to gather a series of SiO rotational lines in both the ground and first vibrational state to deduce with high accuracy the wind acceleration/deceleration in two oxygen-rich evolved stars. This will enable us to clarify the role of dust formation and pulsations in the onset of the stellar wind around low and intermediate mass stars.

Cold dust in the ejecta of SN 1987A

Proposal ID: GT2_mbaes_3

Principal Investigator: Maarten Baes

Time: 2.9 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


The discovery of z>6 galaxies containing very large quantities of dust leaves little room for dust enrichment by low and intermediate mass stars. A potential alternative source is dust formation in the ejecta of core collapse supernovae, where 0.1 to 1 Msun of dust could form according to theoretical scenarios. Studies at mid-infrared wavelengths of type II core-collapse supernovae in nearby galaxies have to date not confirmed these predictions. Recently, we have detected a source coincident with SN 1987A with PACS and SPIRE at 100, 160, 250 and 350 µm as part of the HERITAGE key program. Fits to the spectral energy distribution yield a dust mass of 0.5 to 1 Msun, within the limits set by the predicted abundances for heavy elements in the ejecta.

We propose detailed follow-up scan-map observations of a 10x10 arcmin field round SN 1987A. These observations will yield higher angular resolution and higher S/N detections of SN 1987A at wavelengths between 70 and 500 µm, which will enable us to make the most accurate SED and ejecta dust mass achievable with Herschel. In particular, these observations will yield the 500 µm flux density (for which we only have an upper limit from the HERITAGE observations) and a crucial 70 µm flux density, which will help to bridge the spectral gap between the mid-infrared peak from the shocked ring around SN 1987A and the far-infrared emission peak from the cold ejecta dust. Finally, comparison between the HERITAGE observations and the proposed follow-up observations at 100, 160 and 250 µm will enable us to detect any evolution in the flux densities from the remnant over a two-year time span. Such repeat observations are necessary to determine whether embedded radioactivity or the ambient interstellar radiation field is the dominant heating source of the dust.

MESS SPIRE-FTS spectroscopy of evolved sources having MESS PACS spectroscopy

Proposal ID: GT2_mbarlow_1

Principal Investigator: Michael Barlow

Time: 15.0 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


The SPIRE collaborators in the MESS (Mass loss from Evolved StarS) GTKP wish to allocate 15 hours of SPIRE Guaranteed Time to enable the acquisition of complementary 194-670um SPIRE FTS spectroscopy of 19 MESS evolved star targets for which PACS SED-mode 57-210um spectroscopy has already been obtained or scheduled. The original allocation of 80 hrs of SPIRE GT to the MESS programme for SPIRE imaging photometry and spectroscopy of evolved star targets, was sufficient only for FTS spectra to be obtained for 23 of the 51 evolved stars for which PACS Guaranteed Time was being used to acquire PACS SED-mode spectroscopy. The current application aims to remedy this situation, by obtaining complementary FTS spectra for most of the remaining targets that (a) have MESS PACS spectroscopy; (b) are bright enough for good S/N spectroscopy to be acquired at SPIRE wavelengths; (c) are not being observed with the FTS by any other Herschel programme.

Dust mass-loss on the RGB: reaching the limits

Proposal ID: GT2_mgroen01_6

Principal Investigator: Martin Groenewegen

Time: 7.5 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


Stellar mass loss is the main characteristic of the late stages of stellar evolution. Almost all stars with masses between 1 and 8 solar masses pass through the Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB). Mass loss on the AGB has been relatively well studied and is the main subject of the MESS (Mass-loss of Evolved StarS) Herschel GTKP that the proposers are involved in. However, it is known from Horizontal Branch morphology and other indicators that about 0.2 solar mass is lost in the RGB, and for stars of low initial mass this dominates the mass lost on the AGB. Relatively little is known about the mass loss process on the RGB. It has been established that mass loss in the form of dust is present at the tip of the RGB, but little is known about the exact conditions under which dusty winds develop near the tip of the RGB, mainly because the expected excess is small. On the AGB the mass loss is strongly related to pulsation, and also the stars at the tip of the RGB that show the largest mass-loss rates show pulsation.

In this study we propose to obtain PACS and SPIRE photometry for a very well defined sample of 12 field RGB stars with accurate Hipparcos parallaxes for which ground-based optical and NIR photometry are available. Ground-based high resolution optical spectra that we will obtain and the optical+NIR photometry will very precisely fix the flux from the central star. We show that we will be able to detect the FIR excess if it is present, thanks to the accurate absolute flux calibration of PACS and SPIRE. We will be able to detect total mass-loss rates as low as 1.e-9 solar masses/year. This would push the existing limit on accurate mass-loss rate determination of RGB stars by an order of magnitude, and will allow us to say how prominent dust mass-loss is on the RGB and its dependence on stellar parameters, thereby potentially improving on Reimers law like recipes in standard use in stellar evolutionary models.

Spectroscopy on the bow-shock of CW Leo

Proposal ID: GT2_mgroen01_7

Principal Investigator: Martin Groenewegen

Time: 4.0 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


Herschel and Galex imaging have revealed the presence of a bowshock around CW Leo located at about 8 arcmin from the central star.

The Herschel imaging data have been modelled by our team (Ladjal et al. in the A&A special issue) to show that the PACS and SPIRE continuum emission can be modelled by a modified blackbody with a temperature of 25 K.

Follow-up IRAM 2-1 observations on the apex of the bowshock reveal that the CO is detected, at a velocity very different from the systemic velocity of CW Leo.

In this follow-up proposal we plan to obtain a deep FTS spectrum and PACS line observation on the OI and CII cooling lines on the apex of the bowshock. If other CO lines will be detected we would be able to derive the rotational temperature near the apex of the bowshock which would reveal the physical conditions there.

Faint Extended Dust Envelopes of Young Planetary Nebulae

Proposal ID: GT2_ncox_1

Principal Investigator: Nick Cox

Time: 4.0 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


We propose to trace the distribution of cold dust in the extended envelopes of a selected sample of young Planetary Nebulae (PNe). Information on the mass-loss and overall envelope ejection process of Asymptotic Giant Branch (AGB) stars is imprinted in the morphology of the extended dust shells formed throughout the AGB phase. In particular the origin of asymmetrical PN shapes and their relation to spherical mass-loss presumed to occur on the AGB phase can be illuminated upon. We propose to use PACS to follow-up on AKARI/FIS observations of young PNe to study their mass-loss history. Only Herschel's unprecedented spatial resolution and sensitivity in the far-IR can detect the faint extended cold dust emission in these objects.

"Eyes and Bullets'': A study of peculiar bow shocks and dust arcs around AGB stars

Proposal ID: GT2_ncox_2

Principal Investigator: Nick Cox

Time: 4.3 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


The final evolutionary stages of stars are largely determined by ejection of mass from the stellar envelope. The mechanisms at work are thought to be understood in broad terms, but several major aspects remain elusive. In particular the transition from circumstellar matter to interstellar matter is poorly known. It has now also become clear that the interaction of mass outflows with the pre-existing interstellar medium on the one hand substantially complicate the interpretation of observational data, but on the other hand provide a new tool to study the interstellar medium. This proposal is dedicated to the investigation of peculiar types of extended structure c.q. bow shock emission and dusty arcs observed around AGB stars. We will obtain deep PACS 100 and 160 micron scan maps of so-called ``bullet'' and ``eye''-shaped interaction zones to study the infra-red emission at high angular resolution and model the bow shock SED to probe its dust and gas content.

Far-Infrared Emission from Bow Shocks around Runaway OB stars

Proposal ID: GT2_ncox_3

Principal Investigator: Nick Cox

Time: 4.7 hours priority 1

Category: Galactic Other


Runaway OB stars are massive early-type stars that travel through interstellar space with an anomalously high velocity. As the star travels with supersonic velocity through the interstellar medium matter is swept up resulting in a bow shock. The exact shape and conditions (density, temperature) of such a bow shock region depend critically on the stellar properties (such as velocity and mass-loss rate) as well as on the properties of the surrounding interstellar medium. Beyond the physics of the bow shocks themselves the size and shape can be used to infer parameters of the stellar wind of the star as wel as the local interstellar medium. We propose to use both the PACS and SPIRE instruments in photometric mode to charaterise in detail the far-infrared spatial structure and corresponding spectral energy distribution of these bow shocks. In particular, we expect to resolve, if present, turbulent instabilities.

Green Light from AGB StarS (GLASS)

Proposal ID: GT2_proyer_2

Principal Investigator: Pierre Royer

Time: 4.5 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


Ejecta of low to intermediate mass stars dominate the total mass that is re-injected by stars into the interstellar medium (ISM). Nevertheless, the mechanisms at the origin of the mass-loss of these stars are still not completely understood and their mass-loss history is still unknown. The problem is especially acute for the oxygen-rich evolved stars, for which theoretical models can still not predict the acceleration of the observed stellar winds.

During the last decade, new evidence arose from various wavelength domains that the mass-loss is varying in time, and is spatially structured, rather than constant and isotropic. In particular, Decin et al. (2011) analyse the structures revealed by Herschel-PACS around CW Leo, up to distances about five times larger than any structures that could be revealed with the VLT (FORS1). They show that the PACS "green" band (100 microns) is critically important to detect the complex density structure in the circumstellar material around CW Leo.

Detailed studies of the exact structure of the circumstellar material is of course crucial to set constraints on the mechanisms at the onset of mass-loss. Consequently, we propose to observe five objects at 100 microns with Herschel-PACS. Four of these objects are oxygen-rich, and all five have already revealed complex circumstellar structures at 70 or 160 microns, or in the sub-mm wavelength domain.

Unveiling the evolutionary paths of the most massive stars through the study of their ejected nebulae

Proposal ID: GT2_proyer_3

Principal Investigator: Pierre Royer

Time: 3.7 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


Several important questions remain open regarding the latest stages of evolution of the most massive stars, in particular regarding the exact evolutionary paths between the various subtypes of O stars, LBVs and Wolf-Rayet stars, and the mass-loss history of these objects throughout their lives.

In the framework of the MESS GTKP+GT1, we have obtained or will obtain PACS imaging of 9 massive star nebulae of various types (LBV, LBV candidate, OF/WN, Of?p, WR) and PACS spectroscopy of 4 of them. In this short follow-up proposal we want to obtain PACS line spectroscopy for 3 peculiar massive and evolved objects for which spectroscopy is lacking. In particular, these observations will allow to determine the elemental abundances in the nebulae as well as the mass of the neutral gas using the fine structure lines formed in the ionized gas and in the photo-dissociation region respectively.

Additional molecular observations in AGB and post-AGB objects

Proposal ID: GT2_vbujarra_6

Principal Investigator: Valentin Bujarrabal

Time: 12.5 hours priority 1

Category: Evolved Stars/Planetary Nebulae/Supernovae


The study of shells around AGB and post-AGB stars with Herschel/HIFI is being very fruitful. Observations of molecular lines have yielded extremely rich information on these objects, particularly on their warm gas components, which are crucial to understand the nature of the nebulae and the late stellar evolution.

Two guaranteed time projects, HIFISTARS and SUCCESS, have already obtained most of the originally proposed observations, yielding several hundreds of high-quality line profiles. But these results also indicate that some interesting observations were not proposed, because we could not imagine some unexpected results or because our samples were biased to previously well observed objects. We have realized that a small additional amount of time would significantly improve the existing data in three aspects: A) A few interesting O-rich AGB stars in the HIFISTARS sample were not observed in the strongest lines of H$_2^{18}$O and H$_2^{17}$O, which are in general found to be more intense than expected. B) We detected surprisingly strong and widespread NH$_3$ J,K=1,0-0,0 emission, but a proper analysis of these lines obviously requires data on higher-J lines. C) Our sample of post-AGB objects was biased towards northern sources, the best studied ones until now, but the proper exploitation of ALMA will require high-frequency data of southern nebulae.

We are accordingly proposing a few HIFI GT2 observations of evolved stars that, in combination with already existing data, will significantly improve the reach and quality of the previously allocated GT1. The total telescope time necessary to obtain these additional spectra is only 12.5 hr.

Galaxies / AGNs (7)

Unveiling the nature of the infrared emission in M87

Proposal ID: GT2_jfritz_2

Principal Investigator: Jacopo Fritz

Time: 2.0 hours priority 1

Category: Active galaxies/ULGs/QSOs


M87 is a giant elliptical galaxy located at the centre of the Virgo Cluster. Known to host an extremely massive black hole, it is an active galaxy showing no signs of quasar-like activity. The very nature of its infrared emission is, at present, not completely unveiled. The spectral energy distribution longward of 10 microns is dominated by the radio jet, known since more than 50 years to be powered by synchrotron emission. Whether a fraction of the infrared radiation has a different origin, such as thermal emission from a dusty torus, or from a diffuse dust component, is not clear yet.

We propose to perform deep observations of a field centered on M87 with PACS, at both 70 and 100 micron, at slow speed. In this way we will achieve the best possible spatial resolution, and the jet will be imaged at a very high S/N. Furthermore, we will be able to detect emission from the diffuse dust, if any, down to a few thousands solar masses.

PACS spectroscopy of bright Seyfert galaxies in the [OIV]26um line.

Proposal ID: GT2_lspinogl_6

Principal Investigator: Luigi Spinoglio

Time: 18.0 hours priority 1

Category: Active galaxies/ULGs/QSOs


This proposal is aimed at obtaining PACS spectroscopic data of 10 bright (5 type-1 and 5 type-2) Seyfert nuclei for six atomic fine-structure lines ([OIII]52um, [OI]63um, [OIII]88um, [NII]122um, [OI]145um and [CII]157um) and two molecular lines (CO J=18-17 and OH 119um). It will complete the coverage of the same ionic lines of another 11 Seyfert galaxies, already observed or reserved, by targeting the [OIII]52um line only. All targets were selected based on their optical classification and on the strength of their [OIV]25.9um fine-structure-line emission, proportional to their AGN bolometric luminosity. The proposed targets are among the brightest accretion-powered sources in the local Universe. The two [OIII] lines, together with the [OIV] line measured by Spitzer, will be used for the determination of their narrow-line-region gas density. The FIR spectroscopic tracers, combined with the MIR ones obtained with Spitzer, will enable us to classify and model the various levels of non-thermal and starburst activity in local bright Seyferts. The mid-to far-IR line ratio diagnostic diagrams that we will construct will be essential for the future interpretation of spectroscopic surveys at long wavelengths with ALMA and SPICA. The high spectral resolution of PACS will allow us to further study the dynamics of the nuclear gas, in combination with lines spectrally resolved by Spitzer IRS. The range spectroscopy with PACS has been optimized to allow the detection of 6 fine structure lines, 1 CO line, 1 OH doublet in a total time of 18.0 hours.

Far-infrared investigation of early-type galaxies with dust lanes

Proposal ID: GT2_mbaes_2

Principal Investigator: Maarten Baes

Time: 3.4 hours priority 1

Category: Nearby galaxies


Early-type galaxies are known to harbor a complex multi-phase interstellar medium. Their dust content, however, remains mysterious. Deep optical imaging surveys have shown that a large number of early-type galaxies possess dust features in a variety of morphological forms. Dust has also been detected in emission in many early-type galaxies using IRAS, ISO and Spitzer observations. Strangely, the dust masses derived from far-infrared observations are typically an order of magnitude larger than those estimated using optical extinction features. This inconsistency in the dust energy balance could suggest the presence of a diffusely distributed dust component that is hard to notice in extinction.

We propose PACS and SPIRE imaging of a sample of 11 carefully selected, nearby early-type galaxies with regular and well-defined dust lanes. We will construct panchromatic radiative transfer models for each of these galaxies, based on multi-wavelength optical/NIR images and FIR/submm images. This will enable us to systematically investigate the dust energy balance in dust-lane early-type galaxies, to investigate the amount and the spatial distribution of the dust, to determine the optical properties of the dust, and to test the existence of a diffuse dust component.

Characterizing the Molecular Outflow in Arp 220

Proposal ID: GT2_nrangwal_2

Principal Investigator: Naseem Rangwala

Time: 4.7 hours priority 1

Category: Nearby galaxies


Observations of massive molecular outflows in galaxies can significantly improve our understanding of the connection between AGN/starbursts-feedback and galaxy evolution. It is believed that the energy injection from an AGN or starbursts can quench star formation by expelling the molecular gas out of the galaxy, transforming gas-rich blue galaxies to gas-poor red galaxies. However, the evidence for massive molecular outflows had been missing, until recently, when it was discovered in Mrk231 and NGC1266.

We detected a massive molecular outflow in Arp 220 from the FTS spectrum that was observed as a part of the Very Nearby Galaxy Survey GT key project. The signature of a molecular outflow was seen in the P-Cygni profiles of OH+, H2O+ and H2O -- major molecules involved in the ion-neutral chemistry producing water in the ISM. This outflow can be driven by a hidden AGN or starburst activity in Arp 220. Because FTS could not fully resolve this outflow we were only able to provide a lower limit on the mass of the outflow and an upper limit on the velocity. To properly characterize this outflow we propose to use HIFI to fully resolve the P-Cygni line profile so that we can estimate the outflow velocity and mass with higher accuracy. We choose to observe the OH+ 972 GHz P-Cygni line profile, which is about 1000 km/s wide. To completely cover this feature and still have enough continuum to obtain a good baseline subtraction, we propose to observe it over two frequency tunings. In 2.35 hrs per frequency tuning, we will obtain a S/N of about 10 and 5 per 20 km/s resolution bin in the absorption dip and the emission peak, respectively. The total time for the entire observation is 4.7 hrs. Herschel is the only submillimeter facility that is capable of doing this observation.

Spectral mapping of the closest galactic nucleus

Proposal ID: GT2_rguesten_5

Principal Investigator: Rolf Guesten

Time: 28.5 hours priority 1

Category: Extra-Galactic Other


Due to its proximity, our Galactic Center provides a unique opportunity to study the physical processes that occur within (extra)galactic nuclei with unprecedented sensitivity and spatial resolution. Herschel provides the only opportunity to probe the detailed physical conditions of the circumnuclear neutral material and the feedback processes with the central energy source(s) in our own Galaxy, and by extension in other galactic nuclei.

We propose to acquire wide range (51 to 670 micron) spectral maps towards the atomic and molecular gas surrounding SgrA. Combining data from the PACS and SPIRE instruments, we will establish a complete inventory of the FIR spectrum accessible to Herschel across the central 5 arcmin (12 pc) of the Galaxy.

Our immediate goal is to characterize the physical and chemical conditions of the gas in both the central (ionized) cavity and in the surrounding neutral gas (often referred to as circumnuclear disk, or CND) that is presumably the reservoir of material that can flow to the central black hole. Our supporting ground-based and first targeted HIFI observations show a high-excitation state of the molecular gas in the CND, with a strong radial excitation gradient across the disk and a very sharp inner transition zone to the central cavity. These early data resemble the hard XDR-type CO line SED observed towards e.g. Mrk231.Herschel data cover lines from energy levels needed to constrain the conditions within, and energetics of the CND. We will use state-of-the-art XDR/PDR models that include multiple heating processes (a.o., shock, dissipation of turbulence) to interpret the data.

The data product will be one of Herschel's legacies in the detailed study of galactic nuclei. This data set, with high sensitivity, high spatial resolution, and broad wavelength coverage, will be an essential resource for many studies of the Galactic Center. No comparable study of this region will be possible for many years to come.

HIFI and PACS Observation of NGC 5102

Proposal ID: GT2_sbeaulie_1

Principal Investigator: Sylvie Florence Beaulieu

Time: 3.5 hours priority 1

Category: Nearby galaxies


NGC 5102 provides a rare opportunity to study directly the fuelling of a starburst by infalling gas. We can still see the ongoing star formation, the central extended ionized gas and the likely source of the gas in the form of the HI ring. Our Herschel programme for NGC 5102 will cover two aspects of the starburst process. First, we would like to know if there is additional current star formation hidden by dust in the inner region of the galaxy. Then, we would like to probe the dynamics and physical conditions of the molecular gas which is flowing into the centre of NGC 5102. Using the kinematic resolution of HIFI, it should be possible to measure a velocity gradient in this inflow

Unveiling the Warm Molecular Gas in Blue Compact Dwarf Galaxies

Proposal ID: GT2_vleboute_3

Principal Investigator: Vianney Lebouteiller

Time: 8.3 hours priority 1

Category: Nearby galaxies


Hierarchical models of galaxy evolution place dwarf galaxies in the role of building blocks while on the other hand alternative models to explain galaxy "downsizing" have also been put forth. Key to the coherent picture of galaxy evolution is a proper prescription of metal enrichment and how galaxies convert their gas into stars. Our best local universe analogs to study star formation in the early universe are star forming blue compact dwarf galaxies (BCDs) with metallicities ranging as low as 1/50 solar. How these low mass, low metallicity star forming systems form stars relatively efficiently, yet with little detectable CO emission, has been a subject of much investigation over 2 decades and still remains a mystery today. Pinning down the molecular gas reservoir of two well-known star-forming low metallicity dwarf galaxies (He2-10 and IC10) is the goal of this proposal, using the Herschel SPIRE/FTS spectrometer.

Cosmology (1)


Proposal ID: GT2_mviero_1

Principal Investigator: Marco Viero

Time: 103.4 hours priority 1

Category: Cosmology/Extra-galactic surveys


We propose a unique addition to the HerMES family of maps, the HerMES Large Mode Survey (HeLMS), which will be observed as part of the remaining SPIRE GT time. The field covers 270 deg2 with two repeats over roughly 106 hours. It is chosen to overlap the SDSS Stripe 82 in a region where the Galactic cirrus — with a mean flux density of ∼ 1.2 MJy sr−1 — is at its lowest. The ancillary coverage in this field is extensive, particularly in the optical, making it an attractive large field. The scientific advantages of having a field with the size and makeup of HeLMS are twofold: first, the large survey area, of which ∼ 55 deg2 overlaps Stripe 82, will allow us to resolve approximately ∼ 250, 000 sources, of which ∼ 250 − 500 will be gravitationally lensed. Second, the large, uniform and cross-linked area will allow for unprecedented measurement of large-scale modes (down to l ∼ 150). Such fidelity would be a unique asset in the submillimeter regime for the foreseeable future, and would enable cross-frequency correlation analysis with ∼ 80 deg2 of deep ACT maps, Planck over the full 270 deg−2, as well as future observations with upcoming instruments like ALMA, ACTpol, and others.