1 / 59

The Galactic Plane in H a, and at 1 arcsec resolution: (The north as seen by IPHAS)

The Galactic Plane in H a, and at 1 arcsec resolution: (The north as seen by IPHAS) Janet Drew, Imperial College London. STScI, 11 th July 2007 (image: N. Wright UCL). Talk Outline. Introduction/motivation IPHAS – the survey IPHAS science Conclusion. Nebulae Emission line stars

limei
Download Presentation

The Galactic Plane in H a, and at 1 arcsec resolution: (The north as seen by IPHAS)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Galactic Plane in Ha, and at 1 arcsec resolution: (The north as seen by IPHAS) Janet Drew, Imperial College London STScI, 11th July 2007 (image: N. Wright UCL)

  2. Talk Outline • Introduction/motivation • IPHAS – the survey • IPHAS science • Conclusion • Nebulae • Emission line stars • Stellar populations from the photometry

  3. Reasons to survey the Galactic Plane in Ha, at 1 arcsec resolution • To rectify scarcity of stellar objects in short-lived early and late phases of stellar evolution •  Ha emission common among young/old/luminous/compact stellar objects • In the north, better coverage of PNe for studying galactochemical gradient outside the Solar Circle  access to compact and faint nebulae

  4. Reasons (continued) • To trace the structure of the Galactic disk •  Ha = star-formation indicator  emission line stars as spiral arm tracers • General stellar population photometry: • Ha narrow-band measurement, linked with broad-band data yields… •  spectral type sensitivity, giving photometric discrimination of stellar content • mapping of both stars, by type, and extinction

  5. Numbers of catalogued emission line stars – by magnitude, north (Kohoutek/Wehmeyer) and south (Stephenson/Sanduleak): • a factor of ~1000 in depth being opened up …notice the north/south contrast South south north North

  6. IPHAS observing and data release

  7. Definition of IPHAS: IPHAS = INT Photometric Ha Survey of the Northern Galactic Plane Telescope/instrument: INT/Wide Field Camera Survey area: all northern Plane longitudes; latitude range –5o < b < +5o (1800 sq deg) Magnitude limit (10s): r’ = 20 Required observations: Ha (120 sec), Sloan r’ (30 sec) and i’ (10 sec) at 2 overlapping pointings Seeing: < 2 arcsec, median ~ 1.1 arcsec

  8. The IPHAS Consortium: Janet Drew (PI) Robert Greimel Mike Irwin, Nic Walton Astronomers in the Isaac Newton Group countries: the UK, Netherlands and Spain …also in the USA, Australia, Germany (see iphas.org) (Contributions to talk: Andrew Witham, Danny Lennon, Antonio Hales-Gebrim, Stuart Sale)

  9. The INT Wide Field Camera: Mosaic of 4 CCDs – pixel size 0.33”x0.33” – area imaged ~0.25 sq deg ~7600 x 2 pointings (5 mins per pointing)

  10. …filling the northern Plane: (a section of the IPHAS pointing map at l = 75o)

  11. To cover 1800 sq.degs, twice • 22 clear weeks • Next slides: 2003 – 2005 IPHAS data-taking sequence (~60% achieved in this time): • 200+ nights observing effort, via standard PATT/CAT/NFRA time allocations

  12. Status end 2006:- 72% at < 1.7 arcsec seeing, 80% < 2.0 arcsec Likely completion: end 2007

  13. IPHAS data release: • Reduced images already available from CASU • Early release of point source catalogue: 2003-2005 data, (~60% of survey, nightly calibration – not yet uniform) • Aiming for photometrically uniform catalogue, and public-domain ‘Ha Atlas’ ~200 million objects, due by end July ‘07

  14. IPHAS science • A brief word on nebulae • Emission line stars: how to find them, preliminary catalogue, and one example rarity • Exploitation of the main stellar locus in the (r’-Ha, r’-i’) plane

  15. Extended sources: nebulae

  16. The Prince’s Nebula (Mampaso et al 2006) Ha r’ i’ Ha point source (CS)

  17. …deeper optical image:

  18. A low-density old nebula…. -- at large Galactocentric distance (13.4 kpc) -- low metallicity progenitor -- a Type I PN (with He/H=0.13, N/O=1.8) -- with an interacting binary central star? CaII IR triplet – in central star spectrum:

  19. Another PN discovery: IPHAS + [OIII] combined ~100x100 arcsec2 image Corradi, Mampaso, Viironen, Sabin, Parker, Morris… First aim: to get out an RA 18—20 hrs list of nebulae …mainly finding low surface brightness resolved nebulae, including interesting anticentre candidates (Nick Wright, UCL)

  20. Emission line stars

  21. Where emission line stars are in the IPHAS (r’-Ha,r-i’) colour-colour plane: (EB-V) (EW) High-confidence Ha emitters Main stellar locus from Drew et al 2005 (survey paper)

  22. The preliminary conservatively-selected emission line star catalogue: Witham et al, to be submitted ~5000 objects New catalogue (in red) compared with Kohoutek and Wehmeyer 1999 (in black)

  23. Distribution of conservatively selected emission line objects: Black: r’ > 18 Red: 13 < r’ < 18 Green: area surveyed so far

  24. Distribution against Galactic latitude of: Conservatively-selected emission line objects (top) Premium sample of stars, with repeat/consistent photometry (middle) Emitters/premium (bottom)  confirms warp

  25. Distribution against Galactic longitude: Top – emitters Middle – premium sample Bottom – emitters/premium

  26. Spectroscopic follow up ….MMT/HectoSpec, FAST, La Palma ITP e.g. 2 MMT/HectoSpec selections (up to 300 fibres in a 1-degree field) (Cyg OB2 centre) (DR15, 0.7o south) (red = Ha emitter, blue = spectrum obtained)

  27. Long-slit follow-up: an extreme rarity, and a mystery… IPHAS J0214… r’ = 12.9, spectrum dominated by He and Fe lines …both broadened stellar, and narrow nebular, components Discovery spectrum obtained using FAST

  28. A class of two? J0214 (bottom) and HDE 326823, Be!pec (top) (Lennon et al – in prep.)

  29. Near-MS A stars and more(Direct exploitation of IPHAS photometry)

  30. The power of the IPHAS (r’-Ha, r’-i’) plane: • The main sequence, as it reddens, sweeps out area; • Emission line stars, M dwarfs, M giants, white dwarfs, and near-MS A stars are all easily selected.

  31. Near-MS A star selection from IPHAS colour-colour plane: • D (r’-Ha) ~ 0.025 along bottom of main locus captures A0-5 sub-types • colours metallicity insensitive • representative M(r’) ~ 1.5 for A0-5 field stars at ages > 5 - 10 Myrs •  long sightlines achieved • Uses:- • hunting A dwarfs in their own right • accessing a simple/common (almost) standard candle

  32. Selecting near-MS A stars …..a control experiment: the 5-10 Myr old open cluster NGC 7510 expected distance modulus and reddening

  33. An A dwarf census – in IPHAS and Spitzer GLIMPSE overlap area Question:- how many A0-5 dwarfs show mid-IR (Vega-like) dust excesses? Method: select, deredden using IPHAS, then examine IR colours/SED Hales-Gebrim, 2007 PhD thesis

  34. The answers: Searching 13.5 < r’ < 18.5,  23050 candidate IPHAS A stars in GLIMPSE overlap region 3062 of these come with 2MASS magnitudes, IRAC detections in >2 bands At 8 mm, 1.1% have dust excesses At 24 mm, 1.2% have excesses …only 10 at both wavelengths

  35. Mapping Cyg OB2 and its cluster environment: The big (how big?) OB association in Cygnus-X: IPHAS data for most central field, with AV =4.5 and AV = 7.0 MS tracks, superimposed How are near-MS A stars distributed?

  36. A stars in and around Cyg OB2: 21 field overlaps shown Dereddened magnitudes Blue circles:- 12 < r’0 < 12.5 Smaller black dots 12.5 < r’0 < 13 (Purple box = 2MASS stellar density peak)

More Related