redshifted extragalactic molecular lines

Mechanisms 1. Thermal 2. Masers 3. Dasars

Science A. High Redshift B. Galaxy Evolution C. Star Formation/ISM D. Massive Black Holes E. Cosmology F. Physical Constants

Jeremy Darling (CASA, University of Colorado)

Redshifted Extragalactic Molecular Lines

Redshifted Molecular Lines

Linez when

= 10 GHz

CO (1-0) 10.5

HCN (1-0) 7.9

HCO+ (1-0) 7.9

CS (1-0) 3.9

SiO (1-0) 3.3

NH3 (24 GHz) 1.4

H2O (22 GHz) 1.2

H2CO (211-212) 0.45

HC3N (1-0) Any

CH3OH (6.7 GHz) Any

H2CO (110-111) Any

OH (1.8, 4.7, 6.0 GHz) Any

Redshifted Molecular Lines

Linez when

= 10 GHz

CO (1-0) 10.5

HCN (1-0) 7.9

HCO+ (1-0) 7.9

CS (1-0) 3.9

SiO (1-0) 3.3

NH3 (24 GHz) 1.4

H2O (22 GHz) 1.2

H2CO (211-212) 0.45

HC3N (1-0) Any

CH3OH (6.7 GHz) Any

H2CO (110-111) Any

OH (1.8, 4.7, 6.0 GHz) Any

Out of reach (Existence of molecules?)

Redshifted Molecular Lines

Linez when

= 10 GHz

CO (1-0) 10.5

HCN (1-0) 7.9

HCO+ (1-0) 7.9

CS (1-0) 3.9

SiO (1-0) 3.3

NH3 (24 GHz) 1.4

H2O (22 GHz) 1.2

H2CO (211-212) 0.45

HC3N (1-0) Any

CH3OH (6.7 GHz) Any

H2CO (110-111) Any

OH (1.8, 4.7, 6.0 GHz) Any

z = 0.9 gravitational lens (e.g. Muller et al. 2006)

• high dipole moment • expect detections in submm

galaxies soon!• dense gas tracer

star formation (akin to HCN, HCO+)

Redshifted Molecular Lines

Linez when

= 10 GHz

CO (1-0) 10.5

HCN (1-0) 7.9

HCO+ (1-0) 7.9

CS (1-0) 3.9

SiO (1-0) 3.3

NH3 (24 GHz) 1.4

H2O (22 GHz) 1.2

H2CO (211-212) 0.45

HC3N (1-0) Any

CH3OH (6.7 GHz) Any

H2CO (110-111) Any

OH (1.8, 4.7, 6.0 GHz) Any

z = 0.7, 0.9 gravitational lenses (Henkel et al. 2005, Menten et al. in prep)

• Tunneling transitions (many)• Thermometer• Constancy of me/mp

(Flambaum & Kozlov 2007)

Chengalur, deBruyn, &Chengalur, deBruyn, & Narasimha 1999Narasimha 1999

Patnaik et al. 1994Patnaik et al. 1994

Nair et al. 1993Nair et al. 1993

Ammonia (NHAmmonia (NH33): ): “Umbrella” Tunneling“Umbrella” Tunneling

Rohlfs & Wilson 1996

Ammonia (NH3) Symmetric top molecule

Electrostatic repulsion between N and H3 plane

“Umbrella” inversion possible via tunneling (for low vibration states)

Each rotation ladder has inversion splitting

Inversion transitions can be masers(first maser was NH3 24 GHz!)

Ammonia (NH3) Symmetric top molecule

Electrostatic repulsion between N and H3 plane

“Umbrella” inversion possible via tunneling (for low vibration states)

Each rotation ladder has inversion splitting

Gastrophysics Multiple inversion lines give Trot B0218+357:

z = 0.67; Trot = 35 K

PKS 1830-211: z = 0.89; up to (J,K) = (10,10) detected!

(Menten et al in prep)

(Henkel et al 2005)

Ammonia (NH3): “Umbrella” Tunneling

Redshifted Molecular Lines

Linez when

= 10 GHz

CO (1-0) 10.5

HCN (1-0) 7.9

HCO+ (1-0) 7.9

CS (1-0) 3.9

SiO (1-0) 3.3

NH3 (24 GHz) 1.4

H2O (22 GHz) 1.2

H2CO (211-212) 0.45

HC3N (1-0) Any

CH3OH (6.7 GHz) Any

H2CO (110-111) Any

OH (1.8, 4.7, 6.0 GHz) Any

z = 0.66 maser (Barvanis & Antonucci 2005)

• 5 mJy line• Acceleration search (disks)• HSN targets• Cosmology

H2O Megamasers

• Associated with Type 2 nuclei

• Highly beamed

• NGC 4258: - VLBI proper motions of maser spots - Line accelerations

Geometric distance 7.2 0.5 Mpc (Herrnstein et al. 1999)

(H2O masers can also occur in jets and outflows)

Herrnstein et al. 1999

NGC 4258

Redshifted Molecular Lines

Linez when

= 10 GHz

CO (1-0) 10.5

HCN (1-0) 7.9

HCO+ (1-0) 7.9

CS (1-0) 3.9

SiO (1-0) 3.3

NH3 (24 GHz) 1.4

H2O (22 GHz) 1.2

H2CO (211-212) 0.45

HC3N (1-0) Any

CH3OH (6.7 GHz) Any

H2CO (110-111) Any

OH (1.8, 4.7, 6.0 GHz) Any

No megamasers (Phillips et al 1998, Darling et al 2003)

* Menten predicts broad shallow absorption akin to Galactic Center

Redshifted Molecular Lines

Linez when

= 10 GHz

CO (1-0) 10.5

HCN (1-0) 7.9

HCO+ (1-0) 7.9

CS (1-0) 3.9

SiO (1-0) 3.3

NH3 (24 GHz) 1.4

H2O (22 GHz) 1.2

H2CO (211-212) 0.45

HC3N (1-0) Any

CH3OH (6.7 GHz) Any

H2CO (110-111) Any

OH (1.8, 4.7, 6.0 GHz) Any

z = 0.7,0.9 gravitational lenses (Menten & Reid 1996, Menten et al. 1999)

Biggs et al 2001

Galactic H2CO

Dark Clouds: - “Anomalous” H2CO absorption (e.g. Palmer et al.

1969)

- Absorption in multiple cm lines- No radio continuum source!

Darling & Goldsmith (in prep)

Darling & Goldsmith (in prep)

Barnard 227

NGC 2264

HH22CO: CO: The DASARThe DASAR

L ightA mplification byS timulated E mission ofR adiation

Inversion: “Heating” of lines Tx >> Tkin

Pump required: Chemical, collisional, radiative

D arkness*A mplification** byS timulated A bsorption ofR adiation

Townes et al (1953)

Anti-Inversion: “Cooling” of lines Tx < TCMB

Pump required: Collisions with H2

*Not really dark.**Not a true amplification.

Galactic H2CO

Dark Clouds: - “Anomalous” H2CO absorption (e.g. Palmer et al.

1969)

- Absorption in multiple cm lines- No radio continuum source!

• Can H2CO be observed in other

galaxies?

2. Can “anomalous” H2CO absorption be

observed in galaxy-scale analogs of Dark Clouds?

Darling & Goldsmith (in prep)

Darling & Goldsmith (in prep)

Barnard 227

NGC 2264

H2CO Absorption Against the CMB

H2CO: The DASAR

The CMB is the ultimate illumination source:

• Behind everything• Everywhere• Uniform on arcsec scales

H2CO absorption against the CMB offers an unrivaled, extinction-free, mass-limited probe of dense (star-forming) molecular gas, independent of redshift!

Extragalactic H2CO

Emission in (U)LIRGs (OH Megamasers)

Arp 220 III Zw 35

Absorption in starbursts (OH absorbers)

NGC 520NGC 660

Henkel & Darling (in prep)

Baan, Guesten, & Haschick (1986)

Extragalactic HExtragalactic H22CO CO

Emission in (U)LIRGs (OH Megamasers)

Arp 220 III Zw 35

Absorption in starbursts (OH absorbers)

NGC 520NGC 660

Filho, Barthel, & Ho (2002)

NGC 660, 8.4 GHz

Henkel & Darling (in prep)

Extragalactic H2CO So far…• All OHMs show 6 cm emission in H2CO• All OH absorbers show 6 cm absorption

H2CO 6 cm line flip at

n(H2) ~ 105.6 cm-3

A critical density threshold for OH megamasers?

(there must also be a density upper limit where inversion is quenched… n(H2) ~ 106 cm-3)

H2CO Survey of Local Star-Forming Galaxies

(Mangum, Darling, Menten, & Henkel, 2007)

M 82

Arp 220

6 cm

6 cm

2 cm 2 cm

So far…• All OHMs show 6 cm emission in H2CO• All OH absorbers show 6 cm absorption

H2CO 6 cm line flip at

n(H2) ~ 105.6 cm-3

A critical density threshold for OH megamasers?

(there is also an upper density where 2 cm line flips… n(H2) ~ 105.8 cm-3)

(Mangum et al. 2007)

6 cm

2 cm

OHMs

(kilomaser)

Extragalactic H2CO

• H2CO dasar effect

spans 3 orders of magnitude in density

• cm line ratio is sensitive to n(H2)

Darling & Zeiger

Extragalactic H2CO

• H2CO dasar effect

is insensitive to TCMB

• The effect likely becomes easier to detect with increasing redshift!

Darling & Zeiger

Extragalactic H2CO

Darling & WiklindBiggs et al 2001

Extragalactic H2CO

Maser Emission in (U)LIRGs (OH Megamasers)

Arp 220 III Zw 35

Absorption in starbursts (OH absorbers)

NGC 520NGC 660

Absorption in dense cloudsB0218+357PKS 1830-211

Redshifted Molecular Lines

Linez when

= 10 GHz

CO (1-0) 10.5

HCN (1-0) 7.9

HCO+ (1-0) 7.9

CS (1-0) 3.9

SiO (1-0) 3.3

NH3 (24 GHz) 1.4

H2O (22 GHz) 1.2

H2CO (211-212) 0.45

HC3N (1-0) Any

CH3OH (6.7 GHz) Any

H2CO (110-111) Any

OH (1.8, 4.7, 6.0 GHz) Any

z = 0.26 megamaser z = 0.9 gravitational lens

IRAS 02524+2046 z = 0.18

PKS 1830-211

z = 0.89HI

OH

Merging Galaxies:

OH Megamasers: OH Megamasers: Tracers of Major Mergers, Star Formation, and Massive Black Holes

• OH FIR and favors dusty environments• OHMs seem to indicate massive black holes (small sample)• OHMs seem to favor a specific stage of merging, star formation• Sampling a specific stage of merging BH binary formation rate long-period GW background• There are many approaches to these problems; no single method will be a panacea.

OH Megamasers: OH Megamasers: Tracers of Major Mergers, Star Formation, and Massive Black Holes

• OH FIR and favors dusty environments• OHMs seem to indicate massive black holes (small sample)• OHMs seem to favor a specific stage of merging, star formation• Sampling a specific stage of merging BH binary formation rate long-period GW background• There are many approaches to these problems; no single method will be a panacea.

Begelman, Blandford & Rees 1980

OHMs

GWs

(CSOs?)

OH Megamasers in HI Surveys

Briggs (1988)

20 mJy

5 mJy

1 mJy

0.2 mJy

OH Megamasers: Power-law LF Increasing Merger RateIncreasing Star Formation

Briggs (1998): The deeper the HI survey, the more confusion with OH megamasers

At z ~ 0.1 the OH line > HI line

(but remains rare)

At z ~ 1 there is ~ 1 OHM per deg2

OH Megamaser Surveys: High(er) Redshift

Barriers– RFI– Receivers– Rarity

Boons– Half of OH megamasers are QSO-like– Current sensitivity is adequate for z ~ 1– More merging in past

Detecting OHMegamasers atHigh Redshift

Submm Galaxies

PKS 1413+135: OH and HI Absorption

Conjugate OH satellite lines:1612, 1720 MHz(see also Kanekar et al. 2004)

Systematic offset from HI

Is the offset physical?

How to assess offsets?

13 km s-1

Variability in OH Megamasers: Super-VLBI Resolution

Multiple independent variable features with different timescales:

Segregates sizescales

May segregate positions

Offers sub- milliarcsecond resolution

Sensitivity is key

02524+2046

Observations:

• Day-to-day (and intraday) variation

• Multiple narrow variable components

• 1665 MHz line varies, often (but not always) with 1667

• Components often (but not always) correspond to peaks

Darling (in prep)

02524+2046

Observations: • Unprecedented matching between 1665 and 1667 MHz lines in average and variable fits, including flaring lines

• Variation envelope shows proportional 1667:1665 modulation of ~20% (~30% expected for point source)

• Size scales < 1 pc (0.3 milliarcsec)

• Tb > 81011 K (!)

• (What is line separation in sky?)

Darling (in prep)

Variability Studies: A Super-VLBI Single Dish Telescope

• Variability studies can segregate size scales and on-sky projections of OH megamaser components with super-VLBI resolution (~pc at z = 0.2).

• Roughly half of luminous OMHs at z > 0.1 are variable/compact.

• We have identified compact 1665 MHz emission coincident with compact 1667 MHz lines. • Observed phenomena are consistent with strong refractive ISS (and detailed tests are possible)

• ISS predictions are consistent with VLBI observations

• Long-term monitoring can identify small accelerations

CharacterizingVariability

• 10% modulation

• 4.5 day timescale

Assuming ISS

Variable features: < 1.2 parsec

Quiescent features: > 4 parsec

CharacterizingVariability

• 10% modulation

• 4.5 day timescale

Assuming ISS

Variable features: < 1.2 parsec

Quiescent features: > 4 parsec

Robishaw, Heiles, & Quataert

z = 0.217

Magnetic Fields in OH Megamasers

Robishaw, Heiles, & Quataert have detected Zeeman splitting in multiple OH megamaser galaxies!

Prediction:

Zeeman splitting will also be observable in OH conjugate lines and OH in molecular absorption systems (detectable at arbitrary redshift).

Discussion Questions: High FrequencyWhat can be done to improve 5-10 GHz sensitivity?

– Has double position switching been evaluated at high frequency?– What bandwidths can be correlated?– How good are baselines across 100 MHz? 1 GHz?

• The H2CO “densitometer” offers tremendous promise• H2O surveys and studies (cosmology)• NH3 tunneling lines• High redshift CS

How high in frequency can Arecibo still work with the HSA?– What is the impact of strong continuum on Arecibo within the HSA? – Any hope for observations of molecular absorption systems?

Is there an irreducible noise floor?– How low can we go?– Can we have certainty when observing weak lines?

Discussion Questions: Low FrequencyIs 800 MHz feasible?

– OH (megamasers, conjugate lines, absorption) at z~1 – HI absorption (intrinsic, gravitational lenses, damped Ly systems)– Changing physical constants, peak of star formation, merging, BH growth– Interferometer with GBT, possibly WSRT

Are polarization observations possible with double position switching?

– B fields in single clouds at high z via OH conjugate lines, absorption

Is there an irreducible noise floor in L-band or below?– (How low can we go?)