HI in galaxies from z = 0.002 to z = 0.2

Thijs van der Hulst

Kapteyn Astronomical InstituteUniversity of Groningen

Kapteyn astronomical institute

Open Questions

- When and how quickly did the gas settle in the dark matter potential wells

- Where and how did gas get converted into stars

- When and how did the merging process develop

- What is the importance of gas accretion versus merging

Radiotelescopes can trace the neutral gas extremely well( to go beyond z = 0.2 we need SKA )

COLD GAS HI observations local universe

- Extended HI disks with outer spiral structure

- Large majority of disks WARPED and LOPSIDED

- Lumpy HI structures (clouds, tails, filaments) around galaxies

Result of recent minor mergers and accretion?

- Large reservoirs extra-planar gas

Sancisi et al. A&A Rev., 2008

WARPS

LOPSIDEDNESS

WSRT 1976

HI WSRT

HI VLA

3x108 Mʘ

HI masses in outer structures 108 - 109 Mʘ

optical NGC 5055 neutral hydrogen WSRT

same scale Battaglia et al. 2005

EXTENDED HI (note the spiral structure)

NGC 5055 neutral hydrogen WSRT

same scale Battaglia et al. 2005

EXTENDED HI (spiral arms) GALEX

NGC 6946optical neutral hydrogen

same scale

WSRT

Boomsma et al. 2007

neutral hydrogen

same scale

Boomsma et al. 2007

WSRTDeep B-band

A. Ferguson 2007

Some star formation also in outer disk

NGC 6946

HIGH VELOCITYCLOUDS( total amount ~3 x 108 Mʘ )

NGC 6946Accretion?

Boomsma et al. 2007

HI map WSRT

NGC 2403

HI VLA

Fraternali et al. 2001

modelthin disk

Anomalous gas

3x108 Mʘ

NGC 891 Anomalous HI ~ 1 x 108 Mʘ

Fraternali, 2007

Extra-planar HI

MILKY WAY, NGC 891, NGC 2403M 31, NGC 4559, NGC 253, UGC 7321, NGC 5775, NGC 6946

Emerging picture:

HI disk

- extended with outer spiral structure - warped - lopsided - porous

Extra-planar HI (high velocity clouds)

ACCRETION?

Local UniverseHI detection limits:Column densities 1 x 1019 cm-2

Accreted HI 107 - 109 Mʘ

Time scales 108 - 109 yrsGalaxy fraction 25 - 50 %Accretion rate 0.1 - 0.5 Mʘ / yr

Masses 1 x 106 Mʘ

SUMMARY

4. Cold gas lumpy accretion at a mean rate of 0.1 – 0.5 Mʘ / yr

25 – 50 % of all galaxies accrete lumps of gas of 107-9 Mʘ

1. Spiral structure and star formation in outer HI disks

2. Most galaxies warped and lopsided

3. Large reservoirs of extra-planar HI

HI near the center of the Virgo cluster

Oosterloo & van Gorkom, 2005, A&A 437, 19

NGC 4388

3.8 x 108 Mʘ

The Amazing NGC 7426

- ‘Normal Elliptical- Two tails, 185, 125 h-1 kpc in length!- 4 x 109 h-2 Mʘ

- NHI (min) = 1019 cm-2

- Tails aligned with Pisces-Perseus super cluster structure

>300 h-1 kpc

Schiminovich, van Gorkom et al.

Verheijen, van Gorkom et al. 2007

Present state of the art: imaging HI emission out to z = 0.2

240 hour integration with WSRT

SKA goals for deep fields:

- get to MHI* galaxies out to z = 2

- detect HVC mass objects to z = 0.2

- detect dwarf galaxies to z = 0.5

redshift lookback

time

HI mass limit (Msun)

# detections HI mass limit (Msun)

# detections

Gyr t = 360 h t = 1000 h

0.5 – 1.0 5.0 – 7.7 5.0 x 108 1.6 x 106 3.0 x 108 2.4 x 106

1.0 – 1.5 7.7 – 9.3 1.3 x 109 1.8 x 106 7.9 x 108 2.7 x 106

1.5 – 2.0 9.3 – 10.3 2.7 x 109 1.9 x 106 1.6 x 109 2.7 x 106

2.0 – 2.5 10.3 – 11.0 4.8 x 109 1.7 x 106 2.9 x 109 2.5 x 106

2.5 – 3.0 11.0 – 11.5 7.8 x 109 1.6 x 106 4.7 x 109 2.3 x 106

3.0 – 3.5 11.5 – 11.8 1.2 x 1010 1.4 x 106 7.3 x 109 2.0 x 106

3.5 – 4.0 11.8 – 12.1 1.8 x 1010 1.2 x 106 1.1 x 1010 1.8 x 106

4.0 – 4.5 12.1 – 12.3 2.7 x 1010 1.0 x 106 1.6 x 1010 1.5 x 106

Number of galaxies detectable as a function of redshift per square degree

redshift lookback

time

HI mass limit (Msun)

# detections HI mass limit (Msun)

# detections

Gyr t = 360 h t = 1000 h

0.5 – 1.0 5.0 – 7.7 3.6 x 109 3.8 x 105 2.1 x 109 5.6 x 105

1.0 – 1.5 7.7 – 9.3 9.3 x 109 4.5 x 105 5.6 x 109 6.5 x 105

1.5 – 2.0 9.3 – 10.3 1.9 x 1010 4.3 x 105 1.1 x 1010 6.4 x 105

2.0 – 2.5 10.3 – 11.0 3.4 x 1010 4.0 x 105 2.0 x 1010 5.8 x 105

2.5 – 3.0 11.0 – 11.5 5.5 x 1010 3.6 x 105 3.3 x 1010 5.2 x 105

Phase-1 SKA: Number of galaxies / sq. deg. as a function of redshift

Redshift Frequency Tsys Angular Resolution

Linear Resolution

SB -dimming

Luminosity Distance

Lookback time

HI mass limit

MHz K arcsec kpc Gpc Gyr Msun

0.2 1183.67 50.4 0.52 1.7 0.796 0.972 2.41 6.1x108

0.5 946.94 51.4 0.65 4.0 1.486 2.825 5.02 8.7x108

2.0 710.20 53.8 0.87 7.0 3.026 6.640 7.73 2.7x109

2.5 568.16 57.5 1.09 9.3 4.000 11.02 9.32 7.2x109

2.0 473.47 62.7 1.31 11.1 4.796 15.75 10.32 1.5x1010

2.5 405.83 69.6 1.52 12.5 5.469 20.72 11.00 2.6x1010

3.0 355.10 78.3 1.74 13.6 6.052 25.87 11.48 4.3x1010

3.5 315.64 89.3 1.96 14.6 6.566 31.15 11.83 6.7x1010

Detection limits for SKA for t = 12 hours

Phase-1 SKA Detection limits for t = 12 hours

Redshift Frequency Tsys Angular Resolution

Linear Resolution

SB -dimming

Luminosity Distance

Lookback time

HI mass limit

MHz K arcsec kpc Gpc Gyr Msun

1.0 710.20 53.8 0.87 7.0 3.026 6.640 7.73 1.9x1010

1.5 568.16 57.5 1.09 9.3 4.000 11.02 9.32 5.1x1010

2.0 473.47 62.7 1.31 11.1 4.796 15.75 10.32 1.0x1011

2.5 405.83 69.6 1.52 12.5 5.469 20.72 11.00 1.8x1011

3.0 355.10 78.3 1.74 13.6 6.052 25.87 11.48 3.0x1011